Open AccessDecreased membrane permeability in a polymyxin B‐resistant Escherichia coli mutant exhibiting multiple resistance to β‐lactams as well as aminoglycosides
Author(s) -
Rahaman Sk.Ohidar,
Mukherjee Joydeep,
Chakrabarti Amit,
Pal Subrata
Publication year - 1998
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1998.tb12955.x
Subject(s) - escherichia coli , bacterial outer membrane , microbiology and biotechnology , tetracycline , polymyxin , polymyxin b , nalidixic acid , membrane permeability , mutant , novobiocin , chemistry , minimum inhibitory concentration , bacitracin , cephaloridine , norfloxacin , biology , biochemistry , antibiotics , membrane , ciprofloxacin , cephalosporin , gene
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.