Trichomonas vaginalis somatic antigen effectively kills Staphylococcus spp. by damaging the cell wall, but has no effect on Escherichia coli or Salmonella enterica.

Antimicrobial resistance (AMR) is a critical global health threat, directly responsible for approximately 1.14 million deaths in 2021, underscoring the urgent need for novel antimicrobials. In this study, we examined somatic proteins from Trichomonas vaginalis (TvSP) for activity against selected bacterial strains. Gram-positive Staphylococcus aureus, S. warneri, and S. saprophyticus, and Gram-negative Escherichia coli and Salmonella enterica were tested. TvSP effectively killed all three Staphylococcus species but had no effect on E. coli or S. enterica, demonstrating selective activity against Gram-positive bacteria. Minimum inhibitory and bactericidal concentration (MIC/MBC) assays confirmed these findings (n = 3 independent biological replicates per strain). Kinetic assays indicated that TvSP activity against S. aureus was nearly concentration dependent. Scanning electron microscopy (SEM) revealed that TvSP causes cell-wall damage and lysis in Staphylococcus species. MALDI Q-TOF mass spectrometry of TvSP identified 462 peptides; preliminary findings suggest the presence of albumin (ALB)-like and lysyl endopeptidase (prpL)-like proteins potentially responsible for bactericidal activity. This is the first report of antibacterial activity in T. vaginalis somatic proteins, suggesting this protozoan parasite may employ antimicrobial mechanisms as part of its survival strategy in the urogenital microenvironment. As all assays used ATCC reference strains in vitro, the present findings should be regarded as proof-of-concept; future work will validate activity in clinical and drug-resistant isolates (notably MRSA) and characterise individual and synergistic contributions of the candidate peptides through chemical synthesis.