Division of Infectious Diseases, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan.
J Microbiol Immunol Infect. 2012 Apr;45(2):108-12. doi: 10.1016/j.jmii.2011.09.001. Epub 2011 Dec 6.
Amino acid substitutions in GyrA and ParC are associated with resistance to quinolones in Acinetobacter baumannii (A baumannii), but this association is rarely elucidated in Acinetobacter genomic species (AGS) 13TU. This study aims to compare the association of amino acid substitutions in GyrA and ParC with quinolone resistance in A baumannii and AGS 13TU in Taiwan.
Eleven representative strains of A baumannii and 13 strains of AGS 13TU were selected from 402 bacteremic isolates. The sequences of quinolone resistance determining regions of gyrA and parC were determined. Minimal inhibitory concentrations (MICs) of nalidixic acid, ciprofloxacin, levofloxacin and moxifloxacin were determined by agar dilution method.
Ser83Leu substitution in GyrA in A baumannii (one strain) was associated with resistance to all tested quinolones. This substitution plus a Ser80Leu or Ser80Tyr in ParC in A baumannii (four strains) and AGS 13TU (two strains) were associated with higher MICs of all quinolones. All but one quinolone MICs of A baumannii (one strain) and AGS 13TU (two strains) carrying a single substitution Ser56Asn in ParC remained in the susceptibility breakpoint. The Ser83Leu substitution in GyrA, even with additional Ser56Asn substitution in ParC, was associated with resistance to only nalidixic acid, but not other newer quinolones in AGS 13TU (two strains).
A baumannii and AGS 13TU possessed similar quinolone resistance associated with amino acid substitutions in GyrA and ParC. Further study with more strains is needed to determine whether a single Ser83Leu substitution in GyrA was associated with a high level of quinolone MIC only in A baumannii, but not in AGS 13TU.
在鲍曼不动杆菌（A baumannii）中，GyrA 和 ParC 中的氨基酸取代与对喹诺酮类药物的耐药性相关，但这种关联在不动杆菌属基因组种（AGS）13TU 中很少被阐明。本研究旨在比较台湾 A baumannii 和 AGS 13TU 中 GyrA 和 ParC 中的氨基酸取代与喹诺酮类药物耐药性的相关性。
从 402 株菌血症分离株中选择了 11 株代表株的 A baumannii 和 13 株 AGS 13TU。确定了喹诺酮类药物耐药决定区的 gyrA 和 parC 的序列。通过琼脂稀释法测定了萘啶酸、环丙沙星、左氧氟沙星和莫西沙星的最小抑菌浓度（MIC）。
A baumannii 中 GyrA 的 Ser83Leu 取代（一株）与所有测试的喹诺酮类药物的耐药性相关。这种取代加上 A baumannii（四株）和 AGS 13TU（两株）中 ParC 的 Ser80Leu 或 Ser80Tyr，与所有喹诺酮类药物的 MIC 升高相关。除了一株携带 ParC 中单个取代 Ser56Asn 的 A baumannii（一株）和 AGS 13TU（两株）外，所有喹诺酮类药物的 MIC 均保持在敏感折点内。即使在 ParC 中存在 Ser56Asn 取代，GyrA 中的 Ser83Leu 取代也仅与萘啶酸的耐药性相关，而与 AGS 13TU（两株）中的其他新型喹诺酮类药物无关。
A baumannii 和 AGS 13TU 具有相似的喹诺酮类药物耐药性，与 GyrA 和 ParC 中的氨基酸取代相关。需要进一步研究更多的菌株，以确定 GyrA 中的单个 Ser83Leu 取代是否仅与 A baumannii 中喹诺酮类药物 MIC 的高水平相关，而与 AGS 13TU 无关。
