Turberculosis Flashcards
TB - Cause
Mycobacterium tuberculosis Gram + acid fast bacilli
TB - diagnosis
Microscopy, referred to as an AFB smear to visually identify the organism, and culture to detect AFB are the most commonly used procedures to detect TB; A distinguishing feature of M. tuberculosis is its slow growth rate sputum cultures for MTB may take up to 6 weeks before sufficient growth is seen.
TB stage
Latent: form a nodular granulomatous structure in the lung called the tubercle
1st: Lymphadenopathy - Milliary TB: Disseminated disease with lesions resembling millet seeds
Reactivation: mostly in immunosuppression Pt, localized in lung, little regional lymph node involvement and less caseation;
disseminated disease in unusual, unless the host is severely immunosuppressed
TB - Clinical presentation
Latent: asymptomatic 1st and reactive: blood cough, weight loss, fever, night sweats, chest pain and dyspnea, hemoptysis Elderly: fever, sweats, hemoptysis cavitary disease and +TST are less common CXR: upper lobe infiltration, cavitary lesion
Latent TB diagnosis
TST - PPD skin test; cannot tell non TB mycobacteria and vaccination Interfron - gamma release assays (IGRAs) not affected by vaccination; QuantiFERON-TB Gold In-Tube & T-SPOT assay both cannot distinguish between latent and active TB and should bot be use for diagnosis for active TB
Active TB diagnosis
+ TST/IGRA, CXR/CT 3 sputum specimens in 24 hr intervals and at least one in the early morning BAL (bronchoscopy) sufficient and only one specimen needed Gastric secretions: useful in children, early morning fasting; not for adults
Drug-resistant tuberculosis
MTB resistant to one of the first line drugs: isoniazid, rifampin, pyrazinamide or ethambutol
Multidrug- resistant tuberculosis
resistant to isoniazid and rifampin
extensively drug resistant
resistant to isoniazid, rifampin, a FQ and at least one of three injectable 2nd line drug (capreomycin, kanamycin, amikacin)
Latent TB treatment
INH (isoniazid) 300mg PO daily X 9 months alternative: 900mg PO BIW X 9 months 900mg PO BIW X 6 months INH 300mg po daily X 3 months + rifampin 600 mg po daily X 3 month INH: Given 15mg/kg PO once weekly x 12 doses + Rifapentine: Given 900mg PO once weekly x 12 doses only under directly observation
Active TB treatment no resistant
The initial phase consists of a standard four-drug regimen of isoniazid (INH), rifampin (RIF), pyrazinamide (PZA), and ethambutol (EMB) for ~two months. if no INH or rifampin resistance is detected, the continuation phase may begin with a two-drug regimen of INH and rifampin for an additional 4 months
Active TB treatment for mono resistant
Patients with INH monoresistance are typically treated with the remaining three agents (RIF, PZA, and EMB) for a total of 9 months. Rifampin monoresistance is less common but requires use of the remaining three agents (INH, PZA, and EMB) for a total of 12 to 18 months. Pyrazinamide monoresistance just prolongs the continuation phase of INH + RIF by an additional 3 months to a total treatment duration of 9 months. Ethambutol monoresistance does not change therapy or duration from the table above.
TB monitor
If culture is positive at 2 months, the continuation phase is prolonged by an additional 3 months to a total duration of 9 months. Patients with persistently positive cultures at 3 months should have repeat susceptibility testing performed to rule out development of resistance on therapy.
1 st line agents SE
INH: Hepatotoxicity, Peripheral neuropathy could be minimized by using pyridoxine (Vita B6) RIF: Hepatotoxicity, red-orange discoloration of body fluids PZA: GI upset and hepatotoxicity; Hyperuricemia (in GOut) EMB: optic neutitis (color blinded)
