期刊
JOURNAL OF ANTIMICROBIAL CHEMOTHERAPY
卷 66, 期 1, 页码 126-133出版社
OXFORD UNIV PRESS
DOI: 10.1093/jac/dkq422
关键词
physicochemical properties; Gram-negative; polymyxin
资金
- Australian National Health and Medical Research Council (NHMRC)
- National Institute of Allergy and Infectious Diseases of the National Institutes of Health [R01A1070896, R01AI079330]
- NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES [R01AI079330, R01AI070896] Funding Source: NIH RePORTER
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. 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). 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. Zeta potential differences between A. baumannii phenotypes probably reflect compositional outer-membrane variations that impact the electrostatic component of colistin activity.
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