BIOCHEMICAL AND BIOLOGICAL CHARACTERIZATIONS AND RIBOTYPING OF ACTINOMYCES-PYOGENES AND ACTINOMYCES PYOGENES-LIKE ORGANISMS FROM LIVER-ABSCESSES IN CATTLE

Actinomyces pyogenes is the second most frequently encountered pathoge n, next only to Fusobacterium necrophorum, in liver abscesses of feedl ot cattle. Ninety-one isolates, presumptively identified as A. pyogene s, isolated from liver abscesses of cattle were studied. Biochemical c haracteristics determined by the API 20 Strep kit were similar to thos e reported previously for A. progenes isolated from other infections, except that 18% of isolates hydrolyzed esculin. Nine isolates that res embled A, pyogenes in morphology and in certain biochemical characteri stics, but fermented mannitol and/or raffinose, were called A. pyogene s-like (APL) organisms. The five antimicrobial agents, bacitracin, chl ortetracycline, oxytetracycline, tylosin, and virginiamycin were inhib itory to all strains of A. pyogenes and APLs, Generally, APL organisms had higher mean hemolytic and leukotoxic activities than A. pyogenes. All isolates of A. pyogenes and APLs produced proteases and neuramini dases, Ribotyping with endonucleases, including BstEII, ClaI, EcoRI, E coRV, HaeIII, MboI, PvuII, SalI, and SmaI alone or in combinations, sh owed considerable genetic heterogeneity in both A. pyogenes and APLs. No specific ribopattern characteristic of each group was observed with any of the endonucleases used. The origin of A. pyogenes and APLs and the relative importance of APLs in causing liver abscesses in feedlot cattle are not known. (C) 1998 Elsevier Science B.V.