ANTIMICROBIAL SUBSTANCES PRODUCED BY STAPHYLOCOCCUS-AUREUS STRAINS ISOLATED FROM CATTLE IN BRAZIL

Among 46 isolates of Staphylococcus aureus obtained from cattle in the State of Paraiba, Brazil, four were shown to produce antimicrobial su bstances (AMS). The two best AMS producers carried single plasmids of about 8.0 kbp and 50 kbp, respectively, which were designated pRJ34 an d pRJ35. Curing experiments and molecular analysis associated the AMS production with the presence of these plasmids in the cells. The bioch emical properties exhibited by the AMS suggested that they might be ba cteriocins (Bac). The bacteriocin encoded by pRJ34 showed properties i dentical to those of the bacteriocins encoded by other small staphyloc occal Bac plasmids. However, the bacteriocin encoded by the large plas mid pRJ35 has shown some properties which distinguish it from the othe r bacteriocins of Staph. aureus described so far, suggesting it may be a new member of the staphylococcal bacteriocin family.