Nosocomial bacteriuria in elderly inpatients may be leading to considerable antibiotic overuse: an audit of current management practice in a secondary level care hospital in New Zealand

BACKGROUND: Bacteriuria in the form of symptomatic urinary tract infection (UTI) and asymptomatic bacteriuria (ASB) is common in the elderly. There is no clinical benefit obtained by treating elderly individuals with ASB. However, its high prevalence leads to the overdiagnosis of UTI and unnecessary antibiotic use, which can result in adverse events, including Clostridium difficile diarrhea and reinfection with antibiotic-resistant organisms. METHODS: This was a retrospective audit that assessed the management of nosocomial bacteriuria in elderly patients admitted to the over-65 years rehabilitation unit of a secondary level care hospital in New Zealand. Identified bacteriuria episodes had the timing of sample collection relative to admission, microbial etiology, antibiotic susceptibility profile, inflammatory marker level, and treatment determined. Episodes were classified into six different clinical groups based on the presence or absence of signs and symptoms, urinary catheter status, and systemic inflammatory response. The proportion of bacteriuria episodes by clinical grouping and the level of treatment by clinical group were determined, followed by assessment of the amount of overtreatment in terms of the number of unnecessary antibiotic courses and unnecessary antibiotic treatment days. RESULTS: Significant bacteriuria was identified in 30% of patients, with 35% of urine samples collected in the immediate postadmission period. Fifty-four percent of the bacteriuria episodes were ASB or catheter-associated ASB (CA-ASB) without an inflammatory response, 24% were ASB or CA-ASB with raised inflammatory markers, and 22% were UTI or CA-UTI. The most common cause of bacteriuria was Escherichia coli, although the etiology was diverse, especially after prolonged hospitalization or in catheterized patients. A large proportion of organisms were resistant to one or more of the commonly used oral antibiotics. Treatment of ASB and CA-ASB accounted for 43% of all antibiotic courses received. Furthermore, treatment of ASB and CA-ASB combined with unnecessarily prolonged treatment days for clinically relevant infections accounted for 55% of all antibiotic treatment days received. CONCLUSION: The results suggest that inappropriate urine screening was occurring and that 43% of antibiotic courses and 55% of all antibiotic treatment days were unnecessary. Current practice is amenable to improvement by performing urine culture only when clinically indicated, focusing on clinical signs and symptoms to diagnose clinically significant UTI rather than a positive culture, and using, where possible, the ecologically least damaging antibiotic for the shortest duration required.