Different surface charge of colistin-susceptible and -resistant Acinetobacter baumannii cells measured with zeta potential as a function of growth phase and colistin treatment.

Article Details

Citation

Copy to clipboard

Soon RL, Nation RL, Cockram S, Moffatt JH, Harper M, Adler B, Boyce JD, Larson I, Li J

Different surface charge of colistin-susceptible and -resistant Acinetobacter baumannii cells measured with zeta potential as a function of growth phase and colistin treatment.

J Antimicrob Chemother. 2011 Jan;66(1):126-33. doi: 10.1093/jac/dkq422. Epub 2010 Nov 16.

PubMed ID

21081544 [ View in PubMed

]

Abstract

OBJECTIVES: electrostatic forces mediate the initial interaction between cationic colistin and Gram-negative bacterial cells. Lipopolysaccharide (LPS) loss mediates colistin resistance in some A. baumannii strains. Our aim was to determine the surface charge of colistin-susceptible and -resistant A. baumannii as a function of growth phase and in response to polymyxin treatment. METHODS: the zeta potential of A. baumannii ATCC 19606 and 10 clinical multidrug-resistant strains (MICs 0.5-2 mg/L) was assessed. Colistin-resistant derivatives (MIC >128 mg/L) of wild-type strains were selected in the presence of 10 mg/L colistin, including the LPS-deficient lpxA mutant, ATCC 19606R. To determine the contribution of LPS to surface charge, two complemented ATCC 19606R derivatives were examined, namely ATCC 19606R + lpxA (containing an intact lpxA gene) and ATCC 19606R + V (containing empty vector). Investigations were conducted as a function of growth phase and polymyxin treatment (1, 4 and 8 mg/L). RESULTS: wild-type cells exhibited a greater negative charge (-60.5 +/- 2.36 to -26.2 +/- 2.56 mV) thancolistin-resistant cells (-49.2 +/- 3.09 to -19.1 +/- 2.80 mV) at mid-log phase (ANOVA, P < 0.05). Opposing growth-phase trends were observed for both phenotypes: wild-type cells displayed reduced negative charge and colistin-resistant cells displayed increased negative charge at stationary compared with mid-logarithmic phase. Polymyxin exposure resulted in a concentration-dependent increase in zeta potential. Examination of ATCC 19606R and complemented strains supported the importance of LPS in determining surface charge, suggesting a potential mechanism of colistin resistance. CONCLUSIONS: zeta potential differences between A. baumannii phenotypes probably reflect compositional outer-membrane variations that impact the electrostatic component of colistin activity.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Colistimethate	Bacterial outer membrane	Group	Bacteria	Yes	Incorporation into and destabilization	Details
Colistin	Bacterial outer membrane	Group	Bacteria	Yes	Incorporation into and destabilization	Details