Volume 57, Issue 1 p. 115-124

Interaction of some polyhexamethylene biguanides and membrane phospholipids in Escherichia coli

P. Broxton

P. Broxton

Department of Pharmacy, University of Aston in Birmingham, Gosta Green, Birmingham B4 7ET.

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P.M. Woodcock

P.M. Woodcock

ICI Organics Division, Hexagon House, Blackley, Manchester

Departments of Pharmacy and Chemistry, University of Manchester, Manchester M13 9PL

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F. Heatley

F. Heatley

Departments of Pharmacy and Chemistry, University of Manchester, Manchester M13 9PL

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P. Gilbert

P. Gilbert

Departments of Pharmacy and Chemistry, University of Manchester, Manchester M13 9PL

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First published: August 1984
Citations: 145

Abstract

The interaction between some polyhexamethylene biguanides and the cell envelope of Escherichia coli has been investigated. An amine-ended dimer, (AED, n= 2), a polydisperse mixture (ICI plc) available as the active ingredient of Vantocil IB, (PHMB, n= 5.5), and a high molecular weight fraction, (HMW, n=≧ 10) of PHMB were used. The sensitivity of batch cultures depleted of magnesium (M-dep), phosphorus (P-dep) or glycerol (C-dep) towards the biocides was assessed by monitoring the rate and extent of potassium ion leakage. P-dep suspensions were particularly resistant to all these agents and possessed less than half the quantity of phospholipid of other cell types. This was compensated for by a proportionate increase in fatty acid and neutral lipid content of the cells. The reduction in phospholipid content was accounted for by decreases in phosphatidylglycerol (PG) and phosphatidylethanolamine (PE). Diphosphatidylglycerol (DPG) and phosphatidylserine (PS) content of the cultures remained unaffected by the depleting nutrient. Fourier-transform n.m.r. spectroscopy was used to study proton nuclei during the interaction of HMW, AED and PHMB with various phospholipid-vesicle preparations. The results strongly suggest that the biocides acted preferentially on the acidic phospholipids PG and DPG, rather than towards PE or PS. Resistance of P-dep cultures therefore reflected reductions in PG content. A molecular basis for the interaction of these compounds and membranes is proposed.