Prevalence and antimicrobial resistance of Salmonella serotypes isolated from poultry in Spain: comparison between 1993 and 2006

Abstract

A total of 226 chicken samples (carcasses, legs, wings, necks and breasts) were obtained (73 in 1993 and 153 in 2006) from 10 retail outlets in North-Western Spain and screened for the presence of Salmonella. Isolates were subjected to serotyping, phage typing (Salmonella Enteritidis and Salmonella Typhimurium) and antimicrobial susceptibility testing (15 antimicrobials; disk diffusion method). Salmonella was detected in 40 (55%) samples in 1993 and 19 (12.4%) in 2006 (P<0.001). The serotypes (S. Enteritidis, Salmonella Poona, Salmonella Infantis, Salmonella Newport and S. Typhimurium) and phage types (1, 4, 14b and 35 in the case of S. Enteritidis and 193 for S. Typhimurium) detected are among the main types responsible for human salmonellosis in Spain. All strains were multi-resistant (resistant to 3-13 antimicrobials). The average number of resistances per strain increased (P<0.05) from 3.98 in 1993 to 5.00 in 2006. An increase in the incidence of resistance was observed between 1993 and 2006 for cephalothin (P<0.01), enrofloxacin (P<0.001) and tetracycline (P<0.01). The decreases in the prevalence of Salmonella between 1993 and 2006 suggest that the mandatory measures introduced over the last decade in the European Union to reduce the incidence of Salmonella in poultry have apparently been successful. However, the increase in antibiotic resistance rates is of concern and constitutes a threat to public health. Because the data in this study demonstrated that chicken in North-Western Spain is a potential source of antibiotic-resistant Salmonella strains, the need of consumer education on good sanitary practices is highlighted.