The attribution of human infections with antimicrobial resistant Salmonella bacteria in Denmark to sources of animal origin.

Based on the Danish Salmonella surveillance in 2000-2001, we developed a mathematical model for quantifying the contribution of each major animal-food sources to human salmonellosis caused by antimicrobial resistant bacteria. Domestic food products accounted for 53.1% of all cases, mainly caused by table eggs (37.6%). A large proportion (19%) of cases were travel related, while 18% could not be associated with any source. Imported food products accounted for 9.5% of all cases; the most important source being imported chicken. Multidrug and quinolone resistance was rarely found in cases acquired from Danish food, but was common in cases related to imported products (49.7% and 35.6% of attributable cases) and travelling (26.5% and 38.3% of attributable cases). For most serovars, the quinolone-resistant isolates were found to be associated with relatively more human infections than that of resistant isolates, which in turn was higher than that of susceptible isolates. This may be due to quinolone-resistant isolates having a higher ability to survive food processing and/or cause disease. This study showed domestic food to be the most important source of Salmonella infections in Denmark, but infections with multidrug- and quinolone-resistant isolates were more commonly caused by imported food products and travelling, emphasizing the need for a global perspective on food safety and antimicrobial usage.