An outbreak of Campylobacter jejuni infections associated with food handler contamination: the use of pulsed-field gel electrophoresis

Campylobacter jejuni Foodborne Infection Associated with Cross-contamination: Outbreak in Seoul in 2017

BACKGROUND

In July 2017, there was an outbreak of Campylobacter jejuni infection in three auxiliary police squads in Seoul, Korea. An epidemiological investigation was conducted to identify the cause and source of the illness.

MATERIALS AND METHODS

A retrospective cohort study of all members of the three auxiliary police squads was conducted. Self-administered questionnaires were distributed to all members of the three squads and the food handlers. Rectal swabs were collected from symptomatic police and food handlers.

RESULTS

The overall attack rate was 20.4%, and the epidemic curve indicated a point source type outbreak. Of the 257 auxiliary policemen who consumed the incriminated lunch, 55 met the case definition. Of 36 rectal swabs, 10 were positive for C. jejuni and had the same pulsed-field gel electrophoresis pattern. The major symptoms were loose stool (100%) and abdominal pain (59.3%); the median incubation period was 69 hours. In the univariate epidemiological analysis, watermelon (relative risk [RR], 5.75; 95% confidence interval [CI], 2.14-15.43), half-cut chicken soup (RR, 3.96; 95% CI, 1.49-10.54), steamed rice with millet (RR, 2.73; 95% CI, 1.29-5.77), and radish kimchi (RR, 2.57; 95% CI, 1.45-4.55) were positively associated with the illness. Inspection of the food service facility found that the drainpipe under the meat cleaning sink did not work.

CONCLUSION

This outbreak could have been caused by cross-contamination with C. jejuni from raw chicken via environmental sources.

Association of Paid Sick Leave Laws With Foodborne Illness Rates

INTRODUCTION

Previous studies suggest an association between paid sick leave (PSL) and better population health, including fewer infectious and nosocomial gastrointestinal disease outbreaks. Yet few studies examine whether laws requiring employers to offer PSL demonstrate a similar association. This mixed-methods study examined whether laws requiring employers to provide PSL are associated with decreased foodborne illness rates, particularly laws that are more supportive of employees taking leave.

METHODS

The four earliest PSL laws were classified by whether they were more or less supportive of employees taking leave. Jurisdictions with PSL were matched to comparison jurisdictions by population size and density. Using difference-in-differences, monthly foodborne illness rates (2000-2014) in implementation and comparison jurisdictions before and after the laws were effective were compared, stratifying by how supportive the laws were of employees taking leave, and then by disease. The empirical analysis was conducted from 2015-2017.

RESULTS

Foodborne illness rates declined after implementation of the PSL law in jurisdictions with laws more supportive of employees taking leave, but increased in jurisdictions with laws that are less supportive. In adjusted analyses, PSL laws that were more supportive of employees taking sick leave were associated with an adjusted 22% decrease in foodborne illness rates (p=0.005). These results are driven by campylobacteriosis.

CONCLUSIONS

Although the results suggest an association between more supportive PSL laws and decreased foodborne illness rates, they should be interpreted cautiously because the trend is driven by campylobacteriosis, which has low person-to-person transmission.

Foodborne Infectious Diseases Mediated by Inappropriate Infection Control in Food Service Businesses and Relevant Countermeasures in Korea

Objectives

The objective of this review is to propose an appropriate course of action for improving the guidelines followed by food handlers for control of infection. For this purpose, previous epidemiological reports related to acute gastroenteritis in food service businesses mediated by food handlers were intensively analyzed.

Methods

Relevant studies were identified in international databases. We selected eligible papers reporting foodborne infectious disease outbreaks. Among primary literature collection, the abstract of each article was investigated to find cases that absolutely identified a causative factor to be food handlers’ inappropriate infection control and the taxon of causative microbial agents by epidemiological methodologies. Information about the sites (type of food business) where the outbreaks occurred was investigated.

Results

A wide variety of causative microbial agents has been investigated, using several epidemiological methods. These agents have shown diverse propagation pathways based on their own molecular pathogenesis, physiology, taxonomy, and etiology.

Conclusion

Depending on etiology, transmission, propagation, and microbiological traits, we can predict the transmission characteristics of pathogens in food preparation areas. The infected food workers have a somewhat different ecological place in infection epidemiology as compared to the general population. However, the current Korean Food Safety Act cannot propose detailed guidelines. Therefore, different methodologies have to be made available to prevent further infections.

