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Antimicrobial susceptibility and molecular characteristics of Mycoplasma bovis isolated from cases of bovine respiratory disease in Australian feedlot cattle

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Hasoon, M. F., Jarocki, V. M., Mohammed, M. H., Djordjevic, S. P., Yip, H. Y. E., Carr, M., Khabiri, A., Azari, A. A., Amanollahi, R., Jozani, R. J., Carracher, B., Mollinger, J. L., Deutscher, A. T., Hemmatzadeh, F. and Trott, D. J. (2023) Antimicrobial susceptibility and molecular characteristics of Mycoplasma bovis isolated from cases of bovine respiratory disease in Australian feedlot cattle. Veterinary Microbiology, 283 . p. 109779. ISSN 0378-1135

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Article Link: https://doi.org/10.1016/j.vetmic.2023.109779

Publisher URL: https://www.sciencedirect.com/science/article/pii/S0378113523001311


To date, antimicrobial susceptibility has not been reported for Australian Mycoplasma bovis isolates. This study determined minimal inhibitory concentrations (MICs) for 12 different antimicrobials against Australian M. bovis isolates and used whole genome sequencing to screen those showing high macrolide MICs for point mutations in target genes. Most lung tissue/swab samples from bovine respiratory disease cases (61/76, 80.3%) tested positive for M. bovis. A set of 50 representative isolates (50/61, 82.0%) that showed adequate growth, was used for MIC testing. Uniformly, low MIC values were confirmed for enrofloxacin (≤ 4 μg/mL), florfenicol (≤ 8 μg/mL), gamithromycin (≤ 2 μg/mL), spectinomycin (≤ 4 μg/mL), tetracycline (≤ 8 μg/mL), tiamulin (≤ 4 μg/mL), and tulathromycin (≤ 0.5 μg/mL). A small proportion (10%) of isolates exhibited high MICs (≥ 32 μg/mL) for tildipirosin, tilmicosin, tylosin, and lincomycin, which were above the epidemiological cut-off values for each antimicrobial (≥ 4 μg/mL). These isolates, originating from three Australian states, underwent whole genome sequencing/multilocus sequencing typing and were compared with the reference strain PG45 to investigate mutations that might be linked with the high macrolide/lincosamide MICs. All five belonged to ST52 and two macrolide associated mutations were identified within the 23 S rRNA gene (A2058G in two sequenced isolates and G748A in all sequenced isolates). Four additional 23 S rRNA gene mutations did not appear to be linked to macrolide resistance. Whilst the majority of Australian M. bovis isolates appear susceptible to the tested antimicrobials, emerging macrolide resistance was detected in three Australian states and requires continued monitoring.

Item Type:Article
Corporate Creators:Department of Agriculture and Fisheries, Queensland
Business groups:Biosecurity Queensland
Keywords:MIC testing Broth microdilution BRD WGS AMR
Subjects:Animal culture > Cattle
Veterinary medicine > Veterinary microbiology
Veterinary medicine > Veterinary bacteriology
Animal culture > Feeds and feeding. Animal nutrition
Veterinary medicine > Diseases of special classes of animals > Cattle
Live Archive:29 Aug 2023 01:40
Last Modified:29 Aug 2023 01:40

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