Foodborne Outbreaks Research Articles

Multinational investigation of a Salmonella Umbilo outbreak reveals rocket salad and baby spinach as the likely infection vehicles, Europe, 2024.

A food-borne outbreak with about 200 Salmonella Umbilo cases occurred mainly between July and September 2024 in several European countries. Collaborative work between outbreak teams in Germany, Austria and Denmark, including epidemiological and microbiological investigations, allowed to rapidly identify rocket salad as the likely infection vehicle. Salmonella Umbilo was detected in rocket salad, and later in baby spinach. The food isolates and clinical outbreak strain were genetically closely related. Both food items originated from the same company in Italy.

Food and Waterborne Cryptosporidiosis from a One Health Perspective: A Comprehensive Review

A sharp rise in the global population and improved lifestyles has led to questions about the quality of both food and water. Among protozoan parasites, Cryptosporidium is of great importance in this regard. Hence, Cryptosporidium’s associated risk factors, its unique characteristics compared to other protozoan parasites, its zoonotic transmission, and associated economic losses in the public health and livestock sectors need to be focused on from a One Health perspective, including collaboration by experts from all three sectors. Cryptosporidium, being the fifth largest food threat, and the second largest cause of mortality in children under five years of age, is of great significance. The contamination of vegetables, fresh fruits, juices, unpasteurized raw milk, uncooked meat, and fish by Cryptosporidium oocysts occurs through infected food handlers, sewage-based contamination, agricultural effluents, infected animal manure being used as biofertilizer, etc., leading to severe foodborne outbreaks. The only Food and Drug Administration (FDA)-approved drug, Nitazoxanide (NTZ), provides inconsistent results in all groups of patients, and currently, there is no vaccine against it. The prime concerns of this review are to provide a deep insight into the Cryptosporidium’s global burden, associated water- and foodborne outbreaks, and some future perspectives in an attempt to effectively manage this protozoal disease. A thorough literature search was performed to organize the most relevant, latest, and quantified data, justifying the title. The estimation of its true burden, strategies to break the transmission pathways and life cycle of Cryptosporidium, and the search for vaccine targets through genome editing technology represent some future research perspectives.

Comparative genomic analysis provides new insights into non-typhoidal Salmonella population structure in Peru

Non-typhoidal Salmonella (NTS) is one of the leading causes of foodborne outbreaks worldwide, especially in low- and middle-income countries such as Peru. To understand the dynamics of NTS serotypes circulating in the country, the whole genomes of 1122 NTS strains from 1998 to 2018 were analyzed using phylogenomic and comparative genomics tools. A total of 40 different Sequences Type (STs) were identified, the five most frequent being ST-32 (S. Infantis, 37.25%), ST-11 (S. Enteritidis, 23.8%), ST-19 (S. Typhimurium, 14.17%), ST-31 (S. Newport, 6.77%), and ST-413 (S. Mbandaka, 4.72%). Furthermore, the maximum likelihood phylogeny showed high clonality between strains from the same ST recovered from different isolation sources, as well as a variable recombination rate, when comparing each ST individually. Moreover, several virulence factors involved in adherence and invasion, as well as plasmids and prophages, are strongly associated with the most frequent STs, while multidrug resistance markers are mostly linked to ST-32. This work provides an overview of the main genomic characteristics linked to the high-frequency ST, which have undergone few genetic modifications over time, suggesting a high adaptation of these NTS circulating clones in Peru.

Single Laboratory Evaluation of the Q20+ Nanopore Sequencing Kit for Bacterial Outbreak Investigations

