Additional benefits of GeneXpert MTB/RIF assay for the detection of pulmonary tuberculosis patients with prior exposure to fluoroquinolones.

Background: We performed a prospective study to investigate the association between pre-diagnosis exposure to fluoroquinolone (FQ) and laboratory testing results among tuberculosis (TB) patients.

Patients and methods: Each TB-suspected patient provided sputum specimen for mycobacteria growth indicator tube (MGIT) culture and GeneXpert among pulmonary TB patients. Confirmed TB patients and clinically diagnosed TB patients were further enrolled in the final analysis.

Results: A total of 661 TB patients were included in the final analysis. The distribution of rural TB patients in the FQ-exposed group was significantly higher than that of urban TB patients ( P =0.02). GeneXpert showed significantly better positive rate than MGIT technology for TB cases with prior FQ exposure (30.6% for GeneXpert vs 20.1% for MGIT, P =0.01). The positive rate of GeneXpert was significantly higher than that of MGIT for 7-13 days ( P =0.04) and ≥14 days FQ exposure ( P =0.01) groups, respectively. We also found that the positive rate of MGIT was significantly decreased from 31.5% for <7 days levofloxacin (LFX) exposure group to 9.4% for ≥14 days LFX exposure group ( P =0.01), whereas the positive rate of MGIT displayed significant decrease after 7-13 days exposure to moxifloxacin ( P =0.04).

Conclusion: In conclusion, our data demonstrate that TB patients prior to sputum collection are prone to yield negative culture results. GeneXpert could bring additional benefits for the detection of pulmonary TB patients with prior exposure to FQs. In addition, the exposure to moxifloxacin affected mycobacterial culture at an earlier stage compared with LFX.