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首页> 外文期刊>Journal of Medical Microbiology: An Official Journal of the Pathological Society of Great Britain and Ireland >Molecular analysis of low-level fluoroquinolone resistance in clinical isolates of Moraxella catarrhalis
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Molecular analysis of low-level fluoroquinolone resistance in clinical isolates of Moraxella catarrhalis

机译：Moraxella catarrhalis临床分离株低水平氟代喹啉抗性的分子分析

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We investigated antimicrobial susceptibility and the molecular mechanism underlying low-level resistance to fluoroquinolones in 70 non-duplicate clinical isolates of Moraxella catarrhalis. The isolates were collected in a general hospital in Tokyo, Japan, between January and October 2013 from 38 men and 32 women; most of the isolates (48 out of 70, 68.5 %) were obtained from post-nasal drips of children. The antimicrobial susceptibility of M. catarrhalis isolates was determined with an Etest, and low-level fluoroquinolone-resistant isolates were subtyped by PFGE. Mutations in the gyrA and parC genes were determined by PCR and sequencing. PCR products of the gyrA and parC genes from the low-level fluoroquinolone-resistant isolates were transformed into a fluoroquinolone-susceptible strain. Among the 70 isolates, five (7.1 %) exhibited elevated fluoroquinolone MICs (levofloxacin, 1.0 mg l?1; ciprofloxacin, 0.5 mg l?1) and different PFGE patterns. The patients from whom these five isolates were isolated had not undergone treatment with fluoroquinolones for the past 6 months. Each of the five low-level fluoroquinolone-resistant isolates had a gyrA gene mutation resulting in a Thr-to-Ile substitution at aa 80 (T80I) in the GyrA protein, while no changes were detected in the parC gene. A transformant carrying the gyrA gene containing the T80I substitution, which corresponded to Ser83 in Escherichia coli, displayed an elevated fluoroquinolone MIC and contained the T80I alteration in GyrA. Thus, our findings reveal that the low-level resistance to fluoroquinolones in M. catarrhalis is due to an amino acid substitution of Thr80 to Ile in GyrA. This is the first evidence of low-level fluoroquinolone resistance in M. catarrhalis.
机译：我们研究了70个非重复临床分离株的抗微生物易感性和低水平抗性低水平抗性抗性耐氟喹啉。分离株在2013年1月至10月的38名男子和32名女性之间在日本东京的一家综合医院收集;大多数分离株（70例，68.5％的48％）是从儿童的后鼻腔滴水中获得的。用ETEST测定M. Catarrhalis分离物的抗微生物敏感性，并且低水平的氟代喹啉酮抗性分离物通过PFGE亚级。通过PCR和测序测定Gyra和Parc基因中的突变。从低水平氟代喹啉龙分离株的Gyra和Parc基因的PCR产物转化为氟喹诺酮易感菌株。在70个分离物中，五（7.1％）表现出升高的氟喹诺酮MICS（左氧氟沙星，1.0mgα1;环丙沙星，0.5mg L = 1）和不同的PFGE图案。将分离出这五个分离株的患者在过去6个月内没有用氟代喹啉酮治疗。五种低水平氟喹啉酮的分离物中的每一个具有Gyra基因突变，导致Gyra蛋白中AA 80（T80I）的Th-Ile取代，而在Parc基因中没有检测到任何变化。携带含有T80I取代的Gyra基因的转化体，其与大肠杆菌中的Ser83相对应，呈氟喹诺酮MIC呈升高，并含有Gyra的T80I改变。因此，我们的研究结果表明，M. catarrhalis中对氟喹诺酮酮的低水平抗性是由于氨基酸替代在Gyra中的氨基酸取代。这是M. catarrhalis中低水平氟喹啉抗性的第一种证据。

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