Bacteriology of acute otitis media: A new perspective Mark A. Del B e c c a r o , MD, Paul M. M e n d e l m a n , MD, A n d r e w F. Inglis, MD, Mark A. Richardson, MD, N e w t o n O. D u n c a n , MD, C a r l a R. Clausen, PhD, a n d T e r r e n c e L. Stull, MD From the Children's Hospital and Medical Center, and the Departments of Pediatrics, Otolaryngology, and Laboratory Medicine, University of Washington, Seattle, and the Department of Pediatrics, Medical College of Pennsylvania, Philadelphia

Pathogenic bacteria were isolated from 90% of patients with acute otitis media. This higher-than-expected rate of positive cultures was probably related to the meticulous bacteriologic techniques used. (J PEDIATR1992;120:81-4)

Acute otitis media, one of the most common infections in early childhood, is a frequent reason for visits to health care providers. 1 In a large prospective study, Teele et al. 1 detected AOM in 62% and 83% of children by 1 and 3 years of age, respectively. Seventeen percent of those less than 1 year of age and 40% of those less than 3 years of age had _>3 episodes of AOM. Despite this high frequency of AOM, otoscopic findings are believed by some to be unreliable and inaccurate for predicting AOM resulting from bacterial pathogens. Schwartz et al. 2 studied the association between the appearance of the tympanic membrane and results of tympanocentesis culture. A 38% culture-negative rate was observed for a red TM and a 20% culture-negative rate was observed for a yellow TM. These results are in agreement with numerous studies that have reported 20% to 50% of middle ear cultures from patients with AOM to be sterile) -5 In addition, textbooks 6 and review articles 7 consistently state that 25% to 35% of middle ear cultures are sterile. This high frequency of sterile cultures of specimens from patients with AOM is poorly understood. Viral infections

Supported in part by The Upjohn Company, Kalamazoo Mich. Presented in part at the Thirty-first Annual Meeting of the Ambulatory Pediatric Association,New Orleans, La., April 1991, and at the Fifth International Symposium on Recent Advances in Otitis Media, Fort Lauderdale, Fla., May 20-24, 1991. Submitted for publication May 3, 1991; accepted Aug. 6, 1991. Reprint requests: Mark A. Del Beccaro, MD, c/o Emergency SerVices, Children's Hospital and Medical Center, PO Box C5371, Seattle, WA 98105. 9/22/32933

have been implicated as a possible cause. 4, 8 Attempts to isolate anaerobes or mycoplasmas have not been successful.6"8 For children with signs of AOM the sterile cultures could also be a result of technical difficulties with the isolation of bacteria from the tympanocentesis fluid. This report describes our isolation of bacterial pathogens from patients with AOM. METHODS

Patients between 2 months and 18 years of age with signs of AOM (fever, irritability, or~ear pain) ~ 7 days in duration were recruited for our study as part of two multicenter, single-blind studies comparing the efficacy and safety of a new extended-spectrum, orally administered cephalosporin AOM CI TM

Acute otitis media Confidence interval Tympanic membrane

plus cefpodoxime proxetil (Doxef) with either amoxicillin plus cla~,ulanate (Augmentin) (study 1, November 1989 to May 1990) or cefixime (Suprax) (study 2, October 1990 to June 1991). This report discusses only the culture results for the patients enrolled at Children's Hospital and Medical Center, Seattle, Wash. Children were recruited from the emergency department (n = 9) or acute care clinic (n = 51 ), exclusively during regular otolaryngology clinic hours. The acute care clinic is open in the afternoon and evening and is staffed by pediatric nurse practitioners who see children with minor illnesses. Children with A O M who were enrolled in study 1 (n = 32) were compared with children seen in the Same



