Characterisation of multidrug resistant Escherichia coli from poultry litter and poultry carrying virulence genes for evaluation of poultry farm management

In this study, antibiotic resistance and virulence genes and clonal relationships among Escherichia coli isolates from poultry litter and healthy poultry were investigated on a farm with previous outbreak of avian pathogenic E. coli (APEC) colisepsis, in order to establish a system for evaluating management practice and antibiotic use on poultry farms. Multidrug resistant strains were found in 78.3% (116/148) of tested cloacal swabs and in 100% (5/5) poultry litter E. coli isolates from each of the five poultry houses. The highest rate of resistance was to ampicillin and tetracycline , determined by presence of bla TEM and tet (A) genes. Conjugative transfer of resistance and virulence genes and the presence of integrons and integrases proved that the horizontal gene transfer was involved in the spread of multiresistant phenotypes among E. coli in poultry. Multidrug resistant transconjugant from E. coli isolate H4 from poultry litter carried iroN , ompT , hlyF , iss , iutA virulence genes, as well as bla TEM , aadA1 , aadA2 , sul1 and dfrA5/14 resistance genes and class 1 integron. Pulsed field gel electrophoresis (PFGE) typing distinguished multiple clones. This study demonstrated that poultry litter can serve as a reservoir of multidrug resistant E. coli, and resistotyping and virulence typing of poultry litter and/or isolates from poultry could be used to assess the quality of the management practice on poultry farms. Therefore, we propose a scoring system based on the number and ratio of resistance and virulence genes that can be used for evaluation of the quality of management practices on farms.