Anthrax Dr.T.V.Rao MD

Dr.T.V.Rao MD 1

~ 60 species; Gram-positive or Gram-variable bacilli Large (0.5 x 1.2 to 2.5 x 10 um)

Most are saprophytic contaminants or normal flora

Bacillus anthracis is most important member

Produce endospores

Aerobic or facultatively anaerobic

Bacillus spp. are ubiquitous Soil, water, and airborne dust

Thermophilic (< 75C) and psychrophilic (>5-8C)

Can flourish at extremes of acidity & alkalinity (pH 2 to

10)

General Characteristics of Bacillus

Dr.T.V.Rao MD 2

Anthrax From the Greek word anthrakos for coal

Caused by spores

Primarily a disease of domesticated & wild animals

Herbivores such as sheep, cows, horses, goats

Natural reservoir is soil

Does not depend on an animal reservoir making it hard to eradicate

Cannot be regularly cultivated from soils where there is an absence of endemic anthrax

Occurs sporadically throughout US

South Dakota, Arkansas, Texas, Louisiana, Mississippi, California recognized endemic areas

Dr.T.V.Rao MD 3

A Closer Look at Anthrax

Anthrax is a disease of cattle, goats, and sheep

caused by a bacterium, Bacillus anthracis. It is rare

for humans to be infected. Most infections that do

occur are localized to small cuts in the skin whose

edges turn black (hence the name anthracis,

after anthracite coal). The disease is deadly for

humans because B. anthracis produces lethal

toxins.

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Bacillus anthrax

Several landmarks

1st to Observe under Microscope

1st to communicable disease.

1st observe the spores ( Robert Koch )

1st to prepare for attenuated vaccine. ( Louis Pasteur)

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Dr.T.V.Rao MD

20,000-100,000 cases estimated globally/yearhttp://www.vetmed.lsu.edu/whocc/mp_world.htm

Dr.T.V.Rao MD

Animal Transmission

Most commonly infected by ingestion from

contaminated soil or contaminated feed or bone

meal

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AnthraxAnthraxAnthraxAnthrax An infectious,

Usually fatal disease

of warm-blooded

animals, especially of

cattle and sheep,

caused by the

bacterium Bacillus

anthracis.

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B. anthracisGram-positive, spore-forming, non-motile bacillus

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Anthrax Bacilli

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Dr.T.V.Rao MD

Bacillus anthracisGeneral characteristics

Bacillus anthracis

Large, Gram positive, non-motile

rod

Vegetative form

and spores

Nearly worldwide distribution

Over 1,200 strains

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Bacillus anthracis Gram + rod

Facultative anaerobe

1 - 1.2m in width x 3 - 5m in length

Belongs to the B. cereus family Thiamin growth requirement Glutamyl-polypeptide

capsule Nonmotile

Forms oval, centrally located endospores

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The Spore

Sporulation requires Poor nutrient conditions

Presence of oxygen

Spores Very resistant to extremes

Survive for decades

Taken up by host and germinate

Lethal dose 2,500 to 55,000 spores

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Endospore Oxygen required for sporulation

1 spore per cell

dehydrated cells

Highly resistant to heat, cold,

chemical disinfectants, dry periods

Protoplast carries the material for

future vegetative cell

Cortex provides heat and radiation

resistance

Spore wall provides protection from

chemicals & enzymes

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Gram Stain Morphologyof B. anthracis

Broad, gram-positive rod: 11.5 x 35

Oval, central to subterminal spores: 1 x 1.5 with no significant swelling of cell

Spores usually NOT present in clinical specimens unless exposed to atmospheric O2

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Mechanism of Infection

Anthrax spores enter body Germinate & multiple in

lymph nodes

PA, EF, LF excreted from bacteria

PA binds to TEM8.

