This document provides information on the bacteria Bacillus. It discusses two main types of Bacillus - B. anthracis, which causes anthrax, and B. cereus, which can cause two types of food poisoning. For B. anthracis, it describes its morphology, culture characteristics, virulence factors including toxins, clinical manifestations of anthrax in humans and animals, and methods for laboratory diagnosis and treatment. It also provides historical context on the importance of B. anthracis. For B. cereus, it summarizes the two types of food poisoning it can cause and how they differ clinically.

1. BACILLUS

2. INTRODUCTION
• Gram positive spore forming bacilli belong to two genera:
1. Bacillus: They are obligate aerobes; having non bulging
spores.
2. Clostridium: They are obligate anaerobes with bulging
spores.
• Bacillus species are obligate aerobic gram positive spore
forming rods.
• B. anthracis and B. cereus are the only two pathogenic
species: other members are universal, present in soil, air,
water, dust and also frequently isolated as a contaminant.
• Bacillus species are generally motile (peritrichous
flagella) and non capsulated except anthrx bacillus, which
is non motile and capsulated.

3. BACILLUS ANTHRACIS
• Bacillus anthracis is the causative agent of an
important zoonotic disease called anthrax.
• It is also gained importance recently because of
its ability to be used as biological weapon.
MORPHOLOGY
• They are gram –positive, large rectangular rods
(3-10µm x 1-1.6µm) arrange in chains, non
motile and capsulated bearing non bulging oval
spores.
• The capsule is polypeptide in nature.

4. • Spore are never found in the animal body during
life but are formed in culture or in the soil.
• Sporulation occur under unfavourable conditions.
Robert Koch's original photomicrographs
of Bacillus anthracis.

5. • In culture , the bacilli are arranged end to end in
long chains.
• The ends of the bacilli are truncated concave and
somewhat swollen so that a chain of bacilli presents
in bamboo- stick appearance.
Gram stain of Bacillus anthracis

6. HISTORICAL IMPORTANCE
Considerable historical interest is attached to anthrax
bacillus due to following reasons:
• It was the first bacteria seen under the microscope.
• Anthrax was the first communicable disease shown
to be transmitted by inoculation of infected blood.
• It was the first bacterium isolated in pure culture.
• Anthrax vaccine was the first attenuated bacterial
vaccine .

7. CULTURE
• B.anthracis is an aerobes and facultative
anaerobes.
• Temp: 12-450C
• Nutrient agar:
• Colonies are round ,2-3mm in diameter, raised,
opeque and greyish white.
• Under low power of the microscope , the edge of
the colony is found to be composed of long,
interlacing chain of bacilli resembling lock of
matted hair,so called the medusa head appearance.

8. Medusa head appearance of colony

9. Blood agar media:
• The colonies are non haemolytic, occasional
strains produce a narrow zone of haemolysis.
Gelatin stab culture:
• Gelatin is liquefied mostly at the top due to
aerobic environment and gives a charecterstics
inverted fir tree appearance.
INVERTED FIR TREE APPEARANCE

10. Selective medium:(PLET medium)
• Consisting of heart infusion agar with
polymyxin,lysozyme, ethylene diamine tetracetic
acid and thallous acetate.
• It is used for the isolation of B. anthrasis.
PLET MEDIUM showing growth of Anthrax bacilli

11. Solid medium with penicillin:
• Colonies have a string of pearl appearance look
(due to cells becoming larger and spherical
because of their weaker cell walls under the action
of penicillin, and cells tend to occur in chain on
surface of agar.)
BIOCHEMICAL REACTIONS
• Glucose, maltose and sucrose are fermented with
acid.
• Catalase positive
• Nitrate reduction test positive

12. RESISTANCE
• Vegetative forms are destroyed – 600C in 30min.
• Spore form – viable for years in soil
• Autoclaving – kills anthrax spores
• 4% KmNo4 in 15 mts - kills anthrax spores
• Susceptible to many antibiotics like pencillin etc.,

13. VIRULENCE FACTOR
• Pathogenesis of anthrax due to two important
virulence factor-
Antigen- These are three type:
• Capsular antigen: it is present in virulent strain
and consist of polypeptide and act as hapten.
• Cell wall antigen: polysaccharide
• Somatic protein antigen: it is heat labile protein
present in bacterial body. It stimulate the immune
system to produces the antibody which is
protective in nature.

14. ANTHRAX TOXIN
It is tripartite toxin, consisting of three fragments.
1. Edema factor:
• is the active fragments; act as adenyl cyclase and
increases host cell cAMP.
• It is responsible for edema and other menifestation seen
in anthrax.
2.Protective factor:
• is the binding fragment that binds to the host cell
receptors and facilitates the entry of other fragments
into the host cells.
3.Lethal factor:
• causes cell death, but mechanism of action is not
known.

15. • These fragments are not toxic individually, but in
combination , they produce local edema and
generalized shock.
• Toxin synthesis is controlled by a plasmid
(pX01).
• Loss of plasmid makes the strain avirulent.

16. CLINICAL MANIFESTATION
Animal anthrax:
• Anthrax is primarily a zoonotic disease.
• Herbivorous animal such as cattle, sheep and less
often horses and pig are affected more commonly.
• Infection occurs in susceptible animals by ingestion
of the spore present in the soil.
• Anthrax in animal is presented as a fetal spticemia.
• Infected animal discharge large number of bacilli
from the mouth, nose and rectum. These bacilli
sporulate in soil and remain as the source of
infection for man.

