Measuring transfer of human norovirus during sandwich production: Simulating the role of food, food handlers and the environment

Detection of Foodborne Pathogens in Contaminated Food Using Nanomaterial-Based Electrochemical Biosensors

Foodborne pathogens are a grave concern for the for food, medical, environmental, and economic sectors. Their ease of transmission and resistance to treatments, such as antimicrobial agents, make them an important challenge. Food tainted with these pathogens is swiftly rejected, and if ingested, can result in severe illnesses and even fatalities. This review provides and overview of the current status of various pathogens and their metabolites transmitted through food. Despite a plethora of studies on treatments to eradicate and inhibit these pathogens, their indiscriminate use can compromise the sensory properties of food and lead to contamination. Therefore, the study of detection methods such as electrochemical biosensors has been proposed, which are devices with advantages such as simplicity, fast response, and sensitivity. However, these biosensors may also present some limitations. In this regard, it has been reported that nanomaterials with high conductivity, surface-to-volume ratio, and robustness have been observed to improve the detection of foodborne pathogens or their metabolites. Therefore, in this work, we analyze the detection of pathogens transmitted through food and their metabolites using electrochemical biosensors based on nanomaterials.

Burden and factors influencing intestinal parasitic infections among food handlers in Gondar City, Northwest Ethiopia

Background

Intestinal parasitic infections pose significant global health challenges, particularly in developing countries. Asymptomatic infections often present a considerable burden with food handlers serving as potential carriers. In Ethiopia, the prevalence of these parasites varies across regions, and accurate data in the study area is lacking. Therefore, this study aimed to investigate the prevalence of intestinal parasites among food handlers working in hotels and restaurants in Gondar City, Northwest Ethiopia.

Methods

A cross-sectional study collected stool samples from food handlers alongside a structured questionnaire gathering socio-demographic and hygiene practice information. Stool specimens were screened for intestinal parasites using direct wet mount and formol-ether concentration techniques. The collected data were checked for completeness, entered into EpiData software version 3.1, and exported to SPSS version 20 for analysis. A multivariable logistic regression analysis was deemed statistically significant if the p-value was less than 0.05.

Results

A total of 257 food handlers working in hotels and restaurants in Gondar City participated in the study. Of these, 33.5% (86/257) were found positive for one or more intestinal parasites, with a 95% confidence interval (CI) of 28.0-39.5%. The study identified nine types of intestinal parasites, with E. histolytica/dispar (8.2%, 21/257) and Ascaris lumbricoides (6.6%, 17/257) being the predominant parasites, followed by hookworm (3.5%, 9/257) and S. mansoni (2.3%, 6/257). The prevalence of mixed infections was 9.3% (24/257). A significant association was observed between intestinal parasitic infection and the educational level of food handlers.

Conclusion

In this study, a high prevalence of intestinal parasites was detected indicating poor hygiene practices of the food handlers at the study site. Even the prevalence of mixed infections was high. Regular training, strict adherence to personal hygiene and food-handling practices, and routine inspections and medical checkups for food handlers are crucial.

Quantification and Potential Viability of Human Noroviruses in Final Effluent from Wastewater Treatment Works in Pretoria, South Africa

Growing global concerns over water scarcity, worsened by climate change, drive wastewater reclamation efforts. Inadequately treated wastewater presents significant public health risks. Previous studies in South Africa (SA) have reported high norovirus levels in final effluent and sewage-polluted surface water, indicating pathogen removal inefficiency. However, the viability of these virions was not explored. This study assessed human norovirus viability in final effluent from wastewater treatment works (WWTWs) in Pretoria, SA. Between June 2018 and August 2020, 200 samples were collected from two WWTWs, including raw sewage and final effluent. Norovirus concentrations were determined using in-house RNA standards. Viability of noroviruses in final effluent was assessed using viability RT-qPCR (vPCR) with PMAxx™-Triton X-100. There was no significant difference in GI concentrations between raw sewage (p = 0.5663) and final effluent (p = 0.4035) samples at WWTW1 and WWTW2. WWTW1 had significantly higher GII concentrations in raw sewage (p < 0.001) compared to WWTW2. No clear seasonal pattern was observed in norovirus concentrations. At WWTW1, 50% (7/14) of GI- and 64.9% (24/37) of GII-positive final effluent samples had no quantifiable RNA after vPCR. At WWTW2, the majority (92.6%, 25/27) of GII-positive final effluent samples showed a 100% RNA reduction post vPCR. PMAxx™-Triton X-100 vPCR provides a more accurate reflection of discharge of potentially viable noroviruses in the environment than standard RT-qPCR. Despite significant reductions in potentially viable noroviruses after wastewater treatment, the levels of potentially viable viruses in final effluent are still of concern due to the high initial load and low infectious dose of noroviruses.