Leafy greens are a significant source of produce-related Shiga toxin-producing Escherichia coli (STEC) outbreaks in the United States, with agricultural water often implicated as a potential source. Current FDA outbreak detection protocols are time-consuming and rely on sequencing methods performed in costly equipment. This study evaluated the potential of Oxford Nanopore Technologies (ONT) with Q20+ chemistry as a cost-effective, rapid, and accurate method for identifying and clustering foodborne pathogens. The study focuses on assessing whether ONT Q20+ technology could facilitate near real-time pathogen identification, including SNP differences, serotypes, and antimicrobial resistance genes. This pilot study evaluated different combinations of two DNA extraction methods (Maxwell RSC Cultured Cell DNA kit and Monarch high molecular weight extraction kits) and two ONT library preparation protocols (ligation and the rapid barcoding sequencing kit) using five well-characterized strains representing diverse foodborne pathogens. High-quality, closed bacterial genomes were obtained from all combinations of extraction and sequencing kits. However, variations in assembly length and genome completeness were observed, indicating the need for further optimization. In silico analyses demonstrated that Q20+ nanopore sequencing chemistry accurately identified species, genotype, and virulence factors, with comparable results to Illumina sequencing. Phylogenomic clustering showed that ONT assemblies clustered with reference genomes, though some indels and SNP differences were observed, likely due to sequencing and analysis methodologies rather than inherent genetic variation. Additionally, the study evaluated the impact of a change in the sampling rates from 4 kHz (260 bases pair second) to 5 kHz (400 bases pair second), finding no significant difference in sequencing accuracy. This evaluation workflow offers a framework for evaluating novel technologies for use in surveillance and foodborne outbreak investigations. Overall, the evaluation demonstrated the potential of ONT Q20+ nanopore sequencing chemistry to assist in identifying the correct strain during outbreak investigations. However, further research, validation studies, and optimization efforts are needed to address the observed limitations and fully realize the technology’s potential for improving public health outcomes and enabling more efficient responses to foodborne disease threats.

Investigation of an outbreak of hepatitis E virus 4d reveals the importance of good kitchen hygiene

In July–August 2022, an outbreak of hepatitis E was reported following a funeral dinner in a village of Yantai, June 2022. The aim of this study was to characterise the outbreak, search for more cases, and investigate the risk factors to help prevent hepatitis E infection in the future. A 1:2 case-control study was used to investigate the suspected causative food, and HEV antibody testing and genetic tracing were performed on clinical and environmental samples, and HEV antibody of 69 healthy people who did not attend the dinner in the same village were tested. A total of 80 people were exposed to this outbreak and 18 (22.5 %, 18/80) had acute infections, which was much higher than the positivity rate of healthy people of the same age group in the village (2.9 %, 2/69). Multifactorial analysis showed that the infection was significantly associated with the consumption of cucumber in sauce (aOR = 4.44, 95%CI = 1.23–16.06). Further investigation revealed that there was a mixing of pots and pans for washing raw pork products with those for cold meals during dish preparation. A whole genome sequence of HEV was obtained from sera of cases and from an environmental sample from the pork supplier's refrigerator. All sequences were typed as HEV-4d. This foodborne outbreak was most likely caused due to a failure in kitchen hygiene to differentiate between raw and cooked pots and pans during dish preparation, resulting in cross-contamination from defrosted pork to cold dishes. Our findings emphasize the importance of education of food hygiene, especially in remote areas.

Assessing foodborne outbreak risk in Chinese households: A national survey analysis of pork handling practices

ObjectiveThis study aimed to assess the risk of foodborne outbreaks associated with household food handling practices in China and identify the consumer groups that are at higher risk for foodborne outbreaks. MethodsA national survey of household pork handling practices was conducted in China. The risk of foodborne outbreaks stemming from consumers’ improper handling practices was assessed utilizing the Weighted Harmonic Outbreak Prevention Index (WHOPI). The index categorized these practices into three levels of good hygienic practice (GHP): low (WHOPI≤0.35), medium (WHOPI: 0.36–0.70), and high (WHOPI>0.70). Logistic regression analyses were used to identify groups at higher risk for foodborne outbreaks. ResultsA total of 2730 households from seven provinces in mainland China were analyzed. Based on WHOPI, only 0.4 % of households demonstrated a high level of GHP, while 55.4 % showed a low level of GHP. The primary non-conforming stage was separation practices, followed by cooking and purchasing practices. Nearly two-thirds of households (64.8 %) didn’t have a separate cutting board for raw meat, and 44.9 % of them claimed to use the same board to handle ready-to-eats afterward. Logistic regression indicated more attention is required for those living in southern and rural areas, working in non-public institutions, possessing lower levels of education, and being single or widowed. ConclusionThe household food handling practices of Chinese consumers involve serious food safety risk. Education programs and interventions concerning safe handling practices in households are urgently needed.

