LACTOBACILLUS CURVATUS PRODUCES A BACTERIOCIN-LIKE AGENT ACTIVE AGAINST GRAM-NEGATIVE PATHOGENIC BACTERIA

Isolates from fermented foods were screened for antimicrobial activity against gram‐negative bacteria. The most active isolate was identified as a Lactobacillus curvatus by biochemical analysis and ribotyping, and the isolate was designated as OSY‐HJC6. Lactobacillus curvatus OSY‐HJC6 was further tested for intracellular and extracellular production of antimicrobial agents. A reduction of > 8 log₁₀ cfu/mL was observed when cell suspensions of Salmonella enterica serovar Enteritidis and Escherichia coli O157:H7 were treated with equal volumes of Lb. curvatus culture supernatant. Gram‐positive bacteria were not sensitive to the culture supernatant, but antimicrobial activity was detected when the cell extract was tested against several gram‐positive and gram‐negative bacteria. Culture supernatant and cell extract retained the antimicrobial activity after heating at 60–100C for 10 min but not after protease treatment. The cell extract of Lb. curvatus retarded the growth of E. coli p220 in broth medium and food extracts (i.e., bacteriostatic action) but showed bactericidal activity against the bacterium in phosphate buffer.