Tatay-Dualde Juan, Prats-van der Ham Miranda, de la Fe Christian, Paterna Ana, Sánchez Antonio, Corrales Juan Carlos, Contreras Antonio, Gómez-Martín Ángel
Department of Animal Health, Faculty of Veterinary Sciences, Regional Campus of International Excellence "Campus Mare Nostrum", Universidad de Murcia, Campus de Espinardo s/n., 30100 Murcia, Spain.
Department of Animal Health, Faculty of Veterinary Sciences, Regional Campus of International Excellence "Campus Mare Nostrum", Universidad de Murcia, Campus de Espinardo s/n., 30100 Murcia, Spain.
Vet Microbiol. 2017 Aug;207:63-68. doi: 10.1016/j.vetmic.2017.06.003. Epub 2017 Jun 12.
M. agalactiae is the main causative agent of contagious agalactia, against which antimicrobial treatment is the main applied control measure. Quinolones are an effective group of antimicrobials inhibiting the growth of M. agalactiae, but in the last years, various reports have demonstrated an increase of resistance in field isolates due to its massive use. Nevertheless, the molecular mechanisms involved in the acquisition of fluoroquinolones resistance in M. agalactiae have not been elucidated yet. Therefore, the aim of this work was to analyze the presence of DNA variations that could be related to changes in fluoroquinolone susceptibility. For this purpose, three M. agalactiae strains were selected to obtain in vitro resistant mutants against enrofloxacin, marbofloxacin and moxifloxacin and afterwards, partial sequences of their gyrA, gyrB, parC and parE genes were analyzed. In addition, a set of field isolates with different MIC values were also studied. Changes related to variations in fluoroquinolones susceptibility were found in gyrB, parC and parE. Specifically, gyrB genes were affected at the predicted amino acid position 424, four amino acid changes were detected in parC (positions 78, 79, 80 and 84) and two substitutions were reported in parE (amino acid positions 429 and 459). Mutations at predicted positions 424 of gyrB and 429 of parE are novel DNA changes which had not been previously described and, on the whole, parC was the first gene showing alterations when changes in susceptibility to fluoroquinolones occurred. Thus, this gene is the most suitable target for a rapid study of fluoroquinolone resistance in field isolates of M. agalactiae.
无乳支原体是传染性无乳症的主要病原体，针对该病的主要应用控制措施是抗菌治疗。喹诺酮类是抑制无乳支原体生长的一类有效抗菌药物，但在过去几年中，由于其大量使用，各种报告显示田间分离株的耐药性有所增加。然而，无乳支原体获得氟喹诺酮耐药性所涉及的分子机制尚未阐明。因此，本研究的目的是分析可能与氟喹诺酮敏感性变化相关的DNA变异的存在情况。为此，选择了三株无乳支原体菌株，以获得对恩诺沙星、马波沙星和莫西沙星的体外耐药突变体，然后分析其gyrA、gyrB、parC和parE基因的部分序列。此外，还研究了一组具有不同最低抑菌浓度值的田间分离株。在gyrB、parC和parE中发现了与氟喹诺酮敏感性变化相关的改变。具体而言，gyrB基因在预测的氨基酸位置424处受到影响，在parC中检测到四个氨基酸变化（位置78、79、80和84），在parE中报告了两个替换（氨基酸位置429和459）。gyrB的预测位置424和parE的429处的突变是以前未描述过的新DNA变化，总体而言，当氟喹诺酮敏感性发生变化时，parC是第一个显示改变的基因。因此，该基因是快速研究无乳支原体田间分离株氟喹诺酮耐药性的最合适靶点。
