spore forming bacteria - bacillus and clostridia

Spore forming bacteriaSpore forming bacteria

Dr. Dr. AshishAshish JawarkarJawarkar M.D.M.D.

TypesTypes• Aerobic – Bacillus• Anaerobic – clostridia

Bacillus – two major speciesB. Anthracis – causes AnthraxB. Cereus – food poisoning

B. B. AnthracisAnthracis• Morphology• Growth characteristics• Biochemical reactions• Resistance• Pathogenicity and virulence• Epidemiology• Diseases caused• Laboratory diagnosis• Treatment

MorphologyMorphology• Gram positive bacilli in chains• Bacilli have characteristic squared ends• Bamboo stick appearance• Entire chain surrounded by polypeptide

capsule• Spores donot stain by ordinary stain• They are central – donot cause bulging

Mc Mc fadyeanfadyean’’ss reactionreaction• Amorphous purplish material around

bacilli• Represent capsular material

• Morphology• Growth characteristics• Biochemical reactions• Resistance• Pathogenicity and virulence• Epidemiology• Diseases caused• Laboratory diagnosis• Treatment

Growth Growth charcteristicscharcteristics• Aerobe• On culture – raised, dull opaque, grayish

white colonies – frosted glass appearance

• Edge of colony is composed of interlacing chains of bacilli looking like matted hair –medusa head appearance

• When grown with Penicillin added – the cells become large, spherical and look like string of pearls

Frosted glassFrosted glass

Medusa headMedusa head

String of pearlsString of pearls

ResistanceResistance• Bacilli stay in bone marrow and skin

of dead animals for about a week• Normal heat fixation may not kill

bacteria in blood smears

• Spores are highly resistant to chemical and physical agents

• Found in soil after 60 years• Resistant to dry heat at 140 deg for

3 hours• Resistant to boiling for 10 min• They survive in 5% phenol for weeks

PathogenicityPathogenicity and virulenceand virulence• Capsule – helps to escape

phagocytosis• Toxin – leads to anthrax

EpidemiologyEpidemiology• Seen in animal handlers – those who

carry skin/hides on back • Hide porter disease

AnthraxAnthrax• Agent for bioterrorism

• Active outbreak in India – in sheep –near Tamilnadu-Andhrapradeshborder

• Causes cutaneous infections and meningitis

AnthraxAnthrax• Usually an occupational disease –

contact with infected animals• Types – cutaneous, pulmonary,

intestinal

CutaneousCutaneous anthraxanthrax

• Lesion called malignant pustule• Central area is black due to necrosis

– eschar• Resolves spontaneously

Pulmonary anthraxPulmonary anthrax• Hemmorhagic pneumonia• Hemmorhagic meningitis• Seen in people engaged in sorting

wool – wool sorters disease

Intestinal anthraxIntestinal anthrax• Seen in communities that eat dead

animals • Bloody diarrhoea

Lab diagnosisLab diagnosis• Sample

– Skin – biopsy/materia– Sputum– Stool

• Gram stain• Culture• Special test – direct fluoroscent antibody

test• PCR

B. CereusB. Cereus• Cause of food poisoning• Found in milk, cereals, spices, meat and

poultry• Two types of food poisoning

– Acute – chinese fried rice – vomitting in 1-5 hrs after meal

– Chronic – After 8 hrs of ingestion

• Illnesses are mild – require no treatment

ClostridiaClostridia• Gram positive, spore forming• Anaerobic

–Cl perfringens – gas gangrene–Cl tetani – tetanus–Cl botulinum – food poisoning–Cl difficile – acute colitis

• Clostridia – kloster - spindle

Gas gangreneGas gangrene• Caused by Cl perfringens type A• It is a rapidy spreading necrosis of

muscles• Usually seen after extensive muscle

damage (contaminated) secondary to trauma – road accidents, battle field injury

Clinical featuresClinical features• Increasing pain, edema and

tenderness of the affected limb• Accumulation of gas

Lab diagnosisLab diagnosis• Sample – muscle fragments or

necrotic debris• Plated on appropriate culture media

TetanusTetanus• Characterised by tonic muscular

spasms, commencing at site and slowly becoming generalised

• Disease follows injury too trivial to be noticed

• Due to tetanospasmin toxin produced by Cl tetani

Different forms of tetanusDifferent forms of tetanus• Generalized tetanus

Local tetanusLocal tetanus

Cephalic tetanusCephalic tetanus• After a head injury or local infection• Trismus – lock jaw

Neonatal tetanusNeonatal tetanus• Infection follows unhygeinic practices

after delivery• Applying cowdung on umbilical

stump

• Diagnosis is clinical – by the time symptoms appear, organism is no longer present in lesion

TreatmentTreatment• Human tetanus immunoglobulin –

can neutralize toxin

PreventionPrevention• DPT vaccine

ClCl botulinumbotulinum• Produces neurotoxin• Causes paralysis• Used in treating wrinkles

typestypes• Food borne botulism

– eating food with pre formed toxin– After 12 hrs of taking food– Vomitting, constipation, difficulty in swallowing,

speaking, breathing– Respiratory failure

• Wound botulism– No gi manifestations

• Infant botulism– Infants below 6 months– Honey is an agent– Poor feeding, pooling of oral secretions, loss of head

control

ClCl difficiledifficile• Antibiotic associated diarrhoea

(clindamycin)• Disrupts normal flora• Psuedo membranous colitis

PseudomembranousPseudomembranous colitiscolitis

PseudomonasPseudomonas

P. P. aeruginosaaeruginosa• Pseudo – false• Monas – mono – single unit• Slender gram negative bacillus with

polar flagellum

• Produces bluish green pigment –pyocyanin on culture

• Very resistant to common antiseptics and disinfectants like dettol

• Susceptible to glutaraldehyde and phenols

• Most common infection – otitis media• In hospitals – wound infection, bed

sores, UTI following catheterisation• Seen in equipments such as

respirators, endoscopes, bed pans, lotions, eye drops

spore forming bacteria - bacillus and clostridia

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