ORIGINAL STUDY
Surveillance of Antimicrobial Susceptibilities of Neisseria gonorrhoeae in Nanning, China, 2000 to 2012 Bang-yong Zhu, BD,* Rui-xing Yu, MD,Þ Yueping Yin, PhD,Þ Xiangsheng Chen, PhD,Þ Wei Li, BD,* Xiu-qin Dai, BD,Þ Ming Liang, BD,þ Quan Gan, BD,* Yan-jie Huang, BD,* and Jiang-ping Wei, BD* Objectives: To monitor the frequency of antibiotic resistance of Neisseria gonorrhoeae (NG) in Nanning, China, between 2000 and 2012.
Methods: The production of A-lactamase by NG isolates was determined using the paper acidometric testing method. Antimicrobial susceptibility testing was performed for tetracycline, ciprofloxacin, spectinomycin, and ceftriaxone using the agar dilution method. The W2 test, t test, and univariate and multivariate analyses were used to analyze the statistical difference of the results. Results: A total of 923 NG isolates were collected in Nanning between 2000 and 2012. Among these, 131 (14.2%) were penicillinase-producing NG, 520 (56.3%) isolates were tetracycline-resistant NG, and 857 (92.9%) isolates were ciprofloxacin-resistant strains. One spectinomycin-resistant strain was identified in 2000. There were 304 (32.9%) isolates with decreased susceptibility to ceftriaxone; the proportion of such isolates increased from 22.8% in 2000 to 2002 to 48.9% in 2006 to 2008 (P G 0.001), followed by a fall to 32.2% in 2009 to 2012 (P = 0.001). Patients’ age of 16 to 25 years and isolate collection period of 2008 to 2012 (except 2011) were demonstrated to be risk factors for infection with isolates with decreased susceptibility to ceftriaxone. Conclusions: Antimicrobial susceptibility of NG isolates obtained from patients in Nanning from 2000 to 2012 was characterized by high occurrence of penicillinase-producing NG, tetracycline-resistant NG, and ciprofloxacinresistant strains. Spectinomycin and ceftriaxone can be considered drugs of choice for empirical treatment of NG infection in Nanning. Moreover, we recommend a combination of 500 mg or higher dose of intramuscular ceftriaxone and 1 g oral azithromycin be used for the treatment of NG infection in Nanning and possibly in China.
N
eisseria gonorrhoeae (NG ) is a sexually transmitted pathogen. There are about 106 million new NG infections every year worldwide.1 N. gonorrhoeae infection is associated with urethritis, epididymitis, endometritis, and salpingitis and increases the risk of HIV infection.2 Because of a lack of vaccine for NG infection, effective antimicrobial agents such as the ceftriaxone, which was the first-line drug worldwide, are
From the *Institute of Dermatology, Guangxi Autonomous Region, Nanning, China; †Reference STD Lab, National Center for STD Control, Chinese CDC, and Institute of Dermatology, Chinese Academy of Medical Sciences and Peking Union Medical College, and Jiangsu Key Laboratory of Molecular Biology for Skin Diseases and STIs, Nanjing, Jiangsu Province, China; and ‡The First Affiliated Hospital of Guangxi Medical University, Institute of Dermatology, Nanning, China
Bang-yong Zhu and Rui-xing Yu contributed equally to this study. Conflicts of interest and source of funding: None declared. Correspondence: Yueping Yin, PhD, National Center for STD Control, 12 Jiangwangmiao St, Nanjing 210042, China. E-mail: [email protected]. Received for publication February 28, 2014, and accepted May 22, 2014. DOI: 10.1097/OLQ.0000000000000157 Copyright * 2014 American Sexually Transmitted Diseases Association All rights reserved.
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needed for treatments. However, NG has become resistant to penicillin, tetracycline, and quinolones in the past 3 decades.3Y5 Moreover, in 2012, the NG strains F89 and H041 were found to be resistant to ceftriaxone, the most effective antimicrobial recommended first-line treatment for NG infection.6,7 In China, NG may develop antimicrobial resistance more rapidly than in other countries because the misuse or overuse of antimicroxbials is more frequent in China. Therefore, it is important to track the antimicrobial susceptibility of NG in China, especially in undeveloped areas such as Nanning, the capital of Guangxi Province. The aims of the this study were to analyze the trends of NG susceptibilities to ciprofloxacin, spectinomycin, and ceftriaxone from 2000 to 2012 in Nanning; to assess the percentages of plasmid-mediated penicillinase-producing NG (PPNG) and plasmid-mediated high-level resistance tetracycline-resistant NG (TRNG); and to identify factors associated with infection with NG isolates with decreased susceptibility to ceftriaxone.
TEST METHODS Bacterial Strains A total of 923 NG isolates were consecutively collected by clinicians from patients with uncomplicated gonorrhea attending the sexually transmitted disease clinic affiliated with the Guangxi Provincial Institute of Dermatology in Nanning, China, between 2000 and 2012. Of these, 94.6% were isolated from male patients with urethritis and the rest were recovered from female patients. The mean age of the patients was 33.3 years (range, 16Y67 years). Urethral or cervical swab specimens collected from the patients were inoculated onto Thayer-Martin medium and cultured in candle jars at 36-C for 24 to 48 hours. All isolates were identified on the basis of gram-stained smears, colony morphology, and a positive oxidase reaction. Sugar fermentation test was performed as needed for confirmation. N. gonorrhoeae isolates that met the selection criteria were selected and subcultured onto GC agar base (Difco, Detroit, MI) containing 10% defibrinated sheep blood, and the resulting colonies were swabbed, suspended in skimmed milk, and stored at j70-C before used for antimicrobial susceptibility testing.
Antimicrobial Susceptibility Testing
The production of A-lactamase, a bacterial enzyme that confers resistance to A-lactam antibiotics, by NG isolates, was determined by paper acidometric testing method, as previously described.8 Antimicrobial susceptibility testing was performed for tetracycline, ciprofloxacin, spectinomycin, and ceftriaxone using the agar dilution method.8 Concentrations of antibiotics used were as follows: ciprofloxacin, 0.016 to 16 mg/L; spectinomycin, 2 to 128 mg/L; ceftriaxone, 0.002 to 0.5 mg/L; tetracycline, 8 to 16 mg/L (only used to screen strains with high-level resistance
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to tetracycline according to the World Health Organization (WHO) Western Pacific Region Resistance Surveillance Programme). International NG reference strains ATCC49266 and WHO reference strains G (TRNG), J (PPNG), and L (ceftriaxone-decreased and high-level ciprofloxacin resistant strain) were used as controls in each assay.9 Antimicrobial susceptibilities were determined according to the criteria set by the WHO Western Pacific Region Resistance Surveillance Programme guidelines. Isolates with minimum inhibitory concentrations (MICs) of at least 1.0 mg/L to ciprofloxacin or at least 128 mg/L to spectinomycin were classified as resistant; those with MICs of 0.06 to 0.50 mg/L to ciprofloxacin or at least 0.125 mg/L to ceftriaxone were classified as decreased susceptible; and those with MICs of at least Q16 mg/L to tetracycline were classified as TRNG, although greater than 2 mg/L is also considered resistant.
