Characterization of Tunisian Mycobacterium tuberculosis Rifampin-Resistant Clinical Isolates

Abstract

Analysis of the gene encoding the ␤-subunit of Mycobacterium tuberculosis RNA polymerase (rpoB) has demonstrated a small region that harbors the mutations most frequently associated with rifampin resistance. In this study, we determined the occurrence of rifampin resistance in 544 Tunisian clinical M. tuberculosis strains isolated in a university hospital between 2004 and 2006 by using the standard-proportion agar method, the INNO-LiPA Rif.TB assay, and DNA sequencing.One of the most alarming trends concerning tuberculosis (TB) is the emergence of drug-resistant Mycobacterium tuberculosis strains, which has become a worldwide health care problem (15). The early detection of resistance to primary anti-TB agents is essential for the efficient treatment and control of multidrug-resistant (MDR) strains. Rifampin (RMP) is one of the most potent anti-TB drugs; therefore, resistance to RMP often results in high clinical relapse rates, particularly if RMP resistance is associated with resistance to other anti-TB drugs (8).It has been established that RMP resistance in M. tuberculosis is mainly due to a group of mutations within a limited region of the rpoB gene that encodes the ␤-subunit of the RNA polymerase (28). These mutations can be characterized by PCR single-strand conformation polymorphism analysis (1, 23), heteroduplexing (21), dideoxy fingerprinting (6), the line probe assay (4,7,19), and automated DNA sequencing analysis (9, 24). However, few of these findings are associated with isolates from Tunisia, where the global incidence of TB infection was about 23.54 per 100,000 inhabitants (12). Therefore, the aim of our study was to determine the molecular basis of resistance in M. tuberculosis RMP-resistant strains by using the INNO-LiPA Rif.TB assay (Innogenetics, Ghent, Belgium) and DNA sequencing and to correlate these results with clinical and antibiotic sensitivity data.A total of 544 clinical M. tuberculosis strains from 475 patients were isolated in a university hospital in an urban setting, the Rabta center, Tunis, Tunisia, during a 2-year period (2004 to 2006). The culturing of mycobacterial isolates was performed on solid Löwenstein-Jensen (LJ) medium. All M. tuberculosis cultures were biochemically characterized and confirmed by the AccuProbe method (Gen-Probe Inc., San Diego, CA).Susceptibility testing for isoniazid (INH), RMP, ethambutol (EMB), streptomycin (SM), and ciprofloxacin (CIP) was carried out on LJ medium according to the standard procedure (2, 3). The critical concentrations of RMP, INH, EMB, SM, and CIP were 40, 0.2, 1, 10, and 10 g/ml, respectively. Resistance to RMP was defined as Ն1% growth on RMP-containing medium compared to the rate of growth on control medium. On final analysis of the 544 isolates, 10 (1.83%) were RMP-resistant and 534 were characterized as fully susceptible to RMP. These 10 clinical isolates recovered from six different patients were classified as MDR strains since they were also resistant to INH. Complete medical records were available for all of the six patients...

Sequence analysis for detection of drug resistance in Mycobacterium tuberculosis complex isolates from the Central Region of Cameroon

“…The most common site of nucleotide substitutions in RIF R isolates was codon 531. This finding was similar to those reported in Russia [ 26 ], the US [ 27 ], Tunisia [ 28 ] Ghana [ 21 ] and Germany [ 29 ]. The codon 531 mutation was also reported as the most frequent (68%) in M. tuberculosis isolates of the LAM family in Cameroon [ 30 ].…”

Evaluation the Expression of Efflux Pump Genes “Tap & P55 in Mycobacterium Tuberculosis Clinical Isolates in Fars, Iran

“…The high frequency of mutation in codon 531 was found in previous studies in some other countries, including Indonesia (59.09%) [21], Taiwan (68.2%) [22], India (75.5%) [23], Brazil (79.2%) [24] and Tunisia (85.67) [25], which in these studies, like ours the most common mutation was reported in codon 531 However, in comparison with our study, they reported a higher prevalence of mutation in codons 53.…”

Genotypic assessment of drug-resistant tuberculosis in Baghdad and other Iraqi provinces using low-cost and low-density DNA microarrays

“…The rpoB S531L SNP is the most common mutation site associated with RIF resistance, but the frequency of other rpoB mutations varies depending on geographical location (Kapur et al, 1994;Mani et al, 2003;Pozzi et al, 1999;Soudani et al, 2007). rpoB mutations at position H526Y and S512T feature at high frequency in many regions, and this is not seen herein (Cavusoglu et al, 2002;Sajduda et al, 2004 2003).…”