MYCOBACTERIAL DISEASES

1. MYCOBACTERIAL  DISEASES

2. Mycobacterium tuberculosis Obligate aerobe acid-fast rods

3. TUBERCULOSIS OVERVIEW, CAUSE, AND PATHOGENESIS • Tuberculosis, MTB, or TB (short for tubercle bacillus) • common, and in many cases lethal infectious disease • caused by various strains of mycobacteria • usually Mycobacterium tuberculosis • Mycobacterium tuberculosis, was identified and described on 24 March 1882 by Robert Koch • Tuberculosis may infect any part of the body • most commonly occurs in the lungs • pulmonary tuberculosis

4. Tuberculosis holds a special place in medical history • Can humble master clinicians • challenge public health authorities • treatable and preventable • WHO • over 8 million cases • 2 million deaths occur worldwide each year • 25% to 33% of the world’s population with silent latent infection with M. tuberculosis

5. Tuberculosis in the United States is now largely a disease of the disadvantaged • In 2006, there were 13,767 reported cases of TB in the United States • cases were reported in every state • drug-resistant cases • co-infection with M. tuberculosis and HIV • estimated 10 to 15 million persons remain latently infected

6. Mycobacterium tuberculosis • slightly curved or straight rod-shaped bacillus • requires special acid-fast stains to be visualized • It is closely related to M. bovis • primarily pathogen of cattle and related animals • M. tuberculosis is also related to M. leprae • leprosy

7. Tuberculosis is spread from person to person • through the air by droplet nuclei • 1 to 5 m in diameter that have been expulsed into the air • Cough is the primary means by which tubercle bacilli are aerosolized • singing, sneezing, or speaking may contribute to a lesser extent • Droplet nuclei • small enough to remain suspended in the air for long time • The probability of transmission depends on numerous factors • source case • exposed contact • air space shared

8. Usual pathogenesis of tuberculosis. About 5% of infected persons develop clinical disease within the first year of infection; another 5% develop reactivation later during their lives.

9. TB pathogenesis begins when a droplet containing viable tubercle bacilli is inhaled • Bacilli then spread through the pulmonary lymphatics • reach lymph nodes • may become enlarged • Efferent lymphatics then carry bacilli into the systemic circulation • the lungs, the brain, kidneys, and bones • Tubercle bacilli replicate relatively slowly • dividing time within 18 to 24 hours • 20 minutes for most common pathogens • Thus, the process of local, lymphatic, and eventual systemic spread described above typically requires several weeks

10. PULMONARY TUBERCULOSIS • Worldwide, tuberculosis remains the most common cause of death • Pulmonary tuberculosis is the most common manifestation and the form of the disease usually responsible for its transmission • The usual patient with pulmonary tuberculosis presents with a history of several weeks of a progressive illness • The most important pulmonary symptom is cough • Constitutional complaints coexist and may predominate • fever, chills, night sweats, weight loss, appetite loss, and easy fatigability

14. HIV and TB • HIV has greatly increasing the risk of TB • Diagnosis of TB in patients with HIV can be difficult • Suspicion of TB is an indication for HIV antibody testing

15. Laboratory diagnosis 1- Mantouxskin test (Tuberculin) 2- Chest X-ray 3- Isolation of Mycobacterium species • Löwenstein–Jensen medium (L.J medium) • microscopic positive results for acid-fast bacilli 4- Identification of microbial genetic material • molecular methods such as PCR

16. Positive skin test - tuberculosis • indicates exposure to organism • does not indicate active disease

17. The Mantoux skin test consists of an intradermal injection of one-tenth of a milliliter (ml) of PPD tuberculin.

18. The size of induration is measured 48–72 hours later. Erythema (redness) should not be measured.

19. Mantoux test injection site in a subject without chronic conditions or in a high-risk group clinically diagnosed as negative at 50 hours

20. Skin testing for tuberculosis, using the Mantoux test.

21. Chest X-ray

22. Microscopic Examination of Mycobacterium • The Mycobacteria are aerobic acid fast, non-motile, non-spore forming rods • M. tuberculosis is a non-spore forming, non capsulated straight or slightly curved rod, measuring 1-4µm x 0.2-0.6 µm • The most common pathogens that cause disease to man are • M. tuberculosis, M. bovis, M. africanum, and M.microti

23. Laboratory diagnosis M. tuberculosis • acid fast bacteria • sputum TB in Sputum

24. M. tuberculosis is best demonstrated by using the Ziehl -Neelsen technique or a fluorescence technique. When stained by ZN, they appear as thin pink rods arranged singly or in groups. Once stained, they resist decolorization with 2% H2SO4 and alcohol or 3% HCl in 95% ethyl alcohol (Acid-fast, Alcohol fast).

25. Cultural Characteristics and colony morphology • M. tuberculosis is strict aerobic • grows very slowly (2-4 weeks) • egg enriched medium • Lowenstein-Jensen medium • giving dry creamy colored colonies • Other selective media as Middlebrook 7H10, 7H11 agar and 7H9 broth • used for primary isolation • antibiotic susceptibility testing • M. tuberculosis is a non chromogen • does not grow on media contain p-nitrobenzoicacid • these characteristics help to differentiate them from M. avium, M. intracellulare, and M. kansasii

26. The optimum temperature for growth is at 37C • The culture must be incubated up to 12 weeks • M. tuberculosisproduces rough, and tough colonies on glycerol and pyruvate egg media • They are niacin producers and grow under aerobic conditions at 37 C

27. TB Culture Cultivation and culture characteristics of Tubercle bacilli on Lowenstein Jensen medium (raised dry cream colored colonies)

28. Tuberculosis • polymerase chain amplification • rapid diagnosis

29. Antibotic treatment - tuberculosis • extensive time periods (e.g. 9 months) • organism grows slowly, or dormant • two or more antibiotics • e.g. rifampin and isoniazid • resistance minimized

30. Tuberculosis and Drug resistance • Multiple drug resistant (MDR) • resistant to first line drugs • Extremely drug resistant (XDR) • Resistant to some of the second line drugs • Nearly un-treatable

31. Transmission -tuberculosis • M. tuberculosis causes disease • healthy individuals • transmitted man-man • airborne droplets

32. Aerosol from Sneeze

33. Vaccination • BCG vaccine • an attenuated strain of M. bovis • not effective • in US, • incidence is low • vaccination not practiced • immunization interferes with diagnosis

34. An apparatus (4-5 cm length, with nine short needles) used for BCG vaccination in Japan. Shown with ampoules of BCG and saline.

36. M. avium- M. intracellulare complex (M. avium) • non-AIDS • infection almost never • AIDS • major bacterial opportunist • multiple drug-resistance

37. M. bovis • spread from cattle • infected cattle are culled • positive skin test • rarely seen in US

38. M. leprae • leprosy • major disease of third world • rare in US

39. A 24-year-old man from Norway, infected with leprosy, 1886.

40. Deformities from leprosy in India