Statistical Analysis According to the time of their isolation, NG isolates were divided into 4 groups: 2000 to 2002, 2003 to 2005, 2006 to 2008, and 2009 to 2012. The W2 test was used to compare proportions of isolates with decreased susceptibility to ceftriaxone over time, and the t test was performed to compare the geometric mean MIC of ceftriaxone among the groups. The variables used in univariate and multivariate analyses included age, sex, marital status, clinical course, history of gonorrhea, PPNG, TRNG, and the year of isolation between 2007 and 2012. Univariate and multivariate analyses of odds ratio were performed to identify variables associated with infection with isolates with decreased susceptibility to ceftriaxone. Crude odds ratios and 95% confidence intervals (CIs) were calculated according to univariate analysis, and Pearson W2 test was conducted to determine whether these odds ratios differed significantly from 1. Fisher exact test was used to calculate the odds ratio, 95% CI, and P value for variables with 5 or fewer values. To control other variables, only variables with P values of 0.05 or less in Pearson and Fisher exact tests were included in multivariate logistic regression analysis to model the odds of decreased susceptibility. A stepwise approach was used in the multivariate analysis, with the most significant association from univariate analysis added to the model first. Likelihood ratio tests were used to assess whether added variables accounted for the variations seen in the model. All descriptive and statistical analyses were performed with SPSS 20.0 (IBM, Chicago, IL), and graphs were created using Excel 2010 (Microsoft, New York, NY).
to 2012; its MIC90 remained at levels of at least 16 mg/L in 2000 to 2012. All isolates obtained in 2000 to 2009 were susceptible to spectinomycin, with the exception of one resistant strain identified in 2000. The MIC50 of spectinomycin remained at 16 mg/L in 2000 to 2012; however, its MIC90 increased from 32 mg/L in 2000 to 2002 to 64 mg/L in 2009 to 2012 (Table 1).
NG Susceptibility to Ceftriaxone As shown in Table 1, a total of 304 NG isolates with decreased susceptibility to ceftriaxone were identified, and the percentage of such isolates increased from 22.8% in 2000 to 2002 to 48.9% in 2006 to 2008 (P G 0.001), followed by a fall to 32.2% in 2009 to 2012 (P = 0.001). The MIC90 of ceftriaxone remained at 0.25 mg/L from 2000 to 2010, whereas its MIC50 rose from 0.032 mg/L in 2000 to 2002 to 0.064 mg/L in 2003 to 2005 and then kept unchanged in later years (Table 1). The peak MIC50 values in 2000 to 2002, 2003 to 2005, 2006 to 2008, and 2009 to 2012 were 0.032, 0.064, 0.125, and 0.064 mg/L, respectively, and most of the isolates had an MIC of at least 0.032 mg/L. The geometric mean MIC of ceftriaxone remained stable from 2000 to 2002 to 2003 to 2005 (0.0350 mg/L vs. 0.0363 mg/L, P = 0.741), and then rose to 0.0686 mg/L in 2006 to 2008 (P G 0.001) but declined to 0.0466 mg/L in 2009 to 2012 (P = 0.003), which, however, was still higher than those in 2000 to 2002 (0.0466 mg/L vs. 0.0350 mg/L, P = 0.024) and 2003 to 2005 (0.0466 mg/L vs. 0.0363 mg/L, P = 0.048).
Factors Associated With Infection With NG Isolates With Decreased Susceptibility to Ceftriaxone In the univariate analysis (Table 2), decreased susceptibility of NG isolates to ceftriaxone was associated with patients’ age of 16 to 25 years and isolate collection year between 2008 and 2012 (except 2011). In the multivariate analysis, infection age of 16 to 25 years (odds ratio, 2.589; 95% CI, 1.173Y5.703; P = 0.019) and the year of isolation (2008: odds ratio, 3.679 [95% CI, 1.450Y9.335; P = 0.006]; 2009: odds ratio, 12.259 [95% CI, 4.889Y30.743; P G 0.001]; 2010: odds ratio, 4.768 [95% CI, 1.637Y13.886; P = 0.004]; 2012: odds radio, 7.173 [95% CI, 2.390Y21.524; P G 0.001]) were significantly associated with infection with NG isolates with decreased susceptibility to ceftriaxone. The age 26 years or higher, sex, marital status, clinical course, history of gonorrhea, PPNG, TRNG, and isolation year of 2011 were not associated with decreased susceptibility to ceftriaxone in the univariate analysis and thus were not included in the multivariate analysis model.
RESULTS The Percentages of PPNG and TRNG, and NG Susceptibilities to Ciprofloxacin and Spectinomycin Of all 923 NG isolates recovered in 2000 to 2012, 131 were PPNG, whose percentage increased from 5.6% in 2000 to 2002 to 31.8% in 2009 to 2012 (P G 0.001). Five hundred twenty isolates were TRNG, whose percentage rose from 48.7% in 2000 to 2002 to 63.1% in 2006 to 2008 (P = 0.025), and then slightly fall in 2009 to 2012 (P = 0.635). Eight hundred fiftyseven isolates were ciprofloxacin resistant, the percentage of such isolates was steady from 2000 to 2002 to 2003 to 2005 (P = 0.529) but rose from 88.2% in 2003 to 2005 to 98.3% in 2006 to 2008 (P G 0.001), and then kept stable till 2009 to 2012 (P = 0.854). The MIC50 of ciprofloxacin remained at 4 mg/L in both 2000 to 2002 and 2003 to 2005, then increased to 8 mg/L in 2006 to 2008 and further to levels of at least 16 mg/L in 2009
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DISCUSSION The 923 NG isolates recovered in 2000 to 2012 were tested for their production of penicillinase as well as their susceptibility to tetracycline, ciprofloxacin, spectinomycin, and ceftriaxone (Table 1). Specifically, the percentages of PPNG in Nanning were considerably lower than those reported in both Thailand (80.8%Y86.0% in 2007Y2010, except 2009)10,11 and Laos (55.0%Y90.0% in 2001Y2005),12Y16 and in general lower than those in Vietnam (28.6%Y47.1% in 2000Y2008, except 2003)10,12,13,15Y18, but the percentage of PPNG in 2009 to 2012 in Nanning was consistent with that reported in Vietnam in 2010 (31.4%).11 The percentages of TRNG in Nanning were lower than those reported in Laos (98.9% and 96.9% in 2001 and 2002, respectively),12,13 but higher than those in Vietnam (9.9%Y42.7% in 2000Y2006, except 2003).12,13,15Y18 The prevalence of TRNG in Nanning increased with time in 2000
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TABLE 1.
Percentages of PPNG and TRNG and NG Susceptibilities to Ciprofloxacin, Spectinomycin, and Ceftriaxone Among 923 NG Isolates Tested in Nanning, China
Year
2000Y2002
2003Y2005
2006Y2008
2009Y2012
Total
PPNG (%)* TRNG (%)† Ciprofloxacin‡ Susceptible (%) Decreased (%) Resistant (%) MIC50 (mg/L) MIC90 (mg/L) MIC range (mg/L) Spectinomycin§ Susceptible (%) Decreased (%) Resistant (%) MIC50 (mg/L) MIC90 (mg/L) MIC range (mg/L) Ceftriaxone¶ Susceptible (%) Decreased (%) Resistant (%) MIC50 (mg/L) MIC90 (mg/L) MIC range (mg/L) Total
15 (5.6%) 130 (48.7%)
36 (13.3%) 158 (58.3%)
32 (13.7%) 147 (63.1%)
48 (31.8%) 85 (55.9%)
131 (14.2%) 520 (56.3%)
2 (0.7%) 25 (9.4%) 240 (89.9%) 4 Q16 0.032YQ16
1 (0.4%) 31 (11.4%) 239 (88.2%) 4 Q16 0.032YQ16
0 4 (1.7%) 229 (98.3%) 8 Q16 0.064YQ16
0 3 (2.0%) 149 (98.0%) Q16 Q16 0.125YQ16
3 (0.3%) 63 (6.8%) 857 (92.9%) V V V
266 (99.6%) 0 1 (0.4%) 16 32 2YQ128
271 (100%) 0 0 16 32 2Y64
233 (100%) 0 0 16 64 4Y64
152 (100%) 0 0 16 64 4Y64
922 (99.9%) 0 1 (0.1%) V V V
206 (77.2%) 61 (22.8%) 0 0.032 0.25 e0.002Y0.25 267
191 (70.5%) 80 (29.5%) 0 0.064 0.25 e0.002Y0.25 271
119 (51.1%) 114 (48.9%) 0 0.064 0.25 e0.002Y0.25 233
103 (67.8%) 49 (32.2%) 0 0.064 0.25 0.004Y0.25 152
619 (67.1%) 304 (32.9%) 0 V V V 923
* PPNG: plasmid-mediated PPNG. † TRNG: isolates with MICs of at least ‡
16 mg/L to tetracycline were classified as plasmid-mediated high-level resistance TRNG. Susceptible: isolates with MICs less than 0.06 mg/L; Decreased: isolates with MICs of 0.06 to 0.50 mg/L; Resistant: isolates with MICs of at least 1.0 mg/L. § Susceptible: isolates with MICs of 64 mg/L or less; Resistant: isolates with MICs of at least 128 mg/L. ¶ Susceptible: isolates with MICs of 0.06 mg/L or less; Decreased: isolates with MICs of at least 0.125 mg/L.
