CHARACTERISTICS OF COAGULASE-NEGATIVE STAPHYLOCOCCI ISOLATED FROM BOVINE INTRAMAMMARY INFECTIONS

Coagulase-negative Staphylococci (CNS) isolated from 86 different bovi ne intramammary infections (IMI) were investigated for their plasmid c ontent, antimicrobial resistance, and infection characteristics. Plasm ids were isolated from 30.2% of CNS. Number of plasmid bands ranged fr om 1 to 5. With the exception of tetracycline resistance, the presence of plasmids was not related to antibiotic resistance. Staphylococcus chromogenes was the CNS most frequently isolated from bovine IMI. Intr amammary infections were of long duration (mean = 222 days) and result ed in a low incidence of clinical mastitis (8.1% of IMI). The greatest percentage of IMI (55%) were detected in heifers with 57% of these IM I first detected at calving. A total of 56% of IMI originated during t he dry period in second lactation or older cows. The number of plasmid -positive CNS IMI was greater (P < 0.05) in multilactational cows when compared to heifers. The presence of a plasmid-positive CNS had no in fluence on duration of IMI, origin of IMI, clinical status of the infe ction, and elimination of IMI.