Listeria Gram Stain Listeria Listeria Culture CAMP test

Listeria

Gram Stain Listeria

Listeria Culture

CAMP test

Catalase +ve

MALDI-TOF: Good for Listeria

Listeria identification • • Gram stain Beta-haemolysis CAMP test Tumbling motility Esculin hydrolysis Catalase positive, oxidase negative API coryne MALDITOF!

Other facts Listeria monocytogenes • • Psychrophile Easily destroyed by cooking, Colonises 5 -10% of population. Found in environment (soil and water), animal faeces, raw foods. • Incubation period is 1 -90 days (average 30 days) • Risk groups are pregnant women, neonates, elderly and immunocompromised.

Listeria monocytogenes Pathogenesis • Intra-cellular pathogen • Listeria bacteria have a surface protein “Internalin” • Attach to cells via “E-Cadherin” receptor on epithelial cells. • E-Cadherin receptors specifically present on epithelial cells in intestine, placenta and blood brain barrier.

Listeria in Pregnancy • Often flu like illness in mother • In early pregnancy, foetal infection may result in miscarriage • Maternal listeriosis in the second or third trimester results in a mortality of 40 -50 % for the fetus 4 • In later pregnancy foetal septicaemia may result in damage to multiple organs and stillbirth or neonatal death 3 • The mortality rate varies from 3 – 50 % in live-born neonates infected with listeria 5 • Perinatal listeria within 7 days of birth is often associated with prematurity and fulminant disease. Late onset disease (7 days to six weeks) often presents with meningitis. • Diagnosis with blood cultures.

CNS Listeria infections • • • In top 4 or 5 most common causes of bacterial meningitis. Usually in neonates or elderly. Is 61 elderly? CSF gram positive in 40% CSF glucose not always low. Blood cultures positive 75% Mental fluctuation is more common for listeria meningitis than other bacterial causes of meningitis. • Listeria rhombo-encephalitis is a feared complication of CNS listeria infection with high mortality.

National Listeria Data NZ

Listeria typing • Serotyping 1/2 and 4 only ones that cause problems in humans • PFGE: At least 71 different PFGE subtypes • Asc 1 and Apa 1 enzymes used.

Some risk foods Food type Cold meats Cold cooked chicken Salads (fruit and vegetables) Chilled fish, shellfish and crustacea Cheese Ice cream Other dairy products Examples Unpackaged ready-to-eat from delicatessen counters and sandwich bars Purchased ready-to-eat Pre-prepared or prepackaged salads from salad bars and smorgasbords etc Raw (eg, marinated oysters, sashimi or sushi) and smoked ready-to-eat (eg, salmon) Soft unpasteurised (raw milk) cheese (eg, Roquefort) Soft serve Unpasteurised dairy products

Prevention • Thoroughly cook raw food from animal sources. • Wash raw vegetables thoroughly before eating. • Separate uncooked meats from vegetables, cooked foods and ready-to-eat foods. • Avoid unpasteurized milk or food. • Wash hands, knives, and cutting boards with hot soapy water for at least 20 sec after handling uncooked foods. • Observe all expiration dates on food items. • Consume perishable and ready-to-eat foods as soon as possible. • Do not eat soft cheeses: feta, brier, camembert, blueveined, or Mexican-style etc. • Do not eat refrigerated meat spreads, smoked salmon, smoked seafood; canned or shelf-stable smoked seafood may be eaten. • Listeria monocytogenes is killed by cooking or by heating methods, including pasteurization.