Mycobacterial Disease

Mycobacterial Disease-

-Atypical Mycobacterial Disease-

-Non tuberculous mycobacteria (NTM) species are those other than those belonging to the mycobacterium tuberculosis complex

-These organisms are free living that are in a ubiquitous environment

-NTM bacteria cause 4 different clinical syndromes in patients:  pulmonary disease, superficial lymphadenitis, disseminated disease in immunocompromised patients, skin and soft tissue infection

-The most common NTM causing pulmonary disease is the mycobacterium avium complex (MAC)

-Disseminated NTM infections can enter the pulmonary system and then enter into the blood stream and seed in other organs.

-Disseminated NTM presents with fever, night sweats, and weight loss, fatigue, malaise, and anorexia

-Disseminated NTM may have organ specific symptoms and signs of major sites of involvement; adenopathy, or hepatosplenomegaly.  Diagnosis is made through blood cultures

-Mycobacterium Kansasii has never been found in natural water or soil supplies.  It is uncovered where it is endemic from tap water.   Presents as lung disease almost identical to tuberculosis

-Rapidly Growing Mycobacteria (RGM) are environmental organisms and may cause pulmonary disease

-Indications for treatment of NTM include:  respiratory symptoms, constitutional symptoms with abnormal x ray, plus consistent isolation of one specimen in pulmonary secretions

-Most studies support use of the newer macrolides against MAC (zithromax and biaxin)

-Currently the recommended regimen for MAC is Biaxin plus Rifampin, plus Ethambutol

-Treatment should be continued until sputum cultures are negative for at least 1 year



-Tuberculosis-

-Tuberculosis (TB) is caused by the organism Mycobacterium Tuberculosis

-Signs and symptoms of TB include fever, productive cough, retrosternal pain, pleuritic pain, arthralgias, pharyngitis, and enlarged bronchial lymph nodes.

-90 percent of patients with normal immunity control further replication and enter a latent phase of TB

-The other 10 percent of patients develop TB pneumonia seeding near hilum, get hilar lymphadenopathy, may get cervical lymphadenopathy, meningitis, pericarditis, or get miliary dissemination

-Symptoms of reactivated TB include cough, hemoptysis, weight loss, fatigue, chest pain, dyspnea, and night sweats

-Findings on chest x ray with reactivation of disease include upper lobe cavitary lesions, hilar lymphadenopathy, and solitary nodules

-CT scans of the Chest is more sensitive for diagnosis the chest x-rays for TB

-Complications of TB include hemoptysis, pneumothorax, sepsis, bronchiectasis, extensive pulmonary destruction including gangrene, malignancy, and chronic pulmonary aspergilliosis

-Two tests available to for diagnosing latent TB infection:  tuberculin skin test (TST) and interferon gamma release assay

-Indications for testing for latent TB include:  close contacts of patients with active TB, casual contact of patients with highly contagious active TB, and healthcare workers and other occupations where there is a high risk of exposure with untreated contagious active TB (prisoners and homeless shelters)

-TST is used to show those that have been sensitized to mycobacterial antigens

-Induration for TST should be reassessed in 48-72 hours because is mediated by T Lymphocytes from a delayed hypersensitivity

-Interpretation of the test is as follows:  greater than 5 mm induration is positive in HIV patients, close contact with an active case, abnormal chest x ray with findings of old TB, and immunosuppressed patients.  Greater than 10 mm of induration is positive in patients with increase risk of reactivation, children less than 4 years, foreign born patients, residents and employees of high risk settings.  Greater than 15 mm of induration is considered positive in healthy people with a truly low likelihood of true TB infection

-To diagnose active TB, clinical manifestations must be present.  Generally a cough greater than 2-3 weeks, night sweats, weight loss, and lymphadenopathy.  History of prior positive TST, and radiographic features and labs consistent with TB.  It is recommended that the patient have at least three sputum specimens for acid fast bacillus (AFB)

-Patient should be respiratory isolation while being ruled out.  Positive patients need to be reported to the local health department.

-Four drugs are used in the initial treatment o f active TB because of concern INH resistance.  The 4 drugs are INH, rifampin, ethambutol, and pyrazinamide

-Duration of initial treatment lasts usually for 8 weeks.  If culture and sensitive implicate sensitivity to one of the 4 agents, then ethambutol can usually be discontinued

-The continuation phases is administered for 4-7 months and usually consists of INH and Rifampin

-Hepatotoxicity needs to be monitored

-Need to reassess sputum culture after treatment to determine if there is treatment failure