Expression of efflux pump gene pmrA in fluoroquinolone-resistant and -susceptible clinical isolates of Streptococcus pneumoniae
Expression of efflux pump gene pmrA in fluoroquinolone-resistant and -susceptible clinical isolates of Streptococcus pneumoniae
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DOI：
10.1128/aac.46.3.808-812.2002
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发表时间：
2002-03-01
影响因子：
4.9
通讯作者：
Pumbwe, L
中科院分区：
文献类型：
--
作者：
Piddock, LJV;Johnson, MM;Pumbwe, L
根据对诺氟沙星的敏感性和利血平（20马克杯/毫升）的作用，将34株环丙沙星耐药（MIC大于等于2马克杯/毫升）和12株环丙沙星敏感肺炎链球菌临床分离株分为4组。对所有环丙沙星耐药临床分离株的parC、parE、gyrA和gyrB的喹诺酮类耐药区进行了测序，并测定了其他8种氟喹诺酮类药物、吖啶黄、溴化乙啶、氯霉素和四环素在利血平存在和不存在时的活性。尽管利血平对诺氟沙星的活性有显著影响，但只有少数分离株的另一种氟喹诺酮类药物的活性被利血平增强。对于大多数分离株，尽管利血平对氟喹诺酮类药物活性没有影响，但在利血平的存在下，吖啶黄和溴化乙锭的mic都降低了。对氟喹诺酮类药物最耐药的菌株主要是那些有三个基因突变的菌株。采用Northern blotting（定量竞争逆转录酶PCR）检测外排泵PmrA编码基因的表达，并与肺炎链球菌R6和R6N进行比较。在每一组中都有高、中、低表达该基因的分离株；然而，增加的表达并不完全与那些具有提示外排突变表型的分离株相关。这些数据表明，肺炎链球菌中存在另一种利血平敏感的外排泵，可挤出溴化乙啶和吖啶黄，但不能挤出氟喹诺酮类药物。
Thirty-four ciprofloxacin-resistant (MIC greater than or equal to 2 mug/ml) and 12 ciprofloxacin-susceptible clinical isolates of Streptococcus pneumoniae were divided into four groups based upon susceptibility to norfloxacin and the effect of reserpine (20 mug/ml). The quinolone-resistance-determining regions of parC, parE, gyrA, and gyrB of all ciprofloxacin-resistant clinical isolates were sequenced, and the activities of eight other fluoroquinolones, acriflavine, ethidium bromide, chloramphenicol, and tetracycline in the presence and absence of reserpine were determined. Despite a marked effect of reserpine upon the activity of norfloxacin, there were only a few isolates for which the activity of another fluoroquinolone was enhanced by reserpine. For most isolates the MICs of acriflavine and ethidium bromide were lowered in the presence of reserpine despite the lack of effect of this efflux pump inhibitor on fluoroquinolone activity. The strains that were most resistant to the fluoroquinolones were predominantly those with mutations in three genes. Expression of the gene encoding the efflux pump PmrA was examined by Northern blotting (quantified by quantitative competitive reverse transcriptase PCR) and compared with that of S. pneumoniae R6 and R6N. Within each group there were isolates that had high-, medium-, and low-level expression of this gene; however, increased expression was not exclusively associated with those isolates with a phenotype suggestive of an efflux mutant. These data suggest that there is another reserpine-sensitive efflux pump in S. pneumoniae that extrudes ethidium bromide and acriflavine but not fluoroquinolones.