Compliance with new drug use and the effect of discrepant drug susceptibility testing on MDR/RR-TB treatment.

BACKGROUND: Following the WHO???s announcement in 2018, the use of new drugs was recommended for all patients with multidrug-resistant TB (MDR-TB) in Korea. This study aimed to evaluate adherence to new anti-TB drug regimens and implementation of molecular drug susceptibility testing (mDST) in Korea.METHODS: Nationwide, 560 patients were reported as having MDR-TB in 2021. The implementation of mDST and new anti-TB drug use were analysed. The discrepancy between mDST and phenotypic DST (pDST) results and their implications on the use of new anti-TB drugs were also analysed. The use of novel anti-TB drugs has been approved by the National TB Expert Committee.RESULTS: The non-adherence rate in MDR-TB patients was 14.3%. The mDST implementation rate was 96.1%. Of the 459 patients who underwent both mDST and pDST, the discordance rate for rifampicin (RIF) resistance was 22.6% (n = 104), of which 72.1% (n = 75) were resistant on mDST but susceptible on pDST. The discrepancy in mDST and pDST results related to RIF resistance was found to be the main cause of non-adherence to new drug regimen.CONCLUSION: Comprehensive training on how to interpret conflicting results between mDST and pDST could enhance the utilisation of new drugs in the treatment of MDR/RIF-resistant TB.

Treatment outcomes in multidrug-resistant tuberculosis according to pyrazinamide susceptibility.

BACKGROUND: Pyrazinamide (PZA) is an important anti-tuberculosis drug for multidrug-resistant tuberculosis (MDR-TB). However, PZA has recently been demoted within the hierarchy of TB drugs used for MDR-TB.METHODS: We conducted a retrospective cohort study to investigate treatment outcomes for simple MDR-TB (susceptible to both second-line injectable drugs and fluoroquinolones) according to PZA susceptibility.RESULTS: Among 216 pulmonary MDR-TB patients included in the study, 68 (31.5%) were PZA-resistant (PZA-R). The mean age was 41.8 years, and 63.4% were male. Baseline characteristics such as comorbidity, previous TB history, acid-fast bacilli (AFB) smear positivity and cavitation were similar in PZA-susceptible (PZA-S) and PZA-R patients. The number of potentially effective drugs was slightly higher among PZA-S patients than among the PZA-R (5.1 vs. 4.8, respectively; P = 0.003). PZA was more frequently used in PZA-S patients (73.0%) than in the PZA-R (14.7%), while para-aminosalicylic acid was more frequently used in PZA-R than in PZA-S patients (76.5% vs. 50.7%). The treatment success rate was similar in PZA-S (77.7%) and PZA-R (75.0%) patients. PZA resistance was not associated with treatment success in multivariate analysis.CONCLUSIONS: PZA-resistant simple MDR-TB patients had the same treatment success rate as the PZA-susceptible group even without using novel anti-TB drugs.

Treatment outcomes and moxifloxacin susceptibility in ofloxacin-resistant multidrug-resistant tuberculosis.

SETTING: A tertiary referral centre in Seoul, South Korea. OBJECTIVE: To investigate the effect of moxifloxacin (MFX) susceptibility and later-generation fluoroquinolone (FQ) use on the treatment outcomes of ofloxacin (OFX) resistant multidrug-resistant tuberculosis (MDR-TB). DESIGN: Of 223 patients diagnosed with MDR-TB between January 2006 and December 2012, 70 (31.4%) patients with OFX-resistant MDR-TB were enrolled in this retrospective cohort study. Their treatment outcomes were analysed. RESULTS: The mean age (standard deviation) of the 70 patients was 40.6 (12.9) years; 43 (61.4%) were male and 26 (37.1%) had extensively drug-resistant TB. Of the 70 patients, 22 (31.4%) had MFX-susceptible TB, while the remaining 48 (68.6%) were MFX-resistant. The MFX-susceptible and -resistant groups were comparable in terms of baseline characteristics (including age, sex and radiological severity), and respectively 90.9% (20/22) and 70.8% (34/48) were treated with later-generation FQ-containing regimens (P = 0.074; mainly MFX [40/54, 74.1%]). Treatment success was achieved in 72.7% (16/22) of the MFX-susceptible patients and in 41.7% (20/48) of the MFX-resistant patients (P = 0.021). Treatment failure was significantly higher in the MFX-resistant group (41.7% [20/48] vs. 9.1% [2/22]; P = 0.006). CONCLUSION: Patients with OFX-resistant MDR-TB had significantly better treatment outcomes when susceptible to MFX. This probably reflects the effect of later-generation FQ treatment.

Diagnostic sensitivity of culture and drug resistance patterns in Korean patients with intestinal tuberculosis.

SETTING: It is challenging to differentiate between intestinal tuberculosis (ITB) and Crohn's disease in areas where TB is still prevalent. The use of diagnostic tools and verifying the drug resistance patterns of ITB can be helpful for its correct diagnosis. OBJECTIVE: To determine the diagnostic sensitivity of a culture assay using colonoscopic biopsy specimens and the drug resistance patterns of Mycobacterium tuberculosis isolated from ITB. DESIGN: Data from 400 patients diagnosed with ITB were retrospectively analysed. RESULTS: Of the 400 patients, 170 (42.5%) were males; the median age at diagnosis was 40 years. The sensitivity of culture was 44.1% (145/329). Resistance to at least one anti-tuberculosis drug was identified in 13 (17.6%) and multidrug-resistant TB (MDR-TB) was diagnosed in two (2.7%) of the 74 patients for whom drug susceptibility testing was performed. Including M. tuberculosis isolated from respiratory specimens, the proportion of MDR-TB was 4.4% (5/113); previous anti-tuberculosis treatment was an independent risk factor for MDR-TB (26.7% vs. 1.0%, P < 0.01). CONCLUSION: Culture of colonoscopic biopsy specimens shows substantial diagnostic sensitivity; the frequency of MDR-TB is higher in previously treated cases than in new cases.