A mixed foodborne outbreak with Salmonella heidelberg and Campylobacter jejuni in a nursing home

Investigation of an Acute Gastrointestinal Illness Outbreak Linked to Drinking Water in a Higher Educational Institute in East Sikkim, India

Introduction An acute gastrointestinal illness outbreak was reported in a higher educational institution among students and faculties in East Sikkim, India, from January to February 2023. The investigation was conducted to identify the source of the infection and causative pathogens and prevent the spread of the outbreak. Methods We defined a case as three or more loose stools in 24 hours, abdominal pain, or vomiting with the onset of symptoms between January 16 and February 16, 2023. Active surveillance was conducted by reviewing the affected individuals at the campus and patient registers at the dispensary, where cases were treated. Stool samples, rectal swabs, water samples, and suspected food samples were collected for microbiological testing using conventional culture, multiplex polymerase chain reaction (PCR), and kit-based real-time PCR methods. Results Out of 1,850 residents, 106 (5.7%) were affected by gastrointestinal symptoms like diarrhea, vomiting, etc. The attack rate for females was 23 (1.24%) and for males was 83 (4.49%). The most affected individual median age was 21 years (range: 2-51 years). From the laboratory investigations, most of the cases demonstrated polymicrobial etiologies. Gastroenteritis pathogens like Campylobacter, astrovirus, androtavirusdiarrheagenic Escherichia coli (DEC) (EAEC, EIEC, ETEC, EPEC, and EAEC), Shigella,etc., were detected in the suspected samples. The environmental investigation indicated the presence of rusted and leaky water pipes and sewage pipelines, along with ineffective chlorination of the water plant. Conclusions Based on epidemiological and laboratory investigations, it is conjectured that sewage and fecal contamination of drinking water and poor maintenance of the water distribution system most likely caused the outbreak described in this study. Basic treatment modalities, adequate chlorination, and periodic inspection of the water system were suggested, which controlled the outbreak to a greater extent.

Non-Typhoidal Salmonella at the Human-Food-of-Animal-Origin Interface in Australia

Non-typhoidal Salmonella is a major zoonotic pathogen that plays a significant role in foodborne human salmonellosis worldwide through the consumption of contaminated foods, particularly those of animal origin. Despite a considerable reduction in human salmonellosis outbreaks in developed countries, Australia is experiencing a continuous rise of such outbreaks in humans. This review of the literature highlights the reported non-typhoidal Salmonella outbreaks in humans as well as the occurrence of the pathogen in foods from animal sources throughout Australia. Non-typhoidal Salmonella infections from food animals are more often associated with at-risk people, such as immunocompromised and aged people or children. Although several animal-sourced foods were recognised as the catalysts for salmonellosis outbreaks in Australia, egg and egg-based products remained the most implicated foods in the reported outbreaks. This review further highlights the antimicrobial resistance trends of non-typhoidal Salmonella isolates at the human-food interface, with a focus on clinically important antimicrobials in humans, by collating evidence from previous investigations in Australia. The rise in antimicrobial-resistant Salmonella, especially to antimicrobials commonly prescribed to treat human salmonellosis, has become a significant global public health concern. However, the overall prevalence of antimicrobial resistance in Australia is considerably lower than in other parts of the world, particularly in terms of critically important antimicrobials for the treatment of human salmonellosis. The present review adds to our understanding of the global epidemiology of non-typhoidal Salmonella with emphasis on the past few decades in Australia.

Large outbreak of multiple gastrointestinal pathogens associated with fresh curry leaves in North East England, 2013

A total of 592 people reported gastrointestinal illness following attendance at Street Spice, a food festival held in Newcastle-upon-Tyne, North East England in February/March 2013. Epidemiological, microbiological and environmental investigations were undertaken to identify the source and prevent further cases. Several epidemiological analyses were conducted; a cohort study; a follow-up survey of cases and capture re-capture to estimate the true burden of cases. Indistinguishable isolates of Salmonella Agona phage type 40 were identified in cases and on fresh curry leaves used in one of the accompaniments served at the event. Molecular testing indicated entero-aggregative Escherichia coli and Shigella also contributed to the burden of illness. Analytical studies found strong associations between illness and eating food from a particular stall and with food items including coconut chutney which contained fresh curry leaves. Further investigation of the food supply chain and food preparation techniques identified a lack of clear instruction on the use of fresh uncooked curry leaves in finished dishes and uncertainty about their status as a ready-to-eat product. We describe the investigation of one of the largest outbreaks of food poisoning in England, involving several gastrointestinal pathogens including a strain of Salmonella Agona not previously seen in the UK.

