AUTHOR=Schwaiger Karin , Harms Katrin S., Bischoff Meike , Preikschat Petra , Mölle Gabriele , Bauer-Unkauf Ilse , Thalhammer Sandra , Bauer Johann , Hölzel Christina S.

TITLE=Insusceptibility to disinfectants in bacteria from animals, food and humans—is there a link to antimicrobial resistance?

JOURNAL=Frontiers in Microbiology

VOLUME=5

YEAR=2014

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2014.00088

DOI=10.3389/fmicb.2014.00088

ISSN=1664-302X

ABSTRACT=<p><italic>Enterococcus faecalis</italic> (<italic>n</italic> = 834) and <italic>Enterococcus faecium</italic> (<italic>n</italic> = 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 &gt; 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 <italic>E. faecium</italic> (<italic>p</italic> &lt; 0.05). No indications for a common source of non-wildtype strains were found by RAPD-PCR; however, several non-wildtype <italic>E. faecalis</italic> shared the same variant of the <italic>eme</italic>A-gene. In addition, bacteria (<italic>n</italic> = 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 <italic>E. faecium</italic>—should be substantiated in further studies and might be an additional reason to confine the use of antibiotics.</p>