Bacillus Anthracis: Morphology, Pathogenesis, and Diagnosis

Podcast Beta

Play an AI-generated podcast conversation about this lesson

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?

Poly-d-glutamic acid Signup and view all the answers

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

Acts as adenylyl cyclase Signup and view all the answers

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

Davaine Signup and view all the answers

What is the typical size range of Bacillus anthracis?

3 to 8 by 1 to 1.3 µm Signup and view all the answers

What is the purpose of the McFadyean reaction?

To identify the presence of a capsule Signup and view all the answers

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

Louis Pasteur Signup and view all the answers

What is the purpose of the Protective antigen?

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

What is the type of hemolysis seen in Bacillus anthracis?

Non-hemolytic Signup and view all the answers

What is unique about the spores of Bacillus species?

They are heat-resistant Signup and view all the answers

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

Robert Koch Signup and view all the answers

How many species are there in the genus Bacillus?

More than 50 spp. Signup and view all the answers

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

Loss of plasmid makes the strain avirulent Signup and view all the answers

What is the composition of the anthrax capsule?

Poly d-glutamate Signup and view all the answers

How does the anthrax capsule prevent host defense?

It inhibits complement mediated phagocytosis Signup and view all the answers

What is the mode of transmission of cutaneous anthrax?

Cutaneous exposure to spores Signup and view all the answers

What is the characteristic skin lesion of cutaneous anthrax?

Malignant pustule with a coal-black necrotic eschar Signup and view all the answers

What is the prognosis of cutaneous anthrax?

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

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

Pulmonary anthrax Signup and view all the answers

What is the primary mode of transmission of animal anthrax?

Ingestion of contaminated soil or water Signup and view all the answers

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

From the protective antigen Signup and view all the answers

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

Subcutaneous Signup and view all the answers

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

Medusa head appearance Signup and view all the answers

What is the characteristic of Anthrax bacilli in broth?

Turbidity absent Signup and view all the answers

What is the characteristic of Anthracoid bacilli?

Motile Signup and view all the answers

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

0, 1, and 6 months Signup and view all the answers

What is the characteristic of Anthrax bacilli on blood agar?

No hemolysis Signup and view all the answers

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

No inverted fir tree appearance Signup and view all the answers

What is the typical habitat of Bacillus cereus?

Soil Signup and view all the answers

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

Diarrheal toxin Signup and view all the answers

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

45°C Signup and view all the answers

Which of the following is a characteristic of Bacillus cereus?

Motile and non-capsulated Signup and view all the answers

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

Rice Signup and view all the answers

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

8-16 hours Signup and view all the answers

Which antibiotic is Bacillus cereus resistant to?

Penicillin Signup and view all the answers

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

To isolate the bacteria from feces 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

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

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.