Resistance to first- and second-line antituberculosis drugs in Southern Taiwan: Implications for empirical treatment

Multidrug-resistant and extensively drug-resistant tuberculosis infections cause public health concerns worldwide. Local epidemiologic data about the drug resistance of Mycobacterium tuberculosis isolate (Mtb) is critical to guide appropriate empirical therapy to cure patients and restrain the spread of tuberculosis.

Antituberculosis susceptibility testing was performed for 287 Mtbs, including 63 MDR-Mtbs collected in southern Taiwan from 2011 to 2015. Tuberculosis patients were classified into newly diagnosed cases and previously treated cases based on patients' medical history.

Almost no resistance was found to the tested second-line antituberculosis drugs in non-MDR-Mtbs. Higher resistance rates to ethambutol, ofloxacin, and streptomycin were observed in MDR-Mtbs compared to non-MDR-Mtbs. Among 63 MDR-Mtbs, 61.9% of patients were newly diagnosed and 38.1% were previously treated cases. For MDR-Mtb, the drug-resistance rates in previously treated cases were significantly higher for ethambutol, pyrazinamide, ofloxacin, moxifloxacin, streptomycin, and p-aminosalicylic acid. When MDR-Mtbs are identified in previously treated cases, empirical administration of ethambutol, pyrazinamide, ofloxacin, or moxifloxacin may not provide effective treatment. The resistance rates to these drugs were all more than 50%. Furthermore, 25% of MDR-Mtbs from previously treated patients were resistant to p-aminosalicylic acid.

We observed almost no resistance to the tested second-line antituberculosis drugs among non-MDR-Mtbs. Anti-tuberculosis regimen with pyrazinamide, ethambutol, fluoroquinolone, kanamycin, cycloserine and p-aminosalicylic acid can be empirically used for newly diagnosed MDR-TB cases. For previously treated MDR-TB patients, empirical ethambutol, pyrazinamide, ofloxacin, or moxifloxacin may not provide effective treatment because the resistance rates to these drugs were all >50%.