Assessment of Food Safety Knowledge, Attitude, Self-Reported Practices, and Microbiological Hand Hygiene of Food Handlers

Institutional foodborne illness outbreaks continue to hit the headlines in the country, indicating the failure of food handlers to adhere to safe practices during food preparation. Thus, this study aimed to compare the knowledge, attitude, and self-reported practices (KAP) of food safety assessment and microbiological assessment of food handlers’ hands as an indicator of hygiene practices in food premises. This study involved 85 food handlers working in a university located in Kuala Lumpur, Malaysia. The food safety KAP among food handlers (n = 67) was assessed using a questionnaire; while the hand swabs (n = 85) were tested for the total aerobic count, coliforms, and Escherichia coli, Staphylococcus aureus, Salmonella, Vibrio cholerae and Vibrio parahaemolyticus. The food handlers had moderate levels of food safety knowledge (61.7%) with good attitude (51.9/60) and self-reported practices (53.2/60). It is noteworthy that the good self-reported practices were not reflected in the microbiological assessment of food handlers’ hands, in which 65% of the food handlers examined had a total aerobic count ≥20 CFU/cm² and Salmonella was detected on 48% of the food handlers’ hands. In conclusion, the suggestion of this study was that the food handlers had adequate food safety knowledge, but perceived knowledge failed to be translated into practices at work.

Routes of Transmission in the Food Chain

More than 250 different foodborne diseases have been described to date, annually affecting about one-third of the world's population. The incidence of foodborne diseases has been underreported and underestimated, and the asymptomatic presentation of some of the illnesses, worldwide heterogeneities in reporting, and the alternative transmission routes of certain pathogens are among the factors that contribute to this. Globalization, centralization of the food supply, transportation of food products progressively farther from their places of origin, and the multitude of steps where contamination may occur have made it increasingly challenging to investigate foodborne and waterborne outbreaks. Certain foodborne pathogens may be transmitted directly from animals to humans, while others are transmitted through vectors, such as insects, or through food handlers, contaminated food products or food-processing surfaces, or transfer from sponges, cloths, or utensils. Additionally, the airborne route may contribute to the transmission of certain foodborne pathogens. Complicating epidemiological investigations, multiple transmission routes have been described for some foodborne pathogens. Two types of transmission barriers, primary and secondary, have been described for foodborne pathogens, each of them providing opportunities for preventing and controlling outbreaks. Primary barriers, the most effective sites of prophylactic intervention, prevent pathogen entry into the environment, while secondary barriers prevent the multiplication and dissemination of pathogens that have already entered the environment. Understanding pathogen dynamics, monitoring transmission, and implementing preventive measures are complicated by the phenomenon of superspreading, which refers to the concept that, at the level of populations, a minority of hosts is responsible for the majority of transmission events.

Genotyping of Campylobacter coli strains isolated in Brazil suggests possible contamination amongst environmental, human, animal and food sources

Campylobacter coli and Campylobacter jejuni are two of the most common causative agents of food-borne gastroenteritis in numerous countries worldwide. In Brazil, campylobacteriosis is under diagnosed and under-reported, and few studies have molecularly characterized Campylobacter spp. in this country. The current study genotyped 63 C. coli strains isolated from humans (n512), animals (n521), food (n510) and the environment (n520) between 1995 and 2011 in Brazil. The strains were genotyped using pulsed-field gel electrophoresis (PFGE), sequencing the short variable region (SVR) of the flaA gene ( flaA-SVR) and high-resolution melting analysis (HRMA) of the clustered regularly interspaced short palindromic repeat (CRISPR) locus to better understand C. coli genotypic diversity and compare the suitability of these three methods for genotyping this species. Additionally, the discrimination index (DI) of each of these methods was assessed. Some C. coli strains isolated from clinical and non-clinical origins presented ≥80 % genotypic similarity by PFGE and flaA-SVR sequencing. HRMA of the CRISPR locus revealed only four different melting profiles. In total, 22 different flaA-SVR alleles were detected. Of these, seven alleles, comprising gt1647–gt1653, were classified as novel. The most frequent genotypes were gt30 and gt1647. This distribution reveals the diversity of selected Brazilian isolates in comparison with the alleles described in the PubMLST database. The DIs for PFGE, flaA–SVR sequencing and CRISPR-HRMA were 0.986, 0.916 and 0.550, respectively. PFGE and flaA-SVR sequencing were suitable for subtyping C. coli strains, in contrast to CRISPR-HRMA. The high genomic similarity amongst some C. coli strains confirms the hypothesis that environmental and food sources potentially lead to human and animal contamination in Brazil.

Application of pulsed field gel electrophoresis to type Campylobacter jejuni

Pulsed field gel electrophoresis (PFGE) is generally accepted as one of the most discriminatory methods available for genotyping Campylobacter jejuni. PFGE has been extensively used in epidemiological studies, including outbreak investigation, persistence of genotypes in a human population, environmental diversity of sporadic infection isolates, dissemination of antibiotic-resistant strains, and comparison of genotypes within and between hosts. The main purpose of this chapter is to present a working PFGE protocol for those interested in incorporating this technique in their laboratories.

