Extensively and pre-extensively drug resistant tuberculosis in clinical isolates of multi-drug resistant tuberculosis using classical second line drugs [levofloxacin and amikacin]

ABSTRACT

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]. A descriptive cross-sectional study. Microbiology Department, Armed Forces Institute of Pathology [AFIP], Rawalpindi, from September 2011 to August 2013. Amikacin [AK] and Levofloxacin [LEVO] were obtained in chemically pure form from Sigma [Taufkirchen, Germany]. The breakpoint concentration used for AK was 1.0 microg/ml and for LEVO 2.0 microg/ml. Mycobacterial Growth Indicator Tube [MGIT] 960 system was used to carry out drug susceptibility testing as per recommended protocol. 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. 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