Foodborne Gastroenteritis Outbreaks Research Articles

Year-Round Prevalence of Norovirus in the Environment of Catering Companies without a Recently Reported Outbreak of Gastroenteritis

Food handlers play an important role in the transmission of norovirus (NoV) in food-borne outbreaks of gastroenteritis (GE). In a year-round prevalence study, the prevalence of NoV in catering companies without recently reported outbreaks of GE was investigated and compared to the observed prevalence in catering companies with recently reported outbreaks. Swab samples were collected from surfaces in the kitchens and (staff) bathrooms in 832 randomly chosen companies and analyzed for the presence of NoV RNA. In total, 42 (1.7%) out of 2,496 environmental swabs from 35 (4.2%) catering companies tested positive. In contrast, NoV was detected in 147 (39.7%) of the 370 samples for 44 (61.1%) of the 72 establishments associated with outbreaks of gastroenteritis. NoV-positive swabs were more frequently found in winter, in specific types of companies (elderly homes and lunchrooms), and in establishments with separate bathrooms for staff. We found a borderline association with population density but no relation to the number of employees. Sequence analysis showed that environmental strains were interspersed with strains found in outbreaks of illness in humans. Thus, the presence of NoV in catering companies seemed to mirror the presence in the population but was strongly increased when associated with food-borne GE. Swabs may therefore serve as a valuable tool in outbreak investigations for the identification of the causative agent, although results should be interpreted with care, taking into account all other epidemiological data.

Foodborne gastroenteritis outbreak in an Austrian healthcare facility caused by asymptomatic, norovirus-excreting kitchen staff

An outbreak of norovirus GGII.4 2006b affected an Austrian 600-bed healthcare facility from 15 to 27 March 2009. A total of 204 patients, residents and staff fitted the outbreak case definition; 17 (8.3%) were laboratory-confirmed. Foodborne origin was suspected in the 114 patient and resident cases with onset 15-18 March. A case-cohort study was performed to test the hypothesis that consumption of dishes offered on 14, 15 and 16 March (risk days) was associated with increased risk of infection. Data on food exposure of 62% (317/510) of the patient and resident cohort were available for a simultaneous retrospective cohort study. The case-cohort analysis revealed that consumption of sliced cold sausage offered on 15 March [odds ratio (OR): 3.98; 95% confidence interval (CI): 1.18-14.1], a meat dish with salad (adjusted OR: 2.2; 95% CI: 1.19-4.08) and a rolled spinach pancake (adjusted OR: 2.17; 95% CI: 1.27-3.71) on 16 March were independent risk factors. It is likely that one of the five asymptomatic excretors among the kitchen staff on duty on the risk days was the source of food contamination. The case-cohort study design was found to be a valid alternative to the retrospective cohort study design for the investigation of a suspected foodborne outbreak in a large cohort.

A Case of Liver Abscess and Bacteremia Caused byVibrio choleraeNon-O1

Vibrio cholerae non-O1 have caused several well-studied food-borne outbreaks of gastroenteritis and also have been responsible for sporadic cases of otitis media, wound infection, and bacteremia. Few cases of liver abscess caused by Vibrio cholerae non-O1 have been reported. A 73-year-old man with underlying diabetes mellitus was admitted with nausea, vomiting, dyspepsia and febrile sensation. We identified Vibrio cholerae non-O1 in his blood cultures and multiple hepatic microabscess on abdominal computed tomography. He was treated with systemic antibiotics and fluid therapy, but died due to septic shock on sixth day. We report here, a case of liver abscess with bacteremia due to Vibrio cholerae non-O1 in a patient with diabetes mellitus.

Differential features of foodborne gastroenteritis outbreaks of known and unknown etiology.

