Serotype distribution and antimicrobial susceptibility of Streptococcus pneumoniae causing invasive infections and acute otitis media in children

A prospective study was conducted to determine the serotypes and antibiotic resistance patterns of pneumococcal isolates from children with invasive pneumococcal disease (IPD) and acute otitis media (AOM). From October 2001 to May 2002, 65 children with IPD (28 bacteraemic pneumonia, 24 bacteraemia without focus, 7 meningitis, 6 other infections) and 78 with AOM were identified. The most common serotypes causing IPD were 14 (32.3%), 6B (20.0%), 1 (18.5%) and 19F (7.7%) whereas the predominant serotypes causing AOM were 19F (35.9%), 14 (16.7%) and 23F (9.1%). Sixty-nine percent of IPD and 70.5% of AOM were caused by vaccine serotypes. The vaccine serotypes were more commonly encountered in meningitis cases and in children younger than 2 years of age. Intermediate resistance to penicillin was observed in 6 of 65 (9.2%) IPD isolates, one of which was intermediately resistant to cefotaxime (1.6%), whereas none exhibited high-level resistance to penicillin or other beta-lactam antibiotics. A higher proportion of antimicrobial resistance was noted in AOM isolates; 29 of 78 (37.4%) exhibited intermediate resistance and 8 (10.2%) high level resistance to penicillin, four of which had intermediate resistance to cefotaxime. Significant resistance was also noted to erythromycin; 38.5% of IPD and 48.7% of AOM isolates were resistant. Multidrug resistance was observed in one IPD and in eight AOM isolates. Conclusion:these findings have implications in the potential use of 7-valent conjugate vaccine in our region.Abbreviations AOM acute otitis media - IPD invasive pneumococcal disease - MIC minimal inhibitory concentration