Submitted to: American Society for Microbiology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/2/2003
Publication Date: 5/24/2003
Citation: Mantovani, H.C., Russell, J.B. 2003. Inhibition of listeria monocytogenes by bovicin hc5, a bacteriocin produced by streptococcus bovis hc5.. American Society for Microbiology Annual Meeting. p. 432.
Technical Abstract: Cattle can be infected by listeria if they consume contaminated silage. A bacteriocin from Streptococcus bovis HC5 (bovicin HC5) inhibited ten strains of Listeria monocytogenes that had been isolated from plant materials, soil, contaminated silage and infected cattle. Growth experiments indicated that all of the L. monocytogenes strains were inhibited by 100 AU of bovicin HC5 per ml, and two of the strains were inhibited by only 50 AU per ml. L. monocytogenes cultures that were transferred with sub-lethal doses (12.5 AU per ml) could be adapted in stepwise fashion to higher doses of bovicin HC5. However, even 'adapted' cultures did not grow if 400 AU per ml was added. 'Adapted' cultures that were treated with 100 AU per ml also grew slower and had lower final optical densities than untreated controls. The effect of bovicin HC5 on L. monocytogenes was bactericidal, and the viability of the most resistant strain (CUSI-163/94) decreased 5 to 7 logs after only 2 h of exposure. L. monocytogenes cells that were incubated in MES buffer (100 mM 2-[N-morpholino] ethanesulfonic acid, 10 mM MgSO4 . 7H2O, 10 mM KCl) containing glucose (2 mg per ml) had approximately 1500 nmols intracellular potassium mg protein-1 at pH values ranging from 7.0 to 5.0. Bovicin HC5 catalyzed a nearly complete efflux of potassium in 15 min but only if the pH was less than 6.0. When the pH was greater than 6.0, the cells maintained their potassium pool. Cultures that were grown in BHI (brain heart infusion) medium with 6 mg glucose per ml had a final pH of 4.6, and these acid 'adapted' cells were as sensitive to bovicin HC5 as those that were grown with less glucose (2 mg per ml), additional phosphate buffer (100 mM) and had a final pH of 6.3. These results support the idea that bovicin HC5 could be effective in counteracting listeria in contaminated silages.