Avian pathogenic Escherichia coli (APEC) causes huge annual losses in the poultry industry worldwide. Multiresistance against antibiotics of APEC strains is increasingly seen in broilers, although much is still unknown about strains from laying hens where use of antibiotics is limited. Disinfection can reduce the infection burden. However, little is known about the presence of resistance against these products. Ninety-seven APEC strains were isolated from Belgian laying hens. The resistance to different classes of antibiotics was determined as well as the minimum inhibitory concentrations (MIC; agar and broth dilution) and minimum bactericidal concentrations (MBC) of five disinfectants most often used in the poultry industry (formaldehyde, glutaraldehyde, glyoxal, hydrogen peroxide, and a quaternary ammonium compound). The presence of integrons was determined by PCR Resistance to ampicillin (35.1%), nalidixic acid (38.1%), sulfonamides (SULFA, 41.2%), and tetracycline (TET, 53.6%) was high but resistance to other tested antibiotics was low. Nevertheless, two extended spectrum beta-lactamase producers were found. The MIC of the disinfectants for the APEC strains showed a Gaussian distribution, indicating that there was no acquired resistance. MBCs were similar to MICs via the broth dilution method, showing the bactericidal effect of the disinfectants. Twenty-one strains (21.6%) were found positive for class 1 integrons and a positive association between integron presence and resistance to trimethoprim, SULFA, and TET was found. No association could be found between integron presence and phylogenetic group affiliation. Susceptibility of APEC strains from laying hens to antibiotics is, in general, very high. Phenotypic resistance to commonly used disinfectants could not be found, indicating that the current use of disinfectants in the laying hen industry did not select for resistance.
BackgroundAvian pathogenic Escherichia coli (APEC) are the major cause of economic losses in the poultry industry worldwide. Traditionally, antibiotics are used to treat and prevent colibacillosis in broilers. Due to resistance development other ways of preventing/treating the disease have to be found. Therefore during this study the nebulization of low concentrations of hydrogen peroxide (H2O2) was tested in the presence of chickens to lower pathogenicity of APEC.ResultsSignificantly higher total lesion scores and higher E. coli concentrations were found in the spleen of chickens exposed to 2 % H2O2 compared to those exposed to 1 % H2O2 and control chickens which had been exposed to nebulization with distilled water. Higher total lesions scores and E. coli concentrations in the spleen were found in chickens exposed to 1 % H2O2 in comparison to control chickens (not significant).ConclusionH2O2 is rendering animals more prone to APEC infection contraindicating H2O2 nebulization in the presence of chickens.
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