title: Improved detection of Mycobacterium tuberculosis using two independent PCR targets in a tertiary care centre in South India.
abstract: BACKGROUND
  Tuberculosis (TB) causes significant morbidity and mortality worldwide as one of the leading infectious diseases. In India, more than 1.8 million new cases occur every year. Rapid and accurate diagnosis of TB would improve patient care and limit its transmission. This study aimed to evaluate a dual target polymerase chain reaction (PCR) diagnostic assay to detect Mycobacterium tuberculosis from pulmonary and extra-pulmonary samples at a tertiary care centre in South India.
  
  
  METHODS
  Samples were collected from patients with a low index of suspicion of TB. Acid-fast smears were performed by Auramine O fluorescent microscopy and PCR was performed by using two site-specific primer pairs targeting IS6110 by nested PCR and TRC4 by conventional PCR. Amplified products for IS6110 and/or TRC4 were indicative of M. tuberculosis.
  
  
  RESULTS
  Among 114 (19 pulmonary and 95 extra-pulmonary) samples tested by PCR assay, 12 (11%) were positive for both IS6110 and TRC4, of which 11 (10%) were non-respiratory and one was (1%) respiratory in origin. PCR for TRC4 alone was positive for eight (7%) non-respiratory and two (2%) respiratory samples, while IS6110 alone tested positive for six (5%) non-respiratory samples and one (1%) respiratory sample. Of a total of 29 PCR positive samples, 17 (15 %) were acid-fast smear positive.
  
  
  CONCLUSIONS
  Although the target site of IS6110 is specific for M. tuberculosis, some strains from South India may lack this region. Therefore, the use of an additional target site (TRC4) is required for improved detection of M. tuberculosis.
authors.affiliation: Department of Microbiology , Sri Ramachandra University, Porur, Chennai, India. ramya_viro@yahoo.com
authors.forename: Ramya
authors.initials: R
authors.lastname: Barani
authors.forename: Gopalsamy
authors.initials: G
authors.lastname: Sarangan
authors.forename: Tessa
authors.initials: T
authors.lastname: Antony
authors.forename: Soundararajan
authors.initials: S
authors.lastname: Periyasamy
authors.forename: Anupma Jyoti
authors.initials: AJ
authors.lastname: Kindo
authors.forename: Padma
authors.initials: P
authors.lastname: Srikanth
mesh_terms: D001826:Body Fluids / Q000382:microbiology; D017931:DNA Primers / Q000235:genetics; D004251:DNA Transposable Elements / Q000235:genetics*; D004269:DNA, Bacterial / Q000032:analysis; D005260:Female; D006801:Humans; D008297:Male; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000302:isolation & purification*; D016133:Polymerase Chain Reaction / Q000379:methods*; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics*; D014376:Tuberculosis / Q000175:diagnosis* / Q000382:microbiology; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000382:microbiology
chemical_list: D017931:DNA Primers; D004251:DNA Transposable Elements; D004269:DNA, Bacterial