Foodborne diseases (FBD) are a major cause of disease and death, but their etiologies are not always known. Factors associated with determination of the etiologic agent of FBD outbreaks reported to the Department of Health in Catalonia (Spain) during 2002 to 2005 were studied. For each outbreak, the year, number of persons affected, hospitalization, and availability of samples from patients, food handlers, and foods were collected. The delay between the date of onset of symptoms of the second case and the report to the surveillance unit was calculated. The relationship between explanatory variables and determination of the cause of each outbreak was studied by logistic regression. The causal agent was identified in 242 (73.3%) of 330 outbreaks. Factors associated with determining the etiologic agent of the outbreak in the univariate analysis were availability of samples from cases (odd ratio [OR] of 6.0, 95% confidence interval [CI] of 3.2 to 11.1), hospitalization (OR of 5.1, 95% CI of 2.6 to 11.1), availability of samples from food handlers (OR of 2.7, 95% CI of 1.6 to 4.5), size > or = 10 cases (OR of 2.2, 95% CI of 1.3 to 3.2), availability of samples from food (OR of 1.8, 95% CI of 1.1 to 3.0), and the last year (2005) of the study period (OR of 1.9, 95% CI of 1.0 to 3.6). In the multivariate analysis, hospitalization (adjusted OR of 5.1, 95% CI of 2.4 to 11.2), size > or = 10 cases (adjusted OR of 2.1, 95% CI of 1.2 to 3.7), and the year 2005 (OR of 2.1, 95% CI of 1.1 to 4.0) remained associated. Collection and processing of clinical samples from cases and appropriate laboratory diagnoses of all possible etiologies of FBD, including viruses, are very important. Efforts by physicians and public health services to coordinate and improve their activity in these areas may help provide more accurate knowledge concerning the etiologies of FBD outbreaks and lead to more effective preventive procedures.

A food-borne outbreak of Shigella sonnei gastroenteritis, Austria, 2008

We report on the first foodborne outbreak of Shigella sonnei described in Austria. On July 14 2008, AGES was informed of a cluster of 22 laboratory-confirmed cases of infection with S. sonnei restricted to public health district X in the province of Salzburg. All cases had attended a youth-group trip to a small village in the province of Tyrol from July 7 to July 9. An outbreak case among the trip participants was a person who (1) attended the trip and (2) fell ill with diarrhea in the period between July 8 and July 12. Among the 61 trip participants, 42 fitted the outbreak case definition, including 31 culture-confirmed cases. A household outbreak case was a person who (1) did not participate in the trip, (2) fell ill with diarrhea not before July 10 and (3) had household contact with an outbreak case between one and three days before onset of illness. Of the 11 household outbreak cases, 10 were tested by stool culture and four of these had a laboratory-confirmed S. sonnei infection. In addition, one of the two hostel staff tested positive for S. sonnei. All 36 isolates were biotype gl, lysotype 12, and were indistinguishable from each other by PFGE. A cohort study among the trip participants revealed a risk ratio of 2.71 for consumption of salad (on at least 1 of the 3 days of the trip) (95% CI: 1.38-5.32, P = 0.004). Among the 42cases, 34 could be explained by consumption of salad. The landlady of the hostel, who prepared the salad with bare hands, was a carrier and was assumed to be the source of contamination of the salad. Without proper epidemiological analytical investigation of this shigellosis outbreak, its association with food consumption would not have been identified.

An Outbreak of Food-Borne Gastroenteritis Due to Sapovirus among Junior High School Students

The human sapovirus (SaV) causes acute gastroenteritis mainly in infants and young children. A food-borne outbreak of gastroenteritis associated with SaV occurred among junior high school students in Yokohama, Japan, during and after a study trip. The nucleotide sequences of the partial capsid gene derived from the students exhibited 98% homology to a SaV genogroup IV strain, Hu/Angelholm/SW278/2004/SE, which was isolated from an adult with gastroenteritis in Solna, Sweden. An identical nucleotide sequence was detected from a food handler at the hotel restaurant, suggesting that the causative agent of the outbreak was transmitted from the food handler. This is the first description of a food-borne outbreak associated with the SaV genogroup IV strain in Japan.

