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Lecture 6:- Corynebacterium diphtheria
- 1. Microbiology Lecture 6:- Corynebacteriumdiphtheria Dr. Raghda Saad Mohammed
- 2. Corynebacterium diphtheria • Morphology: •they are GPB non acid fast & non motile bacilli. Showing Clubbing at one or both ends. Non sporing & non capsulated. the presence Of metachromatic granules (Babes-Ernst) granules serve to distinguish it From diphtheroid. The granules are colored dark purple with methylene Blue. Albert or Neisse's stain • The granules consist of polymerized metaphosphate. The bacilli seen in Chine's letter arrangement this is due to incomplete separation of Daughter cell after binary fission.
- 3. Corynebacterium diphtheria • Biochemicalreaction: They are ferment glucose and maltose with acid production. • Catalase:- positive • Oxidase:- negative • Don’t liquefy gelatin • Urea is not hydrolyzed • Resistance: • It is destroyed by heat (58C for 10 min) • It is sensitive to penicillin. Erythromycin & broad spectrum antibiotics . • It is resistant to drying • Toxin: • Diphtheria produce very powerful exotoxin • Diphtheria toxin is protein in nature. It can be converted in to toxoid
- 4. Corynebacterium diphtheria (toxin thathas lost toxicity but not antigenicity) by : 1. Prolonged storage at 37C 2. Incubation at 37C for 4-6 weeks 3. 3 . 0.2 - 0.4 % formalin o The mechanism of action of toxin inhibits protein synthesis & rapidly kill Susceptible cell. It has affinity for myocardium. Adrenal tissue & nerve Endings. Pathogenesis Incubation period is 3-4 days. The site of infection may be:- 1. Facial 2. Iatyngeal 3. Nasal 4. Otitis 5. Conjunctiva 6. Cutaneous around mouth & nose. 7. Genital .
- 5. Neisseria • General character:they are Gram negative, aerobic, none sporulation non motile, oxidase positive cocci ananged in pairs. The genus contains about 30 species. Two impottant pathogens are: • 1. Neisseria meningitides • 2. Neisseria gonorrhea
- 6. Morphology: They are Gramnegative, oval or spherical, arranged in pair with adjacent sides flattened Classification: They are divided into 4 groups A, B, C, D. Three new groups have also recognized E,F and G. Resistance: They are highly susceptible to heat, desiccation, alteration in PH and disinfectants. They may acquire resistance to streptomycin readily. Neisseria meningitides
- 7. Pathogenicity: Meningococci are stricthuman parasites. The route of infection is usually Nasopharynx. They produce cerebrospinal meningitis and meningococcal septicemia. Toxin: Endotoxin is released by the autolysis of organism, there are Hemorrhagic manifestations Neisseria meningitides
- 8. Morphology: it is strictlya parasite of man. The coccus is Gram negative, oval or spherical with adjacent side concave(bean shaped) arranged in pair. It is found predominantly within the polymorphs. Classification: On the basis of colony morphology, autoagglutinability and virulence there are four biotypes (T1, T2, T3, T4). T1&T2 are small, brown, autoagglutinable and virulent. T3&T4 produce large non pigmented colonies which are a virulent. Resistance: They are killed by heat, drying and antiseptics. It is susceptible to sulfonamides, penicillin and other antibiotics. Neisseria gonorrhoeae
- 9. Pathogenicity: The gonococcus isa specific human parasite causing a venereal disease called gonorrhea. It produces lesion as follows: • Incubation period is 2-8 days. In male it starts as acute urethritis with mucopurulent discharge containing gonococci, Infection may exited along urethra to prostate, seminal vesicle and epididymis. • In females infection involves urethra and cervix uteri, Vagina is spared because of acidic PH. The infection may spread to Bartholin glands, endometrium and fallopian tubes. • Pharyngitis and conjunctivitis may occur. Ophthalmic neonatorum occurs in new borne as a result of infection from genital tract of mother Neisseria gonorrhoeae
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