B69-12 Heteroresistance and Clinical Characteristics of Pulmonary and Extrapulmonary Multisite Tuberculosis

Abstract Rationale Heteroresistance refers to the phenomenon where different subpopulations of Mycobacterium tuberculosis (MTB) show varying resistance to the same antimicrobial agent, potentially leading to treatment failure and recurrence. This study aimed to analyze heteroresistance patterns in pulmonary and extrapulmonary multisite tuberculosis (TB) cases , providing experimental data for further exploration of MTB resistance mechanisms. Methods Data were collected from TB cases with pulmonary and extrapulmonary multisite infections. Inclusion criteria were cases with liquid cultures from multiple specimen types, all positive within one month. Clinical information was gathered, and bacterial DNA was extracted using the cetyltrimethylammonium bromide (CTAB) method. Whole genome sequencing (WGS) was performed, and drug susceptibility to 12 antibiotics was determined using the microdilution method. Results A total of 119 patients and 251 specimens were included: 196 pulmonary and 55 extrapulmonary TB. Of the 251 bacterial isolates, 194 strains from 94 patients underwent WGS. Analysis revealed that 67 cases (72.82%) had 141 clustered strains. Drug susceptibility testing was performed on 120 strains from 58 clustered TB cases. Of these, 38 cases (65.52%) showed consistent drug susceptibility results across specimens, while 20 cases (34.48%) showed heteroresistance with a ≥ 2-fold MIC difference. Heteroresistance was observed for the following drugs: isoniazid(11.94%), moxifloxacin (11.94%) , rifabutine (5.97%), ofloxacin (5.97%), cycloserine (5.97%), ethambutol (4.48%), kanamycin (2.99%), para-aminosalicylic acid(2.99%), and streptomycin(2.99%), ethionamide (1.49%),rifampin(1.49%). Mutations in resistance genes were found in 12 cases (60.00%), including those associated with rifampin, rifabutine, and streptomycin. Clinically, heteroresistance cases were significantly younger than those with homogenous resistance (31 vs. 52 years, P < 0.01) and had less stable outcomes (stability rate: 5% vs. 31.58%, P < 0.05). Conclusion Heteroresistance is present in pulmonary and extrapulmonary multisite TB patients. Mutations in resistance-related genes may or may not occur in heteroresistant strains. Patients with heteroresistance tend to be younger and experience more unstable clinical courses, highlighting the need for careful clinical monitoring. This abstract is funded by: None