Are Campylobacter cases low risk for public health follow-up?

OBJECTIVES

Most Campylobacter cases are treated as low risk enterics (LRE) and receive a mailed letter from Toronto Public Health (TPH) with a questionnaire to gather basic risk information. This study sought to identify reasons why Campylobacter cases who were sent this questionnaire did not respond to the letter and to determine whether any of these cases were working in a high-risk occupation.

METHODS

Cases reported to TPH between June 11, 2012 and December 6, 2012 who had not returned the questionnaire within 30 days were telephoned. Participants were asked about awareness of the original letter, reasons for not responding, and whether they worked in a high-risk occupation.

RESULTS

Of the 226 cases identified as not responding to the letter, 172 (76.1%) were reached, and 162 (71.7%) answered the survey questions. The most frequent reason chosen for not responding to the original letter was "forgot" (54.4%). The most common suggestion chosen for ways to encourage response to the original letter was "more information on importance of returning questionnaire" (19.1%). Of the 119 cases with a known occupation, 3 (2.4%) were employed in a sensitive occupation - these include a family physician, a food server, and a line cook. None worked while ill. When prompted with a list of reasons for not returning the questionnaire, the majority of respondents indicated that they "forgot" (54.4%); the next most frequent response was "recovered by illness no longer considered it relevant" (21.5%).

CONCLUSION

To increase response rates in the future, a cover letter should more clearly explain why the response is being solicited by Public Health, even after recovery from the illness, and the form should be simplified for mail return. A very small number of clients originally not reached through the course of the routine LRE program were working in sensitive occupations. Since none reported working while ill, the likelihood of direct or indirect transmission of Campylobacter from these three individuals was low. Using a LRE system to monitor a widespread mostly low-morbidity gastroenteric illness can be an effective public health strategy.

Seasonal diversity of planktonic protists in Southwestern Alberta rivers over a 1-year period as revealed by terminal restriction fragment length polymorphism and 18S rRNA gene library analyses

The temporal dynamics of planktonic protists in river water have received limited attention despite their ecological significance and recent studies linking phagotrophic protists to the persistence of human-pathogenic bacteria. Using molecular-based techniques targeting the 18S rRNA gene, we studied the seasonal diversity of planktonic protists in Southwestern Alberta rivers (Oldman River Basin) over a 1-year period. Nonmetric multidimensional scaling analysis of terminal restriction fragment length polymorphism (T-RFLP) data revealed distinct shifts in protistan community profiles that corresponded to season rather than geographical location. Community structures were examined by using clone library analysis; HaeIII restriction profiles of 18S rRNA gene amplicons were used to remove prevalent solanaceous plant clones prior to sequencing. Sanger sequencing of the V1-to-V3 region of the 18S rRNA gene libraries from spring, summer, fall, and winter supported the T-RFLP results and showed marked seasonal differences in the protistan community structure. The spring library was dominated by Chloroplastidae (29.8%), Centrohelida (28.1%), and Alveolata (25.5%), while the summer and fall libraries contained primarily fungal clones (83.0% and 88.0%, respectively). Alveolata (35.6%), Euglenozoa (24.4%), Chloroplastida (15.6%), and Fungi (15.6%) dominated the winter library. These data demonstrate that planktonic protists, including protozoa, are abundant in river water in Southwestern Alberta and that conspicuous seasonal shifts occur in the community structure.

Association study between an outbreak of Guillain-Barre syndrome in Jilin, China, and preceding Campylobacter jejuni infection

From June to July 2007, 36 cases of Guillain-Barre syndrome (GBS) occurred in a township in north China. Serological study and bacteria culture were performed to investigate the association between preceding Campylobacter jejuni infection and this GBS outbreak. Anti-C. jejuni antibodies were found in significantly higher numbers of GBS patients (IgM 84%, IgG 87.5%) than in healthy inspection cases (IgM 33%, IgG 27%). IgG anti-GM1 was the dominant anti-ganglioside antibody among the GBS patients. Seven C. jejuni isolates (four from human stool and three from poultry specimens taken from the patients' houses) were obtained. Serotyping and molecular analysis were used to investigate the genetic relatedness among these C. jejuni isolates. The four human isolates, collected from residents of the same district, were indistinguishable by both pulsed-field gel electrophoresis and multilocus sequence typing, suggesting these patients had a common source of infection. A new sequence type, sequence type-2993, was assigned to the human C. jejuni isolates, three of which belonged to Penner serotype heat-stable (HS):41. Both serotype and molecular subtype of the human C. jejuni isolates were different from those of isolates obtained from poultry specimens. Our results suggest that the antecedent C. jejuni infection triggered this GBS outbreak in China.

