Antimicrobial resistance patterns in Gardnerella vaginalis isolates from a South African pregnant population

Abstract

Background: Gardnerella vaginalis (G. vaginalis) is responsible for bacterial vaginosis (BV) pathogenicity. BV treatment includes broad-spectrum antibiotics, metronidazole, and clindamycin. However, in clinical settings, the increase in antimicrobial resistance has resulted in recurrent BV. This study aimed to determine susceptibility patterns of G. vaginalis isolates to various antibiotics. Additionally, the genetic diversity of isolates (G. vaginalis clades) was investigated and linked to antimicrobial resistance.

Methods: In total, n = 150 enrolled pregnant women, aged >/= 18 years, provided two self-collected vaginal swabs, which were used for BV diagnosis and G. vaginalis culture. Genetic diversity assessments of isolates were based on genetic differences in the tuf gene using clade-specific primers in quantitative polymerase chain reaction (qPCR). Antimicrobial susceptibility profiles were generated using the Sensititre™ Anaerobe MIC Plate (Thermo Fisher Scientific, Massachusetts, United States).

Results: In this study, 49.3% of the women were negative for BV, 28.7% were intermediate, and 22% were positive. Of the G. vaginalis isolates, 16 were successfully cultured from this population. The genotyping/clade polymerase chain reaction (PCR) detected three clades with frequencies of 100% for clade 1, 37.5% for clade 2, and 43.8% for clade 4. Multiple clades were found in 62.5% of isolates. Only 14 isolates were viable for susceptibility testing, of which 8/14 (57.1%) were susceptible to metronidazole (minimum inhibitory concentration [MIC] of </=  8 µg/ml) and 6/14 (42.9%) were resistant (MIC of >/= 32 µg/ml).

Conclusion: This study reported on the resistance patterns of clinical G. vaginalis isolates; high levels of metronidazole resistance were observed. Obtaining approval for the use of clindamycin and vancomycin for future treatment of BV should be considered in our current setting.