198 Lactic acid bacteria (LAB) were isolated from Iranian milk samples. Almost all isolated
LAB showed inhibitory activity towards E. coli and S. aureus as Gram negative and Gram
positive indicators, respectively. No role was observed for hydrogen peroxide in the activity of
all isolated strains while organic acids proved a prominent role in all detected inhibitory
activities. Within isolated LAB, four strains represented the inhibitory activity against S. aureus
based on the production of bacteriocin-like inhibitory substances (BLIS). Inactivation of the
activity by proteolytic enzymes demonstrated the proteinaceous nature of the antimicrobial
compounds. The selected producers were identified as L. lactis, E. faecium 1, E. hirae and E.
faecium 2 based on biochemical tests according to Bergy's manual of systematic bacteriology.
L. lactis had the highest Minimum Inhibitory Concentration (320 IU/ml) and showed
bacteriostatic mode of activity towards the indicator bacteria.