to 2008, which was different from that in Vietnam from 2000 to 2006.12,13,15Y18 Moreover, the percentages of ciprofloxacinresistant NG isolates in Nanning was much higher than those reported in Thailand (66.9%Y77.0% in 2007Y2010),10,11,19 Laos (22.5%, 74.1%, 88.0%, and 33.0% in 2001, 2002, 2004, and 2007, respectively),10,12,13,15 and Vietnam before 2008 (44.5%Y58.9% in 2000Y2007, except 2003),10,12,13,15Y18 but were consistent with those in Vietnam in 2008 to 2010 (96.0%Y96.5%).10,11,19 In China, the recommended treatment of choice for uncomplicated NG infections was penicillin in 1989, which was changed to ciprofloxacin in 1995 and then to ceftriaxone or spectinomycin in 2000. The present study showed high percentages of PPNG, TRNG, and ciprofloxacin-resistant strains among NG isolates from Nanning, which supports the belief that penicillin, tetracycline, and ciprofloxacin should not be used for the treatment of gonorrhea. It also demonstrates that NG still developed increasing resistance to the 3 antibiotics in 2000 to 2012, during which they were not used for the treatment of NG infection, suggesting that the developed resistance in NG isolates may result from using them to treat other infections. Spectinomycin resistance has been rare; however, after being used widely for 3 years in the mid-1980s, clinical treatment failures caused by spectinomycin resistance began to appear in US military personnel in the Republic of Korea.20 In the current study, only one spectinomycin-resistant strain was identified in 2000, which was in line with that reported in the WHO Western Pacific and South East Asian regions.10Y19 The percentage of spectinomycin-resistant NG isolates was below 5% (0Y1%), and its MIC50 kept stable from 2000 to 2012 in Nanning, indicating that it remains an effective therapy and can Sexually Transmitted Diseases
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be used as the primary treatment of NG infection. However, spectinomycin has some limitations for the treatment of NG infection. First, spectinomycin-resistant NG strains have been detected in Bangladesh,21 Greece,22 and Russia,23 as well as Nanjing8 and Shanghai24 of China. Second, it is only effective for urethral and rectal infections25 but not for pharyngeal infections, which are asymptomatic but increasingly common,26 particularly in men who have sex with men. Third, high-level spectinomycin resistance has emerged quickly when it was used in the past because of a single mutation in the bacterial genome.25 Lastly, this drug is costly and has to be administered intramuscularly. Therefore, we recommend that spectinomycin be used for NG urethral and/or rectal infections in patients who are allergic to cephalosporins. Ceftriaxone is recommended for treating NG infections at all anatomical sites and preferable to other cephalosporins because of its long serum half-life and relatively infrequent and mild side effects.27 Based on the information from other international guidelines, China has recommended using a single dose of 250 mg ceftriaxone administered intramuscularly as first-line treatment for NG infection since 2007; the current study suggests that there is no immediate threat to its efficacy in treating NG infection in Nanning. However, using ceftriaxone for gonorrhea treatment will be a challenge in the future because of the following factors. First, treatment failures with ceftriaxone have been reported in Japan, France, and Spain.7,28,29 Second, in the current study, the percentage of NG isolates with decreased susceptibility to ceftriaxone, as well as the peak and geometric mean of its MIC, increased from 2000Y2002 to 2006Y2008. Third, our finding that 304 (32.9%) isolates had the MIC of ceftriaxone of at least 0.125 mg/L in
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TABLE 2. Univariate and Multivariate Analyses of Risk Factors for Decreased Susceptibility to Ceftriaxone (MIC Q0.125 mg/L) Among NG Isolates Collected From 2007 to 2012 in Nanning, China Univariate Analysis *
P
58 65 57 44 43 30
21 37 25 19 18 10
0.023 0.403 0.475 0.564 0.789 Reference
2.328 1.376 1.339 1.269 0.881
20 277
7 123
Reference 0.415
108 189
49 81
61 135 68 33
P
Odds Ratios (95% CI)
0.019 V V V V V
2.589 (1.173Y5.703) V V V V V
1.000 1.483 (0.574Y3.831)
V V
V V
Reference 0.675
1.00 1.107 (0.688Y1.782)
V V
V V
25 29 61 15
Reference 0.676 0.978 0.790
1.00 0.833 (0.355Y1.958) 0.989 (0.461Y2.125) 0.892 (0.386Y2.061)
V V V V
V V V V
102 195
44 86
Reference 0.873
1.000 1.040 (0.642Y1.686)
V V
V V
63 234
27 103
Reference 0.869
1.048 (0.598Y1.839)
V V
V V
125 172
49 81
Reference 0.176
0.724 (0.454Y1.156)
V V
V V
56 33 68 31 32 77
9 9 28 14 17 53
Reference 0.003 G0.001 0.04 0.208 G0.001
V 0.006 G0.001 0.004 V G0.001
V 3.679 (1.450Y9.335) 12.259 (4.889Y30.743) 4.768 (1.637Y13.886) V 7.173 (2.390Y21.524)
Total Isolates (N) Age, y 16Y25 26Y30 31Y35 36Y40 41Y49 Q50 Sex Male Female Marital status Single Married Clinical course, d 1Y2 3Y4 5Y6 Q7 Previous gonorrhea No Yes PPNG Yes No TRNG Yes No Year of isolation 2007 2008 2009 2010 2011 2012
Multivariate Analysis
n
Odds Ratios (95% CI)
3.656 11.532 4.301 1.958 5.919
(1.126-4.814)† (0.651Y2.910) (0.601Y2.848) (0.565Y2.848) (0.348Y2.230) 1.000
1.000 (1.545Y8.650)† (4.876Y27.277)† (1.575Y11.743)† (0.688Y5.577) (2.188Y16.013)†
Decreased susceptibility was defined as an MIC of at least 0.125 mg/L. * n means the number of isolates with decreased susceptibility to ceftriaxone. † P G 0.05 means the variables were statistical significant using univariate analysis and were included in multivariate analysis.
