Abstract:
Objective: To find out the frequency of Extensively Drug Resistant (XDR) and pre-XDR tuberculosis in clinical isolates of
Multi-Drug Resistant (MDR) Tuberculosis (TB) by determining the susceptibilities against Levofloxacin and Amikacin
(classical second line antituberculosis drugs).
Study Design: A descriptive cross-sectional study.
Place and Duration of Study: Microbiology Department, Armed Forces Institute of Pathology (AFIP), Rawalpindi, from
September 2011 to August 2013.
Methodology: Amikacin (AK) and Levofloxacin (LEVO) were obtained in chemically pure form from Sigma (Taufkirchen,
Germany). The breakpoint concentration used for AK was 1.0 ìg/ml and for LEVO 2.0 ìg/ml. Mycobacterial Growth
Indicator Tube (MGIT) 960 system was used to carry out drug susceptibility testing as per recommended protocol.
Results: A total of 3 MDR-TB isolates (3%) turned out to be XDR-TB based upon simultaneous resistance to injectable
second line antituberculosis drug AK and one of the fluoro-quinolones (LEVO). A total of 24 MDR-TB isolates (24%) were
found to be pre-XDR based upon resistance to LEVO alone. Treatment status record of patients with XDR and pre-XDRTB
isolates revealed that majority of patients had received fluoroquinolones (FQs) during the course of treatment.
Conclusion: XDR-TB has started to emerge in MDR-TB isolates in our set up. The worrying sign is the high frequency of
pre-XDR tuberculosis. Urgent steps need to be taken to stem the tide of pre-XDR-TB in our population. It is thus
recommended to develop facilities to carry out drug susceptibility testing to monitor the status of pre-XDR and XDR-TB in
our population.
