title: Resistance profiles and rpoB gene mutations of Mycobacterium tuberculosis isolates in Taiwan.
abstract: OBJECTIVE
  The rifampicin resistance of Mycobacterium tuberculosis is caused by mutations in the 81-base pair region of the rpoB gene encoding the β-subunit of RNA polymerase. Sequences of the rpoB gene of 68 isolates were analyzed to identify the mutations and to compare the mutations with their related susceptibilities.
  
  
  METHODS
  Susceptibility tests of 68 M. tuberculosis isolates, collected in Taiwan during the period from 1999 to 2011, were performed by the modified agar proportion method according to Clinical and Laboratory Standards Institute recommendations. Sequences of the rpoB gene and the resistance profiles were analyzed and compared with the data from different geographic regions.
  
  
  RESULTS
  Seven alleles were identified. Among 47 isolates of allele 1 (without mutations of rpoB), 46 were rifampicin-susceptible. The other 21 isolates (alleles 2 to 7, with mutations of rpoB) were rifampicin-resistant, including 18 isolates that were multidrug-resistant. Five mutated alleles demonstrated a single mutation. The mutations occurred in the codons 531 (68.2%), 513 (9.1%), 533 (9.1%), 516 (4.5%), and 526 (4.5%). The sensitivity and specificity of rpoB mutations for predicting the rifampicin-resistance of M. tuberculosis were 95.5% and 100%, respectively.
  
  
  CONCLUSIONS
  The most prevalent mutations of the rpoB gene were missense mutations in the critical codons, encoding Ser-531, Gln-513, Leu-533, Asp-516, and His-526. These mutations had high sensitivity and specificity for predicting the rifampicin-resistance of M. tuberculosis isolates. The resistance profiles and the frequencies of mutated codons of the rpoB gene varied in different geographic regions, indicating that resistance evolved under the selective pressure of the therapeutic regimens and the spread of different genetic clones.
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Taichung Veterans General Hospital, Taichung, Taiwan.
authors.forename: Yun-Ho
authors.initials: YH
authors.lastname: Lin
authors.forename: Chun-Hsi
authors.initials: CH
authors.lastname: Tai
authors.forename: Chia-Ru
authors.initials: CR
authors.lastname: Li
authors.forename: Chin-Fu
authors.initials: CF
authors.lastname: Lin
authors.forename: Zhi-Yuan
authors.initials: ZY
authors.lastname: Shi
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics*; D012321:DNA-Directed RNA Polymerases; D024881:Drug Resistance, Bacterial; D006801:Humans; D008826:Microbial Sensitivity Tests; D020125:Mutation, Missense; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D058974:Phylogeography; D017422:Sequence Analysis, DNA; D013624:Taiwan; D014376:Tuberculosis / Q000453:epidemiology* / Q000382:microbiology*
chemical_list: D000995:Antitubercular Agents; D001426:Bacterial Proteins; C505805:rpoB protein, Mycobacterium tuberculosis; D012321:DNA-Directed RNA Polymerases