Detection and identification of Mycobacterium tuberculosis by nested PCR assays in cerebrospinal fluid samples from patients with suspected tuberculous meningitis.

We used the nested polymerase chain reaction (PCR) assays developed previously to detect and identify Mycobacterium tuberculosis (M. tuberculosis) in the cerebrospinal fluid (CSF) samples from patients with suspected tuberculous meningitis and non-tuberculous patients. Our nested PCR assays target the multi-copy IS6110 insertion element and the single-copy mtp40 genomic DNA of M. tuberculosis. These assays, when used in combination, allowed us to detect a very low number of M. tuberculosis in the CSF samples, which otherwise would be undetectable by the culture method, and to distinguish M. tuberculosis from M. bovis. We applied these nested PCR assays to analyze eleven CSF samples. Among these, five of them were from patients with suspected tuberculous meningitis but all except one were culture negative. Our results of PCR assays show that three of these five are M. tuberculosis positive, one of which is M. bovis positive, and only one is M. tuberculosis negative. The other six CSF samples were from the clinically diagnosed non-tuberculous patients. Surprisingly, two of these so called non-tuberculous patients, a subarachnoid hemorrhage (SAH) and the syndrome of inappropriate antidiuretic hormone secretion (SIADH), were shown M. tuberculosis positive. This finding supports a long-standing argument that tuberculous meningitis is one of the causes of these neurological diseases. These nested PCR assays thus provide the neurologists with an important adjunct, in addition to the patient's clinical presentation and laboratory data, for the diagnosis of tuberculous meningitis.