biostudies-literatureNoyes NRAdvancing Canadian Agriculture and Agri-FoodCanadian Cattlemen&apos;s AssociationBoehringer IngelheimBeef Cattle Research CouncilAlberta Beef ProducersNIH HHS705-13https://www.ebi.ac.uk/biostudies/studies/S-EPMC4895489biostudies-literatureUnknown29(2)<h4>Background</h4>Mannheimia haemolytica is an important etiological agent in bovine respiratory disease.<h4>Objectives</h4>Explore risk factors for recovery of susceptible and resistant M. haemolytica in feedlot cattle and explore associations with health outcomes.<h4>Animals</h4>Cattle (n = 5,498) from 4 feedlots sampled at arrival and later in feeding period.<h4>Methods</h4>Susceptibility of M. haemolytica isolates tested for 21 antimicrobials. Records of antimicrobial use and health events analyzed using multivariable regression.<h4>Results</h4>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).<h4>Conclusions and clinical importance</h4>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.Journal of veterinary internal medicineMannheimia haemolytica in feedlot cattle: prevalence of recovery and associations with antimicrobial use, resistance, and health outcomes.PMC4895489BCRC 6.41T32 OD0122010007-038RDBBenedict KMNoyes NRMorley PSGow SPMcAllister TABooker CWHannon SJfalseMannheimia haemolytica in feedlot cattle: prevalence of recovery and associations with antimicrobial use, resistance, and health outcomes.<h4>Background</h4>Mannheimia haemolytica is an important etiological agent in bovine respiratory disease.<h4>Objectives</h4>Explore risk factors for recovery of susceptible and resistant M. haemolytica in feedlot cattle and explore associations with health outcomes.<h4>Animals</h4>Cattle (n = 5,498) from 4 feedlots sampled at arrival and later in feeding period.<h4>Methods</h4>Susceptibility of M. haemolytica isolates tested for 21 antimicrobials. Records of antimicrobial use and health events analyzed using multivariable regression.<h4>Results</h4>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).<h4>Conclusions and clinical importance</h4>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.2015-01-01T00:00:00Z2015 Mar-Apr2025-04-20T01:54:08.051Z2019-03-27T02:15:28ZS-EPMC48954892581822410.1111/jvim.12547