Anthrax

ANTHRAX The anthrax bacillus, Bacillus anthracis, was the first bacterium shown to be the cause of a disease- Kochs Postulate

In 1877, Robert Koch grew the organism in pure culture, demonstrated its ability to form endospores, and produced experimental anthrax by injecting it into animals.

Anthrax is a disease of domesticated and wild animals

Men suffer from anthrax occasionally due to close contact with infected animal or animal products

Bacillus anthracis Gram positive rods

Capsulated ( Protein) Capsule form in animal tissue and in special laboratory condition ( 5% CO2)

Forms endospore, centrally located, do not form in animal tissues

MacFadyean ( Polychrome methylene blue) stain blue bacilli with purple capsule

Aerobic/ Facultative anerobe

Robert Koch's original micrographs of the anthrax bacillus BImal K Das, Microbiology, AIIMS

Bacillus anthracis. Gram stain. 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. BImal K Das, Microbiology, AIIMS

Epiedemiology Distribution worldwide

Not common in West. Common in Africa ( Zimbabwe), S.E. Asia, China, South America, Turkey, Pakistan, India

Human to human or animal to animal transmission is rare ( not contagious)

Grazing animals become infected through ingestion of spores in the soil ( Carcasses become the source)

Epidemic : A. Spread to contiguous geographic areas by infected animal B. Non contiguous geographic areas by - biting flies ( Zimbabwe)- Contaminated surface water poolBImal K Das, Microbiology, AIIMS

Pathogenesis Endospores (Abrasion, inhalation, ingestion)

Death Introduced

Septicemia Phagocytosed by Macrophages

10 7 to 10 8/ml Regional LNs Blood stream

Multiply in Lymphatics Germinate inside Macrophages

Release

Vegetative Forms

BImal K Das, Microbiology, AIIMS

Clinically three forms of Human anthrax occur

Cutaneous anthraxPulmonary anthraxIntestinal anthrax

Broadly can be classified into

Non Industrial/Agricultural ( Through infected animals):

Cutaneous anthrax Rarely intestinal anthrax

Industrial Anthrax ( Through animal products): Mostly through animal products( wools, hair, hides, bones) Likely to develop Cutaneous and pulmonary anthrax ( inhalation)BImal K Das, Microbiology, AIIMS

Cutaneous Anthrax

Mainly in professionals( Veterinarian, butcher, Zoo keeper

Spores infect skin- a characteristic gelatinous edema develops at the site (Papule- Vesicle-Malignant Pustule- Necrotic ulcer)

80-90% heal spontaneously ( 2-6wks)

0-20% progressive disease develop septicemia

95-99% of all human anthrax occur as cutaneous anthrax

Intestinal Anthrax

Due to in ingestion of infected carcasses

Mucosal lesion to the lymphatic system

Rare in developed countries

Extremely high mortality rate BImal K Das, Microbiology, AIIMS

PULMONARY ANTHRAX

Require very high infective dose ( > 10,000 spores)

Acquired through inhalation of spores ( Bioterrorism - aerosol)

Present with symptoms of severe respiratory infection( High fever & Chest pain)

Haemorrhagic mediastinitis

Progress to septicemia very rapidly

10 7 to 10 9 bacilli/ ml of blood at the time of death

Mortality rate is very high > 95%


Meningitis

Meningitis has been reported in association with cutaneous, inhalation, and gastrointestinal anthrax cases

About one-half of patients with inhalation anthrax will develop hemorrhagic meningitis

DIFFERENTIAL DIAGNOSIS OF ANTHRAX

CUTANEOUS ANTHRAX

Boils, Erysipelas, Cutaneous TB, Leprosy, Plague, Vaccinia, Rickettsial pox, tularemia

INTESTINAL ANTHRAX

Typhoid fever, Acute Gastroenteritis, Tularemia, Peritonitis, Peptic ulcer, Mechanical obstruction

PULMONARY ANTHRAX

Viral pneumonia, Mycoplasma. Psittacosis, Legionnaires disease, Q fever, Histoplasmosis, Coccidiodomycosis, Silicosis, Sarcoidosis

Meningeal Anthrax : Sometime manifest as meningitis

D/D : Bacterial meningitis Aseptic meningitisBImal K Das, Microbiology, AIIMS

VIRULENCE FACTORS

Anthrax Toxin Complex of proteins ( all the components thermolabile)A. Protective antigenB. Edema factorC. Lethal Factor

