Jørgen Fr Lassen

Outbreak of haemolytic uraemic syndrome in Norway caused by stx2-positive Escherichia coli O103:H25 traced to cured mutton sausages.

BackgroundOn 20–21 February 2006, six cases of diarrhoea-associated haemolytic uraemic syndrome (HUS) were reported by paediatricians to the Norwegian Institute of Public Health. We initiated an investigation to identify the etiologic agent and determine the source of the outbreak in order to implement control measures.MethodsA case was defined as a child with diarrhoea-associated HUS or any person with an infection with the outbreak strain of E. coli O103 (defined by the multi-locus variable number tandem repeats analysis (MLVA) profile) both with illness onset after January 1st 2006 in Norway. After initial hypotheses-generating interviews, we performed a case-control study with the first fifteen cases and three controls for each case matched by age, sex and municipality. Suspected food items were sampled, and any E. coli O103 strains were typed by MLVA.ResultsBetween 20 February and 6 April 2006, 17 cases were identified, of which 10 children developed HUS, including one fatal case. After pilot interviews, a matched case-control study was performed indicating an association between a traditional cured sausage (odds ratio 19.4 (95% CI: 2.4–156)) and STEC infection. E. coli O103:H25 identical to the outbreak strain defined by MLVA profile was found in the product and traced back to contaminated mutton.ConclusionWe report an outbreak caused by a rare STEC variant (O103:H25, stx2-positive). More than half of the diagnosed patients developed HUS, indicating that the causative organism is particularly virulent. Small ruminants continue to be important reservoirs for human-pathogen STEC. Improved slaughtering hygiene and good manufacturing practices for cured sausage products are needed to minimise the possibility of STEC surviving through the entire sausage production process.

Sources of sporadic Yersinia enterocolitica infections in Norway: a prospective case-control study.

Yersinia enterocolitica is a recognized cause of gastroenteritis in northern Europe. During October 1988-January 1990, a prospective case-control study was performed to address risk factors associated with sporadic Y. enterocolitica infections in southeastern Norway. Sixty-seven case-patients (mean age 23.4 years, range 8 months-88 years) and 132 age-, sex- and geographically-matched controls were enrolled in the study. Multivariate analysis of the data showed that persons with Y. enterocolitica infection reported having eaten significantly more pork items (3.79 v. 2.30 meals, P = 0.02) and sausage (2.84 v. 2.20 meals, P = 0.03) in the 2 weeks before illness onset than their matched controls; only one patient had eaten raw pork. Patients were also more likely than controls to report a preference for eating meat prepared raw or rare (47 v. 27%, P = 0.01), and to report drinking untreated water (39 v. 25%, P = 0.01) in the 2 weeks before illness onset. Each of these factors was independently associated with disease, suggesting a link between yersiniosis and consumption of undercooked pork and sausage products and untreated water. Efforts should be directed towards developing techniques to reduce Y. enterocolitica contamination of pork and educating consumers about (1) proper handling and preparation of pork items and (2) the hazards of drinking untreated water.

Outbreak of Salmonella Thompson Infections Linked to Imported Rucola Lettuce

On November 15, 2004, a cluster of three cases of Salmonella Thompson infection was registered by the Norwegian reference laboratory. In the following days further cases occurred, prompting a case-control study among the first 13 cases and 26 matched controls. By December 31, 21 cases had been reported, with the first onset on October 24. Consumption of rucola lettuce (Eruca sativa, also known as rocket salad or arugula) (OR 8,8 [1,2-infinity]) and mixed salad (OR 5,0 [1,0-infinity]) was associated with illness. On November 26, Swedish authorities notified the finding of Salmonella Thompson in rucola lettuce through the EU Rapid Alert System for Food and Feed. Later, several countries reported finding this and other Salmonella serovars and Campylobacter in rucola produced in Italy. In response to our alert through the international Enter-net surveillance network, Sweden and England also reported an increase of cases. Salmonella Thompson isolates from products and patients from several countries showed high similarity by pulsed-field gel electrophoresis, but some isolates showed significant differences. We think that the outbreak in Norway reflected a larger international outbreak caused by rucola imported from one Italian producer. Findings of other pathogens indicate a massive contamination, possibly caused by irrigation with nonpotable water. Rapid international information exchange is invaluable when investigating outbreaks caused by internationally marketed products.

