Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Antimicrobial Susceptibility and Resistance Mechanisms in Mannheimia haemolytica Isolates From Sheep at Slaughter

Julio Alvarez
ORCID logo ,
Johan M. Calderón Bernal
,
Laura Torre-Fuentes
,
Marta Hernández
ORCID logo ,
Chris E. Pinto Jimenez
,
Lucas Domínguez
,
José F. Fernández-Garayzábal
ORCID logo ,
Ana I. Vela
* ,
Dolores Cid
ORCID logo
Version 1 : Received: 17 April 2023 / Approved: 18 April 2023 / Online: 18 April 2023 (04:15:36 CEST)

A peer-reviewed article of this Preprint also exists.

Alvarez, J.; Bernal, J.M.C.; Torre-Fuentes, L.; Hernández, M.; Jimenez, C.E.P.; Domínguez, L.; Fernández-Garayzábal, J.F.; Vela, A.I.; Cid, D. Antimicrobial Susceptibility and Resistance Mechanisms in Mannheimia haemolytica Isolates from Sheep at Slaughter. Animals 2023, 13, 1991. Alvarez, J.; Bernal, J.M.C.; Torre-Fuentes, L.; Hernández, M.; Jimenez, C.E.P.; Domínguez, L.; Fernández-Garayzábal, J.F.; Vela, A.I.; Cid, D. Antimicrobial Susceptibility and Resistance Mechanisms in Mannheimia haemolytica Isolates from Sheep at Slaughter. Animals 2023, 13, 1991.

Abstract

Mannheimia haemolytica is the main pathogen contributing to pneumonic pasteurellosis in sheep. The aim of this study was to investigate the antimicrobial resistance levels in M. haemolytica from the lungs of slaughtered sheep and the genetic resistance mechanisms involved. A total of 256 M. haemolytica isolates, 169 from lungs with pneumonic lesions and 87 without, were analyzed by the disk diffusion method for 12 antimicrobials, and the whole genome of 14 isolates sequenced to identify resistance determinants. Levels of phenotypic resistance ranged from <2 % for 10 antimicrobials (amoxicillin, amoxicillin-clavulanic, ceftiofur, cefquinome, lincomycin/spectinomycin, gentamicin, erythromycin, florfenicol, enrofloxacin, and doxycycline) to 4.3% for tetracycline and 89.1% for tylosin. Six isolates carried tetH genes and four carried, in addition, strA and sul2 genes in putative plasmid sequences. No mutations associated with macrolide resistance were identified in 23 rDNA sequences suggesting that M. haemolytica phenotypic results for tylosin should be interpreted with care in the absence of well-established epidemiological and clinical breakpoints. The identification of strains phenotypically resistant to tetracycline and of several resistance genes, some of which were present in plasmids, highlight the need for continuous monitoring of susceptibility patterns in Pasteurellaceae isolates from livestock

Keywords

Mannheimia haemolytica; antimicrobial resistance; mobile genetic elements; tetH; strA; sul2; sheep

Subject

Biology and Life Sciences, Animal Science, Veterinary Science and Zoology

Copyright: This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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