Gram-positive Rods

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Author:
smourer
ID:
237225
Filename:
Gram-positive Rods
Updated:
2013-10-10 21:21:40
Tags:
Leishmania hemoflagellates Phlebotomus amastigote promastigote parasites parasitology corynebacteria diphtheria Bacillus anthracis cereus anthrax woolsorter disease
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Description:
Description of the pathogenic bacterial genuses of Corynebacterium, Bacillus, and Leishmania with morphology, life cycle, epidemiology, symptoms and treatments.
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  1. What is the vector for the old world form of Leishmania?
    Genus of Sand Fly Phlebotomus, only female flies which ingest infected macrophages infected with amastigotes.
  2. What is the vector for the new world form of Leishmania?
    Genus of Sand Fly Lutzomyia, only female flies which ingest infected macrophages infected with amastigotes.
  3. What are L-D bodies?
    The amastigote form of Leishmania named after the finders Leishman and Donovan. Found inside the infected cells, typically macrophages, of the vertebrate host.
  4. Parasitophorous vacuole
    A vacuole formed by the promastigote form of the Leishmania parasite that forms the endoplasmic reticulum of the host macrophage into a vacuole and then transforms into the amastigote from and multiply.
  5. What are the four most important species of Leishmania that cause Leishmaniasis?
    L. donovani, L. tropica, L. major, and L. braziliensis
  6. Leishmania donovani is primarily responsible for what kind of Leishmaniasis?
    Visceral Leishmaniasis is primarily caused by Leishmania donovani. Visceral Leishmaniasis primarily effects the tissues and internal organs.
  7. Leishmania tropica is primarily responsible for what form of Leismaniasis?
    Cutaneous leishmania found in densely populated areas of the Middle East, India, Peru, Bolivia, Brazil, and Mexico as well as other smaller countries
  8. Corynebacteria basics
    • small, slender, pleomorphic, gram-positive rods that tend to stain unevenly.
    • non-motile, unencapsulated, and do not form spores.
    • large genus of diverse habitat
    •     - Most are facultative anaerobes
    •     - Those associated with humans grow aerobically on standard lab media such as blood agar.
  9. Corynebacterium diphtheriae
    • causes an acute respiratory or skin infection that may be life threatening (Diphtheria).
    • rare in the USA thanks to effective vaccination protocols
    •      - DTaP vaccine using toxoid
    • Areas that are not immunized have many serious occurrences of the disease.
  10. C. diphtheriae Epidemiology
    • found in the throat and nasopharynx of carriers and in patients with diphtheria.
    • local infection, usually of the throat, so transferred by respiratory droplets.
    • less commonly transmitted via direct contact.
  11. C. diphtheriae Pathogenicity
    • Caused by single diphtheria exotoxin which inhibits eukaryotic protein synthesis.
    • Exotoxin is a heat stable AB toxin.
    •      -Fragment B binds to the cell membrane
    •      -Fragment A enters the cell and inhibits Elongation Factor 2 (EF-2).
    • Strains of C. diphtheria that produce the toxin do so because they have been infected by a phage which has inserted the genes for the toxin into the bacterial chromosome in a process called phage or lysogenic conversion.
  12. Clinical significance of  C. diphtheria
         -Respiratory Diphtheria
    • strictly a local infection of the throat there it produces a thick psuedomembrane composed of cell debris from the mucosa and inflammatory products.
    • Also indicated by noticeable swelling of the lymph nodes in the neck.

    Absorbtion of the toxin can affect the heart and cause permanent damage as well as heart failure.
  13. Clinical significance of C. diphtheria
         -Cutaneous Diphtheria
    • A puncture wound or cut can introduce the bacteria into the skin leading to a non-healing, chronic ulcer with a grey membrane covering.
    • Often associated with poor hygiene in crowded areas and only infects humans
    • Rarely, exotoxin can lead to tissue degeneration and death.
  14. Immunity to C. diphtheriae
    • toxin is antigenic
    • formalin inactivated toxin = Toxoid
    • toxoid used to produce vaccine
  15. Lab ID of C. diphtheriae
    • should be considered in patients with pharyngitis, low-grade fever, and swelling of the neck (cervical adenopathy).
    • Superficial reddening (erythema) of the pharyx progressing to grey membranes is characteristic.
    • Isolation of the organism is required for definitive diagnosis
    •      - Tinsdale agar is selective and differential for C. diphtheriae.
    •           * other respiratory flora are inhibited, and C. diphtheriae produces black colonies surround by halos by reducing TeO32- to Te-
  16. Treatment for C. diphtheriae
    neutralization of toxin, followed by eradication of the organism

    horse serum antitoxin inactivates circulating toxin

    C. diphtheriae is sensitive to several antibiotics such as erythromycin or penicillin
  17. Prevention of C. diphtheriae infections
    • cornerstone of prevention is vaccination with toxoid.
    • administered as a DTP triple vaccine with tetanus toxoid and pertussis antigens.
    • Initial injections should be given at infancy and boosters every ten years.

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