革兰氏阴性菌如大肠埃希氏菌造成的细菌感染，通常对于二种以上的抗生素具有抗药性。由于使用新的抗生素无法消除多重抗药性的问题，所以这种类型的感染成为了重大的健康威胁，特别是院内感染的患者。
多重抗药性成为了许多研究人员的研究目标。最近由一组美国、葡萄牙和法国科学家组成的研究小组，辨认导致革兰氏阴性菌多重抗药性表型的基因事件顺序。
这项研究名为「大肠杆菌的抗生素紧迫、基因反应和改变的渗透性」将发表于4月11 日的Public Library of Science, PLoS ONE中。
当大肠杆菌暴露于浓度越来越高的四圜素时，会使调控基因的活性越来越高，而促进9种不同具排出功能的运输蛋白质的基因表现，使抗生素达到作用的目标前，就被运出细菌之外。
因活动同时进行的，还包括随着抗生素的紧迫增加，外膜的porin蛋白质Omp F 和C会被蛋白酶分解并减少，同时，Omp x 的含量会持续地增加。
研究作者表示，这是第一项研究证实，长时间暴露于抗生素，会使细菌的排出泵浦表现，因此造成细菌的渗透性改变。
(资料来源 : biocompare)
原始出处:
Antibiotic Stress, Genetic Response And Altered Permeability Of E. Coli
4/10/2007
Source: Public Library of Science
Bacterial infections caused by Gram-negative bacteria such as Escherichia coli are frequently resistant to two or more antibiotics (multi-drug resistant). Because introduction of new antibiotics will not eliminate the problem of multi-drug resistance (mdr), mdr type infections constitute a major health threat, especially to patients that acquire such infections nosocomially. The manner by which mdr develops has become an area of intense research and the recent investigations conducted by an international group consisting of American, Portuguese and French scientists have identified the genetic sequence of events that lead to mdr phenotypes of Gram-negative bacteria.
The study, entitled "Antibiotic Stress, Genetic Response and Altered Permeability of E. coli," will be published the 11th April issue of the international, peer-reviewed, open-access online journal of the Public Library of Science, PLoS ONE.
Briefly, prolonged exposure to increasing concentrations of tetracycline cause increased sequential activity of regulatory genes which promote over-expression of genes that code for as many as 9 transporter proteins of distinct efflux pumps which extrude unrelated antibiotics prior to their reaching their intended targets. Parallel to this genetic activity, whereas the level of outer membrane porin proteins Omp F and C decrease with increased antibiotic stress, the level of Omp X continues to increases dramatically. The decrease of Omp C and F appears to result from their being degraded by proteases inasmuch as the activity of genes that code for these proteins are also significantly elevated during prolonged antibiotic stress.
The authors of this study maintain that this is the first time that the response to prolonged exposure to increasing levels of antibiotic cause major changes in the permeability of the bacterium due to over-expression of efflux pumps and down-regulation of porins.
