Eva Nielsen - Academia.edu (original) (raw)

Papers by Eva Nielsen

Epidemiology and Infection, Mar 5, 2007

Clinical Infectious Diseases, Apr 15, 2009

Veterinary Microbiology, Aug 1, 2006

The occurrence and species distribution of thermophilic Campylobacter was investigated in organic... more The occurrence and species distribution of thermophilic Campylobacter was investigated in organic outdoor pigs. An increased exposure of outdoor pigs to C. jejuni from the environment may cause a shift from a normal dominance of C. coli to more C. jejuni, which may imply a concern of reduced food safety. Bacteriological methods for determination of Campylobacter excretion level were combined with colony-blot hybridization and real-time PCR for specific detection of C. jejuni in pigs. Campylobacter was isolated from pigs (n = 47), paddock environment (n = 126) and wildlife (n = 44), identified to species by real-time PCR and sub-typed by serotyping (Penner) and pulse-field gel electrophorsis (PFGE) genotyping. All pigs excreted Campylobacter (10 3-10 7 CFU g À1 faeces) from the age of 8-13-weeks old. C. jejuni was found in 29% of pigs in three consecutive trials and always in minority to C. coli (0.3-46%). C. jejuni and C. coli were isolated from 10% and 29% of the environmental samples, respectively, while crow-birds and rats harboured C. jejuni. Individual pigs hosted several strains (up to nine serotypes). The paddock environment was contaminated with C. coli serotypes similar to pig isolates, while most of the C. jejuni serotypes differed. C. jejuni isolates of different origin comprised few similar serotypes, just one identical genotype was common between pigs, environment and birds. In conclusion, the occurrence of C. jejuni varied considerably between the three groups of outdoor pigs. Furthermore, transfer of C. jejuni to the outdoor pigs from the nearby environment was not predominant according to the subtype dissimilarities of the obtained isolates.

Emerging Infectious Diseases, Mar 1, 2020

C ampylobacter jejuni is the most frequent cause of bacterial gastroenteritis in industrialized c... more C ampylobacter jejuni is the most frequent cause of bacterial gastroenteritis in industrialized countries worldwide (1,2), including in Denmark, where ≈4,000 Campylobacter infections are reported annually (3). Despite the high notification rates, Campylobacter infections are believed to be highly underdiagnosed (4,5). Denmark's national surveillance system for Campylobacter is based on observation of the number of notified human cases (3); a substantial number of Campylobacter outbreaks may be overlooked because of a lack of routine microbiological typing of isolates. This hypothesis is supported by evidence from a recent study, in which whole-genome sequencing (WGS)-based typing of selected clinical Campylobacter isolates from patients in Denmark identified numerous small outbreak-like clusters (6). This finding suggests that more outbreaks occur in Denmark than the few typically large outbreaks associated with a single event that are detected by the current surveillance system (7-10). To achieve a national surveillance system that will detect ongoing Campylobacter outbreaks in real time, highly discriminatory subtyping of isolates is needed. Thus, we more comprehensively evaluated the frequency of Campylobacter outbreaks among humans in Denmark by using WGS-based typing. To match the clinical isolates with their sources, we compared them with isolates from food and animals, covering the main putative sources of human Campylobacter infections (i.e., contact with or consumption of animals or animal products, primarily contaminated poultry meat). Although Campylobacter infections are primarily foodborne, a recent case-control study in Denmark found that contact with animals and the environment might account for a substantial proportion of domestic infections (11). Several other reported sources of infection include unpasteurized milk, drinking water, bathing water, vegetables, and fruits (1,12-14). WGS offers high-resolution discriminatory subtyping and has been successfully implemented for

Journal of Applied Microbiology, Feb 12, 2014

 Users may download and print one copy of any publication from the public portal for the purpose... more  Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Epidemiology and Infection, Oct 1, 2003