The temporal, PFGE and resistance pattern associations suggest that poultry products are only a minor source of human infections in western Finland

In order to compare human and retail poultry meat thermophilic Campylobacter isolates originating in a regional area in Western Finland, minimum inhibitory concentration (MICs) for six antimicrobials (96 isolates) and pulsed-field gel electrophoresis (PFGE) (102 isolates) were analysed. Campylobacter spp. were detected in 10.5% out of 305 fresh poultry products studied; 29 (90.5%) isolates were identified as Campylobacter jejuni. Among the 70 human isolates, 66 (94.3%) isolates were identified as C. jejuni. Only one C. jejuni domestic poultry isolate showed resistance (ampicillin), whereas domestic human C. jejuni isolates were more commonly resistant to ciprofloxacin, nalidixic acid, ampicillin and tetracycline. The resistance in foreign human isolates was significantly more common than among domestic isolates. PFGE analysis with KpnI restriction enzyme resulted in 59 different PFGE types among the poultry and human isolates. Three types were detected first in poultry meat and thereafter during the following month in domestic human samples, whereas the other conjoint types were detected only after many months. This study suggests that poultry products play only a minor role in human campylobacteriosis in the study area and that the resistance found in domestic human isolates is not likely related to retail poultry meat products.

Genetic and Epidemiological Relationships among Campylobacter Isolates from Humans

84 Campylobacter jejuni isolates from Swedish patients with domestic infection were characterized with pulsed-field gel electrophoresis (PFGE), and the subtype information considered in relation to epidemiological data. Based on pattern combinations from restriction cleavage with SmaI and SalI, 52 different PFGE types were identified. Types with an average pattern similarity of at least 82% and 63% were assembled in groups and clusters, respectively. The 2 largest clusters included 71% of the isolates. The distribution in time varied between different groups and clusters, where some were isolated sporadically during the whole period and others appeared more concentrated in time. Types in 1 cluster were significantly more often isolated in summer than other types in the study. Isolates from children showed lower pattern similarity to other isolates than isolates from adults. Sets of type and time related cases, possibly representing small outbreaks, were identified when indistinguishable PFGE patterns were found in isolates from temporally related cases. Our results indicate that although a large number of genotypes may be found among C. jejuni strains infecting humans, a large proportion of these may be genetically related, and that different genotypes may appear during different seasons and infect individuals of different ages.

Cooking practices in the kitchen-observed versus predicted behavior

Cross-contamination and undercooking are major factors responsible for campylobacteriosis and as such should be incorporated in microbiological risk assessment. A previous paper by van Asselt et al.((1)) quantified cross-contamination routes from chicken breast fillet via hand, cutting board, and knife ending up in a prepared chicken-curry salad in the domestic kitchen. The aim of the current article was to validate the obtained transfer rates with consumer data obtained by video observations and microbial analyses of a home prepared chicken-curry salad. Results showed a wide range of microbial contamination levels in the final salad, caused by various cross-contamination practices and heating times varying from 2'44'' to 41'30''. Model predictions indicated that cooking times should be at least 8 minutes and cutting boards need to be changed after cutting raw chicken in order to obtain safe bacterial levels in the final salad. The model predicted around 75% of the variance in cross-contamination behavior. Accuracy of the model can further be improved by including other cross-contamination routes besides hands, cutting boards, and knives. The model proved to be fail-safe, which implies it can be used as a worst-case estimate to assess the importance of cross-contamination in the home.

Population-attributable risk estimates for risk factors associated with Campylobacter infection, australia

One-sentence summary: Each year, an estimated 50,500 cases in persons >5 years of age can be directly attributed to consumption of chicken.

In 2001–2002, a multicenter, prospective case-control study involving 1,714 participants >5 years of age was conducted in Australia to identify risk factors for Campylobacter infection. Adjusted population-attributable risks (PARs) were derived for each independent risk factor contained within the final multivariable logistic regression model. Estimated PARs were combined with adjusted (for the >5 years of age eligibility criterion) notifiable disease surveillance data to estimate annual Australian Campylobacter case numbers attributable to each risk factor. Simulated distributions of “credible values” were then generated to model the uncertainty associated with each case number estimate. Among foodborne risk factors, an estimated 50,500 (95% credible interval 10,000–105,500) cases of Campylobacter infection in persons >5 years of age could be directly attributed each year to consumption of chicken in Australia. Our statistical technique could be applied more widely to other communicable diseases that are subject to routine surveillance.

