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

Abstract

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 percentage of cases of antibiotic resistance). The antibiogram (Kirby-Bauer) was determined and, in parallel, 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 equivalent (sterile cotton cloth) in 30 sec, for two alcohol solutions. A predictive equation of the bactericidal 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 microorganisms: "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 antiseptics or disinfectants in ICUs, except if aztreonam resistance is high. In which case is better to use greater concentration than 1% of Chlorhexidine.

An interesting increase in immediate and residual efficacy of a trade mark of alcoholic 2% chlorhexidine gluconate, with and without dye, has been demonstrated by an in vitro study with ATCC micro‐organisms and strains isolated from ICU patients

“…In parallel, cotton germ‐carriers (which give very similar results to the skin of a corpse or a lyophilized pig skin, and also correlate with the ‘in vivo’ results in humans) (Herruzo et al ; Herruzo et al ; Herruzo et al ; Herruzo et al ; Herruzo et al ) cut into circles of 0·5 cm diameter and sterilized by steam flow were impregnated with 10 µl of a microbial suspension. They were left to dry for 30 min and then 10 µl of antiseptic or sterile distilled water were added, the latter acting as the control for antiseptics.…”

“…A recent study found two‐thirds of 159 micro‐organisms isolated from ICU patients (Herruzo et al ), had a CHG MIC >32 ppm (some with MIC >100 ppm). However, this did not influence its bactericidal effect.…”

“…Antiseptic inhibitor (Herruzo‐Cabrera et al, ; Herruzo et al, ; Herruzo et al, ; Herruzo et al, ; Herruzo et al, ): Nutrient Broth (Lab BD) containing 6% Tween80 (Lab Panreac. Castellar del Vallés, Barcelona, Spain), 0·5% sodium bisulphite (Lab Panreac) and 0·5% sodium thiosulphate (Lab Panreac) serves to inhibit the action of the antiseptics or disinfectants.…”

“…They were left to dry for 30 min and then 10 µl of antiseptic or sterile distilled water were added, the latter acting as the control for antiseptics. The antiseptic or control was left to act for 30 s or 1 min after which its potential antimicrobial action was inhibited by submerging each carrier in a tube containing 1 ml of the antiseptic inhibitor described above (Herruzo et al ; Herruzo et al ; Herruzo et al ; Herruzo et al ; Herruzo et al ). Subsequently, each tube was shaken with its carrier for 1 min after which two 100 µl neat or diluted (1 : 100) aliquots were cultured onto blood, MacConkey or Sabouraud dextrose agar plates.…”