Mutations in an 81-bp region of the rpoB gene associated with rifampin resistance were studied in 41 rifampin-resistant clinical strains of Mycobacterium tuberculosis isolated in Turkey. Fourteen different rpoB alleles, three of which had not been reported before, were found. A reverse hybridization-based line probe assay (the Inno-LiPA Rif.TB test) for rapid detection of the mutations was evaluated with these isolates. Rifampin resistance was correctly identified in 23 of 41 isolates (56.1%) with the kit's R probes specific for these mutations. Seventeen of 41 isolates (41.5%) yielded hybridization patterns, with at least one negative signal obtained with the S probes for the wild type. One isolate was identified as rifampin sensitive by the line probe assay. The rate of concordance of the results of the line probe assay with the results of the in vitro susceptibility test was high (97.6%). These results demonstrate that the line probe assay kit may be useful for the rapid diagnosis of rifampin-resistant tuberculosis.Mycobacterium tuberculosis remains one of the most significant causes of death from an infectious agent, annually leading to 2 million deaths worldwide (4). As the incidence of tuberculosis has increased, there has been a corresponding rise in the incidence of drug-resistant strains of M. tuberculosis. Early diagnosis of the disease and rapid identification of resistance to primary antituberculosis agents are essential for efficient treatment and control of multidrug-resistant (MDR) strains. Rifampin (RIF) is one of the most potent antituberculosis drugs; therefore, resistance to RIF often results in high clinical relapse rates, particularly if RIF resistance is associated with resistance to other antituberculosis drugs (5, 14). Moreover, more than 90% of RIF-resistant isolates are also resistant to isoniazid; therefore, detection of RIF resistance could also identify MDR strains (3, 5, 17). The incidence of pulmonary tuberculosis in Turkey was 35.5 per 100,000 population in 2000. In the Aegean region, 8.2% of M. tuberculosis strains isolated between 1999 and 2001 were found to be resistant to RIF. During the same period, the incidence of resistance to both RIF and isoniazid was 6.8% (6).Collectively, DNA sequencing studies demonstrate that more than 95% of RIF-resistant M. tuberculosis strains have a mutation within the 81-bp hot-spot region (codons 507 to 533) of the RNA polymerase B subunit (rpoB) gene (9,10,12,13,15,16,18,20,21,23,24). In addition, other studies reveal that mutations associated with RIF resistance can also occur in other regions of the rpoB gene, although these occur less frequently (7,8). Several molecular methods have been developed in recent years to evaluate the rpoB gene for RIF resistance mutations, including DNA sequencing, line probe assay, and analysis with DNA microarrays (19). These molecular tests can also serve as a means of detecting molecular epidemiological markers, since the relative frequencies of the alleles associated with resistance can vary geographically ...

The relationship between resistance to rifampicin and rifabutin and genetic alterations in the rpoB gene of 41 rifampicin-resistant isolates of Mycobacterium tuberculosis was evaluated. Although 35 isolates with rifampicin MICs > or = 32 mg/L were also rifabutin-resistant, six isolates with rifampicin MICs of 2-16 mg/L were susceptible to rifabutin (MIC < or = 0.5 mg/L). Mutations Asp516Val, Asp516Tyr, Leu533Pro and the double mutation Met515Ile and Leu533Pro influenced susceptibility to rifampicin, but not to rifabutin. All mutations at codons 531 and 526, except one isolate with a His526Cys mutation, correlated with resistance to both compounds.

Tuberculosis (TB) is an unusual infection in transplant recipients. We evaluated (i) the frequency of TB, (ii) the duration to develop the TB infection, and (iii) clinical consequences, in 380 solid-organ recipients from January 1995 to December 2000. A total of 10 (2.63%) patients (eight renal, two liver transplant recipients) were found to have post-transplantation TB. The frequency of TB in this patient population is 8.5-fold higher than the prevalance in the general Turkish population. Tuberculosis developed within 2-33 months after transplantation, with a median of 15 months. In all of these 10 patients, Mycobacterium tuberculosis (MTB) was isolated from the culture. All the patients continued to have low dose immunosuppressive treatment, and also quadriple antituberculosis treatment [isoniazid (INH), rifampin (RIF), pyrazinamide (PRZ) and ethambutol (ETB)] has been given. The two recipients had died of disseminated form of TB. Relapse was detected in one patient 6 months after the completion of the treatment. As post-transplant TB infection develops mostly within the first year after transplantation, clinicians should be more careful for early and fast diagnosis and treatment should be started immediately.

Serological evidence of previous HAV, HCV and HEV infections was not significantly different between Behçet's patients and other groups. However, previous HBV infection was found in a significantly lower number of BD patients as compared with healthy controls and systemic vasculitic patients.

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