Norovirus GII.17 Caused Five Outbreaks Linked to Frozen Domestic Bilberries in Finland, 2019

In March 2019, the Finnish Institute for Health and Welfare and Finnish Food Authority started an outbreak investigation after a notification of food business operators' recall of frozen bilberries due to a norovirus finding. A retrospective search was conducted in the food and waterborne outbreak notification system to identify the notifications linked to norovirus and consumption of bilberries in January-March 2019. Five outbreaks were found in which norovirus GII or GII.17 had been detected in patient samples. A pooled retrospective cohort study was performed for those four in which a questionnaire study had been done. A case was defined as a person with diarrhoea or vomiting within 2 days after consuming a meal studied at one of the outbreak locations. Of 79 participants, 45 (57%) cases were identified. Persons that had consumed foods containing unheated bilberries were three times more likely to get ill than those who had not consumed them (RR 3.1, CI 95% 1.2-8.1, p = 0.02). Norovirus GII.17 was found in 16/17 patient samples sent for further typing. Identical norovirus GII.17 was detected in frozen Finnish bilberries and patient samples. At the berry packaging premises, signs of norovirus GII contamination were found in packaging lines. A new procedure for extracting viral nucleic acid from food and environmental samples was used during the outbreak investigation. Consumption of industrially packed frozen berries as heated would be one of the means to prevent norovirus infections.

Ozone and photodynamic inactivation of norovirus surrogate bacteriophage MS2 in fresh Brazilian berries and surfaces

This study assessed the efficacy of ozone (bubble diffusion in water; 6.25 ppm) and photodynamic inactivation (PDT) using curcumin (75 μM) as photosensitizer (LED emission 430-470 nm; 33.6 mW/cm2 irradiance; 16.1, 20.2, and 24.2 J/cm2 light dose) against the Norovirus surrogate bacteriophage MS2 in Brazilian berries (black mulberry and pitanga) and surfaces (glass and stainless steel). Contaminated berries and surfaces were immersed in ozonized water or exposed to PDT-curcumin for different time intervals. Transmission electron microscopy was used to assess the effects of the treatments on MS2 viral particles. The MS2 inactivation by ozone and PDT-curcumin varied with the fruit and the surface tested. Ozone reduced the MS2 titer up to 3.6 log PFU/g in black mulberry and 4.1 log PFU/g in pitanga. On surfaces, the MS2 reduction by ozone reached 3.6 and 4.8 log PFU/cm2 on glass and stainless steel, respectively. PDT-curcumin reduced the MS2 3.2 and 4.8 log PFU/g in black mulberry and pitanga and 2.7 and 3.3 log PFU/cm2 on glass and stainless steel, respectively. MS2 particles were disintegrated by exposure of MS2 to ozone and PDT-curcumin on pitanga. Results can contribute to establishing effective practices for controlling NoV in fruits and surfaces, estimated based on MS2 bacteriophage behavior.

A review of nucleic acid-based detection methods for foodborne viruses: Sample pretreatment and detection techniques

Viruses are major pathogens that cause food poisoning when ingested via contaminated food and water. Therefore, the development of foodborne virus detection technologies that can be applied throughout the food distribution chain is essential for food safety. A common nucleic acid-based detection method is polymerase chain reaction (PCR), which has become the gold standard for monitoring food contamination by viruses due to its high sensitivity, and availability of commercial kits. However, PCR-based methods are labor intensive and time consuming, and are vulnerable to inhibitors that may be present in food samples. In addition, the methods are restricted with regard to site of analysis due to the requirement of expensive and large equipment for sophisticated temperature regulation and signal analysis procedures. To overcome these limitations, optical and electrical readout biosensors based on nucleic acid isothermal amplification technology and nanomaterials have emerged as alternatives for nucleic acid-based detection of foodborne viruses. Biosensors are promising portable detection tools owing to their easy integration into compact platforms and ability to be operated on-site. However, the complexity of food components necessitates the inclusion of tedious preprocessing steps, and the lack of stability studies on residual food components further restricts the practical application of biosensors as a universal detection method. Here, we summarize the latest advances in nucleic acid-based strategies for the detection of foodborne viruses, including PCR-based and isothermal amplification-based methods, gene amplification-free methods, as well as food pretreatment methods. The principles, strengths/disadvantages, and performance of each method, problems to be solved, and future prospects for the development of a universal detection method are discussed.