Multiple antibiotic resistance of Salmonella Infantis in the Peruvian poultry production chain: Detection in birds, the farming environment, and chicken carcasses

Poultry can act as a reservoir of Salmonella enterica serotype Infantis (S. Infantis) of clinical and epidemiological importance because it triggers foodborne disease outbreaks and presents antibiotic multiresistance. The present study aimed to determine antimicrobial resistance in S. Infantis isolates from poultry livers, litter and chicken carcasses from Lima, Peru, during 2022–2023. S. Infantis was isolated from 10.1 % (27/267), 4.7 % (4/86), and 8 % (2/25) of the bird, litter and carcass samples, respectively. All isolates showed resistance to nalidixic acid (NA). In addition, 94 %, 76 %, 70 %, 48 %, and 45 % of the isolates showed resistance to tetracycline (TET), amoxicillin (AMX), chloramphenicol (C), gentamicin (GEN) and trimethoprim/sulfamethoxazole (TS), respectively. All isolates showed susceptibility to imipinem and amoxicillin/clavulanic acid. Of the isolates, 93.9 % displayed multidrug resistance. The most frequent resistance pattern was C-AMX-NA-GEN-TET (24.2 %, n=8), determined even from carcass isolates, followed by C-AMX-NA-TET (18.2 %, n=6), and C-AMX-NA-GEN-TS-TET (12.1 %, n=4). The presence of these multidrug-resistant S. Infantis isolates is a threat to food safety and public health.

Fresh produce-associated foodborne disease outbreaks in Australia, 2001 to 2017.

Fresh produce is an important source of foodborne outbreaks in Australia. Using descriptive analysis, we examined confirmed and suspected foodborne outbreaks associated with fresh produce in Australia recorded in the OzFoodNet outbreak register from 2001 to 2017. The outbreak register contains reports of foodborne disease outbreaks collected by OzFoodNet epidemiologists and public health officials. A fresh produce outbreak was defined as the occurrence of two or more cases of the same illness in which the investigation had implicated a common food and this food contained fresh produce. A total of 92 fresh produce outbreaks were reported, encompassing 3,422 reported illnesses, 446 hospitalisations and four deaths. Of these outbreaks, 76.1% (70/92) were caused by a known pathogen, with the majority caused by either Salmonella enterica (n = 30) or Norovirus (n = 29). Most outbreaks (77.2%; 71/92) were associated with consumption of foods containing multiple ingredients, some of which were not fresh produce. The largest outbreaks associated with a single fresh produce item included bean sprouts contaminated with S. enterica serovar Saintpaul (419 illnesses and 76 hospitalisations) and semi-dried tomatoes contaminated with Hepatitis A (372 illnesses and 169 hospitalisations). Restaurants (45.7%; n = 42/92) and commercial catering (15.2%: n = 14/92) were common settings for fresh produce outbreaks. Outbreaks occurred in all states and territories of Australia and in all seasons, with an increased frequency in the warmer months (September-May). Although the number of fresh produce-associated outbreaks did not seem to be increasing in Australia, integrated surveillance is needed to rapidly identify sources of infection due to the propensity of these outbreaks to be large and widespread.

Evaluating Chlorine Sanitization at Practical Concentrations for Controlling Listeria monocytogenes and Salmonella on Fresh Peaches.

Recent foodborne outbreaks and recalls involving Listeria monocytogenes and Salmonella-contaminated peaches have caused significant economic losses to the peach industry. This study evaluated the effectiveness of chlorine, a commonly used sanitizer in the fresh produce industry, against L. monocytogenes and Salmonella and its ability to control cross-contamination in fresh peaches. Peaches inoculated with L. monocytogenes or Salmonella (~6 log10 CFU/peach) were treated with 50-150 mg/L of free chlorine (FC, pH6.8) 24 h post-inoculation. The results revealed that chlorine had similar efficacy against L. monocytogenes and Salmonella on peaches (p > 0.05). A 30 s treatment at 50, 100, and 150 mg/L FC resulted in dose-dependent reductions (p < 0.05), achieving reductions of 0.88-0.92, 1.54-1.61, and 1.73-1.79 log10 CFU/peach, respectively. Extending the contact time to 2 min slightly but significantly enhanced the chlorine efficacy (p < 0.05). Additionally, a 30 s to 2 min exposure to chlorine with 50-150 mg/L FC resulted in a 1.05-1.43 log10 CFU/peach reduction in yeasts and molds. Tap water exposure led to substantial cross-contamination between inoculated and uninoculated fruits and processed water, with Salmonella exhibiting higher transfer rates than L. monocytogenes. The application of chlorine mitigated the cross-contamination of both pathogens but did not entirely prevent it. These findings offer valuable insights for the peach and other stone fruit industries to verify process controls.

