Antimicrobial resistance profiles and genetic characterisation of macrolide resistant isolates of Streptococcus agalactiae

ABSTRACT

In this study, 100 clinical isolates of Streptococcus agalactiae recovered from genitourinary tract specimens of non-pregnant individuals living in Rio de Janeiro were submitted for antimicrobial susceptibility testing, detection of macrolide resistance genes and evaluation of the genetic diversity of erythromycin-resistant isolates. By agar diffusion method, all isolates were susceptible to ceftazidime, penicillin and vancomycin. Isolates were resistant to levofloxacin (1 percent), clindamycin (5 percent), erythromycin (11 percent) and tetracycline (83 percent) and were intermediated to erythromycin (4 percent) and tetracycline (6 percent). Erythromycin-resistant and intermediated isolates presented the following phenotypes M (n = 3), constitutive macrolide-lincosamide-streptogramin B (MLS B, n = 5) and inductive MLS B (n = 7). Determinants of macrolide resistance genes, erm and mef, were detected in isolates presenting MLS B and M phenotypes, respectively. Randomly amplified polymorphic DNA profiles of erythromycin-resistant isolates were clustered into two major groups of similarity.