During the period January 1998-December 2001, all Danish broiler flocks were monitored bacteriolo... more During the period January 1998-December 2001, all Danish broiler flocks were monitored bacteriologically for thermophilic campylobacters and isolates were stored at x80 xC. Six neighbouring broiler farms in a small community were selected for detailed examination of all Campylobacter jejuni isolated (n=180) from these farms during 1998-2000 using Penner serotyping and pulsed-field gel electrophoresis (PFGE). The area and the farms were selected according to their prevalence of campylobacter so that both farms with low and high frequencies of campylobacter positive flocks were included in the study. The frequency of campylobacter positive flocks on the six farms ranged from 24. 5 to 72. 7%. One hundred and eighty of the isolates were C. jejuni (included in this study), 14 isolates were C. coli whereas 7 isolates belonged to other species but were not further identified. By serotyping of all C. jejuni 56 isolates (31. 5%) were assigned to the 4-complex, 32 isolates (18. 0%) to serotype 2, 12 isolates (6. 7 %) to serotype 11, and 11 isolates (6. 2%) were assigned to serotype 12. In three farms, 4-complex was the most prevalent serotype, in one farm it was the second most frequently isolated serotype, while serotypes 2 and 1,44, respectively, were the most frequently isolated from the two remaining farms. This serotype distribution differed from the overall country-wide distribution where serotypes 2 and 1,44 are the most prevalent. All serotype 4-complex isolates from the six selected farms were compared by PFGE to serotype 4-complex isolates from the rest of the country. The results showed that there was a high level of diversity among isolates from the whole country, whereas isolates from the six farms were very homogeneous and only displayed one or a few different PFGE patterns on each farm. It is suggested that certain campylobacter clones persist in a confined geographical area, probably at the farm, and that the broiler houses may be repeatedly infected with a few C. jejuni clones during succeeding broiler flocks. New clones may be introduced, however, the sources and vehicles are yet unknown.

Clinical Microbiology and Infection, Jul 1, 2016

Listeria monocytogenes may contaminate and persist in food production facilities and cause repeat... more Listeria monocytogenes may contaminate and persist in food production facilities and cause repeated, seemingly sporadic, illnesses over extended periods of time. We report on the investigation of two such concurrent outbreaks. We compared patient isolates and available isolates from foods and food production facilities by use of whole-genome sequencing and subsequent multilocus sequence type and single nucleotide polymorphism analysis. Outbreak cases shared outbreak strains, defined as Listeria monocytogenes isolates belonging to the same sequence type with fewer than five single nucleotide polymorphism differences. We performed routine food consumption interviews of L. monocytogenes patients and compared outbreak cases with sporadic cases. Two outbreaks were defined, each consisting of ten outbreak cases in the period 2013e15. Seven outbreak cases and a fetus in gestational week 38 died. Listeria monocytogenes isolates from cold smoked or gravad fish products or their two respective production environments were repeatedly found to belong to the outbreak strains. Outbreak cases more often than sporadic cases stated that they consumed the relevant fish products, odds ratio 10.7. Routine collection and typing of food isolates was key to solving the outbreaks. Furthermore, these outbreaks illustrate the value of whole-genome sequencing for outbreak definition and investigation. Wholegenome sequencing combined with epidemiological investigations provided the discriminatory power to recognize low-intensity, extended time-period outbreaks and link them to food products from two different contaminated production facilities with sufficient strength for food authorities to intervene on. Cold smoked and gravad fish constitute risk products and may be responsible for more listeriosis cases than previously recognized.

Weekly releases (1997–2007), Jun 14, 2007

Eurosurveillance

Background Since 2008, Danish national surveillance of Clostridioides difficile has focused on bi... more Background Since 2008, Danish national surveillance of Clostridioides difficile has focused on binary toxin-positive strains in order to monitor epidemic types such as PCR ribotype (RT) 027 and 078. Additional surveillance is needed to provide a more unbiased representation of all strains from the clinical reservoir. Aim Setting up a new sentinel surveillance scheme for an improved understanding of type distribution relative to time, geography and epidemiology, here presenting data from 2016 to 2019. Methods For 2─4 weeks in spring and autumn each year between 2016 and 2019, all 10 Danish Departments of Clinical Microbiology collected faecal samples containing toxigenic C. difficile. Isolates were typed at the national reference laboratory at Statens Serum Institut. The typing method in 2016–17 used tandem-repeat-sequence typing, while the typing method in 2018–19 was whole genome sequencing. Results During the study period, the sentinel surveillance scheme included ca 14–15% of all...

