Publication: The moderate drift towards less tetracycline-susceptible isolates of contagious agalactia causative agents might result from different molecular mechanisms.
Authors
Prats-van der, Ham M ; Tatay-Dualde, J ; Ambroset, C ; De la Fe, C. ; Tardy, F.
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DOI
https://doi.org/10.1016/j.vetmic.2018.05.001
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info:eu-repo/semantics/article
Description
©2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
This document is the Accepted version of a Published Work that appeared in final form in Veterinary Microbiology. To access the final edited and published work see https://doi.org/10.1016/j.vetmic.2018.05.001
Abstract
Contagious agalactia is a mycoplasmosis that affects small ruminants, is associated with
loss of milk production and high morbidity rates, and is highly deleterious to dairy
industries. The etiological agents are four mycoplasma (sub)species, of which the
relative importance depends on the countries and the animal host. Tetracyclines are non 23 expensive, broad-spectrum antimicrobials and are often used to control mastitis in dairy
herds. However, the in vitro efficiency of tetracyclines against each of the etiological
agents of contagious agalactia has been poorly assessed.
The aims of this study were i) to compare the tetracycline susceptibilities of various
field isolates, belonging to different mycoplasma (sub)species and subtypes, collected
over the years from different clinical contexts in France or Spain, and ii) to investigate
the molecular mechanisms behind the decreased susceptibility of some isolates to
tetracyclines.
The Minimum Inhibitory Concentrations (MICs) of tetracyclines were determined in
vitro on a set of 120 isolates. Statistical analyses were run to define the significance of
any observed differences in MICs distribution. As mutations in the genes encoding the
ttracycline targets (rrs loci) are most often associated with increased tetracycline MICs
in animal mycoplasmas, these genes were sequenced.
The loss of susceptibility to tetracyclines after year 2010 is not significant and recent
MICs are higher in M. agalactiae, especially isolates from ovine mastitis cases, than in
other etiological agents of contagious agalactia. The observed increases in MICs were
not always associated with mutations in the rrs alleles which suggests the existence of
other resistance mechanisms yet to be deciphere
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