Tuberculosis (PDF)

NOTES NOTES TUBERCULOSIS MICROBE OVERVIEW ▪ Tuberculosis (AKA Mycobacterium ▫ Staining: acid-fast stains like Ziehl– tuberculosis) mycobacterium that primarily Nee...

NOTES NOTES TUBERCULOSIS MICROBE OVERVIEW ▪ Tuberculosis (AKA Mycobacterium ▫ Staining: acid-fast stains like Ziehl– tuberculosis) mycobacterium that primarily Neelsen, fluorescent stains like infects lungs but may infect any bodily auramine/rhodamine organ/tissue ▪ Clumped colonies ▪ Important properties ▪ Distinctly slow growing (up to 6 weeks for ▫ Curved rod shaped bacteria often visible growth) wrapped together in cord-like ▪ Grown on Lowenstein–Jensen media formations ▪ Resistant to weak disinfectants, can survive ▫ Obligate aerobe on dry surfaces for months ▫ Impervious to Gram staining due to ▪ Can avoid mucus traps, getting into deep waxy cell wall composed of fatty acids airways (alveoli) (e.g., mycolic acid) MYCOBACTERIUM TUBERCULOSIS osms.it/mycobacterium-tuberculosis fusion → bacteria survives, proliferates, PATHOLOGY & CAUSES creates localized infection → primary tuberculosis development TYPES ▫ TB infiltrated macrophage fusion → Primary tuberculosis Langhans giant cells ▫ Cell-mediated immunity activation → Reactivation tuberculosis granuloma forms within infected area → ▪ In about 5–10% cases of primary TB caseous necrosis inside granuloma → Ghon focus Extrapulmonary tuberculosis ▫ Lymphatic dissemination of TB → lymph ▪ May involve any organ (most commonly node caseation kidneys, meninges, lymph nodes, etc.) ▫ Ghon focus + involved lymph node → ▪ Systemic miliary tuberculosis Ghon complex ▫ Ghon complex fibrosis, calcification → STAGING Ranke complex ▪ Transmitted by inhaling infectious aerosol ▪ Primary infection resolution droplets from individual with active TB (e.g. ▫ Mycobacteria killed by immune system coughing, sneezing, speaking, etc.) ▫ Bacteria walled off in granuloma ▪ TB enters lungs, gets phagocytized by remains dormant but viable → macrophages → TB produces enzymes that latent tuberculosis with no further inhibit lysosome and phagocytic vacuole complications in immunocompetent OSMOSIS.ORG 583  individuals ▪ Compromised immune system → more caseous necrosis areas → cavity formation → reactivation tuberculosis RISK FACTORS ▪ Immunocompromised states ▫ HIV ▫ Diabetes mellitus ▫ Hematologic malignancy ▫ Chronic lung disease (especially silicosis) ▫ Malnutrition ▫ Aging ▪ Substance abuse ▫ Alcoholism Figure 105.1 The gross pathological ▫ Injection drug users appearance of a Ghon focus. ▪ Close contact with individuals with active TB infection ▫ Healthcare providers SIGNS & SYMPTOMS ▫ Incarceration ▪ Lower-income, medically underprivileged ▪ Primary tuberculosis countries ▫ Usually asymptomatic (90-95% of ▫ Recent immigrants from high- cases) prevalence countries ▫ Mild flu-like illness ▫ Rarely pleural effusion COMPLICATIONS ▪ Reactivation tuberculosis ▪ Bronchopneumonia ▫ Constitutional symptoms (fever, chills, ▪ Pneumothorax night sweats, fatigue, appetite loss, ▪ Extrapulmonary tuberculosis weight loss, pleuritic chest pain) ▫ Kidney → dysuria, pyelonephritis with ▫ Cough (dry cough, prolonged sterile pyuria cough producing purulent sputum, ▫ Meninge → meningitis hemoptysis—suggesting advanced TB) ▫ Lumbar vertebrae → Pott disease ▫ Crepitations during lung auscultation ▫ Liver and gallbladder → hepatitis, ▪ Extrapulmonary tuberculosis obstructive jaundice ▫ Depending on affected organ/tissue ▫ Lymph nodes → cervical tuberculous ▪ Miliary (disseminated) tuberculosis lymphadenitis (scrofula) ▫ Can affect any organ (e.g. choroidal ▫ Peritonitis tubercles in eye, granulomas within ▫ Pericarditis organs) ▪ Systemic infection ▫ Weight loss ▫ Fever, chills ▫ Dyspnea 584 OSMOSIS.ORG  Chapter 105 Tuberculosis Antibiotic resistance DIAGNOSIS ▪ Multiple-drug-resistant TB ▫ Resistant to isoniazid and rifampin DIAGNOSTIC IMAGING ▪ Extensively drug-resistant TB ▫ Resistant to both isoniazid and rifampin, Chest X-ray any fluoroquinolone, at least one ▪ Used in PPD/IGRAs positive second-line drug ▪ Ranke complex → sign of healed primary TB ▪ Cavities → active TB sign LAB RESULTS PPD intradermal skin test (tuberculin test) ▪ Screening test for people at high risk for TB ▫ Tuberculin injection between dermal layers, induration area measurement within 48–72 hours ▪ Induration area ≥ 5mm: positive in immunocompromised individuals, persons with primary TB radiographic evidence/ close contact with those with active TB ▪ Induration area ≥ 10mm: positive in residents/immigrants from high-prevalence countries, children > four years of age, high Figure 105.2 An X-ray image of the chest risk populations (e.g., medical employees) demonstrating diffuse interstitial granular ▪ Induration area ≥ 15mm: considered densities in an individual with milliary positive in individuals with no known risk tuberculosis. factors ▪ Cannot be used for differentiation between active and latent TB ▪ PPD result interpretation ▫ Positive → exposure evidence ▫ False-positive → previously immunized with BCG vaccine ▫ Negative → no exposure evidence ▫ False-negative → sometimes seen in individuals with sarcoidosis, malnutrition, Hodgkin’s lymphoma Sputum testing ▪ Used for definitive diagnosis ▪ Staining, culture, PCR OTHER DIAGNOSTICS Figure 105.3 Multifocal patchy opacities Interferon gamma release assays (IGRAs) in the right upper lobe of an individual who ▪ Alternative for PPD presented with night sweats, weight loss and ▪ Unlike PPD, doesn’t show false-positive persistent cough. The presenting symptoms results in BCG vaccinated and radiological appearance are consistent with pulmonary tuberculosis. OSMOSIS.ORG 585  TREATMENT MEDICATIONS ▪ Prophylactics ▫ BCG vaccine (some countries) ▪ Latent TB ▫ Isoniazid for 9 months ▪ Active TB ▫ First line anti-TB drugs: isoniazid, rifampin, pyrazinamide, ethambutol/ streptomycin ▪ Antibiotic resistance Figure 105.4 The histological appearance ▫ For multiple-drug-resistant TB, of a tuberculosis granuloma. The granuloma treatment requires second-line drugs is formed of epithelioid macrophages and (amikacin, kanamycin, capreomycin) giant cells with a focus of caseating necrosis at the centre and a rim of lymphocytes at the OTHER INTERVENTIONS periphery. ▪ Active TB ▫ Compulsory isolation (until sputum negative for TB) 586 OSMOSIS.ORG