Department of Botany, University of Pune, Pune, India.
Indian J Med Res. 2010 Jul;132:94-9.
BACKGROUND & OBJECTIVES: The multiple drug resistance (MDR) is a serious health problem and major challenge to the global drug discovery programmes. Most of the genetic determinants that confer resistance to antibiotics are located on R-plasmids in bacteria. The present investigation was undertaken to investigate the ability of organic extract of the fruits of Helicteres isora to cure R-plasmids from certain clinical isolates.
Active fractions demonstrating antibacterial and antiplasmid activities were isolated from the acetone extracts of shade dried fruits of H. isora by bioassay guided fractionation. Minimal inhibitory concentration (MIC) of antibiotics and organic extracts was determined by agar dilution method. Plasmid curing activity of organic fractions was determined by evaluating the ability of bacterial colonies (pre treated with organic fraction for 18 h) to grow in the presence of antibiotics. The physical loss of plasmid DNA in the cured derivatives was further confirmed by agarose gel electrophoresis.
The active fraction did not inhibit the growth of either the clinical isolates or the strains harbouring reference plasmids even at a concentration of 400 microg/ml. However, the same fraction could cure plasmids from Enterococcus faecalis, Escherichia coli, Bacillus cereus and E. coli (RP4) at curing efficiencies of 14, 26, 22 and 2 per cent respectively. The active fraction mediated plasmid curing resulted in the subsequent loss of antibiotic resistance encoded in the plasmids as revealed by antibiotic resistance profile of cured strains. The physical loss of plasmid was also confirmed by agarose gel electrophoresis.
INTERPRETATION & CONCLUSIONS: The active fraction of acetone extract of H. isora fruits cured R-plasmids from Gram-positive and Gram-negative clinical isolates as well as reference strains. Such plasmid loss reversed the multiple antibiotic resistance in cured derivatives making them sensitive to low concentrations of antibiotics. Acetone fractions of H. isora may be a source to develop antiplasmid agents of natural origin to contain the development and spread of plasmid borne multiple antibiotic resistance.
多重耐药性（MDR）是一个严重的健康问题，也是全球药物发现计划面临的主要挑战。赋予抗生素耐药性的大多数遗传决定因素位于细菌的 R 质粒上。本研究旨在研究 Helicteres isora 果实的有机提取物消除某些临床分离株 R 质粒的能力。
通过生物测定指导的分步分离，从 H. isora 果实的丙酮提取物中分离出具有抗菌和抗质粒活性的活性馏分。通过琼脂稀释法测定抗生素和有机提取物的最小抑菌浓度（MIC）。通过评估用有机馏分预处理 18 小时的细菌菌落（pre treated with organic fraction for 18 h）在抗生素存在下生长的能力，确定有机馏分的质粒消除活性。通过琼脂糖凝胶电泳进一步证实了在被治愈的衍生物中质粒 DNA 的物理损失。
活性馏分即使在 400μg/ml 的浓度下也不会抑制临床分离株或携带参考质粒的菌株的生长。然而，相同的馏分可以分别以 14、26、22 和 2%的效率治愈粪肠球菌、大肠杆菌、蜡状芽孢杆菌和大肠杆菌（RP4）的质粒。活性馏分介导的质粒消除导致质粒编码的抗生素耐药性随后丧失，这通过被治愈的菌株的抗生素耐药谱揭示。琼脂糖凝胶电泳也证实了质粒的物理损失。
H. isora 果实丙酮提取物的活性馏分治愈了革兰氏阳性和革兰氏阴性临床分离株以及参考菌株的 R 质粒。这种质粒丢失使被治愈的衍生物对低浓度抗生素敏感，逆转了多重抗生素耐药性。H. isora 的丙酮馏分可能是开发天然来源的抗质粒剂的来源，以遏制质粒介导的多重抗生素耐药性的发展和传播。
