tetanus teaching basics

Clostridium tetaniteaching basics

Dr.T.V.Rao MD

05/01/23 Dr.T.V.Rao MD @ Rao's Microbiology 1

Clostridia: general characteristics

Genus Clostridium contains a large number of gram-positive, spore-forming species, several of which are able to produce disease in humans.Most species are obligate anaerobes, some will grow under microaerophilic conditions.Natural habitat: soil and the intestinal Tract


History• Tetanus was well known to ancient

people, who recognized the relationship between wounds and fatal muscle spasms. In 1884, Arthur Nicolaier isolated the strychnine-like toxin of tetanus from free-living, anaerobic soil bacteria.

• Rosenbach and Kitasato contributed05/01/23 Dr.T.V.Rao MD @ Rao's Microbiology 3

Clostridium tetani• Clostridium tetani is a rod-

shaped, anaerobic bacterium of the genus Clostridium.. C. tetani is found as spores in soil or as parasites in the gastrointestinal tract of animals. C. tetani produces a potent biological toxin, tetanospasmin, and is the causative agent of tetanus


Clostridium tetani• Clostridium tetani is

an anaerobic pathogenic bacterium that is primarily found in soil and animal intestinal tracts.

• Cotton, dust• Plaster of Paris• Catugut


Morphology• Gram + bacilli• 4-8 x 0.5 microns• Drumstick

appearance• Obligatory

anaerobe


Cultural characteristics'• Grows on blood agar with advancing

edges• In gelatin stab fir tree appearance• In Robertson cooked meat medium

produces turbidity gas• Meat is not digested turns black • First α hemolysis followed by β hemolysis


C. tetani: key characteristicsLarge, spore-forming, motile, obligate anaerobic bacillus (see below).Ferments: proteins or amino acids.Produces: acetic acid, fatty acids, NH3, CO2, H2, and a strong exotoxin.

Tetanospasmin, a powerful neurotoxin


Resistance of the Clostridium tetani

.Survives boiling upto 3 hours

• They can not survive autoclaving at 249.8 °F (121 °C) for 20 minutes.

• The spores are also relatively resistant to phenol and other chemical agents.


Biochemical reactions• Indole +• MR and VP test

negative• H2 S not produce• Nitrites are not

reduced• Gelatin liqification

occurs


Tetanus etiology• In necrotic and infected wounds,

anaerobic conditions will permit germination. Contaminated puncture wounds can be particularly dangerous, especially when a foreign body is present.


Mode of Transmission -

Tetanus• Mode of Transmission: Transmission is

primarily by contaminated wounds, Tissue injury( surgery, burns,deep puncture wounds, crush wounds, Otitis media ,dental infection, animal bites, abortion, and pregnancy

• Incubation Period: 8 DAYS ( 3-21 DAYS)


Type of Tetanus

• Traumatic tetanus• Puerperal tetanus• Otogenic tetanus• Idiopathic tetanus• Tetanus

Neonatroum


Tetanus – Toxin oriented disease

• C. tetani usually enters a host through a wound to the skin and then it replicates. Once an infection is established, C. tetani produces two exotoxins, tetanolysin and tetanospasmin.. The genes that produce toxin are encoded on a plasmid which is present in all toxigenic strains, and all strains that are capable of producing toxin produce identical toxin


Nature of Toxins• C. tetani produces two exotoxins,

tetanolysin and tetanospasmin. The function of tetanolysin is not known with certainty.

• Tetanospasmin is a neurotoxin and causes the clinical manifestations of tetanus.

• Tetanospasmin estimated Human lethal dose 2.5 ng/kg


Toxins• Hemolysin ( tetanolysin )• Neurotoxin ( Tetanospasmin )• Non spasmogenic toxin• Tetanolysin is heat labile and oxygen laible• Toxin is responsible for the Tetanus• Heat laible inactivated at 650c• Mol wt Heavy chain 93,000

Light chain 52,000 bound by disulphide bonds


Tetanospasmin• Mol wt Heavy chain 93,000

Light chain 52,000 bound by disulphide bonds

• Human – 130 nanograms• Horse and guinea pigs guinea

pigs rabbits effected


Tetanospasmin• Tetanospasmin is distributed in the

blood and lymphatic system of the host. The toxin acts at several sites within the central nervous system, including peripheral nerve terminals, the spinal cord, and brain, and within the sympathetic nervous system.


Tetanospasmin• The toxin is taken up into within the

nerve axon and transported across synaptic junctions, until it reaches the central nervous system, where it is rapidly fixed to gangliosides at the presynaptic junctions of inhibitory motor nerve ending


Pathogenicty• The spores germinate in

reduced oxygen potential devitalized tissues, presence of foreign bodies

• Motor neurons absorb• Spread Intraaxonally to

CNS• Avidly fixed to

gangliosides of gray matter


Mechanism of Action of Tetanus Toxin


Tetanospasmin• Resembles strychnine blocks synaptic

inhibition in the spinal cord• At inhibitory terminals that use glycine and

GABA as neurotransmitters• Toxin acts presynaptically unlike

styrchnine post synaptically• Muscle spasms of agonists and

antagonists


How Toxin acts• The toxin, by blocking the release of

inhibitors, keeps the involved muscles in a state of contraction and leads to spastic paralysis , a condition where opposing flexor and extensor muscles simultaneously contract. Death is usually from respiratory failure.


Clinical manifestations• The clinical manifestations of tetanus

are caused when tetanus toxin blocks inhibitory impulses, by interfering with the release of neurotransmitters, including glycine and gamma-aminobutyric acid. This leads to unopposed muscle contraction and spasm.


