1579 Journal o f Food Protection, Vol. 77, No. 9, 2014, Pages 1579-1582 doi: 10.4315/0362-028X.JFP-14-018 Copyright © , International Association for Food Protection
Research Note
Prevalence of Salm onella Isolates and Antimicrobial Resistance in Poultry Meat from South Korea RAN-HEE YOON,t SE-YEOUN CHA,t BAI WEI, JAE-HEE ROH, HYE-SUK SEO, JAE-YOUNG OH, HYUNG-KWAN JANG*
and
Department o f Infectious Diseases and Avian Diseases, College o f Veterinary Medicine and Korea Zoonosis Research Institute, Chonbuk National University, 79 Gobong-ro, Iksan-si 570-752, South Korea MS 14-018: Received 13 January 2014/Accepted 24 April 2014
ABSTRACT Contamination of Salmonella was assessed in duck and chicken meat collected from supermarkets, traditional markets, internet shopping malls, and wholesale markets in Jeonlado, South Korea, in 2013. Salmonella contamination was found in 51.3% of duck meat samples and 3.7% of chicken meat samples. Salmonella contamination of duck meat samples differed by meat type, i.e., 69.8% of samples of whole ducks and 33.9% of samples of duck pieces. Six serotypes were identified from 64 Salmonella isolates in duck meat: Salmonella Typhimurium (37.5%), Salmonella Enteritidis (21.8%), Salmonella Stanley (3.1%), Salmonella Regent (1.6%), Salmonella Winterthur (3.1%), and Salmonella Westhampton (1.6%). All isolates were resistant to one or more antibiotics. Resistance to sulfisoxazole was most common (93.8% of isolates), followed by resistance to nalidixic acid (59.4%), ceftazidime (26.6%), and ampicillin (26.6%). To our knowledge, this study is the first to report Salmonella contamination in duck meat from Korea. Duck meat should be considered an important source of foodbome pathogens.
Salmonella is a significant cause of foodbome illness in humans. Antibiotic resistance is one of the world’s most important public health problems. The use of antimicrobials in veterinary medicine may promote the development of resistant bacteria or resistance genes that can be transferred to bacteria that cause human disease (14). Thus, resistance among Salmonella strains found in animals and their food products should be monitored. Food of animal origin, particularly poultry and their products, is an important source of human salmonellosis (13). From 2003 to 2005 in the United Kingdom, Salmonella contamination was higher in duck meat (29% of samples) than in chicken (5%), turkey (5%), or other poultry (8%) (12). Healthy domestic ducks can carry Salmonella enterica, which can then spread to humans (1). Duck is the third most common poultry meat in the world and the second most common in Asia, including Korea. Korea is the seventh largest producer of duck meat after China, France, Malaysia, Myanmar, Vietnam, and Thailand (7). However, information on the prevalence of Salmonella serotypes in ducks worldwide is limited. Studies conducted in Korea have revealed a high carriage rate of Salmonella on duck farms (54.3%) (4), but no study has been conducted on the contamination of retail duck meat. The aim of this study was to investigate the prevalence of Salmonella contamination in poultry meat products from South Korea and to characterize all isolates based on their antimicrobial resistance. * Author for correspondence. Tel: (82) 63-850-0945; Fax: (82) 63-8589155; E-mail: [email protected]. f These authors contributed equally to this study.
