Importance of differentiating Mycobaterium bovis in tuberculous meningitis

The aim of the article is to describe the principal findings among patients with M.tuberculosis and M. bovis CNS infection. Mycobacterium tuberculosis is one of the most common infectious agents that cause death and neurological sequelae around the world. Most of the complications of CNS TB can be attributed to a delay in the diagnosis. Unfortunately, there are no specific diagnostic tools to support an early diagnosis. Other prognostic factors different from delay in treatment have not been identified. Clinical, radiological and laboratory characteristics were analyzed retrospectively from the medical files of all the patients admitted with the diagnoses of tuberculosis. Of 215 patients admitted with systemic tuberculosis, 64 (30%) had a neurological infection. Positive cultures were found in 54 (84%) cases, 18 (33%) in the CSF and the rest in other fluids or tissues. Adenosin deaminase (ADA) enzyme determination was more sensitive than M. tuberculosis PCR in the CSF for supporting an early diagnosis. In addition to a later clinical stage and treatment lag, positive CSF cultures (P=0.001) and the presence of M. bovis (P=0.020) were prognostic factors for a worse outcome. Neither older age, the presence of tuberculomas versus meningeal enhancement, or HIV co-infection, was associated to a worse prognosis. The isolation of M. bovis subspecies was more common that previously reported, and it was associated to the development of parenchymal lesions (P=0.032) when compared to M. tuberculosis. In this study, positive CSF cultures for M. tuberculosis and further identifying M. bovis species were additional prognostic factors for worse outcome. Positive cultures in systemic fluids other than CSF, even when the patient had no obvious systemic manifestations, and ADA determination in the CSF were noteworthy diagnostic tools for the diagnosis.