Lack of agreement between biochemical and genetic identification of Aeromonas spp

Biochemical and genetic identification by RFLP (restriction fragment length polymorphism) of the PCR‐amplified 16S r‐RNA sequence were compared for a selection of 171 clinical and environmental isolates of Aeromonas spp. The investigation revealed large differences between the two methods. The species phenotypic identification scheme and the genetic technique applied to the environmental strains gave divergent results for 96% of the strains tested. There was 46% discrepancy between the two methods for the clinical isolates. The distribution of species differed between clinical and environmental isolates. A. hydrophila, A. caviae, A. jandaei and A. veronii dominated the clinical material (81% of isolates by RFLP), whilst only 21% of the environmental isolates belonged to those four species. From the environmental group A. salmonicida, A. bestiarum, A. sobria, A. media, and A. encheleia contributed 72% of the strains tested. The poor parity between the biochemical and the genetic identification of the environmental isolates, and to a lesser extent for the clinical isolates, underlines the fact that our current biochemical methods cannot adequately differentiate Aeromonas spp. This work also shows that the biochemical schemes derived from clinical isolates are incomplete for the identification of environmental strains.

Chromosomal Integration of the Extended-Spectrum β-Lactamase Gene blaCTX-M-15 in Salmonella enterica Serotype Concord Isolates from Internationally Adopted Children

ABSTRACT We report the emergence of Salmonella enterica isolates of serotype Concord (and its monophasic variant 6,7:l,v:-) producing the extended-spectrum β-lactamases (ESBLs) SHV-12 and CTX-M-15 in France and Norway between 2001 and 2006 (43 in France and 26 in Norway). The majority of these isolates were from adopted children from Ethiopia, most of whom were healthy carriers. Several symptomatic secondary cases were found in the adoptive families and health care facilities in France. Serotype Concord isolates collected before 2003 produced SHV-12 encoded on a 340-kb conjugative plasmid of replicon IncI1. Isolates collected after 2003 produced CTX-M-15. We detected two conjugative plasmids carrying blaCTX-M-15. One plasmid, approximately 300 kb in size, was positive for the IncHI2 replicon and the plasmid-mediated quinolone resistance gene qnrA1. The other plasmid, from one of the earliest CTX-M-15-producing isolates collected, was a fusion plasmid with IncY and IncA/C2 replicons and was 200 kb in size. However, we showed, using Southern hybridization of I-CeuI-digested chromosomal DNA and S1 nuclease analysis of plasmid DNA, that most isolates had a blaCTX-M-15 gene located on chromosomal DNA. Analysis of the flanking regions of the chromosomally located blaCTX-M-15 gene by cloning revealed an ISEcp1 truncated by an intact IS26 upstream from the blaCTX-M-15 gene and a truncated orf477 gene downstream from blaCTX-M-15. We found regions beyond the IS26 and the orf477 genes that were derived from IncA/C2 plasmids, suggesting the chromosomal integration of part of the blaCTX-M-15-carrying IncY and IncA/C2 fusion plasmid from early CTX-M-15-producing isolates.

Genetic variability among isolates of Listeria monocytogenes from food products, clinical samples and processing environments, estimated by RAPD typing

RAPD analysis with four primers was used to examine the genetic relationship among 432 strains of Listeria monocytogenes isolated from clinical and veterinarian cases of listeriosis, dairy, vegetable, meat- and fish-based food items, environmental samples and samples collected from one transport terminal, one poultry-processing company and four Atlantic salmon-processing plants. The purpose of the study was to determine whether clinical isolates belonged to a specific genetic group, whether links could be made between food groups and clinical cases and whether specific genetic groups were associated with specific food products or processing units. There was great genetic variability among the isolates, which produced a total of 141 RAPD composites based on the RAPD analysis with four primers. The RAPD composites divided in two major clusters and clinical isolates were evenly distributed in both of them. None of the isolates from food products had the same RAPD composite as isolates from human patients, thus, no particular food commodity could be linked to clinical cases. Each food-processing environment was contaminated with more than one RAPD composite and the genetic variability found within each company was, in most cases, of approximately the same magnitude as the variability found when considering all the samples. In each plant, one or a few types persisted over time, indicating the presence of an established in-house flora. Our results indicate that most of the analysed cases of listeriosis were sporadic and, further, that these cases cannot be traced to a few specific food sources. We also found that no particular RAPD composite was better suited for survival in specific food types or food-processing environments, indicating that although differences may be found in virulence properties of individual strains, all L. monocytogenes must be treated as potentially harmful.

