Decreased membrane permeability in a polymyxin B-resistant Escherichia coli mutant exhibiting multiple resistance to β-lactams as well as aminoglycosides

Abstract A laboratory mutant of Escherichia coli stably resistant to more than 36 000 U ml−1 of polymyxin B was isolated. The mutant exhibited moderate increases in minimum inhibitory concentration to fluoroquinolones and bacitracin but high levels of cross-resistance to β-lactams and aminoglycoside...

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Bibliographic Details
Published in:FEMS microbiology letters 1998-04, Vol.161 (2), p.249-254
Main Authors: Rahaman, Sk.Ohidar, Mukherjee, Joydeep, Chakrabarti, Amit, Pal, Subrata
Format: Article
Language:English
Subjects:
Aminoglycosides
Bacitracin
Cefazolin
Cross-resistance
E coli
Escherichia coli
Fluoroquinolones
Lactose
Lipopolysaccharide
Lipopolysaccharides
Membrane permeability
Membrane proteins
Membranes
Microbiology
Minimum inhibitory concentration
Multiple resistance
Nalidixic acid
Norfloxacin
Novobiocin
Outer membrane protein
Outer membrane proteins
Permeability
Polymyxin B
Proteins
β-Lactam antibiotics
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Summary:Abstract A laboratory mutant of Escherichia coli stably resistant to more than 36 000 U ml−1 of polymyxin B was isolated. The mutant exhibited moderate increases in minimum inhibitory concentration to fluoroquinolones and bacitracin but high levels of cross-resistance to β-lactams and aminoglycosides. However, it remained susceptible to tetracycline, nalidixic acid and novobiocin. Changes were observed in the outer membrane proteins and lipopolysaccharide profile leading to a decrease in permeability as evident from reduction in the following: (i) minimum inhibitory concentration values in the presence of Tween 80, (ii) uptake of 1-N-phenyl naphthylamine and norfloxacin, (iii) hydrolysis of β-lactams and (iv) diffusion of lactose and cefazolin into proteoliposomes reconstituted with outer membrane proteins. We therefore suggest that the novel pattern of cross-resistance of our isolate is due to the decrease in its permeability.
ISSN:0378-1097
1574-6968
DOI:10.1111/j.1574-6968.1998.tb12955.x