Efficacy of an extended theory of planned behaviour model for predicting caterers' hand hygiene practices

The main aim of this study was to determine the factors which influence caterers' hand hygiene practices using social cognitive theory. One hundred and fifteen food handlers from 29 catering businesses were observed carrying out 31,050 food preparation actions in their workplace. Caterers subsequently completed the Hand Hygiene Instrument (HHI), which ascertained attitudes towards hand hygiene using constructs from the Theory of Planned Behaviour (TPB) and the Health Belief Model. The TPB provided a useful framework for understanding caterers' implementation of hand hygiene practices, explaining 34% of the variance in hand hygiene malpractices (p < 0.05). Five components were identified as significant predictors of hand hygiene malpractices: attitudes, subjective norms, descriptive norms, perceived behavioural control and intention (p < 0.05). Thus, suggesting that hand hygiene practices cannot be improved solely through the provision of information to individuals. Effective interventions may need to focus on changing the organisational food safety culture.

Introduction to United States Department of Agriculture VetNet: status of Salmonella and Campylobacter databases from 2004 through 2005

In 2003 the United States Department of Agriculture established USDA VetNet. It was modeled after PulseNet USA, the national molecular subtyping network for foodborne disease surveillance. The objectives of USDA VetNet are: to use pulsed-field gel electrophoresis (PFGE) to subtype zoonotic pathogens submitted to the animal arm of the National Antimicrobial Resistance Monitoring System (NARMS); examine VetNet and PulseNet PFGE patterns; and use the data for surveillance and investigation of suspected foodborne illness outbreaks. Whereas PulseNet subtypes 7 foodborne disease-causing bacteria- Escherichia coli O157:H7, Salmonella, Shigella, Listeria monocytogenes, Campylobacter, Yersinia pestis, and Vibrio cholerae-VetNet at present subtypes nontyphoidal Salmonella serotypes and Campylobacter from animals, including diagnostic specimens, healthy farm animals, and carcasses of food-producing animals at slaughter. By the end of 2005, VetNet had two functioning databases: the NARMS Salmonella and the NARMS Campylobacter databases. The Salmonella database contained 6763 Salmonella isolates and 2514 unique XbaI patterns, while the Campylobacter database contained 58 Campylobacter isolates and 53 unique SmaI patterns. Both databases contain the PFGE tagged image file format (TIFF) images, demographic information, and the antimicrobial resistance profiles assigned by NARMS. In the future, veterinary diagnostic laboratories will be invited to participate in VetNet. The establishment of USDA VetNet enhances the mission of the agriculture and public health communities in the surveillance and investigation of foodborne illness outbreaks.

Campylobacter jejuni multilocus sequence types in humans, northwest England, 2003-2004

MLST can be used to describe and analyze the epidemiology of campylobacteriosis in distinct human populations.

Detailed understanding of the epidemiology of Campylobacter is increasingly facilitated through use of universal and reproducible techniques for accurate strain differentiation and subtyping. Multilocus sequence typing (MLST) enables discriminatory subtyping and grouping of isolate types into genetically related clonal complexes; it also has the advantage of ease of application and repeatability. Recent studies suggest that a measure of host association may be distinguishable with this system. We describe the first continuous population-based survey to investigate the potential of MLST to resolve questions of campylobacteriosis epidemiology. We demonstrate the ability of MLST to identify variations in the epidemiology of campylobacteriosis between distinct populations and describe the distribution of key subtypes of interest.

Descripción de un brote de gastroenteritis por Campylobacter jejuni y caracterización molecular de la cepa implicada

INTRODUCTION

The aim of this study is to describe an outbreak of diarrhea caused by Campylobacter jejuni in a primary school.

METHODS

Stool samples from five patients were cultured. Molecular typing of the isolated strains was performed using PCR-RFLP-flaA, PFGE and MLST.

RESULTS

Campylobacter jejuni was isolated from all five patients. Two of the five strains were available for typing. The DNA patterns of the two isolates were indistinguishable.

CONCLUSION

The results suggest that the causal strain had a common identity.

Estimated Numbers of Community Cases of Illness Due to Salmonella, Campylobacter and Verotoxigenic Escherichia Coli: Pathogen-specific Community Rates

OBJECTIVE

To estimate the annual number of cases of illness due to verotoxigenic Escherichia coli (VTEC), Salmonella and Campylobacter in the Canadian population, using data from the National Notifiable Disease registry (NND), estimates of under-reporting derived from several National Studies on Acute Gastrointestinal Illness, and the literature.

METHODS

For each of the three pathogens (VTEC, Salmonella and Campylobacter), data were used to estimate the percentage of cases reported at each step in the surveillance system. The number of reported cases in the NND for each pathogen was then divided by these percentages. In cases where the pathogen-specific estimates were unavailable, data on acute gastrointestinal illness were used, accounting for differences between those with bloody and nonbloody diarrhea.

RESULTS

For every case of VTEC, Salmonella and Campylobacter infection reported in the NND, there were an estimated 10 to 47, 13 to 37, and 23 to 49 cases annually in the Canadian population, respectively.

