Dissemination of an erythromycin-resistant penicillin-nonsusceptible Streptococcus pneumoniae Poland(6B)-20 clone in Argentina.

Prevalence of serotype 6B penicillin (PEN)-nonsusceptible Streptococcus pneumoniae significantly increased from 15.8% (1993-1997) to 67.3% (1998-2002) (p<0.001) in Argentina. Serogroup 6 ranks fourth among different capsular types within invasive isolates from Argentinean patients <6 years of age. To evaluate whether the increase in PEN resistance in serotype 6B pneumococci was due to the dissemination of one or more clones, the genetic diversity of 93 S. pneumoniae serotype 6B isolates was analyzed. Five BOX-polymerase chain reaction types were obtained (65.5% isolates) and a group of 15 isolates, representing 41.6% of those having a decreased susceptibility to PEN, were further characterized. The antibiotype of these isolates showed their multiresistance, with 100% of the isolates being resistant to erythromycin, 80% to tetracycline, and 73.3% to trimethoprim-sulfamethoxazole. Of the 15 isolates, 13 belonged to the same pulsed-field gel electrophoresis type and galU cluster and were members of the same clone. The identity of the clone was confirmed in four isolates by multilocus sequence typing. The sequence type found (ST315) corresponds to the Poland(6B)-20 clone. In summary, BOX-polymerase chain reaction, pulsed-field gel electrophoresis, and galU polymorphism were useful tools to detect the presence of a clone whose identity was confirmed by multilocus sequence typing. The isolates belonging to Poland(6B)-20 found in this work are described for the first time in Latin America.