Nanning suggests that a higher dose (Q500 mg) may be more suitable for the treatment of NG infection.30 In addition, coadministration of it with 1 g of oral azithromycin was advocated to treat all concomitant chlamydia infections and gonorrhea, which may be able to control rapid emergence of resistance and prevent NG infection outbreak.31 Although NG has showed decreased susceptibility to ceftriaxone, no other effective antimicrobial drugs are available to replace it. Data from meta-analysis refute the suggestion that gentamicin is a promising alternative because this agent has failed to meet the target of greater than 95% treatment success.32 A new potential agent, solithromycin, is being investigated in a phase II clinical trial.33 The levels of MIC50 and MIC90 of ceftriaxone in this study were higher than those reported in Nanjing8 and Shanghai24 of China, Bangladesh,21 Korea,34 and United States.35 Factors such as self-medication in China, possibly due to insufficient control of antimicrobial sale and lack of medical care during treatment, may have contributed to the development of resistance to the antibiotics. In the present study, infection with NG isolates with decreased susceptibility to ceftriaxone was shown to be strongly associated with patients’ age of 16 to
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25 years, suggesting that isolates with decreased susceptibility to ceftriaxone are probably circulating in young people. Moreover, the isolation period of 2008 to 2012, except 2011, was also demonstrated to be associated with infection with NG isolates with decreased susceptibility to ceftriaxone. The exception of 2011 for the association might not be significant because of a small number of isolates collected in this year. Up to now, few studies have identified these variables as risk factors for decreased susceptibility to ceftriaxone. This study has some limitations as follows: (1) isolates with decreased susceptibility to ceftriaxone were not tested by molecular methods for subtyping, which may better understand the mechanism of NG resistant to ceftriaxone, the relationship between special molecular type and antimicrobial resistance, and the relationship between demographic information and antimicrobial resistance; (2) all tested NG isolates were collected from patients attending a sexually transmitted disease clinic affiliated with Guangxi Provincial Institute of Dermatology, which might have a higher prevalence of NG antibiotic resistance than the general population; (3) the small number (approximately 30) of the isolates collected from 2009 to 2011 might limit the statistical power and affect the reliability of relevant results of this
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study; (4) to clearly observe the trends of NG antimicrobial susceptibilities in Nanning from 2000 to 2012, we divided all isolates collected during this period into 4 groups (2000Y2002, 2003Y2005, 2006Y2008, and 2009Y2012), which might limit the availability of detailed information on NG isolates to readers; and (5) the geometric mean t test might be an imperfect measure because a bimodal distribution was observed in later years.
CONCLUSIONS Successful antibiotic treatment plays a critical role in controlling NG infection. Therefore, many initiatives have been directed at promoting and sustaining national and international gonococcal antimicrobial susceptibility surveillance as a key measure to promptly inform the public and update guidelines for NG infection treatment. Our results underscore the requirement for periodic review of national and regional treatment guidelines based on up-to-date antimicrobial resistance data for NG. In this study, antimicrobial susceptibility of NG isolated in Nanning from 2000 to 2012 was characterized by high percentages of PPNG, TRNG, and ciprofloxacin-resistant strains, although none of penicillin, tetracycline, and ciprofloxacin is currently being used as first-line therapy for NG infection. Results of the present study implicate that spectinomycin and ceftriaxone should be considered the drugs of choice for empirical treatment of NG infection in Nanning. Moreover, we recommend using a combination of 500 mg or higher intramuscular ceftriaxone and 1 g oral azithromycin for the treatment of NG infection in Nanning and possibly in China. REFERENCES 1. World Health Organization. Global incidence and prevalence of selected curable sexually transmitted infections 2008 [World Health Organization web site] 2008. Available at: http://www.who.int/ reproductivehealth/publications/rtis/2008_STI_estimates.pdf. Accessed May 9, 2013. 2. Bernstein KT, Marcus JL, Nieri G, et al. Rectal gonorrhea and chlamydia reinfection is associated with increased risk of HIV seroconversion. J Acquir Immune Defic Syndr 2010; 53:537Y543. 3. Barry PM, Klausner JD. The use of cephalosporins for gonorrhea: The impending problem of resistance. Expert Opin Pharmacother 2009; 10:555Y577. 4. Deguchi T, Yasuda M, Maeda S. Lack of nationwide surveillance of antimicrobial resistance of Neisseria gonorrhoeae in Japan. Ann Intern Med 2008; 149:363Y364. 5. Tapsall JW, Ndowa F, Lewis DA, et al. Meeting the public health challenge of multidrug- and extensively drug-resistant Neisseria gonorrhoeae. Expert Rev Anti Infect Ther 2009; 7:821Y834. 6. Goire N, Lahra MM, Ohnishi M, et al. Polymerase chain reactionbased screening for the ceftriaxone-resistant Neisseria gonorrhoeae F89 strain. Euro Surveill 2013; 18:20444. 7. Unemo M, Golparian D, Nicholas R, et al. High-level cefixime- and ceftriaxone-resistant Neisseria gonorrhoeae in France: Novel penA mosaic allele in a successful international clone causes treatment failure. Antimicrob Agents Chemother 2012; 56:1273Y1280. 8. Su X, Jiang F, Qimuge, et al. Surveillance of antimicrobial susceptibilities in Neisseria gonorrhoeae in Nanjing, China, 1999Y2006. Sex Transm Dis 2007; 34:995Y999. 9. Unemo M, Fasth O, Fredlund H, et al. Phenotypic and genetic characterization of the 2008 WHO Neisseria gonorrhoeae reference strain panel intended for global quality assurance and quality control of gonococcal antimicrobial resistance surveillance for public health purposes. J Antimicrob Chemother 2009; 63:1142Y1151. 10. Tapsall JW, Limnios EA, Abu BH, et al. Surveillance of antibiotic resistance in Neisseria gonorrhoeae in the WHO Western Pacific and South East Asian regions, 2007Y2008. Commun Dis Intell Q Rep 2010; 34:1Y7.
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11. Lahra MM. WHO Western Pacific and South East Asian Gonococcal Antimicrobial Surveillance Programme. Surveillance of antibiotic resistance in Neisseria gonorrhoeae in the WHO Western Pacific and South East Asian Regions, 2010. Commun Dis Intell Q Rep 2012; 36:95Y100. 12. Surveillance of antibiotic resistance in Neisseria gonorrhoeae in the WHO Western Pacific Region, 2001. World Health Organization. Commun Dis Intell Q Rep 2002; 26:541Y545. 13. Surveillance of antibiotic resistance in Neisseria gonorrhoeae in the WHO Western Pacific Region, 2002. Commun Dis Intell Q Rep 2003; 27:488Y491. 14. Surveillance of antibiotic resistance in Neisseria gonorrhoeae in the World Health Organization Western Pacific Region, 2003. Commun Dis Intell Q Rep 2005;29:62Y64. 15. Surveillance of antibiotic resistance in Neisseria gonorrhoeae in the WHO Western Pacific Region, 2004. Commun Dis Intell Q Rep 2006;30:129Y132. 16. Surveillance of antibiotic resistance in Neisseria gonorrhoeae in the WHO Western Pacific Region, 2005. Commun Dis Intell Q Rep 2006; 30:430Y433. 17. Surveillance of antibiotic resistance in Neisseria gonorrhoeae in the WHO Western Pacific Region, 2000. Commun Dis Intell Q Rep 2001; 25:274Y276. 18. Surveillance of antibiotic resistance in Neisseria gonorrhoeae in the WHO Western Pacific Region, 2006. Commun Dis Intell Q Rep 2008; 32:48Y51. 19. Surveillance of antibiotic resistance in Neisseria gonorrhoeae in the WHO Western Pacific and South East Asian Regions, 2009. Commun Dis Intell Q Rep 2011; 35:2Y7. 20. Boslego JW, Tramont EC, Takafuji ET, et al. Effect of spectinomycin use on the prevalence of spectinomycin-resistant and of penicillinase-producing Neisseria gonorrhoeae. N Engl J Med 1987; 317:272Y278. 21. Ahmed MU, Chawdhury FA, Hossain M, et al. Monitoring antimicrobial susceptibility of Neisseria gonorrhoeae isolated from Bangladesh during 1997Y2006: Emergence and pattern of drug-resistant isolates. J Health Popul Nutr 2010; 28:443Y449. 22. Stathi M, Flemetakis A, Miriagou V, et al. Antimicrobial susceptibility of Neisseria gonorrhoeae in Greece: Data for the years 1994Y2004. J Antimicrob Chemother 2006; 57:775Y779. 23. Kubanova A, Frigo N, Kubanov A, et al. The Russian gonococcal antimicrobial susceptibility programme (RU-GASP)VNational resistance prevalence in 2007 and 2008, and trends during 2005Y2008. Euro Surveill 2010; 15:1Y5. 24. Yang Y, Liao M, Gu WM, et al. Antimicrobial susceptibility and molecular determinants of quinolone resistance in Neisseria gonorrhoeae isolates from Shanghai. J Antimicrob Chemother 2006; 58:868Y872. 25. Ferreira WA, Ferreira CM, Naveca FG, et al. Genotyping of two Neisseria gonorrhoeae fluroquinolone resistant strains in the Brazilian Amazon region. Mem Inst Oswaldo Cruz 2011; 106:629Y631. 26. Gail AB, Sparling PF, Wasserheit JN. The emerging threat of untreatable gonococcal infection. N Engl J Med 2012; 366:485Y487. 27. Hanc¸ali A1, Ndowa F, Bellaji B, et al. Antimicrobial resistance monitoring in Neisseria gonorrhoeae and strategic use of funds from the Global Fund to set up a systematic Moroccan gonococcal antimicrobial surveillance programme. Sex Transm Infect 2013; 89(Suppl4):iv24Yiv27. 28. Ohnishi M, Golparian D, Shimuta K, et al. Is Neisseria gonorrhoeae initiating a future era of untreatable gonorrhea? Detailed characterization of the first strain with high-level resistance to ceftriaxone. Antimicrob Agents Chemother 2011; 55: 3538Y3545. 29. Camara J, Serra J, Ayats J, et al. Molecular characterization of two high-level ceftriaxone-resistant Neisseria gonorrhoeae isolates detected in Catalonia, Spain. J Antimicrob Chemother 2012; 67: 1858Y1860. 30. Ison CA, Town K, Obi C, et al. GRASP collaborative group. Decreased susceptibility to cephalosporins among gonococci: data from the gonococcal resistance to Antimicrobials Surveillance Programme (GRASP) in England and Wales, 2007Y2011. Lancet Infect Dis 2013; 13:762Y768.
