Abstract
We investigated the suitability of a newly developed biocide susceptibility test system based on microtiter plates containing vacuum dried biocides as a fast and reliable screening method. The evaluated substances included the cationic biocides benzalkonium chloride (BAC), chlorhexidine dihydrochloride (CHX), cetylpyridinium chloride, didecyldimethylammonium chloride, and octenidine dihydrochloride. Testing a selection of Escherichia coli and enterococci, the biocide microtiter plates provided results comparable to those obtained from broth microdilution according to ISO 20776-1. Broad MIC ranges allowed for testing gram-positive and gram-negative species with the same plate design. In the second part of our study, we applied the established method to analyze the susceptibility of 90 clinical Enterococcus faecium isolates from a German university hospital, as previous studies have indicated a link between reduced susceptibility to substances such as CHX and BAC and vancomycin resistance. We therefore determined MIC and minimum bactericidal concentrations (MBC) for 48 non-clonal vancomycin susceptible and 42 non-clonal vancomycin resistant isolates, but MIC95 and MBC95 were quite similar in both groups. Our easy to handle and ready to use test system enables the routine surveillance of bacterial tolerance towards disinfectants in hospitals. As a result, hygiene measures can be adapted and nosocomial infections controlled despite increasing prevalence of antibiotic-resistant bacteria.
Highlights
In the era of multidrug resistance with a rising number of infections unresponsive to antibiotic treatment, the relevance of hygiene measures to reduce bacterial burden and transmission in clinical settings has significantly increased [1]
The MIC values determined with the customized vacuum dried biocide microtiter plate were within the acceptable range of ± one doubling dilution step compared to the modal values obtained with a broth microdilution method according to ISO 20776-1 (EA = 100% for all isolate-substance combinations)
We explored the suitability of a newly developed biocide susceptibility test system based on microtiter plates containing vacuum dried biocides as a screening method to identify bacteria resistant to cationic substances frequently used in hospital settings
Summary
In the era of multidrug resistance with a rising number of infections unresponsive to antibiotic treatment, the relevance of hygiene measures to reduce bacterial burden and transmission in clinical settings has significantly increased [1]. We have reported a polyclonal outbreak with Serratia marcescens on a neonatology ICU [8] These isolates exhibited resistance to 0.5% Mikrobac forte® consisting of benzyl-C12-18-alkyl dimethyl ammonium chloride 199 mg/g and N-(3-aminopropyl)-N-dodecylpropane-1,3-diamine 50 mg/g, which was used for disinfection of surfaces before the outbreak. One of the measures in the bundle that successfully contained this outbreak consisted of increasing the concentration of used Mikrobac forte® to 2% Outcomes of these studies point towards the need for regular monitoring of bacterial biocide susceptibility profiles. A test plate system containing predefined concentrations of biocidal substances would be preferable for routine screening of bacterial susceptibility profiles to biocides of interest. The first aim of our study was to evaluate the comparability of susceptibility profiles for chosen biocides obtained with broth microdilution method according to ISO 20776-1 and a newly developed microtiter-plate containing vacuum dried cationic biocides (MERLIN Diagnostika GmbH, Bornheim-Hersel, Germany). We used the novel test system to determine biocide susceptibility of vancomycin-resistant (VRE) and susceptible enterococci (VSE) as vancomycin resistance has been linked to reduced susceptibility to cationic biocides such as CHX and benzalkonium chloride (BAC) in the past [13,14]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
