The phenotypic and genotypic antibiotic susceptibility of vaginal Lactobacillus with potential probiotic properties isolated from healthy women in northern Iran

This study assesses the antibiotic susceptibility of vaginal Lactobacillus strains and provides data for determining the prevalence of certain antibiotic resistance genes in the new strains of lactobacilli serving as probiotics and selected from healthy women in northern Iran.

One hundred premenopausal non-pregnant women in the reproductive age range of 22-50 years participated in this study. The potential probiotic vaginal lactobacilli used in the study included Lactobacillus crispatus (34.2%), Lactobacillus gasseri (26.3%), Lactobacillus johnsonii (10.5%), Lactobacillus acidophilus (15.7%) and Lactobacillus jensenii (13.1%). The phenotypic antibiotic susceptibility of the strains was determined by E test and DNA extraction and PCR were performed to examine the antibiotic resistance genes.

38 potential probiotic vaginal lactobacilli were isolated. All the strains of lactobacilli were resistant to metronidazole and trimethoprim/sulfamethoxazole and all of the strains were susceptible to ampicillin and chloramphenicol antibiotics. The results showed that ermB, ermC, and ermA genes were observed in the strains of Lactobacillus acidophilus. Metronidazole resistance (nim) gene was also found in one strain of Lactobacillus crispatus and Lactobacillus johnsonii. The aminoglycoside resistance (aac6'-aph2") gene was observed in 8% of the strains. Also, tetM, tetK and tetW genes were found in more than 80% of the Lactobacillus strains.

The antimicrobial susceptibility of vaginal lactobacilli is an important criterion for establishing whether or not the organism is a probiotic. A high level of resistance to clinical antibiotics, such as metronidazole and aminoglycosides, was demonstrated. Antibiotic resistant genes also appeared widely in vaginal lactobacilli.