Aggregation-promoting factor in human vaginal Lactobacillus strains

A total of 60 Lactobacillus sp. strains were examined for expression of auto-aggregation and cell surface hydrophobicity. Isolates were obtained from the vagina of healthy women (n = 20). The results obtained showed that the occurrence of cell surface hydrophobicity correlated with auto-aggregative activity in 12 homofermentative Lactobacillus sp. strains. The aggregation mechanism was mediated by the presence of an aggregation promoting factor (APF) in one Lactobacillus sp. strain, HV 142. APF was confirmed by DNA hybridisation with a 1.3 kb PstI DNA fragment of recombinant plasmid pFDS containing the reading open frame of the APF gene derived from Lactobacillus plantarum 4B2. Coaggregation activity was seen in three strains of auto-aggregative human vaginal lactobacilli and five strains of P-fimbriated uropathogenic Escherichia coli. Moreover, one of four Lactobacillus sp. strains (HV 389) aggregated with two of five E. coli tested. These results suggest that APF producing lactobacilli could represent a further mechanism in the interaction of commensal microflora with strains of uropathogenic E. coli.