Population-level and longitudinal MIC distributions for antimicrobials against drug-resistant Mycobacterium tuberculosis in Wuxi, a low-epidemic city in China, from 2019 to 2023.

BACKGROUND

Drug-resistant tuberculosis (DR-TB) remains a significant global health challenge, with increasing resistance to both first- and second-line anti-tuberculosis drugs. Understanding the demographic distribution, temporal trends, and resistance profiles of DR-TB is essential for improving treatment strategies and public health interventions.

OBJECTIVE

This study aimed to examine the demographic characteristics, temporal distribution, and minimum inhibitory concentration (MIC) patterns of drug-resistant Mycobacterium tuberculosis (M. tuberculosis) isolates in a retrospective cohort of patients with culture-confirmed DR-TB from August 2019 to July 2023.

METHODS

A total of 402 drug-resistant M. tuberculosis isolates from clinical patients were included in this study for the analysis of MIC distributions and resistance trends over time. The study included four DR-TB categories: isoniazid-resistant TB, RR-TB, MDR-TB, and pre-XDR-TB. No XDR-TB cases were identified. The temporal distribution of cases was analyzed for seasonal trends, and MIC values were assessed for anti-tuberculosis drugs. A longitudinal analysis was conducted to observe variations in MICs over time. Specifically, a longitudinal comparison was performed on paired M. tuberculosis isolates from 49 patients, with isolates collected at intervals exceeding 4 weeks.

RESULTS

The majority of patients were male (72.14%), and the most common form of DR-TB was isoniazid-resistant TB (23.14%). The study found significant seasonal variation, with higher DR-TB incidence in winter and spring months, and the temporal distribution was affected by COVID-19. Resistance rates were highest for isoniazid (40.30%), cycloserine (47.76%), and para-aminosalicylic acid (52.24%). Across the DR-TB cohorts, MICs for isoniazid, ethionamide, para-aminosalicylic acid, and amikacin demonstrated a significant upward trend, whereas a declining pattern was observed for ethambutol. The longitudinal comparison of paired M. tuberculosis isolates from 49 patients, demonstrated a marked elevation in the MICs for all 12 antimicrobials over the course of treatment.

CONCLUSION

This study highlights the increasing burden of DR-TB, with increasing MICs and relatively high resistance rates for a few key drugs indicating reduced drug susceptibility over time. The increasing MICs highlight the need for continuous resistance monitoring and enhanced DR-TB control efforts.