Antimicrobial susceptibility and multilocus sequence typing of Mycoplasma capricolum subsp. capricolum

Mycoplasma capricolum subsp. capricolum is one of the causative agents of contagious agalactia (CA). Nevertheless, there is still a lack of information about its antimicrobial susceptibility and genetic characteristics. Therefore, the aim of this work was to study the antimicrobial and genetic variability of different Mycoplasma capricolum subsp. capricolum field isolates. For this purpose, the growth inhibition effect of 18 antimicrobials and a multilocus sequence typing (MLST) scheme based on five housekeeping genes (fusA, glpQ, gyrB, lepA and rpoB) were performed on 32 selected field isolates from Italy and Spain.The results showed a wide range of growth inhibitory effects for almost all the antimicrobials studied. Macrolides presented lower efficacy inhibiting Mcc growth than in previous works performed on other CA-causative mycoplasmas. Erythromycin was not able to inhibit the growth of any of the studied strains, contrary to doxycycline, which inhibited the growth of all of them from low concentrations. On the other hand, the study of the concatenated genes revealed a high genetic variability among the different Mcc isolates. Hence, these genetic variations were greater than the ones reported in prior works on other mycoplasma species.

山羊支原体山羊亚种（Mycoplasma capricolum subsp. capricolum）是传染性无乳症（contagious agalactia, CA）的致病菌之一。目前学界对其抗菌药物敏感性与遗传特征的相关研究仍存在不足。为此，本研究旨在探究不同山羊支原体山羊亚种野外分离株的抗菌活性与遗传变异性。实验针对32株采自意大利与西班牙的野外分离株，开展了18种抗菌药物的生长抑制试验，并基于fusA、glpQ、gyrB、lepA及rpoB这5个持家基因（housekeeping genes）构建了多位点序列分型（multilocus sequence typing, MLST）方案。结果显示，几乎所有受试抗菌药物均表现出宽泛的生长抑制活性范围。大环内酯类药物对该菌（以下简称Mcc）的生长抑制效果弱于此前针对其他传染性无乳症致病支原体的相关研究。与多西环素（可从低浓度起抑制所有受试菌株的生长）不同，红霉素无法抑制任何一株受试菌株的生长。另一方面，对串联基因的分析揭示了不同Mcc分离株间存在高度遗传变异性，且该变异程度高于此前针对其他支原体物种的报道。