Bacillus Anthracis: Morphology, Pathogenesis, and Diagnosis
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Questions and Answers

What is the shape of the spore in Bacillus anthracis?

  • Rectangular
  • Spiral
  • Rounded
  • Oval (correct)

    • What is unique about the flagella of Bacillus anthracis?

  • They are polar
  • They are peritrichous
  • They are few in number
  • They are absent (correct)

    • What is the temperature range for the growth of Bacillus species?

  • 30 to 80 ºc
  • 15 to 60 ºc
  • 25 to 75 ºc (correct)
  • 20 to 50 ºc

    • What is the composition of the capsule in Bacillus anthracis?

    <p>Poly-d-glutamic acid</p> Signup and view all the answers

    What is the function of the Edema factor in Bacillus anthracis?

    <p>Acts as adenylyl cyclase</p> Signup and view all the answers

    Who discovered that Anthrax was the first communicable disease transmitted by inoculation of infected blood?

    <p>Davaine</p> Signup and view all the answers

    What is the typical size range of Bacillus anthracis?

    <p>3 to 8 by 1 to 1.3 µm</p> Signup and view all the answers

    What is the purpose of the McFadyean reaction?

    <p>To identify the presence of a capsule</p> Signup and view all the answers

    What is the name of the person who developed the first live attenuated bacterial vaccine?

    <p>Louis Pasteur</p> Signup and view all the answers

    What is the purpose of the Protective antigen?

    <p>To bind to host cell receptors and facilitate entry of other fragments</p> Signup and view all the answers

    What is the type of hemolysis seen in Bacillus anthracis?

    <p>Non-hemolytic</p> Signup and view all the answers

    What is unique about the spores of Bacillus species?

    <p>They are heat-resistant</p> Signup and view all the answers

    Who is the scientist who first isolated Bacillus anthracis in pure culture and showed that it possesses spores?

    <p>Robert Koch</p> Signup and view all the answers

    How many species are there in the genus Bacillus?

    <p>More than 50 spp.</p> Signup and view all the answers

    What is the basis of the original anthrax vaccine prepared by Pasteur?

    <p>Loss of plasmid makes the strain avirulent</p> Signup and view all the answers

    What is the composition of the anthrax capsule?

    <p>Poly d-glutamate</p> Signup and view all the answers

    How does the anthrax capsule prevent host defense?

    <p>It inhibits complement mediated phagocytosis</p> Signup and view all the answers

    What is the mode of transmission of cutaneous anthrax?

    <p>Cutaneous exposure to spores</p> Signup and view all the answers

    What is the characteristic skin lesion of cutaneous anthrax?

    <p>Malignant pustule with a coal-black necrotic eschar</p> Signup and view all the answers

    What is the prognosis of cutaneous anthrax?

    <p>Self-limiting with a 10-20% risk of septicaemia or meningitis</p> Signup and view all the answers

    What is the most common form of anthrax used in bioterrorism?

    <p>Pulmonary anthrax</p> Signup and view all the answers

    What is the primary mode of transmission of animal anthrax?

    <p>Ingestion of contaminated soil or water</p> Signup and view all the answers

    What is the preparation source of Adsorbed (Alum Precipitated) Toxoid Vaccine?

    <p>From the protective antigen</p> Signup and view all the answers

    What is the route of administration for post-exposure prophylaxis of Anthrax Vaccines?

    <p>Subcutaneous</p> Signup and view all the answers

    What is the characteristic of the colony of Anthrax bacilli under low power microscope?

    <p>Medusa head appearance</p> Signup and view all the answers

    What is the characteristic of Anthrax bacilli in broth?

    <p>Turbidity absent</p> Signup and view all the answers

    What is the characteristic of Anthracoid bacilli?

    <p>Motile</p> Signup and view all the answers

    What is the dosing schedule for pre-exposure prophylaxis of Anthrax Vaccines?

    <p>0, 1, and 6 months</p> Signup and view all the answers

    What is the characteristic of Anthrax bacilli on blood agar?

    <p>No hemolysis</p> Signup and view all the answers

    What is the characteristic of Anthracoid bacilli in gelatin stab agar?

    <p>No inverted fir tree appearance</p> Signup and view all the answers

    What is the typical habitat of Bacillus cereus?

    <p>Soil</p> Signup and view all the answers

    Which type of toxin is responsible for the diarrheal type of food poisoning caused by Bacillus cereus?

    <p>Diarrheal toxin</p> Signup and view all the answers

    What is the temperature at which Bacillus cereus does not grow?

    <p>45°C</p> Signup and view all the answers

    Which of the following is a characteristic of Bacillus cereus?

    <p>Motile and non-capsulated</p> Signup and view all the answers

    Which type of food is commonly associated with the emetic type of food poisoning caused by Bacillus cereus?

    <p>Rice</p> Signup and view all the answers

    What is the incubation period for the diarrheal type of food poisoning caused by Bacillus cereus?

    <p>8-16 hours</p> Signup and view all the answers

    Which antibiotic is Bacillus cereus resistant to?

