Antimicrobial resistance and serotype distribution of Streptococcus pneumoniae strains isolated in southern Taiwan.

The antimicrobial susceptibilities and serotypes of 115 Streptococcus pneumonia strains isolated in southern Taiwan from January 1990 to December 1993 were determined. All isolates were susceptible to cephalothin, cefotaxime, trimethoprim/sulfamethoxazole and vancomycin, and 14 of the isolates were resistant to penicillin G. The oxacillin disk method for presumptive detection of resistance to penicillin had a sensitivity of 85.7% and specificity of 97.0%. Resistance rates were as follows: erythromycin 62.2%, tetracycline 71.3%, clindamycin 46.1% and chloramphenicol 19.1%. Eighty-four percent of the isolates were resistant to one or more of the antibiotic tested. Multiple resistance (to three or more classes of antibiotics) was identified in 40.9% of all the isolates and 100% of penicillin-resistant isolates. The predominant serotypes were: 14 (19.1%), 3 (17.4%), 23 (15.7%), 6 (10.4%), and 15 (6.1%). Serotypes 14 and 63 most commonly caused childhood infections, while serotypes 3 and 23 were frequently encountered in adults. The proportion of coverage in 23-valent pneumococcal polysaccharide vaccine was 92.2%, if vaccine-related serotypes were considered to be cross-protecting. Seven (58%) of 12 typable penicillin-resistant isolates belonged to serotype 23 and two (16.7%) to serotype 6. All isolates of serotype 14, 23, 15 and 19 were resistant to one or more antibiotics. Multiple drug resistance was frequently associated with serotype 23 (31.9%), 14 (23.4%) and 6 (17.0%). Sixty-five percent of isolates of serotype 3 were susceptible to all antibiotics tested. The high level of antimicrobial resistance in S. pneumoniae mandates the continuous surveillance of resistance and the strict control of antibiotic use in Taiwan.