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Spore forming bacteria - bacillus and clostridia

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Information about Spore forming bacteria - bacillus and clostridia
Health & Medicine

Published on March 4, 2014

Author: aashuvj1234

Source: slideshare.net

Description

This is a series of lectures on microbiology, useful for undergraduate medical and paramedical students
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Spore forming bacteria Dr. Ashish Jawarkar M.D.

Types • Aerobic – Bacillus • Anaerobic – clostridia Bacillus – two major species B. Anthracis – causes Anthrax B. Cereus – food poisoning

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

Morphology • • • • 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 fadyean’s reaction • Amorphous purplish material around bacilli • Represent capsular material

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

Growth charcteristics • 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 glass

Medusa head

String of pearls

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

Resistance • 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

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

Pathogenicity and virulence • Capsule – helps to escape phagocytosis • Toxin – leads to anthrax

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

Epidemiology • Seen in animal handlers – those who carry skin/hides on back • Hide porter disease

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

Anthrax • Agent for bioterrorism

• Active outbreak in India – in sheep – near Tamilnadu-Andhrapradesh border • Causes cutaneous infections and meningitis

Anthrax • Usually an occupational disease – contact with infected animals • Types – cutaneous, pulmonary, intestinal

Cutaneous anthrax

• Lesion called malignant pustule • Central area is black due to necrosis – eschar • Resolves spontaneously

Pulmonary anthrax • Hemmorhagic pneumonia • Hemmorhagic meningitis • Seen in people engaged in sorting wool – wool sorters disease

Intestinal anthrax • Seen in communities that eat dead animals • Bloody diarrhoea

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

Lab diagnosis • Sample – Skin – biopsy/materia – Sputum – Stool • Gram stain • Culture • Special test – direct fluoroscent antibody test • PCR

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

B. 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

Clostridia • Gram positive, spore forming • Anaerobic – Cl – Cl – Cl – Cl perfringens – gas gangrene tetani – tetanus botulinum – food poisoning difficile – acute colitis

• Clostridia – kloster - spindle

Gas 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 features • Increasing pain, edema and tenderness of the affected limb • Accumulation of gas

Lab diagnosis • Sample – muscle fragments or necrotic debris • Plated on appropriate culture media

Tetanus • 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 tetanus • Generalized tetanus

Local tetanus

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

Neonatal 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

Treatment • Human tetanus immunoglobulin – can neutralize toxin

Prevention • DPT vaccine

Cl botulinum • Produces neurotoxin • Causes paralysis • Used in treating wrinkles

types • 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

Cl difficile • Antibiotic associated diarrhoea (clindamycin) • Disrupts normal flora • Psuedo membranous colitis

Pseudomembranous colitis

Pseudomonas

P. aeruginosa • 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

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