Bacillus and Corynebacterium

Bacillus and Corynebacterium
Aman Ullah
B.Sc. MLT
M. Phil Microbiology
Master in Health Research
Certificate in Health Professional Education

Background
Gram-positive bacilli
Aerobic Anaerobic
Non spore forming Spore forming Spore forming
Corynebacterium
Listeria Bacillus Clostridium

Cont…
Bacillus
Pathogenic
Non-pathogenic
(Anthracoids)
B. anthracis B. cereus
e.g. B. subtilis

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

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.

Bacillus anthracis
 1st
disease-causing
bacterium discovered
 1877 by Robert Koch
 Causative agent of
Anthrax

Transmission
 Acute infectious disease in
human & animal
 Occupational disease
 Direct person-to-person
spread is rare

Virulence Factors
 Poly D-glutamyl capsule
 Antiphagocytic
 Anthrax toxin
 Mediates the toxigenic
stage
 Edema Factor (EF)
 Protective Antigen (PA)
 Lethal Factor (LF)

Types of Anthrax
 Cutaneous Anthrax (Malignant Pustule)
 Direct contact of spores with injured skin
 Pneumonic Anthrax (Woolsorters disease)
 Inhalation of spore-containing dust
 Intestinal Anthrax
 Eating meat of infected animals
 Anthrax Meningitis
 Complication of anyone of the above conditions

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

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

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.

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

 Morphology
 Microscopical
 Gram Stain
 Spore Stain
 Capsular Stain
 Macroscopical
 Cultural characteristics
 Blood agar
 Nutrient agar
 Broth culture
Cont…

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.

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

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

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

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

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

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.

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

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

 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

 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

Questions/Suggestions
khurramthalwi@hotmail.com

Bacillus and Corynebacterium

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