Incidence of antibiotic-resistant Streptococcus pneumoniae and beta-lactamase-positive Haemophilus influenzae in clinical isolates from patients with otitis media.
BACKGROUND
The prevalence of penicillin-resistant Streptococcus pneumoniae and beta-lactamase-producing Haemophilus influenzae in otitis media infections is increasing; emergence of these pathogens has complicated treatment.


OBJECTIVE
To evaluate the incidence of penicillin resistance and the in vitro activity of amoxicillin/clavulanate, cefaclor, loracarbef, cefixime, trimethoprim/sulfamethoxazole, azithromycin and clarithromycin in S. pneumoniae isolates. The in vitro activity of azithromycin, clarithromycin and cefaclor was also evaluated in beta-lactamase-positive and -negative isolates of H. influenzae.


METHODS
Bacterial isolates of S. pneumoniae and H. influenzae were obtained by tympanocentesis and subsequent culture of middle ear effusion from children with acute otitis media enrolled in a multicenter trial. Susceptibility to test agents was assessed by disk diffusion and broth dilution techniques with criteria established by the National Committee for Clinical Laboratory Standards.


RESULTS
Nineteen (31%) of the 61 S. pneumoniae isolates were resistant to penicillin. A significantly lower percentage of the S. pneumoniae isolates were resistant to azithromycin (16%) and clarithromycin (11%) than to penicillin, amoxicillin/ clavulanate, cefaclor, loracarbef or cefixime (31% in all cases). Azithromycin was also more active than cefaclor and significantly more active than clarithromycin against the 55 H. influenzae isolates.


CONCLUSIONS
The susceptibility of resistant and nonresistant strains of S. pneumoniae to azithromycin and clarithromycin and of isolates of H. influenzae to azithromycin, coupled with penetration of azithromycin into the middle ear, may provide a significant advantage in the treatment of otitis media.
McLinn
S
S
Scottsdale Pediatric Center, AZ 85260-6743, USA.
Williams
D
D
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017963:Azithromycin / Q000494:pharmacology*; D002648:Child; D017291:Clarithromycin / Q000494:pharmacology; D006192:Haemophilus Infections / Q000188:drug therapy* / Q000453:epidemiology / Q000382:microbiology; D006193:Haemophilus influenzae / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D015994:Incidence; D008826:Microbial Sensitivity Tests; D010033:Otitis Media / Q000188:drug therapy / Q000382:microbiology*; D010403:Penicillin Resistance; D011008:Pneumococcal Infections / Q000188:drug therapy* / Q000453:epidemiology / Q000382:microbiology; D013296:Streptococcus pneumoniae / Q000187:drug effects*; D001618:beta-Lactamases / Q000096:biosynthesis
D000900:Anti-Bacterial Agents; D017963:Azithromycin; D001618:beta-Lactamases; D017291:Clarithromycin