Cross-resistance to antibiotics of Escherichia coli adapted to benzalkonium chloride or exposed to stress-inducers.

Aims: To study the effects of adaptation and stress on the resistance to benzalkonium chloride (BC) and cross-resistance to antibiotics in Escherichia coli.

Methods And Results: Precultivation of E. coli ATCC 11775 and E.

Intrinsic and acquired resistance to quaternary ammonium compounds in food-related Pseudomonas spp.

Aims: To determine the sensitivity of a strain used for disinfectants testing (Pseudomonas aeruginosa ATCC 15442) and food-associated isolates to benzalkonium chloride and didecyl dimethylammonium chloride (DDAC). To determine whether the increase in bacterial resistance after adaptation to DDAC can be associated with phenotypic changes. To test the activity of alternative disinfectants to eliminate resistant Pseudomonas spp.

Characterization of Serratia marcescens surviving in disinfecting footbaths.

Aim: To determine if disinfecting footbaths in the food industry were contaminated with bacteria and to characterize some of the bacteria present.

Methods And Results: Bacterial strains were isolated from disinfecting footbaths containing TEGO 103G (amphoteric disinfectant) or TP-99 (alkyl amino acetate-based disinfectant) in five of six dairy factories. Fourteen strains identified as Cedecea spp.

Occurrence of and a possible mechanism for resistance to a quaternary ammonium compound in Listeria monocytogenes.

In a study of 200 Listeria monocytogenes isolates, 10% were determined to be resistant to benzalkonium chloride (BC). Serial subcultivation of initially BC sensitive (BC(S)) and BC resistant (BC(R)) isolates in sublethal concentrations of BC resulted in enhanced and approximately equal resistance of all strains to the compound. Fifty per cent of the BC(R) isolates showed resistance to ethidium bromide (EB) as well.

Potentiation of the lethal effect of peroxygen on Bacillus cereus spores by alkali and enzyme wash.

Bacillus cereus present in pipes and heat-exchangers represents a potential quality problem for dairy industry. The peroxygen-containing disinfectants investigated had only negligible sporicidal effect when applied at the recommended in-use temperature and concentration. However, cleaning agents used before disinfection potentiated their lethal activity.