As previously mentioned, prophylactic chemotherapy with INH is used when known or suspected primary tuberculous infection causes a risk for clinical disease. At present, the BCG vaccine (named after Calmette and Gu&in) is the only available vaccine against tuberculosis. The effectiveness of this live vaccine is controversial because studies have demonstrated ineffectiveness to 80% protection. The greatest potential value for this vacdne is in developing countries that have high prevalence rates for tuberculosis. Nevertheless, at least four types of antituberculosis vaccines are currently being evaluated in experimental studies using animals for possible subsequent use in humans.
A 40-year-old HIV-positive man on HAART (highly active anliretroviral therapy) presented with progressive encephalomyeloradicuopathy. He had no fever, cough or weakness, but had severe headaches. CSF was collected and contained 25 white blood cells (WBCs) per cubic millimeter (/mm3), low glucose, devated protein, and no organisms on Gram stain or add-fast stain. His studies were negative for cryptococcal antigen, toxoplasma by serology, and herpes simplex virus (HSV) by PCR. Routine bacterial culture was negative. Despite therapy for HSV and routine aerobic bacterial causes of meningitis, over the next 4 days he spiked fevers and a second CSF specimen showed 415 WBCs/mm3, with no diagnosis. A battery of viral encephalitis serology tests was done and all were negative. An in-house PCR of a third CSF specimen was positive for Mycobacterium tuberculosis, which grew in culture after 4 weeks.
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