Eurosurveillance

An outbreak of Salmonella Typhimurium phage type U292 has been ongoing in Denmark since 1 April, ... more An outbreak of Salmonella Typhimurium phage type U292 has been ongoing in Denmark since 1 April, with 1,054 cases registered until 23 October 2008. Extensive investigations including hypothesis-generating interviews, matched case-control studies, cohort studies in embedded outbreaks, shopping list analyses, analyses of food samples from patient's homes, trace-back analyses and extensive microbiological analysis of products have not provided clear indications of a specific source of infection but the main hypothesis is that the vehicle of the outbreak are different pork products. In addition to the large U292 outbreak, at least four other S. Typhimurium outbreaks (caused by phage types U288, DT120, DT3 and DT135) have been investigated in Denmark in 2008.

Weekly releases (1997–2007), 2007

Eurosurveillance, 2006

In May/June 2005 an outbreak of diarrhoeal illness occurred among company employees in Copenhagen... more In May/June 2005 an outbreak of diarrhoeal illness occurred among company employees in Copenhagen. Cases were reported from seven of eight companies that received food from the same catering kitchen. Stool specimens from three patients from two companies were positive for Campylobacter jejuni. We performed a retrospective cohort study among employees exposed to canteen food in the three largest companies to identify the source of the outbreak and to prevent further spread. Using self-administered questionnaires we collected information on disease, days of canteen food eaten and food items consumed. The catering kitchen was inspected and food samples were taken. Questionnaires were returned by 295/348 (85%) employees. Of 247 employees who ate canteen food, 79 were cases, and the attack rate (AR) was 32%. Consuming canteen food on 25 May was associated with illness (AR 75/204, RR=3.2, 95%CI 1.3-8.2). Consumption of chicken salad on this day, but not other types of food, was associated...

Zoonoses and Public Health, 2017

SummaryCampylobacter is the most frequently occurring cause of bacterial gastroenteritis in Europ... more SummaryCampylobacter is the most frequently occurring cause of bacterial gastroenteritis in Europe. Unlike other zoonotic diseases, European‐wide incidences of Campylobacter infections have increased during the past decade, resulting in a significant disease burden. In Denmark, campylobacteriosis is notifiable by laboratory and a unique registration system of electronic transfer and storage of notified Campylobacter cases linked to the national person register of age, gender and geographical location allows collection of comprehensive case data. Using national surveillance data, we describe Campylobacter infections in Denmark from 2000 to 2015, focusing on age‐specific incidences, geography, seasonality and outbreaks. During the observed period, a total of 60,725 Campylobacter infections were registered with a mean annual incidence of 69.3 cases/100,000 population. From 2000 to 2014, the incidence of campylobacteriosis decreased by 20%, followed by an apparent increase of 20% from 2...

Eurosurveillance, 2013

Multiple-locus variable-number of tandem-repeats analysis (MLVA) has emerged as a valuable method... more Multiple-locus variable-number of tandem-repeats analysis (MLVA) has emerged as a valuable method for subtyping bacterial pathogens and has been adopted in many countries as a critical component of their laboratory-based surveillance. Lack of harmonisation and standardisation of the method, however, has made comparison of results generated in different laboratories difficult, if not impossible, and has therefore hampered its use in international surveillance. This paper proposes an international consensus on the development, validation, nomenclature and quality control for MLVA used for molecular surveillance and outbreak detection based on a review of the current state of knowledge.

