Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/27/2010
Publication Date: 1/1/2011
Citation: Brito, M.A., Somkuti, G.A., Renye Jr, J.A. 2011. Production of antilisterial bacteriocins by staphylococci isolated from bovine milk. Journal of Dairy Science. 94:1194-1200.
Interpretive Summary: The control of staphylococci in dairy herds is important because these bacteria may cause infections and also outbreaks of food borne disease. However, some strains of staphylococci recovered from cattle produce natural antimicrobial products with high activity against bacteria causing milk-borne diseases such as Listeria and other staphylococci. Our survey of over 100 strains of staphylococci isolated from dairy herds in Brazil showed that close to 50 percent of cultures produced known or possibly novel antimicrobials that inhibited the growth of Listeria and staphyloccous cultures that cause udder infections in cows. The association of such staphylococci with dairy herds may be considered beneficial as they protect the health of animals by competitively inhibiting the growth of other infection causing staphylococci. In some cases it may be possible to transfer this protective property to food grade bacteria that in turn may serve as natural biopreservatives of food systems controlling bacterial infections and leading to improved margins of food safety.
Technical Abstract: A collection of 111 staphylococcal isolates recovered from healthy cows in 41 dairy herds in Brazil was surveyed for the production of bacteriocins. The group included 94 coagulase positive and 17 coagulase negative strains of staphylococci. All cultures were grown in tryptic soy broth for 18 h at 37 deg C and cell-free supernatants were tested for antimicrobial activity against several target organisms by the agar diffusion method. Filtrates of 57 staphylococci showed strong activity against Listeria monocytogenes Scott A and 52 isolates also inhibited the growth of Stapylococcus aureus Newbould 305, a major causative agent of bovine mastitis in the United States. The plasmid profiles of staphylococci invariably included an 8 kb plasmid. Staphylococcal isolates were tested for the production of aureocins A70 and A53, two bacteriocins of coagulase positive staphylococci known to be associated with 8 kb and 10.2 kb plasmids, respectively. The presence of the A70 or A53 bacteriocin gene was checked by PCR techniques using primers based on nucleotide sequences flanking the structural gene of each bacteriocin. Agarose gel analysis of amplified PCR products of plasmid templates from all 58 isolates showed only a 525 bp fragment corresponding to the structural gene of the bacteriocin aureocin A70. The results indicated that the apparently widespread association of A70-producing staphylococci with healthy cows in Brazil may be beneficial in controlling undesirable bacteria in dairy herds.