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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 spore forming
Non-?-hemolytic on sheep blood agar
C. diphtheriae is fastidious while diphtheriods are non-fastidious
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. 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
Skin and cutaneous forms
14. C. diphtheriae: Causative Agent of Diphtheria Respiratory diseasediphtheria
Incubation period2 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 intropical 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
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.
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)
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: Eleks Test Principle:
It is toxin/antitoxin reaction
Toxin production by C.diphtheriae can be demonstrated by a precipitation between exotoxin and diphtheria antitoxin
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
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