Journal of Applied Microbiology, 2003

To study the prevalence of seven virulence and toxin genes, and cytolethal distending toxin (CDT)... more To study the prevalence of seven virulence and toxin genes, and cytolethal distending toxin (CDT) production of Campylobacter jejuni and C. coli isolates from Danish pigs and cattle. Methods and Results: The presence of the cadF, ceuE, virB11, flaA, cdtA, cdtB, cdtC and the cdt gene cluster among 40 C. jejuni and C. coli isolates was detected by polymerase chain reaction. The CDT production of the isolates was determined on Vero, colon 205 and chicken embryo cells. The cadF, flaA, ceuE and cdtB genes were detected from 100% of the isolates. The cdtA and cdtC genes were found in 95AE0 and 90AE0% of the isolates, respectively. The cdt gene cluster was detected in 82AE5% isolates. Only 7AE5% of the isolates were positive for virB11. Ninety-five per cent of the isolates produced CDT in Vero and colon 205 cell assays, and 90% of the isolates produced CDT in chicken embryo cell assays. Conclusions: High prevalence of the cadF, ceuE, flaA and cdtB genes was found. Data of the prevalence of cdt genes was consistent with the CDT titres produced by the isolates. Campylobacter coli from pigs produced high CDT titres. Significance and Impact of the Study: The high prevalence of seven virulence and toxin genes demonstrated that these putative pathogenic determinants are widespread among Campylobacter isolates from pigs and cattle. Campylobacter coli isolates from pigs produced much higher CDT titres compared with C. coli isolates from other sources suggesting that C. coli may be particularly adapted to or associated with this species.

Foodborne Pathogens and Disease, 2012

Shigella flexneri is one of the agents most frequently linked to diarrheal illness in developing ... more Shigella flexneri is one of the agents most frequently linked to diarrheal illness in developing countries and often causes outbreaks in settings with poor hygiene or sanitary conditions. Travel is one of the means by which S. flexneri can be imported into developed countries, where this pathogen is not commonly seen. A robust and discriminatory subtyping method is needed for the surveillance of S. flexneri locally and regionally, and to aid in the detection and investigation of outbreaks. The PulseNet International network utilizes standardized pulsedfield gel electrophoresis (PFGE) protocols to carry out laboratory-based surveillance of foodborne pathogens in combination with epidemiologic data. A multicenter validation was carried out in nine PulseNet laboratories located in North and South America, Europe, and Asia, and it demonstrated that a new protocol is highly robust and reproducible for subtyping of S. flexneri. This protocol, already approved for PulseNet laboratories, applies NotI and XbaI as primary and secondary restriction enzymes, respectively, under electrophoresis conditions of initial switch time of 5 s to final switch time of 35 s, at 6 volts/cm.

European Journal of Clinical Microbiology & Infectious Diseases, 2013

Clostridium difficile infection (CDI) is gradually being recognised as a cause of morbidity in th... more Clostridium difficile infection (CDI) is gradually being recognised as a cause of morbidity in the community. We investigated the incidence and clinical characteristics of CDI in a community setting and characterised the C. difficile strains by toxin gene profiling and polymerase chain reaction (PCR) ribotyping. Patients included in the study had attended general practice, primarily because of diarrhoea; CDI patients (259 patients; 121 <2 years of age) had positive cultures for toxigenic C. difficile and non-CDI patients (455 patients) were culture-negative. Outcome variables included the frequency and duration of diarrhoea, vomiting, stomach ache, fever >38 °C, weight loss and sick leave. Data were analysed by logistic regression. CDI patients <2 and ≥2 years of age with C. difficile as the only enteropathogen in the faecal sample reported slimy stools (65% vs. 62%), stomach ache (60% vs. 75%), weight loss (50% vs. 76%) and duration of diarrhoea >15 days (59% vs. 73%) as the predominant symptoms. CDI patients ≥2 years old reported duration of diarrhoea >15 days more often compared to non-CDI patients (73% vs. 27 %, p < 0.0001). The annual incidence of CDI was 518 and 23/100,000 for patients <2 and ≥2 years of age, respectively, and 46/100,000 in the subgroup of patients ≥60 years of age. CDI was characterised by stomach ache and persistent diarrhoea, often leading to weight loss. This emphasises the importance of diagnosing CDI not only in hospitalised patients, but also in individuals ≥2 years of age attending general practice because of gastrointestinal symptoms, especially in the elderly, where the incidence of CDI is high.

