Arcanobacterium pyogenes, a commensal on the mucous membranes of many economically important animal species, is also a pathogen, causing abscesses of the skin, joints, and visceral organs as well as mastitis and abortion. In food animals, A. pyogenes is exposed to antimicrobial agents used for growth promotion, prophylaxis, and therapy, notably tylosin, a macrolide antibiotic used extensively for the prevention of liver abscessation in feedlot cattle in the United States. Of 48 A. pyogenes isolates, 11 (22.9%) exhibited inducible or constitutive resistance to tylosin (MIC of >128 g/ml). These isolates also exhibited resistance to other macrolide and lincosamide antibiotics, suggesting a macrolide-lincosamide resistance phenotype. Of the 11 resistant isolates, genomic DNA from nine hybridized to an erm(X)-specific probe. Cloning and nucleotide sequencing of the A. pyogenes erm(X) gene indicated that it was >95% similar to erm(X) genes from Corynebacterium and Propionibacterium spp. Eight of the erm(X)-containing A. pyogenes isolates exhibited inducible tylosin resistance, which was consistent with the presence of a putative leader peptide upstream of the erm(X) open reading frame. For at least one A. pyogenes isolate, 98-4277-2, erm(X) was present on a plasmid, pAP2, and was associated with the insertion sequence IS6100. pAP2 also carried genes encoding the repressor-regulated tetracycline efflux system determinant Tet 33. The repA gene from pAP2 was nonfunctional in Escherichia coli and at least one A. pyogenes isolate, suggesting that there may be host-encoded factors required for replication of this plasmid.The use of antimicrobial agents as feed additives for disease prophylaxis and growth promotion in the beef cattle industry is a common practice in the United States. One of the major targets is liver abscessation, which is second only to respiratory disease in terms of economic losses to cattle feedlots. Control of liver abscesses has primarily depended on the use of feed additives, such as the macrolide tylosin, chlortetracycline, and oxytetracycline (10, 26), with tylosin the most effective and commonly used feed additive (11). A study involving almost 7,000 feedlot cattle demonstrated that the use of tylosin as a feed additive reduced the incidence of liver abscessation by 73% and increased weight gain and feed conversion by 2.3 and 2.6%, respectively (G. J. Vogel and S. B. Laudert, abstract, J. Anim. Sci. 72[Supp. 1]:293, 1994). Correspondingly, tylosin use is extensive, with 42.3% of feedlot cattle receiving tylosin as a feed additive, primarily for the prevention of liver abscesses (26).Fusobacterium necrophorum is the primary etiological agent of bovine hepatic abscessation (18), but Arcanobacterium pyogenes is a synergistic pathogen, being found in 10 (9) to 90% (12) of abscesses. Interestingly, in cattle fed tylosin, the incidence of hepatic abscesses containing A. pyogenes increased from 10 to 53% (9).The resistance of A. pyogenes to tylosin has only recently been documented. In a survey of A. pyo...

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In our study, the SALT triage system was overall more accurate triage method than START at classi-fying patients, specifically in the delayed and immediate categories. In our field exercise, paramedic use of the START methodology yielded a higher rate of undertriage compared to the SALT classification.