[Bacteriuria in patients with indwelling urinary catheters-when and how to treat? : Diagnosis, prevention and treatment of catheter-associated urinary tract infections].

Catheter-associated urinary tract infection (CAUTI) represents one of the most common healthcare-associated infections. In patients with indwelling urinary catheters, bacterial colonization frequently occurs in nearly all patients and increases with the duration of catheterization. A crucial clinical challenge is the differentiation between catheter-associated asymptomatic bacteriuria (CA-ABU) and symptomatic local or systemic catheter-associated urinary tract infection (L- or S‑CAUTI). While CA-ABU in general does not require treatment, CAUTIs should be treated appropriately. The pathogenesis is largely determined by microbial biofilm formation on the catheter surface. Biofilms facilitate persistent bacterial colonization and contribute to reduced susceptibility to antimicrobial agents. The microbial spectrum commonly includes Enterobacterales such as E. coli, Klebsiella spp. and Proteus spp. as well as Enterococcus species with an increasing number of multidrug-resistant species. Major risk factors include the duration of catheterization, frequent manipulation of the drainage system, insufficient hygiene, and patient-related factors such as advanced age, comorbidities, immunosuppression, and diuresis. Prevention strategies therefore focus primarily on avoiding unnecessary catheterization, short duration of catheterization, and implementing standardized catheter care protocols. In cases of suspected CAUTI, urinalysis and urine culture should be performed, ideally after catheter replacement. Antibiotic therapy should be guided by clinical severity (local or systemic infection), local resistance patterns, and microbiological findings. Catheter removal or replacement should be considered. The overall goal is effective infection control while minimizing unnecessary antibiotic use to reduce antimicrobial resistance.