Impact of antimicrobial exposure on bronchoscopy yields in immunocompromised patients: a single-centre experience

Bronchoscopy with bronchoalveolar lavage (BAL) is an important diagnostic tool for pulmonary infections in immunocompromised hosts (ICH). However, the effect of pre-procedural antimicrobial exposure on BAL yield remains uncertain. Our study aimed to evaluate associations between pre-bronchoscopy antimicrobial exposure and BAL microbiological yield.

We analysed data from a prospective registry of immunocompromised patients undergoing bronchoscopy with BAL at a tertiary hospital between May 2021 and May 2024. Positive BAL yield was defined as positive bacterial or fungal culture, viral polymerase chain reaction (PCR), or BAL galactomannan (GM) >0.5. Associations between antimicrobial exposure and BAL yield were analysed.

A total of 113 bronchoscopies were performed in 107 ICH. Prior to bronchoscopy, 85% had received antibiotics, 41.6% antivirals, and 26.5% antifungals. BAL yielded at least one positive result in 76.1% of procedures, including bacterial cultures (23.0%), fungal cultures (67.3%), viral PCR (27.4%), and GM >0.5 (15.0%). Prophylactic antibiotics [odds ratio (OR) 0.168, 95% confidence interval (CI): 0.037-0.762, P=0.01] and empiric antibiotics ≥24 h (OR 0.262, 95% CI: 0.100-0.687, P=0.005) were associated with reduced bacterial culture yield. Prophylactic antifungal exposure reduced fungal culture yield (OR 0.206, 95% CI: 0.073-0.584, P=0.002). Conversely, antiviral exposure increased odds of positive viral PCR (OR 2.997, 95% CI: 1.274-7.051, P=0.01), while empiric antifungals ≥48 h increased odds of positive GM (OR 9.538, 95% CI: 1.915-47.505, P=0.01).

Pre-bronchoscopy exposure to antibiotics and antifungals was associated with reduced bacterial and fungal yields respectively, supporting the value of early BAL. Viral PCR and GM assays remained informative despite antimicrobial exposure. The perceived reduction in yield should be weighed against the persistent diagnostic utility of BAL, especially for viral and fungal pathogens.