Chronic non-progressive pneumonia in small ruminants caused by Mycoplasma (M.) ovipneumoniae is mainly controlled by chemotherapy. In France, during the last decade, a rise in M. ovipneumoniae cases was recorded in both sheep and goats, suggesting a possible emergence. Whether this rise is associated with antimicrobial resistance, as observed in other ruminant Mycoplasma species, has yet to be examined.

The aim of the study was to characterize the diversity of M. ovipneumoniae strains circulating in France and assess their antimicrobial resistance, together with the underlying mechanisms, to help find an explanation for the increase in reported cases.

The genetic diversity of 56 strains isolated between 2007 and 2018 from sheep and goats was assessed using different subtyping methods. Their susceptibility to six antimicrobial classes was profiled by estimating Minimum Inhibitory Concentrations (MICs) using an optimised agar dilution method. Resistance mechanisms were explored by sequence analysis of rRNA targets.

A high genetic diversity of strains was evidenced, with consistent, marked animal-host clustering in the Hsp70 gene and whole genome sequence phylogeny. No clonal evolution could thus account for putative emergence. Apart from florfenicol, MICs were low except for a few isolates with increased values for tetracyclines, macrolides and lincosamides. Hotspot mutations in the target ribosomal gene could explain increased tetracycline MICs. Other mechanisms are suspected for macrolide-lincosamide and florfenicol resistance.

The emergence of M. ovipneumoniae is thus not related to any increase in resistance or to a clonal spread. Explanations may lie in breeding practices.

卵型支原体（M. ovipneumoniae）引起的小反刍动物的慢性非进行性肺炎主要由化学疗法控制。在过去的十年中，法国的绵羊和山羊卵中M. ovipneumoniae病例均增加，这表明可能出现这种情况。如在其他反刍动物支原体物种中观察到的，这种升高是否与抗药性有关，尚待研究。

这项研究的目的是表征法国流通的卵形支原体菌株的多样性，并评估其耐药性，以及潜在的机制，以帮助解释所报告病例增加的原因。

使用不同的分型方法评估了2007年至2018年之间从绵羊和山羊分离出的56个菌株的遗传多样性。通过使用优化的琼脂稀释方法估算最低抑菌浓度（MIC）来描述其对六种抗菌药的敏感性。通过对rRNA靶标进行序列分析来探索耐药机制。

证明了菌株的高度遗传多样性，在Hsp70基因和整个基因组序列系统发育上具有一致的，明显的动物宿主簇。因此，没有克隆进化可以解释假定的出现。除了氟苯尼考以外，MIC较低，除了一些分离菌的四环素，大环内酯类和林可酰胺的值增加。目标核糖体基因中的热点突变可以解释四环素MIC的增加。怀疑大环内酯-林可酰胺和氟苯尼考耐药的其他机制。

因此，猪肺炎支原体的出现与耐药性的增加或克隆性传播无关。解释可能在于育种实践。