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31. Bala M, Kakran M, Singh V, et al. Monitoring antimicrobial resistance in Neisseria gonorrhoeae in selected countries of the WHO South-East Asia Region between 2009 and 2012: A retrospective analysis. Sex Transm Infect 2013; 89(Suppl 4):iv28Yiv35. 32. Dowell D, Kirkcaldy RD. Effectiveness of gentamicin for gonorrhoea treatment: Systematic review and meta-analysis. Postgrad Med J 2013; 89:142Y147. 33. Golparian D, Fernandes P, Ohnishi M, et al. In vitro activity of the new fluoroketolide solithromycin (CEM-10) against a large collection of clinical Neisseria gonorrhoeae isolates and international reference
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strains including high-level antimicrobial resistance: Potential treatment option for gonorrhoea?. Antimicrob Agents Chemother 2012; 56:2739Y2742. 34. Lee H, Hong SG, Soe Y, et al. Trends in antimicrobial resistance of Neisseria gonorrhoeae isolated from Korean patients from 2000 to 2006. Sex Transm Dis 2011; 38:1082Y1086. 35. Cephalosporin susceptibility among Neisseria gonorrhoeae isolatesV United States, 2000Y2010 [J]. MMWR Morb Mortal Wkly Rep 2011; 60:873Y877.
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Surveillance of Antimicrobial Susceptibilities of Neisseria gonorrhoeae in Nanning, China, 2000 to 2012 Bang-yong Zhu, BD,* Rui-xing Yu, MD,Þ Yueping Yin, PhD,Þ Xiangsheng Chen, PhD,Þ Wei Li, BD,* Xiu-qin Dai, BD,Þ Ming Liang, BD,þ Quan Gan, BD,* Yan-jie Huang, BD,* and Jiang-ping Wei, BD* Objectives: To monitor the frequency of antibiotic resistance of Neisseria gonorrhoeae (NG) in Nanning, China, between 2000 and 2012.
Methods: The production of A-lactamase by NG isolates was determined using the paper acidometric testing method. Antimicrobial susceptibility testing was performed for tetracycline, ciprofloxacin, spectinomycin, and ceftriaxone using the agar dilution method. The W2 test, t test, and univariate and multivariate analyses were used to analyze the statistical difference of the results. Results: A total of 923 NG isolates were collected in Nanning between 2000 and 2012. Among these, 131 (14.2%) were penicillinase-producing NG, 520 (56.3%) isolates were tetracycline-resistant NG, and 857 (92.9%) isolates were ciprofloxacin-resistant strains. One spectinomycin-resistant strain was identified in 2000. There were 304 (32.9%) isolates with decreased susceptibility to ceftriaxone; the proportion of such isolates increased from 22.8% in 2000 to 2002 to 48.9% in 2006 to 2008 (P G 0.001), followed by a fall to 32.2% in 2009 to 2012 (P = 0.001). Patients’ age of 16 to 25 years and isolate collection period of 2008 to 2012 (except 2011) were demonstrated to be risk factors for infection with isolates with decreased susceptibility to ceftriaxone. Conclusions: Antimicrobial susceptibility of NG isolates obtained from patients in Nanning from 2000 to 2012 was characterized by high occurrence of penicillinase-producing NG, tetracycline-resistant NG, and ciprofloxacinresistant strains. Spectinomycin and ceftriaxone can be considered drugs of choice for empirical treatment of NG infection in Nanning. Moreover, we recommend a combination of 500 mg or higher dose of intramuscular ceftriaxone and 1 g oral azithromycin be used for the treatment of NG infection in Nanning and possibly in China.
N
eisseria gonorrhoeae (NG ) is a sexually transmitted pathogen. There are about 106 million new NG infections every year worldwide.1 N. gonorrhoeae infection is associated with urethritis, epididymitis, endometritis, and salpingitis and increases the risk of HIV infection.2 Because of a lack of vaccine for NG infection, effective antimicrobial agents such as the ceftriaxone, which was the first-line drug worldwide, are
From the *Institute of Dermatology, Guangxi Autonomous Region, Nanning, China; †Reference STD Lab, National Center for STD Control, Chinese CDC, and Institute of Dermatology, Chinese Academy of Medical Sciences and Peking Union Medical College, and Jiangsu Key Laboratory of Molecular Biology for Skin Diseases and STIs, Nanjing, Jiangsu Province, China; and ‡The First Affiliated Hospital of Guangxi Medical University, Institute of Dermatology, Nanning, China
Bang-yong Zhu and Rui-xing Yu contributed equally to this study. Conflicts of interest and source of funding: None declared. Correspondence: Yueping Yin, PhD, National Center for STD Control, 12 Jiangwangmiao St, Nanjing 210042, China. E-mail: [email protected]. Received for publication February 28, 2014, and accepted May 22, 2014. DOI: 10.1097/OLQ.0000000000000157 Copyright * 2014 American Sexually Transmitted Diseases Association All rights reserved.
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needed for treatments. However, NG has become resistant to penicillin, tetracycline, and quinolones in the past 3 decades.3Y5 Moreover, in 2012, the NG strains F89 and H041 were found to be resistant to ceftriaxone, the most effective antimicrobial recommended first-line treatment for NG infection.6,7 In China, NG may develop antimicrobial resistance more rapidly than in other countries because the misuse or overuse of antimicroxbials is more frequent in China. Therefore, it is important to track the antimicrobial susceptibility of NG in China, especially in undeveloped areas such as Nanning, the capital of Guangxi Province. The aims of the this study were to analyze the trends of NG susceptibilities to ciprofloxacin, spectinomycin, and ceftriaxone from 2000 to 2012 in Nanning; to assess the percentages of plasmid-mediated penicillinase-producing NG (PPNG) and plasmid-mediated high-level resistance tetracycline-resistant NG (TRNG); and to identify factors associated with infection with NG isolates with decreased susceptibility to ceftriaxone.
