Antimicrob Agents Chemother. 2016 Aug 29. pii: AAC.00673-16. [Epub ahead of print]
Streptococcus pneumoniae of Serotypes 9 and 14 Circulating in Brazil Over a 23-Year Period Prior to the Introduction of PCV10: Role of International Clones in the Evolution of Antimicrobial Resistance and Description of a Novel Genotype.
Antimicrobial resistant pneumococcal strains have been detected worldwide since the 1960's. In Brazil, the first penicillin non-susceptible pneumococci (PNSP) were reported in the 1980's, and their emergence and dissemination have been mainly attributed to serogroup 9 and serotype 14 strains, especially those highly related to recognized international clones. In the present study, antimicrobial susceptibility testing and Multilocus Sequence Typing (MLST) were performed on 315 pneumococcal isolates belonging to serogroup 9 (n=99) or serotype 14 (n=216), recovered from patients or asymptomatic carriers between 1988 and 2011 in Brazil, in order to trace changes in antimicrobial resistance and genotypes prior to the full introduction of the pneumococcal conjugate vaccine in the country. Over the 23-year study period, PNSP levels increased and four clonal complexes (CC156, CC66, CC15 and CC5401) have played important roles in the evolution and dissemination of pneumococcal isolates belonging to serogroup 9 and serotype 14, as well as in the emergence of antimicrobial resistance, in the pre-pneumococcal vaccination era. The earliest PNSP strains detected in this study belonged to serotype 9N/ST66 and were single locus variants of the international clone Tennesse14-18 ST67 (CC66). The first serotype 14 PNSP isolates were identified in 1990, and were related to the England14-9 ST9 (CC15) clone. Serotype 14 PNSP variants of the Spain9V-3 ST156 clone with elevated penicillin MICs and non-susceptibility to other beta-lactams were detected in 1995, and showed an increasing trend over the years. The results also indicated that introduction of ST156 in our region was preceded by the emergence of trimethoprim/sulfamethoxazole resistance and by the dissemination of ST162. In addition to the presence of successful international clones, a novel regional serotype 14 genotype (CC5401) has emerged in 1996.
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