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J Vet Intern Med. 2015 Mar-Apr;29(2):705-13. doi: 10.1111/jvim.12547.

Mannheimia haemolytica in feedlot cattle: prevalence of recovery and associations with antimicrobial use, resistance, and health outcomes.

Author information

1
Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO.

Abstract

BACKGROUND:

Mannheimia haemolytica is an important etiological agent in bovine respiratory disease.

OBJECTIVES:

Explore risk factors for recovery of susceptible and resistant M. haemolytica in feedlot cattle and explore associations with health outcomes.

ANIMALS:

Cattle (n = 5,498) from 4 feedlots sampled at arrival and later in feeding period.

METHODS:

Susceptibility of M. haemolytica isolates tested for 21 antimicrobials. Records of antimicrobial use and health events analyzed using multivariable regression.

RESULTS:

M. haemolytica recovered from 29% of cattle (1,596/5,498), 13.1% at arrival (95% CI, 12.3-14.1%), and 19.8% at second sampling (95% CI, 18.7-20.9%). Nearly half of study cattle received antimicrobial drugs (AMDs) parenterally, mostly as metaphylactic treatment at arrival. Individual parenteral AMD exposures were associated with decreased recovery of M. haemolytica (OR, 0.2; 95% CI, 0.02-1.2), whereas exposure in penmates was associated with increased recovery (OR, 1.5; 95% CI, 1.05-2.2). Most isolates were pan-susceptible (87.8%; 95% CI, 87.0-89.4%). AMD exposures were not associated with resistance to any single drug. Multiply-resistant isolates were rare (5.9%; 95% CI, 5.1-6.9%), but AMD exposures in pen mates were associated with increased odds of recovering multiply-resistant M. haemolytica (OR, 23.9; 95% CI, 8.4-68.3). Cattle positive for M. haemolytica on arrival were more likely to become ill within 10 days (OR, 1.7; 95% CI, 1.1-2.4).

CONCLUSIONS AND CLINICAL IMPORTANCE:

Resistance generally was rare in M. haemolytica. Antimicrobial drug exposures in penmates increased the risk of isolating susceptible and multiply-resistant M. haemolytica, a finding that could be explained by contagious spread.

KEYWORDS:

Antibiotic resistance; Pasteurella haemolytica; morbidity; mortality

PMID:
25818224
PMCID:
PMC4895489
DOI:
10.1111/jvim.12547
[Indexed for MEDLINE]
Free PMC Article

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