If the suspicion of tuberculosis is high or the patient is seriously ill with a disorder, either pulmonary or extrapulmonary, that is thought possibly to be tuberculosis, combination chemotherapy using one of the recommended regimens should be initiated promptly, often before AFB smear results are known and usually before mycobacterial culture results have been obtained. A positive AFB smear provides strong inferential evidence for the diagnosis of tuberculosis. If the diagnosis is confirmed by isolation of M. tuberculosis or a positive nucleic acid amplification test, treatment can be continued to complete a standard course of therapy ( Figure 1 ). When the initial AFB smears and cultures are negative, a diagnosis other than tuberculosis should be considered and appropriate evaluations undertaken. If no other diagnosis is established and the PPD-tuberculin skin test is positive (in this circumstance a reaction of 5 mm or greater induration is considered positive), empirical combination chemotherapy should be initiated. If there is a clinical or radiographic response within 2 months of initiation of therapy and no other diagnosis has been established, a diagnosis of culture-negative pulmonary tuberculosis can be made and treatment continued with an additional 2 months of INH and RIF to complete a total of 4 months of treatment, an adequate regimen for culture-negative pulmonary tuberculosis ( Figure 2 ). If there is no clinical or radiographic response by 2 months, treatment can be stopped and other diagnoses including inactive tuberculosis considered.
Since 1990, CDC has provided epidemiologic assistance during investigations of several MDR-TB outbreaks that occurred in institutional settings. These outbreaks involved a total of approximately 300 cases of MDR-TB and included transmission of M. tuberculosis to patients, HCWs, and correctional-facility inmates and employees in Florida, New Jersey, and New York (18-23). These outbreaks were characterized by the transmission of M. tuberculosis strains resistant to isoniazid and, in most cases, rifampin; several strains also were resistant to other drugs (., ethambutol, streptomycin, ethionamide, kanamycin, and rifabutin). In addition, most of the initial cases of MDR-TB identified in these outbreaks occurred among HIV-infected persons, for whom the diagnosis of TB was difficult or delayed. The fatality rate among persons who had active MDR-TB was >70% in most of the outbreaks.
Frederick M Vincent, Sr, MD Clinical Professor, Department of Neurology and Ophthalmology, Michigan State University Colleges of Human and Osteopathic Medicine
Frederick M Vincent, Sr, MD is a member of the following medical societies: Alpha Omega Alpha , American Academy of Neurology , American Association of Neuromuscular and Electrodiagnostic Medicine , American College of Forensic Examiners Institute , American College of Legal Medicine , American College of Physicians
Disclosure: Nothing to disclose.