FDSC3940 Listeria

Listeria monocytogenes

gram positive rod

facultative anaerobe

non-spore forming

psychrotrophic

species of Listeria

L. monocytogenes

human pathogen

L. ivanovii

pathogen of ruminant animals

L. innocua

BSL 1 species used as a surrogate in lab experiments

serotyping

based on two cell-surface antigens

Lineages

large phylogenetic groups

clonal complexes

multilocus sequence type assignments targets 7 conserved genes

unique sequence result in a new assigned “number”

Whole genome sequencing (WGS)

comparisons between genomes based on SNPs

used for modern outbreak investigations

Single Nucleotide Polymorphisms (SNPs)

differences in the genomic sequence at a single position base position in the DNA

closely relate species

Pathogen detection database

GenomeYtakr has public health labs

Pathogen Detection Database NCBI collects genomic data from ongoing surveillance efforts

identify clusters of related pathogen genome sequences to identify outbreaks

cantaloupe pack-house

cross-contamination in pack-house with rinsing of cantaloupe

Blue Bell Ice Cream

Listeria contamination 2010-2015 linked to two blue bell facilities

10 cases in 5 years

Detection Methods

FDA BAM

Sample: 25g sample, swab or sponge

1. enrichment in BLEB then add selective reagents

2. selective differential plating on one esculin-containing and one chromogenic agar

3. step 4: re-streak on TSA-YE, confirmation test

Listeria disease burden

Listeriosis is rare but L. monocytogenes in 3rd cause of foodborne illness death (1,600 ill, 260 death)

loss of 4,000 DALYs

listeriosis has high fatality (20%)

febrile gastroenteritis

fever, onset time = 1 day

infectious dose=HIGH

Invasive listeriosis

pregnant women, elderly, immunocompromised

inital flu-like symptoms, pathogen crosses into blood or cerebrospinal fluid

progress into meningitis, septicemia, encephalitis, miscarriage

onset: 1-2 months

mortality: 20-30%

Lm virulence

invade GI —> phagocytosis —> lyse phagosome —> multiply in the cell cytosol —> travel within and between cells

foods associated with Listeria growth

soft cheese, fresh-cut produce, raw and smoked fish, lunch meat, raw meat and milk

natural environment, soil, surface water

mexican style soft cheese

famous listeriosis outbreak in 1985, 96% of victims were hispanic, 93 illness, 44 dead

zero tolerance

<1 CFU per 25g food sample of L. monocytogenes in RTE food

presence would trigger a recall

zero tolerance vs regulatory level

proposed regulatory level in foods which do not support growth (100 CFU/g)

Listeria persistence

long-term persistence in food plants

persist in floor mats

EMP Zone 1

product contact surfaces

EMP zone 2

non-product contact surfaces

exterior, under framework, fridge, switches

EMP Zone 3

other areas within finished product

phone, forklift, drains, wheels

EMP zone 4

area outside RTE room

locker room, cafeteria, hallway, loading dock