Kiran S, Sharma P, Harjai K, Capalash N
Departments of Biotechnology.
Iran J Microbiol. 2011 Mar;3(1):1-12.
There is increasing emergence of multidrug resistant Pseudomonas aeruginosa (MDRPA) strains and drug resistance is positively-correlated with biofilm-forming ability. Since about 10% of P. aeruginosa genome is controlled by quorum sensing (QS), alteration in its antibiotic susceptibility by targeting QS was the focus of the present study.
One day biofilms of PAO1 and three urinary tract infection MDRPA isolates (PA2, PA8 and PA18) were formed in 96-well microtiter plate. Biofilms were exposed to concentration gradient of ciprofloxacin and gentamicin to obtain Minimum Biofilm Eradication Concentration (MBEC) by direct enumeration method. Susceptibility of 24 h biofilms was evaluated by treatment with ciprofloxacin and gentamicin per se and in combination with lactonase. The effect was also examined on 72 h biofilms by Scanning Electron Microscopy.
Lactonase treatment did not have any effect on growth of the selected strains but 73.42, 69.1, 77.34 and 72.5% reduction of biofilm was observed after lactonase (1 unit) treatment, respectively. Antibiotics in combination with lactonase (0.3 units) resulted in an increased susceptibility of the biofilm forms by>3.3, 4, 5 and 1.5 folds of MBEC, for ciprofloxacin and>6.67, 12.5, 6 and>2.5 folds, for gentamicin respectively, which could be due to the disruption of biofilm by lactonase treatment as shown by scanning electron microscopy. Also there was significant reduction (p<0.001) in virulence factor production by the strains.
Lactonase treatment increased antibiotic susceptibility of the biofilms of MDRPA isolates underscoring the potential of quorum quenching in antimicrobial therapeutics.
多重耐药铜绿假单胞菌（MDRPA）菌株不断出现，且耐药性与生物膜形成能力呈正相关。由于约10%的铜绿假单胞菌基因组受群体感应（QS）调控，因此本研究聚焦于通过靶向QS来改变其抗生素敏感性。
在96孔微量滴定板中形成PAO1及三株泌尿系统感染MDRPA分离株（PA2、PA8和PA18）的一日龄生物膜。将生物膜暴露于环丙沙星和庆大霉素的浓度梯度下，通过直接计数法获得最低生物膜清除浓度（MBEC）。用环丙沙星、庆大霉素单独及与内酯酶联合处理，评估24小时生物膜的敏感性。还通过扫描电子显微镜检查了对72小时生物膜的影响。
内酯酶处理对所选菌株的生长没有任何影响，但在内酯酶（1单位）处理后，分别观察到生物膜减少了73.42%、69.1%、77.34%和72.5%。抗生素与内酯酶（0.3单位）联合使用，使生物膜形式的敏感性分别提高至环丙沙星的MBEC的3.3倍、4倍、5倍和1.5倍以上，以及庆大霉素的6.67倍、12.5倍、6倍和2.5倍以上，这可能是由于扫描电子显微镜所示的内酯酶处理破坏了生物膜。此外，菌株的毒力因子产生也显著降低（p<0.001）。
内酯酶处理提高了MDRPA分离株生物膜的抗生素敏感性，突出了群体淬灭在抗菌治疗中的潜力。