MATERIALS AND METHODS Sample collection. A total of 109 raw duck meat products and 80 raw chicken meat products were collected from January to March 2013 in Jeonbuk Province, Korea. Meat samples (two or three samples from each market) were collected on each sampling day, and the retail markets were visited one or two times each. Poultry samples were obtained from four types of markets: both meats were obtained from supermarkets, traditional markets, and internet shopping malls, and duck meat only was obtained from wholesale markets (Table 1). The collected samples were stored on ice in an ice box and transported to the laboratory within 2 h after collection. Analyses were completed upon arrival at the laboratory or after storage at 4°C for no longer than 1 day. Isolation and identification of Salmonella. Whole body samples were placed in a sterile plastic bag that contained 400 ml of sterile buffered peptone water (BPW; Difco, BD, Sparks, MD) and shaken for 2 min. For duck pieces and chicken breasts, 25-g samples were placed in a sterile plastic bag in sterile BPW (1:10 dilution) and homogenized for 2 min by stomaching (Stomacher 80 Lab Blender, Seward, Worthington, UK). The whole body rinsate and the homogenized samples were incubated at 37°C for 24 h. One hundred microliters of enriched BPW culture was transferred into 10 ml of Rappaport-Vassiliadis broth (RV; Oxoid, Basingstoke, UK) and incubated at 42°C for 24 h for selective enrichment. A loopful of each RV culture was streaked onto xylose lysine deoxycholate agar (Difco, BD) and brilliant green agar or brilliance Salmonella agar base (Oxoid), and the plates were incubated overnight at 37°C. Presumptive Salmonella colonies were further tested with a Salmonella latex test kit (Oxoid). Serotyping was performed using antisera (Difco, BD) in slide and tube agglutination tests based on the presence of the
1580
YOON ET AL.
J. Food Prot., Vol. 77, No. 9
TABLE 1. Korea market types Market type
Description
Supermarket Traditional Internet Wholesale
Large self-service store that sells food and various everyday household goods Open food market in wet market, including butcher shops Goods available from a seller over the Internet using a Web browser Sale of goods and services to buyers for resale or business use
somatic O antigen and flagellar antigens according to the Kauffmann-White scheme.
Antibiotic susceptibility test. Antimicrobial susceptibility testing was conducted using the disc diffusion method o f the Clinical and Laboratory Standards Institute (CLSI) (6). The isolates were tested against 16 antimicrobials: amikacin (An), ampicillin (Am), ceftazidime (Caz), ceftriaxone (Cro), cefazolin (Cf), chloramphenicol (C), ciprofloxacin (Cip), gentamicin (Gm), imipenem (Ipm), kanamycin (K), nalidixic acid (Na), streptomycin (S), sulfisoxazole (G), tetracycline (Te), amoxicillin-clavulanic acid (Amc), and trimethoprim-sulfamethoxazole (Sxt) (BD, Full erton, CA). Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 29213 were used as quality control strains. The results were interpreted according to CLSI guidelines. Statistical analysis. Significant differences among Salmo nella isolation rates were analyzed using the chi-square test. P values < 0.05 were considered statistically significant.
RESULTS Prevalence of Salmonella. All samples were analyzed for Salmonella contamination (Table 2). From whole ducks, 69.8% of the isolates were positive for Salmonella. From the 64 isolates, six serotypes were identified: Salmonella Typhimurium (24 isolates), Salmonella Enteritidis (14), Salmonella Stanley (2), Salmonella Regent (1), Salmonella Winterthur (2), and Salmonella Westhampton (1). The serotype could not be determined for 20 isolates. The predominant serotypes were Salmonella Typhimurium and Salmonella Enteritidis. Eight samples had two kinds of Salmonella contamination. Eighty raw chicken meat samples were analyzed for Salmonella contamination (Table 2). The overall Salmonella prevalence on raw chicken meat at retail stores was 3.7%, and three serotypes were isolated: Salmonella Typhimurium, Salmonella En teritidis, and untypable.
