Association of qacE and qacEΔ1 with multiple resistance to antibiotics and antiseptics in clinical isolates of Gram-negative bacteria

Clinical isolates of Enterobacter cloacae, Citrobacter freundii, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia were tested for resistance to antibiotics and to the antiseptics benzalkonium chloride and cetyltrimethylammonium bromide. Furthermore, they were examined for the presence of the resistance genes qacE and qacE Delta 1. qacE Delta 1 was detected by PCR in 10% of all (n = 103) and in 81% of multiply antibiotic-resistant strains (n = 15). qacE was found in only one of 37 P. aeruginosa strains. The minimum inhibitory concentrations of benzalkonium chloride, cetyltrimethylammonium bromide, and ethidium bromide were not significantly different for qacE Delta 1/qacE-positive or -negative strains. Our data indicate that multiply antibiotic-resistant Gram-negative bacteria are not necessarily more resistant to quaternary ammonium compounds than antibiotic-sensitive strains even though qacE or qacE Delta 1 is present. (C) 2000 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.