Clinical and laboratory observations

clinic who also had a diagnosis of AOM. There were 99 children (32 in the study, 67 not enrolled) who had a diagnosis of otitis media and were seen in either the emergency department or the acute care clinic during otolaryngology clinic hours. Of the 67 patients not enrolled in the study, 30 were not eligible for at least one of the following reasons: already receiving antibiotics (10); allergic to penicillins and cephalosporins (3); too young (less than 2 months in age) or too sick (admitted or immunocompromised) (6); without a guardian available or living in another state (5); or having ear drainage for more than 2 days or tympanostomy tubes (6). The parents or guardians of almost all of the remaining 37 eligible patients were asked but declined to participate in the study. In addition to the preceding 99 children seen in either the emergency department or the acute care clinic during otolaryngology clinic hours, another 178 children had a diagnosis of A O M on the same days but not while the otolaryngology clinic was open. To determine whether the patients enrolled were different from the nonenrolled patients, the next two children (n -- 64) with a diagnosis of AOM to be seen after a child who was enrolled in study 1 were selected for comparison. Their records were abstracted for demographic features, history, and physical examination findings. This study was approved by the human subjects committee. Informed consent was obtained from the parents or guardians of all children. Assent was obtained from all children older than 7 years. Tympanocentesis was performed by one of the otolaryngology investigators. Cerumen was gently curetted from the ear canal, and a culture specimen was obtained from the surface of the tympanic membrane with a sterile calcium alginate wire swab. Tympan0centesls and aspiration of middle ear fluid were performed by means of standard technique. 6 After tympanocentesis the fluid specimen inside the needle hub, syringe, or trap was taken as it was or adsorbed with a sterile calcium alginate wire swab, placed in a sterile container, and taken immediately to the microbiology laboratory for culture and Gram staining. The middle and external ear specimens were inoculated onto blood, chocolate, and MacConkeY agar plates and aerobically incubated at 35 ~ C in 5% to 10% carbon dioxide. Middle ear specimens were also inoculated and incubated anaerobically on Brucella blood agar plates and in trypticase soy yeast and thioglycollate broths. Swab tips were routinely left in the trypticase soy yeast broth. If there was no growth on the primary plates, a blind subculture of trypticase soy yeast broth was started 48 hours after the initial inoculation. Bacteria were considered to be pathogens if they were isolated only from the middle ear fluid. The presence of the /3-1actamase enzyme was determined by

The Journal of Pediatrics January 1992 means of the chromogenic cephalosporin test with nitrocefin (Cefinase; Becton Dickinson Microbiological Systems, Cockeysville, Md.). Children were seen three times after the initial visit, on days 3 to 5, days 10 to 12, and days 24 to 33. If the child had recurrent otitis after the completion of therapy, a second tympanocentesis was performed. Recurrent A O M was defined as fever, irritability, or ear pain, with either redness or bulging of the TM. Strains of Streptococcus pneumoniae associated with recurrences were sent for serotype analysis and susceptibility testing to the laboratory of Richard Facklain, PhD, at the Centers for Disease Control, Atlanta, Ga., or to Barry Gray, MD, University of Alabama. Strains of Haemophilus influenzae associated with recurrences were analyzed with restriction fragment length polymorphisms of the chromosomal D N A detected by ribosomal ribonucleic acid restriction fragment length polymorphisms as follows: purified chromosomal D N A was digested to completion with the EcoRI restriction enzyme. The fragments were separated by agarose gel electrophoresis and blotted to nitrocellulose by the method of Southern. 9 The blot was probed with Escherichia coli ribosomal R N A labeled with 32p and hybridization bands were detected by autoradiography.1~ Data were encoded and analyzed by means of Epi Info, version 5, computer software program (USD Inc., Stone Mountain, Ga.). RESULTS Sixty children were enrolled in the study. Thirty-six (60%) were female, 44 (73%) were white, and 40 (67%) were uninsured. The median age was 2.0 years (range, 0.5 to 13.5 years) and the mean body temperature of these children when they were first seen was 37.2 ~ C (SD, 1.0; range 35.5 ~ to 39.3~ Ninety-seven percent had a history of upper respiratory tract infection during the preceding week182% had ear pain, 65% had a history of fever, 25% had vomiting, and 23% had diarrhea. Children who were enrolled in the study were not significantly different from other children with AOM seen in the emergency department or acute care clinic with regard to any of the abovementioned characteristics or symptoms. All 60 patients in the study had a red TM, 56 (93%) had dullness, 55 (92%) had decreased mobility detected by either pneumatic otoscopy or tympanogram, and 55 (92%) had some degree of bulging of the TM. The 64 control patients all had redness of the TM and 90% had either a bulging TM or purulent drainage. Mobility and dullness of the TM were infrequently recorded in the charts of control patients. Fifty-five (92%, 95% confidence interval = 82% to 97%) of the 60 patients had cultures that yielded pathogens (Table I). Eight patients with bilateral otitis consented to bilateral tympanocentesis; seven of the eight had the same pathogens isolated from both ears. One of the eight patients