Impact of Various Washing Protocols on the Mitigation of Escherichia coli Contamination in Raw Salad Vegetables.

Vegetables are an essential component of a balanced diet. The consumption of ready-to-eat foods may lead to the risk of infections and illnesses due to microbial contamination. To mitigate the potential of microbial contamination risks, it is critical to promote safe handling practices among consumers. In this study, our research evaluated the efficacy of different vegetable washing methods, specifically with lettuce, tomato, and cucumber, to establish optimal practices for reducing microbial contamination. This study consisted of two phases. Initially, a survey was distributed to 150 volunteers using snowball sampling to assess everyday vegetable handling and washing methods. The survey's results identified four predominant methods: washing with a 5% vinegar solution for 3 min followed by tap water rinse (37.3% of participants), rinsing with tap water for 1 min (29.3%), washing with a 5% salt solution (vegetable soap) for 3 min followed by a tap water rinse (16.6%), and a 3 min tap water rinse (14%). A minor segment (3.33%) reported not washing their vegetables at all. The survey's findings guided the second phase, which tested the aforementioned washing protocols' effectiveness in reducing Escherichia coli (E. coli) levels on spiked contaminated salad vegetables. The tested vegetables were sterilized using UV light, inoculated with 0.5 McFarland E. coli, and then washed using the four identified methods. After that, E. coli enumeration after washing was performed using 3M™ Petrifilm and the comparison was analyzed via one-way ANOVA. During this study, it was revealed that the cucumbers had the highest E. coli contamination levels in comparison to the lettuce and tomato after washing. Interestingly, by comparing the three washing methods, it was found that washing the vegetables with vinegar proved to be the most effective solution for reducing microbial presence on both lettuce and cucumbers. Notably, the natural smoothness of tomato skin led to no significant differences in contamination levels across washing methods. In summary, vinegar washing effectively reduces microbial contamination from salad vegetables, highlighting the need for informed consumer practices to prevent foodborne outbreaks. This study emphasizes the importance of monitoring contamination sources and using safe washing techniques.

Seasonal Variability of Human Enteric Viruses Discovered in Food Production Mussels (Mytilus galloprovincialis) Farmed in the Central Adriatic Sea (Italy).

Among the different naked and quasi-enveloped viruses, the hepatitis A virus (HAV), hepatitis E virus (HEV), and norovirus genogroups I and II (NoV GI and NoV GII) are considered the main microbiological noxae involved in foodborne outbreaks. Mussels can harbor pathogens in their tissues. In addition to epidemiological attention, marine water temperature changes are considered a crucial variable influencing viral loads. This study aimed to biomolecularly screen 1775 farmed mussels (Mytilus galloprovincialis) for viral ribonucleic acid (RNA) sequence detection (belonging to the HAV, HEV, and NoV GI and GII genogroups) in three different sampling periods (spring, summer, and winter), with the mussels collected from three farms located in the Central Adriatic Sea (Italy). The results showed that 10.42% of the screened animals harbored at least one type of pathogen RNA, more specifically, 5.35% HEV, 4.51% NoV GI, and 0.56% HAV. The highest genetic equivalent (GE) amounts were majorly observed in the winter season (NoV GI 1.0 × 103 GE/g and HEV 1.0 × 102 GE/g), resulting in statistical differences when compared to summer and spring (p-value: <0.001). The original data obtained serve to bring scientific attention to the possible influence of environmental and climatic aspects on viral loads, highlighting the crucial role played by biomolecular assays as preventive medicine tools.

