Listeria monocytogenes Flashcards
Named after
Joseph Lister (pioneer of antiseptic surgery)
characteristics
Gram positive, rod-shaped becaterium, non - spore
forming, motile (peritrichous flagellae, facultative
anaerobic bacterium.
a human foodborne pathogen causing listeriosis.
found in
Is ubiquitous in nature, found in moist environments,
decaying vegetation and soil.
Other 7 Listeria species
L. ivanovii, L. seeligeri, L. welshimeri, L. innocua, L. marthi, L. rocourtiae, L. grayi
but not pathogenic to humans
foods associated
Ready-to-eat foods, raw milk, soft cheese, smoked
seafood, raw vegetables
causing
Listeriosis
High risk gps
Affects immunocompromised individuals (elderly, pregnant, neonates, HIV patients, transplantation patients)
The state of the immune system plays an important role
Growing temp
able to grow at refrigeration temperatures (even at -1’C)
fatality rate
30%
The most deadly foodborne pathogen (causes most deaths than any other foodborne pathogen but responsible for small fraction of cases
L. monocytogenes infectious cycle
Infected animals, or milk, survival in the environment (decaying vegetation, ubiquitous, present in food factory environment, biofilms) –>
–> Contamination of foods (Stress resistant can survive HHP, acidic pH, heat etc.)
–> Stomach (acidic pH)
–> Localization in the intestine (anaerobic conditions, osmotic pressure, competitive microflora etc.)
–> Expression of inlA –> binding to e-cadherin –>
–> Phagocytosis (oxidative stress, acidic pH) –> intracellular cycle –> listeriosis.
L. monocytogenes intracellular action
–> phagocytosis –> Escape from phagolysosome
–> replication in the cytoplasm –> polymerization of hosts actin (rocket-like movement) –> spread to blood, nervous system, brain, fetus.
Absence of flagella at 37oC –> evasion from immune system –> Usually flu-like symptoms without typical intestinal infection symptoms
Misdiagnosis is common –> listeriosis
Treatment
penicillin or ampicillin
Incubation time
3 – 70 days
Long incubation –> difficult to link food with listeriosis
Listeriosis symptoms
sometimes prior to the onset of listeriosis diarrhea or other gastrointestinal symptoms can occur.
Mild flu-like symptoms initially followed by meningitis or septicemia (Fever, stiff neck, confusion, weakness, vomiting, sometimes preceded by diarrhea) –> can lead to permanent disability
Pregnant women –> infection of fetus –> abortion,
stillbirth, or delivery of acutely ill infant
Prevention of listeriosis
Good implementation of HACCP and prevention of post processing contamination. Limit for all ready-to-eat foods can provide 1- 5 log reduction
Phages are viruses that are pathogenic for bacteria.
It is usually sprayed on the surface.
