title: Anti-tuberculosis drug resistance and associated risk factors in a tertiary level TB center in Iran: a retrospective analysis.
abstract: BACKGROUND
  This study aimed to determine first-line anti-tuberculosis drug resistance rates in new and previously treated cases and to identify risk factors associated with multidrug resistant tuberculosis (MDR-TB) at the National Reference Tuberculosis Laboratory of Iran.
  
  
  METHODS
  This was a retrospective analysis of all confirmed TB patients from December 2000 to June 2005. Drug susceptibility testing to isoniazid, rifampicin, streptomycin, ethambutol and pyrazinamide was performed on Löwenstein-Jensen (LJ) medium according to the proportion method.
  
  
  RESULTS
  Mycobacterium tuberculosis strains were isolated from 1,742 patients with TB, of whom 935 (53.7%) were male. The mean age of patients was 44.2 ± 17.4 years (SD). A total of 1,074 patients were native Iranians while 668 (38.3%) were immigrant patients. Out of 1,139 (65.4%) new cases, 340 (29.9%) had at least one drug resistance. Of 603 (34.6%) previously treated cases, 416 (69.0%) had resistant strains. There were 263 patients (15.1%) with MDR-TB, 72 of whom were new (6.3% of all new cases) and 191 were previously treated (31.7% of all previously treated cases). Factors associated with MDR-TB included age under 45 years, male sex, previous TB treatment, immigration, poor living conditions, and unemployment.
  
  
  CONCLUSIONS
  The high rate of initial resistance in MDR-TB cases and the high rate of MDR-TB in a young age group were indicators of recent transmission. Therefore, closer monitoring of transmission trends of drug resistant strains should be considered as priority, to ensure a successful TB control programme.
authors.affiliation: Mycobacteriology Research Center-National Research Institute of Tuberculosis and Lung Disease, Masih Daneshvari Hospital, Shahid Beheshti University of Medical Sciences, Darabad, Tehran, Iran . muayadfaily@yahoo.com
authors.forename: Muayad Aghali
authors.initials: MA
authors.lastname: Merza
authors.forename: Parissa
authors.initials: P
authors.lastname: Farnia
authors.forename: Payam
authors.initials: P
authors.lastname: Tabarsi
authors.forename: Mehdi
authors.initials: M
authors.lastname: Khazampour
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Masjedi
authors.forename: Ali Akbar
authors.initials: AA
authors.lastname: Velayati
mesh_terms: D000328:Adult; D000995:Antitubercular Agents / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D005260:Female; D006801:Humans; D007492:Iran / Q000453:epidemiology; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000302:isolation & purification*; D012189:Retrospective Studies; D012307:Risk Factors; D018088:Tuberculosis, Multidrug-Resistant / Q000453:epidemiology*
chemical_list: D000995:Antitubercular Agents