ISOLATION AND ANTIMICROBIAL SUSCEPTIBILITY OF ACTINOMYCES-PYOGENES RECOVERED FROM THE UTERUS OF DAIRY-COWS WITH RETAINED FETAL MEMBRANES AND POST PARTURIENT ENDOMETRITIS

The minimal inhibitory concentrations (MICs) of 14 antimicrobial agent s for Actinomyces pyogenes isolates recovered from the uterus of cows with retained fetal membranes (RFM) and post-parturient endometritis ( PPE) were determined. Cows with RFM received a course of intrauterine tetracycline therapy, whereas some cows with PPE received a similar tr eatment and others did not. Samples of uterine exudate were asepticall y collected at least 10 d after the last treatment. A profuse growth o f A. pyogenes was observed on blood agar plates inoculated with uterin e exudate from 72% of the 54 cows sampled. Differences were not observ ed in the type and characteristics of bacterial growth in the exudate of cows with PPE which were sampled before and after antibiotic treatm ent. The MIC of penicillin G, amoxycillin, cephalothin lincomycin and tylosin for 90% of the isolates was <0.5 mu g/ml; the corresponding va lue for streptomycin, oxytetracycline (OTC), chloramphenicol, norfor f loxacin and sulfadiazine/trimethoprim was > 10.0 mu g/ml. The MIC of O TC for 90% of the A. pyogenes isolates was >100 mu/ml. The susceptibil ity of 14 A. pyogenes isolates of bovine udder origin and 3 A. pyogene s ATCC isolates from the bovine udder and abscesses in sheep and swine to antibiotics was determined, for comparative purposes. Most of the isolates recovered from the uterus were resistant to OTC and sulpha/TM P whereas this was not the case for isolates recovered from other sour ces