Clinical Features of Sporadic Campylobacter Infections in Norway

To assess risk factors and clinical impact of campylobacteriosis in Norway, a case-control study of sporadic cases of infection with thermotolerant Campylobacter spp. was conducted. This report describes: (1) the frequency and duration of signs and symptoms, antimicrobial treatment, hospitalization, and faecal carriage among the study patients; (2) diarrhoeal illness and campylobacter carriage among their household members; and (3) antimicrobial susceptibility pattern among bacterial isolates. A total of 135 patients with bacteriologically confirmed campylobacter infection were enrolled in the study. Of these, 58 (43%) were domestically acquired while 77 (57%) were acquired abroad. If the study enrollees are representative of the cases reported to the national surveillance system, the reported infections led to an estimated annual average of at least 8590 days of illness, 78 admissions to hospital, 329 days of hospital stay, 2236 days lost at work or at school, 1000 physician consultations, and 96 antimicrobial prescriptions among the 4.2 million Norwegians. Convalescent carriage of campylobacter was detected in 16% of the patients who submitted follow-up stool specimens; the organism was carried for a mean of 37.6 days (median 31, range 15-69) after the onset of illness. Antimicrobial treatment appeared to have reduced the likelihood of carriage once symptoms had resolved. Diarrhoeal illness was more commonly reported in members of case households than control households (OR = 5.44, p < 0.0001). Cases were more likely than controls to report antecedent recurrent diarrhoea (OR = 6.00, p = 0.034). Two cases of neonatal infection, probably acquired from the mother at the time of delivery, were detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Salmonella infections in Norway : descriptive epidemiology and a case-control study

The epidemiological progression of human salmonellosis in Norway is parallel to trends noted elsewhere in Europe. During the past two decades, the number of reported cases has increased steadily, with a special sharp rise in the early 1980s due to the emergence of Salmonella enteritidis, followed by a levelling off in recent years. However, in contrast to the situation in most other European countries, about 90% of the cases from whom a travel history is available, have acquired their infection abroad. The incidence of indigenous salmonella infections as well as the prevalence of the microorganism in the domestic food chain, are both comparatively low. In 1993-4, a national case-control study of sporadic indigenous salmonella infections was conducted to identify preventable risk factors and guide preventive efforts. Ninety-four case patients and 226 matched population controls were enrolled. The study failed to demonstrate any statistically significant association between salmonellosis and consumption of domestically produced red meat, poultry or eggs. The only factor which remained independently associated with an increased risk in conditional logistic regression analysis, was consumption of poultry purchased abroad during holiday visits to neighbouring countries. A separate analysis of Salmonella typhimurium infections incriminated food from catering establishments and foreign travel among household members, in addition to imported poultry.

Antimicrobial resistance in Campylobacter jejuni from humans and broilers in Norway

In this study comprising isolates from 2001 to 2003, resistance was considerably more widespread among Campylobacter jejuni from humans infected abroad than infected within Norway. The discrepancy was particularly notable for fluoroquinolone resistance (67.4% vs. 6.5%). This is probably a reflection of a low resistance prevalence in Norwegian broiler isolates (1.2% fluoroquinolone resistant).

Outbreak of Salmonella Livingstone infection in Norway and Sweden due to contaminated processed fish products.

In Europe, the number of reported sporadic human cases of Salmonella Livingstone infection is low, and outbreaks are rare. We report the largest S. Livingstone outbreak described in the literature having an identified source of infection. In February 2001, an increased incidence of infection caused by S. Livingstone was observed in Norway and Sweden. By July 2001, 44 cases were notified in Norway and 16 in Sweden. The median age was 63 years, and 40 were women. There were three deaths, and 22 patients were hospitalized. Based on standardized questionnaires and retrospective studies of S. Livingstone strains in Norway and Sweden, food items with egg powder were suspected, and S. Livingstone was subsequently recovered from a processed fish product at the retail level. Analysis by pulsed-field gel electrophoresis documented that isolates from the fish product belonged to the same clone as the outbreak strain.