CONCLUSIONS

The authors estimate that a significant number of infections due to VTEC, Salmonella and Campylobacter occur each year in Canada, highlighting the fact that these enteric pathogens still pose a significant health burden. Recognizing the significant amount of under-reporting is essential to designing appropriate interventions and assessing the impact of these pathogens in the population.

Outbreak of infection with hepatitis A virus (HAV) associated with a foodhandler and confirmed by sequence analysis reveals a new HAV genotype IB variant

An outbreak of infection with hepatitis A virus associated with a foodhandler and involving 26 subjects occurred in Southern Italy. Sequence analysis of the VP3-VP1 and VP1-P2A junctions confirmed that the outbreak was due to a point source and allowed the identification of a new genotype IB variant. This report confirms the usefulness of sequence-based molecular fingerprinting during outbreaks.

An outbreak of gastroenteritis from a non-chlorinated community water supply

STUDY OBJECTIVE

To determine the source and the extent of a community wide outbreak of gastroenteritis.

DESIGN

A matched case-control study with postal questionnaires. Subtyping of campylobacter strains by pulsed field gel electrophoresis (PFGE).

SETTING

A rural municipality with a population of 8600 in southern Finland, August 2000. Two thirds of the population receive non-chlorinated ground water from the municipal water supply.

PARTICIPANTS

Cases were randomly selected among residents of the municipality who contacted the municipal health centre because of gastroenteritis and had illness onset between 31 July and 20 August 2000. Community controls were identified from the population registry and matched according to sex, year of birth, and postal code.

MAIN RESULTS

Four hundred and sixty three persons contacted the municipal health centre because of gastroenteritis. Campylobacter jejuni was isolated from stool samples of 24 persons. One hundred and thirty seven cases and 388 controls were enrolled in the case-control study. In multivariate analysis, drinking unboiled water from the municipal supply was significantly associated with illness (odds ratio 11.1, 95% confidence interval 1.4 to 90.2). C jejuni was isolated from one tap water sample. The water isolate and all but one of the patient isolates were indistinguishable by PFGE.

CONCLUSIONS

Combining epidemiological investigation with molecular subtyping methods provided strong evidence that water was the source of the outbreak. Non-chlorinated small ground water systems may be susceptible to waterborne outbreaks and constitute a risk to rural populations.

Diversities and similarities in PFGE profiles of Campylobacter jejuni isolated from migrating birds and humans

AIMS

To genetically sub-type Campylobacter jejuni strains isolated from migratory birds, and to compare these with clinical strains collected in the same area and corresponding time period, with the aim to increase our knowledge on sub-types occurring among wild birds and their possible impact on human disease.

METHODS AND RESULTS

We sub-typed C. jejuni strains from migrating birds (n = 89) and humans (n = 47), using macrorestriction profiling by pulsed-field gel electrophoresis. Isolates from migrant birds often exhibited sub-types with higher levels of similarity to isolates from birds of the same species or feeding guild, than to isolates from other groups of birds. Likewise, could the vast majority of sub-types found among the migrant bird isolates not be identified among sub-types from human cases. Only two bird strains, one from a starling (Sturnus vulgaris) and one from a blackbird (Turdus merula), had sub-types that were similar to some of the human strain sub-types.

CONCLUSIONS

Isolates from one bird species, or feeding guild, often exhibited high similarities, indicating a common transmission source for individuals, or an association between certain sub-types of C. jejuni and certain ecological guilds or phylogenetic groups of birds. Sub-types occurring among wild birds were in general distinctively different from those observed in patients. The two bird isolates that were similar to human strains were isolated from bird species that often live in close associations with human settlements.

SIGNIFICANCE AND IMPACT OF STUDY

Wild birds have often been mentioned as a potential route for transmission of C. jejuni to humans. Our study demonstrates that strains isolated from birds most often are different from clinical strains, but that some strain similarities occur, notably in birds strongly associated with human activities.

Risk factors associated with Campylobacter jejuni infections in Curaçao, Netherlands Antilles

A steady increase in the incidence of Guillain-Barré syndrome (GBS) with a seasonal preponderance, almost exclusively related to Campylobacter jejuni, and a rise in the incidence of laboratory-confirmed Campylobacter enteritis have been reported from Curaçao, Netherlands Antilles. We therefore investigated possible risk factors associated with diarrhea due to epidemic C. jejuni. Typing by pulsed-field gel electrophoresis identified four epidemic clones which accounted for almost 60% of the infections. One hundred six cases were included in a case-control study. Infections with epidemic clones were more frequently observed in specific districts in Willemstad, the capital of Curaçao. One of these clones caused infections during the rainy season only and was associated with the presence of a deep well around the house. Two out of three GBS-related C. jejuni isolates belonged to an epidemic clone. The observations presented point toward water as a possible source of Campylobacter infections.

