Comparison of pathogens and their antimicrobial resistance patterns in paediatric, adult and elderly patients in Canadian hospitals.

The purpose of this study was to describe the association between age groups and antimicrobial resistance in the most commonly identified pathogens in Canadian hospitals. Between 2007 and 2011, 27123 clinically significant isolates, comprising 3580 isolates from children 18 years old, 12119 isolates from adults 1964 years old and 11424 isolates from elderly patients aged 65 years old, were collected as part of the CANWARD surveillance study from tertiary-care centres across Canada. Antimicrobial susceptibility testing was performed according to CLSI guidelines. A multifactorial logistic regression model was used to determine the impact of demographic factors, including age groups, on antimicrobial resistance. Staphylococcus aureus, Escherichia coli, Streptococcus pneumoniae and Pseudomonas aeruginosa were in the top five organisms for all of the age groups. The proportions of S. aureus that were methicillin resistant, enterococci that were vancomycin resistant and E. coli that produced extended-spectrum -lactamases were 11.2, 0.7 and 1.0 for children, 22.8, 4.6 and 4.3 for adults, and 28.0, 3.8 and 4.9 for the elderly, respectively. Notable age-related differences in antimicrobial resistance patterns included the following: significantly less methicillin, clindamycin, clarithromycin and trimethoprim/sulfamethoxazole resistance in S. aureus from children; for E. coli, higher cefazolin and ciprofloxacin resistance in the elderly and less ceftriaxone, ciprofloxacin and gentamicin resistance in isolates from children; more S. pneumoniae isolates with penicillin MICs 1 mg/L in children; and for P. aeruginosa, higher resistance rates for meropenem, ciprofloxacin and levofloxacin in adults. The assessment of antimicrobial susceptibility patterns by age group revealed that resistance rates are often higher in the older age groups; however, considerable variability in age-specific resistance trends for different pathogenantimicrobial combinations was noted.