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Disinfectants are widely used in different areas and an inappropriate use might cause the emergence of disinfectantresistances,
leading to further disinfection failure. Beyond this, the co-selection of disinfectant- and antibiotic- resistance
has been reported in case of various bacteria. Due to the fact that the presence of ESBL/ AmpC dramatically
limits the therapeutic options, the appearance of disinfectant-resistances in these kinds of bacteria might contribute a
health thread for humans as well as animals.
Materials and Methods
90 ESBL-/ AmpC-producing E. coli, isolated from cloacal swabs of chicken out of seven broiler fattening flocks
throughout Germany were investigated. For each strain the minimal inhibitory concentration (MIC) of three different
disinfectants – Benzalkonium chloride (BKC), Chlorhexidine (CHX) and Triclosan (TCL) was determined. In addition,
the presence of 5 different qac genes (qacE, qacEΔ1,qacH, qacF and qacG) was investigated.
Compared to three E. coli reference strains, 23 samples showed decreased susceptibility to single or multiple disinfectants
(8/CHX; 7/TCL; 3/BKC+CHX; 5/CHX+TCL). However, none of the strains was able to survive at concentrations
recommended for disinfection with commercially available products.
The qacEΔ1 gene was found in 18.89% samples, the frequency of qacH 6.67% was low while qacE, qacF and qacG
were not detected. However, all isolates showing an increased MIC against BKC contain none of the investigated
qac genes, whereas three BKC sensitive isolates contain qacH as well as qacEΔ1 genes.
ESBL-/ AmpC- producing E. coli possessing decreased susceptibility to disinfectants have been detected within
chicken in German broiler fatting farms. However, none of the detected MIC values indicate that accurately performed
disinfection procedures will lead to ineffectiveness. In addition, no correlation between the presence of qac
genes and the increased disinfectant tolerance has been observed.