THE ANTIBACTERIAL ACTIVITY AND SENSITIVITY OF S. BOVIS STRAINS ISOLATED FROM THE RUMEN OF CATTLE

Authors: MANTOVANI, H - CORNELL UNIVERSITY; KAM, D - CORNELL UNIVERSITY; HA, J - CORNELL UNIVERSITY; Russell, James

Submitted to: Federation of European Microbiological Societies Microbiology Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/2001
Publication Date: 9/1/2001
Citation: MANTOVANI, H.C., KAM, D.K., HA, J.K., RUSSELL, J.B. THE ANTIBACTERIAL ACTIVITY AND SENSITIVITY OF S. BOVIS STRAINS ISOLATED FROM THE RUMEN OF CATTLE. FEDERATION OF EUROPEAN MICROBIOLOGICAL SOCIETIES MICROBIOLOGY ECOLOGY. 2001.

Interpretive Summary: Cattle in the U.S. are often fed antibiotics, but the widespread use of antibiotics in animal feed has been criticized. Antibiotics are primarily targeted against gram-positive gut bacteria. Gram-positive ruminal bacteria produce large amounts of hydrogen a precursor of methane, ammonia, a wasteful end-product of amino acid degradation, and lactic acid, an acid that causes ruminal acidosis, ruminal ulcers, founder and even death of th animal. Some bacteria produce peptides (bacteriocins) that can inhibit gram-positive bacteria, and bacteriocins have been proposed as an alternative to antibiotics. In this manuscript we describe the bacteriocin production and sensitivity of S. bovis strains isolated from the rumen of cattle. Some of the bacteriocins were not highly effective, and resistance was often a problem. The bacteriocin of S. bovis HC5 was most effective and little resistance was observed. Research on bacteriocins has the potential to decrease the need for antibiotic in animal feed.

Technical Abstract: Approximately 50% of S. bovis isolates (n = 90) from cattle fed hay or grain-based diets inhibited the growth of S. bovis JB1 in agar overlays. When repetitive DNA (BOX) sequences were amplified by PCR, the bacteriocin-producing (bac+) strains could be organized into 16 phylogenetic groups, but the similarity indexes (UPGAMA) were as low as 40%. Based on these results, bacteriocin production was not a phylogenetically conserved trait. PCR analyses indicated that none of the bac+ strains had the gene for bovicin 255, a bacteriocin produced by Streptococcus gallolyticus LRC0255, and many of the bac+ isolates were sensitive to bovicin 255. Bovicin 255 decreased the viability of many fresh isolates, but it never killed all of the cells. Cells that survived bovicin 255 and were transferred a second time became resistant (less than or equal to 2 log reduction in viability). The isolates were more sensitive to the bacteriocin of S. bovis HC5 than bovicin 255, the initial average decrease in viability was approximately 3 logs greater (4.8 +/- 2.7 versus 1.8 +/- 2.1, respectively, P < 0.001), and the HC5-sensitive strains did not adapt. Sixteen of the bac+ isolates were highly resistant to S. bovis HC5 (less than or equal to 1 log reduction in viability), and BOX PCR indicated that only 5 of them had the same BOX pattern as S. bovis HC5. The remaining bac+, HC5-resistant isolates (n=11) had distinctly different BOX patterns and were not always highly resistant to bovicin 255. Based on these results, the rumen has a highly diverse population of bac+ S. bovis strains, and this population can co-exist with bac- strains in the rumen.