Protein capsule Poly D Glutamic acid capsule - Inhibits phagocytosis ( Unencapsulated strains nonpathogenic)


LABORATORY DIAGNOSISFew points to remember

Anthrax is not highly contagious Cutaneous anthrax is not lethal and is readily treated with common antibiotics ID for human pulmonary / intestinal infection is > 10,000 spores

SPECIMEN TO COLLECT ( HUMAN ANTHRAX)Disposable gloves, masks, overalls, boots, head gear and dust maskDisposable items Autoclave and incinerate

Cutaneous anthrax: Vesicular exudate swabs and capillary tube aspirate

Intestinal anthrax: - Stool sample - isolate guinea pig inoculation - Blood( venipuncture) smear examination for bacilli - Peritoneal fluid for culture - Paired sera for Ab


Pulmonary anthrax:

Specimens of blood obtained prior to antimicrobial therapy should be sent for routine culture and for polymerase chain reaction (PCR) testing at a Laboratory Response Network (LRN) laboratory

Pleural fluid, if present, for Gram stain, culture, and PCR

Cerebrospinal fluid, in patients with meningeal signs, for Gram stain, culture, and PCR

Acute and convalescent serum samples for serologic testing

Pleural and/or bronchial biopsies for immunohistochemistry, if other tests are negative

SAMPLES FROM ANIMAL

Sudden death of animal in areas where anthrax was reported earlier

Carcasses 1 or 2 day oldAspirate blood - MacFadyean stain for bacilliDirect demonstration by IFADirect plating on blood agar

Putrefying carcassesBlood, tissue and hideCulture on selective mediumSoil sample from the areas where the carcass as lying

Serological assay

ELISA: based on anthrax toxin ( PA, LF and EF) for routine confirmation and vaccine response)Molecular techniques ( Only in the referral laboratories):- RFLP- PCR FingerprintingAnimal Inoculation: Guinea pig and mice inoculation

Culture is confirmed by gamma phage lysis ( PlyG lysin enzyme- g phage)BImal K Das, Microbiology, AIIMS

TREATMENTAntibiotics should be given to unvaccinated individuals exposed to inhalation anthrax.

Penicillin, tetracyclines and fluoroquinolones are effective if administered before the onset of lymphatic spread or septicemia

Antibiotic treatment is effective in cutaneous anthrax

Inhalation anthrax can be effectively treated with antibiotics administered prior to lymphatic spread or septicemia

INITIAL THERAPYOPTIMAL THERAPY

AdultsCiproflox Penicillin G 4 mu iv qdsX60days( 400mg iv BDX60days)Doxycycline 100mg iv BDX60 days

Children Ciproflox20-30mg/kgbodywt ivX60daysPenicllin G 50,000 u/kg X 60 days

Alternatives Amox, Tetracycline, Chloramphenicol, Erythromycin, Streptomycin


Although initial therapy should be intravenous, patients may be switched to oral therapy once they are stable, usually after 14 to 21 days of intravenous therapy.

A total duration of treatment of 60 days (combination of intravenous and oral therapy) should be given

Vaccine against Anthrax

Killed bacilli and/or capsular antigens produce no significant immunity.

A nonencapsulated toxigenic strain (Sterne Strain) has been used effectively in livestock.

Vaccine for humans: ( avirulent and nonencapsulated) sublethal amounts of the toxin produced

Licensed in the U.S. is a preparation of the protective antigen (PA)

Dose: A. 3 doses subcutaneously at the interval of 2 wksB. Followed by three additional doses at 6,12 and 18 monthsC. Annual booster dose

Who are to be vaccinated

Professionals ( Veternarians, butcher, Zoo keeper, Wild life workers, Forest guards) Military personnels


Anthrax and Biological Warfare Countries > 10 countries in the worldClouds of spores of Anthrax bacilli aerosol ( war heads filled with anthrax spores) - Through dried spores in envelopsSeptember 9/11 WTO attackPostal workers affected Inhalation anthrax ( 40% mortality)US Columbia, Florida, New Jersey, N. YorkOther parts of the worldBImal K Das, Microbiology, AIIMS

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Anthrax