期刊
VETERINARY MICROBIOLOGY
卷 149, 期 3-4, 页码 390-398出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.vetmic.2010.11.018
关键词
Antimicrobial resistance; Bovine respiratory disease; Disk-diffusion; Feedlot cattle; Mannheimia haemolytica; PFGE
资金
- Advancing Canadian Agriculture and Agri-Food (ACAAF) Program
- Agriculture and the Agri-Food Canada Matching Investment Initiative
- Alberta Beef Producers
- Beef Cattle Research Council
A surveillance study was undertaken to examine the population dynamics and antimicrobial resistance of Mannheimia haemolytica isolated from feedlot cattle. A total of 416 isolates were collected from the nasopharynx either upon entry or exit from two feedlots in southern Alberta, Canada. Isolates were serotyped, characterized by pulsed-field gel electrophoresis and tested for susceptibility to ten antimicrobial agents via disk diffusion. Resistant isolates were screened by PCR for select antimicrobial-resistance gene determinants. Isolates were highly diverse, with 335 unique pulsed-field profiles identified among 147 strongly related clusters (similarity >= 85%). Clonal spread of isolates throughout the feedlots was limited and no clear association was found between genetic relatedness of M. haemolytica and sampling event (entry or exit). Pulsed-field profiles sharing a common serotype and resistance phenotype tended to cluster together. The majority of isolates were identified as serotype 2 (74.5%) although both serotype 1(11.9%) and 6 (12.7%) were detected. Only 9.54% of isolates exhibited antimicrobial resistance. Resistance to oxytetracycline was most prevalent (n = 16), followed by ampicillin (n = 10), and amoxicillin/clavulanic acid (n = 7). Multi-drug resistance was observed in five isolates. The tetH gene was detected in all but two oxytetracycline resistant isolates. Other detectable resistance determinates included ermX and bla(ROB-1). In the two feedlots examined, M. haemolytica exhibited considerable genetic diversity and limited resistance to common veterinary antibiotics. Garnering further information on the linkage between genotype and phenotype should contribute toward a better understanding of the pathogenesis and dissemination of M. haemolytica in feedlots. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.
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