[Resistance phenotypes and genotypes of Streptococcus pyogenes clinical isolates in Chile over a 10-year period].
BACKGROUND
Macrolide and lincosamide resistance in Streptococcus pyogenes is due to the acquisition of mef, ermB and ermA genes, which confer different resistance phenotypes, namely M, MLSBconstitutive and MLSBinducible respectively. The last report of resistance in Chile was done in the period 1990-1998, in which resistance to macrolides was 5.4%, with M phenotype as the predominant one.


OBJECTIVE
To characterize the evolution of erythromycin and clindamycin resistance and their associated genes in S. pyogenes strains isolated from patients with invasive and non-invasive infections in the period 1996 to 2005.


METHODS
Resistance to erythromycin and clindamycin was determined in 1,282 clinical isolates using the disk diffusion test. Resistant isolates were analyzed by polymerase chain reaction (PCR) for the presence of the above mentioned resistance genes.


RESULTS
Global resistance to erythromycin and clindamycin was 3.5 and 0.7% respectively. Eighty percent of the resistant strains possessed the M. phenotype.


CONCLUSIONS
Resistance levels of S. pyogenes have decreased in Chile in the last years. Most resistant strains have M phenotype in contrast to many countries in which the MLSB constitutive phenotype is the predominant one.
Laboratorio de Microbiología, Departamento de Laboratorios Clínicos, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.
Carlos
C
Rodríguez
Pablo
P
Rojas
Aniela
A
Wozniak
Alexis M
AM
Kalergis
Inés
I
Cerón
Ingrid
I
Riedel
Juan C
JC
Román
Luis A
LA
Villarroel
Ximena
X
Berríos
Luis
L
Bavestrello
Patricia
P
García
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D002677:Chile / Q000453:epidemiology; D002981:Clindamycin / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial / Q000187:drug effects / Q000235:genetics*; D004917:Erythromycin / Q000494:pharmacology*; D005838:Genotype; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics; D008780:Methyltransferases / Q000235:genetics; D010612:Pharyngitis / Q000188:drug therapy / Q000382:microbiology*; D010641:Phenotype; D016012:Poisson Distribution; D013290:Streptococcal Infections / Q000188:drug therapy / Q000382:microbiology*; D013297:Streptococcus pyogenes / Q000187:drug effects* / Q000235:genetics
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C117866:MefA protein, Streptococcus; D008565:Membrane Proteins; C551474:ermB protein, Streptococcus pyogenes; D002981:Clindamycin; D004917:Erythromycin; D008780:Methyltransferases; C431709:ErmA protein, Bacteria