A Shiga toxin-producing Escherichia coli O157 outbreak associated with consumption of rice cakes in 2011 in Japan

Validation of process technologies for enhancing the safety of low-moisture foods: A review

The outbreaks linked to foodborne illnesses in low-moisture foods are frequently reported due to the occurrence of pathogenic microorganisms such as Salmonella Spp. Bacillus cereus, Clostridium spp., Cronobacter sakazakii, Escherichia coli, and Staphylococcus aureus. The ability of the pathogens to withstand the dry conditions and to develop resistance to heat is regarded as the major concern for the food industry dealing with low-moisture foods. In this regard, the present review is aimed to discuss the importance and the use of novel thermal and nonthermal technologies such as radiofrequency, steam pasteurization, plasma, and gaseous technologies for decontamination of foodborne pathogens in low-moisture foods and their microbial inactivation mechanisms. The review also summarizes the various sources of contamination and the factors influencing the survival and thermal resistance of pathogenic microorganisms in low-moisture foods. The literature survey indicated that the nonthermal techniques such as CO₂ , high-pressure processing, and so on, may not offer effective microbial inactivation in low-moisture foods due to their insufficient moisture content. On the other hand, gases can penetrate deep inside the commodities and pores due to their higher diffusion properties and are regarded to have an advantage over thermal and other nonthermal processes. Further research is required to evaluate newer intervention strategies and combination treatments to enhance the microbial inactivation in low-moisture foods without significantly altering their organoleptic and nutritional quality.

Application of a Rapid Knowledge Synthesis and Transfer Approach To Assess the Microbial Safety of Low-Moisture Foods

Low-moisture foods (LMF) are increasingly implicated in outbreaks of foodborne illness, resulting in a significant public health burden. To inform the development of a new Codex Alimentarius code of hygienic practice for LMF, we applied a rapid knowledge synthesis and transfer approach to review global research on the burden of illness, prevalence, and interventions to control nine selected microbial hazards in eight categories of LMF. Knowledge synthesis methods included an integrated scoping review (search strategy, relevance screening and confirmation, and evidence mapping), systematic review (detailed data extraction), and meta-analysis of prevalence data. Knowledge transfer of the results was achieved through multiple reporting formats, including evidence summary cards. We identified 214 unique outbreaks and 204 prevalence and 126 intervention studies. Cereals and grains (n = 142) and Salmonella (n = 278) were the most commonly investigated LMF and microbial hazard categories, respectively. Salmonella was implicated in the most outbreaks (n = 96, 45%), several of which were large and widespread, resulting in the most hospitalizations (n = 895, 89%) and deaths (n = 14, 74%). Salmonella had a consistently low prevalence across all LMF categories (0 to 3%), but the prevalence of other hazards (e.g., Bacillus cereus) was highly variable. A variety of interventions were investigated in small challenge trials. Key knowledge gaps included underreporting of LMF outbreaks, limited reporting of microbial levels in prevalence studies, and a lack of intervention efficacy research under commercial conditions. Summary cards were a useful knowledge transfer format to inform complementary risk ranking activities. This review builds upon previous work in this area by synthesizing a broad range of evidence using a structured, transparent, and integrated approach to provide timely evidence informed inputs into international guidelines.

Sensitive detection of Escherichia coli O157:H7 using Pt-Au bimetal nanoparticles with peroxidase-like amplification

Escherichia coli O157:H7 is one of the most notorious foodborne pathogens causing serious disease at low infectious dose. To protect consumers from deadly foodborne E. coli O157:H7 infection, it is vital to develop a simple, reliable, sensitive and rapid method which can detect low level E. coli O157:H7 in foods at real-time. We have successfully developed a novel immunochromatographic assay (ICA) with enhanced sensitivity for the visual and quantitative detection of E. coli O157:H7. Sandwich-type immunoreactions were performed on the ICA, and Pt-Au bimetal nanoparticles (NPs) were accumulated on the test zone. The signal amplification is based on Pt-Au bimetal NPs possessing high peroxidase activity toward 3,3',5,5'-tetramethylbenzidine, which can produce characteristic colored bands and thus, enable visual detection of E. coli O157:H7 without instrumentation. The innovative aspect of this approach lies in the visualization and quantification of target pathogen through the detection of color intensity. Due to the excellent peroxidase activity of Pt-Au NPs, they emit strong visible color intensity in less than 1 min for visual observation even in low concentration range of E. coli O157:H7. Quantification was performed using a commercial assay meter. The sensitivity was improved more than 1000-folds compared to the conventional test strip based on colored gold-colloids. Although the feasibility was demonstrated using E. coli O157:H7 as a model analyte, this approach could be easily developed to be a universal signal amplification technique and applied to detection of a wide variety of foodborne pathogens and protein biomarkers.

