It’s Possible to Predict a Decreased Bactericidal Effect of Biocides, through Antibiotic Resistance in ICU: Study Using a Large Sample of Bacteria and Multivariate Analysis

Objective: To determine whether there was any association between resistance to antibiotics and decreased susceptibility to antiseptics and disinfectants and their importance in clinical practice. Methods: We studied a large number of microorganisms isolated from ICU patients (high percent- age of cases of antibiotic resistance). The antibiogram (Kirby-Bauer) was determined and, in par- allel, the bactericidal effect was assessed by two methods, according to the product used: 1) Effect on rough material (endodontic files) in 10 min, using five disinfectants; 2) Effect on a skin equiva- lent (sterile cotton cloth) in 30 sec, for two alcohol solutions. A predictive equation of the bacteri- cidal effects versus microorganisms' antibiogram was obtained by multivariate methods. Results: Bactericidal efficacy was very similar for all the products with the exception of 1% povidone-iodine. Within each product there were no significant differences between the three groups of microor- ganisms: "Enterobacteria", "Non Fermentative Gram Negative Bacteria" and "cocci". Multivariate study only obtained one significant equation: 1% chlorhexidine resistance was directly correlated with aztreonam resistance (OR = 2.16), while resistance to imipenem and to phosphomycin acted as protection factors (OR < 1). Conclusion: There is no necessary to change the indications for an- tiseptics or disinfectants in ICUs, except if aztreonam resistance is high. In which case is better to use greater concentration than 1% of Chlorhexidine. * Corresponding author.