The emergence of Streptococcus pneumoniae resistant to macrolide antimicrobial agents: a 6-year population-based assessment.
From 1994 through 1999, the available isolates (4148 isolates) from active population-based surveillance of invasive pneumococcal disease in metropolitan Atlanta were serotyped and were tested for antimicrobial susceptibility. Macrolide-resistant isolates were studied for the presence of ermAM (a ribosomal methylase gene), mefE (a macrolide efflux gene), and tetM (the class M tetracycline resistance gene). Macrolide resistance increased from 16% of all invasive isolates in 1994 to 32% in 1999. Of the macrolide-resistant pneumococcal isolates studied, 99% contained genomic copies of mefE or ermAM. Isolates with ermAM were mainly serotypes 6B, 23F, 14, or 19F and contained tetM; mefE-associated isolates were predominantly serotypes 14, 6A, or 19F, and most did not contain tetM. The frequency of the ermAM-mediated phenotype in invasive Streptococcus pneumoniae remained stable over the 6-year surveillance. However, the mefE-mediated phenotype increased from 9% in 1994 to 26% of all isolates in 1999 and was noted in new serotypes. By 1999, 93% of the mefE-containing strains had minimum inhibitory concentrations >/=8 microgram/mL. Dissemination of the mefE determinant accounted for the rapid increase in the rate of macrolide resistance in our S. pneumoniae population.
Gay
K
K
Departments of Medicine and of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, USA. kgay@emory.edu
Baughman
W
W
Miller
Y
Y
Jackson
D
D
Whitney
C G
CG
Schuchat
A
A
Farley
M M
MM
Tenover
F
F
Stephens
D S
DS
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D004917:Erythromycin / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000235:genetics; D013997:Time Factors
D000900:Anti-Bacterial Agents; D004917:Erythromycin