CORYNEBACTERIUM
Scientific classification
 Kingdom:Bacteria
Phylum:Actinobacteria
Class:Actinobacteria
Order:Actinomycetales
Family:Corynebacteriaceae
Genus:Corynebacterium
Species:C. diphtheriae
Corynebacterium
Introduction
 Corynebacterium diphtheriae is a
pathogenic bacterium that causes diphtheria.
 It is also known as the Klebs-Löffler bacillus,
because it was discovered in 1884 by German
bacteriologists Edwin Klebs (1834 – 1912)
and Friedrich Löffler (1852 – 1915).
Basic characteristic
 Corynebacteria belong in the family
Mycobacteriaceae and are part of the CMN
group (Corynebacteria, Mycobacteria and
Nocardia).
 The family Mycobacteriaceae are Grampositive, nonmotile, catalase-positive and
have a rod-like to filamentous morphology
(Corynebacteria are often pleomorphic).
 As a group, they produce characteristic long
chain fatty acids termed mycolic acids.
Pathogenic species
 C. diphtheriae is the etiologic agent of
diphtheria.
 These organisms colonize the mucus
membranes of the respiratory tract and
produce the enzyme neuraminidase which
splits N-acetylneuraminic acid (NAN) from
cell surfaces to produce pyruvate which acts
as a growth stimulant.
Lab diagnosis
 Gram stain is performed to show gram-positive,
highly pleomorphic organisms with no particular
arrangement (classically resembling Chinese
characters).
 Special stains like Alberts's stain and Ponder's
stain are used to demonstrate the
metachromatic granules formed in the polar
regions.
 Metachromacity is the phenomenon by which
different parts of an organism can get stained in
two or more different colours just by applying a
single dye.
Cont.
 The granules are called as polar granules, Babes
Ernst Granules, Volutin, etc.).
 An enrichment medium, such as Löffler's serum,
is used to preferentially grow C. diptheriae.
 After that, use a selective plate known as
tellurite agar, which allows all
Corynebacteria (including C. diphtheriae) to
reduce tellurite to metallic tellurium.
 The tellurite reduction
is colormetrically indicated by brown colonies for
most Cornyebacteria species or by a black halo
around the C. diphtheriae colonies.
Special test
 A low concentration of iron is required in the
medium for toxin production. At high iron
concentrations, iron molecules bind to an
aporepressor on the betabactiophage, which
carries the Tox gene. When bound to iron, the
aporepressor shuts down toxin production.
 Elek’s test for toxogenecity is used to
determine whether the organism is able to
produce the diphtheria toxin or not.
Antimicrobial sensitivity
 The bacterium is sensitive to the majority
of antibiotics, such as the
penicillins, ampicillin,
cephalosporins, quinolones,
chloramphenicol, tetracyclines,
cefuroxime and trimethoprim.
BACILLUS AND CLOSTRIDIUM
Bacillus
Bacillus sp.
Scientific classification
 Domain:Bacteria
Division:Firmicutes
Class:Bacilli
Order:Bacillales
Family:Bacillaceae
Genus:Bacillus
Basic Characteristics
 Bacillus is a genus of Gram-positive
 rod-shaped bacteria and a member of the
division Firmicutes. Bacillus species can be
obligate aerobes or facultative anaerobes,
and test positive for the enzyme catalase.[
Cont.
 Ubiquitous in nature, Bacillus includes
both free-living and pathogenic species.
 Under stressful environmental conditions, the
cells produce oval endospores that can stay
dormant for extended periods.
Nature application
 the source of a natural antibiotic
protein barnase (a ribonuclease),
 Alpha amylase used in starch hydrolysis,
 the proteasesubtilisin used with detergents,
 the BaMH1 restriction enzyme used in DNA
research.
Medically important
 B. anthracis, which causes anthrax,
 B. cereus, which causes a foodborne
illness similar to that of Staphylococcus.
Other species
 A third species, B. thuringiensis, is an
important insect pathogen, and is sometimes
used to control insect pests.
 B. subtilis, an important model organism. It is
also a notable food spoiler, causing ropiness
in bread and related food.
 B. coagulans is also important in food
spoilage.
Laboratory diagnosis
 Using mannitol salt agar
 Incubated for a day
 Rod shape
 Oval endospore at one end
 Cell wall composed of techoic acid
Clostridium
Scientific classification
 Domain:Bacteria
Phylum:Firmicutes
Class:Clostridia
Order:Clostridiales
Family:Clostridiaceae
Genus:Clostridium
Basic characteristics
 Gram positive
 Obligate anaerobe
 Producing endospore
 Rod-shaped
 Consists of around 100 sp.
 Free-living bacteria
Endospore in clostridium
Pathogenic species
 C. botulinum – causing botulism by producing
toxin in food/wound. Able to paralyse infant’s

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breathing muscles. Sometimes contain in honey
but for adult, it is safe because it poorly compete
with bacteria present in GI
C. difficile – overgrowth other bacteria in the gut
during antibiotic therapy n cause
pseudomembranous colitis
C. perfringens (C.welchii) – causing food poising
until gas gangrene. Contain in salt raising bread
C. tetani – causing tetanus in muscle
C. sordellii – causing death to women after
childbirth
Clostridium botulinum
Clostridium difficile
Toxin production
 Neurotoxin production is the unifying feature
of the species C. botulinum.
 Seven types of toxins have been identified
and allocated a letter (A-G).
 Most strains produce one type of neurotoxin
but strains producing multiple toxins have
been described.
 Example: C. botulinum producing B and F
toxin types have been isolated from human
botulism cases in New Mexico and California.
Interesting info..
 C. botulinum produces a potentially lethal
neurotoxin that is used in a diluted form in
the drug Botox, which is carefully injected to
nerves in the face, which prevents the
movement of the expressive muscles of the
forehead, to delay the wrinkling effect of
aging.
 It is also used to treat spasmodic torticollis
and provides relief for approximately 12 to 16
weeks
MYCOBACTERIUM TUBERCULOSIS
Scientific classification
 Kingdom:Bacteria
Phylum:Actinobacteria
Order:Actinomycetales
Suborder:Corynebacterineae
Family:Mycobacteriaceae
Genus:Mycobacterium
Species:M. tuberculosis
In cell
Introduction
 1st discovered by Robert Koch
 Causative agent for tuberculosis
 Acid-fast bacili
 Aerobic (strictly aerobe)
 Pathogen of the mammalian respiratory
system
 Have a waxy coating (mycolic acid)
Lab diagnosis
 Lowenstein-Jensen medium
 Flourescent microscopy
 Caseous granuloma
 Acid-fast staining
In culture
Cont.
 Best shown in Zielh-Neelsen staining (acid
fast stain)
 It doesn’t retain crystal violet stain because
lack of outer cell membrane
 M. tuberculosis divides every 15–20 hours,
which is extremely slow compared to other
bacteria, which tend to have division times
measured in minutes
Cont.
 It is a small bacillus that can withstand
weak disinfectants and can survive in a dry
state for weeks. Its unusual cell wall, rich
in lipids (e.g.,mycolic acid), is likely
responsible for this resistance and is a key
virulence factor.
 Macrophages unable to digest the bacteria
because of its unique cell wall
Strain variation
 Most of the different pathogenic strain
associate with the different geographic
regions
 Some of it are newly discover but some are
antibiotic-resistant
 However, the hyper virulent strains are under
M. tuberculosis
The end