Grupo de Micobactérias, Unidade de Microbiologia Médica, Instituto de Higiene e Medicina Tropical (IHMT), Universidade Nova de Lisboa, Rua da Junqueira 100, Lisbon, Portugal.
Int J Antimicrob Agents. 2012 Jan;39(1):16-21. doi: 10.1016/j.ijantimicag.2011.08.013. Epub 2011 Oct 5.
Thioridazine (TZ)-induced accumulation of the universal efflux pump substrate ethidium bromide and its subsequent efflux by Salmonella strains with various degrees of overexpressed efflux pumps takes place automatically at pH 7.4, is independent of a metabolic source, is not affected by a proton ionophore and is precluded by palmitic acid. Salmonella enterica serotype Enteritidis cultured in medium containing increasing concentrations of TZ does not grow during the first 6-8h, after which time its growth is similar to unexposed controls. At the end of a 16-h exposure period, the organism is resistant to >250mg/L TZ. Parallel assessment by real-time reverse transcription quantitative polymerase chain reaction (RT-qPCR) of the activity of genes that regulate and code for the AcrB transporter of the main efflux pump (AcrAB) of the organism at periodic intervals suggests a sequence of activation beginning with the stress gene soxS, followed by the global regulator ramA, then by the local regulator marA and then by the transporter acrB. These activations take place during the period of no growth. By the end of a 16-h culture period, only the acrB transporter gene is still highly overexpressed. Assessment of the activity of genes of the two-component regulon PmrA/B indicates that TZ also activates this regulon. Because activation of pmrA/B also activates acrB, development of high resistance to TZ during a 16-h culture period is in part due to activation of the two-component regulon.
噻氯匹定（TZ）诱导普遍外排泵底物溴化乙锭的积累，以及随后由具有不同程度过表达外排泵的沙门氏菌菌株将其外排，这在 pH 值为 7.4 时自动发生，独立于代谢源，不受质子载体影响，并被棕榈酸排除。在含有递增浓度 TZ 的培养基中培养的肠炎沙门氏菌血清型 Enteritidis 在最初的 6-8 小时内不会生长，之后其生长与未暴露的对照相似。在 16 小时暴露期结束时，该生物体对>250mg/L TZ 具有抗性。通过实时逆转录定量聚合酶链反应（RT-qPCR）平行评估调节和编码该生物体主要外排泵（AcrAB）的 AcrB 转运蛋白的基因活性，每隔一段时间提示一个从应激基因 soxS 开始的激活序列，随后是全局调节剂 ramA，然后是局部调节剂 marA，然后是转运蛋白 acrB。这些激活发生在无生长期间。在 16 小时培养期结束时，只有 acrB 转运蛋白基因仍高度过表达。对双组分调节子 PmrA/B 的基因活性的评估表明，TZ 还激活了该调节子。由于 pmrA/B 的激活也激活了 acrB，因此在 16 小时培养期间对 TZ 的高抗性的发展部分归因于双组分调节子的激活。
