Low Levels of Extensively Drug-resistant Tuberculosis among Multidrug Resistant Tuberculosis Isolates and Their Relationship to Risk Factors: Surveillance in Tehran, Iran; 2006 to 2014

OBJECTIVES: Extensively drug-resistant tuberculosis (XDR-TB) is more expensive and difficult to treat than multidrug-resistant tuberculosis (MDR-TB), and outcomes for patients are much worse; therefore, it is important that clinicians understand the magnitude and distribution of XDR-TB. We conducted a retrospective study to compare the estimated incidence of and risk factors for M/XDR-TB with those of susceptible TB controls. METHODS: Sputum culture and drug susceptibility testing (DST) were performed in patients with known or suspected TB. Strains that were identified as MDR were subjected to DST for second-line drugs using the proportion method. RESULTS: Among 1,442 TB patients (mean age, 46.48 ± 21.24 years) who were culture-positive for Mycobacterium tuberculosis, 1,126 (78.1%) yielded isolates that were resistant to at least one first-line drug; there were 33 isolates (2.3%) of MDR-TB, of which three (0.2%) were classified as XDR-TB. Ofloxacin resistance was found in 10 (0.7%) isolates. Women were 15% more likely than men to yield M/XDR-TB isolates, but this difference was not significant. In a multivariate analysis comparing susceptible TB with X/MDR-TB, only one variable—the number of previous treatment regimens—was associated with MDR (odds ratio, 1.06; 95% confidence interval, 1.14–21.2). CONCLUSION: The burden of M/XDR-TB cases is not sizeable in Iran. Nonetheless, strategies must be implemented to identify and cure patients with pre-XDR-TB before they develop XDR-TB. Our results provide a greater understanding of the evolution and spread of M/XDR-TB in an environment where drug-resistant TB has a low incidence.

[Comparative study of protein profile in Mycobacterium tuberculosis and Mycobacterium bovis with SDS-PAGE method]

Mycobacterium bovine, as the etiology of bovine TB, involves human in some cases and with Mycobacterium tuberculosis are regarded as global health problems. The aim of this study was to extract and compare protein profile of these strains in order to achieve effective biomarkers for diagnosis and the vaccine components. First, the clinical samples were cultured on Lowenstein-Jensen [LJ] medium by the N-acetyl-L-cysteine-sodium hydroxide method and the biochemical tests and antibiotic susceptibility were used. Colonies were grown in the Middlebrook 7H9 medium and, upon harvesting the new colonies, secretory and membrane proteins were extracted by sonication and ammonium sulfate and alcohol precipitation. Concentration was determined by Bradford method and finally the comparison was made through one dimensional electrophoresis. The major discrepancy between two strains of Mycobacterium tuberculosis and Mycobacterium bovis was 45 and 60 KDa bands as well as the zone between 14 and 45 KDa bands of secretory proteins, in the banding separation membrane proteins. Discrepancy in the protein bands of sensitive strains and Mycobacterium bovis seems to be used as an effective protein marker or even a biomarker in distinguishing the sensitive and bovis strains; also similarities can be used for immunization purposes

Frequency and molecular characterization of rifampicin-resistance in rpoB region of multiple drug resistance [MDR] isolates from tuberculosis patients in southern endemic region of Iran

The aim of this study was to investigate the frequency, location and type of rpoB gene mutations in Mycobacterium tuberculosis [MTB] collected from patients in the southern endemic region of Iran. Drug susceptibility testing was determined by using the BACTEC system and the center for diseases controls [CDC] standard conventional proportional method. In 29 rifampicin-resistant MTB [85%] isolates, 60 mutations and 13 micro-deletions were identified. Missense mutations produced 23 types of amino acid substitutions. In five rifampicin-resistant MTB isolates [15%] no mutations were found in the core region of the rpoB gene. All silent mutations were localized in codon 507. Most frequent mutations detected in Iranian strains, were found in codons 523 and 526. Five alleles in codon 526 and three alleles occurring in triplets in each of the codons 507, 508, 513 were also found. Thus in Iran the highest frequency of common mutations shared between primary and secondary infections was found to occur in codons 523 and 526