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

(Accepted 13 May 2005, first published online 29 July 2005)SUMMARYA total of 1873 strains from human origin and 4283 strains from non-human origin of Salmonellaenterica serotypes Typhimurium, Enteritidis, Heidelberg, Hadar and Virchow, collected overthree years 1993, 1997 and 2000, were examined in order to determine the rate of antimicrobialresistance to 12 antimicrobial drugs. The objective of the study was to describe and to comparethe evolution of the main resistance types in human and non-human isolates, focusing on thepoultry sector. The evolution and the rates of antimicrobial resistances for the five serotypes, withthe 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 wasthe spectacular increase of the resistance frequency to nalidixic acid for the strains belonging toserotypes Hadar and Virchow, especially in the poultry food sector (14% in 1993 vs. 72% in 2000for Salmonella Virchow, 4% in 1993 vs. 70% in 2000 for Salmonella Hadar) and also in humanisolates (24% in 1997 vs. 48% in 2000 for S. Virchow, 31% in 1997 vs. 78% in 2000 forS. Hadar). In addition to the classical resistance to ampicillin, streptomycin, sulphonamide,chloramphenicol and tetracycline (ASSuCT resistance type), which stabilized between 1997 and2000, the emergence of a new resistance type was observed.INTRODUCTIONSalmonellosis is the most frequent foodborne diseasereported in France, often transmitted by foods ofanimal origin, especially raw eggs, egg products orpoultry meats, causing more than 300 outbreaks peryear [1]. To address this public health problem,national surveillance networks to monitor Salmon-ellae of both human and non-human origins wereset up. These networks are used to reveal trends inthe evolution of different serotypes, monitor theirantimicrobial susceptibility, detect outbreaks, andcontribute to their investigation. Antimicrobial re-sistance monitoring has become more important sincethe appearance and dissemination of multidrug-resistant Salmonella Typhimurium phage typeDT104, conferring resistance to ampicillin, strepto-mycin, sulphonamide, chloramphenicol and tetra-cycline(resistance-typeASSuCT).Thegenesencodingfor these resistances are clustered on the chromo-somal genomic island SGI1 and can be transferred