School of Biological Sciences, University of the Punjab, Lahore, Pakistan.
Institute of Biochemistry and Biotechnology, University of the Punjab, Lahore, Pakistan.
Microb Pathog. 2020 Dec;149:104491. doi: 10.1016/j.micpath.2020.104491. Epub 2020 Sep 14.
Pseudomonas aeruginosa harbors pvcABCD operon that is responsible for the synthesis of paerucumarin. Here we report the involvement of pvcABCD operon in chloramphenicol and ciprofloxacin resistance. P. aeruginosa mutant defective in pvcB (PW4832) was more sensitive to chloramphenicol and ciprofloxacin in comparison with its parent strain (MPAO1). A mutation in pvcA gene in MPAO1 (PW4830) did not alter the sensitivity to either antibiotic. As chloramphenicol and ciprofloxacin are substrates of MexEF-OprN efflux pump, so we decided to investigate the modulation of MexEF-OprN and its transcriptional regulator MexT in PW4832, PW4830 and MPAO1 strains. We isolated and sequenced mexT gene from MPAO1, PW4830 and PW4832. The nucleotide sequence of mexT gene in all three strains was identical. Expression levels of mexEF-oprN, mexT and mexS genes were checked via quantitative real-time RT-PCR. All these genes showed significant repression in mRNA levels in PW4832 as compared to MPAO1. These results indicate that chloramphenicol and ciprofloxacin sensitivity in PW4832 is due to transcriptional repression of mexT and mexEF-oprN genes. Exogenous addition of paerucumarin resumed the expression of mexT and mexEF-oprN genes as well as resistance against chloramphenicol and ciprofloxacin in PW4832 strain. This is a novel finding linking pvcB gene of P. aeruginosa with chloramphenicol and ciprofloxacin resistance and MexEF-OprN pump modulation which needs to be further explored.
铜绿假单胞菌含有 pvcABCD 操纵子，负责合成帕鲁卡霉素。在这里，我们报告了 pvcABCD 操纵子在氯霉素和环丙沙星耐药中的作用。与亲本菌株（MPAO1）相比，pvcB 缺陷型铜绿假单胞菌突变体（PW4832）对氯霉素和环丙沙星更为敏感。MPAO1 中的 pvcA 基因突变（PW4830）并未改变对任何一种抗生素的敏感性。由于氯霉素和环丙沙星是 MexEF-OprN 外排泵的底物，因此我们决定研究 PW4832、PW4830 和 MPAO1 菌株中 MexEF-OprN 及其转录调节剂 MexT 的调节作用。我们从 MPAO1、PW4830 和 PW4832 中分离并测序了 mexT 基因。这三个菌株的 mexT 基因的核苷酸序列完全相同。通过定量实时 RT-PCR 检查了 mexEF-oprN、mexT 和 mexS 基因的表达水平。与 MPAO1 相比，所有这些基因在 PW4832 中的 mRNA 水平均显著下调。这些结果表明，PW4832 中氯霉素和环丙沙星的敏感性归因于 mexT 和 mexEF-oprN 基因的转录抑制。外源性添加帕鲁卡霉素恢复了 PW4832 中 mexT 和 mexEF-oprN 基因的表达以及对氯霉素和环丙沙星的耐药性。这是一个新的发现，将铜绿假单胞菌的 pvcB 基因与氯霉素和环丙沙星耐药性以及 MexEF-OprN 泵调节联系起来，这需要进一步探索。
