A retrospective cohort study of Mycobacterium kansasii complex pulmonary infections at a tertiary teaching hospital

Background: Mycobacterium kansasii complex (MKC) is the second common slowly growing mycobacterium associated with pulmonary diseases, typically presenting as chronic, progressive respiratory symptoms with structural lung damage. This study aimed to identify the prognostic factors, genotypes, antimicrobial susceptibility, and treatment outcomes in patients with MKC pulmonary disease (MKC-PD). Methods: This retrospective cohort study of patients with MKC-PD from January 2016 to August 2021 was conducted at Linkou Chang Gung Memorial Hospital in Taiwan. Diagnosis was based on the 2020 American Thoracic Society/European Respiratory Society/European Society of Clinical Microbiology and Infectious Diseases/and Infectious Diseases Society of America criteria. Medical records were reviewed for demographic data, antimycobacterial agents, and treatment outcomes. Speciation was based on heat-shock protein 65 (hsp65) or Tu elongation factor (tuf) gene sequencing for MKC. Antimicrobial susceptibility was determined using Sensititre RAPMYCO2 broth microdilution. Results: A total of 202 isolates, one from each patient, were included in the analysis. Sixty-six patients did not meet the diagnostic criteria for MKC-PD, and 71 underwent clinical monitoring without antimycobacterial therapy. Of 65 treated patients, 30 (46.2 %) achieved treatment success, whereas 35 (53.8 %) were categorized as treatment failure. Logistic regression analysis identified age, body mass index (BMI), and treatment duration as significant predictors of treatment outcomes. Of 33 rifampin-resistant strains, 21(63 %) were identified as Mycobacterium persicum. Conclusions: In this cohort of patients with MKC-PD, treatment outcomes were significantly associated with age, BMI, and treatment duration. These findings underscored the importance of early individualized risk stratification to improve treatment outcomes in MKC-PD.