The authors of this research note that urinary catheterisation is associated with a duration-dependent increased risk of bacteriuria and symptomatic urinary tract infection (UTI). It is unclear whether administration of prophylactic antibiotics when the catheter is removed will prevent subsequent symptomatic UTI; randomised controlled trials have yielded conflicting results and consensus recommendations differ.
A systematic search of the literature was conducted to identify any randomised or non-randomised studies comparing antibiotic prophylaxis to placebo/control at the time of removal of a short-term (≤14 days) urinary catheter, with symptomatic UTI (detection of measureable bacteriuria plus the presence of at least one symptom or sign compatible with UTI) as an endpoint.
A total of seven studies met the inclusion criteria – six RCTs (one unpublished) and one non-randomised controlled study. Results were mixed – three reported antibiotic prophylaxis to be associated with lower incidence of UTI, whereas the others did not report any benefit. The quality of the studies however varied and the authors note that the risk of selection and attrition bias was high in most. Specifically, randomisation and allocation were considered to be inadequate in four. Studies were heterogeneous in the type (trimethoprim/sulfamethoxazole, ciprofloxacin, nitrofurantoin, and a cephalosporin) and duration (single dose to three day course) of antimicrobial prophylaxis and the period of observation.
The results of the meta-analysis indicated that antibiotic prophylaxis was associated with an overall reduction in symptomatic UTI compared with controls (risk ratio of 0.45; 95% CI 0.28 to 0.72). The absolute reduction was 5.8%, with a number needed to treat (NNT) of 17 (95% CI 12-30). Heterogeneity was low (I2=16%).
Results were similar when the non-randomised study and the unpublished trial were excluded from the analysis, and when the analysis was limited to the five studies conducted with surgical patients. However when the results of the two studies in mixed hospital populations were analysed, no significant advantage of antimicrobial prophylaxis was seen (risk ratio 0.44; 95% CI 0.02 to 9.40). The funnel plot suggested some publication bias, but this is difficult to interpret based on the small number of included studies. Only two of the studies recorded information on adverse events associated with the antibiotics, and none looked at the costs of antibiotic prophylaxis or emerging antimicrobial resistance.
The authors caution that the possible publication bias toward positive studies, the limitations of the included studies, and practical considerations about encouraging more widespread antibiotic use should be considered when interpreting the positive overall results of the meta-analysis. Further studies should aim to identify specific populations at risk of developing symptomatic UTIs who would be potential targets for antimicrobial prophylaxis.