Screening and antimicrobial activity evaluation of antimicrobial Lactobacillus strains from vagina

Abstract:

[Objective] To develop probiotics for gynecological inflammation, we isolated and screened out Lactobacillus with antimicrobial and probiotic properties from the vagina of healthy women. [Methods] The plate streaking method was employed to isolate the Lactobacillus strains from vaginal samples, and the isolates were then identified based on morphological and 16S rRNA gene sequencing evidence. The growth and adhesion of the five strains were characterized. The Oxford cup method with Escherichia coli and Staphylococcus aureus as indicator strains was employed to assess the antimicrobial activities of the strains. The microtiter plate method was used to measure the inhibitory effects of the strains on Candida albicans. The antimicrobial components were explored by organic acid elimination and hydrogen peroxide elimination methods. [Results] Five strains of Lactobacillus were isolated, including three strains (Q2.1, BHC04, and Q8.5) of Lactobacillus crispatus and two strains (Q6.3 and BHG05) of Lactobacillus gasseri. All the five strains of Lactobacillus had strong growth and high acid production. Strains Q2.1, BHC04, and BHG05 had a short delay period and reached a plateau growth stage after 20 h, and strains BHG05, Q6.3, and Q8.5 had high acid production, with the culture medium finally reaching pH 3.80-4.03. The adhesion capacity (hydrophobicity, self-agglutination rate, and co-agglutination rate with pathogens) of L. crispatus Q2.1, BHC04, and Q8.5 was significantly higher than that of the positive control strain, L. delbrueckii DM8909. The inhibitory effects of the five strains on E. coli, S. aureus, and C. albicans were stronger than those of the positive control (nisin). Strains BHC04, BHG05, and Q8.5 showcased stronger inhibitory effects on E. coli than DM8909. The inhibitory effect of BHG05 on C. albicans was significantly stronger than that of DM8909, with the inhibition rate reaching up to (73.14±0.14)%. The inhibitory effects of BHC04 and Q8.5 on C. albicans were not significantly different from that of DM8909, with the inhibition rates reaching up to (72.80±0.30)% and (72.93±0.10)%, respectively. According to the results above, we selected BHC04 and BHG05 as high quality strains with antimicrobial potential. The five strains produced organic acids and hydrogen peroxide to exert antimicrobial effects. [Conclusion] Two strains of Lactobacillus with antimicrobial effects and excellent probiotic properties were screened out. They can be used as candidate strains of antimicrobial probiotics for the prevention and treatment of gynecological inflammation caused by E. coli, S. aureus, and C. albicans.