Volume 120 Number 1

Clinical a n d laboratory observations


Table I. Bacteriology of middle ear isolates Total Strain

Primary plate

Broth subculture*



S. pneumoniae M. catarrhalis'[ H. influenzae'~ Streptococcus pyogenes a-Streptococcus Enterobacter cloacae Moraxella phenylpyruvica Total (%)

29 12 12 3 0 1 0 57 (87.7%)

2 3 1 0 1 0 1 8 (12.3%)

31 15 13 3 1 1 1 65

47.7 23.1 20.0 4.6 1.5 1.5 1.5 (100%)~

*No growth observed on primary plates. ~'Thirteen of fifteen (87%) M. catarrhalis and 4 of 13 (31%) H. influenzae isolates produced the B-iactamase enzyme. :~Ninechildren had mixedcultures:S. pneumoniae with H. influenzae (n = 4), S. pneumoniae with M. catarrhalis (n = 2), S. pneumoniae with S. pyogenes (n = 1), S. pneumoniae with E. cloacae (n = 1), and S. pneumoniae with both M. catarrhalis and H. influenzae (n = 1).

Table II. Bacteriology of initial and recurrent episodes of A O M Initial culture

Recurrent culture

Day of recurrence*


H. influenzae ( - ) H. influenzae ( - ) H. influenzae (+) S. pneumomae (23F) S. pneumomae S. pneumomae S. pneumontae (14) S. pneumomae S. pneumontae and E. cloacae M. catarrhalis (+) S. pneumoniae and H. influenzae ( - ) S. pneumoniae (6) S. pneumoniae (33)

H. influenzae ( - ) H. influenzae ( - ) H. influenzae ( - ) S. pneumoniae (14) M . catarrhalis (+) M. catarrhalis (+) and H. influenzae (-) S. pneumoniae (14) H. influenzae (+) H. influenzae (+) and H. influenzae ( - ) S. pneumoniae H. influenzae ( - ) S. pneumoniae (19) S. pneumoniae (33)

4 5 5 8 5 14 17 18 4 6 6 3 17

Yes Yes No No NA NA Yes NA NA NA Yes No Yes

+ and -, Presence or absence of ~3-1actamaseenzyme; (23F), (14), (6), (19), and (33), serotype (see text); NA, not applicable. *Number of days after last dose of antibiotic. tBased on RNA typing and serotype analysis (see text). who u n d e r w e n t bilateral tympanocentesis h a d pathogens in only one of the two ear cultures. Seventeen of the initial 65 middle ear isolates (26%, 95% CI = 15% to 37%) produced the t3-1actamase enzyme. Seventeen patients (28%, 95% CI = 22% to 34%) h a d recurrences; 13 of the 17 consented to a second t y m p a n o c e n tesis; all 13 were culture positive at the second t y m p a n o centesis. Eight of the recurrences (62%, 95% CI = 31% to 84%) were due to different pathogens (Table II). In total, 75 (93%, 95% CI = 87% to 99%) of the 81 tympanocentesis procedures yielded pathogens. DISCUSSION T h e recovery of pathogens from more t h a n 90% of ear cultures stands in contrast to the previously m e n t i o n e d average of 50% to 80% reported in the literature. This difference could result from either selection bias or culture technique. M o s t of our patients were recruited from t h e acute care clinic, in which children with minor illnesses are seen.

A n effort was m a d e to recruit all patients with A O M who were eligible. In addition, the patients with A O M who participated in the study showed no differences in presenting symptoms or d e m o g r a p h i c features from other patients who did not participate in the study. W e are not aware of any previous articles t h a t showed how patients who were selected for study compared with nonstudy patients. In previous studies of children with " a c u t e severe otitis" (all with a t e m p e r a t u r e >38.5 ~ C) 6 or children with A O M and a bulging T M ( m a n y with a t e m p e r a t u r e >--39.4 ~ C), 3 the culture-negative rate was still 30% to 50%. O u r subjects did not appear to be more severely ill t h a n other children in our institution with A O M or those in previous studies of children with A O M (e.g., 38.5 ~ C). W e believe t h a t our results are due to differences in culture methods. N o n e of the previously mentioned studies 26, 8 appear to have used blind b r o t h subcultures. Twelve percent of our pathogens were isolated only with this technique. In


