Genetic characterization and antimicrobial susceptibility of Mannheimia haemolytica isolated from the nasopharynx of feedlot cattle

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 we...

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Bibliographic Details
Published in:Veterinary microbiology 2011-05, Vol.149 (3-4), p.390-398
Main Authors: Klima, C.L., Alexander, T.W., Read, R.R., Gow, S.P., Booker, C.W., Hannon, S., Sheedy, C., McAllister, T.A., Selinger, L.B.
Format: Article
Language:English
Subjects:
Alberta
Animals
Anti-Bacterial Agents - pharmacology
Antimicrobial resistance
Bacteriology
Biological and medical sciences
Bovine respiratory disease
Cattle
Cluster Analysis
Disk-diffusion
Drug Resistance, Multiple, Bacterial
Electrophoresis, Gel, Pulsed-Field
Feedlot cattle
Female
Fundamental and applied biological sciences. Psychology
Genotype
Mannheimia haemolytica
Mannheimia haemolytica - classification
Mannheimia haemolytica - drug effects
Mannheimia haemolytica - genetics
Microbial Sensitivity Tests - veterinary
Microbiology
Miscellaneous
Nasopharynx - microbiology
PFGE
Phenotype
Polymerase Chain Reaction - methods
Serotyping
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Summary: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 blaROB-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.
ISSN:0378-1135
1873-2542
DOI:10.1016/j.vetmic.2010.11.018