Identification of the Causative Organism of Tuberculous Lymphadenitis in Ethiopia by PCR

Abstract

Tuberculous lymphadenitis (TBLN) is a common form of extrapulmonary tuberculosis with multiple differential diagnoses. Demonstration of the etiologic agent by smear microscopy or culture of fine needle aspirate (FNA) specimens is often unsuccessful. FNA specimens from 40 patients presenting at a rural health center in South Ethiopia and diagnosed as positive for TBLN on the basis of clinical and cytological criteria were analyzed for mycobacterial DNA by PCR. Thirty (75%) had cervical lymphadenitis and 11 (27.5%) were seropositive for human immunodeficiency virus (HIV). Three primer sets were initially used to identify the causative agent at the genus (antigen 85 complex), complex (IS6110 insertion sequence), and species (pncA gene and allelic variation) levels. Among the forty TBLN cases, 35 (87.5%) were positive by PCR at the genus and complex levels. Based on PCR for detection of allelic variation at position 169, 24 (68.6%) of the 35 were positive for Mycobacterium tuberculosis and 6 (17.1%) were positive for M. bovis. These six were positive in additional PCR assays using the JB21-JB22 primer set, which is highly specific for M. bovis. In developing countries with a high incidence of tuberculosis, tuberculous lymphadenitis (TBLN) is one of the most frequent causes of lymphadenopathy (12) and it is the most common form of extrapulmonary tuberculosis (16). TBLN also occurs with increased frequency in human immunodeficiency virus type 1 (HIV-1)-infected individuals (9, 27). Within the Mycobacterium tuberculosis complex, M. tuberculosis and M. bovis are the most common causative agents of TBLN. Which control measures and treatment are to be instituted depends on the most common causative agent in the area. Therefore, species identification is of paramount importance.Over the past decades, fine needle aspirate (FNA) cytology, an alternative procedure less invasive than excision biopsy, has assumed an important role in the diagnosis of peripheral lymphadenopathy. The cytological criteria for diagnosis of TBLN have been clearly defined (13,19). However, the amount of material obtained in FNA is usually so small that it is often inadequate for performance of acid-fast smear and culture examinations with reasonable sensitivity.Introduction of the PCR provided new possibilities for identification of mycobacteria in various types of clinical samples (3, 5); based on the amplification of common sequences, the identification time for detection of mycobacteria in clinical specimens was reduced (4, 8). The M. tuberculosis complex, consisting of M. tuberculosis, M. bovis, M. africanum, and M. microti, has been identified with a number of different targets, including the IS6110 insertion element sequence, using PCR methods (2, 6).In the present study, PCR was applied for assays of FNAs to identify the causative agent in TBLN in Ethiopia at the genus, complex, and species levels. MATERIALS AND METHODS Patients.The study was initiated after approval by the institutional and national ethical committees. FNAs which were collect...

Assessment of possible tuberculous lymphadenopathy by PCR compared to non-molecular methods

“…The positivity rate varies from 61 to 94 % but it is found to be the most sensitive technique (Kim et al, 1996;Ersoz et al, 1998;Manitchotpisit et al, 1999;Baek et al, 2000;Goel et al, 2001;Kidane et al, 2002). The PCR positivities in cases of granuloma only and granuloma with necrosis are reported to be 42 % each, and 15 .…”

Bovine tuberculosis infection in animal and human populations in Ethiopia: a review

“…With respect to this, Kiros (1998) Furthermore, the author indicated that a higher prevalence of BTB in cattle owned by tuberculous patients was found than in cattle owned by nontuberculous owners, which suggests the significant role of M. bovis in the incidences of tuberculosis in humans (Regassa, 2005). In addition, Kidane et al (2002) indicated that M. bovis along with other MTC species were found to be a cause for tuberculous lymphadenitis in humans.…”

“…BTB in the human population mainly takes place through drinking raw milk and occur in the extra-pulmonary form in the cervical lymphadenitis form in particular. Recently, Kidane et al (2002) indicated that M. bovis was found to be a cause for tuberculous lymphadenitis in 17.1% of 29 human tuberculosis cases in Ethiopia. The proportion of which BTB contributes to the total of tuberculosis cases in humans depends on the prevalence of the disease in cattle, socioeconomic conditions, consumer habits, practiced food hygiene and medical prophylaxis measures.…”

Identification and genotyping of the etiological agent of tuberculous lymphadenitis in Ethiopia

“…Among members of the Mycobacterium tuberculosis complex (MTC), M. tuberculosis and M. bovis have been implicated as the most common causes of tuberculous lymphadenitis (TBLN) [3,4,5,6]. In Ethiopia, little has been done to identify how M. bovis causes human TB, despite the population's routine consumption of unpasteurized milk and raw meat.…”