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Single locus sequence typing and macrorestriction to assess Mycoplasma bovis diversity in feedlot calves prior and after antimicrobial treatments
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International audience. BackgroundMycoplasma (M.) bovis is a major etiological agent of bovine respiratory diseases (BRD) responsible for important economic losses worldwide. In France, current isolates collected in the framework of the Vigimyc network are distributed in two subtypes (ST): ST2 (81 %) and ST3 (19 %). These results could be biased because of the modalities of strains recruitment, usually in acute clinical cases after treatment failure. The present study was conducted to assess the diversity of isolates collected directly from feedlot veal calves prior and after antimicrobial treatments.MethodsNasal swabs were collected at calves entry (B0), at clinical onset (B1) and ~4 weeks after the end of antimicrobial treatments (B2) in 21 herds. The collected M. bovis isolates were subtyped using Single Locus Sequence Typing (polC gene) and Pulse-Field Gel Electrophoresis (PFGE) in order to estimate their diversity at different levels (fattening unit or calf). ResultsThe overall proportion of the two ST was identical to that derived from Vigimyc isolates (ST3=19%) and did not change in the course of the clinical episode. One isolate presented a new atypical ST. PFGE analysis of 61 representative isolates confirmed the homogeneity of ST2 isolates (one cluster) in contrast to the diversity of ST3 isolates observed at the calf or feedlot level.ConclusionThe ST proportions, as observed through the Vigimyc network, was confirmed and no influence of the antimicrobial treatments on strains diversity was evidenced.
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