Molecular characterization of strains of fluoroquinolone-resistant Salmonella enterica serovar Schwarzengrund carrying multidrug resistance isolated from imported foods
Molecular characterization of strains of fluoroquinolone-resistant Salmonella enterica serovar Schwarzengrund carrying multidrug resistance isolated from imported foods
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DOI：
10.1093/jac/dkr414
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发表时间：
2012-01-01
影响因子：
5.2
通讯作者：
Khan, Ashraf A.
中科院分区：
文献类型：
--
作者：
Akiyama, Tatsuya;Khan, Ashraf A.
目的：了解进口食品中肠道沙门氏菌对氟喹诺酮类药物的耐药情况。方法：采用纸片琼脂扩散法和ETEST法检测沙门氏菌对16种抗生素的敏感性。通过gyrA、gyrB、parC和pARE基因序列分析、qnrA、qnrB和qnrS基因扩增以及AcrB、raA、marA、soxs和rob基因的定量RT-PCR检测耐喹诺酮类药物的决定因素。外排泵活性对抗生素耐药性的贡献是通过添加乙酰氰基间氯苯肼(CCCP)确定的。结果：沙门氏菌30株和487株对环丙沙星敏感，与对环丙沙星高度耐药的75株相比，gyrA基因发生单突变。RAMA的高表达与对环丙沙星的高耐药性有关。菌株75在调节RAMA表达的ramR基因上有315个碱基的缺失。RAMA的过度表达可能与RamR的缺失有关。RamR的引入使环丙沙星的MIC从48 mg/L降至24 mg/L，CCCP的加入并未降低抗生素耐药性。据我们所知，本研究首次报道了施瓦辛沙门氏菌中ramR的自然缺失。结论：本研究表明，进口食品中普遍存在耐氟喹诺酮类沙门氏菌。GyrA双突变和ramR缺失与耐多药沙门氏菌75株的高水平喹诺酮耐药有关。
Objectives: To determine the fluoroquinolone resistance determinants in Salmonella enterica serovar Schwarzengrund from imported foods.Methods: Antibiotic susceptibility of Salmonella Schwarzengrund to 16 antibiotics was examined using disc agar diffusion and Etest. Quinolone resistance determinants were examined by sequence analysis of gyrA, gyrB, parC and parE, PCR amplification of qnrA, qnrB and qnrS, and expression of acrB, ramA, marA, soxS and rob using quantitative RT-PCR. The contribution of efflux pump activities to antibiotic resistance was determined by the addition of carbonyl cyanide m-chlorophenylhydrazone (CCCP). The effect of ramR deletion on ciprofloxacin resistance was determined by complementing with wild-type ramR.Results: Salmonella strains 30 and 487 were susceptible to ciprofloxacin and had a single mutation in gyrA as compared with strain 75, which was highly resistant to ciprofloxacin and had a double mutation in gyrA. Increased expression of ramA was associated with high resistance to ciprofloxacin. Strain 75 had a deletion of 315 bp in the ramR gene, which regulates ramA expression. Overexpression of ramA was possibly related to a loss of ramR. Introduction of ramR decreased the MIC of ciprofloxacin from 48 to 24 mg/L. The addition of CCCP did not reduce antibiotic resistance. To our knowledge, this study reports for the first time the natural deletion of ramR in Salmonella Schwarzengrund.Conclusions: This study indicates that fluoroquinolone-resistant Salmonella are prevalent in imported food. Double mutations in gyrA and a loss of ramR were associated with high-level quinolone resistance in multidrug-resistant Salmonella Schwarzengrund strain 75.