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Unformatted text preview: Lecture 8 Listeria Lecture 8 Listeria Overview: GramPos Rods Overview: GramPos Rods
Gram+ Rod Spores Shape
regular irregular +
Clostridium - Acid Fast Listeria Branched Filaments CoryneNocardia Mycobacterium bacterium CMN-Group + - + Classification Classification Family Genus Mycobacteriaceae Listeria Species Six species: L.monocytogenes General Characteristics General Characteristics Short rod; diplococci /diplobacillus gram positive Motile at room temp (2025oC) but not at 37oC Grows at 4oC!! (145oC) Supports high salt; BetaHemolytic Facultative anaerobe NOT Acid fast Non spore forming Peritrichous flagella Peritrichous flagella Flagella expressed at room temp but not at body temperature Gram stain Gram stain EPIDEMIOLOGY Bacteria ubiquitous (soil, water, feces of mammals) leads to food contamination Outbreaks mostly associated with contaminated food products (meat, soft cheese, raw vegetables, non pasteurized milk) Seasonal variety of incidences (peak in summer months) Bacteria grow in the fridge!! HistoryEpidemiology HistoryEpidemiology 1981 L. monocytogenes was identified as a cause of foodborne illness. An outbreak of listeriosis in Halifax, Nova Scotia involving 41 cases and 18 deaths, mostly in pregnant women and neonates, was epidemiologically linked to the consumption of coleslaw containing cabbage that had been treated with L. monocytogenes contaminated raw sheep manure. EPIDEMIOLOGY Infections in healthy adults are asymptomatic (or mild flulike symptoms) DISEASE in humans restricted to immunocompromised (no Tcells), pregnant woman and neonates Symptomatic disease has highest mortality rate of any foodborne pathogen (2030%) Pregnant women They are about 20 times more likely than other healthy adults to get listeriosis. About onethird of listeriosis cases happen during pregnancy. Newborns Newborns rather than the pregnant women themselves suffer the serious effects of infection in pregnancy. 3rd most common cause of meningitis in newborns Persons with weakened immune systems Persons with cancer, diabetes, or kidney disease Persons with AIDS They are almost 200 times more likely to get listeriosis than people with normal immune systems. Persons who take glucocorticosteroid medications EPIDEMIOLOGY EPIDEMIOLOGY EPIDEMIOLOGY Those are the reported cases but estimated 20003000 cases per year 500 death per year In severe cases (meningitis) mortality up to 25% Pathogenesis Pathogenesis Bacteria are able to cross three tight barriers in host 1) after ingestion, invasion of intestinal epithelium and subsequent colonization of internal organs 2) after systemic bacteremia, crossing of bloodbrain barrier (meningitis) 3) in pregnant women, crossing of the fetoplacental barrier (infection of fetus) Pathogenesis Bacteria are facultative intracellular Can survive in phagocytotic cells and can induce phagocytosis in nonphagocytotic cells (endo and epithelial cells) “Zipper Mechanism” Pathogenesis: Virulence Factors Internalin A and B (Adhesins/Invasins) bind to receptor and initiate actin remodeling for induced phagocytosis (“Zipper Mechanism”) Listeriolysin O (LLO) exotoxin, pore forming, expressed only by bacteria in phagosomes, essential for escape of bacteria into host cell cytosol Internalin Internalin Internalinmediated traversal of the intestinal and fetoplacental barriers. (A) Histological section of a guinea pig intestinal sample after oral infection with L. monocytogenes during 144 h. Immunolabeling using antiL. monocytogenes antibodies (red) reveals bacterial proliferation within enterocytes (scale bar: 10 μm, reprinted from Lecuit et al. ). (B) Placental explant infected with L. monocytogenes during 1 h, followed by 2 h incubation with gentamicin and 21 h incubation with culture medium without antibiotics. AntiL. monocytogenes antibodies (magenta) labeled replicating