STAPHYLOCOCCOSIS OF TURKEYS .6. DEVELOPMENT OF PENICILLIN RESISTANCE IN AN INTERFERING STRAIN OF STAPHYLOCOCCUS-EPIDERMIDIS

Staphylococcus epidermidis strain 115, used as an interfering agent to help reduce the incidence of staphylococcosis in turkeys, was convert ed into a penicillin- and chloramphenicol-resistant strain designated 115R. This was accomplished by introducing a plasmid carrying the beta -lactamase (penicillinase) and chloramphenicol-resistance genes into S . epidermidis 115 by electroporation. The resultant strain, 115R, was an efficient producer of beta-lactamase and had marked increased resis tance to penicillin and chloramphenicol. A beta-lactamase DNA probe wa s used to confirm the presence of the beta-lactamase gene in strain 11 5R. S. epidermidis strain 115R retained the characteristics of tissue adherence, bacteriocin production, and non-virulence that were present in the original non-transformed strain 115, and in addition should th eoretically remain colonized in poults following treatment with penici llin.