Isolation and identification of Mycobacterium tuberculosis from the urine samples by conventional and molecular methods

Genitourinary tuberculosis presents a challenge in diagnosis and treatment due to variations in clinical and radiological signs, insufficient patient history and difficulty in the isolation of the bacilli. The aim of this study was to isolate and identify Mycobacterium tuberculosis from the urine samples obtained from patients with suspected urinary tuberculosis admitted to our hospital by using Ehrlich-Ziehl-Neelsen (EZN), culture and polymerase chain reaction-restriction analysis (PCR-RFLP) methods. A total of 1004 urine samples collected from 437 patients who were admitted to our hospital between January 2004-July 2006, were inoculated on Löwenstein-Jensen (LJ) and/or BACTEC 12B (Becton Dickinson, USA) after decontamination and, direct preparations stained with EZN method were evaluated microscopically. M. tuberculosis complex (MTC) and mycobacteria other than tuberculosis (MOTT) were differentiated by nitro-alpha-acetylamino-beta-hydroxypropiophenone (NAP) test and the susceptibility testing for the MTC strains to primary antituberculosis drugs were performed by BACTEC 460 TB (Becton Dickinson, USA) system. PCR-RFLP method was performed for the identification of Mycobacterium spp. Twenty-two (5%) patients have yielded positive results by at least one of the conventional methods (EZN, LJ and/or BACTEC). Fifteen samples were positive for acido-resistant bacilli (ARB) by EZN method, and 17 samples were positive for mycobacterial growth in the cultures. Ten of 22 patients were found positive by both of the methods, while seven were culture positive but ARB negative and five were culture negative but ARB positive. These five patients received BCG treatment because of the presence of bladder tumor. Twelve (70.5%) of 17 strains isolated from culture were identified as MTC, while five (29.4%) were identified as M. fortuitum. Of 12 MTC isolates, eight (66.7%) were found susceptible to all of the antituberculosis agents, while one was found resistant to isoniazide (INH) and ethambutole (ETB), one was resistant to INH and rifampicin (RIF), and two were resistant to only INH. It is concluded that, in order to identify mycobacteria and to perform antituberculous susceptibility tests, cultivation of mycobacteria is a prerequisite.