17. Human anthrax:
Transmission:
• Cutaneous mode- by spore entering through the
abraded skin.
• Inhalation of spore
• Inhalation of carcasses of animals drying of
anthrax containing spores (manifested as bloody
diarrhoea)
• Indirectly through fomite (very rare)

18. Clinical types:
There are three types of human anthrax:
1.Cutaneous anthrax (most common)
2.Pulmonary anthrax (less common)
3.Intestinal anthrax (very rare)

19. 1.Cutaneous anthrax:
• Spores enter through abraded skin
• Germinate & Multiply at the site of entry.
• Localised lesions - Face, neck & hand.
• Papule – vesicle – pustular – centrally necrosed –
black coloration.

21. PULMONARYANTHRAX
• Inhalation of the dust or filaments of wool from
infected animals, particularly in wool factories (
wool sorter’s disease)
• Hemorrhagic pneumonia
• Bacilli spread by lymphatics or blood, leading to-
• Bacteremia
• Meningitis

22. Intestinal anthrax
• Consumption of improperly cooked infected meat.
• Causes violent enteritis with bloody diarrhoea.
• All clinical conditions lead to septicaemic
anthrax if not treated early – Highly fatal!!!

23. Epidemiology of Human anthrax
• Human anthrax is highest in Africa, and central
and southern Asia. Human anthrax cases may be
of two types-
1. Non industrial cases: it is result from agricultural
exposure to animal.
2.Industrial cases: it result from infected animal
products such as hides, bristles and wool.

24. LABORATORY DIAGNOSIS
Specimen collection-
• Pus or swab from pustule
• Sputum in pulmonary anthrax
• Blood in case of septicemia
• CSF in hemorrhagic meningitis
• Gastric aspirate, feces or food in intestinal anthrax
• Ear lobe from dead animals

25. Direct demonstration:
Gram staining- gram positive rectangular bacilli.
McFadyean’s reaction- polypeptide casule can be
demonstrated by staining with Gurr’s polychrome
methylene blue stain for 30 sec.
• Shows amorphous purple capsule surrounding blue
bacilli.
McFadyaen’s reactionGram stain

26. Direct immunofluorescence test – it detect
capsular and cell wall polypeptide antigens by
using fluorescent tagged monoclonal antibodies.
Ascoli’s thermopreciitation test:
• It is a ring precipitation test, done when the
sample is putrid form and bacilli are likely to be
non viable.
• Tissues sample grounded in saline , boiled and
filtered.
• This antigenic extract is layered over the anthrax
antiserum on a narrow capillary tube.
• A ring of precipitate appears at the junction of
two liquids within 5min.

27. Culture
• Nutrient agar: medusa head appearance colony
• Blood agar: dry wrinkled, non haemolytic colony
• Gelatin stab agar: Inverted fir tree appearance
colony
Selective media-
• Solid medium with penicillin: string of pearl
colony
• PLET medium: inhibit the growth of contaminant

28. Culture smear:
• Reveals bamboo stick appearance,i.e. long chain
bacilli with non bulging spore.
Spores: they can be demonstrated by using special
stain, such as hot malachite green or 0.25%
sulphuric acid (spores are acid fast).
Serology:
• Antibodies appear in convalescent sera and can be
detected by ELISA or immunodiffusion in gel
method.
• Molecular diagnosis: PCR with specific primer
can be used for further cnfirmation.

29. Treatment:
• Pencillin
• Erythromycin
• Antitoxins – in emergency cases
Prophylaxis:
ANIMAL VACCINE –
• Sterne vaccine
HUMAN VACCINE –
• Alum Precipitated Toxoid –
• 3 doses intramuscularly at intervals of 6 weeks
and 6 months
• Booster dose after one year.

30. Bacillus cereus

31. Introduction:
• It is normal habitant of soil, also widely isolated
from food items such as vegetable, milk, cereals,
spices, meat, and poultry.
• It is an important agent of food poisoning in man.

32. Clinical manifestations:
Food poisoning:
• It produces two type of toxin diarrhoeal toxin
(causes diarrheal type of food poisoning) and
emetic toxin (causes emetic type of food
poisoning).

33. Bacillus cereus Diarrheal type Emetic type
Incubation period 8-16 hours 1-5 hours
Toxin Secreted in intestine
(similar to clostridium
perfringens
enterotoxin)
Preformed
toxin(formed in diet,
similar S. aureus)
Heat Heat labile Heat stable
Food items
contaminated
Meat, vegetables, dried
beans, cereal
Rice (chinese fried
rice)
Clinical features Diarrhea , fever ,
abdominal cramps
Vomiting , abdominal
cramps
Serotype involve 2,6,8,9,10,12 1,3,5
Differences between diarrheal type and emetic type of food poisoning

34. Emetic toxin:
• It is heat stable preformed toxin resembling
S.aureus enterotoxin.
• It act immediately on intestine so that the
incubation period of food poisoning is shorts (1-6
hrs).
Diarrheal toxin:
• Organism secretes this toxin only after entering
into the intestine, hence the incubation period is
longer (8-16 hrs.).

35. Ocular disease:
• It causes severe keratitis and panopthalmitis
following trauma to the eye that may lead to the
loss of vision.
Other condition:
• It rarely causes systemic infections including
endocarditis, meningitis, osteomyelitis and
pneumonia.

36. Laboratory diagnosis:
• Bacillus cereus can be isolated from feces by
using selective media such as:
• MYPA (mannitol, egg yolk, phenol red and agar)
• PEMBA(polymyxin B, egg yolk, mannitol,
bromothymol blue, agar).
• It is motile, non-capsulated and not susceptible to
gamma phage.

37. Treatment:
• Disease is mild and self limiting, requiring no
specific treatment.
• But bacillus cereus is susceptible to clindamycin,
erythromycin, vancomycin, aminoglycosides and
tetracycline.
• It is resistant to penicillin and trimethoprime.
Control:
• Adequate food hygiene is to be maintained while
storing cooked food especially rice and reheating
should be rapid.

38. Thank
you