مقالات پذیرفته شده در نهمین کنگره بین المللی زیست پزشکی
A Systematic Review of Antibiotic Resistance Patterns in Vaginal Lactobacillus Strains with Probiotic Potential
A Systematic Review of Antibiotic Resistance Patterns in Vaginal Lactobacillus Strains with Probiotic Potential
Maryam Tahmasbi,1,*
1. Department of Biology, Faculty of Science, Shahid Chamran University of Ahvaz, Iran
Introduction: Antibiotic resistance is recognized as one of the most pressing global health challenges, exerting profound consequences on healthcare systems worldwide. The extensive and, at times, irrational use of antimicrobial agents in both human and veterinary medicine has accelerated the dissemination of resistance determinants across bacterial populations. These genes, frequently transferred through mobile genetic elements such as plasmids and transposons, threaten the therapeutic efficacy of critical antibiotics and constitute a serious risk to public health.
Within this context, Lactobacillus species, which dominate the vaginal microbiota of healthy women, play a pivotal role in maintaining microbial balance and urogenital health. By producing lactic acid, hydrogen peroxide, and bacteriocins, these bacteria inhibit the growth of opportunistic pathogens and are widely considered natural probiotics. Nevertheless, recent evidence indicates that vaginal Lactobacillus strains may also harbor antibiotic resistance genes, raising concerns regarding their biosafety and clinical application. Consequently, systematic evaluation of resistance profiles is essential to ensure the safe and effective use of these microorganisms in both therapeutic and industrial settings.
Methods: This study was conducted as a systematic review of the literature published between 2017 and 2024 on antibiotic resistance in vaginal Lactobacillus strains with probiotic potential. Relevant articles were retrieved from reputable scientific databases, including PubMed, Scopus, and Google Scholar.
Inclusion criteria comprised studies that reported the isolation of Lactobacillus strains from healthy women, molecular identification of species through 16S rRNA sequencing, antibiotic susceptibility testing using standardized approaches (notably the E-test for determining minimum inhibitory concentrations, MICs), and PCR-based detection of resistance genes. Studies lacking reliable phenotypic or genotypic data were excluded from the analysis.
Results: The systematic review revealed that vaginal Lactobacillus isolates exhibit broadly consistent resistance and susceptibility profiles across diverse geographic regions. Overall, high levels of resistance have been documented against commonly used agents such as metronidazole, sulfonamides, tetracyclines, macrolides, and aminoglycosides. Resistance to metronidazole has been almost universally reported and is regarded as an intrinsic trait of the genus. Similarly, resistance to aminoglycosides including kanamycin and gentamicin is widespread, largely attributable to intrinsic mechanisms such as reduced membrane permeability and efflux activity.
At the genetic level, tetracycline resistance genes (tetM, tetK, tetW) and macrolide resistance genes (ermA, ermB, ermC) have been frequently detected in a substantial proportion of isolates. Importantly, these determinants have also been identified in strains phenotypically susceptible to the corresponding drugs, underscoring the potential for horizontal gene transfer to pathogenic bacteria.
Findings concerning vancomycin resistance have been heterogeneous. Some studies report resistance rates exceeding 40–50%, whereas others demonstrate considerable susceptibility. These discrepancies may reflect interspecies variation—for example, differences between L. johnsonii and L. crispatus—or methodological differences in susceptibility testing. This issue is clinically relevant, as vancomycin remains a cornerstone therapy for multidrug-resistant infections. Conversely, nearly all studies consistently report stable susceptibility of vaginal Lactobacillus isolates to ampicillin and chloramphenicol, suggesting that these drugs may serve as useful indicators when selecting safe strains for probiotic applications.
Collectively, the data highlight that while vaginal Lactobacillus strains contribute significantly to host protection, they simultaneously act as potential reservoirs of antibiotic resistance determinants, necessitating cautious evaluation.
Conclusion: The evidence synthesized in this review demonstrates that antibiotic resistance in vaginal Lactobacillus species follows a relatively stable and global pattern. Intrinsic resistance, such as that observed with metronidazole, may provide clinical advantages by allowing concurrent probiotic administration during antimicrobial therapy. In contrast, the presence of transferable resistance genes, particularly tet and erm, raises serious biosafety concerns due to the risk of dissemination to pathogenic microorganisms, thereby jeopardizing therapeutic efficacy.
A notable area of debate concerns vancomycin resistance, where findings remain inconsistent. While some investigations have reported widespread resistance, others describe marked susceptibility among certain species. This heterogeneity likely reflects both species-level differences and methodological variability. Given the importance of vancomycin as a last-resort antibiotic, continuous monitoring of resistance trends in vaginal Lactobacillus strains is imperative.
Recent recommendations emphasize that phenotypic assays alone are insufficient to guarantee probiotic safety. Comprehensive genetic characterization of resistance determinants should be incorporated as part of standardized screening prior to commercialization. Continuous surveillance and whole-genome analysis are therefore critical to ensuring both the biosafety and functional reliability of vaginal probiotics.