Antibiotic susceptibility analysis. The 64 isolates from duck meats were tested against 16 antimicrobial agents. All isolates were resistant to at least one antimicro bial tested. The highest resistance rate observed was to sulfisoxazole (93.8%) followed by nalidixic acid (59.4%), ceftazidime and ampicillin (26.6% each), streptomycin (18.8%), cefazolin (17.2%), and ceftriaxone and trimetho prim-sulfamethoxazole (12.5%). There were no strains resistant to ciprofloxacin. The antibiotic susceptibility patterns of the isolates are shown in Table 3. Fifty-five (85.9%) of the 64 isolates were resistant to two or more antimicrobials, and 28 (43.7%) were resistant to three or more antimicrobials. Thirty-eight different antimicrobial resistance patterns were identified. The most frequent resistance type (16 isolates) was the NaG pattern (sulfisox azole and nalidixic acid), and 15, 8, 2, 2, 1, and 1 resistant pattern was identified for Salmonella Typhimurium, Sal monella Enteritidis, Salmonella Stanley, Salmonella Win terthur, Salmonella Regent, and Salmonella Westhampton isolates, respectively. All three chicken isolates were resistant to at least five antimicrobials tested. The Salmonella Enteritidis (NaGSTeAmAmc), Salmonella Ty phimurium (GSTeAmAmc), and untyped (NaSTeAmAmc) isolates had different patterns. DISCUSSION Salmonella contamination in duck and chicken meat was surveyed in this study. The results indicate that Salmonella contamination in duck meat (56 [51.3%] of 109 samples) was significantly higher than that in chicken meat (3 [3.7%] of 80 samples). These findings are in agreement with those reported from the United Kingdom (12). The prevalence of Salmonella in retail duck meat obtained in this study was higher than that in previous reports; 10% in Malaysia and 29% in the United Kingdom (1, 12). The prevalence of Salmonella in chicken meat was
TABLE 2. Isolation o /S alm onella/rom duck meat and chicken meat collected from supermarkets, traditional markets, internet shopping, and wholesale market No. of positive samples/no. of samples tested (% positive)
Sample Duck
Chicken
NT, not tested.
Sample type Whole Pieces Total Whole Breast Total
Supermarkets (n = 6) 11/13 5/16 16/29 2/24 0/15 2/39
(84.0) (31.3) (55.1) (8.3) (0) (5.1)
Traditional markets (n = 5) 11/15 (73.3) 2/9 (22.2) 13/24 (54.1) 0/12 (0) NT 0/12 (0)
Internet shopping (n = 6) 6/8 5/12 11/20 0/12 1/17 1/29
(75.0) (41.7) (55.0) (0) (5.9) (3.4)
Wholesale markets (n = 7) 9/17 (52.9) 7/19 (36.8) 16/36 (44.4) NT' NT NT
Total 37/53 19/56 56/109 2/48 1/32 3/80
(69.8) (33.9) (51.3) (4.2) (3.1) (3.7)
1581
PREVALENCE OF SALMONELLA IN POULTRY MEAT
J. Food Prot., Vol. 77, No. 9
i V O ' s O ’- - V O V O ' O v« O v O ^ O ’-Hi vO
'O
vo
VO
o4
( N
Research Note
Prevalence of Salm onella Isolates and Antimicrobial Resistance in Poultry Meat from South Korea RAN-HEE YOON,t SE-YEOUN CHA,t BAI WEI, JAE-HEE ROH, HYE-SUK SEO, JAE-YOUNG OH, HYUNG-KWAN JANG*
and
Department o f Infectious Diseases and Avian Diseases, College o f Veterinary Medicine and Korea Zoonosis Research Institute, Chonbuk National University, 79 Gobong-ro, Iksan-si 570-752, South Korea MS 14-018: Received 13 January 2014/Accepted 24 April 2014
ABSTRACT Contamination of Salmonella was assessed in duck and chicken meat collected from supermarkets, traditional markets, internet shopping malls, and wholesale markets in Jeonlado, South Korea, in 2013. Salmonella contamination was found in 51.3% of duck meat samples and 3.7% of chicken meat samples. Salmonella contamination of duck meat samples differed by meat type, i.e., 69.8% of samples of whole ducks and 33.9% of samples of duck pieces. Six serotypes were identified from 64 Salmonella isolates in duck meat: Salmonella Typhimurium (37.5%), Salmonella Enteritidis (21.8%), Salmonella Stanley (3.1%), Salmonella Regent (1.6%), Salmonella Winterthur (3.1%), and Salmonella Westhampton (1.6%). All isolates were resistant to one or more antibiotics. Resistance to sulfisoxazole was most common (93.8% of isolates), followed by resistance to nalidixic acid (59.4%), ceftazidime (26.6%), and ampicillin (26.6%). To our knowledge, this study is the first to report Salmonella contamination in duck meat from Korea. Duck meat should be considered an important source of foodbome pathogens.
