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

Kim Stanford; Rahat Zaheer; Cassidy Klima; Tim McAllister; Delores Peters; Yan D Niu; Brenda Ralston

doi:10.3390/microorganisms8020288

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

Microorganisms. 2020 Feb 20;8(2):288. doi: 10.3390/microorganisms8020288.

Authors

Kim Stanford¹, Rahat Zaheer², Cassidy Klima², Tim McAllister², Delores Peters³, Yan D Niu⁴, Brenda Ralston³

Affiliations

¹ Alberta Agriculture and Forestry, Lethbridge, AB T1J 4V6, Canada.
² Agriculture and Agri-Food Canada, Lethbridge, AB T1J 4B1, Canada.
³ Alberta Agriculture and Forestry, Airdrie, AB T4A 0C3, Canada.
⁴ University of Calgary, Calgary, AB T2N 1N4, Canada.

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 bla_ROB-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.

Keywords: Histophilus somni; Mannheimia haemolytica; Mycoplasma bovis; Pasteurella multocida; antimicrobial resistance; bovine respiratory disease; managed without antimicrobials.

Grants and funding

2015-13/Alberta Agriculture and Forestry Animal Health Biosecurity Internal Initiatives