Biopreservation strategies using bacteriocins to control meat spoilage and foodborne outbreaks

Biopreservation strategies using bacteriocins to control meat spoilage and foodborne outbreaks

Investigation of probable Salmonella outbreak in the National Cancer Institute, Sri Lanka

Abstract Background An outbreak is the occurrence of case of disease in excess of what would normally be expected in a defined community. Outbreaks in immune compromised population can lead to devastating morbidity and mortality. Infection prevention and control (IPC) team has a pivotal role in both averting and managing outbreaks in health care settings. There were 7 cases of Salmonella spp, isolated from blood and stools since 12th July 2023 up to 11th August. Assuming of a possible outbreak, IPC team decided to investigate in order to find a possible source for the outbreak. Methods As soon as the outbreak was confirmed, immediate relevant control measures were taken after studying the available information. Working case definitions was constructed with clinical criteria and laboratory criteria with restrictions by time, place and person. Different categories of case definitions were used as the diagnosis was uncertain, such as “confirmed”, “probable” and “possible”. Active surveillance was conducted to collect information on additional case. Data collection tool was prepared with demographic information, clinical information and risk factor information. Then more cases were detected and line listing was created to organize important information for the investigation. Epidemic curve was drawn to see the pattern of spread and it was an irregularly jagged curve which interprets as intermittent common source epidemic. Specific control and prevention measures were implemented. Inquiries were made regarding the dietary intake of the patients over the last seven days and it was difficult to find a common source of food item however, all patients have consumed food prepared in the hospital kitchen. Therefore an audit was conducted in the hospital kitchen to identify probable source. Kitchen staff was educated about the food safety measures and personal hygiene. Kitchen staff was screened for Salmonella carrier state in their stool. Quality of the water from the kitchen and wards was checked for fecal contamination. No residual food was available for microbiological testing. Hypothesis was formulated to gather information after discussion with patients and staff. Findings were communicated to all relevant parties including Director and clinicians in the hospital. Salmonella isolates were sent to the Enteric Reference Laboratory, Medical Research Institute, Colombo for serotype identification. Results It was difficult find a common source. There were some malpractices in the kitchen and those were corrected immediately. Water quality in the hospital was satisfactory. Kitchen staff were not colonized with salmonella. However egg supplier to the kitchen was changed recently and eggs were supplied last minute and the eggs were not washed prior to cooking. Three isolates sent to the reference laboratory were identified as Salmonella Weltevreden, one as Salmonella Enteritidis, while the remaining three isolates could not be identified to serotype level with the available resources. Conclusion The exact contributory factor to the outbreak remained elusive. However, numerous food safety issues which can lead to cross contamination during the preparation of food were identified. Consequently, prompt investigation and control measures are essential to prevent further food borne outbreaks.

Monitoring and preventing foodborne outbreaks: are we missing wastewater as a key data source?

In 2022, the number of foodborne outbreaks in Europe increased by 43.9%, highlighting the need to improve surveillance systems and design outbreak predictive tools. This review aims to assess the scientific literature describing wastewater surveillance to monitor foodborne pathogens in association with clinical data. In the selected studies, the relationship between peaks of pathogen concentration in wastewater and reported clinical cases is described. Moreover, details on analytical methods to detect and quantify pathogens as well as wastewater sampling procedures are discussed. Few papers show a statistically significant correlation between high concentrations of foodborne pathogens in wastewater and the occurrence of clinical cases. However, monitoring pathogen concentration in wastewater looks like a promising and cost-effective strategy to improve foodborne outbreak surveillance. Such a strategy can be articulated in three steps, where the first one is testing wastewater with an untargeted method, like shotgun metagenomic, to detect microorganisms belonging to different domains. The second consists of testing wastewater with a targeted method, such as quantitative polymerase chain reaction, to quantify those specific pathogens that in the metagenomic dataset display an increasing trend or exceed baseline concentration thresholds. The third involves the integrated wastewater and clinical data analysis and modeling to find meaningful epidemiological correlations and make predictions.

Staphylococcus aureus in Dairy Industry: Enterotoxin Production, Biofilm Formation, and Use of Lactic Acid Bacteria for Its Biocontrol.