USE OF PHAGE TYPING COMBINED WITH PULSED-FIELD GEL ELECTROPHORESIS AND POLYERASE CHAIN REACTION IN CHARACTERIZATION OF HUMAN SALMONELLA ENTERITIDIS ISOLATES

Phage typing (PT) combined with pulsed-field gel electrophoresis (PFGE) and Polymerase chain reaction (PCR) analysis methods, using 3 kinds of primers ( ERIC, SERE, RAPD) was used in order to characterize human isolates of Salmonella Enteritidis strains. Thirty-six epidemiologically unrelated isolates from outbreaks of foodborne gastroenteritis were studied. Analysis with Xba I, Bln I and Spe I enzymes showed that Xba I gave the highest index of discrimination among strains. Molecular typing by PCR methods was not able to differentiate the isolates belonging to different phage types. We identified eight phage types, with a predominance of PT 8 (42% of isolates). Three PFGE pattern types were obtained with Xba I restriction endonuclease enzyme among the unrelated isolates. The establishment of a highly reliable and discriminatory method for epidemiologic analysis is necessary in order to trace the sources of specific pathogens and, consequently, to control and prevent the spread of epidemic Salmonella Enteritidis isolates to humans. It is concluded that PFGE, in combination with phage typing, represents a suitable tool for the epidemiological typing of Salmonella Enteritidis strains which could be used for investigations or surveillance of the international spread of these clones

A rapid procedure for detecting noroviruses from cheese and fresh lettuce

Noroviruses (NoVs) are recognized as the most common agents of outbreaks of food-borne viral gastroenteritis and the efficiency of different methods for detection of NoVs from food matrices have been tested in several laboratories worldwide. The aim of this study was to develop a rapid and sensitive method for recovery of NoVs by using a filtration concentration method followed by PCR amplification for detection of NoVs from cheese and fresh lettuce. Experimentally, a fecal suspension containing different number of NoVs copies was spiked in the food surface and extracted by a direct elution using a Stomacher® apparatus. An Ozone-Safe solvent Vertrel XF® treatment was included for cheese samples for removing particulate matter. The watery phase was collected and the viral concentration was performed by the adsorption–elution method using negatively charged membranes with inorganic solvents in a Stericup® and afterwards ultrafiltered using a Centriprep Concentrator® 50 to obtain a final volume of 2ml. RNA isolation was carried out with the QIAamp Viral RNA Mini Kit® available commercially and reverse transcription was carried out with a Pd(N6) random primer. Real time quantitative PCR (TaqMan®) and qualitative PCR were used for molecular detection of NoVs. The recovery rate of NoVs ranged from 5.2 to 72.3% in lettuce and from 6 to 56.3% in cheese. The results indicate that this method is suitable for detection of NoVs contamination in food and will help establish the cause and source of NoVs outbreaks of food-borne illness.

Enteroaggregative Escherichia coli associated with a foodborne outbreak of gastroenteritis

This study investigated two foodborne outbreaks of gastroenteritis that occurred 10 days apart among individuals who had meals at the restaurant of a farm holiday resort. Mild gastrointestinal symptoms were reported and none of the patients needed hospitalization. Mean incubation times were 45 and 33 h, and the overall attack rates were 43.5 and 58.3%, respectively. Stool sample examination was negative for common enteric pathogens in both outbreaks. Specimens from 13 people involved in the second outbreak and 3 restaurant staff were examined for diarrhoeagenic Escherichia coli. An enteroaggregative E. coli (EAEC) strain of serotype O92:H33 was isolated from six participants and one member of staff. In particular, the EAEC strain was isolated from five of the six cases of diarrhoea examined. The strain showed an aggregative pattern of adherence to HEp-2 cells, did not produce a biofilm and possessed the virulence-related genes aat, aggR, aap and set1A, but not the astA gene. A retrospective cohort study indicated a pecorino cheese made with unpasteurized sheep milk as the possible source (P<0.001). Samples of the cheese had E. coli counts higher than 10(6) c.f.u. g(-1), but the outbreak EAEC strain was not isolated. This report confirms that EAEC infections are probably underdiagnosed because of the limited availability of laboratories capable of identifying this group of pathogenic E. coli.

