QAC action against Gram (-) bacteria

ARENA ME; SAVINO MJ; MANCA DE NADRA MC

BIOCELL

INCA

Lugar: Mendoza; Año: 2006 vol. 30 p. 173 - 173

0327-9545

Surface disinfection can control the dissemination of pathogens in the food industry. Quaternary ammonium compounds (QAC) are widely used as chemical disinfectant. The objective of this work is to study the effect of different concentrations of commercial QAC in the development of Escherichia coli and Pseudomonas aeruginosa. The assayed QAC concentrations in Luria culture media pH 4.9 and 7.0 were in v/v: 1/10000; 1/2000; 1/1000 and 1/500. Cell growth was determined spectrofotometricaly at 560nm and quantitatively by cfu/ml determination. The lowest concentration that inhibits both bacterial growths (MIC) was 1/2000 at pH 4.9. At pH 7.0, the MIC is 1/10000 for E. coli and 1/2000 for P. aeruginosa. When plated out, after the disinfection test, there are three possible microbial states: active cells, developed colonies at the same time than the control media (AC); inactivated cells, colonies are not observed (IC) and cells with a reversible injury, colonies were formed after prolonged storage (RI). The MIC of QAC at both pH values after 48 h incubation produces RI state in both microorganisms. The IC state was achieved with the maximal QAC concentration.  P. aeruginosa was more resistant than E. coli. It’s important to consider the presence of RI cells after the disinfection practices in order to avoid false negative results in the food industry.