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Increasing incidence of penicillin- and ampicillin-resistant middle ear pathogens
W J Rodriguez1, R H Schwartz, M M Thorne
1Children's National Medical Center, Washington, DC, Department of Infectious Disease 20010-2970, USA.
Insights
High rates of antibiotic resistance in common middle ear infection bacteria like Streptococcus pneumoniae and Haemophilus influenzae necessitate reevaluating amoxicillin treatment for acute otitis media, especially in severe cases.
Area of Science:
- Pediatrics
- Infectious Diseases
- Microbiology
Background:
- Acute otitis media (AOM) is a common childhood infection.
- Bacterial pathogens are the primary cause of AOM.
- Antibiotic resistance is a growing concern in treating AOM.
Purpose of the Study:
- To determine the prevalence of bacterial pathogens in pediatric AOM cases.
- To assess the antibiotic resistance patterns of isolated bacteria.
- To inform empirical antibiotic treatment guidelines for AOM.
Main Methods:
- Middle ear fluid samples were collected from 151 children with AOM.
- Bacterial cultures were performed to identify pathogens.
- Antibiotic susceptibility testing was conducted for isolated bacteria.
Main Results:
- 95% of AOM cases yielded bacterial pathogens.
- Streptococcus pneumoniae (37%), Haemophilus influenzae (27%), and Moraxella catarrhalis (25%) were the most common pathogens.
- High resistance rates were observed: 21% of S. pneumoniae to penicillin, 62% of H. influenzae and 98% of M. catarrhalis to ampicillin.
Conclusions:
- Empirical amoxicillin use for AOM should be reconsidered in this community.
- High rates of resistance to ampicillin and penicillin were found.
- Treatment guidelines may need adjustment, particularly for severe AOM presentations.
Abstract:
During a 13-month period ending in January, 1995, we obtained 159 samples of middle ear exudate through tympanocentesis (n = 155) or acute spontaneous otorrhea (n = 4) from 151 children enrolled in therapeutic trials of acute otitis media in a pediatric practice in Northern Virginia. Their ages ranged from < 1 to > 6 years of age (mean, 35 months; median, 22 months). Precise diagnostic criteria for acute otitis media always included bulging outward of all or part of the eardrum, opacification of the eardrum regardless of color and impaired mobility to positive and negative pressure via the pneumatic otoscope. Bacterial pathogens were isolated from middle ear fluid in 95% of these children: Streptococcus pneumoniae was recovered from 61 (37%); Haemophilus influenzae from 45 (27%); Moraxella catarrhalis from 41 (25%); Group A streptococcus from 6 (4%); Staphylococcus aureus from 4 (2%); and no growth or microbes of uncertain significance from 8 (5%). Six of the patients had mixed bacterial cultures; 2 of the 6 had at least one ampicillin-resistant bacteria, and a third had 2 ampicillin-resistant bacteria. Eight patients who failed to improve with antimicrobial treatment had a second tympanocentesis performed or developed spontaneous drainage; on that follow-up culture 3 of 8 cultures had different microorganisms; and 5 of the 8 bacterial specimens were resistant to ampicillin or penicillin. Twenty-one percent of the S. pneumoniae strains recovered from the middle ear were resistant to penicillin. Sixty-two percent of the H. influenzae and 98% of the M. catarrhalis isolates were resistant to ampicillin. Overall bacteria resistant to penicillin or ampicillin were recovered in 54% of middle ear fluid from 46 patients who had received a beta-lactam antibiotic in the preceding month as well as in 57% of middle ear fluids from 105 patients who had not. The empiric use of amoxicillin for treatment of acute otitis media should be reexamined in our community particularly in those who appear ill, have a high fever or have severe unremitting otalgia.