02281nas a2200265   4500000000100000000000100001008004100002260007000043653001700113653001300130653000800143653003200151653001700183100001200200700001600212700001200228700001100240700001400251700001300265700001200278245011100290490000800401520159200409022001402001       2019                            d  c03/2019bSchlütersche Verlagsgesellschaft mbH & Co. KGaHannover10adisinfection10abacteria10aMIC10aqualitative suspension test10acarrier test1 aF Geber1 aM Reinhardt1 aM Kreuz1 aC Cuny1 aY Pfeifer1 aU Truyen1 aS Speck00aA comparison of different methods to determine disinfectant susceptibility of multidrug-resistant bacteria0 v1323 aThe 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.  a0005-9366