Molecular epidemiology of Streptococcus agalactiae recovered from significant bacteriuria

Abstract

Background: Streptococcus agalactiae has been implicated in urinary tract infections, but the molecular epidemiology of such infections is poorly characterized. Methods: In this study, 194 isolates recovered from significant bacteriuria of non-pregnant individuals were submitted to antimicrobial susceptibility testing, molecular characterization of macrolide resistance, PCR-based capsular typing and analysis of genetic diversity by pulsed-field gel electrophoresis (PFGE). Results: By disk diffusion, all isolates were susceptible to ceftriaxone, levofloxacin, penicillin G and vancomycin; 87.6% and 9.3% of isolates were non-susceptible to tetracycline and clindamycin, respectively. The minimum inhibitory concentration (MIC) confirmed that 11.3% of isolates were resistant to erythromycin. Macrolide resistance determinants were iMLS_B (n = 9), cMLS_B (n = 9) and M (n = 4), associated with ermA, ermB and mefA/E. Predominant capsular types were V, Ia, II and III. No significant association was observed between any capsular type and the occurrence of pyuria. However, type III was associated with erythromycin resistance, while type II was associated with erythromycin-susceptible isolates. Distinct PFGE profiles were observed among different types, but identical profiles were found among erythromycin-susceptible and -resistant isolates of the same type. Conclusion: A variety of capsular and PFGE types are involved in significant bacteriuria. Although capsular types found here are prevalent in different infections, the frequency of each type seems to be unique. Erythromycin resistance is due to polyclonal origin instead of the expansion of few clones of S. agalactiae.

Keywords::

• Antimicrobial resistance
• capsular typing
• pulsed-field gel electrophoresis
• Streptococcus agalactiae
• urinary tract infection

Acknowledgements

The authors thank the Fleury Group for donation of isolates and Pró Reitoria de Pesquisa, Pós-Graduação e Inovação, Universidade Federal Fluminense, for financial support.

Declaration of interest: This study was supported by the Pró-Reitoria de Pesquisa, Pós-Graduação e Inovação, Universidade Federal Fluminense. The authors report no conflicts of interest.