Predictive value of in vitro antimicrobial susceptibility testing for outcomes of Burkholderia cepacia complex infection: a single-center retrospective study.

INTRODUCTION: With the Clinical and Laboratory Standards Institute (CLSI) progressively removing interpretive breakpoints for Burkholderia cepacia complex (Bcc), clinicians face growing uncertainty in selecting antimicrobial therapy. This study evaluated 10-year local trends in Bcc antimicrobial susceptibility and assessed whether in vitro antimicrobial susceptibility testing (AST) retains independent prognostic value for clinical outcomes in the absence of contemporary standardized breakpoints. METHODS: This single-center retrospective study included 47 patients treated at Peking Union Medical College Hospital between 2014 and 2024, in whom Bcc was microbiologically identified and clinically confirmed as the sole causative pathogen. RESULTS: Among the 47 patients with monomicrobial Bcc infection (27 bloodstream and 20 respiratory tract infections), the median age was 62 years and 85% had underlying comorbidities. Over the 10-year period, Bcc isolates maintained high and stable in vitro susceptibility to trimethoprim-sulfamethoxazole (95.6%), minocycline (95.7%), and ceftazidime (91.1%). However, in vitro susceptibility to these agents was not an independent predictor of clinical outcome (all p > 0.05). Older age was the only independent risk factor for unfavorable clinical outcomes (Firth regression: all p < 0.05; Bayesian: posterior mean = -0.15, 95% CI: -0.27 to -0.06; OR = 0.86, 95% CI: 0.76 to 0.94). CONCLUSION: Although Bcc isolates remained highly susceptible to first-line agents, in vitro AST results alone were insufficient to predict clinical outcomes, which were driven predominantly by host factors, particularly advanced age. In the absence of current CLSI breakpoints, AST results should be interpreted cautiously and integrated with host risk assessment, source control, and overall clinical status rather than used in isolation.