[Excess mortality associated with antibiotic resistant Salmonella typhimurium]

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.

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.

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.

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.