How Probiotics may Kill Harmful Bacteria: The in vitro Activity against Some Haemolytic Strains

Haemolysis is the lysis of red blood cells (RBCs) and the subsequent release of their contents into surrounding fluid. Several pathogens, including Enterococcus faecalis, Klebsiella pneumoniae, Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa are able to cause haemolysis in vitro and in vivo. A vast body of scientific literature has demonstrated the ability of certain probiotic bacteria to antagonize grampositive and gram-negative strains by secreting soluble molecules named bacteriocins. Anyway, insufficient data is currently available in relation to haemolytic bacteria. Ten lactobacilli were selected for this in vitro study. The agar spot assay was employed to quantify any possible inhibition. The diameters of inhibition zones around the spots were measured. Our results showed that selected probiotics could exert a focused protective effect against pathogenic bacteria responsible for RBCs lysis at various extent. Further investigations will be needed to study the underlying molecules responsible for inhibition.