TEST METHODS Bacterial Strains A total of 923 NG isolates were consecutively collected by clinicians from patients with uncomplicated gonorrhea attending the sexually transmitted disease clinic affiliated with the Guangxi Provincial Institute of Dermatology in Nanning, China, between 2000 and 2012. Of these, 94.6% were isolated from male patients with urethritis and the rest were recovered from female patients. The mean age of the patients was 33.3 years (range, 16Y67 years). Urethral or cervical swab specimens collected from the patients were inoculated onto Thayer-Martin medium and cultured in candle jars at 36-C for 24 to 48 hours. All isolates were identified on the basis of gram-stained smears, colony morphology, and a positive oxidase reaction. Sugar fermentation test was performed as needed for confirmation. N. gonorrhoeae isolates that met the selection criteria were selected and subcultured onto GC agar base (Difco, Detroit, MI) containing 10% defibrinated sheep blood, and the resulting colonies were swabbed, suspended in skimmed milk, and stored at j70-C before used for antimicrobial susceptibility testing.
Antimicrobial Susceptibility Testing
The production of A-lactamase, a bacterial enzyme that confers resistance to A-lactam antibiotics, by NG isolates, was determined by paper acidometric testing method, as previously described.8 Antimicrobial susceptibility testing was performed for tetracycline, ciprofloxacin, spectinomycin, and ceftriaxone using the agar dilution method.8 Concentrations of antibiotics used were as follows: ciprofloxacin, 0.016 to 16 mg/L; spectinomycin, 2 to 128 mg/L; ceftriaxone, 0.002 to 0.5 mg/L; tetracycline, 8 to 16 mg/L (only used to screen strains with high-level resistance
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to tetracycline according to the World Health Organization (WHO) Western Pacific Region Resistance Surveillance Programme). International NG reference strains ATCC49266 and WHO reference strains G (TRNG), J (PPNG), and L (ceftriaxone-decreased and high-level ciprofloxacin resistant strain) were used as controls in each assay.9 Antimicrobial susceptibilities were determined according to the criteria set by the WHO Western Pacific Region Resistance Surveillance Programme guidelines. Isolates with minimum inhibitory concentrations (MICs) of at least 1.0 mg/L to ciprofloxacin or at least 128 mg/L to spectinomycin were classified as resistant; those with MICs of 0.06 to 0.50 mg/L to ciprofloxacin or at least 0.125 mg/L to ceftriaxone were classified as decreased susceptible; and those with MICs of at least Q16 mg/L to tetracycline were classified as TRNG, although greater than 2 mg/L is also considered resistant.
Statistical Analysis According to the time of their isolation, NG isolates were divided into 4 groups: 2000 to 2002, 2003 to 2005, 2006 to 2008, and 2009 to 2012. The W2 test was used to compare proportions of isolates with decreased susceptibility to ceftriaxone over time, and the t test was performed to compare the geometric mean MIC of ceftriaxone among the groups. The variables used in univariate and multivariate analyses included age, sex, marital status, clinical course, history of gonorrhea, PPNG, TRNG, and the year of isolation between 2007 and 2012. Univariate and multivariate analyses of odds ratio were performed to identify variables associated with infection with isolates with decreased susceptibility to ceftriaxone. Crude odds ratios and 95% confidence intervals (CIs) were calculated according to univariate analysis, and Pearson W2 test was conducted to determine whether these odds ratios differed significantly from 1. Fisher exact test was used to calculate the odds ratio, 95% CI, and P value for variables with 5 or fewer values. To control other variables, only variables with P values of 0.05 or less in Pearson and Fisher exact tests were included in multivariate logistic regression analysis to model the odds of decreased susceptibility. A stepwise approach was used in the multivariate analysis, with the most significant association from univariate analysis added to the model first. Likelihood ratio tests were used to assess whether added variables accounted for the variations seen in the model. All descriptive and statistical analyses were performed with SPSS 20.0 (IBM, Chicago, IL), and graphs were created using Excel 2010 (Microsoft, New York, NY).
to 2012; its MIC90 remained at levels of at least 16 mg/L in 2000 to 2012. All isolates obtained in 2000 to 2009 were susceptible to spectinomycin, with the exception of one resistant strain identified in 2000. The MIC50 of spectinomycin remained at 16 mg/L in 2000 to 2012; however, its MIC90 increased from 32 mg/L in 2000 to 2002 to 64 mg/L in 2009 to 2012 (Table 1).
NG Susceptibility to Ceftriaxone As shown in Table 1, a total of 304 NG isolates with decreased susceptibility to ceftriaxone were identified, and the percentage of such isolates increased from 22.8% in 2000 to 2002 to 48.9% in 2006 to 2008 (P G 0.001), followed by a fall to 32.2% in 2009 to 2012 (P = 0.001). The MIC90 of ceftriaxone remained at 0.25 mg/L from 2000 to 2010, whereas its MIC50 rose from 0.032 mg/L in 2000 to 2002 to 0.064 mg/L in 2003 to 2005 and then kept unchanged in later years (Table 1). The peak MIC50 values in 2000 to 2002, 2003 to 2005, 2006 to 2008, and 2009 to 2012 were 0.032, 0.064, 0.125, and 0.064 mg/L, respectively, and most of the isolates had an MIC of at least 0.032 mg/L. The geometric mean MIC of ceftriaxone remained stable from 2000 to 2002 to 2003 to 2005 (0.0350 mg/L vs. 0.0363 mg/L, P = 0.741), and then rose to 0.0686 mg/L in 2006 to 2008 (P G 0.001) but declined to 0.0466 mg/L in 2009 to 2012 (P = 0.003), which, however, was still higher than those in 2000 to 2002 (0.0466 mg/L vs. 0.0350 mg/L, P = 0.024) and 2003 to 2005 (0.0466 mg/L vs. 0.0363 mg/L, P = 0.048).
Factors Associated With Infection With NG Isolates With Decreased Susceptibility to Ceftriaxone In the univariate analysis (Table 2), decreased susceptibility of NG isolates to ceftriaxone was associated with patients’ age of 16 to 25 years and isolate collection year between 2008 and 2012 (except 2011). In the multivariate analysis, infection age of 16 to 25 years (odds ratio, 2.589; 95% CI, 1.173Y5.703; P = 0.019) and the year of isolation (2008: odds ratio, 3.679 [95% CI, 1.450Y9.335; P = 0.006]; 2009: odds ratio, 12.259 [95% CI, 4.889Y30.743; P G 0.001]; 2010: odds ratio, 4.768 [95% CI, 1.637Y13.886; P = 0.004]; 2012: odds radio, 7.173 [95% CI, 2.390Y21.524; P G 0.001]) were significantly associated with infection with NG isolates with decreased susceptibility to ceftriaxone. The age 26 years or higher, sex, marital status, clinical course, history of gonorrhea, PPNG, TRNG, and isolation year of 2011 were not associated with decreased susceptibility to ceftriaxone in the univariate analysis and thus were not included in the multivariate analysis model.
RESULTS The Percentages of PPNG and TRNG, and NG Susceptibilities to Ciprofloxacin and Spectinomycin Of all 923 NG isolates recovered in 2000 to 2012, 131 were PPNG, whose percentage increased from 5.6% in 2000 to 2002 to 31.8% in 2009 to 2012 (P G 0.001). Five hundred twenty isolates were TRNG, whose percentage rose from 48.7% in 2000 to 2002 to 63.1% in 2006 to 2008 (P = 0.025), and then slightly fall in 2009 to 2012 (P = 0.635). Eight hundred fiftyseven isolates were ciprofloxacin resistant, the percentage of such isolates was steady from 2000 to 2002 to 2003 to 2005 (P = 0.529) but rose from 88.2% in 2003 to 2005 to 98.3% in 2006 to 2008 (P G 0.001), and then kept stable till 2009 to 2012 (P = 0.854). The MIC50 of ciprofloxacin remained at 4 mg/L in both 2000 to 2002 and 2003 to 2005, then increased to 8 mg/L in 2006 to 2008 and further to levels of at least 16 mg/L in 2009
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DISCUSSION The 923 NG isolates recovered in 2000 to 2012 were tested for their production of penicillinase as well as their susceptibility to tetracycline, ciprofloxacin, spectinomycin, and ceftriaxone (Table 1). Specifically, the percentages of PPNG in Nanning were considerably lower than those reported in both Thailand (80.8%Y86.0% in 2007Y2010, except 2009)10,11 and Laos (55.0%Y90.0% in 2001Y2005),12Y16 and in general lower than those in Vietnam (28.6%Y47.1% in 2000Y2008, except 2003)10,12,13,15Y18, but the percentage of PPNG in 2009 to 2012 in Nanning was consistent with that reported in Vietnam in 2010 (31.4%).11 The percentages of TRNG in Nanning were lower than those reported in Laos (98.9% and 96.9% in 2001 and 2002, respectively),12,13 but higher than those in Vietnam (9.9%Y42.7% in 2000Y2006, except 2003).12,13,15Y18 The prevalence of TRNG in Nanning increased with time in 2000
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TABLE 1.
