Clinical isolates of Staphylococcus aureus carry various antiseptic and disinfectant resistance determinants (qac genes) on a variety of plasmids. The biochemistry and specificity of these resistance genes in S. aureus is the subject of this report. The qac genes were separated into two families on the basis of resistance profiles and DNA homology. Isotopic and fluorimetric assays demonstrated that the qac genes encode efflux systems that rely on proton motive force.

Escherichia coli strains bind to Gal alpha 1-4Gal-containing glycolipids via P pili-associated G-adhesins. Three functional classes of adhesins with different binding specificities are encoded by conserved G-alleles. We suggest that the Class I papG-allele of strain J96 is a novel acquisition possibly introduced via horizontal gene transfer into one of the two P pili gene clusters carried by this strain. Closely related strains in the ECOR collection of natural E. coli isolates carry either a Class II or a Class III G-adhesin. Data indicate that genetic exchanges involving either entire pap or prs gene clusters or individual pap/prs genes have occurred. We propose that the retention and spread of pap/prs DNA among E. coli is the result of selection pressure exerted by mammalian intestinal isoreceptors.

Most uropathogenic strains of Escherichia coli produce heteropolymeric organelles, known as P pili, that bind to the globoseries of glycolipids present in the urinary tract. The formation of a P pilus is the result of a family of related proteins being coordinately assembled into the structure in a defined order with the adhesin located exclusively at the tip. The preassembled digalactoside a-D-galactopyranosyl-(1--4)-.8-D-galactopyranose-binding adhesin was purified to homogeneity from the periplasmic space in a complex with the