Foodborne outbreak of gastroenteritis due to Norovirus and Vibrio parahaemolyticus

Vibrio parahaemolyticus and Norovirus have been recognized as the cause of sporadic cases or outbreaks of diarrhoeal illness in association with the ingestion of raw or improperly cooked seafood. This report describes a foodborne outbreak of gastroenteritis caused by both Norovirus and Vibrio parahaemolyticus following the consumption of raw seafood in a restaurant in Terrassa (Catalonia, Spain) in September 2005. Measures are needed to reduce contamination of raw seafood. Consumers can reduce the risk of foodborne illness by avoiding consumption of raw or undercooked food.

Highly Sensitive and Specific PCR Assay for Reliable Detection of Cyclospora cayetanensis Oocysts

Multiple outbreaks of food-borne gastroenteritis caused by the coccidian parasite Cyclospora cayetanensis have been reported annually in North America since 1995. Detection of C. cayetanensis contamination typically relies on laborious and subjective microscopic examination of produce washes. Molecular detection methods based on nested PCR, restriction fragment length polymorphism, or multiplex PCR have been developed for C. cayetanensis; however, they have not been adequately validated for use on food products. Further challenges include reliably extracting DNA from coccidian oocysts since their tough outer wall is resistant to lysis and overcoming PCR inhibitors in sample matrices. We describe preliminary validation of a reliable DNA extraction method for C. cayetanensis oocysts and a sensitive and specific novel PCR assay. The sensitivity and repeatability of the developed methods were evaluated by multiple DNA extractions and PCR amplifications using 1,000-, 100-, 10-, or 1-ooycst aliquots of C. cayetanensis oocysts in water or basil wash sediment. Successful PCR amplification was achieved on 15 and 5 replicates extracted from aliquots containing 1,000 oocysts in water and basil wash, respectively. All 45 replicates of the 100-oocyst aliquots in water and 5 in basil wash were amplified successfully, as were 43/45 and 41/45 of the 10- and 1-oocyst aliquots in water and 9/15 and 2/15 in basil wash, respectively. The developed primers showed no cross-reactivity when tested against bacteria, nematodes, and protozoans, including Eimeria, Giardia, and Cryptosporidium. Our results indicate that these methods are specific, can reliably detect a single oocyst, and overcome many of the limitations of microscopic diagnosis.

Statistical analysis of attack rate in norovirus foodborne outbreaks

Norovirus (NoV), which causes foodborne gastroenteritis outbreaks, is one of the important viruses in public health. We statistically analyzed the attack rate in foodborne outbreaks caused by NoV. The attack rate in 95 oyster-associated outbreaks was significantly higher than that in 195 food handler-associated outbreaks ( P = 0.007). The difference in the number of NoV genotypes implicated is considered to be an important factor for this difference. The attack rate in 20 outbreaks associated only with GII/3 was higher than that in 143 other outbreaks ( P = 0.247), while the attack rate in 27 outbreaks associated only with GII/4 was lower than that in 136 other outbreaks ( P = 0.004), suggesting that GII/4 NoVs cause asymptomatic infection more frequently than do other NoV genotypes. Our results suggest that differences in implicated foods, susceptibility of the host to NoV infection, and pathogenicity of NoVs may influence the attack rate in NoV foodborne outbreaks.

Small round viruses: classification and role in food-borne infections.