Outbreak of foodborne gastroenteritis in a senior high school in South-eastern Ghana: a retrospective cohort study

BACKGROUND

On 4th February 2015, a group of Senior High School students from Fanteakwa district presented to the emergency unit of the district hospital with complaints of abdominal pain, vomiting and diarrhoea. All the students had eaten from a specific food vendor and had neither eaten any other common meal that day nor the previous day. A foodborne disease outbreak was suspected. We investigated to verify the outbreak, determine its magnitude, identify the source and implement control measures.

METHODS

A retrospective cohort study was conducted. We reviewed medical records and interviewed patrons of the food vendor. We collected data on age, sex, signs and symptoms, date of illness onset, date of admission, date of discharge, treatments given and outcome. A case of foodborne disease was any person in the school with abdominal pain, vomiting and or diarrhoea from 4th to 11th February 2015 and had eaten from the food vendor. We conducted active case search to identify more cases. We conducted environmental assessment and collected clinical and food samples for laboratory testing. Descriptive and inferential statistical analyses were performed using Stata 12.0.

RESULTS

A total of 68 cases were recorded giving overall attack rate of 35.79 % (68/190) with no death. Of these, 51.47 % (35/68) were males. Mean age of case-patients was 17.8 (standard deviation +/-1.62). The index case, a 17-year-old female student ate from the food vendor on 4th February at 9:00 am and fell ill at 3:40 pm later that day. Compared to those who ate other food items, students who drank water from container at the canteen were more likely to develop foodborne disease at statistically significant levels [RR = 2.6, 95 % CI = (2.11-3.15)]. Clostridium perfringens (C. perfringens) and Salmonella species (Salmonella spp) were isolated from water and stew respectively. Clinical features of case-patients were compatible with both organisms.

CONCLUSION

A foodborne gastroenteritis outbreak occurred in a Senior High School in Fanteakwa District from 4th to 7th February 2015. The most probable aetiologic agent was C. perfringens with contaminated water at canteen as the vehicle of transmission. Concurrent Salmonella spp infection could not be ruled out. Rapid outbreak response helped in controlling the outbreak.

Epidemiologic data and pathogen genome sequences: a powerful synergy for public health

Epidemiologists aim to inform the design of public health interventions with evidence on the evolution, emergence and spread of infectious diseases. Sequencing of pathogen genomes, together with date, location, clinical manifestation and other relevant data about sample origins, can contribute to describing nearly every aspect of transmission dynamics, including local transmission and global spread. The analyses of these data have implications for all levels of clinical and public health practice, from institutional infection control to policies for surveillance, prevention and treatment. This review highlights the range of epidemiological questions that can be addressed from the combination of genome sequence and traditional ‘line lists’ (tables of epidemiological data where each line includes demographic and clinical features of infected individuals). We identify opportunities for these data to inform interventions that reduce disease incidence and prevalence. By considering current limitations of, and challenges to, interpreting these data, we aim to outline a research agenda to accelerate the genomics-driven transformation in public health microbiology.

Specific discrimination of three pathogenic Salmonella enterica subsp. enterica serotypes by carB-based oligonucleotide microarray

It is important to rapidly and selectively detect and analyze pathogenic Salmonella enterica subsp. enterica in contaminated food to reduce the morbidity and mortality of Salmonella infection and to guarantee food safety. In the present work, we developed an oligonucleotide microarray containing duplicate specific capture probes based on the carB gene, which encodes the carbamoyl phosphate synthetase large subunit, as a competent biomarker evaluated by genetic analysis to selectively and efficiently detect and discriminate three S. enterica subsp. enterica serotypes: Choleraesuis, Enteritidis, and Typhimurium. Using the developed microarray system, three serotype targets were successfully analyzed in a range as low as 1.6 to 3.1 nM and were specifically discriminated from each other without nonspecific signals. In addition, the constructed microarray did not have cross-reactivity with other common pathogenic bacteria and even enabled the clear discrimination of the target Salmonella serotype from a bacterial mixture. Therefore, these results demonstrated that our novel carB-based oligonucleotide microarray can be used as an effective and specific detection system for S. enterica subsp. enterica serotypes.

