Intravesical BCG: A Double-Edged Sword? The Untold Story of Infection Risks

Background and Objectives: Intravesical Bacillus Calmette-Guérin (BCG) therapy remains a cornerstone in the treatment of non-muscle-invasive bladder carcinoma due to its efficacy in reducing recurrence and progression rates. However, its use is associated with various complications—including urinary tract infections (UTIs)—which necessitates further exploration. This study aims to analyze UTIs occurring during intravesical BCG treatment, emphasizing the microbial spectrum, resistance patterns, and risk factors from an infectious diseases and clinical microbiology perspective. Materials and Methods: A retrospective analysis was conducted on 240 patients diagnosed with non-muscle-invasive bladder carcinoma who received intravesical BCG therapy between 2010 and 2021. Data were collected from hospital records, including demographic characteristics, comorbidities, number of intravesical BCG cycles, and microbiological findings. UTIs were classified based on susceptibility patterns, and statistical analyses were performed to determine associations between clinical variables and UTI risk. Results: UTIs developed in 39.1% (n = 94) of patients, with 25.8% (n = 62) caused by susceptible pathogens and 13.3% (n = 32) by resistant pathogens. The most common causative agent was Escherichia coli (80.7% in susceptible UTIs, 43.8% in resistant UTIs), followed by Pseudomonas aeruginosa and Klebsiella pneumoniae. The presence of diabetes mellitus and chronic kidney disease significantly increased the risk of developing a UTI (p < 0.05). A higher number of intravesical BCG cycles correlated with increased UTI occurrence (p < 0.001). Serum C-reactive protein (CRP) levels were significantly elevated in patients with resistant UTIs, while procalcitonin levels were not a reliable predictor of UTI occurrence. Conclusions: Intravesical BCG therapy is associated with a significant incidence of UTIs, particularly among patients with predisposing comorbidities. The increasing prevalence of antibiotic-resistant infections underscores the need for careful monitoring and targeted antimicrobial stewardship strategies. CRP may serve as a useful adjunctive marker for UTI diagnosis in this setting. Future studies should focus on optimizing infection control measures and refining diagnostic criteria to differentiate between BCG-related inflammation and infectious complications. © 2025 by the authors.