In order to see whether the susceptibility of Danish Listeria monocytogenes strains has changed over the years we examined a collection of human isolates from the period 1958-2001. We, furthermore, wanted to compare L. monocytogenes susceptibility testing using a disc diffusion assay with MIC measurements performed by the E-test. 106 strains isolated predominantly from blood cultures and cerebrospinal fluids were examined together with three reference strains. Susceptibility to the following antibiotics was tested by the E-test and by Oxoid discs using Iso-sensitest agar: penicillin G, ampicillin, meropenem, gentamicin, sulphamethoxazole, trimethoprim, ciprofloxacin, erythromycin, vancomycin, linezolid, chloramphenicol and tetracycline. The strains were in the main sensitive to all antibiotics examined using both methods, except for ciprofloxacin, where the strains were intermediate sensitive. However, for penicillin, ampicillin and sulphamethoxazole, while the disc diffusion assay found the strains to be sensitive, MIC measurements generally placed the strains one dilution above the breakpoint for sensitivity in the intermediate sensitive group. Based on the MIC measurements, the antibiotic susceptibility of L. monocytogenes has not changed in Denmark from 1958 to 2001, and the multiresistant strains found in human infections elsewhere have not been found in Denmark.
Antimicrobial treatment of acute infection caused by verocytotoxin toxin-producing Escherichia coli (VTEC) is controversial due to risk of inducing haemolytic uraemic syndrome. We review the treatment of 9 persons who experienced serious social problems due to prolonged, asymptomatic carriage of non-O157 VTEC. Eradication of VTEC was successful and without complications.
Infectious gastroenteritis is one of the most common diseases in young children. To clarify the infectious etiology of diarrhea in Danish children less than 5 years of age, we conducted a 2-year prospective case-control study. Stools from 424 children with diarrhea and 870 asymptomatic age-matched controls were examined, and their parents were interviewed concerning symptoms. Rotavirus, adenovirus, and astrovirus were detected by enzyme-linked immunosorbent assay, and norovirus and sapovirus were detected by PCR. Salmonella, thermotolerant Campylobacter, Yersinia, Shigella, and Vibrio spp. were detected by standard methods. Shiga toxin-producing (STEC), attaching-and-effacing (A/EEC), enteropathogenic (EPEC), enterotoxigenic, enteroinvasive, and enteroaggregative Escherichia coli were detected by using colony hybridization with virulence gene probes and serotyping. Parasites were detected by microscopy. Overall, a potential pathogen was found in 54% of cases. More cases than controls were infected with rotavirus, Salmonella, norovirus, adenovirus, Campylobacter, sapovirus, STEC, classical EPEC, Yersinia, and Cryptosporidium strains, whereas A/EEC, although common, was not associated with illness. The single most important cause of diarrhea was rotavirus, which points toward the need for a childhood vaccine for this pathogen, but norovirus, adenovirus, and sapovirus were also major etiologies. Salmonella sp. was the most common bacterial pathogen, followed by Campylobacter, STEC, Yersinia, and classical EPEC strains. A/EEC not belonging to the classical EPEC serotypes was not associated with diarrhea, underscoring the importance of serotyping for the definition of EPEC.
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.
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We report the findings of a case-control study of risk factors for sporadic cases of human campylobacteriosis in Denmark. In 3 different analytical models, the main domestic risk factor identified was eating fresh, unfrozen chicken. Specifically, 28 of 74 domestically acquired case-patients were exposed to fresh chicken compared with 21 of 114 controls (multivariate matched odds ratio 5.8; 95% confidence interval 2.1-15.9). In contrast, a risk from eating other poultry, including previously frozen chicken, was only indicated from borderline significant 2-factor interactions. The marked increase in consumption of fresh, unfrozen poultry in Denmark during the 1990s likely contributed substantially to the increasing incidence of human campylobacteriosis in this period.
To examine the general frequency of household outbreaks, the authors performed a retrospective search among cases of the five most frequent gastrointestinal bacterial pathogens in Denmark, a country of 5.3 million inhabitants. This was done for 57,667 cases registered from 1991 to 2001 by finding all cases that shared addresses and became infected within 3 weeks of one another. The percentage of cases that were part of household outbreaks was found to be 3.2% for Campylobacter, 13.3% for Salmonella serotype Enteritidis, 5.6% for Salmonella serotype Typhimurium, 2.0% for Yersinia enterocolitica, and 10.4% for Shigella sonnei. The vast majority of the outbreaks had not previously been registered. The wide variation in the ability to cause household outbreaks among the different types of bacteria reflects differences in their epidemiology and most likely also mirrors their overall outbreak potential. Differences in the time occurring between infections of household members may also indicate differences in the importance of person-to-person transmission for the different types of bacteria. The fact that household outbreaks occur with a relatively high frequency may be utilized in future analyses of sources of infection, in particular of Campylobacter, for which more household outbreaks than expected were identified.
Until recently, Salmonella enterica serotype Enteritidis has remained sensitive to most antibiotics. However, national surveillance data from Denmark show that quinolone resistance in S. Enteritidis has increased from 0.8% in 1995 to 8.5% in 2000. These data support concerns that the current use of quinolone in food animals leads to increasing resistance in S. Enteritidis and that action should be taken to limit such use.
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BACKGROUND: Risk factors for childhood diarrhea in industrialized countries are not well characterized, although diarrhea remains an important cause of morbidity. METHODS: We conducted a case-control study of 422 cases and 866 controls over 22 months in Denmark. We selected cases among children under 5 years of age with diarrhea. Age-matched healthy controls were selected from the background population using a population register. Parents were interviewed about possible exposures and underlying conditions. In addition, stool samples from both cases and controls were analyzed for viruses, parasites, and bacteria. We analyzed risk factors for diarrhea in general and for diarrhea of a viral, bacterial, or "unknown" etiology using logistic regression. RESULTS: The following factors were independently associated with an increased risk of diarrhea: recent foreign travel, contact with symptomatic persons (particularly in daycare centers), hospitalization, contact with a dog with diarrhea, private daycare, consumption of products containing formula milk, unemployment and low educational status of parents, and prior diagnosis of several types of atopic diseases. In a pathogenic-specific analysis of diarrhea of bacterial (73 patients), viral (88), or "unknown" (222) etiology, the major risk factor for viral diarrhea was contact with symptomatic persons. For bacterial diarrhea, foreign travel and socioeconomic factors were the main risk factors. CONCLUSIONS: Viral diarrhea appears to be transmitted predominantly from person to person, whereas bacterial diarrhea appears to be primarily foodborne. A substantial portion of the diarrheal episodes may be of noninfectious etiology. Limiting child-to-child transmission of disease in daycare centers may substantially reduce the disease burden.