Term
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Definition
• Gram-positive non-spore-forming, coccobacillus
• Found in soil, water, mammals, birds, fish, and insects
• Enters body in contaminated food and drink
• Listeria produces no toxins or enzymes
• Virulence is directly related to the bacteria’s ability to live within cells |
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Term
How Listeria Avoids the Immune System
Diagnosis, Treatment, and Prevention |
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Definition
• Diagnosis
– Presence of the bacteria in the cerebrospinal fluid
– Rarely seen by Gram-staining because so few Listeria cells are required to produce disease
• Treatment
– Most antimicrobial drugs inhibit Listeria
• Prevention
– Difficult because the organism is ubiquitous
– At risk individuals should avoid undercooked vegetables, unpasteurized milk, undercooked meat, and all soft cheeses |
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Term
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Definition
• Gram-positive coccobacilli; resistant to heat, cold, salt, and pH extremes.
• Most infections in humans from ingestion of contaminated milk or meat products.
• Pregnant women are highly susceptible to a mild form of the disease, which can be transmitted to the infant prenatally, or postnatally, causing meningitis.
• Immunocompromised individuals are at higher risk of infection.
• Treated with ampicillin; prevented by pasteurization and proper cooking. |
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Term
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Definition
• Ubiquitous on plants and in animals and humans
• Colonizes the skin and the respiratory, gastrointestinal, urinary, and genital tract
• Corynebacterium diphtheriae, the cause of diphtheria, is the most widely known
– Transmitted from person to person via respiratory droplets or skin contact
– Endemic in poor parts of the world that lack adequate immunization
– Diphtheria toxin is responsible for the signs and symptoms of diphtheria |
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Term
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Definition
• Severe respiratory infections of nonimmune patients produce the signs and symptoms of diphtheria
– Pseudomembrane results from fluid that has thickened and adheres throughout the respiratory tract
– The pseudomembrane can completely occlude the respiratory passages and cause suffocation
• Cutaneous diphtheria causes cell death and formation of a pseudomembrane on the skin |
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Term
| Diphtheria: Diagnosis, Treatment, and Prevention |
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Definition
• Diagnosis
– Initial diagnosis is based on the presence of pseudomembrane
– Absolute identification is based on the Elek test
• Antibodies against the toxin react with toxin in a sample of fluid from the patient (immunodif)
• Treatment
– Administration of antitoxin to neutralize toxin before it binds to cells
– Penicillin and erythromycin kill the bacteria
• Prevention
– Immunization with the DPT vaccine |
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Term
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Definition
• Small pleomorphic rods in ‘V’s, ‘L’s, and palisades. Contain metachromatic granules.
• Diphtheria caused by C. diphtheriae which is not pathogenic until it has been lysogenized by the beta-corynephage.
• Diphtheria toxin is a powerful exotoxin which is absorbed by tissue and prevents eukaryotic protein synthesis; causes formation of pseudomembrane in the throat (composed of dead tissue) which can obstruct airway. |
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Term
Corynebacterium diphtheriae
Diphtheria |
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Definition
• Toxin can also damage the heart and CNS.
• Bull-neck caused by enlarged cervical lymph nodes is common.
• Transmission is from person-to-person
• Diagnosis is by clinical & serological tests
• Treatment is antitoxin and penicillin
• Prevented by vaccination
• Schick test determines immune status |
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Term
| Erysipelothrix rhusiopathiae |
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Definition
• Gram-positive rod commonly found in farm animals (especially tonsils of pigs).
• Causes epidemics of swine erysipelas.
• Humans at risk are those who handle animals.
• Portal of entry is usually a scratch on the hand or arm; org multiplies and causes erysipeloid.
• Erysipeloid is characterized by dark red lesions that burn and itch.
• Treated with penicillin or erythromycin.
• Prevented by wearing gloves. |
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