In vitro activity of 19 antimicrobial agents against 3513 nosocomial pathogens collected from 48 Canadian medical centres. The Canadian Antimicrobial Study Group.

Antimicrobial resistance is a global concern. Differentiation between susceptibility rates for nosocomial versus community pathogens is important epidemiologically because it impacts on the appropriate empirical selection of antimicrobial therapy for infected patients. We studied resistance rates for 3513 nosocomial pathogens from 48 Canadian medical centres tested against 19 antimicrobial agents. The following are percent susceptibility for ceftazidime, ceftriaxone, ciprofloxacin, imipenem, netilmicin, and ticarcillin/clavulanic acid, respectively: Enterobacteriaceae 95, 95, 97, 99 98, 89; Escherichia coli, all 99 except ticarcillin/clavulanic acid (91); Enterobacter spp. 78, 78, 96, 99, 99, 71; Citrobacter spp. 79, 80, 89, 100, 94, 73; Proteus spp. 99, 88, 99, 88, 99, 98; Pseudomonas aeruginosa 88, 20, 82, 88, 81, 36; Staphylococcus aureus, all > 95; Enterococcus spp. 4, 9, 62, 95, 43, 38. Susceptibility rates for other species of microorganisms and agents tested varied considerably. Some institutions had higher than average resistance rates for some pathogens (i.e. P. aeruginosa) and some agents. Detection and continued surveillance of antimicrobial resistance amongst nosocomial pathogens is vital to patient care and health care resources. The control of antimicrobial resistance can help maintain antibiotic usage and costs associated with the use of ever more potent drugs and the treatment of increasingly resistant infections.