Leveraging risk assessment for foodborne outbreak investigations: The Quantitative Risk Assessment-Epidemic Curve Prediction Model.

Root cause analysis can be used in foodborne illness outbreak investigations to determine the underlying causes of an outbreak and to help identify actions that could be taken to prevent future outbreaks. We developed a new tool, the Quantitative Risk Assessment-Epidemic Curve Prediction Model (QRA-EC), to assist with these goals and applied it to a case study to investigate and illustrate the utility of leveraging quantitative risk assessment to provide unique insights for foodborne illness outbreak root cause analysis. We used a 2019 Salmonella outbreak linked to melons as a case study to demonstrate the utility of this model (Centers for Disease Control and Prevention [CDC], 2019). The model was used to evaluate the impact of various root cause hypotheses (representing different contamination sources and food safety system failures in the melon supply chain) on the predicted number and timeline of illnesses. The predicted number of illnesses varied by contamination source and was strongly impacted by the prevalence and level of Salmonella contamination on the surface/inside of whole melons and inside contamination niches on equipment surfaces. The timeline of illnesses was most strongly impacted by equipment sanitation efficacy for contamination niches. Evaluations of a wide range of scenarios representing various potential root causes enabled us to identify which hypotheses, were likely to result in an outbreak of similar size and illness timeline to the 2019 Salmonella melon outbreak. The QRA-EC framework can be adapted to accommodate any food-pathogen pairs to provide insights for foodborne outbreak investigations.

Evaluation of Methods of Enrichment and Compositing of Environmental Samples for Detection of Listeria monocytogenes.

ABSTRACT: Various methods exist for the enrichment and detection of Listeria spp. and Listeria monocytogenes from environmental samples. Procedures for the compositing of environmental samples are not as well defined. In this study, different enrichment procedures involving buffered Listeria enrichment broth (BLEB), University of Vermont medium (UVM), and Fraser broth (FB) were evaluated to determine the limits of detection (LODs) for L. monocytogenes from culture and from swabs of stainless steel and to assess the efficacy of composite sampling by wet (pooling of primary enrichments) and dry (pooling of swabs) procedures. For detection of cells in pure culture, the computed values for the LOD at 95% probability (LOD95) using a single-step BLEB or two-step UVM-FB enrichment were 0.33 and 0.49 CFU/225 mL enrichment, respectively. No significant differences in detection were observed for procedures using either two-step BLEB-FB or UVM-FB enrichments for swabs of stainless steel when L. monocytogenes was inoculated at 2 to 6 log CFU; the LOD95 values were 3.82 and 3.62 log CFU per 4-in2 area, respectively. Wet compositing of L. monocytogenes from culture with and without romaine lettuce wash resident microbiota was conducted using BLEB-FB and UVM-FB enrichment methods; both allowed detection of the pathogen at ratios of 1:1, 1:2, 1:4, and 1:7 (1 positive sample to x negative samples) with no loss in sensitivity. From swabs of stainless steel, L. monocytogenes was detected similarly for both wet and dry composites of up to eight samples (1:7) with romaine lettuce wash. However, the BLEB-FB method allowed significantly faster detection (after 24 h of FB incubation) in composites of 1:4 and 1:7 samples compared with the UVM-FB method under the conditions tested. The results of this study provide data to evaluate the efficacies of the different enrichment procedures and aid in assessing the use of wet and dry compositing of environmental samples for use as part of a Listeria control plan in food production and processing facilities.

Predictors of multivisceral resection in patients with locally advanced colorectal cancer.

BACKGROUND: Practice guidelines recommend en bloc multivisceral resection (MVR) for all involved organs in patients with locally advanced adherent colorectal cancer (LAACRC) to reduce local recurrence and improve survival. We found that MVR was performed in one-third of eligible American patients in the Surveillance, Epidemiology and End Results cancer registry but that study could not identify factors amenable to quality improvement. This study was conducted to examine rates, and predictors of MVR among Canadian patients with LAACRC. METHODS: Rates of MVR were examined by observational study. Eligible patients were aged 20-74 years who had surgery for nonmetastatic LAACRC from July 1997 to December 2000. Patient, tumor, surgeon, and hospital characteristics were extracted from medical records. Summary statistics were compared by type of surgery (MVR, partial MVR, standard resection). To identify factors associated with MVR we analyzed operative notes and transcripts from interviews with general surgeons using standard qualitative methods. RESULTS: Factors associated with MVR included fewer years in practice, preoperative treatment planning, involvement of surgical consultants, and access to diagnostic imaging and systems to enable preoperative multidisciplinary planning. Judgments regarding the nature of peritumoral adhesions, resectability, and personal technical skill may mediate decision-making. Many surgeons would prefer to refer patients than undertake complicated, lengthy cases. CONCLUSION: Further research is required to validate these findings in larger studies and among patients undergoing surgery for conditions other than LAACRC, and evaluate strategies to improve rates of MVR through enhanced individual awareness and system capacity.