Introduction: The use of antimicrobials in food production has been associated with drug-resistance in foodborne pathogens such as Salmonella and Campylobacter. However, little is known about the health impact of antimicrobial drug-resistance in these pathogens. In a matched cohort study, we determined the mortality associated with drug-resistance in Salmonella Typhimurium.
Material and methods: Data from the Danish Surveillance Registry for Enteric Pathogens were linked with the Civil Registration System and the Danish National Patient Registry. By survival analysis, the two-year mortality among patients was compared with a matched sample of the general Danish population adjusted for differences in comorbidity.
Results: Among 2047 cases of S. Typhimurium, 59 deaths were identified. Patients with pan-susceptible strains of S. Typhimurium were 2.3 times (95 per cent confidence interval [CI] 1.5-3.5) more likely to die in the two-year follow-up period after infection than persons in the general Danish population. Patients infected with strains resistant to ampicillin, chloramphenicol, streptomycin, sulfonamide, and tetracycline were 4.8 times (95 per cent CI 2.2-10.5) more likely to die, whereas quinolone-resistance was associated with a 10.3 times (95 percent CI 2.8-37.8) higher mortality than the general population.
Discussion: Overall, infections with S. Typhimurium were associated with excess mortality. Patients infected with multi-drug resistant strains had a tendency towards higher mortality than patients infected with non-multiresistant strains. Particular risk was associated with quinolone-resistance in foodborne S. Typhimurium, and the excess mortality among patients infected with multi-drug resistant S. Typhimurium could be attributed to additional quinolone resistance in many of the multi-drug resistant isolates.