Utility of multilocus sequence typing as an epidemiological tool for investigation of outbreaks of gastroenteritis caused by Campylobacter jejuni

Multilocus sequence typing (MLST) has been proven useful for the study of the global population structure of Campylobacter jejuni; however, its usefulness for the investigation of outbreaks of disease caused by C. jejuni has not been proven. In this study, MLST plus sequencing of the flaA short variable region (SVR) were applied to 47 isolates from 12 outbreaks of C. jejuni infection whose relatedness has been determined previously, and the results were compared to those of serotyping and pulsed-field gel electrophoresis (PFGE). Isolates implicated in an outbreak were indistinguishable by all four subtyping methods, with sporadic isolates being distinguished from outbreak isolates. Two sporadic isolates from one outbreak were resistant to SmaI digestion and therefore nontypeable by PFGE but were differentiated from the outbreak strain by the other methods. PFGE and flaA SVR typing were the most discriminatory methods, with discriminatory indices (DI) of 0.930 and 0.923, respectively. However, an epidemic strain from one outbreak was distinguished from the other outbreak isolates by flaA SVR typing; its flaA allele was different at five nucleotides, suggesting that this change was possibly mediated by recombination. MLST was less discriminatory than PFGE and flaA SVR typing (DI = 0.859), and many of the epidemic strains possessed common sequence types (STs) including ST-8, -21, -22, and -42. However, further discrimination within STs was achieved by flaA SVR typing or PFGE. The results from this study demonstrate that a combined approach of MLST plus flaA SVR typing provides a level of discrimination equivalent to PFGE for outbreak investigations.

Molecular epidemiology in the public health and hospital environments

The increasing speed and ease of genomic sequencing coupled with available funding to sequence multiple, unrelated strains of the same species will lead inevitably to the identification of candidate genes that can be used as molecular typing tools (MLST, SLST, microarray approach). However, it is important to note that even the most sophisticated typing tool should never replace a full epidemiologic investigation in which all available information is taken into account. Nevertheless, the typing methods discussed in this article and those yet to be developed have significantly improved the quality of health care worldwide.

Application of single-strand conformation polymorphism and denaturing gradient gel electrophoresis for fla sequence typing of Campylobacter jejuni

Campylobacter jejuni is a frequent cause of bacterial gastroenteritis in humans all over the world. Several molecular typing methods are used to study the epidemiology of Campylobacter spp. infections. The aim of the present study was to investigate the application of single-strand conformation polymorphism (SSCP) and denaturing gradient gel electrophoresis (DGGE) analysis as rapid primary subtyping methods for C. jejuni. A variable fragment from the 3' end of the flaA to the 3' end of the intergenic region, separating the flaA and flaB genes, was subjected to SSCP and DGGE analysis. A total of 48 clinical C. jejuni isolates, 49 C. jejuni strains isolated from poultry, 2 strains isolated from ducks and 1 strain isolated from a pheasant were assigned to 24 distinct SSCP patterns. Sequence analysis of the respective DNA fragments revealed that every different fla sequence type could be distinguished by SSCP. DGGE proved to be equally discriminatory. Both methods can be applied as primary subtyping methods, because pulsed-field gel electrophoresis (PFGE) and amplified fragment length polymorphism (AFLP) analysis further differentiated isolates belonging to the same fla sequence types.

Campylobacter spp in human, chickens, pigs and their antimicrobial resistance

Campylobacter spp. have been identified as etiologic agents in outbreaks and sporadic cases of gastroenteritis in developed countries. In developing countries, most reported Campylobacter infections are in children. Previously reported prevalences of Campylobacter spp. in children in Southeast Asia range from 2.9% to 15%. The frequency and pattern of occurrence of Campylobacter spp. differ between developed and developing countries, especially in the number of cases reported in adults and the presence of any seasonal patterns in occurrence. Although the severity of Campylobacter infection in adults was different between developed and developing countries, the clinical symptoms of infection in adults resulting from infection in developing countries was similar to those in developed countries. Many different animal species maintain Campylobacter spp. with no clinical signs. There do not appear to be significantly different colonization rates of Campylobacter in food animals between developed and developing countries. The role of C. jejuni as a primary pathogen in farm animals is uncertain. C. jejuni can be found in feces of diarrheic and healthy calves and piglets. Campylobacter with resistance to antimicrobial agents have been reported in both developed and developing countries, and the situation seems to deteriorate more rapidly in developing countries, where there is widespread and uncontrolled use of antibiotics resistance was observed at high levels in food animals in both developed and developing countries. Studies suggested an association between antimicrobial use in food animals and the development of resistance in human isolates in developed countries.

