Antimicrobial susceptibility and genetic relationships among Streptococcus dysgalactiae subsp. equisimilis isolates in Rio de Janeiro

Abstract

Background: Streptococcus dysgalactiae subsp. equisimilis (SDSE) has been increasingly associated with several infectious diseases, ranging from pharyngitis to life-threatening conditions, such as necrotizing fasciitis and streptococcal toxic shock syndrome. However, its molecular epidemiology in some geographical areas remains unclear.

Methods: In this study, 44 isolates of SDSE, recovered from noninvasive infections (37) and from carriage (7), during 2008–2013, were submitted to antimicrobial susceptibility testing, emm typing and pulsed-field gel electrophoresis (PFGE) analysis.

Results: All isolates were susceptible to ceftriaxone, levofloxacin, penicillin G and vancomycin. Resistance rates to erythromycin was 18.2% and to clindamycin was 6.8%, while 38.7% of the isolates were tetracycline non-susceptible. Macrolide resistance phenotypes were M (5 isolates), iMLS_B (2) and cMLS_B (1), associated with mefA/E, ermA and ermB genotypes, respectively. Seventeen emm types with 21 subtypes were found, but 6 types (stG653.0, stC1400.0 with three subtypes, stC839.0, stC36.0 with two subtypes, stG480.0 and stG840.0) were detected in 70.4% of the isolates. Six new emm subtypes were identified (stC1400.12, stC1400.13, emm152.1, emm152.2, stG652.6 and stG6792.5). Twenty-five PFGE profiles were obtained from 39 isolates.

Conclusions: Congruence between both typing systems was observed, since the majority of isolates belonging to a given emm type clustered together by PFGE. Clones (at least 80% similarity) were also observed among isolates with different emm types, probably due to horizontal recombination of the emm gene. Erythromycin-resistant isolates harbored diverse emm genes and generated different PFGE profiles, showing a polyclonal dissemination of such characteristic among SDSE isolates.

Keywords:

• Antimicrobial resistance
• emm typing
• PFGE analysis
• Streptococcus dysgalactiae subsp. equisimilis

Acknowledgements

The authors thank Fleury Group for isolates donation and André V Barbosa, from DNA Sequencing Facility, Universidade Federal Fluminense.

Disclosure statement

There is no conflict of interest.

Funding information

This study was supported by Pró-Reitoria de Pesquisa, Pós-Graduação e Inovação, Universidade Federal Fluminense.