title: Insusceptibility to disinfectants in bacteria from animals, food and humans-is there a link to antimicrobial resistance?
abstract: Enterococcus faecalis (n = 834) and Enterococcus faecium (n = 135) from blood and feces of hospitalized humans, from feces of outpatients and livestock and from food were screened for their susceptibility to a quaternary ammonium compound (didecyldimethylammoniumchloride, DDAC) and to 28 antibiotics by micro-/macrodilution. The maximum DDAC-MIC in our field study was 3.5 mg/l, but after adaptation in the laboratory, MIC values of 21.9 mg/l were observed. Strains for which DDAC had MICs > 1.4 mg/l ("non-wildtype," in total: 46 of 969 isolates/4.7%) were most often found in milk and dairy products (14.6%), while their prevalence in livestock was generally low (0-4%). Of human isolates, 2.9-6.8% had a "non-wildtype" phenotype. An association between reduced susceptibility to DDAC, high-level-aminoglycoside resistance and aminopenicillin resistance was seen in E. faecium (p < 0.05). No indications for a common source of non-wildtype strains were found by RAPD-PCR; however, several non-wildtype E. faecalis shared the same variant of the emeA-gene. In addition, bacteria (n = 42) of different genera were isolated from formic acid based boot bath disinfectant (20 ml of 55% formic acid/l). The MICs of this disinfectant exceeded the wildtype MICs up to 20-fold (staphylococci), but were still one to three orders of magnitude below the used concentration of the disinfectant (i. e., 1.1% formic acid). In conclusion, the bacterial susceptibility to disinfectants still seems to be high. Thus, the proper use of disinfectants in livestock surroundings along with a good hygiene praxis should still be highly encouraged. Hints to a link between antibiotic resistance and reduced susceptibility for disinfectants-as seen for E. faecium-should be substantiated in further studies and might be an additional reason to confine the use of antibiotics.
authors.affiliation: Animal Hygiene, Wissenschaftszentrum Weihenstephan für Ernährung, Landnutzung und Umwelt, Technische Universität München Freising, Germany.
authors.forename: Karin
authors.initials: K
authors.lastname: Schwaiger
authors.affiliation: Animal Hygiene, Wissenschaftszentrum Weihenstephan für Ernährung, Landnutzung und Umwelt, Technische Universität München Freising, Germany.
authors.forename: Katrin S
authors.initials: KS
authors.lastname: Harms
authors.affiliation: Animal Hygiene, Wissenschaftszentrum Weihenstephan für Ernährung, Landnutzung und Umwelt, Technische Universität München Freising, Germany.
authors.forename: Meike
authors.initials: M
authors.lastname: Bischoff
authors.affiliation: Bavarian Health and Food Safety Authority (LGL) Erlangen, Germany.
authors.forename: Petra
authors.initials: P
authors.lastname: Preikschat
authors.affiliation: Bavarian Health and Food Safety Authority (LGL) Erlangen, Germany.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Mölle
authors.affiliation: Bavarian Health and Food Safety Authority (LGL) Erlangen, Germany.
authors.forename: Ilse
authors.initials: I
authors.lastname: Bauer-Unkauf
authors.affiliation: Animal Hygiene, Wissenschaftszentrum Weihenstephan für Ernährung, Landnutzung und Umwelt, Technische Universität München Freising, Germany.
authors.forename: Solveig
authors.initials: S
authors.lastname: Lindorfer
authors.affiliation: Animal Hygiene, Wissenschaftszentrum Weihenstephan für Ernährung, Landnutzung und Umwelt, Technische Universität München Freising, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Thalhammer
authors.affiliation: Animal Hygiene, Wissenschaftszentrum Weihenstephan für Ernährung, Landnutzung und Umwelt, Technische Universität München Freising, Germany.
authors.forename: Johann
authors.initials: J
authors.lastname: Bauer
authors.affiliation: Animal Hygiene, Wissenschaftszentrum Weihenstephan für Ernährung, Landnutzung und Umwelt, Technische Universität München Freising, Germany.
authors.forename: Christina S
authors.initials: CS
authors.lastname: Hölzel
keywords: QAC; aminoglycoside; antimicrobial resistance; antiseptic; biocide; disinfectant; enterococci; formic acid