Staphylococcus aureus is a well-known pathogen capable of producing enterotoxins during bacterial growth in contaminated food, and the ingestion of such preformed toxins is one of the major causes of food poisoning around the world. Nowadays 33 staphylococcal enterotoxins (SEs) and SE-like toxins have been described, but nearly 95% of confirmed foodborne outbreaks are attributed to classical enterotoxins SEA, SEB, SEC, SED, and SEE. The natural habitat of S. aureus includes the skin and mucous membranes of both humans and animals, allowing the contamination of milk, its derivatives, and the processing facilities. S. aureus is well known for the ability to form biofilms in food processing environments, which contributes to its persistence and cross-contamination in food. The biocontrol of S. aureus in foods by lactic acid bacteria (LAB) and their bacteriocins has been studied for many years. Recently, LAB and their metabolites have also been explored for controlling S. aureus biofilms. LAB are used in fermented foods since in ancient times and nowadays characterized strains (or their purified bacteriocin) can be intentionally added to prolong food shelf-life and to control the growth of potentially pathogenic bacteria. Regarding the use of these microorganism and their metabolites (such as organic acids and bacteriocins) to prevent biofilm development or for biofilm removal, it is possible to conclude that a complex network behind the antagonistic activity remains poorly understood at the molecular level. The use of approaches that allow the characterization of these interactions is necessary to enhance our understanding of the mechanisms that govern the inhibitory activity of LAB against S. aureus biofilms in food processing environments.

Simultaneous detection of six major virulent genes of Escherichia coli O157:H7 from seafood by multiplex PCR and its validation through spiked study

Enterohaemorrhagic Escherichia coli (EHEC), mainly the serotype O157:H7 is a global concern in foodborne outbreaks,. The incidence of E. coli O157:H7 in seafood sold in India has been reported as 8.4%. The conventional method for the detection of E. coli O157:H7 from seafood is cumbersome and time consuming making this strain particularly challenging to detect. In this study a multiplex PCR was developed targeting six major virulence factors of the pathogen viz. shigatoxin 1 and 2, attachment and effacement factor, flagellar antigen, hemolysin gene and O157 antigen. The sensitivity of the multiplex PCR developed in the study was found to be 120 pg μl-1 of DNA and that of E. coli 0157:H7 spiked samples was 2 cfu ml-1. The multiplex PCR developed in this study showed 100% specificity in identifying E. coli O157:H7, effectively distinguishing it from non-target bacteria. This highly sensitive and specific multiplex PCR is the first of its kind to detect E. coli O157:H7 in seafood by targeting six major virulence genes. Keywords: E. coli O157:H7, EHEC, Foodborne pathogen, Seafood, Sensitivity, Shigatoxin, Specificity

Accelerated Detection of Foodborne Pathogens and Toxins: Techniques and Applications – A Review

Pathogens associated with food and their corresponding toxins, including mycotoxins, pose a sig¬nificant threat to public health, leading to various health issues worldwide, particularly affecting infants, young children, and the elderly. The rise in foodborne illnesses highlights the crucial importance of food safety in ensuring a reliable food supply and promoting health. Timely detection of foodborne pathogens, toxins, and mycotoxins is essential for reducing the incidence of foodborne diseases. This review aims to provide comprehensive insights into the methodology for rapid detection, detailing the principles, appli¬cations, advantages, and limitations to enhance current knowledge. Conventional culture-based methods for foodborne pathogen identification are selective and are hindered by significant time demands, labor intensity, challenges from complex sample preparation, delayed results, and the need for specialized per¬sonnel. In contrast, the new emerging detection techniques such as immunological, nucleic acid-based, and biosensor-based methods offer time efficiency, reduced labor, improved accuracy, sensitivity, specificity, and reliability, and are user-friendly. Recently, numerous novel techniques have been developed for the rapid identification of foodborne pathogens, toxins, and mycotoxins, transforming food safety practices. Providing rapid and accurate results is crucial for controlling and managing foodborne disease outbreaks while ensuring food safety. As the global food supply chain becomes more complex, advancing rapid and automated detection methods remains essential for safeguarding food safety and quality, as well as enhanc¬ing public health.

