Low rate of fluoroquinolone resistance in Mycobacterium tuberculosis isolates from northern Tanzania

Abstract

Fluoroquinolones are used in second-line treatment of tuberculosis (TB) and have a potential role in shortening TB treatment duration. The wide use of fluoroquinolones in the treatment of other infections, including respiratory tract infections in patients with (undiagnosed) active TB, could result in fluoroquinolone-resistant Mycobacterium tuberculosis. We determined the rate of fluoroquinolone resistance in M. tuberculosis isolates obtained from Tanzanian patients and linked this to previous fluoroquinolone exposure and mycobacterial resistance to rifampicin and isoniazid. A total of 291 M. tuberculosis isolates were obtained between April 2009 and June 2010 from patients with smear-positive pulmonary TB and tested for susceptibility to ciprofloxacin, moxifloxacin, rifampicin and isoniazid. Information on previous fluoroquinolone use was obtained by interviewing patients and checking their medical files. Only 2 (0.7%) of the 291 M. tuberculosis isolates were resistant to ciprofloxacin; 1 of which was intermediately resistant to moxifloxacin as well. These two isolates were susceptible to rifampicin and isoniazid. Twenty-two (8%) of the 291 patients had a history of fluoroquinolone use (median: 7 days; interquartile range: 5-10 days). The patients from whom the fluoroquinolone-resistant M. tuberculosis isolates were obtained had no known history of previous fluoroquinolone use. Our findings indicate that the rate of fluoroquinolone-resistant M. tuberculosis in Tanzanian patients with TB is low and not related to previous, brief episodes of exposure to fluoroquinolones. The findings favour future application of fluoroquinolones in TB treatment regimens of shorter duration.