@article{2566, keywords = {disinfection, bacteria, MIC, qualitative suspension test, carrier test}, author = {F Geber and M Reinhardt and M Kreuz and C Cuny and Y Pfeifer and U Truyen and S Speck}, title = {A comparison of different methods to determine disinfectant susceptibility of multidrug-resistant bacteria}, abstract = {The efficacy of Benzalkonium chloride (BAC), sodium hypochlorite, peracetic acid, glutaraldehyde, and ethanol against multidrug-resistant bacteria was assessed in a comprehensive three-step test series according to the guidelines of the German Veterinary Society. Bacteriostatic minimum inhibitory concentrations (MICs) and bactericidal concentrations were determined by broth macro-dilution, qualitative suspension tests and practical tests on stainless steel carriers without mechanical action. We examined whether the test method influences outcome with regard to bacterial biocide susceptibility or resistance. Marked differences in efficacious concentrations were noticed as a function of the test method and disinfectant applied resulting in increasing or decreasing values. This was most obvious for BAC as bactericidal values obtained by qualitative suspension tests were up to 100 times higher as compared to MICs whereas practical test results exceeded MICs 1,500-fold at maximum. Moreover, incubation time had a significant influence on bactericidal potency in practical tests. The effect of organic soiling on bactericidal concentrations was most striking for BAC and sodium hypochlorite. Our results underline that MIC determination and qualitative suspension tests are insufficient approaches to evaluate biocide susceptibility or resistance considerably regarding BAC. This highlights the necessity for standard methods that are suitable to assess biocide resistance for a broad range of disinfectants and allow for comparison between different studies.}, year = {2019}, journal = {Berliner und Münchener Tierärztliche Wochenschrift}, volume = {132}, month = {03/2019}, publisher = {Schlütersche Verlagsgesellschaft mbH & Co. KG}, address = {Hannover}, issn = {0005-9366}, doi = {10.2376/0005-9366-18047}, language = {English}, }