7. coryne bacterium
- 2. morphology • Corynebacteria are Gram-positive, catalase positive, non-spore-forming, non-motile, rod- shaped bacteria that are straight or slightly curved. • Their size falls between 2-6 micrometers in length and 0.5 micrometers in diameter.
- 3. • The shape has been described as the form of a "V", "palisades", or "Chinese letters".
- 5. CULTURAL CHARACTERISTICS • They are aerobic, facultative anaerobic growing best in 37 degree C and PH of 7.2. • They grow best in medias with blood , egg , or serum.
- 6. Blood tellurite medium • Resistant to tellurite (some strains may be inhibited); many other coryneforms may also grow on media with tellurite and produce black colonies (tellurite reduction). • This media will reduce the growth of other organisms. • Also known as pottasium tellurite 0.04% media
- 7. Serum broth • After 24 hrs of incubation, it shows turbidity and pellicle formation
- 8. Loeffler’s slope/ Loeffler’s inspisated serum medium • The organism shows abundant growth after 6- 8 hrs • The formed colonies will be small, circular, moist, creamy and glistening with irregular edges.
- 9. pathogenesis • Corynebacterium diphtheriae is the etiological agent of diphtheria, an upper respiratory disease mainly affecting children. • Diphtheria is described as "an upper respiratory tract illness characterized by sore throat, low-grade fever, and an adherent membrane of the tonsil(s), pharynx, and/or nose,"
- 10. Local effect • C. diphtheriae usually colonize in the upper respiratory tract, where the toxin secreted by the bacteria causes necrotic injury to epithelial cells. • As a result, blood plasma leaks into the area and forms a fibrin network called a pseudomembrane, which is full of rapidly growing C. diphtheriae cells.
- 11. • The pseudo membrane may extend to the larynx and may cause laryngeal obstruction, asphyxia and death.
- 12. Systemic or general effect • At the site of the lesion the diphtheria toxin is entered throughout the blood via lymph channels. • Most commonly affected areas include heart, muscle, peripheral nerves, adrenal glands, kidneys, liver, and spleen.
- 13. Laboratory diagnosis • The main study is bacteriological study • -it includes »Microscopic examination »Culture studies »Biochemical studies
- 14. MICROSCOPIC EXAMINATION • The smears made from the specimen are stained by ALBERT’S STAIN . • Metachromatic granules are appeared in the form of beads on slender rods.
- 16. culture • The swabs will treated in loeffler’s serum slope, blood tellurite medium and blood agar medium. • In loeffler’s serum slope medium after 6-8 hrs of incubation small circular colonies will appear.
- 17. • In blood tellurite medium and blood agar medium, the colonies will be formed after 36- 48 hrs.
- 18. Biochemical tests • 1. SUGAR FERMENTATION TEST: PRODUCTION OF ACID ONLY • 2. CATALASE TEST: POSITIVE • 3. OXIDASE TEST: NEGATIVE • 4. GELATIN LIQUEFACTION TEST: NEGATIVE • 5. UREA HYDROLYSIS: NEGATIVE
- 19. TOXIGENICITY TEST • There are two types of tests, • 1. in vivo tests » Subcutaneous test » Intra dermal test • 2. in vitro tests » Eleks gel precipitation test
- 20. Subcutaneous test • In this test the colonies of loefflers slope or pottasium tellurite 0.04% medium is mixed with 2-5 ml broth and injected 0.8 ml of emulsion s/c to the left leg of two guinea pigs. • Among this one guinea pig is protected with 500 units of diphtheria anti-serum before 18- 24 hrs. • Then the both animals are observed upto 96 hrs
- 21. • The unprotected animal will die within 2-3 days and the protected animal will remains healthy.
- 22. Intradermal test • In this test the colonies of loefflers slope or pottasium tellurite 0.04% medium is mixed with 2-5 ml broth and injected 0.1 ml of emulsion i/d to the two guinea pigs. • Among this one guinea pig is protected with 500 units of diphtheria anti-serum before ( 24 hr before) test (control animal) and the other one is injected with 50 units of diphtheria anti-serum intra peritoneally after 4 hrs of skin test.
- 23. • The unprotected animal will develop local erythematous lesion at the site of injection in 18-72 hrs, but no changes will occur in the control animal.
- 24. ELEKS GEL PRECIPITATION TEST • Mix a tube of melted nutrient agar with 2 ml of sterile horse serum. • Rotate the tube to mix the serum and agar. Do not shake the tube. • Pour the mixture into a sterile Petri dish. • Using lightly flamed forceps, lay the strip of anti-toxin impregnated filter paper across the centre of the Petri dish allowing it to sink beneath the agar surface.
- 25. • Allow the agar to set, then lift one corner of the lid and let the plate dry for 30-45 min in the incubator. • When dry inoculate with a toxinogenic strain of diphtheriae by streaking a single line of inoculums across the plate and paper strip at right angles to the strip.
- 27. Treatment • Penicillin and erythromycin are effective against c.diphtheria
- 28. • VACCINE »DPT VACCINE( diphtheria, tetanus, pertusis vaccine) is giving in the age of 6 weeks, 14 weeks, and 16-24 months.