4. General Characters of Bacillus spp
Very large Gram positive bacilli
Arranged in long chains
Motile except B. anthracis
Spore forming (outside the host)
Capsulated (inside the host)
Non Fastidious
Facultative anaerobes
Catalase positive
5. Epidemiology
Primarily a disease of herbivores (horses, sheep & cattle).
Humans become infected through contact with these animals
or their products (Skin, Hide, Wool etc).
Spores are inoculated through the skin, ingested or inhaled.
11. Cutaneous Anthrax
Upon introduction of organisms or spores that
germinate, a papule develops
It rapidly evolves into a painless, black, severely
swollen “malignant pustule”, which eventually
crusts over (an eschar)
The organisms may invade regional lymph nodes,
and then the general circulation, leading to a
fatal septicemia
12. Pulmonary Anthrax
Caused by inhalation of spores, this disease is
characterized by progressive hemorrhagic
pneumonia and lymphadenitis (inflammation of
the lymph nodes), and has a mortality rate
approaching 100 percent if untreated
13. Gastrointestinal Anthrax
2-5 days after the ingestion of
endospore-contaminated meat of
animals
Mesenteric lymphadenitis
Massive edema
Mucosal necrosis in small intestine
Nausea
Vomiting
Progressing to bloody diarrhoea
Sepsis
Death results from intestinal
perforation or anthrax toxemia.
15. Laboratory Diagnosis
Specimens
Pustular exudates in malignant pustule
Sputum in pneumonic anthrax
Blood in bacteraemia
CSF in meningitis
Stool in intestinal anthrax (also in food poisoning by B.
cereus)
Stool specimen is emulsified and heated to 80o
C to kill non
spore forming microorganism
16. Morphology
Microscopical
Gram Stain
Spore Stain
Capsular Stain
Macroscopical
Cultural characteristics
Blood agar
Nutrient agar
Broth culture
Cont…
17. Cont…
Gram Stain
Gram positive bacilli
Found in chains
Capsulated in clinical
specimen (occasionally)
Sporulated outside the
host
Spore is central, oval
and non-bulging
Bacillus anthracis. Gram stain. 1500X. The cells have
characteristic squared ends. The endospores are
ellipsoidal shaped and located centrally in the
sporangium. The spores are highly refractile to light
and resistant to staining.
18. Cont…
Spore Stain
Spores are oval and central
Different techniques can b used to visualize spores
A. Methylene blue Staining, B. Malachite Green, & Safranin Staining, C. Indian ink Staining (Negative
Staining), D. Fluorescent Antibody Staining.
A B C D
19. Cont…
Culture characteristics
Aerobes
Optimum temperature for growth 35 to 37 ˚C
Spore formation best at 25 to 30˚C
Culture media used
Blood agar
Nutrient agar
Broth culture
20. Cont…
Blood agar
Large
2 to 5 mm in diameter
Grey-white in color
Irregular
Hemolytic except B. anthracis
Wavy edges
Ground glass appearance
Colonies of Bacillus cereus on the left; colonies of Bacillus anthracis on
the right. B. cereus colonies are larger, more mucoid, and this strain
exhibits a slight zone of hemolysis on blood agar
21. Cont…
Nutrient Agar
Can be used to check the
encapsulation of the
bacteria
0.7%sodium bicarbonate is
added in it.
Carbon dioxide rich
environment is provided
Colonies are large, smooth
and mucoid
Mucoid colonies of Bacillus anthracis. The culture was
probably incubated at an increased CO2 tension (5% CO2)
which greatly enhances production of the poly-D-glutamyl
capsule and accounts for the mucoid colony type
22. Cont…
Biochemical Test
Catalase Test
All bacilli are catalase positive.
Nitrate Reduction Test
Reduces nitrate to nitrite.
Seroogical Tests
ELISA to measure antibodies against EF and LF
Diagnostic titre: greater than 1:32
ELISA for anti-capsular antibodies
All Bacillus species are catalase positive
23. Anthrax and Biological Warfare
The inhalation of anthrax spores can lead to
infection and disease. The possibility of creating
aerosols containing anthrax spores has made B.
anthracis a chosen weapon of bioterrorism.
24. Bacillus cereus
Saprophyte
Causes Two Types of food poisoning
Emetic form or short incubation
It is caused by heat stable enterotoxin
Nausea, vomiting and abdominal cramps
Incubation period of 1-6 hrs
Diarrheal form or long incubation
It is caused by heat labile enterotoxin
Abdominal cramps and diarrhea
Incubation period of 8-16 hrs
In either type, the illness usually lasts < 24 hrs after onset
26. Corynebacterium diphtheriae
C. diphtheriae is found on the skin, and in the nose,
throat, and nasopharynx of carriers and patients with
diphtheria
Transmission: By respiratory droplets
Pathogenicity: Diphtheria is caused by the local and
systemic effects of a single exotoxin that inhibits
eukaryotic protein synthesis
This toxin inactivates eukaryotic polypeptide chain
elongation factor EF-2 by ADP-ribosylation, thus
terminatingprotein synthesis
27. Corynebacterium diphtheriae
Disease: Diphtheria
Clinical Manifestation: This life-threatening disease
begins as a local infection, usually of the throat
The infection produces a distinctive thick, grayish,
adherent exudate (called a pseudomembrane) that is
composed of cell debris from the mucosa, and
inflammatory products
The exudate coats the throat and may extend into
the nasal passages or respiratory tract where it
sometimes obstructs the airways, leading to
suffocation
28. Corynebacterium diphtheriae
Generalized symptoms are due to dissemination
of the toxin
Although all human cells are sensitive to
diphtheria toxin, major clinical effects involve the
heart (myocarditis may lead to congestive heart
failure and permanent heart damage) and
peripheral nerves