ACTIVITY OF ORAL ANTIBIOTICS IN MIDDLE-EAR AND SINUS INFECTIONS CAUSED BY PENICILLIN-RESISTANT STREPTOCOCCUS-PNEUMONIAE - IMPLICATIONS FOR TREATMENT

The increasing prevalence of intermediately and highly penicillin-resi stant strains of Streptococcus pneumoniae is a problem worldwide. Howe ver, optimal management of patients with middle ear and sinus infectio ns caused by resistant pneumococci has not been established. We perfor med agar dilution susceptibility studies on 71 strains of penicillin-r esistant pneumococci (minimum inhibitory concentration (MIC), greater than or equal to 0.1 mu g/ml) recovered from middle ear and sinus cult ures of Houston children against 13 oral antibiotics with the use of b oth established and newly proposed National Committee for Clinical Lab oratory Standards susceptibility criteria. Of the 62 middle ear isolat es 35 (56%) were intermediately resistant and 27 (44%) were highly res istant to penicillin. Of the 9 sinus isolates tested, 5 (56%) were int ermediately resistant (MIC between 0.1 and 1 mu g/ml) and 4 (44%) were highly resistant (MIC greater than or equal to 2 mu g/ml) to penicill in. The MIC(90) increased with increasing penicillin resistance for th e antibiotics tested except for rifampin, ciprofloxacin, loracarbef, c lindamycin and trimethoprim-sulfamethoxazole. None of the highly penic illin-resistant isolates was susceptible to loracarbef or trimethoprim -sulfamethoxazole. The MIC(90) values for clindamycin and rifampin wer e similar for the intermediately and highly penicillin-resistant group s, and the number of susceptible isolates in each group remained great er than 90% for both antibiotics. Thirty-five isolates were resistant to erythromycin but susceptible to clindamycin, a susceptibility patte rn distinctly different from that seen in South Africa and Europe, whe re clindamycin resistance parallels erythromycin resistance. Further s tudy is necessary to correlate in vitro susceptibility data with clini cal outcome from infections caused by penicillin-resistant pneumococci because the MIC(90) values for most of the antibiotics tested against the isolates in our study exceeded achievable antibiotic concentratio ns in middle ear effusions.