Antibacterial, Sperm Immobilization and Spermicidal Activities of Bacteriocins Produced by Vaginal Lactobacilli

Abstract

Lactobacillus bacteriocin is an interesting compound playing a dual spermicidal/bacteriocidal role so that this compound can be developed as an agent that can be able to replace the unsafety chemical, nonoxynol-9. The present study aimed to investigate the antibacterial, sperm immobilization, and spermicidal activities of bacteriocins that were produced from vaginal lactobacilli. Nine of 932 cell-free supernatants exhibited potent antibacterial activities against the standard bacterial strains and the pathogenic Niesseria gonorrhoeae. Ion exchange-purified bacteriocins B84/7 F2 demonstrated the lowest minimum inhibitory concentration and the highest bacteriocin activity against the tested pathogens. The isolate B84/7 was then identified as Lactobacillus crispatus. The rapid killing activity was exerted within 15 minutes after being exposed to the tested bacteria, and also significantly inhibited the exponential growth of the tested pathogen. Among 48 semen of volunteers, the median time of sperm immobilization of ion-exchange purified B84/7 F2 bacteriocin (18.70 mg/mL) was 30.42 seconds. Within 60 seconds, spermicidal activities of the partial fractionated and ion-exchange purified B84/7 F2 at the undiluted concentration were 83.67 and 80.75%, respectively. Its activity will significantly decline at pH > 8.0 or after being treated with alkaline and proteolytic enzymes. Two peptide bands of this bacteriocin were 7.08, and 8.81 kDa after being detected on a tricine SDS-PAGE gel. In-depth characteristics of this bacteriocin should be further investigated regarding the mode of action and purification. These findings can be applied to develop as the protecting agent of sexually transmitted infections especially gonorrhea, and unwanted pregnancy.