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18 Cards in this Set
- Front
- Back
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What is Listeria |
Listeria is a genus of bacteria that contains 10 species,each containing two subspecies.
“opportunistic pathogen,” |
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Morphology |
Intracellular, small, Gram positive , rod-shaped, facultatively anaerobic, and non-spore forming.
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Habitat |
In raw milk and foods made from raw milk.
Can also live in food processing plants |
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source |
Ready-to-eat meats and hot dogs
Refrigerated spreads Unpasteurized (raw) milk and dairy products Soft cheese made with unpasteurized milk, such as queso fresco, Feta, Brie, Camembert Refrigerated smoked seafood Raw sprouts |
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Important pathogenic species of Listeria?
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Listeria monocytogenes.
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Most Important property |
It possess uniquephysiological characteristics that allow growth atrefrigeration temperature that are usually adverse formost pathogenic, food-borne bacteria.
The organism canalso tolerate a pH between 5.4 and 9.6 |
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Growth conditions |
Temperature of 86-98.6 degrees F (30-37 degrees C), but also multiply better than all other bacteria at refrigerator temperatures, Incubation of 3-70 day |
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What type of hemolytic reaction
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narrow zone of Beta-hemolysis
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Media used for growth
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Blood Agar, Fraser broth, PALCAM agar ( Polymixin Acriflavine Lithium chloride Ceftazidime Aesculin Mannitol) ,ALOA, and RAPID'L
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Biochemicals used |
catalase positive, oxidase negative, fermentation of carbohydrates to acid but not to gas, hydrolysis of esculin and sodium hippurate, methyl red positive, ammonia production from arginine, negative reaction for hydrogen sulfide production, indole negative, nitrate reductase negative, no gelatin liquefaction, no hydrolysis of starch and no urea hydrolysis.
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Test for conformation |
CAMP test
Listeria monocytogenes shows an enhanced zone of hemolysis, forming an arrow head towards the S. aureus culture |
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Pathogenisis |
Listeria uses the cellular machinery to move around inside the host cell: It induces directed polymerization of actin by the ActA transmembrane protein, thus pushing the bacterial cell around
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Diseases caused by Listeria |
Rare bacterial disease, listeriosis( bacterial zoonitic diseases that occur in humans)
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Target group |
Elderly, pregnant mothers, and patients infected with HIV or cancer,People with weakened immune systems,Organ transplant patients who are receiving drugs to prevent the body from rejecting the organ
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Symptoms of Listeriosis and clinical manifestations
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Fever, stiff neck, confusion, weakness, vomiting, sometimes preceded by diarrhea .
clinical manifestations are sepsis and meningitis |
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Prevention
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Effective sanitation of food contact surfaces.
Alcohol is an effective topical sanitizer against Listeria. Quaternary ammonium can be used Refrigerated foods in the home should be kept below 4 °C (39.2 °F) to discourage bacterial growth. |
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Treatment
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Ampicillin, penicillin, or amoxicillin for invasive listeriosis, and gentamicin is often added in patients with compromised immune systems.
Trimethoprim-sulfamethoxazole, vancomycin, andfluoroquinolones can be used in cases of allergy to penicillin. |
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for more information
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