Since the first observation of Norwalk virus in the electron microscope in 1972, many different small virus particles in the size range 20-40 nm have been described world-wide in association with outbreaks of gastroenteritis. Progress characterizing these agents has been hampered by the relatively small numbers of particles present in clinical material and the lack of success in culturing them. Although the relationship between some of these viruses remains confusing, a number of distinct groups has emerged, based on morphological features and limited physical data. Immuno-electron microscopy has proved valuable in detecting viruses but the addition of antibody can mask surface morphological features. Examination of viruses in negatively stained preparations without added antibody has revealed distinct morphological differences and viruses previously thought to be simply antigenic variants within the Norwalk group of viruses clearly belong to other groups. Preliminary evidence suggests that one human virus unrelated to Norwalk has a single-stranded DNA genome and is a parvovirus. Some groups have been implicated in outbreaks of food-borne gastroenteritis, particularly after the consumption of shellfish, and their role in other food-borne and water-borne outbreaks is being increasingly recognized.

Foodborne Salmonella-Caused Outbreaks in Catalonia (Spain), 1990 to 2003

In most developed countries, nontyphoid Salmonella is an important cause of sporadic cases and outbreaks of foodborne gastroenteritis. The aim of this study was to investigate the trend of foodborne Salmonella-caused outbreaks and number of cases, hospitalizations, and deaths and compare them with those caused by other infectious agents. The study was carried out in Catalonia, a region in northeastern Spain with a population of 6.5 million inhabitants, in 2002. All information on reported outbreaks of foodborne disease from 1990 to 2003 was reviewed. For each outbreak, the following variables were collected: year; setting (household, restaurant, school, hospital, nursing home, and others); number of cases, hospitalizations, and deaths; causal agent; and food vehicle involved. Of 1,652 reported outbreaks, 1,078 had a known causal agent. Among them, 871 (80.8%) were caused by Salmonella, with 14,695 cases, 1,534 hospitalizations, and 4 deaths. The rate of hospitalization was higher in outbreaks due to Salmonella than in those caused by other infectious agents (rate ratio, 2.54; 95% confidence interval, 2.20 to 2.94). Forty-eight percent of Salmonella-caused outbreaks were eggborne, compared with 5.3% of those caused by other infectious agents (rate ratio, 1.40; 95% confidence interval, 1.33 to 1.48). The annual number of cases in household outbreaks of eggborne Salmonella rose over time (R2 = 0.82), but the number of outbreaks produced in other settings did not. Eggborne outbreaks caused by Salmonella in households are a major cause of disease, and increased preventive efforts are necessary, especially consumer education and awareness of the risk of eating food containing raw or slightly cooked eggs.

Detection ofVibrio parahaemolyticusin Shellfish by Use of Multiplexed Real-Time PCR with TaqMan Fluorescent Probes

We developed a multiplexed real-time PCR assay using four sets of gene-specific oligonucleotide primers and four TaqMan probes labeled with four different fluorophores in a single reaction for detection of total and pathogenic Vibrio parahaemolyticus, including the pandemic O3:K6 serotype in oysters. V. parahaemolyticus has been associated with outbreaks of food-borne gastroenteritis caused by the consumption of raw or undercooked seafood and therefore is a concern to the seafood industry and consumers. We selected specific primers and probes targeting the thermostable direct hemolysin gene (tdh) and tdh-related hemolysin gene (trh) that have been reported to be associated with pathogenesis in this organism. In addition, we targeted open reading frame 8 of phage f237 (ORF8), which is associated with a newly emerged virulent pandemic serotype of V. parahameolyticus O3:K6. Total V. parahaemolyticus was targeted using the thermolabile hemolysin gene (tlh). The sensitivity of the combined four-locus multiplexed TaqMan PCR was found to be 200 pg of purified genomic DNA and 10(4) CFU per ml for pure cultures. Detection of an initial inoculum of 1 CFU V. parahaemolyticus per g of oyster tissue homogenate was possible after overnight enrichment, which resulted in a concentration of 3.3x10(9) CFU per ml. Use of this method with natural oysters resulted in 17/33 samples that were positive for tlh and 4/33 samples that were positive for tdh. This assay specifically and sensitively detected total and pathogenic V. parahaemolyticus and is expected to provide a rapid and reliable alternative to conventional detection methods by reducing the analysis time and obviating the need for multiple assays.