Epidemiology and Infection, Mar 5, 2007

Clinical Infectious Diseases, Apr 15, 2009

Veterinary Microbiology, Aug 1, 2006

The occurrence and species distribution of thermophilic Campylobacter was investigated in organic... more The occurrence and species distribution of thermophilic Campylobacter was investigated in organic outdoor pigs. An increased exposure of outdoor pigs to C. jejuni from the environment may cause a shift from a normal dominance of C. coli to more C. jejuni, which may imply a concern of reduced food safety. Bacteriological methods for determination of Campylobacter excretion level were combined with colony-blot hybridization and real-time PCR for specific detection of C. jejuni in pigs. Campylobacter was isolated from pigs (n = 47), paddock environment (n = 126) and wildlife (n = 44), identified to species by real-time PCR and sub-typed by serotyping (Penner) and pulse-field gel electrophorsis (PFGE) genotyping. All pigs excreted Campylobacter (10 3-10 7 CFU g À1 faeces) from the age of 8-13-weeks old. C. jejuni was found in 29% of pigs in three consecutive trials and always in minority to C. coli (0.3-46%). C. jejuni and C. coli were isolated from 10% and 29% of the environmental samples, respectively, while crow-birds and rats harboured C. jejuni. Individual pigs hosted several strains (up to nine serotypes). The paddock environment was contaminated with C. coli serotypes similar to pig isolates, while most of the C. jejuni serotypes differed. C. jejuni isolates of different origin comprised few similar serotypes, just one identical genotype was common between pigs, environment and birds. In conclusion, the occurrence of C. jejuni varied considerably between the three groups of outdoor pigs. Furthermore, transfer of C. jejuni to the outdoor pigs from the nearby environment was not predominant according to the subtype dissimilarities of the obtained isolates.

Emerging Infectious Diseases, Mar 1, 2020

C ampylobacter jejuni is the most frequent cause of bacterial gastroenteritis in industrialized c... more C ampylobacter jejuni is the most frequent cause of bacterial gastroenteritis in industrialized countries worldwide (1,2), including in Denmark, where ≈4,000 Campylobacter infections are reported annually (3). Despite the high notification rates, Campylobacter infections are believed to be highly underdiagnosed (4,5). Denmark's national surveillance system for Campylobacter is based on observation of the number of notified human cases (3); a substantial number of Campylobacter outbreaks may be overlooked because of a lack of routine microbiological typing of isolates. This hypothesis is supported by evidence from a recent study, in which whole-genome sequencing (WGS)-based typing of selected clinical Campylobacter isolates from patients in Denmark identified numerous small outbreak-like clusters (6). This finding suggests that more outbreaks occur in Denmark than the few typically large outbreaks associated with a single event that are detected by the current surveillance system (7-10). To achieve a national surveillance system that will detect ongoing Campylobacter outbreaks in real time, highly discriminatory subtyping of isolates is needed. Thus, we more comprehensively evaluated the frequency of Campylobacter outbreaks among humans in Denmark by using WGS-based typing. To match the clinical isolates with their sources, we compared them with isolates from food and animals, covering the main putative sources of human Campylobacter infections (i.e., contact with or consumption of animals or animal products, primarily contaminated poultry meat). Although Campylobacter infections are primarily foodborne, a recent case-control study in Denmark found that contact with animals and the environment might account for a substantial proportion of domestic infections (11). Several other reported sources of infection include unpasteurized milk, drinking water, bathing water, vegetables, and fruits (1,12-14). WGS offers high-resolution discriminatory subtyping and has been successfully implemented for

Journal of Applied Microbiology, Feb 12, 2014

 Users may download and print one copy of any publication from the public portal for the purpose... more  Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Epidemiology and Infection, Oct 1, 2003