Foodborne illness: new developments concerning an old problem

Foodborne illnesses continue to cause substantial morbidity and mortality in the United States, primarily as gastroenteritis but occasionally as other syndromes as well. Most of these illnesses are caused by a variety of widely known infectious agents, principally viruses, and are probably the result of common mistakes in food handling in the home or in restaurants. The epidemiology of foodborne illness is evolving. Major changes in food production, distribution, and consumption have created opportunities for new pathogens to emerge and for old ones to reemerge, and the potential for widespread outbreaks is increasing. Antibiotic resistance in bacterial pathogens resulting from the widespread use of antimicrobial agents in animal husbandry is also an important concern. Clinicians must be aware of the changing epidemiology of foodborne illness to recognize and manage these conditions in the clinical setting. In addition, clinicians are critical in the reporting of recognized or suspected foodborne illness, so that public health authorities are able to investigate, understand, and ultimately better control them. A number of new techniques have been employed, and others under development will improve our ability to recognize and cope with foodborne diseases.

Comparison of pulsed-field gel electrophoresis and amplified fragment length polymorphism techniques for investigating outbreaks of enteritis due to campylobacters

Campylobacters are the most commonly reported cause of acute bacterial enteritis in the United Kingdom and United States, with poultry, milk, and water implicated as sources or vehicles of infection. The majority of campylobacter infections are sporadic, although outbreaks may occur, and these provide an opportunity to evaluate genotypic fingerprinting techniques. In this study, pulsed-field gel electrophoresis (PFGE) was compared with single-enzyme-amplified fragment length polymorphism (SAFLP). The results for the three separate episodes indicated that SAFLP and PFGE both clustered the strains from the first incident as 100% homologous. The strains from the second and third incidents clustered as distinct from both the first incident and from each other. PFGE is well recognized as a discriminatory fingerprinting technique for campylobacters; however, SAFLP has proven to be equally discriminatory, but far less labor intensive and with the added advantages of less "hands-on" time and inexpensive equipment, it is an excellent alternative to PFGE for investigation of outbreaks.

Determinants of cluster distribution in the molecular epidemiology of tuberculosis

Recently developed molecular techniques have revolutionized the epidemiology of tuberculosis. Multiple studies have used these tools to examine the population structure of Mycobacterium tuberculosis isolates in different communities. The distributions of clusters of M. tuberculosis isolates in these settings may variously reflect social mixing patterns or the differential fitness of specific clones of the organism. We developed an individual-based microsimulation of tuberculosis transmission to explore social and demographic determinants of cluster distribution and to observe the effect of transmission dynamics on the empiric data from molecular epidemiologic studies. Our results demonstrate that multiple host-related factors contribute to wide variation in cluster distributions even when all strains of the organism are assumed to be equally transmissible. These host characteristics include interventions such as chemotherapy, vaccination and chemoprophylaxis, HIV prevalence, the age structure of the population, and the prevalence of latent tuberculosis infection. We consider the implications of these results for the interpretation of cluster studies of M. tuberculosis as well as the more general application of microsimulation models to infectious disease epidemiology.

Evaluation of methods for subtyping Campylobacter jejuni during an outbreak involving a food handler

In October 1998, the Centers for Disease Control and Prevention (CDC) assisted in an investigation of an outbreak of campylobacteriosis at a school in Salina, Kansas. Twenty-two isolates were submitted from the Kansas state public health laboratory to CDC, 9 associated with the outbreak and 13 epidemiologically unrelated sporadic isolates. Pulsed-field gel electrophoresis (PFGE) using SmaI and SalI was initially used to validate the epidemiologic data. We then tested the ability of other subtyping techniques to distinguish the outbreak-associated isolates from unrelated sporadic isolates. The methods employed were somatic O serotyping, PCR-restriction fragment length polymorphism (RFLP) analysis of flaA, DNA sequence analysis of 582 bp of flaA that included the short variable region (SVR), and sequencing of the entire flaA gene. PFGE was the most discriminatory technique, yielding 11 SmaI and 10 SalI restriction profiles. All outbreak isolates were indistinguishable by PFGE, somatic O serotyping, and sequencing of the 582-bp region of the flaA gene. fla typing by PCR-RFLP grouped one sporadic isolate with the outbreak strain. Analysis of the DNA sequence of a 582-bp segment of flaA produced strain groupings similar to that generated by PCR-RFLP but further differentiated two flaA PCR-RFLP types (with a 1-bp difference in the 582-bp region). Two sporadic strains were distinct by flaA PCR-RFLP but differed only by a single base substitution in the 582-bp region. The entire flaA gene was sequenced from strains differing by a single base pair in the 582-bp region, and the data revealed that additional discrimination may in some cases be obtained by sequencing outside the SVR. PFGE was superior to all other typing methods tested for strain discrimination; it was crucial for understanding the Kansas outbreak and, when SmaI was used, provided adequate discrimination between unrelated isolates.