Tetanus• Involves somatic musculkar system• Injuries• Punctured wound• Surgery• Otitis media• Septic abortion• Cow dung applications• Ear boring circumcision• Incubation 2 days to weeks• Average 6 12 days


Opisthotonus


Photo Courtesy of U.S. Centers for Disease Control and Prevention05/01/23 Dr.T.V.Rao MD @ Rao's Microbiology 28

http://www.idph.state.il.us/about/vpcd.htm

Tetanus symptoms & signs• Characteristic

features are risus sardonicus (a rigid smile), trismus (commonly known as "lock-jaw"), and

opisthotonus (rigid, arched back).


Risus Sardonicus in Tetanus Patient


Laboratory Diagnosisof Tetanus


Laboratory Diagnosis• Clinical diagnosis most important

in management• Microscopy• Culture• Animal Inoculation• Microscopy not reliable05/01/23 Dr.T.V.Rao MD @ Rao's Microbiology 32

Culture• Done on Blood agar • One half of plate spreads to other half after 1 – 2

days of incubation anerobically• Three tubes of cooked meat broth inoculated • 1 tube 800c for 15 mt• 2 tube 800c for 5 mt• 3 tube unheated• All are incubated at 370c upto 4 days • Subcultured


Clostridium tetani Gram Stain

Round terminal spores give cells a “drumstick” or “tennis racket” appearance.05/01/23 Dr.T.V.Rao MD @ Rao's Microbiology 34

Showing spores and Grwoth on Blood Agar plate


Toxigenicty tests• In a plate of Blood divided into 2 halves first half

incorporated with 1500 / ml of antitoxin• Hemolysis without antitoxin• Bacteria grown in Robertson cooked meat

medium inoculated into tail of a mice• A 2nd animal injected with tetanus antitoxin 1000

units an hour earlier the test• Spasm of tail of un inoculated mice spread to

limb and other side and the animal dies


Tetanus bacteria grow in RCM Medium

• Bacteria grown in Robertson cooked meat medium


Treatment• Treatment involves debridement, the antibiotic

metronidazole* active immunization with tetanus toxoid , and passive immunization with tetanus immune globulin.

• Prevention is through active immunization with tetanus toxoid**. The toxoid stimulates the body to make neutralizing antibodies against the binding component of the tetanus toxin. Once the antibody binds to the toxin, the toxin can no longer bind to the receptors on the host cell membrane


PreventionTetanus carries a 35% mortality rate, making prevention very important! The best course is childhood immunizations, with consistent booster doses, and prompt cleaning of wounds with hydrogen peroxide.


Prophylaxis• Surgical attention• Antibiotics• Immunization• Antibiotics <4 hours • Erythromycin 5000 mg Bid• Pencillin• Local treatment with bacitracin, and

neomycin


Passive Immunization• Tetanus antitoxin 1,500 IU s/c IM• Test dose to be given• Human Anti tetanus globulin 250

units


Passive Immunization• Antitoxin (tetanus immune globulin) should be

administered immediately. This will inactivate toxins in the blood.

• Wounds should be debrided to remove dead tissue or foreign bodies.

• Antibiotics should be given to inhibit growth of C. tetani.• A tetanus toxoid booster immunization should be given

to patients who have not received one within the last 5 years.

• If spasms occur, antispasmodic drugs should be used and respiration maintained by a breathing apparatus if necessary.


• Tetanus toxoid was developed by Descombey in 1924,

• Tetanus toxoid immunizations were used extensively in the armed services during World War II.

• Although the rates of seroconversion are about equal,the adsorbed toxoid is preferred because the antitoxin response reaches higher titers and is longer lasting than that following the fluid toxoid.

TETANUS TOXOID


Tetanus toxoid

• Tetanus toxoid consists of a formaldehyde-treated toxin.

• There are two types of toxoid available —adsorbed (aluminum salt precipitated)toxoid and fluid toxoid


Active Immunization• 1st dose - 6th week• 2nd dose - 10th week• 3rd dose - 14th week• 1st booster - 18th month• 2nd booster - 6th year• 3rd booster - 10th year


Passive Immunization

1. ATS(equine) Ig- 1500 IU/s.c after sensitivity test

(or)2. ATS(human) Ig- 250-500 IU, no

anaphylactic shock, very safe and costly.


Treatment of Tetanus patients

• Hospitalization• Tracheotomy• Human TIG 10,000 IU• Pencillin, Metronidazole• ATS IV • Give active immunization.05/01/23 Dr.T.V.Rao MD @ Rao's Microbiology 47

PREVENTION OF NEONATAL TETANUS

• 2 doses of T.T to all pregnant women between 16 to 36 weeks of pregnancy with an interval of 1 to 2 months between the two doses.

• The first dose as early as possible & the second dose a month later preferably 3 weeks before delivery.

• If the pregnant woman is previously immunized, a booster dose is sufficient.

• If the pregnant woman is not immunized, then the new born should be protected against tetanus by giving tetanus human immunoglobulin 750 IU with in 6 hours of birth.


Triple Antigen vaccine• Triple Antigen vaccine

is a combination of Diphtheria, Tetanus, and Pertussis. The vaccine stimulates the production of antibodies to immunize the body against the causative agents of the three diseases listed above


Epidemiology • Endospores are found in most soils and in the

intestinal tract of many animals and humans.• Although exposure to endospores is common,

disease is uncommon except in countries with poor medical care and vaccination compliance.

• It is estimated that there is more than one million cases a year worldwide, with a mortality rate of 20% to 50%.

• Most deaths occur in neonates and originates from infection of umbilical stumps in mothers that have no immunity.


Prevention is Better than Cure


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