Clinical and laboratory observations

addition, in previous studies specimens were sometimes refrigerated for several hours before inoculation onto culture media, whereas all of our specimens were inoculated within 20 minutes of collection. Refrigeration or other delays could contribute to a decrease in viable colonies. The predominance of S. pneumoniae in the initial infections is in agreement with previous findings. 2-8 The increasing importance of Moraxella catarrhalis as a cause of A O M 57 is confirmed in our study. M. catarrhalis accounted for more cases of A O M than H. influenzae did. However, 53% of isolates from our patients with recurrence were/4. influenzae. W e found no evidence that anaerobes or staphylococci are etiologic agents in A O M . Our data confirm those of Carlin et al.,5 who found that 75% of recurrences were due to new bacterial species. In summary, we have shown that pathogenic bacteria are recoverable from more than 90% of patients with A O M and that nearly two thirds of recurrences are due to new pathogens.

The Journal of Pediatrics January 1992





7. 8.


REFERENCES 1. Teele D, Klein J, Rosner B. Epidemiology of otitis media during the first seven years of life in children in greater Boston: a prospective, cohort study. J Infect Dis 1989;160:83-94. 2. Schwartz R, Stool S, Rodriguez W, Grundfast K. Acute otitis


media: toward a more precise definition. Clin Pediatr 1981;20: 549-54. Feingold M, Klein J, Haslam G, Ti!les J, Finland M, Gellis S. Acute otitis media in children: bacteriological findings in middle ear fluid obtained by needle aspiration. Am J Dis Child 1966;111:361-5. Klein B, Dollette F, Yolken R. The role of respiratory syncytial virus and other viral pathogens in aeute otitis media. J PEDIATR 1982;101:16-20. Carlin S, Marchant C, Shurin P, Johnson C, Murdell-Panek D, Barenkamp S. Early recurrences of otitis media: reinfection or relapse? J PEDIATR 1987;110:20-5. Bluestone C, Klein J. Otitis media, ateleetasis, and Eustachian tube dysfunction. In: Bluestone C, Stool S, Scheetz M, eds. Pediatric otolaryngology. Philadelphia: WB Saunders, 1990: 320-538. Wald E. Changing trends in the microbiology of otitis media with effusion. Pediatr Infect Dis J 1984;3:380-3. Halsted C, Lepow M, Balassanian N, Emmerich J, Wolinsky E. Otitis media: clinical observations, microbiology, and evaluation of therapy. Am J Dis Child 1968;115:542-51. Southern E. Detection of specific sequences among DNA fragments separated by gel eleetrophoresis. J Mol Biol 1975;98:503-17. Stull T, LiPuma J, Edlind T. A broad-spectrum probe for molecular epidemiology of bacteria: ribosomal RNA. J Infect Dis 1988;157:280-6.

Safety and immunogenicity of acellular diphtheria-tetanus-pertussis and Haemophilus conjugate vaccines given in combination or at separate injection sites Arthur Kovel, MD, Ellen R. Wald, MD, N a n c y Guerra, PNP, Carol Serdy, RN, a n d Carlton K. Meschievitz, MD, MPH From the University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, and Connaught Laboratories, Inc., Swiftwater, Pennsylvania This prospective, double-blind, randomized trial c o m p a r e d the immunogenicity and reactogenicity of acellular diphtheria-tetanus-pertussis vaccine and Haemophilus influenzae type b conjugate vaccine-diphtheria toxoid conjugate, given at separate injection sites or at a single site, in 79 children 18 months of a g e who had received three prior immunizing doses of whole-cell diphtheriatetanus-pertussis vaccine. No significant differences were observed. (J PEDIATR 1992;120:84-7) Supported by Connaught Laboratories, Inc., Swiftwater, Pa. Submitted for publication May 9, 1991; accepted July 31, 1991. Reprint requests: A. Kovel, MD, Allegheny General Hospital, Department of Pediatrics, 320 E. North Ave., Pittsburgh, PA 15212.


Concern over reactions to whole-cell pertussis vaccines has prompted the recent development of several acellular diph theria-tetanus-pertussis vaccines.I, 2 The specific antigenic components of the ideal A D T P vaccine have yet to be determined.

Bacteriology of acute otitis media: a new perspective.

Pathogenic bacteria were isolated from 90% of patients with acute otitis media. This higher-than-expected rate of positive cultures was probably relat...
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