title: Rapid detection of extensively drug-resistant (XDR-TB) strains from multidrug-resistant tuberculosis (MDR-TB) cases isolated from smear-negative pulmonary samples in an Intermediate Reference Laboratory in India.
abstract: BACKGROUND
  Direct sputum smear microscopy is commonly used for diagnosing tuberculosis (TB). The objectives of the study were first, to determine the recovery of Mycobacterium tuberculosis in smear-negative sputum samples through liquid culture (using MGIT 960) and solid culture (using LJ slant) and second, to screen multidrug-resistant isolates through line probe assay and further third, to identify XDR isolates through MGIT second-line DST from these positive MDR cultures in Delhi region.
  
  
  METHODS
  In this study, the sample size was 717 (sputum smear AFB negative and culture positive for M. tuberculosis complex by both solid and liquid culture methods) MDRTB suspects who were enrolled from January 2014 to December 2014 at the Intermediate Reference Laboratory in New Delhi Tuberculosis Centre, New Delhi. Rapid line probe assay was performed on all culture-positive samples, which were direct smear-negative specimens, and LPA-confirmed MDR samples were tested on MGIT 960 second-line DST for identification of XDR strains.
  
  
  RESULTS
  An overall increase in the culture positivity (9.4%) among these smear-negative cases shows a good sign of recovery from M. tuberculosis infection in these samples. 717 (9.4%) positive cultures (MGIT+LJ) were subjected to line probe assay. Out of these 717 cultures, 9 (1.2%) were confirmed as NTM, 50 (7%) were MDR, 4 (0.6%) were mono-rifampicin resistant and 654 (91.2%) cultures were sensitive to both drugs Rif and Inh, respectively. Out of these 54 (50 MDR +4 mono-RIF resistant) cultures as screened by LPA, 1 (1.8%) was XDR, 10 (18.6%) were mono-ofloxacin resistant and 1 (1.8%) was mono-Kanamycin resistant. Sensitivity to both drugs KAN and OFX was seen in 42 (77.8%) cultures.
  
  
  CONCLUSIONS
  Since the bacterial load in direct smear-negative suspected MDR samples is less, it is important to recover mycobacteria by rapid liquid culture method in such samples. Initial screening for MDRTB is to be done in such cases by performing rapid molecular genotypic drug susceptibility test such as LPA. Baseline second-line DST is also done to rule out the XDR cases among them for rapid and better management of XDRTB patients.
authors.affiliation: New Delhi Tuberculosis Centre - Jawahar Lal Nehru Marg, New Delhi, India.
authors.forename: Himanshu
authors.initials: H
authors.lastname: Vashistha
authors.affiliation: New Delhi Tuberculosis Centre - Jawahar Lal Nehru Marg, New Delhi, India. Electronic address: irldlndc@rntcp.org.
authors.forename: M
authors.initials: M
authors.lastname: Hanif
authors.affiliation: New Delhi Tuberculosis Centre - Jawahar Lal Nehru Marg, New Delhi, India.
authors.forename: Sanjeev
authors.initials: S
authors.lastname: Saini
authors.affiliation: LokNayak Hospital, Chest Clinic (TB), Jawahar Lal Nehru Marg, New Delhi, India.
authors.forename: Ashwani
authors.initials: A
authors.lastname: Khanna
authors.affiliation: New Delhi Tuberculosis Centre - Jawahar Lal Nehru Marg, New Delhi, India.
authors.forename: Srashty
authors.initials: S
authors.lastname: Sharma
authors.affiliation: New Delhi Tuberculosis Centre - Jawahar Lal Nehru Marg, New Delhi, India.
authors.forename: Zeeshan
authors.initials: Z
authors.lastname: Sidiq
authors.affiliation: New Delhi Tuberculosis Centre - Jawahar Lal Nehru Marg, New Delhi, India.
authors.forename: Vasim
authors.initials: V
authors.lastname: Ahmed
authors.affiliation: New Delhi Tuberculosis Centre - Jawahar Lal Nehru Marg, New Delhi, India.
authors.forename: Manoj
authors.initials: M
authors.lastname: Dubey
authors.affiliation: New Delhi Tuberculosis Centre - Jawahar Lal Nehru Marg, New Delhi, India.
authors.forename: K K
authors.initials: KK
authors.lastname: Chopra
authors.affiliation: Jaipur National University, School of Life Sciences, Jagatpura, Jaipur, Rajasthan, India.
authors.forename: Divya
authors.initials: D
authors.lastname: Shrivastava
mesh_terms: D000995:Antitubercular Agents; D015373:Bacterial Typing Techniques / Q000379:methods*; D054908:Extensively Drug-Resistant Tuberculosis / Q000175:diagnosis* / Q000382:microbiology*; D006801:Humans; D007194:India; D007538:Isoniazid; D008826:Microbial Sensitivity Tests; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000302:isolation & purification*; D012293:Rifampin; D013183:Sputum / Q000382:microbiology*
chemical_list: D000995:Antitubercular Agents; D007538:Isoniazid; D012293:Rifampin