Foodborne Outbreak Investigation in Elementary School Students in Bantul, Yogyakarta, 2023

Bantul District Health Office received notification that 75 students in elementary school were sick with symptoms of nausea, vomiting, and dizziness after they consumed snacks from the school canteen. An epidemiological investigation was conducted to confirm the outbreak, identify additional cases, determine risk factors and causes, and recommend preventive measures. This investigation conducted active case finding followed by a retrospective cohort study. Individuals who experience one or more symptoms, such as nausea, vomiting, diarrhea, stomach pain, dizziness, fever, and malaise after consuming snacks were defined as cases. Data was collected through direct interviews with students, teachers, staff, and food sellers. Samples of food and vomit were collected and sent to the health laboratory. Data were analyzed using chi-square and multiple binomial regression. There were 150 cases. Most cases were found in the female group (53.22%), 9-year-old group (55.32%), and third-grade students (65%). Dizziness (66.67%), vomiting (56.67%), and nausea (46%) were the most common symptoms. The epidemic curve was a common source, with incubation periods ranging from one to 26 hours. Meatballs were associated with the increased risk of becoming a case in this outbreak (aRR = 1.49; 95% CI = 1.22-1.81). The causative agent was suspected to be Salmonella spp, but the laboratory analysis results were inconclusive due to contamination. Potential risk factors were large storage in the refrigerator, insufficient reheating, and cross-contamination. Improvements in food safety monitoring for schools and food handlers, along with appropriate sampling by healthcare facilities, are required to control outbreaks.

Biofilm Formation among Staphylococcus aureus Strains from Food Contact Surfaces in Households: A Public Health Concern

Staphylococcus aureus is a foodborne pathogen of serious public health concern due to its high biofilm formation capability. One of the contributing factors to foodborne illnesses is improper cleaning and sanitization of food contact surfaces This study aimed to determine the prevalence of S. aureus with biofilm formation potential (BFP) from various food contact surfaces. A total of 100 samples were obtained, 20 from each of stainless steel spoons, plastic plates, plastic eating bowls, plastic cutting boards and glass cups. Samples were obtained by surface swabbing. The cotton swabs were streaked onto nutrient agar plates and incubated overnight. Colonies obtained were subjected to Gram staining, coagulase, catalase and DNAse tests for the identification of S. aureus. The identified S. aureus strains were subjected to biofilm formation potential assay using crystal violet assay (CV-assay) in polystyrene 96-well microtitre plates. Out of the 100 samples obtained, 26 were found to harbour S. aureus. Moreover, out of the 20 isolates, 2 (10%) were from stainless steel spoons, 8 (40%) from plastic plates, 5 (25%) from plastic-eating bowls, 10 (50%) from plastic cutting boards and 1 (5%) from glass cups. Additionally, 11 (42%) of the strains had strong BFP, 11 (42%) had moderate BFP, 3 (12%) and 1 (4%) had no BFP. Presence of S. aureus with BFP on food contact surfaces should be checked to avoid foodborne outbreaks due to this organism.

A foodborne outbreak caused by staphylococcal enterotoxins in cheese sandwiches in northern Italy

Staphylococcus aureus can produce numerous toxins, including staphylococcal enterotoxins, namely, SEs, SEA to SEE, SEG to SEI, and SER to SET. They have demonstrated emetic activity and can cause food poisoning outbreaks (FBOs). Here, we report a multidisciplinary investigation conducted by authorities competent in food safety in collaboration with veterinary and health and hygiene services. The issue was foodborne intoxication which involved eight members (aged 12–74 years) of the same family. Notification reported that time to symptom onset was about 3 hours after lunch, which suggests that the food contained preformed toxins. Ham and cheese used for the preparation of sandwiches consumed by all symptomatic relatives were suspected to be the source of FBO. The day after symptoms appeared, samples were collected at the restaurant and delivered to the food safety laboratory. All analyses performed on official food samples are validated according to ISO 17025:2017 and accredited. The cheese subsamples were all positive for coagulase-positive staphylococci CPS (range: 1.1*103 CFU/g to 8.1*103 CFU/g). The pooled sample tested positive for staphylococcal enterotoxin D (SED) at 0.649 ng/g. This concentration can cause symptoms of FBO. Following the notification of suspected food poisoning, a rapid response by the district food safety agency is necessary. In the case described here, the multidisciplinary collaboration facilitated the collection of samples at the food business plant aimed at identifying a suspected source of intoxication and to withdraw unsafe food from the market.