title: Cumulative Antimicrobial Susceptibility Data from Intensive Care Units at One Institution: Should Data Be Combined?
abstract: Cumulative susceptibility test data (CSTD) are used to guide empirical antimicrobial therapy and to track trends in antibiotic resistance. The Clinical and Laboratory Standards Institute recommends reporting CSTD at least annually and sets the minimum number of isolates per reported organism at 30. To comply, many hospitals combine data from multiple intensive care units (ICUs); however, this may not be appropriate to guide empirical therapy because of variations in patient populations. In this study, susceptibility data for two different ICUs at a tertiary care hospital in Toronto, Canada, were used to create a traditional CSTD report, which combined data from different ICUs, and a rolling-average CSTD report, which pooled 2 years of data for each ICU separately. For simplicity, data for only the most common Gram-negative organisms (Escherichia coli,Pseudomonas aeruginosa) and the most relevant antibiotics (ciprofloxacin, piperacillin-tazobactam) were examined. With the rolling-average method, significant differences in susceptibility were seen between the ICUs in 50% of the organism-antimicrobial combinations. Furthermore, the 3% median year-over-year difference in susceptibilities seen for the 16 organism-antibiotic combinations by using the traditional method was lower than the 14% median difference seen for the 20 between-ICU within-year comparisons obtained using the rolling-average method. Changes in our selection of empirical antibiotics resulted from this revised approach, and our results suggest that pooling data from ICUs with different patient populations may not be appropriate. A rolling-average method may be an appropriate strategy for the creation of individual-unit CSTD reports.
authors.affiliation: Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada.
authors.forename: Aaron
authors.initials: A
authors.lastname: Campigotto
authors.affiliation: Division of Infectious Diseases, Department of Medicine, St. Michael's Hospital, Toronto, ON, Canada Department of Medicine, University of Toronto, Toronto, ON, Canada.
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Muller
authors.affiliation: Division of Infectious Diseases, Department of Medicine, St. Michael's Hospital, Toronto, ON, Canada Department of Medicine, University of Toronto, Toronto, ON, Canada.
authors.forename: Linda R
authors.initials: LR
authors.lastname: Taggart
authors.affiliation: Department of Pharmacy, St. Michael's Hospital, Toronto, ON, Canada.
authors.forename: Reem
authors.initials: R
authors.lastname: Haj
authors.affiliation: Department of Pharmacy, St. Michael's Hospital, Toronto, ON, Canada.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Leung
authors.affiliation: Division of Microbiology, Department of Laboratory Medicine, St. Michael's Hospital, Toronto, ON, Canada.
authors.forename: Jeya
authors.initials: J
authors.lastname: Nadarajah
authors.affiliation: Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada Division of Infectious Diseases, Department of Medicine, St. Michael's Hospital, Toronto, ON, Canada Division of Microbiology, Department of Laboratory Medicine, St. Michael's Hospital, Toronto, ON, Canada matukasl@smh.ca.
authors.forename: Larissa M
authors.initials: LM
authors.lastname: Matukas
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D001419:Bacteria / Q000187:drug effects* / Q000302:isolation & purification; D001424:Bacterial Infections / Q000188:drug therapy / Q000382:microbiology; D002170:Canada; D003627:Data Interpretation, Statistical; D024881:Drug Resistance, Bacterial; D006801:Humans; D007362:Intensive Care Units; D008826:Microbial Sensitivity Tests; D062606:Tertiary Care Centers
chemical_list: D000900:Anti-Bacterial Agents