Phenotypes and genotypes of erythromycin-resistant Streptococcus pyogenes strains isolated from invasive and non-invasive infections from Mexico and the USA during 1999–2010

• Published in: International journal of infectious diseases 2012-03, Vol.16 (3), p.e178-e181
• Main Authors: Villaseñor-Sierra, Alberto, Katahira, Eva, Jaramillo-Valdivia, Abril N, Barajas-García, María de los Angeles, Bryant, Amy, Morfín-Otero, Rayo, Márquez-Díaz, Francisco, Tinoco, Juan Carlos, Sánchez-Corona, José, Stevens, Dennis L
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Aged; Aged, 80 and over; Anti-Bacterial Agents - pharmacology; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Ceftriaxone - pharmacology; Child; Child, Preschool; Clindamycin - pharmacology; Drug Resistance, Bacterial; Erythromycin - pharmacology; Genotype; Humans; Infant; Infectious Disease; Macrolides; Membrane Proteins - genetics; Membrane Proteins - metabolism; Methyltransferases - genetics; Methyltransferases - metabolism; Mexico; Mexico - epidemiology; Microbial Sensitivity Tests; Middle Aged; Penicillins - pharmacology; Phenotype; Phenotypes; Prevalence; Pulmonary/Respiratory; Resistance genes; Streptococcal Infections - epidemiology; Streptococcus pyogenes; Streptococcus pyogenes - drug effects; Streptococcus pyogenes - genetics; Streptococcus pyogenes - isolation & purification; United States - epidemiology; USA; Vancomycin - pharmacology; Young Adult
• ISSN: 1201-9712; 1878-3511
• DOI: 10.1016/j.ijid.2011.11.005

Summary Objective To compare the prevalence, phenotypes, and genes responsible for erythromycin resistance among Streptococcus pyogenes isolates from Mexico and the USA. Methods Eighty-nine invasive and 378 non-invasive isolates from Mexico, plus 148 invasive, 21 non-invasive, and five unclassified isolates from the USA were studied. Susceptibilities to penicillin, erythromycin, clindamycin, ceftriaxone, and vancomycin were evaluated according to Clinical and Laboratory Standards Institute (CLSI) standards. Phenotypes of erythromycin resistance were identified by triple disk test, and screening for mef A, erm TR, and erm B genes was carried out by PCR. Results All isolates were susceptible to penicillin, ceftriaxone, and vancomycin. Erythromycin resistance was found in 4.9% of Mexican strains and 5.2% of USA strains. Phenotypes in Mexican strains were 95% M and 5% cMLS; in strains from the USA, phenotypes were 33.3% iMLS, 33.3% iMLS-D, and 33.3% M. Erythromycin resistance genes in strains from Mexico were mef A (95%) and erm B (5%); USA strains harbored erm TR (56%), mef A (33%), and none (11%). In Mexico, all erythromycin-resistant strains were non-invasive, whereas 89% of strains from the USA were invasive. Conclusions Erythromycin resistance continues to exist at low levels in both Mexico and the USA, although the genetic mechanisms responsible differ between the two nations. These genetic differences may be related to the invasive character of the S. pyogenes isolated.