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Antimicrobial susceptibility of Histophilus somni isolated from clinically affected cattle in Australia

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Goldspink, L. K., Mollinger, J. L., Barnes, T. S., Groves, M., Mahony, T. J. and Gibson, J. S. (2015) Antimicrobial susceptibility of Histophilus somni isolated from clinically affected cattle in Australia. The Veterinary Journal, 203 (2). p. 239. ISSN 10900233

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Article Link: http://dx.doi.org/10.1016/j.tvjl.2014.12.008

Publisher URL: http://www.sciencedirect.com/science/article/pii/S1090023314005048


This study investigated antimicrobial resistance traits, clonal relationships and epidemiology of Histophilus somni isolated from clinically affected cattle in Queensland and New South Wales, Australia. Isolates (n = 53) were subjected to antimicrobial susceptibility testing against six antimicrobial agents (ceftiofur, enrofloxacin, florfenicol, tetracycline, tilmicosin and tulathromycin) using disc diffusion and minimum inhibitory concentration (MIC) assays. Clonal relationships were assessed using repetitive sequence PCR and descriptive epidemiological analysis was performed. The H. somni isolates appeared to be geographically clonal, with 27/53 (47%) isolates grouping in one cluster from one Australian state. On the basis of disc diffusion, 34/53 (64%) isolates were susceptible to all antimicrobial agents tested; there was intermediate susceptibility to tulathromycin in 12 isolates, tilmicosin in seven isolates and resistance to tilmicosin in one isolate. Using MIC, all but one isolate was susceptible to all antimicrobial agents tested; the non-susceptible isolate was resistant to tetracycline, but this MIC result could not be compared to disc diffusion, since there are no interpretative guidelines for disc diffusion for H. somni against tetracycline. In this study, there was little evidence of antimicrobial resistance in H. somni isolates from Australian cattle. Disc diffusion susceptibility testing results were comparable to MIC results for most antimicrobial agents tested; however, results for isolates with intermediate susceptibility or resistance to tilmicosin and tulathromycin on disc diffusion should be interpreted with caution in the absence of MIC results.

Item Type:Article
Business groups:Biosecurity Queensland
Keywords:Antimicrobial susceptibility Bovine respiratory disease Disc diffusion Histophilus somni Minimum inhibitory concentration ceftiofur enrofloxacin florfenicol tetracycline tilmicosin tulathromycin animal tissue antibiotic resistance antibiotic sensitivity Article Australia bacterium colony bacterium culture bacterium identification bacterium isolate Bovinae comparative study controlled study disk diffusion nonhuman polymerase chain reaction Bos
Subjects:Veterinary medicine > Communicable diseases of animals (General)
Animal culture > Cattle
Veterinary medicine > Veterinary bacteriology
Live Archive:18 Mar 2015 03:58
Last Modified:03 Sep 2021 16:44

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