Gram-positive spores and toxin-producing anaerobic bacillus
Motility present except in
C. tetani type VI
Capsule present in
Capsulated non-motile organisms which produce oval spores present sub-terminally
Stormy fermentation on litmus milk media
Litmus milk media (differential media)contains-
Skimmed milk(W/o Fat) containing sugar(Lactose) & protein (casein-milk protein)
C. perfringens show stormy fermentation in litmus milk medium. Lactose in the medium is fermented to organic acid and gas by the organism. Acid changes the color of the indicator litmus from blue to red. Acid coagulates casein (milk protein) in the medium to form a clot. Due to the vigorous production of gas, the clot gets disrupted. The paraffin seal is pushed upwards and shreds of the clot can be seen on the sides of the test tube. This type of fermentation is called stormy fermentation.
Shows target/double zone hemolysis–θ causes complete/alpha hemolysis and α cause incomplete/beta-hemolysis on blood agar
Major- α,β, I,ε
There are 5 types of perfringens-A, B, C, D, E
Most important virulence factor is – alpha toxin/phospholipase c/lecithinase- causes intravascular hemolysis
Present in the gut as commensals which is indicated by part/remote fecal pollution of water.
Gas gangrene/clostridial myonecrosis-In case of a very severe soiled dirty wound where blood vessels are damaged, spores of the organism can enter our body (spores in soil). These spores give rise to bacteria which releases various toxins(most importantly alpha toxin)into circulation leading to a rapid spread of edematous myonecrosis(gas gangrene). The sample to be collected-necrotic tissue and exudates from the wound
Mainstay- Surgical debridement
Poisoning-by C. perfringens type A
Intakes of food like meat and meat products
Caused due to heat labile enterotoxin
Incubation period-8-16 hrs
Detected by Nagler’s RXN-
Terminal bulging round spores having Drum stick appearance
On Robertson cooked meat broth, it turns meat particle black with foul odor due to its proteolytic activity
Swarming growth can be seen on Blood agar with polymyxin B plate
Virulence factors(2 exotoxins)
Tetanospasmin-It is an exotoxin that acts presynaptically on neuromuscular junction and prevents the release of inhibitory neurotransmitters like GABA and glycine. This causes descending spastic paralysis seen in tetanus.
Tetanolysin-heat and oxygen labile hemolysin which plays no role in the pathogenesis of Tetanus.
Diagnosis-Based on clinical symptoms. Culture can be done to support the diagnosis.
Prophylaxis-administration of tetanus toxoid (TT).It is present in 2 forms
Monovalent vaccine-toxoid is prepared by incubating toxin with formalin
-immunization against Diptheria, Pertussis, and Tetanus. Pertussis component act as adjuvant and inc. antigenicity of DT and TT. Various forms are –
DPT -DT+TT+Pertussis(whole cell)
DPaT- DT+TT+ Pertussis(acellular)
dT-It contains TT and adult dose diphtheria toxoid (2Lf) -3 doses(0,1M,1Yr) given to children above 12 yrs.
-Schedule-5 doses- Out of 5,3 doses at 6,10,14 weeks after birth and 2 booster dose at 16-24 months and 5yrs
-Site-IM at Ant-Lat aspect of the thigh
-protective titer-antitoxin titer of 0.01unit/mL
Produces 7 toxins-A,B,C1,CR,D,E,F
Botulism toxin is the most toxic to humankind with a minimum lethal dose of -1micro gram
Out of 7, six toxins A, B, C1, D, E, F are neurotoxins and cause botulism and CR is cytotoxic(acts by ADP-ribosylation)
Most common toxins which cause human disease are A, B & E
Botulinum toxin acts pre-synaptically at Neuro-Muscular junction and prevents the release of Acetylcholine leading to descending flaccid paralysis
The toxin has parasympathetic activity
Clinical features include
There are 3 types of botulism
Most common type
Due to the intake of canned food
Due to the intake of honey contaminated by spores
Due to contamination of the wound with spores of bacteria
During canning, spores enter the food and germinate in the anaerobic environment of the sealed container.
These bacteria then release the toxins
Spores germinate in an alkaline environment of the intestine into bacteria which then produces toxins.
C/F listed above
Baby stops sucking milk and
keeps falling over(k/a Floppy baby syndrome)
C/F listed above except GIT features
Present in the gut of 3% of normal people
The most common cause of nosocomial diarrhea
Antibiotic-associated colitis /Diarrhea-Intake of antibiotics kill the gut flora except for C. difficult. With no commensals left to inhibit the growth of C. Difficle, these grow rapidly and then produce toxins. Clindamycin has the highest chance to produce this disease
Pseudomembranous enterocolitis-with yellow plaque of size ranging from 1-2mm. Soon, it spreads over the entire colonic surface.
Types of toxin
Both toxins are needed to cause disease
Colonoscopy shows yellowish-white plaque in colon
ELISA(to demonstrate toxin)
PCR(to detect genes producing toxins)
Drug of choice is Metronidazole
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