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Respiratory diseases constitute a major health challenge for the worldwide pork industry. Porcine enzootic pneumonia (PES) is caused by Mycoplasma hyopneumoniae (Mhyo). Mycoplasmas have the ability to produce extracellular vesicles (EVs), which can be useful for pathogenicity studies and as delivery systems for vaccines. The aim of this study was to demonstrate and compare, under laboratory conditions, EVs produced by Mhyo strain J and wild isolate in stressed and non-stressed in vitro conditions. Using differential centrifugation, density gradient ultracentrifugation, and transmission electron microscopy, the ability of Mhyo strains to produce EVs was demonstrated under favorable and unfavorable conditions.

Mycoplasma hyopneumoniae is the etiologic agent of porcine enzootic pneumonia, responsible for major production losses worldwide. The bacteria have a limited metabolism and need to obtain molecules from the growth environment, which causes multiple difficulties for in vitro culture. These limitations have a negative influence on the ability to carry out research for the development of the rational use of antimicrobials and vaccines. The objective of this investigation was to evaluate the genetic profile and in vitro susceptibility of field isolates of M. hyopneumoniae to different antimicrobials. All 16 isolates obtained from the samples presented 100% of identity in the partial sequence of 16S rRNA gene when compared to M. hyopneumoniae. A dendrogram was created using the PCR results of the genes related to pathogenicity, and the isolates were distributed into four clusters, suggesting genetic variability among four different isolates circulating on the same farm. The minimum inhibitory concentration of the isolates was higher for the antimicrobials tylosin (< 0.001–16 mg/L) and spiramycin (< 0.001–16 mg/L) than for enrofloxacin (< 0.001–0.125 mg/L) and tiamulin (< 0.001–0.125 mg/L). Our results demonstrate the genetic variability among M. hyopneumoniae isolates from pigs of the same farm, with differences in their susceptibility to antimicrobial agents. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s42770-019-00185-0) contains supplementary material, which is available to authorized users.