Antimicrobial susceptibility of starter culture bacteria used in Norwegiandairy products

Commercial starter culture bacteria are widely used in the production of da iry products and could represent a potential source for spread of genes enc oding resistance to antimicrobial agents. To learn more about the antimicro bial susceptibility of starlet culture bacteria used in Norwegian dairy pro ducts, a total of 189 isolates of lactic acid bacteria were examined for su sceptibility to ampicillin, penicillin G, cephalothin, vancomycin, bacitrac in, gentamicin, streptomycin, erythromycin, tetracycline, chloramphenicol, quinupristin/dalfopristin, ciprofloxacin, trimethoprim and sulphadiazine us ing Etest for MIC determination. Most of the isolates (140) originated from 39 dairy products (yoghurt, sour cream, fermented milk and cheese), while 49 were isolated directly from nine commercial cultures. The bacteria belon ged to the genera Lactobacillus, Lactococcus, Leuconostoc and Streptococcus Only one of the 189 isolates was classified as resistant to an antimicrobia l agent included in the study. This isolate, a lactobacillus, was classifie d as high level resistant to streptomycin. The remaining isolates were not classified as resistant to the antimicrobial agents included other than to those they are known to have a natural reduced susceptibility to. Thus, sta rter culture bacteria in Norwegian dairy products do not seem to represent a source for spread of genes encoding resistance to antimicrobial agents. ( C) 2001 Elsevier Science B.V. All rights reserved.