During the period January 1998-December 2001, all Danish broiler flocks were monitored bacteriolo... more During the period January 1998-December 2001, all Danish broiler flocks were monitored bacteriologically for thermophilic campylobacters and isolates were stored at x80 xC. Six neighbouring broiler farms in a small community were selected for detailed examination of all Campylobacter jejuni isolated (n=180) from these farms during 1998-2000 using Penner serotyping and pulsed-field gel electrophoresis (PFGE). The area and the farms were selected according to their prevalence of campylobacter so that both farms with low and high frequencies of campylobacter positive flocks were included in the study. The frequency of campylobacter positive flocks on the six farms ranged from 24. 5 to 72. 7%. One hundred and eighty of the isolates were C. jejuni (included in this study), 14 isolates were C. coli whereas 7 isolates belonged to other species but were not further identified. By serotyping of all C. jejuni 56 isolates (31. 5%) were assigned to the 4-complex, 32 isolates (18. 0%) to serotype 2, 12 isolates (6. 7 %) to serotype 11, and 11 isolates (6. 2%) were assigned to serotype 12. In three farms, 4-complex was the most prevalent serotype, in one farm it was the second most frequently isolated serotype, while serotypes 2 and 1,44, respectively, were the most frequently isolated from the two remaining farms. This serotype distribution differed from the overall country-wide distribution where serotypes 2 and 1,44 are the most prevalent. All serotype 4-complex isolates from the six selected farms were compared by PFGE to serotype 4-complex isolates from the rest of the country. The results showed that there was a high level of diversity among isolates from the whole country, whereas isolates from the six farms were very homogeneous and only displayed one or a few different PFGE patterns on each farm. It is suggested that certain campylobacter clones persist in a confined geographical area, probably at the farm, and that the broiler houses may be repeatedly infected with a few C. jejuni clones during succeeding broiler flocks. New clones may be introduced, however, the sources and vehicles are yet unknown.

Clinical Microbiology and Infection, Jul 1, 2016

Listeria monocytogenes may contaminate and persist in food production facilities and cause repeat... more Listeria monocytogenes may contaminate and persist in food production facilities and cause repeated, seemingly sporadic, illnesses over extended periods of time. We report on the investigation of two such concurrent outbreaks. We compared patient isolates and available isolates from foods and food production facilities by use of whole-genome sequencing and subsequent multilocus sequence type and single nucleotide polymorphism analysis. Outbreak cases shared outbreak strains, defined as Listeria monocytogenes isolates belonging to the same sequence type with fewer than five single nucleotide polymorphism differences. We performed routine food consumption interviews of L. monocytogenes patients and compared outbreak cases with sporadic cases. Two outbreaks were defined, each consisting of ten outbreak cases in the period 2013e15. Seven outbreak cases and a fetus in gestational week 38 died. Listeria monocytogenes isolates from cold smoked or gravad fish products or their two respective production environments were repeatedly found to belong to the outbreak strains. Outbreak cases more often than sporadic cases stated that they consumed the relevant fish products, odds ratio 10.7. Routine collection and typing of food isolates was key to solving the outbreaks. Furthermore, these outbreaks illustrate the value of whole-genome sequencing for outbreak definition and investigation. Wholegenome sequencing combined with epidemiological investigations provided the discriminatory power to recognize low-intensity, extended time-period outbreaks and link them to food products from two different contaminated production facilities with sufficient strength for food authorities to intervene on. Cold smoked and gravad fish constitute risk products and may be responsible for more listeriosis cases than previously recognized.

Weekly releases (1997–2007), Jun 14, 2007

Eurosurveillance

Background Since 2008, Danish national surveillance of Clostridioides difficile has focused on bi... more Background Since 2008, Danish national surveillance of Clostridioides difficile has focused on binary toxin-positive strains in order to monitor epidemic types such as PCR ribotype (RT) 027 and 078. Additional surveillance is needed to provide a more unbiased representation of all strains from the clinical reservoir. Aim Setting up a new sentinel surveillance scheme for an improved understanding of type distribution relative to time, geography and epidemiology, here presenting data from 2016 to 2019. Methods For 2─4 weeks in spring and autumn each year between 2016 and 2019, all 10 Danish Departments of Clinical Microbiology collected faecal samples containing toxigenic C. difficile. Isolates were typed at the national reference laboratory at Statens Serum Institut. The typing method in 2016–17 used tandem-repeat-sequence typing, while the typing method in 2018–19 was whole genome sequencing. Results During the study period, the sentinel surveillance scheme included ca 14–15% of all...

