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Non-typhoidal Salmonella (NTS) and Campylobacter are common causes of diarrhoea in human immunodeficiency virus (HIV)-positive patients. To investigate if incidence has changed since the introduction of highly active antiretroviral therapy (HAART), we combined data from The Danish Surveillance Registry for Enteric Pathogens and The Danish National Hospital Registry. We found that the incidences of NTS- and Campylobacter-related illness among HIV-positive patients in Denmark have declined since the introduction of HAART, although the incidences remained higher compared to the background population. Moreover our study suggests that there is an increased incidence of Campylobacter-related illness among homosexual men in the HIV-positive population.

Objectives: The use of antimicrobial drugs for food animals selects for resistant non-typhoid Salmonella strains, but human consumption of antimicrobial drugs may also increase the risk of subsequent infection. The aim of this study was to determine the risk of salmonellosis attributable to human consumption of antimicrobial drugs in a case-control study of 22 602 laboratory-confirmed Salmonella infections, diagnosed in Denmark between 1997 and 2005., Methods: A population registry-based case-control study, using several Danish databases: the National Prescription Database; the National Registry for Enteric Pathogens; the Civil Registry System; and the Integrated Database on Labour Market Research., Results: Exposure to trimethoprim, sulphonamides, broad-spectrum penicillins, tetracyclines and fluoroquinolones, during the year prior to diagnosis, was associated with an increased risk of non-typhoid Salmonella infection. Overall, the highest risk was associated with the prior use of fluoroquinolones. This risk increased as the time window of exposure approached the infection date. Previous use of fluoroquinolones was associated with an odds ratio (OR) of 4.55 [95% confidence interval (CI): 3.78-5.47] for Salmonella serotypes other than Salmonella Typhimurium or Salmonella Enteritidis, an OR of 2.21 (95% CI: 1.70-2.86) for Salmonella Typhimurium and an OR of 2.07 (95% CI: 1.76-2.42) for Salmonella Enteritidis. In particular for fluoroquinolones, there was an interaction between the pathogen resistance pattern and a history of antibiotic drug use., Conclusions: The increasing use of antibiotics, particularly fluoroquinolones, is likely to result in increased incidence of foodborne infections with drug-resistant Salmonella.

Background: Salmonella enterica subsp. enterica is one of the leading food-borne pathogens in the USA and European countries. Outcome of human Salmonella serotype Typhimurium infections ranges from mild self-limiting diarrhoea to severe diarrhoea that requires hospitalization. Increased knowledge of the mechanisms that are responsible for causing infection and especially the severity of infection is of high interest., Results: Strains were selected from patients with mild infections (n = 9) and patients with severe infections (n = 9) and clinical data allowed us to correct for known underlying diseases. Additionally, outbreak isolates (n = 3) were selected. Strains were analyzed on a DNA-DNA microarray for presence or absence of 281 genes covering marker groups of genes related to pathogenicity, phages, antimicrobial resistance, fimbriae, mobility, serotype and metabolism. Strains showed highly similar profiles when comparing virulence associated genes, but differences between strains were detected in the prophage marker group. The Salmonella virulence plasmid was present in 72% of the strains, but presence or absence of the virulence plasmid did not correspond to disease symptoms. A dendrogram clustered strains into four groups. Clustering confirmed DT104 as being a clonal phagetype. Clustering of the remaining strains was mainly correlated to presence or absence of the virulence plasmid and mobile elements such as transposons. Each of the four clusters in the tree represented an almost equal amount of strains causing severe or mild symptoms of infection., Conclusions: We investigated clinical significance of known virulence factors of Salmonella serotype Typhimurium strains causing different disease symptoms, and conclude that the few detected differences in Salmonella serotype Typhimurium do not affect outcome of human disease.

The incidence of multidrug-resistant (MDR) Salmonella Typhimurium infections in humans, and in particular MDR definitive phage type 104 (DT104), has increased substantially in many countries in the last 2 decades, often associated with increased illness. To examine the magnitude of this problem, a survey was conducted among countries with available antimicrobial resistance or phage typing surveillance data. A total of 29, primarily industrialized, countries participated in the survey, which covered the years 1992-2001. Overall, the incidence of MDR S. Typhimurium and DT104 increased continuously during this period, although the problem affected primarily Europe and North America. The increase appeared to have peaked in the United Kingdom but not in other countries. Also, the incidence of quinolone-resistant S. Typhimurium was increasing. This survey implies that MDR S. Typhimurium constitutes an increasing public health problem in large parts of the world and emphasizes the importance of surveillance and control programs.

In a registry-based cohort study, we determined the risk of invasive illness or death associated with infection with quinolone-resistant Salmonella serotype Typhimurium. We linked data from the Danish surveillance registry of enteric pathogens with data from the Danish civil registration system and 2 national health registries. Of 1323 patients infected with Salmonella Typhimurium, 46 (3.5%) were hospitalized due an invasive illness within 90 days of infection, and 16 (1.2%) died within 90 days of infection. After adjustment for age, sex, and comorbidity, infection with quinolone-resistant Salmonella Typhimurium was associated with a 3.15-fold (95% confidence interval, 1.39-7.10-fold) higher risk of invasive illness or death within 90 days of infection, compared with that observed for infection with pansusceptible strains.

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.

In a matched cohort study, we determined the death rates associated with drug resistance in Salmonella Typhimurium. We linked data from the Danish Surveillance Registry for Enteric Pathogens with the Civil Registration System and the Danish National Discharge Registry. By survival analysis, the 2-year death rates were compared with a matched sample of the general Danish population, after the data were adjusted for differences in comorbidity. In 2,047 patients with S. Typhimurium, 59 deaths were identified. Patients with pansusceptible strains of S. Typhimurium were 2.3 times more likely to die 2 years 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% CI 2.2 to 10.2) more likely to die, whereas quinolone resistance was associated with a mortality rate 10.3 times higher than the general population.