Trends in antimicrobial resistance phenotypes in non-typhoid Salmonellae from human and poultry origins in France

A total of 1873 strains from human origin and 4283 strains from non-human origin of Salmonella enterica serotypes Typhimurium, Enteritidis, Heidelberg, Hadar and Virchow, collected over three years 1993, 1997 and 2000, were examined in order to determine the rate of antimicrobial resistance to 12 antimicrobial drugs. The objective of the study was to describe and to compare the evolution of the main resistance types in human and non-human isolates, focusing on the poultry sector. The evolution and the rates of antimicrobial resistances for the five serotypes, with the exception of Virchow, were almost comparable in strains isolated from human and non-human sources over the period studied. The most striking result concerning single resistance was the spectacular increase of the resistance frequency to nalidixic acid for the strains belonging to serotypes Hadar and Virchow, especially in the poultry food sector (14 % in 1993 vs. 72 % in 2000 for Salmonella Virchow, 4 % in 1993 vs. 70% in 2000 for Salmonella Hadar) and also in human isolates (24 % in 1997 vs. 48 % in 2000 for S. Virchow, 31 % in 1997 vs. 78 % in 2000 for S. Hadar). In addition to the classical resistance to ampicillin, streptomycin, sulphonamide, chloramphenicol and tetracycline (ASSuCT resistance type), which stabilized between 1997 and 2000, the emergence of a new resistance type was observed.