Characterization of the etiological agents of tuberculous lymphadenitis in Dera Woreda, North Showa, Ethiopia

Background: Tuberculous lymphadenitis (TBLN) is a common form of extra pulmonary tuberculosis where lymph nodes particularly from cervical, axillary and inguinal sites are mostly involved; however, its diagnosis poses a major challenge in resource limited settings. Objective: To identify the etiological species of Mycobacteria responsible for TBLN in Derra area, a rural district in Ethiopia, where the status of TBLN is unknown. Materials and Methods: A total of 153 patients who were clinically suspected for TBLN, between the periods of August 2004 and February 2005 were included in the study. Fine needle aspirates (FNA) were collected and processed from 145 participants and further analyzed using Ziehl Neelsen staining, culture, cytology and polymerase chain reaction (PCR) using sets of primers, targeting the IS6110 insertion sequence and the pncA gene allelic variation at position 169. Results: Out of the 145 FNA samples, 66 (45.5%) demonstrated growth on Lowenstein - Jensen (LJ) medium and 115 (79.3%) cases were confirmed as TBLN by a combination of results from acid fast bacilli (AFB) smear examination, culture, cytology and PCR. From the 145 clinically suspected TBLN cases, 108 (75%) were identified by PCR at complex level of which 107/108 (99.1%) were positive for M. tuberculosis and 1/108 (0.9%) was positive for M. bovis using pncA primers. Conclusion: The study indicates that M. tuberculosis is the major cause of tuberculous lymphadenitis in Dera area.