Sharma V, Dahiya S, Jangra P, Das B K, Kumar R, Sood S, Kapil A
Department of Microbiology, All India Institute of Medical Sciences, New Delhi, India.
Indian J Med Microbiol. 2013 Oct-Dec;31(4):374-8. doi: 10.4103/0255-0857.118898.
There are increasing reports on failure of clinical response to ciprofloxacin in typhoid fever despite the strain being sensitive to drug in in-vitro using standard guidelines and showing mutations in DNA gyrase. But this increased MIC and clinical failures with ciprofloxacin are not always co-related with mutations presently identified in gyrA and parC genes. This shows that there may be other mechanisms such as an active drug efflux pump responsible as has been shown in other Enterobacteriaceae. This study was carried out to determine the role of efflux pump in Salmonella Typhi isolates.
Total 25 already characterized nalidixic acid sensitive and nalidixic acid resistant S. Typhi strains with different range of ciprofloxacin MIC were included to study the role of efflux pump in the presence of CCCP (efflux pump inhibitor). For genotypic characterization, the entire acrR gene was sequenced to confirm the presence of any mutation in the gene.
The MIC of ciprofloxacin remained same in the presence and absence of CCCP in the studied strains and no significant mutations were found in the acrR gene in any of the isolates studied.
No role of efflux pump in ciprofloxacin resistance was found in strains studied. There is a need to explore further mechanism of ciprofloxacin resistance in Salmonella Typhi.
尽管按照标准指南，伤寒杆菌菌株在体外对环丙沙星敏感且未显示DNA促旋酶突变，但关于伤寒热患者对环丙沙星临床反应失败的报道却越来越多。然而，环丙沙星这种增加的最低抑菌浓度（MIC）和临床治疗失败情况并不总是与目前在gyrA和parC基因中鉴定出的突变相关。这表明可能存在其他机制，比如像在其他肠杆菌科细菌中所显示的那样，存在一种活性药物外排泵。本研究旨在确定外排泵在伤寒沙门氏菌分离株中的作用。
总共纳入25株已鉴定的对萘啶酸敏感和耐药的伤寒杆菌菌株，这些菌株具有不同范围的环丙沙星MIC，用于研究在存在碳酰氰间氯苯腙（CCCP，一种外排泵抑制剂）的情况下外排泵的作用。为了进行基因分型，对整个acrR基因进行测序，以确认该基因中是否存在任何突变。
在所研究的菌株中，无论有无CCCP，环丙沙星的MIC均保持不变，并且在所研究的任何分离株中，acrR基因均未发现明显突变。
在所研究的菌株中未发现外排泵在环丙沙星耐药性中起作用。有必要进一步探索伤寒沙门氏菌中环丙沙星耐药性的机制。