An overview of transducers as platform for the rapid detection of foodborne pathogens

The driving advent of portable, integrated biosensing ways for pathogen detection methods offers increased sensitivity and specificity over traditional microbiological techniques. The miniaturization and automation of integrated detection systems present a significant advantage for rapid, portable detection of foodborne microbes. In this review, we have highlighted current developments and directions in foodborne pathogen detection systems. Recent progress in the biosensor protocols toward the detection of specific microbes has been elaborated in detail. It also includes strategies and challenges for the implementation of a portable platform toward rapid foodborne sensing systems.

Campylobacter immunity and coinfection following a large outbreak in a farming community

An outbreak of campylobacteriosis affected approximately one-half of 165 people attending an annual farmers' dance in Montrose, Scotland, in November 2005. Epidemiological investigations, including a cohort study (n = 164), identified chicken liver paté as the most likely vehicle of infection. Paté preparation involved deliberate undercooking of chicken livers by flash-frying, followed by mechanical homogenization. Typing of 32 Campylobacter strains (isolated from submitted stools) by multilocus sequence typing identified four distinct clades of Campylobacter jejuni. There was good agreement when isolates were typed by Penner serotyping, pulsed-field gel electrophoresis, and flaA short variable region sequencing but poorer agreement with phage and antibiotic susceptibility testing. At least three attendees were coinfected with two Campylobacter strains each. The outbreak was probably due to several livers contributing Campylobacter strains that survived undercooking and were dispersed throughout the paté. The study highlights improper culinary procedures as a potential human health risk and provides a striking counterexample to the "dominant outbreak strain" view of point source outbreaks of food-borne infections. It also demonstrates that previous exposure to biologically plausible sources of Campylobacter may confer protection against subsequent infection.

Antimicrobial resistance in Salmonella enterica serovar Heidelberg isolates from retail meats, including poultry, from 2002 to 2006

Salmonella enterica serovar Heidelberg frequently causes food-borne illness in humans. There are few data on the prevalence, antimicrobial susceptibility, and genetic diversity of Salmonella serovar Heidelberg isolates in retail meats. We compared the prevalences of Salmonella serovar Heidelberg in a sampling of 20,295 meats, including chicken breast (n = 5,075), ground turkey (n = 5,044), ground beef (n = 5,100), and pork chops (n = 5,076), collected during 2002 to 2006. Isolates were analyzed for antimicrobial susceptibility and compared genetically using pulsed-field gel electrophoresis (PFGE) and PCR for the bla(CMY) gene. A total of 298 Salmonella serovar Heidelberg isolates were recovered, representing 21.6% of all Salmonella serovars from retail meats. One hundred seventy-eight (59.7%) were from ground turkey, 110 (36.9%) were from chicken breast, and 10 (3.4%) were from pork chops; none was found in ground beef. One hundred ninety-eight isolates (66.4%) were resistant to at least one compound, and 49 (16.4%) were resistant to at least five compounds. Six isolates (2.0%), all from ground turkey, were resistant to at least nine antimicrobials. The highest resistance in poultry isolates was to tetracycline (39.9%), followed by streptomycin (37.8%), sulfamethoxazole (27.7%), gentamicin (25.7%), kanamycin (21.5%), ampicillin (19.8%), amoxicillin-clavulanic acid (10.4%), and ceftiofur (9.0%). All isolates were susceptible to ceftriaxone and ciprofloxacin. All ceftiofur-resistant strains carried bla(CMY). PFGE using XbaI and BlnI showed that certain clones were widely dispersed in different types of meats and meat brands from different store chains in all five sampling years. These data indicate that Salmonella serovar Heidelberg is a common serovar in retail poultry meats and includes widespread clones of multidrug-resistant strains.

