Canadian Patterns of Antimicrobial Resistance: Overview of Current Trends Related to Hospital Pathogens

Selection of appropriate empirical antibiotic therapy is dependent onmany factors, not the least of which is an understanding of antimicrobialresistance rates in the patient population that is undergoing treatment.Resistance rates may vary by geographical location, institution,hospital ward or unit, and even body site of infection. The presentpaper reviews the currently available Canadian data regarding resistancerates for some of the most common hospital-acquired pathogens,including Escherichia coli, Klebsiella species, Pseudomonas aeruginosa,Enterobacter species, Staphylococcus aureus and Enterococcus species.Current data suggest that the rates of extended-spectrum beta-lactamasesamong E coli and Klebsiella species remain relatively low acrossCanada. There are very little data on the epidemiology of ampCcephalosporinases among Gram-negative organisms, although combinedAmerican and Canadian data suggest that ceftazidime resistancerates for Enterobacter species range from 17.1% to 24.8%. Theincreased use of fluoroquinolones has led to an increase in resistancerates among most Gram-negative organisms. In the late 1990s,ciprofloxacin resistance rates for P aeruginosa were reported to beapproximately 20%. For the Gram-positive organisms, methicillinresistance rates for S aureus have been reported to be as high as 10%and vancomycin resistance rates for Enterococcus species have beenreported to be less than 1%. Additional data that are representative ofall regions of Canada are needed. Continued surveillance, antibioticstewardship, and adherence to good infection prevention and controlmeasures will lead to a better understanding of the epidemiology ofantimicrobial resistance in Canadian hospitals, as well as help to controlits spread.