Recent studies have demonstrated that under laboratory conditions, exposure of organisms to quaternary ammonium disinfectants may develop resistance to antibiotics. Potential pathogens frequently found in water treatment plants such as Pseudomonas aeroginosa exposed to alkyl-dimethylbenzyl-ammonium chloride develop resistance to penicillin, tetracycline and ciprofloxacin.   Exposure can alter sensitivity to antibiotics as illustrated by an isolate of Pseudomonas derived from a mid-western lake that became resistant to ciprofloxacin but more susceptible to streptomycin following exposure.

It is important for scientists working in the field of environmental bacteriology to determine the actual levels of quaternary ammonium disinfectants in the waters they study and relate these to concentrations used in food production and medical facilities to ascertain whether laboratory results are relevant to the real world.

Resistance of pathogens to Quaternary ammonium compounds is instinctively of significance in hatcheries and egg-packing plants if a single class of disinfectant is used for extended periods without appropriate microbiologic monitoring.