Eurosurveillance

An outbreak of Salmonella Typhimurium phage type U292 has been ongoing in Denmark since 1 April, ... more An outbreak of Salmonella Typhimurium phage type U292 has been ongoing in Denmark since 1 April, with 1,054 cases registered until 23 October 2008. Extensive investigations including hypothesis-generating interviews, matched case-control studies, cohort studies in embedded outbreaks, shopping list analyses, analyses of food samples from patient's homes, trace-back analyses and extensive microbiological analysis of products have not provided clear indications of a specific source of infection but the main hypothesis is that the vehicle of the outbreak are different pork products. In addition to the large U292 outbreak, at least four other S. Typhimurium outbreaks (caused by phage types U288, DT120, DT3 and DT135) have been investigated in Denmark in 2008.

Weekly releases (1997–2007), 2007

Eurosurveillance, 2006

In May/June 2005 an outbreak of diarrhoeal illness occurred among company employees in Copenhagen... more In May/June 2005 an outbreak of diarrhoeal illness occurred among company employees in Copenhagen. Cases were reported from seven of eight companies that received food from the same catering kitchen. Stool specimens from three patients from two companies were positive for Campylobacter jejuni. We performed a retrospective cohort study among employees exposed to canteen food in the three largest companies to identify the source of the outbreak and to prevent further spread. Using self-administered questionnaires we collected information on disease, days of canteen food eaten and food items consumed. The catering kitchen was inspected and food samples were taken. Questionnaires were returned by 295/348 (85%) employees. Of 247 employees who ate canteen food, 79 were cases, and the attack rate (AR) was 32%. Consuming canteen food on 25 May was associated with illness (AR 75/204, RR=3.2, 95%CI 1.3-8.2). Consumption of chicken salad on this day, but not other types of food, was associated...

Zoonoses and Public Health, 2017

SummaryCampylobacter is the most frequently occurring cause of bacterial gastroenteritis in Europ... more SummaryCampylobacter is the most frequently occurring cause of bacterial gastroenteritis in Europe. Unlike other zoonotic diseases, European‐wide incidences of Campylobacter infections have increased during the past decade, resulting in a significant disease burden. In Denmark, campylobacteriosis is notifiable by laboratory and a unique registration system of electronic transfer and storage of notified Campylobacter cases linked to the national person register of age, gender and geographical location allows collection of comprehensive case data. Using national surveillance data, we describe Campylobacter infections in Denmark from 2000 to 2015, focusing on age‐specific incidences, geography, seasonality and outbreaks. During the observed period, a total of 60,725 Campylobacter infections were registered with a mean annual incidence of 69.3 cases/100,000 population. From 2000 to 2014, the incidence of campylobacteriosis decreased by 20%, followed by an apparent increase of 20% from 2...

Eurosurveillance, 2013

Multiple-locus variable-number of tandem-repeats analysis (MLVA) has emerged as a valuable method... more Multiple-locus variable-number of tandem-repeats analysis (MLVA) has emerged as a valuable method for subtyping bacterial pathogens and has been adopted in many countries as a critical component of their laboratory-based surveillance. Lack of harmonisation and standardisation of the method, however, has made comparison of results generated in different laboratories difficult, if not impossible, and has therefore hampered its use in international surveillance. This paper proposes an international consensus on the development, validation, nomenclature and quality control for MLVA used for molecular surveillance and outbreak detection based on a review of the current state of knowledge.

