A clinico-bacteriological study of peripheral tuberculous lymphadenitis.

OBJECTIVE: Tuberculous lymphadenitis is the commonest form of extra-pulmonary tuberculosis. It is most often caused by M. tuberculosis though several reports from other countries have shown mycobacteria other than tuberculosis (MOTT) to be responsible for a significant proportion of tuberculous lymphadenitis cases. The present study was conducted to find the prevalence of M. tuberculosis and MOTT as aetiological agents in patients with peripheral tuberculous lymphadenitis. METHODS: A total of 138 patients with tuberculous lymphadenitis were included in the study. Diagnosis of tuberculosis was established on the basis of fine needle aspiration cytology, histopathology, presence of mycobacteria on Ziehl Neelson stain or auramine rhodamine stain, or aspiration of pus with negative Gram's stain and pyogenic cultute with radiologic evidence of pulmonary tuberculosis. Mycobacterial cultures were performed on aspirated material and species identified using standard methods. RESULTS: Of 138 patients, single lymph nodal enlargement was found in 48.6% patients while others had more than one lymph nodes. Lymph nodes were matted in 26.8% cases while fluctuation could be elicited in 12.3% patients. Chest X-ray showed evidence of active pulmonary lesions or mediastinal lymphadenopathy in 28.3% cases. The fine needle aspiration cytology was positive for tuberculous lymphadenitis in 41.3% cases while it revealed granulomas or necrosis in another 13% cases. The Ziehl-Neelson and the auramine-rhodamine staining were positive in 19.6% and 26.8% patients, respectively. On culture, the lymph node aspirate was positive for Mycobacterium species in 40.6% patients. In all but two cases, the culture revealed presence of Mycobacterium tuberculosis. The other two cultures revealed growth of Mycobacterium fortuitum chelonae complex. Of the two HIV-positive patients, M. tuberculosis could be isolated in one case. CONCLUSION: Findings of this study suggest that M. tuberculosis is still the most common cause of tuberculous lymphadenitis and MOTT are responsible for very few cases. However, such studies need to be carried out frequently at various centres so as to see any periodic and geographic variations within India.

Immune response profile in patients with active tuberculosis in a BCG vaccinated area.

Tuberculosis patients with pulmonary (N = 95) or lymph node disease (N = 23) were assessed for Th1 responses (PPD skin test and lymphocyte blastogenic and interferon gamma) and Th2 responses (polyclonal and antigen specific IgE). Skin test responses to PPD and lymphocyte proliferative responses to crude mycobacterial antigens (PPD, culture filtrate and sonicate) and recall antigens (tetanus toxoid and streptolysin O) were significantly suppressed (p < 0.001) in patients with pulmonary disease compared to endemic controls. However, mitogen (phytohemagglutinin)-stimulated responses were comparable in patients and controls. Polyclonal and antigen specific (M. tuberculosis culture filtrate) IgE responses which are considered to be surrogate markers for Th2 responses were significantly higher in patients with pulmonary disease compared to healthy endemic controls (Mann Whitney analysis p < 0.01). Patients with lymph node disease showed strong Th1 responses but did not show significant responses for either polyclonal or antigen specific IgE. Thus overall suppression of T cell memory response was observed only in patients with pulmonary disease but not in patients with lymph node disease suggesting that sequestration of antigen in different compartments leads to differential activation of Th1 and Th2 responses. PPD skin test responses were highly positive in endemic controls (47% positive) and household contacts (86% positive). Furthermore, PPD positivity decreased with disease severity. Therefore PPD positivity in a BCG vaccinated TB endemic area cannot be used as a diagnostic marker for active tuberculosis particularly in advanced disease.