Antimicrobial Resistance in Members of the Bacterial Bovine Respiratory Disease Complex Isolated from Lung Tissue of Cattle Mortalities Managed with or without the Use of Antimicrobials

Abstract

Over a two-year period, Mannheimia haemolytica (MH; n = 113), Pasteurella multocida (PM; n = 47), Histophilus somni (HS; n = 41) and Mycoplasma bovis (MB; n = 227) were isolated from bovine lung tissue at necropsy from cattle raised conventionally (CON, n = 29 feedlots) or without antimicrobials [natural (NAT), n = 2 feedlots]. Excluding MB, isolates were assayed by PCR to detect the presence of 13 antimicrobial resistance (AMR) genes and five core genes associated with integrative and conjugative elements (ICEs). Antimicrobial susceptibility phenotypes and minimum inhibitory concentrations (MICs, µg/mL) were determined for a subset of isolates (MH, n = 104; PM, n = 45; HS, n = 23; and MB, n = 61) using Sensititre analyses. A subset of isolates (n = 21) was also evaluated by whole-genome sequencing (WGS) based on variation in AMR phenotype. All five ICE core genes were detected in PM and HS by PCR, but only 3/5 were present in MH. Presence of mco and tnpA ICE core genes in MH was associated with higher MICs (p < 0.05) for all tetracyclines, and 2/3 of all macrolides, aminoglycosides and fluoroquinolones evaluated. In contrast, association of ICE core genes with MICs was largely restricted to macrolides for PM and to individual tetracyclines and macrolides for HS. For MH, the average number of AMR genes markedly increased (p < 0.05) in year 2 of the study due to the emergence of a strain that was PCR positive for all 13 PCR-tested AMR genes as well as two additional AMR genes (aadA31 and blaROB-1) detected by WGS. Conventional management of cattle increased (p < 0.05) MICs of tilmicosin and tulathromycin for MH; neomycin and spectinomycin for PM; and gamithromycin and tulathromycin for MB. The average number of PCR-detected AMR genes in PM was also increased (p < 0.05) in CON mortalities. This study demonstrates increased AMR especially to macrolides by bovine respiratory disease organisms in CON as compared to NAT feedlots and a rapid increase in AMR following dissemination of strain(s) carrying ICE-associated multidrug resistance.

Multidrug Resistance in Pasteurellaceae Associated With Bovine Respiratory Disease Mortalities in North America From 2011 to 2016

“…Since the discovery of ICE Pmu1 in P. multocida ( Michael et al, 2012a ), and ICE Mh1 in M. haemolytica ( Eidam et al, 2015 ), multiple ICEs have been documented in Pasteurellaceae , many of which are associated with possible XDR ( Klima et al, 2016 ; Cameron et al, 2018 ; Kadlec et al, 2018 ; Stanford et al, 2020 ). All have a similar backbone with regions of functional genes associated with conjugation, recombination and regulation grouped together and in similar orientation.…”

“…Samples from study 1 consisted of fresh tissue stored at 4 • C for a period no longer than 10 days prior to bacterial isolation (Klima et al, 2014b). In studies 2 and 3, when delivery time was projected to exceed 72 h, tissues were frozen and stored at −20 • C until processed (Anholt et al, 2017;Stanford et al, 2020). Metadata for the animals sampled were provided from submitting veterinary practices and included diagnosis and gross pathology for each case.…”

Monitoring Mycoplasma bovis Diversity and Antimicrobial Susceptibility in Calf Feedlots Undergoing a Respiratory Disease Outbreak

“…Prevention and control of BRD rely on metaphylaxis in high-risk herds (e.g., >1000 animals in the USA), bacterial vaccinations when available, but with controversial efficacies, and antimicrobial treatments of diseased animals [ 11 , 12 ]. Because feedlot management uses many antimicrobials, antimicrobial resistance (AMR) among the bacterial pathogens commonly associated with BRD has been increasingly reported worldwide [ 12 , 13 ]. M. bovis is no exception [ 14 ].…”

A Sensitive and Accurate Recombinase Polymerase Amplification Assay for Detection of the Primary Bacterial Pathogens Causing Bovine Respiratory Disease

“…The M. haemolytica isolates represented both serotypes A1 and A6 and encompassed 35 different pulsed field gel electrophoresis (PFGE) profiles. Isolates were obtained from lung tissues of BRD mortalities, collected in both Canada and the USA (9,15,24). Arising from the same studies, P. multocida and H. somni isolates belonged to 31 and 21 PFGE types, respectively.…”

“…The resulting multi-drug resistance (MDR) among some BRD pathogens containing ICE presents a significant challenge for the efficacy of antimicrobial therapy as a treatment for BRDClawson et al (12) found that the gene tet(H), which confers tetracycline resistance was present in all AMR M. haemolytica strains isolated from confirmed BRD cases, and was also frequently found in P. multocida (13) and H. somni ICE (14). Furthermore, tet(H) was adjacent to the transposase gene tnpA, a core ICE gene associated with increased minimum inhibitory antimicrobial concentrations in M. haemolytica, H. somni, and P. multocida (15).…”