Percentages of PPNG and TRNG and NG Susceptibilities to Ciprofloxacin, Spectinomycin, and Ceftriaxone Among 923 NG Isolates Tested in Nanning, China
Year
2000Y2002
2003Y2005
2006Y2008
2009Y2012
Total
PPNG (%)* TRNG (%)† Ciprofloxacin‡ Susceptible (%) Decreased (%) Resistant (%) MIC50 (mg/L) MIC90 (mg/L) MIC range (mg/L) Spectinomycin§ Susceptible (%) Decreased (%) Resistant (%) MIC50 (mg/L) MIC90 (mg/L) MIC range (mg/L) Ceftriaxone¶ Susceptible (%) Decreased (%) Resistant (%) MIC50 (mg/L) MIC90 (mg/L) MIC range (mg/L) Total
15 (5.6%) 130 (48.7%)
36 (13.3%) 158 (58.3%)
32 (13.7%) 147 (63.1%)
48 (31.8%) 85 (55.9%)
131 (14.2%) 520 (56.3%)
2 (0.7%) 25 (9.4%) 240 (89.9%) 4 Q16 0.032YQ16
1 (0.4%) 31 (11.4%) 239 (88.2%) 4 Q16 0.032YQ16
0 4 (1.7%) 229 (98.3%) 8 Q16 0.064YQ16
0 3 (2.0%) 149 (98.0%) Q16 Q16 0.125YQ16
3 (0.3%) 63 (6.8%) 857 (92.9%) V V V
266 (99.6%) 0 1 (0.4%) 16 32 2YQ128
271 (100%) 0 0 16 32 2Y64
233 (100%) 0 0 16 64 4Y64
152 (100%) 0 0 16 64 4Y64
922 (99.9%) 0 1 (0.1%) V V V
206 (77.2%) 61 (22.8%) 0 0.032 0.25 e0.002Y0.25 267
191 (70.5%) 80 (29.5%) 0 0.064 0.25 e0.002Y0.25 271
119 (51.1%) 114 (48.9%) 0 0.064 0.25 e0.002Y0.25 233
103 (67.8%) 49 (32.2%) 0 0.064 0.25 0.004Y0.25 152
619 (67.1%) 304 (32.9%) 0 V V V 923
* PPNG: plasmid-mediated PPNG. † TRNG: isolates with MICs of at least ‡
16 mg/L to tetracycline were classified as plasmid-mediated high-level resistance TRNG. Susceptible: isolates with MICs less than 0.06 mg/L; Decreased: isolates with MICs of 0.06 to 0.50 mg/L; Resistant: isolates with MICs of at least 1.0 mg/L. § Susceptible: isolates with MICs of 64 mg/L or less; Resistant: isolates with MICs of at least 128 mg/L. ¶ Susceptible: isolates with MICs of 0.06 mg/L or less; Decreased: isolates with MICs of at least 0.125 mg/L.
to 2008, which was different from that in Vietnam from 2000 to 2006.12,13,15Y18 Moreover, the percentages of ciprofloxacinresistant NG isolates in Nanning was much higher than those reported in Thailand (66.9%Y77.0% in 2007Y2010),10,11,19 Laos (22.5%, 74.1%, 88.0%, and 33.0% in 2001, 2002, 2004, and 2007, respectively),10,12,13,15 and Vietnam before 2008 (44.5%Y58.9% in 2000Y2007, except 2003),10,12,13,15Y18 but were consistent with those in Vietnam in 2008 to 2010 (96.0%Y96.5%).10,11,19 In China, the recommended treatment of choice for uncomplicated NG infections was penicillin in 1989, which was changed to ciprofloxacin in 1995 and then to ceftriaxone or spectinomycin in 2000. The present study showed high percentages of PPNG, TRNG, and ciprofloxacin-resistant strains among NG isolates from Nanning, which supports the belief that penicillin, tetracycline, and ciprofloxacin should not be used for the treatment of gonorrhea. It also demonstrates that NG still developed increasing resistance to the 3 antibiotics in 2000 to 2012, during which they were not used for the treatment of NG infection, suggesting that the developed resistance in NG isolates may result from using them to treat other infections. Spectinomycin resistance has been rare; however, after being used widely for 3 years in the mid-1980s, clinical treatment failures caused by spectinomycin resistance began to appear in US military personnel in the Republic of Korea.20 In the current study, only one spectinomycin-resistant strain was identified in 2000, which was in line with that reported in the WHO Western Pacific and South East Asian regions.10Y19 The percentage of spectinomycin-resistant NG isolates was below 5% (0Y1%), and its MIC50 kept stable from 2000 to 2012 in Nanning, indicating that it remains an effective therapy and can Sexually Transmitted Diseases
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be used as the primary treatment of NG infection. However, spectinomycin has some limitations for the treatment of NG infection. First, spectinomycin-resistant NG strains have been detected in Bangladesh,21 Greece,22 and Russia,23 as well as Nanjing8 and Shanghai24 of China. Second, it is only effective for urethral and rectal infections25 but not for pharyngeal infections, which are asymptomatic but increasingly common,26 particularly in men who have sex with men. Third, high-level spectinomycin resistance has emerged quickly when it was used in the past because of a single mutation in the bacterial genome.25 Lastly, this drug is costly and has to be administered intramuscularly. Therefore, we recommend that spectinomycin be used for NG urethral and/or rectal infections in patients who are allergic to cephalosporins. Ceftriaxone is recommended for treating NG infections at all anatomical sites and preferable to other cephalosporins because of its long serum half-life and relatively infrequent and mild side effects.27 Based on the information from other international guidelines, China has recommended using a single dose of 250 mg ceftriaxone administered intramuscularly as first-line treatment for NG infection since 2007; the current study suggests that there is no immediate threat to its efficacy in treating NG infection in Nanning. However, using ceftriaxone for gonorrhea treatment will be a challenge in the future because of the following factors. First, treatment failures with ceftriaxone have been reported in Japan, France, and Spain.7,28,29 Second, in the current study, the percentage of NG isolates with decreased susceptibility to ceftriaxone, as well as the peak and geometric mean of its MIC, increased from 2000Y2002 to 2006Y2008. Third, our finding that 304 (32.9%) isolates had the MIC of ceftriaxone of at least 0.125 mg/L in
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TABLE 2. Univariate and Multivariate Analyses of Risk Factors for Decreased Susceptibility to Ceftriaxone (MIC Q0.125 mg/L) Among NG Isolates Collected From 2007 to 2012 in Nanning, China Univariate Analysis *
P
58 65 57 44 43 30
21 37 25 19 18 10
0.023 0.403 0.475 0.564 0.789 Reference
2.328 1.376 1.339 1.269 0.881
20 277
7 123
Reference 0.415
108 189
49 81
61 135 68 33
P
Odds Ratios (95% CI)
0.019 V V V V V
2.589 (1.173Y5.703) V V V V V
1.000 1.483 (0.574Y3.831)
V V
V V
Reference 0.675
1.00 1.107 (0.688Y1.782)
V V
V V
25 29 61 15
Reference 0.676 0.978 0.790
1.00 0.833 (0.355Y1.958) 0.989 (0.461Y2.125) 0.892 (0.386Y2.061)
V V V V
V V V V
102 195
44 86
Reference 0.873
1.000 1.040 (0.642Y1.686)
V V
V V
63 234
27 103
Reference 0.869
1.048 (0.598Y1.839)
V V
V V
125 172
49 81
Reference 0.176
0.724 (0.454Y1.156)
V V
V V
56 33 68 31 32 77
9 9 28 14 17 53
Reference 0.003 G0.001 0.04 0.208 G0.001
V 0.006 G0.001 0.004 V G0.001
V 3.679 (1.450Y9.335) 12.259 (4.889Y30.743) 4.768 (1.637Y13.886) V 7.173 (2.390Y21.524)
Total Isolates (N) Age, y 16Y25 26Y30 31Y35 36Y40 41Y49 Q50 Sex Male Female Marital status Single Married Clinical course, d 1Y2 3Y4 5Y6 Q7 Previous gonorrhea No Yes PPNG Yes No TRNG Yes No Year of isolation 2007 2008 2009 2010 2011 2012
Multivariate Analysis
n
Odds Ratios (95% CI)
3.656 11.532 4.301 1.958 5.919
(1.126-4.814)† (0.651Y2.910) (0.601Y2.848) (0.565Y2.848) (0.348Y2.230) 1.000
1.000 (1.545Y8.650)† (4.876Y27.277)† (1.575Y11.743)† (0.688Y5.577) (2.188Y16.013)†
Decreased susceptibility was defined as an MIC of at least 0.125 mg/L. * n means the number of isolates with decreased susceptibility to ceftriaxone. † P G 0.05 means the variables were statistical significant using univariate analysis and were included in multivariate analysis.