Are Noroviruses Emerging?

Are Noroviruses Emerging?

Gastroenteritis Due to Listeria monocytogenes

It has been known for a long time that many patients experience diarrhea antecedent to the development of bacteremia or meningoencephalitis due to Listeria monocytogenes, but it was only recently that convincing evidence was obtained that this organism can cause acute, self-limited, febrile gastroenteritis in healthy persons. At least 7 outbreaks of foodborne gastroenteritis due to L. monocytogenes have been reported. Illness typically occurs 24 h after ingestion of a large inoculum of bacteria and usually lasts 2 days. Common symptoms include fever, watery diarrhea, nausea, headache, and pains in joints and muscles. L. monocytogenes should be considered to be a possible etiology in outbreaks of febrile gastroenteritis when routine cultures fail to yield a pathogen.

Epidemiology of acute gastroenteritis outbreaks caused by Noroviruses in Okayama, Japan

Noroviruses (called formerly "Norwalk-like viruses") cause food-borne gastroenteritis outbreaks. These outbreaks were thought to be related to shellfish consumption, although non-shellfish related outbreaks also occurred frequently in Japan. To clarify the epidemiology of Norovirus outbreaks, 435 stool samples were collected from 60 acute non-bacterial gastroenteritis outbreaks occurring over 8 years in Okayama, Japan. Using reverse transcription-PCR (RT-PCR), Noroviruses were detected in 257 cases (59.1% of all samples) from 46 outbreaks (77% of all outbreaks). The majority of the 46 Norovirus outbreaks (89%) occurred during November to March; notably one-third occurred in December. Restaurants, schools, and welfare institutions accounted for the major settings in 50%, 20%, and 15% of the Norovirus outbreaks, respectively. This was similar to other reports from Japan, but differed from those from the United Kingdom. The transmission routes were assigned in 27 of the Norovirus outbreaks. In 18 outbreaks the routes were related to human contact (7 from food handlers and 11 from person-to-person contact), whereas those related directly to shellfish occurred only in 9 outbreaks. These results suggest that transmission routes related to human contact are more important than recognized previously in the context of preventive medicine. Furthermore, all outbreaks in which some of the samples contained dual genogroups of Noroviruses were related to shellfish, suggesting that consumption of contaminated shellfish frequently results in mixed Norovirus infections in contrast to other transmission routes and that coexistence of genogroups is a useful marker for shellfish-related outbreaks.

Detection of multiple enteric virus strains within a foodborne outbreak of gastroenteritis: an indication of the source of contamination

An outbreak of acute gastroenteritis of suspected viral aetiology occurred in April 2003 in the British Royal Fleet Auxiliary ship (RFA) Argus deployed in the Northern Arabian Gulf. There were 37 cases amongst a crew of 400 personnel. Of 13 samples examined from cases amongst the crew, six enteric viruses were detected by reverse transcriptase polymerase chain reaction (RT-PCR). Five different viruses were identified including, three norovirus genotypes, a sapovirus and a rotavirus. No multiple infections were detected. A common food source was implicated in the outbreak and epidemiological analysis showed a statistically significant association with salad as the source of the outbreak, with a relative risk of 3.41 (95% confidence interval of 1.7-6.81) of eating salad on a particular date prior to the onset of symptoms. Faecal contamination of the salad at source was the most probable explanation for the diversity of viruses detected and characterized.

Detection of noroviruses in raspberries associated with a gastroenteritis outbreak

Following an acute foodborne gastroenteritis outbreak in southern Sweden, stool specimens from five of nine ill patients were found positive for norovirus using reverse transcriptase polymerase chain reaction. Epidemiological data pointed to raspberry cakes as the source of the outbreak. Using a combination of generic and patient-specific primers and novel food analysis methodology (with extraction efficiency control and inhibitor removal), norovirus strains from two different genogroups were directly identified in the contaminated raspberries.