Salmonella is a significant cause of foodbome illness in humans. Antibiotic resistance is one of the world’s most important public health problems. The use of antimicrobials in veterinary medicine may promote the development of resistant bacteria or resistance genes that can be transferred to bacteria that cause human disease (14). Thus, resistance among Salmonella strains found in animals and their food products should be monitored. Food of animal origin, particularly poultry and their products, is an important source of human salmonellosis (13). From 2003 to 2005 in the United Kingdom, Salmonella contamination was higher in duck meat (29% of samples) than in chicken (5%), turkey (5%), or other poultry (8%) (12). Healthy domestic ducks can carry Salmonella enterica, which can then spread to humans (1). Duck is the third most common poultry meat in the world and the second most common in Asia, including Korea. Korea is the seventh largest producer of duck meat after China, France, Malaysia, Myanmar, Vietnam, and Thailand (7). However, information on the prevalence of Salmonella serotypes in ducks worldwide is limited. Studies conducted in Korea have revealed a high carriage rate of Salmonella on duck farms (54.3%) (4), but no study has been conducted on the contamination of retail duck meat. The aim of this study was to investigate the prevalence of Salmonella contamination in poultry meat products from South Korea and to characterize all isolates based on their antimicrobial resistance. * Author for correspondence. Tel: (82) 63-850-0945; Fax: (82) 63-8589155; E-mail: [email protected]. f These authors contributed equally to this study.
MATERIALS AND METHODS Sample collection. A total of 109 raw duck meat products and 80 raw chicken meat products were collected from January to March 2013 in Jeonbuk Province, Korea. Meat samples (two or three samples from each market) were collected on each sampling day, and the retail markets were visited one or two times each. Poultry samples were obtained from four types of markets: both meats were obtained from supermarkets, traditional markets, and internet shopping malls, and duck meat only was obtained from wholesale markets (Table 1). The collected samples were stored on ice in an ice box and transported to the laboratory within 2 h after collection. Analyses were completed upon arrival at the laboratory or after storage at 4°C for no longer than 1 day. Isolation and identification of Salmonella. Whole body samples were placed in a sterile plastic bag that contained 400 ml of sterile buffered peptone water (BPW; Difco, BD, Sparks, MD) and shaken for 2 min. For duck pieces and chicken breasts, 25-g samples were placed in a sterile plastic bag in sterile BPW (1:10 dilution) and homogenized for 2 min by stomaching (Stomacher 80 Lab Blender, Seward, Worthington, UK). The whole body rinsate and the homogenized samples were incubated at 37°C for 24 h. One hundred microliters of enriched BPW culture was transferred into 10 ml of Rappaport-Vassiliadis broth (RV; Oxoid, Basingstoke, UK) and incubated at 42°C for 24 h for selective enrichment. A loopful of each RV culture was streaked onto xylose lysine deoxycholate agar (Difco, BD) and brilliant green agar or brilliance Salmonella agar base (Oxoid), and the plates were incubated overnight at 37°C. Presumptive Salmonella colonies were further tested with a Salmonella latex test kit (Oxoid). Serotyping was performed using antisera (Difco, BD) in slide and tube agglutination tests based on the presence of the
1580
YOON ET AL.
J. Food Prot., Vol. 77, No. 9
TABLE 1. Korea market types Market type
Description
Supermarket Traditional Internet Wholesale
Large self-service store that sells food and various everyday household goods Open food market in wet market, including butcher shops Goods available from a seller over the Internet using a Web browser Sale of goods and services to buyers for resale or business use
somatic O antigen and flagellar antigens according to the Kauffmann-White scheme.
Antibiotic susceptibility test. Antimicrobial susceptibility testing was conducted using the disc diffusion method o f the Clinical and Laboratory Standards Institute (CLSI) (6). The isolates were tested against 16 antimicrobials: amikacin (An), ampicillin (Am), ceftazidime (Caz), ceftriaxone (Cro), cefazolin (Cf), chloramphenicol (C), ciprofloxacin (Cip), gentamicin (Gm), imipenem (Ipm), kanamycin (K), nalidixic acid (Na), streptomycin (S), sulfisoxazole (G), tetracycline (Te), amoxicillin-clavulanic acid (Amc), and trimethoprim-sulfamethoxazole (Sxt) (BD, Full erton, CA). Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 29213 were used as quality control strains. The results were interpreted according to CLSI guidelines. Statistical analysis. Significant differences among Salmo nella isolation rates were analyzed using the chi-square test. P values < 0.05 were considered statistically significant.
