1. Batterjee Medical College

2. Dr. Manal El Said Mycobacterium tuberculosis Head of Medical Microbiology Department

3. Batterjee Medical College Mycobacterium tuberculosis Diseases Characteristics Tuberculosis Aerobic & acid-fast rods High lipid content of cell wall, which prevents dyes used in Gram stain from staining organism. Lipids include mycolic acids & wax D. Grows very slowly, which requires that drugs be present for long periods (months). Produces catalase, which is required to activate isoniazid to active drug.

4. Batterjee Medical College Habitat and Transmission Habitat is human lungs. Transmission is via respiratory droplets produced by coughing. Mycobacterium tuberculosis Pathogenesis Granulomas & caseation mediated by cellular immunity, i.e., macrophages & CD4-positive Tcells (delayed hypersensitivity). Cord factor (trehalose mycolate) virulence factors. Immunosuppression increases risk of reactivation & dissemination.

5. Batterjee Medical College Laboratory Diagnosis Mycobacterium tuberculosis Acid-fast rods seen with Ziehl-Neelsen stain. Slow-growing (3–6 weeks) colony on Löwenstein-Jensen medium. Organisms produce niacin & are catalase-positive. Rough and buff lowenstein jensen agar

6. Batterjee Medical College Laboratory Diagnosis Mycobacterium tuberculosis Acid-fast rods seen with Ziehl-Neelsen stain. Slow-growing (3–6 weeks) colony on Löwenstein- Jensen medium. Organisms produce niacin & are catalase-positive. Skin Test PPD skin test is positive if induration measuring 10 mm or more appears 48 hours after inoculation. Induration is caused by a delayed hypersensitivity. Positive skin test indicates that the person infected & not that the person has the disease tuberculosis.

7. Batterjee Medical College Laboratory Diagnosis Mycobacterium tuberculosis Tuberculin skin test (Mantoux test) or PPD test

8. Batterjee Medical College Treatment Mycobacterium tuberculosis Long-term therapy (6–9 months) with three drugs, isoniazid, rifampin, and pyrazinamide. A fourth drug, ethambutol, is used in severe cases (e.g., meningitis), in immunocompromised patients (e.g., AIDS) & where the chance of isoniazid-resistant organisms is high

9. Batterjee Medical College Treatment Mycobacterium tuberculosis Most patients become noninfectious within 2 weeks of adequate therapy. Treatment of latent (asymptomatic) infections consists of isoniazid taken for 6 to 9 months. Multidrug-resistant (MDR) strains have emerged & require other drug combinations

10. Batterjee Medical College Prevention Mycobacterium tuberculosis BCG vaccine containing live, attenuated Mycobacterium bovis organisms may prevent or limit extent of disease but does not prevent infection with M. tuberculosis.

11. Batterjee Medical College Atypical Mycobacteria These mycobacteria are called atypical because they differ from M. tuberculosis in various ways. Most important difference is that atypical are found in environment, whereas M. tuberculosis is found only in humans. Atypical are called "Mycobacteria other than M. tuberculosis," or MOTTS. Atypical are subdivided into slow growers & rapid growers based on whether they form colonies in more than or less than 7 days.

12. Batterjee Medical College Atypical Mycobacteria The following are important slow growers: Mycobacterium avium-intracellulare complex -They causes tuberculosis-like disease, especially in immunocompromised patients e.g.with AIDS. - It is highly antibiotic-resistant. Mycobacterium kansasii It causes tuberculosis-like disease but is less antibiotic- resistant than MAC.

13. Batterjee Medical College Atypical Mycobacteria Mycobacterium marinum : It causes "swimming pool granuloma or fish tank granuloma," which is a skin lesion at the site of an abrasion acquired in a swimming pool or an aquarium. Mycobacterium scrofulaceum It causes scrofula, which manifests as swollen, nontender cervical lymph nodes (cervical adenitis).

14. Batterjee Medical College The important rapid grower is: Mycobacterium fortuitum-chelonei complex It causes infections of prosthetic joints and indwelling catheters. It also causes skin and soft tissue infections at the site of puncture wounds. The organisms are usually resistant to most antituberculosis drugs. Atypical Mycobacteria

15. Batterjee Medical College Mycobacterium leprae Diseases Characteristics Leprosy. Aerobic, acid-fast rods. Cannot be cultured in vitro. Optimal growth at less than body temperature, so lesions are on cooler parts of the body, such as skin, nose, and superficial nerves.

16. Batterjee Medical College Habitat and Transmission Mycobacterium leprae Humans are reservoir. It founds in armadillos, but it is uncertain whether they are source of infections for humans. Mode of transmission is nasal secretions of patients with lepromatous form. Patients with lepromatous form are more likely to transmit than those with tuberculoid form because they have much higher numbers of organisms than those with tuberculoid leprosy. Prolonged exposure is usually necessary.

17. Batterjee Medical College Mycobacterium leprae Pathogenesis Lesions occur in cooler parts of body, e.g., skin & peripheral nerves. In tuberculoid leprosy, destructive lesions are due to cell- mediated response to organism. Damage to fingers is due to burns & other trauma, because nerve damage causes loss of sensation. In lepromatous leprosy, cell-mediated response to M. leprae is lost & large numbers of organisms appear in lesions & blood.

18. Batterjee Medical College Laboratory Diagnosis Mycobacterium leprae Acid-fast rods are abundant in lepromatous leprosy, but few are found in tuberculoid form. Cultures & serologic tests not done. Lepromin skin test is positive in tuberculoid but not in lepromatous form.

19. Batterjee Medical College Treatment Mycobacterium leprae Dapsone plus rifampin for the tuberculoid form. Clofazimine is added to that regimen for lepromatous form or if organism is resistant to dapsone. Treatment is for at least 2 years.

20. Batterjee Medical College Prevention Mycobacterium leprae Dapsone for close family contacts. No vaccine is available.