EF and/or LF binds

Complex internalized by endocytosis

Acidification of endosome

LF or EF crosses into cytosol via PA mediated ion-conductive channels

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Cultural

characteristics

Aerobe, facultative anaerobe

Grows between 12 -45 c

2-3 mm colonies

Edge like matted hair

Medusa head appearance

Blood agar Hemolytic colonies

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Appearance of Anthrax

String of pearl

appearance with

Pencillin

Differentiates Anthrax

and Cereus

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SELECTIVE MEDIUM

PLET

Contain

1 polymyxins

2 Lysozyme

3 Ethylene dioxide

4 Tetra acetic acid

Contains EDTA

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Biochemical Reactions

Gelatin

Inverted fir

tree

appearance

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Biochemical

Reactions

Glucose, Maltose

and Sucrose

fermented with

acid but no gas

Catalase positive

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Sterilization of environments Floor

space/shed/vehicle

Preliminary disinfection using 10% formaldehyde; (1-1.5 It/ sq.m.) or 4%

Gluteraldehydes for at least 2 hours

Cleaning - by washing or scrubbing with hot water

Final disinfection by one of the following disinfectants applied for at least 2 hours.

10% formaldehyde

4% Gluteraldehydes

3% hydrogen peroxide or

1% per acetic acid

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Wool and Hair

By duckering process (five stages) i.e.

lmmersion in 0.25-0.3% soda liquor

Immersion in soap liquor;

Two immersions in 2% formaldehyde solution; and

Rinsing in water

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Antibiotics

Pencillin

Erythrocin

Tetracycline

Chloramphenicol

Occasional strains

resistant to penicillin

are encountered

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TransmittedTransmittedTransmittedTransmitted The disease can be

transmitted to humans through contact with contaminated animal substances, such as hair, feces, or hides, and is characterized by ulcerative skin lesions

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Criteria in Transmission

Skin: direct skin contact with spores; in nature, contact with infected animals or animal products (usually related to occupational exposure)

Respiratory tract: inhalation of aerosolized spores

GI: consumption of undercooked or raw meat products or dairy products from infected animals

NO person-to-person transmission of inhalation or GI anthrax

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Anthrax CycleAnthrax CycleAnthrax CycleAnthrax Cycle

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Pathogenesis

The infectious dose of B. anthracis in humans by any route is not precisely known.

Rely on primate data

Minimum infection dose of ~ 1,000-8,000 spores

LD50 of 8,000-10,000 spores for inhalation

Virulence depends on 2 factors

Capsule

3 toxins http://www.kvarkadabra.net/index.html?/biologija/teksti/biolosko_orozje.htm

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Anthrax:

Clinical Presentation

Cutaneous

Inhalational

Gastrointestinal

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Epidemiology

of Anthrax in

Animal and

Human Hosts

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Three forms of Anthrax

Cutaneous anthrax

Skin

Most common

Spores enter to skin through small lesions

Inhalation anthrax

Spores are inhaled

Gastrointestinal (GI) anthrax

Spores are ingested

Oral-pharyngeal and abdominal

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Dr.T.V.Rao MD

Cutaneous Anthrax

95% of all cases globally

Incubation: 2-3 days (up to 12 days)

Spores enter skin through open wound or abrasion

Papule progresses to black Escher

Severe edema

Fever and malaise

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Anthrax:Cutaneous

Begins as a papule, progresses through a vesicular stage to a depressed black necrotic ulcer (Escher)

Edema, redness, and/or necrosis without ulceration may occur

Form most commonly encountered in naturally occurring cases

Incubation period: 112 days Case-fatality:

Without antibiotic treatment20% With antibiotic treatment1%

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Anthrax:Inhalational

A brief prodromal resembling a viral-like

illness, characterized by myalgia, fatigue,

fever, with or without respiratory

symptoms, followed by hypoxia and

dyspnea, often with radiographic evidence

of mediastinal widening.

Meningitis in 50% of patients

Rhinorrhea (rare)

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Capsule Glycocalyx

Sticky, gelatinous polymer external to cell wall

pX02 plasmid

Made up of D-glutamic acid

Non-toxic on its own

Only encapsulated B. anthracisvirulent

Most important role during establishment of disease

Protects against phagocytosis & lysis during vegetative state

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Virulence Factors

1 Capsular polypeptide

Anthrax Toxin

Both are coded by separate plasmid

The capsular polypeptide aids virulence by

inhibiting phagocytosis, loss of plasmid loss of

virulence

How the live attenuated anthrax spore vaccine (