|Brito, Maria - EMBRAPA DAIRY CATTLE RES|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 17, 2006
Publication Date: July 28, 2007
Citation: Brito, M.A., Somkuti, G.A. 2006. Production of bacteriocins by bacterial isolates from dairy cattle (abstract). National Meeting of the American Dairy Association. Paper No. T8. Technical Abstract: A collection of 116 bacterial strains recovered from healthy cows in 41 dairy herds in Brazil was surveyed for the production of bacteriocins. The bacteria included 106 strains of staphylococci (87 coagulase positive and 19 coagulase negative) and 10 strains classified as streptococci. All cultures were grown in tryptic soy broth for 18 h at 37°C and cell-free supernatants were tested for antimicrobial activity against several target organisms by the agar diffusion method. Filtrates of 58 staphylococci and a culture identified as Streptococcus uberis showed strong activity against Listeria monocytogenes Scott, whereas a S. bovis isolate was active against S. agalactiae. Filtrates of 53 staphylococci also inhibited the growth of Staph. aureus strain 305, a major causative agent of bovine mastitis in the United States. Although plasmids were apparently absent in the streptococcal isolates, 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 either the A70 or A53 bacteriocin gene was checked by PCR techniques using forward and reverse primers 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 that corresponded 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.