Nanning suggests that a higher dose (Q500 mg) may be more suitable for the treatment of NG infection.30 In addition, coadministration of it with 1 g of oral azithromycin was advocated to treat all concomitant chlamydia infections and gonorrhea, which may be able to control rapid emergence of resistance and prevent NG infection outbreak.31 Although NG has showed decreased susceptibility to ceftriaxone, no other effective antimicrobial drugs are available to replace it. Data from meta-analysis refute the suggestion that gentamicin is a promising alternative because this agent has failed to meet the target of greater than 95% treatment success.32 A new potential agent, solithromycin, is being investigated in a phase II clinical trial.33 The levels of MIC50 and MIC90 of ceftriaxone in this study were higher than those reported in Nanjing8 and Shanghai24 of China, Bangladesh,21 Korea,34 and United States.35 Factors such as self-medication in China, possibly due to insufficient control of antimicrobial sale and lack of medical care during treatment, may have contributed to the development of resistance to the antibiotics. In the present study, infection with NG isolates with decreased susceptibility to ceftriaxone was shown to be strongly associated with patients’ age of 16 to
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25 years, suggesting that isolates with decreased susceptibility to ceftriaxone are probably circulating in young people. Moreover, the isolation period of 2008 to 2012, except 2011, was also demonstrated to be associated with infection with NG isolates with decreased susceptibility to ceftriaxone. The exception of 2011 for the association might not be significant because of a small number of isolates collected in this year. Up to now, few studies have identified these variables as risk factors for decreased susceptibility to ceftriaxone. This study has some limitations as follows: (1) isolates with decreased susceptibility to ceftriaxone were not tested by molecular methods for subtyping, which may better understand the mechanism of NG resistant to ceftriaxone, the relationship between special molecular type and antimicrobial resistance, and the relationship between demographic information and antimicrobial resistance; (2) all tested NG isolates were collected from patients attending a sexually transmitted disease clinic affiliated with Guangxi Provincial Institute of Dermatology, which might have a higher prevalence of NG antibiotic resistance than the general population; (3) the small number (approximately 30) of the isolates collected from 2009 to 2011 might limit the statistical power and affect the reliability of relevant results of this
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Susceptibilities of NG in China
study; (4) to clearly observe the trends of NG antimicrobial susceptibilities in Nanning from 2000 to 2012, we divided all isolates collected during this period into 4 groups (2000Y2002, 2003Y2005, 2006Y2008, and 2009Y2012), which might limit the availability of detailed information on NG isolates to readers; and (5) the geometric mean t test might be an imperfect measure because a bimodal distribution was observed in later years.
CONCLUSIONS Successful antibiotic treatment plays a critical role in controlling NG infection. Therefore, many initiatives have been directed at promoting and sustaining national and international gonococcal antimicrobial susceptibility surveillance as a key measure to promptly inform the public and update guidelines for NG infection treatment. Our results underscore the requirement for periodic review of national and regional treatment guidelines based on up-to-date antimicrobial resistance data for NG. In this study, antimicrobial susceptibility of NG isolated in Nanning from 2000 to 2012 was characterized by high percentages of PPNG, TRNG, and ciprofloxacin-resistant strains, although none of penicillin, tetracycline, and ciprofloxacin is currently being used as first-line therapy for NG infection. Results of the present study implicate that spectinomycin and ceftriaxone should be considered the drugs of choice for empirical treatment of NG infection in Nanning. Moreover, we recommend using a combination of 500 mg or higher intramuscular ceftriaxone and 1 g oral azithromycin for the treatment of NG infection in Nanning and possibly in China. REFERENCES 1. World Health Organization. Global incidence and prevalence of selected curable sexually transmitted infections 2008 [World Health Organization web site] 2008. Available at: http://www.who.int/ reproductivehealth/publications/rtis/2008_STI_estimates.pdf. Accessed May 9, 2013. 2. Bernstein KT, Marcus JL, Nieri G, et al. Rectal gonorrhea and chlamydia reinfection is associated with increased risk of HIV seroconversion. J Acquir Immune Defic Syndr 2010; 53:537Y543. 3. Barry PM, Klausner JD. The use of cephalosporins for gonorrhea: The impending problem of resistance. Expert Opin Pharmacother 2009; 10:555Y577. 4. Deguchi T, Yasuda M, Maeda S. Lack of nationwide surveillance of antimicrobial resistance of Neisseria gonorrhoeae in Japan. Ann Intern Med 2008; 149:363Y364. 5. Tapsall JW, Ndowa F, Lewis DA, et al. Meeting the public health challenge of multidrug- and extensively drug-resistant Neisseria gonorrhoeae. Expert Rev Anti Infect Ther 2009; 7:821Y834. 6. Goire N, Lahra MM, Ohnishi M, et al. Polymerase chain reactionbased screening for the ceftriaxone-resistant Neisseria gonorrhoeae F89 strain. Euro Surveill 2013; 18:20444. 7. Unemo M, Golparian D, Nicholas R, et al. High-level cefixime- and ceftriaxone-resistant Neisseria gonorrhoeae in France: Novel penA mosaic allele in a successful international clone causes treatment failure. Antimicrob Agents Chemother 2012; 56:1273Y1280. 8. Su X, Jiang F, Qimuge, et al. Surveillance of antimicrobial susceptibilities in Neisseria gonorrhoeae in Nanjing, China, 1999Y2006. Sex Transm Dis 2007; 34:995Y999. 9. Unemo M, Fasth O, Fredlund H, et al. Phenotypic and genetic characterization of the 2008 WHO Neisseria gonorrhoeae reference strain panel intended for global quality assurance and quality control of gonococcal antimicrobial resistance surveillance for public health purposes. J Antimicrob Chemother 2009; 63:1142Y1151. 10. Tapsall JW, Limnios EA, Abu BH, et al. Surveillance of antibiotic resistance in Neisseria gonorrhoeae in the WHO Western Pacific and South East Asian regions, 2007Y2008. Commun Dis Intell Q Rep 2010; 34:1Y7.
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