    <p>Penicillin</p> Signup and view all the answers

    What is the purpose of the MYPA and PEMBA media in the laboratory diagnosis of Bacillus cereus?

    <p>To isolate the bacteria from feces</p> Signup and view all the answers

    Study Notes

    General Features of Bacillus

    • Genus Bacillus consists of aerobic, heat-resistant, spore-forming bacteria
    • Gram-positive, but tend to be decolorized easily
    • Generally motile with peritrichous flagella, except for Bacillus anthracis
    • Most Bacillus species form catalase and produce acid, but not gas from glucose
    • The genus includes psychrophilic, mesophilic, and thermophilic species, with a temperature range of 25-75°C and a minimum of 5°C
    • Spores are ubiquitous, found in soil, dust, water, and air, and are common contaminants in bacteriological culture media

    Species of Bacillus

    • There are over 50 species in the genus Bacillus
    • Medically important species include Bacillus anthracis and Bacillus cereus
    • Bacillus anthracis causes anthrax, while Bacillus cereus is a food poisoning and opportunistic pathogen

    History of Bacillus anthracis

    • 1849: Pollender was the first to observe Bacillus anthracis under a microscope
    • 1850: Davaine showed that anthrax was the first communicable disease transmitted by inoculation of infected blood
    • 1876: Robert Koch isolated Bacillus anthracis in pure culture and showed that it possesses spores
    • Koch's postulates were based on Bacillus anthracis
    • 1881: Louis Pasteur developed the first live attenuated bacterial vaccine, the anthrax vaccine

    Morphology of Bacillus anthracis

    • One of the largest of pathogenic bacteria, with a size of 3-8 by 1-1.3 μm
    • Gram-positive, non-acid fast, straight, sporing bacilli
    • Capsule composed of d-glutamic acid
    • McFadyean reaction: a characteristic reaction of Bacillus anthracis, where capsular material is visible around the bacilli

    Culture of Bacillus anthracis

    • NA: irregular, round, 2-3 mm, raised, dull, opaque, grayish-white colonies with a Medusa head appearance
    • BA: non-hemolytic, with a narrow zone of hemolysis
    • Gelatin: inverted fir tree appearance
    • Selective media: PLET, polymyxin, lysozyme, and EDTA

    Virulence Factors and Pathogenesis of Bacillus anthracis

    • Capsule: composed of poly d-glutamic acid, interferes with phagocytosis, and loss of plasmid controlling capsule production leads to loss of virulence
    • Anthrax Toxin: a three-component protein exotoxin consisting of edema factor, protective antigen, and lethal factor
    • Toxin fragments are not toxic individually, but in combination, they produce local edema and generalized shock

    Clinical Manifestations of Bacillus anthracis

    • Transmission: based on mode of infection, human anthrax presents in three ways: cutaneous, inhalation, and ingestion
    • Clinical types: cutaneous, pulmonary, and intestinal anthrax
    • Cutaneous anthrax: characterized by a malignant pustule, begins as a papule, then becomes a painless vesicle, followed by a coal-black, necrotic eschar surrounded by non-pitting edema
    • Pulmonary anthrax: characterized by hemorrhagic pneumonia, bacilli spread by lymphatics or blood, and may lead to bacteremia, hemorrhagic mediastinitis, and hemorrhagic meningitis

    Animal Anthrax

    • Anthrax is primarily a zoonotic disease
    • Animals affected: herbivores, such as cattle, sheep, and horses
    • Acquired by ingestion of spores present in soil
    • Presentation: fatal septicaemia
    • Infective materials: discharges from mouth, nose, and rectum

    Vaccines

    • Adsorbed (Alum Precipitated) Toxoid Vaccine: prepared from the protective antigen, safe and effective for human use, indicated for pre-exposure and post-exposure prophylaxis
    • Anthrax Vaccines: indication, route, and dosing schedule vary depending on the type of vaccine and the population being vaccinated

    Bacillus cereus

    • Normal habitant of soil
    • Widely isolated from vegetables, milk, cereals, spices, meat, and poultry
    • Causes food poisoning, with two types: diarrheal and emetic
    • Diarrheal type: characterized by diarrhea, fever, and rarely nausea, caused by a heat-labile toxin
    • Emetic type: characterized by vomiting, abdominal cramps, and diarrhea, caused by a heat-stable toxin

    Laboratory Diagnosis and Treatment

    • Sample: feces
    • Culture isolation: MYPA (mannitol, egg yolk, polymyxin, phenol red, and agar) and PEMBA (polymyxin B, egg yolk, mannitol, bromothymol blue, and agar)
    • Treatment: susceptible to clindamycin, erythromycin, vancomycin, aminoglycosides, and tetracycline, but resistant to penicillin and trimethoprim

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    Description

    Learn about the morphology, pathogenesis, clinical features, and diagnosis of Bacillus anthracis, a Gram-positive, aerobic bacillus that forms heat-resistant spores. Understand its lab diagnosis, prevention, and treatment.

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