Norovirus attribution study: Detection of norovirus from the commercial food preparation environment in outbreak and non-outbreak premises

AIMS

Norovirus remains the most significant virological risk that is transmitted via food and the environment to cause acute gastroenteritis. This study aimed to investigate the hypothesis that the contamination of the commercial food production environment with norovirus will be higher in premises that have recently reported a foodborne norovirus outbreak than those that have not.

METHODS

Sampling of commercial food production environments was carried out across a 16-month period between January 2015 and April 2016 in the South East and the North West of England by local authority environmental health departments as part of routine surveillance visits to premises. A total of 2982 samples, 2038 virological and 944 bacteriological, were collected from 256 premises. Sixteen of these premises, six from South East and ten from North West England, were sampled as part of a public health outbreak investigation.

RESULTS & CONCLUSIONS

Overall, 2038 swabs were submitted for norovirus testing, with an average of eight swabs per premises (range 4 to 23) and a median of seven. Of the premises sampled, 11.7% (30/256) yielded at least one norovirus-positive sample (environmental, and/or food handler hand swab), and 2.5% of the swabs were positive for norovirus. A peak in the positivity rate was seen in the South East in April 2016. No associations were found between norovirus positivity and bacteriology indicators, or between bacteriology indicators and hygiene ratings.

SIGNIFICANCE AND IMPACT OF STUDY

This study demonstrates that food premises and food handlers remain a potential source of norovirus transmission and outbreaks.

Prevalence of intestinal parasites and associated factors among food handlers in food establishments in the Lideta subcity of Addis Ababa, Ethiopia: an institution-based, cross-sectional study

OBJECTIVE

This study was conducted to assess the prevalence of intestinal parasites and the associated factors among food handlers in the Lideta subcity of Addis Ababa, Ethiopia.

DESIGN

An institution-based, cross-sectional study design was used. Stool samples were collected from food handlers and examined using direct wet mount and formalin-ether concentration techniques. Personal and establishment-related information was collected using a pretested questionnaire, with a structured observation. Multivariable binary logistic regression was used to identify factors associated with the prevalence of intestinal parasites on the basis of adjusted OR (AOR) and 95% CI and p values <0.05.

SETTING

Food establishments in the Lideta subcity of Addis Ababa, Ethiopia.

PARTICIPANTS

411 food handlers participated in the study.

OUTCOME MEASURES

The primary outcome was the prevalence of intestinal parasites, defined as the presence of one or more intestinal parasitic species in stool samples.

RESULTS

One or more intestinal parasites were detected in 171 (41.6%; 95% CI 36.6% to 46.4%) stool samples. The most common intestinal parasites were Entamoeba histolytica/dispar (12.7%), Giardia duodenalis (11.2%) and Ascaris lumbricoides (8.3%). The presence of intestinal parasites among food handlers was associated with low monthly income (AOR: 2.83, 95% CI 1.50 to 8.84), untrimmed fingernails (AOR: 4.36, 95% CI 1.98 to 11.90), no food safety training (AOR: 2.51, 95% CI 1.20 to 5.58), low level of education (AOR: 3.13, 95% CI 1.34 to 7.44), poor handwashing practice (AOR: 2.16, 95% CI 1.03 to 4.22) and lack of medical check-up (AOR: 2.31, 95% CI 1.18 to 6.95).

CONCLUSION

The prevalence of intestinal parasites among food handlers in food establishments in the Lideta subcity of Addis Ababa was high. The presence of intestinal parasites was linked to socioeconomic conditions, poor hand hygiene conditions and absence of food safety training. It is crucially important to promote handwashing practices and provide food hygiene and safety training in these settings.

A Comparison of Two Methods for Detection of Norovirus RNA in Environmental Swab Samples

Standardised molecular methods are available for the detection of norovirus from water and specific food items. Detection of norovirus from stool samples also relies on molecular methods, but differences exist between nucleic acid extraction, reverse transcription, and amplification strategies recommended by the ISO 15216-1:2017, and those employed in clinical laboratories. Here, we conduct a direct comparison of two methods for the detection and quantitation of norovirus from a stool sample and from artificially contaminated swabs. We also compare use of linear dsDNA standards as recommended in ISO 15216:2017 against an in vitro-transcribed single-stranded RNA (ssRNA) for estimation of norovirus genome copy number. Our results show that the two methods have comparable sensitivity for the detection of norovirus RNA from a clinical sample or swab. The use of a ssRNA standard revealed that quantitation performed against a linear dsDNA standard consistently underestimated the genome copy numbers by 1.5 to 2 log due to the relative inefficiency of the reverse transcription step. This has important implications for the estimation of the sensitivity of norovirus detection methods, comparability of results across sites, and assessment of viral loads that may be clinically significant or estimated to constitute infectious doses.