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 agents 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 treatment and others did not. Samples of uterine exudate were aseptically collected at least 10 d after the last treatment. A profuse growth of A. pyogenes was observed on blood agar plates inoculated with uterine exudate from 72% of the 54 cows sampled. Differences were not observed in the type and characteristics of bacterial growth in the exudate of cows with PPE which were sampled before and after antibiotic treatment. The MIC of penicillin G, amoxycillin, cephalothin lincomycin and tylosin for 90% of the isolates was <0.5 mu g/ml; the corresponding value for streptomycin, oxytetracycline (OTC), chloramphenicol, norfor floxacin and sulfadiazine/trimethoprim was > 10.0 mu g/ml. The MIC of OTC for 90% of the A. pyogenes isolates was >100 mu/ml. The susceptibility of 14 A. pyogenes isolates of bovine udder origin and 3 A. pyogenes 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/TMP whereas this was not the case for isolates recovered from other sources