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Baseline resistance and Cross resistance among fluoroquinolones in Multi Drug Resistant Mycobacterium tuberculosis Isolates at a national reference laboratory.

J Glob Antimicrob Resist; 2017 Sep 05.
Article in English | MEDLINE | ID: mdl-28887289


Pre-existing fluoroquinolone (FQ) resistance in Multiple Drug Resistant Tuberculosis (MDR TB) patients is a major threat in treating MDR TB. This study was conducted to assess the percentage of FQ resistance among MDR TB patients and to determine whether there is complete cross-resistance between FQs (ofloxacin, levofloxacin and moxifloxacin) used as second line drugs in TB treatment.


Among 879 MDR TB suspects tested, 68 were confirmed to be MDRTB and mono rifampicin resistant. They were further analyzed for FQ drug resistance by DST using MGIT. The minimal inhibitory concentrations (MIC) were also determined for ofloxacin, levofloxacin and moxifloxacin.


Out of 879 MDR TB suspects, rifampicin resistance was observed in 70 patients (8%). Among which pre-existing FQ resistance was detected in 32% of patients. 88% of isolates exhibited a similar DST pattern for all three FQs tested. Cross resistance among FQs was not complete in 8 isolates. MIC of moxifloxacin was found to be much lower than MICs of ofloxacin and levofloxacin.


A huge proportion of MDR TB strains (32%) exhibiting ofloxacin resistance prior treatment with second line anti TB drugs raises major concern. Baseline drug resistance detection in TB patients helps in cutting down transmission of drug resistant TB. The MIC for Ofloxacin was higher than its critical concentration indicating the prevalence of baseline resistance to FQs due to irrational use of the drug.