Term
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Definition
• Cell wall contains a waxy lipid called mycolic acid
• The unusual cell wall results in a number of unique characteristics
– Slow growth
– Protection from lysis once the bacteria are phagocytized
– Capacity for intracellular growth
– Resistance to Gram-staining, detergents, many antimicrobial drugs, and dessication |
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Term
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Definition
• 3 main mycobacterial diseases in humans:
– Tuberculosis
– Leprosy
– Buruli ulcer
• Estimated 1/3 of world population is infected with TB. It is the number 3 cause of death from infectious disease; number 1 from a single organism. 15 million cases in U.S. |
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Term
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Definition
• Respiratory disease cause by Mycobacterium tuberculosis
• Cases are declining in the United States but it is pandemic in other parts of the world
• Virulent strains of M.tuberculosis contain the cell wall component, cord factor, that is necessary to cause disease |
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Term
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Definition
• 3 types of tuberculosis
– Primary TB
• Results from the initial infection with M.tuberculosis
– Secondary TB
• Reestablishment of an active infection after a period of dormancy
– Disseminated TB
• Results when the infection spreads throughout the body |
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Term
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Definition
• Prior to the work of Robert Koch, TB was though to be a genetic disease.
• Pasteurization of milk and the isolation of infected patients in sanatoriums, reduced the incidence of TB in the U.S.
• Populations at high risk are those which contact infected patients and those with immunodeficiencies (HIV).
• Diagnosis by stethoscope, x-rays, and skin tests (OT =old tuberculin; PPD =purified protein derivative), and culturing. |
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Term
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Definition
Fluorescent
Acid-Fast Stain
of Sputum
(AFB per field)
0 to >9 = 4+ |
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Term
| TB Diagnosis, Treatment, and Prevention |
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Definition
• Diagnosis
– Tuberculin skin test identifies individuals with previous exposure to M. tuberculosis by the presence of a hard, red swelling at the test site
– Chest x-rays are used to identify individuals with active disease
• Treatment
– Treatment with common antimicrobials is difficult because the bacteria grow slowly and can live within macrophages
– Combination therapy must be used for a number of months to treat the disease |
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Term
Skin Testing for Tuberculosis:
Diagnosis, Treatment, and Prevention |
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Definition
• Prevention
– Prophylactic use of antibacterial drugs is used to treat patients who have shown a conversion from a negative to a positive skin test or were exposed to active cases of tuberculosis
– Inmmunization with BCG vaccine is used in countries where TB is common |
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Term
| Drugs Used to Treat Tuberculosis: |
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Definition
• Directly observed therapy (DOT)
• Rifater =INH + rifampin + pyrazinamide.
• Vaccine = Bacille Calmet-Guerin (BCG) strain of M. bovis. BCG about 80% effective in kids,only 20-50% effective in adults. |
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Term
| Mycobacterium Other Than Tuberculosis (MOTT |
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Definition
• Mycobacterium avium complex (MAC)
– Secondary infections in AIDS patients
• Mycobacterium Kansasii
– TB-like disease (milder)
• Mycobacterium fortuitum
– Post-surgical skin infections
• Mycobacterium marinum
– Localized skin infections
• Mycobacterium scrofulaceum
– Scrofula (ulcerating, draining cervical lymph nodes |
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Term
Swimming pool granuloma caused by Mycobacterium marinum
Leprosy |
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Definition
• Caused by Mycobacterium leprae
• Bacteria have never been grown in cell-free culture
• Cases of leprosy are becoming relatively rare
• Transmission is via person-to-person contact or through a break in the skin |
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Term
|
Definition
• 2 different forms of disease
– Tuberculoid leprosy
• High cell-mediated response; low antibody
• Nonprogressive disease that is characterized by loss of sensation in regions of the skin
– Lepromatous leprosy
• Low cell-mediated response; high antibody
• Produces gradual tissue destruction that results in the loss of facial features, digits, and other body structures |
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Term
| Leprosy: Diagnosis, Treatment, and Prevention |
|
Definition
• Diagnosis
– Based on the signs and symptoms of the disease
• Loss of sensation in skin lesions in the case of tuberculoid leprosy
• Disfigurement in the case of lepromatous leprosy
• Treatment
– Treatment with a combination of antimicrobial drugs
– Lifelong treatment is sometimes needed
• Prevention
– Avoid exposure; some protection from BCG |
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Term
|
Definition
• Cannot be cultivated in vitro; only in the footpads of mice and the bellies of 9-banded armadillos.
• Endemic in certain tropical and subtropical regions; > 10 million cases worldwide.
• Incubation period is long: 2-5 yrs; 40 yrs doc.
• Treatment is:
– Tuberculoid form: dapsone and rifampin; 6 mo.
– Lepromatous form: dapsone, rifampin, & clofazimine for up to 2 yrs; then dapsone for >10 yrs. |
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Term
Two Forms of Leprosy:
Tuberculoid Leprosy:
Lepromatous Leprosy:
Lepromatous Leprosy:
Borderline Leprosy:
Leprosy Before After 1 yr Treat.
Mycobacterium ulcerans |
|
Definition
Beruli ulcer.
• Associated with slow moving water; enters skin through abrasions and grows extracellularly.
• Produces a polyketide (lipid) toxin, mycolactone, that destroys subcutaneous tissue; skin on top eventually dies and sloughs off producing a clean ulcer that may cover the entire chest or back. Mycolactone is also a powerful immune suppressing agent.
• No proven drug therapy; must excise infected skin and use skin grafts.
• One of the most serious emerging pathogens today |
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Term
| Mycobacterial Infections in AIDS Patients |
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Definition
• Mycobacterium avium-intracellulare is the most common mycobacterial infection among AIDS patients in the United States
• Infections are a result of ingestion of contaminated food or water
• Infections can simultaneously affect almost every organ and result in massive organ failure
• Treatment is difficult due to the disseminated nature of the infection |
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Term
|
Definition
• Small, Gram-positive rods that are often found on the skin
• Propionibacterium acnes is the species most commonly involved in human infections
• Causes much of the acne of adolescents and young adults
• May also be an opportunistic pathogen
• Treatment often involves the use of antimicrobial drugs though many cases require no treatment |
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Term
|
Definition
| Partially acid-fast to acid-fast soil bacilli; may cause a TB-like disease. |
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Term
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Definition
| Anaerobic gram-positive filamentous soil bacilli; oral opportunists. |
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Term
|
Definition
| Filamentous branching gram-positive soil bacilli; make most of our antibiotics. |
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Term
|
Definition
• Normal member of the surface microbiota of human mucous membranes
• Produces opportunistic infections of the respiratory, gastrointestinal, urinary, and female genital tracts
• Actinomycosis results when the bacteria enters breaks in the mucous membrane
– Disease is characterized by the formation of many abscesses connected by channels in the skin or mucous membranes
• Diagnosis of actinomycosis can be difficult because other organisms cause similar diseases |
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Term
|
Definition
Actinomycosis
(periodontal extension)
Nocardiosis
(pulmonary extension) |
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