A Salmonella Typhimurium 197 outbreak linked to the consumption of lambs' liver in Sydney, NSW

We identified an increase in the number of cases of Salmonella Typhimurium phage type 197 in New South Wales in February 2005. Cases were predominantly of Lebanese descent. To identify risk factors for illness, we conducted an unmatched case-control study including 12 cases and 21 controls. Eight of 12 cases (67%) and no controls reported eating lambs' liver (OR incalculable, P<0.05), and seven of nine cases (78%) and one of 21 controls (5%) reported eating fresh fish (OR 70.0, P<0.05). Among participants who did not eat liver, there was a strong association between eating fish and illness (OR 60.0, P<0.05). The fish was from divergent sources. Five cases had bought the liver from two different butcher's shops, which obtained the lambs' liver from a single abattoir. Consumption of liver is a risk for salmonellosis. Traditional dishes may place some ethnic groups at increased risk of foodborne disease.

Food Safety Guidance for Older Adults

Aging is associated with loss of the physical barriers and immune efficiency that typically control pathogens' access to and multiplication within the body, thus making infection more likely in elderly persons. Chronic diseases and other health factors, such as malnutrition and immobility, may increase susceptibility to and severity of infections, including foodborne illnesses, in elderly persons, as well as associated morbidity and mortality. Prevention is the best way to avoid foodborne illnesses, but older adults have long-established food preparation and handling practices, some of which may increase the likelihood of illness. Elderly persons rely on physicians as trusted sources of health information. Physicians and other health care professionals can help prevent and control foodborne diseases by educating their patients about the risks of foodborne illness, providing sound advice on safe food-handling and consumption practices, making rapid appropriate diagnoses, and reporting cases promptly to public health authorities.

Temporal clusters of Salmonella serovars in humans in Alberta, 1990-2001

BACKGROUND

Temporal clusters of salmonellosis are believed to occur but have not been quantitatively explored, thus, our objectives were to describe trends, seasonal patterns, and clusters of salmonellosis in humans in Alberta by examining isolates reported through passive surveillance systems.

METHODS

Cases of salmonellosis reported through Notifiable Disease Records between January 1990 and December 2001 were obtained from Alberta Health and Wellness. Least squares regression was used to characterize the distribution (long-term trends and seasonal patterns) of isolates. A cluster detection test was used to determine if and when isolates of specific serovars aggregated in time, over and above the background distribution. Comparisons were made to temporal patterns in Alberta livestock and to known outbreaks in humans.

RESULTS

S. Typhimurium, Enteritidis, Hadar, Heidelberg, and Thompson were the five most common serovars of the 9,188 isolates reported. The annual number of isolates was relatively stable over time, with a distinct summertime seasonal pattern. Clusters were observed in 23 of 32 serovars examined. More clusters occurred in September and October than in other months, and in 1998 through 2001 than in the early to mid-1990s. Also, more clusters were of short duration than long.

INTERPRETATION

Short-duration clusters likely indicate a point source of infection, while long-duration clusters may indicate exposure to a persistent common source or the occurrence of secondary infections. A sharp increasing trend and a large cluster of S. Heidelberg may have public health implications. Surveillance activities focussed on similarities between common serovars, trends, and temporal clusters in humans and animals, and studies on factors associated with autumn clusters may be useful in preventing outbreaks in humans.

Phage-based typing scheme for Salmonella enterica serovar Heidelberg, a causative agent of food poisonings in Canada

Salmonella enterica serovar Heidelberg is perhaps the second most frequent Salmonella serovar isolated from humans and the most common isolated from animals in Canada. This pathogen has shown increasing resistance to antimicrobial agents and mimics the multidrug resistance observed in S. enterica serovar Typhimurium strain DT 104. However, unlike for serovar Typhimurium, a rapid and inexpensive subtyping method has not been available for large-scale surveillance efforts. We developed a phage typing scheme and subtyped 2,523 strains of serovar Heidelberg from outbreaks, sporadic infections, and environmental sources in Canada between January 1991 and December 2000. All strains were sensitive to one or more phages and could be subdivided into 49 phage types. A total of 196 isolates from 13 major outbreaks could be subtyped into six phage types, while 86 strains from family outbreaks were assigned to seven phage types. All strains were typeable, and epidemiologically related strains isolated from patients and implicated foods had identical phage types, antibiograms, and pulsed-field gel electrophoresis (PFGE) patterns. Combining PFGE with phage typing increased the discriminatory power of the analysis beyond that of either method alone. We concluded that this phage typing scheme, in conjunction with PFGE, enhances subtyping of serovar Heidelberg strains. Furthermore, this phage typing scheme is a rapid, economical, stable, and reliable epidemiologic tool for tracing the origin of food-borne disease and for the surveillance of sporadic infections.