RESULTS Prevalence of Salmonella. All samples were analyzed for Salmonella contamination (Table 2). From whole ducks, 69.8% of the isolates were positive for Salmonella. From the 64 isolates, six serotypes were identified: Salmonella Typhimurium (24 isolates), Salmonella Enteritidis (14), Salmonella Stanley (2), Salmonella Regent (1), Salmonella Winterthur (2), and Salmonella Westhampton (1). The serotype could not be determined for 20 isolates. The predominant serotypes were Salmonella Typhimurium and Salmonella Enteritidis. Eight samples had two kinds of Salmonella contamination. Eighty raw chicken meat samples were analyzed for Salmonella contamination (Table 2). The overall Salmonella prevalence on raw chicken meat at retail stores was 3.7%, and three serotypes were isolated: Salmonella Typhimurium, Salmonella En teritidis, and untypable.
Antibiotic susceptibility analysis. The 64 isolates from duck meats were tested against 16 antimicrobial agents. All isolates were resistant to at least one antimicro bial tested. The highest resistance rate observed was to sulfisoxazole (93.8%) followed by nalidixic acid (59.4%), ceftazidime and ampicillin (26.6% each), streptomycin (18.8%), cefazolin (17.2%), and ceftriaxone and trimetho prim-sulfamethoxazole (12.5%). There were no strains resistant to ciprofloxacin. The antibiotic susceptibility patterns of the isolates are shown in Table 3. Fifty-five (85.9%) of the 64 isolates were resistant to two or more antimicrobials, and 28 (43.7%) were resistant to three or more antimicrobials. Thirty-eight different antimicrobial resistance patterns were identified. The most frequent resistance type (16 isolates) was the NaG pattern (sulfisox azole and nalidixic acid), and 15, 8, 2, 2, 1, and 1 resistant pattern was identified for Salmonella Typhimurium, Sal monella Enteritidis, Salmonella Stanley, Salmonella Win terthur, Salmonella Regent, and Salmonella Westhampton isolates, respectively. All three chicken isolates were resistant to at least five antimicrobials tested. The Salmonella Enteritidis (NaGSTeAmAmc), Salmonella Ty phimurium (GSTeAmAmc), and untyped (NaSTeAmAmc) isolates had different patterns. DISCUSSION Salmonella contamination in duck and chicken meat was surveyed in this study. The results indicate that Salmonella contamination in duck meat (56 [51.3%] of 109 samples) was significantly higher than that in chicken meat (3 [3.7%] of 80 samples). These findings are in agreement with those reported from the United Kingdom (12). The prevalence of Salmonella in retail duck meat obtained in this study was higher than that in previous reports; 10% in Malaysia and 29% in the United Kingdom (1, 12). The prevalence of Salmonella in chicken meat was
TABLE 2. Isolation o /S alm onella/rom duck meat and chicken meat collected from supermarkets, traditional markets, internet shopping, and wholesale market No. of positive samples/no. of samples tested (% positive)
Sample Duck
Chicken
NT, not tested.
Sample type Whole Pieces Total Whole Breast Total
Supermarkets (n = 6) 11/13 5/16 16/29 2/24 0/15 2/39
(84.0) (31.3) (55.1) (8.3) (0) (5.1)
Traditional markets (n = 5) 11/15 (73.3) 2/9 (22.2) 13/24 (54.1) 0/12 (0) NT 0/12 (0)
Internet shopping (n = 6) 6/8 5/12 11/20 0/12 1/17 1/29
(75.0) (41.7) (55.0) (0) (5.9) (3.4)
Wholesale markets (n = 7) 9/17 (52.9) 7/19 (36.8) 16/36 (44.4) NT' NT NT
Total 37/53 19/56 56/109 2/48 1/32 3/80
(69.8) (33.9) (51.3) (4.2) (3.1) (3.7)
1581
PREVALENCE OF SALMONELLA IN POULTRY MEAT
J. Food Prot., Vol. 77, No. 9
i V O ' s O ’- - V O V O ' O v« O v O ^ O ’-Hi vO
'O
vo
VO
o4
( N