Journal of Applied Microbiology, 2003

To study the prevalence of seven virulence and toxin genes, and cytolethal distending toxin (CDT)... more To study the prevalence of seven virulence and toxin genes, and cytolethal distending toxin (CDT) production of Campylobacter jejuni and C. coli isolates from Danish pigs and cattle. Methods and Results: The presence of the cadF, ceuE, virB11, flaA, cdtA, cdtB, cdtC and the cdt gene cluster among 40 C. jejuni and C. coli isolates was detected by polymerase chain reaction. The CDT production of the isolates was determined on Vero, colon 205 and chicken embryo cells. The cadF, flaA, ceuE and cdtB genes were detected from 100% of the isolates. The cdtA and cdtC genes were found in 95AE0 and 90AE0% of the isolates, respectively. The cdt gene cluster was detected in 82AE5% isolates. Only 7AE5% of the isolates were positive for virB11. Ninety-five per cent of the isolates produced CDT in Vero and colon 205 cell assays, and 90% of the isolates produced CDT in chicken embryo cell assays. Conclusions: High prevalence of the cadF, ceuE, flaA and cdtB genes was found. Data of the prevalence of cdt genes was consistent with the CDT titres produced by the isolates. Campylobacter coli from pigs produced high CDT titres. Significance and Impact of the Study: The high prevalence of seven virulence and toxin genes demonstrated that these putative pathogenic determinants are widespread among Campylobacter isolates from pigs and cattle. Campylobacter coli isolates from pigs produced much higher CDT titres compared with C. coli isolates from other sources suggesting that C. coli may be particularly adapted to or associated with this species.

Foodborne Pathogens and Disease, 2012

Shigella flexneri is one of the agents most frequently linked to diarrheal illness in developing ... more Shigella flexneri is one of the agents most frequently linked to diarrheal illness in developing countries and often causes outbreaks in settings with poor hygiene or sanitary conditions. Travel is one of the means by which S. flexneri can be imported into developed countries, where this pathogen is not commonly seen. A robust and discriminatory subtyping method is needed for the surveillance of S. flexneri locally and regionally, and to aid in the detection and investigation of outbreaks. The PulseNet International network utilizes standardized pulsedfield gel electrophoresis (PFGE) protocols to carry out laboratory-based surveillance of foodborne pathogens in combination with epidemiologic data. A multicenter validation was carried out in nine PulseNet laboratories located in North and South America, Europe, and Asia, and it demonstrated that a new protocol is highly robust and reproducible for subtyping of S. flexneri. This protocol, already approved for PulseNet laboratories, applies NotI and XbaI as primary and secondary restriction enzymes, respectively, under electrophoresis conditions of initial switch time of 5 s to final switch time of 35 s, at 6 volts/cm.

European Journal of Clinical Microbiology & Infectious Diseases, 2013

Clostridium difficile infection (CDI) is gradually being recognised as a cause of morbidity in th... more Clostridium difficile infection (CDI) is gradually being recognised as a cause of morbidity in the community. We investigated the incidence and clinical characteristics of CDI in a community setting and characterised the C. difficile strains by toxin gene profiling and polymerase chain reaction (PCR) ribotyping. Patients included in the study had attended general practice, primarily because of diarrhoea; CDI patients (259 patients; 121 <2 years of age) had positive cultures for toxigenic C. difficile and non-CDI patients (455 patients) were culture-negative. Outcome variables included the frequency and duration of diarrhoea, vomiting, stomach ache, fever >38 °C, weight loss and sick leave. Data were analysed by logistic regression. CDI patients <2 and ≥2 years of age with C. difficile as the only enteropathogen in the faecal sample reported slimy stools (65% vs. 62%), stomach ache (60% vs. 75%), weight loss (50% vs. 76%) and duration of diarrhoea >15 days (59% vs. 73%) as the predominant symptoms. CDI patients ≥2 years old reported duration of diarrhoea >15 days more often compared to non-CDI patients (73% vs. 27 %, p < 0.0001). The annual incidence of CDI was 518 and 23/100,000 for patients <2 and ≥2 years of age, respectively, and 46/100,000 in the subgroup of patients ≥60 years of age. CDI was characterised by stomach ache and persistent diarrhoea, often leading to weight loss. This emphasises the importance of diagnosing CDI not only in hospitalised patients, but also in individuals ≥2 years of age attending general practice because of gastrointestinal symptoms, especially in the elderly, where the incidence of CDI is high.