Resolving postharvest harborage sites of Listeria protects Zone 1 surfaces

Resolving postharvest harborage sites of Listeria protects Zone 1 surfaces

Jan. 1, 2017 - Jun. 30, 2019

2017-151F

$358,132.31

Trevor Suslow, Ph.D.
University of California, Davis

Adrian Sbodio, Janneth Pinzon-Avila

Final Report

Fresh citrus is an important global commodity and a major specialty crop in California. The 2014-15 CA Agricultural Statistics Review places the combined value of oranges, lemons, and tangerines at over $ 2 billion dollars and all three are in the Top 15 Specialty Crops by value. Fresh whole citrus has not experienced an incident of recall, illness, or outbreak and CA citrus production practices and regions appear to significantly limit the environmental risk of preharvest contamination. However, recent serious incidents involving the bacterial pathogen Listeria monocytogenes, associated with CA apple, have prompted proactive measures to more carefully assess postharvest risks and develop validated interventions for citrus system-wide. Confidentially enrolled handlers will participate in a detailed survey for indicator Listeria and L. monocytogenes. The outcome will be the development of model Environmental Monitoring Program (EMP) and guidance in establishing an environmental-zone Master Sanitation Schedule linked to EMP-outcomes for California fresh citrus packinghouses. The anticipated outcomes are expected to include a general overview and report-card of the CA citrus packing environment and identification of potential sources of Listeria related to industry growing regions and harvest/postharvest practices. From this knowledge-gap closing effort, measureable improvements in reduced L. monocytogenes prevalence will result.

Technical Abstract

Fresh citrus is an important global commodity, a major specialty crop in the Pacific states and remains important in California. The 2014-15 CA Agricultural Statistics Review places the combined value of oranges, lemons, and tangerines at over $ 2 billion dollars farm gate value and all three are in the Top 15 Specialty Crops by value. Fresh whole citrus has not experienced an incident of recall, illness, or outbreak and CA citrus production practices and regions appear to significantly limit the environmental risk of preharvest contamination. However, recent serious incidents with other tree fruit have prompted proactive measures to more carefully assess postharvest risks and develop validated interventions. The systematic and thorough identification of prevalence, specific harborage sites, and source-tracking of transient and resident Listeria monocytogenes  rarely occurs in the absence of a ‘crisis’ incident for company and its commodity group by association. Through discussions, The CA citrus leadership has focused on developing a detailed cross-seasonal baseline of Listeria incidence among confidentially enrolled handlers towards the development of a model Environmental Monitoring Program (EMP) and guidance in establishing an environmental-zone Master Sanitation Schedule linked to EMP-outcomes for California fresh citrus packinghouses. The anticipated outcomes are expected to include 1. A general overview and report-card of the CA citrus packing environment; 2.  Identify potential sources of chronic and seasonal introduction and transfer of Listeria related to industry growing regions and harvest/postharvest practices; 3. Resolve potential citrus industry challenges in verification of detection outcomes for Listeria sp. and L. monocytogenes of EMP programs; 4. Provide a data-basis for developing system-wide industry guidance and standards for EMPs; and 5. From this knowledge-gap closing effort, implement any identified and practical corrective actions and document a measureable improvement in reduced L. monocytogenes (Lm) prevalence over the two-year period. To achieve this baseline information, a spatial and traffic-flow map is developed from culture confirmed isolates and Pulsed-Field Gel Electrophoresis (PFGE) and PCR-based serogrouping. More detailed sub-typing and diversity analysis will be conducted by future Whole Genome Sequencing with an external partner. This sub-typing and diversity assessment potentially informs us about specific sources of transient and persistent L. monocytogenes at the postharvest facilities as well as the potential for movement and transference to Zone 1 surfaces during daily operation. In areas found to be Listeria positive, we will preliminarily evaluate the efficacy of emerging, registered hard-surface, non-porous, and porous surfaces sanitizers and disinfectants on diverse non-contact surfaces which test positive for genus Listeria in enrolled citrus packinghouses. This information further guides the prioritization of cleaning and sanitation scheduling of Zone 2 and 3, which may be high-risk non-direct contact transfer areas. Our approach is; You can’t reasonably clean and sanitize all zones in a packing house every day.” Setting these frequencies and critical non-contact but high harborage areas for biofilm preventive sanitation is not always obvious. Understanding common points and routes or sources of L. monocytogenes in CA citrus will greatly benefit the practical and rationale design of Master Sanitation Schedules.