Aerobic Non-Spore Forming Gram-Positive Bacilli

Aerobic Non-Spore Forming Gram-Positive Bacilli

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Aerobic Non-Spore Forming Gram-Positive Bacilli

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1. Aerobic Non-Spore Forming Gram-Positive Bacilli Corynebacterium

3. Species of Corynebacteria

4. Corynebacterium spp Gram positive bacilli, with characteristic morphology (club shaped and beaded) Non motile Non spore forming Non capsulated Non-?-hemolytic on sheep blood agar Facultative anaerobic C. diphtheriae is fastidious while diphtheriods are non-fastidious Catalase positive Oxidase negative

5. ?Lipid-rich cell wall contains meso-diaminopimelic acid, arabino-galactan polymers, and short-chain mycolic acids ?Lysogenic bacteriophage encodes for potent exotoxin in virulent strains

8. Corynebacterium: Natural Habitats Many species normal commensals of the human skin (including C. amycolatum, C. jeikeium, C. urealyticum) C. jeikeium and C. amycolatum also present in the inanimate hospital environment

9. Corynebacterium: Modes of Infection Corynebacterium jeikeium, C. amycolatum, and C. urealyticum as skin flora can be introduced systemically from infected catheter wounds Corynebacterium urealyticum as an anterior urethral commensal can invade the urinary tract in debilitated patients

10. Corynebacterium: Types of Infectious Disease C. jeikeium, C. amycolatum, and C. urealyticum produce wound infection, bacteremia, and endocarditis in hospital patients. C. urealyticum is a urease producer that causes to deposition of ammonium magnesium phosphate crystals and damages bladder mucosa with ulceration and infection.

11. Corynebacterium: Types of Infectious Disease Toxigenic strains of C. diphtheriae lyso- genized by tox+ ?-prophage most often cause diphtheria. Occasional strains of C. ulcerans and C. pseudotuberculosis also produce toxin, but only C. ulcerans is associated with diphtheria-like illness. Tox? strains of C. diphtheriae cause pharyngitis and endocarditis.

13. Clinical Forms of Diphtheria Respiratory Acquired by droplet spray or hand to mouth contact Non-immunized individuals are susceptible Non-respiratory Systemic Skin and cutaneous forms

14. C. diphtheriae: Causative Agent of Diphtheria Respiratory disease?diphtheria Incubation period?2 to 5 days Symptoms: sore throat, fever, malaise Toxin is produced locally, usually in the pharynx or tonsils Toxin causes tissue necrosis, can be absorbed to produce systemic effects Forms a tough grey to white pseudomembrane which may cause suffocation

15. This may obstruct the ?airway ?and result ?in death caused by a lack of air or oxygen

16. Corynebacterium The more dangerous ?effects ?occur when the toxin becomes systemic and ?attacks the ?heart (heart failure), ?peripheral nerves (paralysis), and the adrenal glands (hypofunction). Cutaneous ?diphtheria? ?More ?common ?in?tropical and subtropical areas. Necrotic lesions with occasional formation of a local pseudomembrane occur. Antibiotic susceptibility and treatment Antiserum ? once the toxin has bound, however, the antiserum ?against it is ineffective. Penicillin? to eliminate the organism.

18. Corynebacterium: Resistance to ??-Lactam Drugs Corynebacterium amycolatum, C. jeikeium, and C. urealyticum are characteristically resistant to penicillin and other ??-lactam drugs, and uniformly vancomycin susceptible

20. C. diphtheria toxin Toxin enters through receptor mediated endocytosis Acidification of endocytic vesicle allows A to dissociate from B A enters cyctoplasm and inhibit protein synthesis by rection with EF

22. Specimen: A throat swap Culture: The swap is inoculated on Loeffler's serum medium and/or on blood tellurite agar aerobically at 37C for 24. On Loeffler's serum medium: Corynebacteria grow much more readily than other respiratory pathogens Deep blue or red metachromatic granules (accumulated inorganic polyphosphates) by methylene blue stain

24. Cultural characteristics On blood tellurite agar It is selective medium for isolation of C. diphtheriae (Potassium tellurite)

26. 3 biotypes of C. diphtheriae are characterized on BTA i.e. Gravis, mitis and intermedius biotypes The most severe disease is associated with the gravis biotype Colony of gravis biotype is large, non-hemolytic & grey. Colonies of mitis biotype are small, hemolytic and black Colonies of intemedius biotype are intermediate in size, non-hemolytic with black center & grey margin.

27. Morphology Gram +ve, nonspore forming nonmotile bacilli Club-shaped (Coryne= club) arranged at acute angles or parallel to each other (Chinese letters appearance) Beaded (metachromatic granules) Gram stain: C. diphteriae are gram positive bacilli arranged in Chinese letters form often club shaped

28. Biochemical Reaction All Corynebacterium species are catalase positive (Also, Staphylococcus and Bacillus species are catalase positive)

30. Detection of toxin: Elek?s Test Principle: It is toxin/antitoxin reaction Toxin production by C.diphtheriae can be demonstrated by a precipitation between exotoxin and diphtheria antitoxin Procedure: A strip of filter paper impregnated with diphtheria antitoxin is placed on the surface of serum agar The organism is streaked at right angels to the filter paper Incubate the plate at 37C for 24 hrs

31. Resuls: After 48 hrs incubation, the antitoxin diffusing from filter paper strip and the toxigenic strains produce exotoxin, which diffuses and resulted in lines four precipitation lines radiating from intersection of the strip and the growth of organism

32. Treatment Infected patients treated with anti-toxin and antibiotics Anti-toxin produced in horses Antibiotics have no effect on circulating toxin, but prevent spread of the toxin Penicillin drug of choice with erythromycin

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