Surveillance of Bacterial Pathogens of Diarrhoea in Two Selected Sub Metros Within the Accra Metropolis

BACKGROUND

In recent years, many localities within the Greater Accra Region (GAR) have witnessed several episodes of cholera outbreaks, with some deaths. Compared to previous epidemics, which usually followed heavy rains, recent outbreaks show no seasonality.

OBJECTIVES

To investigate infective bacterial diseases in selected sub metros within the GAR.

METHODS

We used existing disease surveillance systems in Ghana, and investigated all reported cases of diarrhoea that met our case-definition. A three-day training workshop was done prior to the start of study, to sensitize prescribers at the Korle-Bu Polyclinic and Maamobi General hospital. A case-based investigation form was completed per patient, and two rectal swabs were taken for culture at the National Public Health and Reference Laboratory. Serotyping and antibiogram profiles of identified bacteria were determined. Potential risk factors were also assessed using a questionnaire.

RESULTS

Between January and June 2012, a total of 361 diarrhoeal cases with 5 deaths were recorded. Out of a total of 218 rectal swabs cultured, 71 (32.6%) Vibrio cholerae O1 Ogawa serotypes, and 1 (0.5%) Salmonella (O group B) were laboratory confirmed. No Shigella was isolated. The Vibrio cholerae isolates were susceptible to ciprofloxacin and tetracycline. Greater than 80% of patients reported having drank sachet water 24 h prior to diarrhoea onset, and many (144/361) young adults (20-29 years) reported with diarrhoea.

CONCLUSION

Enhanced surveillance of diarrhoeal diseases (enteric pathogens) within cholera endemic regions, will serve as an early warning signal, and reduce fatalities associated with infective diarrhoea.

Control selection methods in recent case-control studies conducted as part of infectious disease outbreaks

Successful investigation of national outbreaks of communicable disease relies on rapid identification of the source. Case-control methodologies are commonly used to achieve this. We assessed control selection methods used in recently published case-control studies for methodological and resource issues to determine if a standard approach could be identified. Neighbourhood controls were the most frequently used method in 53 studies of a range of different sizes, infections and settings. The most commonly used method of data collection was face to face interview. Control selection issues were identified in four areas: method of identification of controls, appropriateness of controls, ease of recruitment of controls, and resource requirements. Potential biases arising from the method of control selection were identified in half of the studies assessed. There is a need to develop new ways of selecting controls in a rapid, random and representative manner to improve the accuracy and timeliness of epidemiological investigations and maximise the effectiveness of public health interventions. Innovative methods such as prior recruitment of controls could improve timeliness and representativeness of control selection.

Polynucleotide phosphorylase is required for Escherichia coli O157:H7 growth above refrigerated temperature

BACKGROUND

The growth of Escherichia coli O157:H7 in contaminated dairy and other refrigerated food products due to temperature fluctuation poses a major food safety threat. Effective control or inhibition of E. coli O157:H7 growth depends on our understanding of mechanisms that regulate its growth at low temperature. We hypothesized that polynucleotide phosphorylase (PNPase) plays a critical role in E. coli O157:H7 low-temperature growth.

METHODS

To test this hypothesis, the pnp deletion mutant of E. coli O157:H7 was generated using the λ Red recombinase system, and the growth and survival of wild-type and pnp deletion mutant strains were compared at low temperatures.

RESULTS

The growth of pnp deletion mutant strains in Luria Broth (LB) and agar plate at 37°C was similar to their corresponding wild-type strains, while the deletion of pnp impaired E. coli O157:H7 growth in LB at 10°C and 22°C; growth impairment could be partially recovered in the mutant strains by ectopic expression of the pnp complementation plasmid, demonstrating that growth impairment was PNPase-specific. During 14 days of 10°C storage in both LB and milk, wild type strain EDL933 grew and reached >8 log10 colony-forming units per milliliter after 4 days of 10°C storage, while EDL933Δpnp gradually died off with effects more pronounced in milk, which were again mitigated by pnp overexpression. In addition, pnp deletion impaired the motility of E. coli O157:H7 but did not affect its susceptibility to H2O2.

CONCLUSION

PNPase is required for the growth of E. coli O157:H7 at low temperature; PNPase thus provides a molecular target to control the growth of E. coli O157:H7, which may have important practical applications in dairy and other food industry.