bacteria within the explant (nuclei labeled in blue) which is delimited by Ecadherin (green) (scale bar: 10 μm, reprinted from Lecuit et al. Pathogenesis: Virulence Factors Phospholipase C (PlcA and PlcB): secreted important for escape of bacteria into cytosol; disrupts phagosome lipid bilayer (→CAMP reaction!) ActA: induces polarized actin polymerization; essential for celltocell spread of bacteria Movie Movie http://www.nature.com/nrmicro/animation/index.htm Dendritic Nucleation/Array Treadmilling Model for Protrusion of Dendritic Nucleation/Array Treadmilling Model for Protrusion of the Leading Edge Actin Polymerization Actin Polymerization Highly dynamic process Arp2/3 complex essential for polymerization Invasion Invasion Actin tails and ActA protein Actin tails and ActA protein Actin tails induced by different Actin tails induced by different pathogens Actin Tails Actin Tails ActA directly activates the Arp2/3 complex Consequences of pathogenesis Consequences of pathogenesis mechanism Due to direct celltocell transmission, bacteria evade humoral IR LLO exotoxin not implicated in clinical manifestation of disease (regulated intracellular expression!) Clinical Diseases Clinical Diseases
Neonatal Disease 1) EarlyOnset (inutero), “Granulomatosis Infantiseptica” high mortality unless treated promptly disseminated abscesses and granulomas 2) LateOnset (occurs 23 weeks after birth) meningitis symptoms similar to Group B Streptococcal meningitis Symptoms: fever, headache, stiff neck, vomiting In both cases immediate antibiotic treatment necessary!! (even before conclusive lab diagnosis) Clinical Diseases Healthy Adults benign, flulike symptoms, rarely causes disease Elderly (>50), pregnant women, patients on immunosupressive drugs Meningitis Severely Immunosupressed Adults (AIDS) bacteremia, meningitis,→risk of death Clinical Diseases Clinical Diseases Meningitis Interior view of infected brain Prophylaxis Prophylaxis
The general guidelines recommended for the prevention of listeriosis are similar to those used to help prevent other foodborne illnesses. Thoroughly cook raw food from animal sources, such as beef, pork, or poultry. Wash raw vegetables thoroughly before eating. Keep uncooked meats separate from vegetables and from cooked foods and readytoeat foods. Avoid unpasteurized (raw) milk or foods made from unpasteurized milk. Wash hands, knives, and cutting boards after handling uncooked foods. Consume perishable and readytoeat foods as soon as possible Prophylaxis Prophylaxis
People at highrisk (pregnant women/AIDS patients) should avoid eating raw foods (meat, soft cheese vegetables) Do not eat hot dogs, luncheon meats, or deli meats, unless they are reheated until steaming hot. Avoid getting fluid from hot dog packages on other foods, utensils, and food preparation surfaces, and wash hands after handling hot dogs, luncheon meats, and deli meats. Do not eat soft cheeses such as feta, Brie, and Camembert, blueveined cheeses, or Mexicanstyle cheeses such as queso blanco, queso fresco, and Panela, unless they have labels that clearly state they are made from pasteurized milk. Do not eat refrigerated pâtés or meat spreads. Prophylaxis Prophylaxis No vaccine available Treatment/Prophylaxis Treatment/Prophylaxis Immediate treatment with ampicillin (B Lactam) +gentamicin (aminoglycoside) (IV!; 3 weeks) Hard to find bacteria in lesions, Cerebrospinal fluid (CSF) Cultures cold enrichment of clinical specimens (Blood,CSF) gram positive rod/bacillus CAMP positive, hippurate positive, Catalase positive motility in semisolid agar! Diagnosis not needed to guide therapy!! No time!! Lab Diagnosis Lab Diagnosis Umbrellashaped pattern in Umbrellashaped pattern in semisolid agar ...
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This note was uploaded on 01/24/2011 for the course BSCI 424 taught by Professor Staff during the Fall '08 term at Maryland.
- Fall '08