Competitive inhibition bacteria of bovine origin against Salmonella serovars

Abstract

Studies were conducted to isolate bacteria inhibitory to Salmonella enterica serovar Typhimurium definitive type (DT) 104 in vitro from cattle not carrying Salmonella and to determine the inhibitory activity of the isolated bacteria through competitive growth in cattle feces artificially contaminated with Salmonella Typhimurium DT104 and S. enterica serovar Newport. Fecal samples (108) were obtained from dairy and beef cows. S. enterica serovars were isolated from 9.25% of the samples and included Salmonella Newport (4), Salmonella Bareilly (1), Salmonella Mbandaka (1), Salmonella Montevideo (1), Salmonella Meleagridis (1), and monophasic Salmonella (2). All four Salmonella Newport isolates were resistant to at least nine antibiotics. Of 1,097 bacterial isolates from cattle feces screened, 30 were inhibitory to Salmonella Typhimurium DT104 in vitro. The inhibitory isolates included 22 Escherichia coli, 6 Bacillus circulans, 1 Serratia fonticola, and 1 Enterobacter cloacae. Typing by pulsed-field gel electrophoresis showed 17 distinguishable profiles among the 22 E. coli. Competitive inhibition isolates did not significantly reduce Salmonella Typhimurium DT104 during 21 days of storage at 37°C in cattle feces. B. circulans (105 CFU/g of inoculum) significantly reduced Salmonella Newport on days 3 and 5 and on day 21 with 108 CFU/g of inoculum at 37°C. At 21°C, significant reductions of Salmonella Typhimurium DT104 occurred with 108 CPU of gram-negative competitive inhibition bacteria per g and 105 CPU of B. circulans per g on day 5 only. No significant reductions were observed with Salmonella Newport at 21°C. The 25 competitive inhibition bacteria identified in this study offer a first step in identifying competitive inhibition bacteria that may reduce the level of intestinal carriage and fecal shedding of Salmonella Typhimurium DT104 and Salmonella Newport in cattle. Copyright ©, International Association for Food Protection.