Bacillus anthrax ,a potent bioweapon

Post on 14-Dec-2014

179 Views

Category:

Education

4 Downloads

Preview:

Click to see full reader

DESCRIPTION

MEDICAL MICROBIOLOGY LECTURES

Transcript

BACILLUS

Sporogenous Bacilli

Aerobic Bacilli Anaerobic Clostridia

1.Bacillus anthracis 1. Cl.perfringens 2.Bacillus cereus 2. Cl. tetani 3. Anthracoid bacilli 3. Cl.botulinum

Bacillus anthracis

-First pathogenic bacteria to be observed under microscope-First bacilli to be isolated in pure culture-First bacilli in which spores were demonstrated -First bacterium used for preparation of attenuated vaccine-First bacterium to be shown cause of disease-First bacterium that evolved as a potent weapon in bioterrorism

OVERVIEWMorphologyCultural characteristicsBiochemical reactionsResistancePathogenicityLab diagnosisEpidemiologyProphylaxisTreatment

BIOTERRORISM

MORPHOLOGY-One of the largest pathogenic bactera;4-8x1-1.5 mm in size-Gram +ve, rod shaped, non-motile and non acid-fast-Bamboo stick appearance of long chains-Polypeptidal capsule-Central or sub terminal oval spores

CULTURAL CHARECTERISTICS-Aerobic ,Facultative anaerobic-On NA : Colonies are round, grayish white,irregular,raised with “frosted glass” appearance,2-3 mm in diameter.Medusa head /Barrister's wig appearance of colonies under low magnification-On BA: Non-hemolytic colonies-Gelatin stab culture: “Inverted fir tree" appearance-PLET medium: for selective isolation

BIOCHEMICAL REACTIONS-Glucose, Maltose, Sucrose fermented with ACID production -Nitrate reduction test-Gelatin liquefaction test All positive-Catalase test

RESISTANCE-Spores survive for many years(dry state & soil)

-Moist heat kills : -vegetative cells 60 0C x 30 min. -spores 1000C x 10 min. -4% FD & KMnO4 kills sporesDuckering: 2% formaldehyde at 30-40 0C for 20 min. disinfects wool & 0.25% at 60 0C for 6 hrs. for animal hair & bristles.

PATHOGENICITYVirulence factors:1.Capsular polypeptide – inhibits phagocytosis2.Anthrax toxin –a complex of 3 fractions:-Edema factor(OF or Factor I) whole complex

-Protective antigen factor(PA or Factor II) produces local edema

-Lethal factor(LF or Factor III) & generalized shock

Edema factor + protective antigen = Edema toxin Lethal factor + protective antigen = Lethal toxin

Clinically three forms of Human anthrax occur1.Cutaneous anthrax2.Pulmonary anthrax3.Intestinal 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

1.Cutaneous Anthrax(95-99% human anthrax)

•Mainly in professionals( Veterinarian, butcher, Zoo keepers, persons handling carcasses/hides/hair, loading skin on bare backs-hide porters disease .

• Spores infect skin- a characteristic gelatinous edema & congestion develops at the site (Papule- pustule-black ulcer(eschar) .Later a ring of vesicle containing serous fluid surrounds eschar termed as Malignant pustule.

•Face ,neck,arms and back are common sites

• 80-90% heal spontaneously ( 2-6wks)

• 10-20% progressive disease – develop fatal septicemia, death

Different locations & morphology of lesion in cutaneous anthrax

2.Pulmonar Anthrax- wool sorter's/Ragpicker’s disease:

-Acquired with inhalation of spores(bioterrorism-aerosol)-Requires very high infective dose(10,000 t0 20,000 spores)-Inflammatory reaction occurs in trachea, bronchi with hemorrhagic bronchospasm-Presents initially with non -specific symptoms but later with symptoms of severe respiratory infection & severe respiratory collapse-Hemorrhagic meningitis sometimes occurs as complication-Progress to septicemia very rapidly-Mortality rate is very high

3.Intestinal Anthrax

-Rare in man and is found in primitive communities eating dead carcasses of infected animal-Presents with serious severe enteritis, bloody or hemorrhagic diarrhoea,bloody vomit -Fatality rate is 25-60% depending upon treatment

EPIDEMIOLOGY(INDIA)

-Anthrax is enzootic in India

-An epizootic of anthrax in sheep active AP,TN borders-Largest live stock population in the world

-Pondicherry ( JIPMER) - 30 human cases reported ( Mostly Cutaneous, Septicemic or Meningeal)

-Vellore ( CMC)- 49 human cases

-Chittor ( Rajasthan)- 30 human cases

-Tirupati ( Andhrapradesh)- 25 human cases

-Midnapur ( WB)- 22 human cases

LABORATORY DIAGNOSISA. Hematological investigation-not significantB.Bacteriological investigation:Specimen- swabs, pus, pustules, blood ,sputum, feces etc.1.Microscopy:Gram staining & spore staining Characteristic Mc’ Fadyean’s reaction Immunofluorescent microscopy

2.Culture: Suitable culture media for selective isolation3.Animal inoculation : done in guinea pigs, mice & rabbits. 3.Serology(Ascoli’s thermoprecipitation test)4.Molecular methods : PCR with specific primers5.Molecular typing: MLVA & AFLL for epidemiological studies

PROPHYLAXISHumans protected by preventing disease in animals

-Veterinary supervision-Trade restrictions-Proper sterilization & disinfection of animal

products-Deep burial or cremation of carcasses Improved industry standards

Safety practices in laboratories Post-exposure antibiotic prophylaxis

VACCINATION:-Active immunization with Pasteur’s anthrax vaccine-Salvo immune serum in serious toxic cases-Cell free vaccine in high risk groups-Inactivated /killed vaccine for veterinarians & Agri-workers-Sterne vaccine used effectively in livestock's-Alum precipitated toxoid found safe in professionals 3 doses given intramuscularly

TREATMENTEffective antibiotics in humans:Sulphonamides,ciprofloxacin,penicillin,erythromycin,Vancomycin,doxycyline,chloramphenicolFDA -approved ciprofloxacin,doxycycline and penicillin

BIOTERRORISM-anthrax as a bioweapon

-Anthrax was used by Scandinavian rebels against Russians -Operation vegetarian by Royal Air Force against Germany in 1944 ,an anti-livestock operation-In 1997-accidental release of anthrax spores from biological weapons complex in Russia infected 94 people ,68 died-In Oct.2001 anthrax attacks in USA termed Amerithrax(FBI) 22 cases- 11 inhalation(5 deaths),11 cutaneous(no deaths)

Bacillus cereus-Important cause of food poisoning-Distributed widely in nature(soil, vegetables & foods)-Non-Capsulated but Motile (few non-motile strains )-Two patterns of food borne disease are produced:1.Diarrhoeal type: -caused by serotypes 2,6,8,9,10 & 12 -associated with wide range of foods -characterized by diarrhea & abdominal pain2.Emetic type(fried rice syndrome) caused by STs 1,3 & 5 - associated with consumption of cooked rice - characterized by acute nausea & vomitingFor isolation MYPA medium is used10,00000 bacilli/gram of stool is significant

ANTHRACOIS /PSEUDOANTHRAX-Saprophytic ,spore-forming, non-pathogenic species-They are most common laboratory contaminants (e.g. B.subtilis contaminating blood transfusion bottles-They are opportunistic & may cause septicemia

top related