DNA OF MYCOBACTERIUM-TUBERCULOSIS IN FORMALIN-FIXED, PARAFFIN-EMBEDDED TISSUE IN TUBERCULOSIS AND SARCOIDOSIS DETECTED BY POLYMERASE CHAIN-REACTION

Infection with Mycobacterium tuberculosis is a major cause of death wo rldwide. Identification of mycobacteria in tissue sections is usually easily achieved by acid-fast stains, but this method sometimes gives u nsatisfactory results. The authors therefore compared conventional sta ining techniques and polymerase chain reaction (PCR) for mycobacterial DNA sequences in 24 selected tissue samples from patients with tuberc ulosis. In all samples, either positive or negative with acid-fast sta in, mycobacterial DNA fragments were detected. In addition, tissue sam ples from patients with clinically proven sarcoidosis were included as controls. Surprisingly, strong signals for mycobacterial DNA were fou nd in 2 of 15 cases. Polymerase chain reaction is a useful technique i n the demonstration of mycobacterial DNA fragments in patients with cl inically suspected tuberculosis who have acid fast stain-negative hist ology. An epithelioid granulomatous reaction in the lung, negative by acid-fast stain and positive for mycobacterial DNA by PCR, however, do es not permit a diagnosis of tuberculosis, because a positive result c an also be obtained in cases of sarcoidosis. In some cases of sarcoido sis, the causal agent might be either cell wall defective mycobacteria or persistent intracellular DNA from mycobacteria.