In vitro phagocytic interaction between Trichomonas vaginalis isolates and bacteria

The phagocytic activity of 12 Trichomonas vaginalis isolates against both gram-positive bacteria (Staphylococcus aureus ATCC 25923, Lactobacillus spp.) and gram-negative bacteria (Enterobacter cloacae ATCC 13047, 5 strains of Escherichia coli, Pseudomonas aeruginosa ATCC 27853) was studied. Results showed that all the isolates were able to ingest Staphylococcus aureus to a variable degree, and almost all of them showed phagocytic activity against Pseudomonas aeruginosa. Furthermore, experiments with a restricted number of isolates of Trichomonas vaginalis showed that they phagocytized, often very effectively, human vaginal lactobacilli. Only in some cases was the addition of serum essential for bacteria ingestion. Phagocytic uptake of Escherichia coli and Enterobacter cloacae was not detectable under the experimental conditions used. It is concluded that phagocytosis may be involved in changes in vaginal biocenosis during the early stages of trichomoniasis.