[Emergence of resistance to macrolides in Streptococcus pyogenes].
BACKGROUND
Diseases produced by Streptoccocus pyogenes are still a problem in Chile, as in the rest of the world. It exhibits in vitro susceptibility to different antimicrobials, but penicillin continues to be the treatment of choice. Alternative drugs have been developed for allergic patients, such as erythromycin, new macrolides and cephalosporins. Nevertheless, resistant strains are appearing due to the indiscriminate use of macrolides.


OBJECTIVE
To assess present antimicrobial susceptibility of S Pyogenes strains isolated from chilean patients.


METHODS
The susceptibility to penicillin, macrolides, clindamycin, cephalotin and vancomycin of 153 S Pyogenes strains, obtained from different health centers of the Metropolitan Region and isolated between 1996 and 1998, was assessed using the Kirby-Bauer method. Agar dilution minimal inhibitory concentration was then determined to macrolide resistant strains.


RESULTS
All strains were susceptible to penicillin. There was a 7.2% cross-resistance to macrolides.


CONCLUSIONS
These results confirm that S Pyogenes resistance to macrolides has increased considerably in the Metropolitan Region of Chile during the last years.
Vinagre
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Unidad de Microbiología Oriente, Facultad de Medicina, Universidad de Chile, Santiago de Chile. gtomasel@chilesat.net
Cifuentes
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M
Valdivieso
F
F
Ojeda
A
A
Prado
V
V
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018550:Cephalosporin Resistance; D002981:Clindamycin / Q000494:pharmacology; D004352:Drug Resistance, Microbial; D006801:Humans; D018942:Macrolides; D008826:Microbial Sensitivity Tests; D010403:Penicillin Resistance; D013297:Streptococcus pyogenes / Q000187:drug effects* / Q000302:isolation & purification; D020713:Vancomycin Resistance
D000900:Anti-Bacterial Agents; D018942:Macrolides; D002981:Clindamycin