The prevalence of <i>optrA</i> -carrying <i>Enterococci</i> in the vaginal micro-ecology of pregnant women in late pregnancy

The colonization of <i>Enterococcus</i> in the female vagina leads to neonatal and pediatric enterococcal septicemia. Linezolid (LZD) is a kind of mainstream drug for treating multidrug-resistant Gram-positive infections. <i>OptrA</i> is the main LZD-resistance gene at <i>Enterococci</i> in human isolates. It is essential to explore the prevalence of <i>optrA</i>-carrying <i>Enterococcus</i> in vaginal secretions of late pregnant women and the drug resistance of <i>optrA</i>. From May to June 2023, this study recruited 340 volunteers in late pregnancy (35-40 weeks of pregnancy) to provide non-repetitive vaginal discharge samples. Luria-Bertani broth and florfenicol (10 µg/mL) were used to enrich bacteria. <i>Enterococci</i> was identified through time-of-flight mass spectrometry. Additionally, antimicrobial susceptibility, polymerase chain reaction, and next-generation sequencing assays were applied to this study. Fifty-four <i>optrA</i>-carrying <i>Enterococcus</i> strains were obtained, the proportion of the whole vagina of late pregnant women was 15.88% (54 out of 340), and <i>Enterococcus faecalis</i> account the highest proportion. All <i>optrA</i>-carrying <i>Enterococcus</i> were resistant to at least three drugs. Tetracycline, chloramphenicol, erythromycin, and LZD have higher bacterial resistance rates. Genetic environment analysis revealed that IS<i>1216E</i>, <i>fexA</i>, and <i>erm</i>(A) may synergistically exert multidrug resistance with <i>optrA</i>. It is necessary to strengthen the surveillance of <i>optrA</i>-carrying <i>Enterococcus</i> in pregnant women. This study provides scientific support for controlling hospital infections and managing antibiotic-resistant bacteria, and provides a scientific basis for rational clinical medication.IMPORTANCEThe disruption of cervicovaginal microbiota homeostasis is considered a key factor in causing imbalance in the microenvironment, leading to inflammation, transmission of infections, and illness. <i>Enterococcus</i> is considered a major cause of healthcare-related infections globally. It has resistance to multiple antimicrobial drugs, which pose significant challenges for clinical treatment. Therefore, it is crucial to assess the prevalence of <i>optrA</i>-carrying <i>Enterococcus</i> in vaginal secretions of late pregnant women and the drug resistance of <i>optrA</i>. This study detected 15.88% of <i>optrA</i>-carried <i>Enterococci</i> in 340 pregnant women. Furthermore, we found that <i>optrA</i>-carrying <i>Enterococcus</i> strains are highly resistant to tetracycline, chloramphenicol, erythromycin, and Linezolid. Additionally, genetic environment analysis revealed that <i>IS1216E</i>, <i>fexA</i>, and <i>erm</i>(A) may synergistically exert multidrug resistance with <i>optrA</i>. This study provides scientific support for controlling hospital infections and managing antibiotic-resistant bacteria and provides a scientific basis for rational clinical medication.