A study of urine cultures in Switzerland found that pathogens that cause catheter-associated urinary tract infections (CAUTIs) were more frequently resistant to antibiotics than non-CAUTI pathogens, researchers reported yesterday in Antimicrobial Stewardship & Healthcare Epidemiology.
For the study, a team of Swiss researchers analyzed all urine cultures from 2019 submitted to the Swiss Centre for Antibiotic Resistance. They conducted antimicrobial susceptibility tests and compared proportions of bacterial species and antibiotic-resistant isolates in CAUTIs, which are considered complicated UTIs and are generally treated with fluoroquinolone antibiotics, and non-CAUTI samples.
The aim of the study was to clarify whether urinary pathogens and antibiotic resistance vary depending on catheter association, which could help clinicians with empiric antibiotic therapy choices.
Among the 27,158 urine cultures that met the inclusion criteria, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Proteus mirabilis represented 70% and 85% of pathogens identified in CAUTI and non-CAUTI samples, respectively. The most relevant difference concerned P aeruginosa, which represented 10% of CAUTI pathogens versus 3.3% of non-CAUTIs. The overall resistance rate for the often empirically prescribed antibiotics ciprofloxacin, norfloxacin, and trimethoprim-sulfamethoxazole was between 13% and 31%.
Except for nitrofurantoin, E coli from CAUTI samples were more often resistant to all classes of antibiotics analyzed, including third-generation cephalosporins (used as a surrogate for extended-spectrum β-lactamase, or ESBL, production). Significantly higher resistance proportions in CAUTI samples versus non-CAUTI samples were observed for ciprofloxacin and norfloxacin in K pneumoniae, for norfloxacin in P mirabilis, and for cefepime and piperacillin-tazobactam in P aeruginosa.
Given the large sample size of isolates, the study authors say they believe their findings are representative of the current ecology of urinary pathogens in Switzerland.
"This finding emphasizes the need for urine sampling for culturing before initiating therapy for CAUTI and the importance of considering therapeutic alternatives," they concluded.