Adhesion Forces and Coaggregation between Vaginal Staphylococci and Lactobacilli

Jessica A Younes,Henny C Van Der Mei,Edwin Van Den Heuvel,Gregor Reid,Henk J Busscher,Daniel J Muller

doi:10.1371/journal.pone.0036917

Abstract

Urogenital infections are the most common ailments afflicting women. They are treated with dated antimicrobials whose efficacy is diminishing. The process of infection involves pathogen adhesion and displacement of indigenous Lactobacillus crispatus and Lactobacillus jensenii. An alternative therapeutic approach to antimicrobial therapy is to reestablish lactobacilli in this microbiome through probiotic administration. We hypothesized that lactobacilli displaying strong adhesion forces with pathogens would facilitate coaggregation between the two strains, ultimately explaining the elimination of pathogens seen in vivo. Using atomic force microscopy, we found that adhesion forces between lactobacilli and three virulent toxic shock syndrome toxin 1-producing Staphylococcus aureus strains, were significantly stronger (2.2–6.4 nN) than between staphylococcal pairs (2.2–3.4 nN), especially for the probiotic Lactobacillus reuteri RC-14 (4.0–6.4 nN) after 120 s of bond-strengthening. Moreover, stronger adhesion forces resulted in significantly larger coaggregates. Adhesion between the bacteria occurred instantly upon contact and matured within one to two minutes, demonstrating the potential for rapid anti-pathogen effects using a probiotic. Coaggregation is one of the recognized mechanisms through which lactobacilli can exert their probiotic effects to create a hostile micro-environment around a pathogen. With antimicrobial options fading, it therewith becomes increasingly important to identify lactobacilli that bind strongly with pathogens.

Highlights

Vaginal and bladder infections are among the most common causes of illness in females
High throughput sequencing studies on well-characterized cohorts have revealed that Lactobacillus iners, Lactobacillus crispatus, Lactobacillus gasseri, and Lactobacillus jensenii dominate the vaginal microbiota in healthy women, but L. crispatus and L. jensenii are unable to withstand the influx of pathogens leading to infection, and are more displaced from the normal microflora [1,2,3]
For the identical staphylococcal pair (Figure 2A), a maximal adhesion force of 25.8 nN was reached after 120 s, which is considerably smaller than the maximal adhesion force of 27.1 nN between the mixed Staphylococcus and the Lactobacillus strain (Figure 2B)

Summary

Introduction

Vaginal and bladder infections are among the most common causes of illness in females. High throughput sequencing studies on well-characterized cohorts have revealed that Lactobacillus iners, Lactobacillus crispatus, Lactobacillus gasseri, and Lactobacillus jensenii dominate the vaginal microbiota in healthy women, but L. crispatus and L. jensenii are unable to withstand the influx of pathogens leading to infection, and are more displaced from the normal microflora [1,2,3]. This inability to persist is believed to be related to their lack of adhesion to the vaginal surface, other microbes and their failure to adapt to the changing urogenital environment [4]. In vitro studies have shown that the administration of certain probiotic lactobacilli can lead to disruption of these pathogenic biofilms [9], but the actual mechanism of interference and biofilm penetration has not been studied

Methods

Results

Conclusion