Experimental studies on membrane permeability defects of drug-resistant bacteria.

Multiply antibiotic-, lysozyme-and bacitracin-resistant, representative strains of staphylococci, Escherichia coli, Shigella dysenteriae and Klebsiella pneumoniae were compared respectively with their parent cultures in respect of their membrane permeability as judged by fluorescence polarization spectroscopy, using a sensitive fluorescent probe. The cytoplasmic membrane of the drug-resistant mutants was found to be less fluid and permeable, compared to that from the sensitive wild types. The study constitutes an attempt to determine the physical basis for the mechanism of resistance of certain bacteria against certain drugs.