title: High-level rifampin resistance correlates with multiple mutations in the rpoB gene of pulmonary tuberculosis isolates from the Afghanistan border of Iran.
abstract: The aim of this study was to investigate the significance of multiple mutations in the rpoB gene as well as predominant nucleotide changes and their correlation with high levels of resistance to rifampin (rifampicin) in Mycobacterium tuberculosis isolates that were randomly collected from the sputa of 46 patients with primary and secondary cases of active pulmonary tuberculosis from the southern region (Afghanistan border) of Iran where tuberculosis is endemic. Drug susceptibility testing was performed using the CDC standard conventional proportional method. DNA extraction, rpoB gene amplification, and DNA sequencing analysis were performed. Thirty-five (76.09%) isolates were found to have multiple mutations (two to four) in the rpoB (beta-subunit) gene. Furthermore, we demonstrate that the combination of mutations with more prevalent nucleotide changes were observed in codons 523, 526, and 531, indicating higher frequencies of mutations among patients with secondary infection. In this study, 76.08% (n = 35) of all isolates found to have mutation combinations involving nucleotide changes in codons 523 (GGG-->GCG), 531 (TCG-->TTG or TTC), and 526 (CAC-->CGC, TTC, AAC, or CAA) demonstrated an association with higher levels of resistance to rifampin (MIC, >or=100 microg/ml).
authors.affiliation: Department of Pathology, The Methodist Hospital Research Institute, 6565 Fannin Street, Houston, TX 77030, USA.
authors.forename: Ahmad Reza
authors.initials: AR
authors.lastname: Bahrmand
authors.forename: Leonid P
authors.initials: LP
authors.lastname: Titov
authors.forename: Alireza Hadizadeh
authors.initials: AH
authors.lastname: Tasbiti
authors.forename: Shamsi
authors.initials: S
authors.lastname: Yari
authors.forename: Edward A
authors.initials: EA
authors.lastname: Graviss
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D012321:DNA-Directed RNA Polymerases; D024881:Drug Resistance, Bacterial; D006801:Humans; D007492:Iran; D008826:Microbial Sensitivity Tests / Q000379:methods; D020125:Mutation, Missense; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification*; D012293:Rifampin / Q000494:pharmacology*; D017422:Sequence Analysis, DNA; D013183:Sputum / Q000382:microbiology; D014397:Tuberculosis, Pulmonary / Q000382:microbiology*
chemical_list: D000995:Antitubercular Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; C505805:rpoB protein, Mycobacterium tuberculosis; D012321:DNA-Directed RNA Polymerases; D012293:Rifampin