Bacterial epidemiology and antimicrobial resistance profiles of urinary specimens of the elderly

Although urinary tract infections are the second leading cause of infections among patients aged above 65 years, data on bacterial epidemiology of urinary specimens in these patients is scarce. Our aim was to describe the main bacterial species found at significant levels in urine specimens of the elderly and to determine their antimicrobial resistance profiles.

From October 2012 to October 2015, all urinary specimens (catheter-related or not) received at the laboratory of microbiology of the university hospital of Caen (France) were retrospectively studied. Results were compared to those of urinary specimens of patients aged 18-64 years. Bacterial identification was performed using MALDI-TOF mass spectrometry and antimicrobial susceptibility testing was performed as per CA-SFM guidelines.

Out of 33,302 urine cytobacteriological examinations (UCBE) performed in patients aged above 65 years, 13,450 microorganisms were identified. Escherichia coli was the most frequent species (41.8%) followed by Enterococcus faecalis (9.7%), Pseudomonas aeruginosa (5.7%), Proteus mirabilis (4.6%), and Klebsiella pneumoniae (4.2%). Around 9% of E. coli isolates were resistant to third-generation cephalosporins, including 8.2% by production of extended-spectrum β-lactamase (ESBL). This prevalence was significantly higher than that observed in urinary specimens of patients aged 18-74 years (4.9%, P<0.001).

The bacterial epidemiology of urines collected from the elderly is diverse and significantly different from that of urine specimens of younger patients, with a higher proportion of multidrug-resistant bacteria (particularly ESBL-producing E. coli).