Viruses, bacterial toxins possible causes of food poisoning in E-Bridge case, say analysts
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While tests commissioned by E-bridge operator Etonhouse had suggested no contamination, the food poisoning could have been caused by other bacteria or viruses, say experts.
ST PHOTO: GAVIN FOO
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- Initial tests on food from E-Bridge pre-schools showed no contamination, but experts warn results may not be conclusive due to potential bacterial toxins.
- SFA data indicates 2024 had 53 major gastroenteritis cases, with caterers responsible for the most outbreaks between 2018-2021.
- Experts suggest enhanced monitoring for caterers, better food safety education, and stiffer penalties to avoid future outbreaks.
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SINGAPORE – Though preliminary results from tests conducted on food linked to 185 cases of gastroenteritis infections recently
On Nov 21, 173 pupils and 12 employees from six E-Bridge pre-schools reported gastroenteritis symptoms after consuming food supplied by Middleton International School. Such symptoms include vomiting and diarrhoea.
EtonHouse International Education Group, which operates E-Bridge pre-schools, said on Nov 24 that preliminary results from tests conducted on food samples showed that they were not contaminated
EtonHouse said the central kitchen had sent samples of the catered food for microbiological testing at Merieux NutriSciences AQ (Singapore) Lab, separate from the tests being conducted by the Singapore Food Agency (SFA).
According to the National Centre for Infectious Diseases, the most common bacteria associated with food poisoning are Campylobacter jejuni, Salmonella, Staphylococcus aureus, Vibrio parahaemolyticus, Bacillus cereus and E.coli.
However, gastroenterologist Benjamin Yip, medical director of Alpha Digestive and Liver Centre, noted that while the lab had tested for six common bacteria found in contaminated food, there are many more bacteria and viruses that can cause food poisoning.
Other bacteria associated with food poisoning include Shigella – responsible for infecting more than 17,000 people in the United States in 2023 – while viruses include the norovirus, linked to 24 gastroenteritis cases at E-Bridge Pre-School’s Dawson Road centre in September.
Professor William Chen, director of Nanyang Technological University’s Future Ready Food Safety Hub (FRESH), said these pathogens are not detectable using the method to detect the six common bacteria.
He noted that food poisoning can also be caused by toxins released by bacteria, which can cause tissue damage.
These are often resistant to heat, and thus may not be destroyed during the cooking process and could still cause food poisoning, he explained.
“It is not clear from the report if the bacterial toxins – which require different (testing) techniques than those used to detect bacteria – were also investigated by the reported lab,” said Prof Chen.
Checks could also be conducted to ensure that proper sampling of the food was done, he added.
53 major gastroenteritis cases in 2024
There were 53 major gastroenteritis cases in 2024, according to SFA data, 44 cases in 2023 and 57 in 2022. Food-borne cases were responsible for most of the incidents over the three years, and accounted for 31 cases in 2024.
The number of reported food-borne illness cases per 100,000 population was 22.8 in 2024.
Besides gastroenteritis, other food-borne illnesses include hepatitis A and listeria, which causes aches and fever, and can lead to death in more serious cases.
As more than half of these food-borne illness cases involve catered food, SFA carried out more targeted checks on food establishments supplying catered food, the agency said in its Singapore Food Statistics 2024 publication.
A study by researchers from SFA, the Ministry of Health (MOH), Nanyang Technological University and the National University of Singapore found that between 2018 and 2021, caterers were responsible for the most food-borne gastroenteritis outbreaks investigated by SFA and MOH.
The study defined gastroenteritis outbreaks as two or more cases of food poisoning symptoms linked to a food establishment.
Published in the International Journal of Environmental Research and Public Health in January 2024, the study found that during that period, caterers were linked to 51 outbreaks.
In comparison, restaurants and in-house kitchens were responsible for 18 and 15 outbreaks respectively.
The higher rate of food poisoning among caterers could be due to poor personal hygiene practices and inadequate temperature control of food, said Dr Yip.
Pathogens multiply most rapidly when food is between 5 deg C and 60 deg C. Under current regulations, catered cooked food should be consumed within four hours if it is not kept chilled below 5 deg C or hot above 60 deg C.
The study also recorded 50 non-food-borne gastroenteritis outbreaks during that period, almost all of which were in schools, with researchers noting that environmental swabs in affected pre-schools tested positive for norovirus.
This could point to the need for greater awareness of proper cleaning and disinfection of pre-school premises, as well as proper screening of children for signs of gastroenteritis, the researchers said.
These and other possible factors – such as cross-contamination between raw and cooked items as well as insufficient cooking – are details that catering companies should pay attention to, Dr Yip said.
“These issues are often exacerbated when handling large volumes of food and during peak periods,” he noted, advising that customers should also be vigilant and discard food that does not taste right.
An enhanced monitoring and reporting system could be introduced to ensure a safe food preparation environment at such vendors, Prof Chen said, noting that FRESH is developing “new and proactive data-driven techniques to predict possible food poisoning”.
Statistics for major gastroenteritis incidents in 2025 are not yet available, though ST reported at least five outbreaks this year
The earlier incidents involved students from the School of the Arts, Raffles Girls’ Primary School and three different pre-schools, including one in late September involving 20 pupils and four employees at E-Bridge Pre-School’s centre in Dawson Road.
Young children are more vulnerable to food poisoning as their immune system is not yet strong, said Prof Chen.
The November incident comes ahead of 13 schools here adopting a central kitchen model in January, amid challenges in attracting stallholders for school canteens.
Operators must be licensed by SFA and ensure food handlers are trained and registered before they are allowed to prepare food and drinks for sale.
For safety reasons, it is easier to monitor food prepared by a central kitchen, Prof Chen noted.
“However, food needs to be properly distributed to the schools to ensure safety,” he said. This includes refrigerating food during transportation and storage to minimise microbial growth, and proper hygiene observed by operators as well as consumers.
Fines and other stiffer penalties should also be imposed if an outbreak is attributable to a certain facility, said Dr Yip.
Prof Chen said consumers, school staff and students should also be educated on food safety matters such as personal hygiene, including the proper washing of hands, and not leaving cooked food out in the open for too long.