Molecular epidemiology of Salmonella Heidelberg in an equine hospital

From 1992 to 1997, multi-drug resistant (MDR) Salmonella Heidelberg isolates were cultured from a number of horses hospitalised in a veterinary hospital in Victoria, Australia. To examine the relationships between the cases, 28 isolates from the hospital were compared by pulsed field gel electrophoresis (PFGE), IS200 element profiles, antimicrobial resistance patterns, plasmid profiles and phage typing. The PFGE patterns following digestion with XbaI and BlnI restriction endonucleases showed that the isolates from the veterinary hospital originated from a common source. These isolates also had indistinguishable IS200 profiles. However, PFGE was more discriminatory than IS200 profiles. All the veterinary hospital isolates and one independent isolate had the same antimicrobial resistance pattern and had at least one plasmid in common. Localisation of antimicrobial resistance genes indicated that the veterinary hospital isolates had more than one plasmid carrying resistance genes and that the genes encoding sulphathiazole and trimethoprim resistance were not on these plasmids. Phage typing was ineffective as 22 of the 28 isolates were untypeable. In conclusion, the combination of different methods used for epidemiological studies suggested that a single strain of MDR S. Heidelberg was isolated from horses admitted to the hospital for 6 years and caused salmonellosis in susceptible horses within that period with no apparent correlation between the antimicrobials used and retention of its MDR phenotype.

Emerging health care-associated infections in the geriatric population

The increasing number of persons >65 years of age form a special population at risk for nosocomial and other health care-associated infections. The vulnerability of this age group is related to impaired host defenses such as diminished cell-mediated immunity. Lifestyle considerations, e.g., travel and living arrangements, and residence in nursing homes, can further complicate the clinical picture. The magnitude and diversity of health care-associated infections in the aging population are generating new arenas for prevention and control efforts.

Identification, assessment and management of food-related microbiological hazards: historical, fundamental and psycho-social essentials

Microbiological risk assessment aimed at devising measures of hazard management, should take into account all perceived hazards, including those not empirically identified. It should also recognise that safety cannot be "inspected into" a food. Rather hazard management should be the product of intervention strategies in accordance with the approach made mandatory in the EU Directive 93/43 and the USDA FSIS Pathogen Reduction HACCP system; Final Rule. It is essential too that the inherent variability of the biological attributes affecting food safety is recognised in any risk assessment. The above strategic principles may be conceptualised as a four-step sequence, involving (i) identification and quantification of hazards; (ii) design and codification of longitudinally integrated ("holistic") technological processes and procedures to eliminate, or control growth and metabolism of, pathogenic and toxinogenic organisms; (iii) elaboration of microbiological analytical standard operating procedures, permitting validation of "due diligence" or responsible care, i.e. adherence to adopted intervention strategies. This should be supported by empirically assessed reference ranges, particularly for marker organisms, while the term "zero tolerance" is refined throughout to tolerable safety limit; (iv) when called for, the need to address concerns arising from lay perceptions of risk which may lack scientific foundation. In relation to infectious and toxic hazards in the practical context the following general models for quantitative holistic risk assessment are presented: (i) the first order, basic lethality model; (ii) a second approximation taking into account the amount of food ingested in a given period of time; (iii) a further adjustment accounting for changes in colonization levels during storage and distribution of food commodities and the effects of these on proliferation of pathogens and toxin production by bacteria and moulds. Guidelines are provided to address: (i) unsubstantiated consumer concern over the wholesomeness of foods processed by an innovative procedure; and (ii) reluctance of small food businesses to adopt novel strategies in food safety. Progress here calls for close cooperation with behavioural scientists to ensure that investment in developing measures to contain risk deliver real benefit.