title: Characterization of Acinetobacter baumannii and meropenem-resistant Pseudomonas aeruginosa in Canada: results of the CANWARD 2007-2009 study.
abstract: A total of 66 (0.35% of overall isolates) Acinetobacter baumannii and 102 (0.55%) meropenem-resistant Pseudomonas aeruginosa were identified among 18 538 isolates collected from medical centers across Canada during the 2007-2009 period. A. baumannii was most frequently recovered from patients in intensive care units (ICUs; 42.4%) and was isolated mostly from blood cultures (53.0%) and respiratory tract specimens (33.3%). Colistin, meropenem, and amikacin were the most active agents against A. baumannii strains (≥ 92.4% coverage). Gentamicin, levofloxacin, and tigecycline were also active against this bacterial species (MIC(50) 1, 0.12, and 0.5 μg/mL, respectively). Multidrug resistance (MDR; resistance to ≥ 3 antimicrobial classes) was noted in only 4 strains (6.1%), and molecular typing revealed 6 clusters of 2 isolates per cluster that displayed >85% similarity on the dendrogram. Meropenem-resistant P. aeruginosa isolates were primarily obtained from patients in ICUs (40.2%) and the most prevalent specimen types were those collected from the respiratory tract (63.7%), followed by blood cultures (18.6%). Most of the meropenem-resistant P. aeruginosa were resistant to all antimicrobial agents tested, and low susceptibility rates were observed for levofloxacin (8.8%) and gentamicin (28.4%). Amikacin and colistin were active against 67.7% and 88.2% of the isolates, respectively. A total of 68.6% (n = 70) of meropenem-resistant P. aeruginosa were MDR. Pulsed-field gel electrophoresis analysis revealed 94 unique isolates and 2 small clusters (6 and 4 isolates, 1 hospital each). In summary, MDR A. baumannii are rare in Canada and, conversely, meropenem-resistant P. aeruginosa were mostly MDR; however, there was minimal clonal spread among these nonfermentative bacilli.
authors.affiliation: National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada R3E 3R2.
authors.forename: Melissa
authors.initials: M
authors.lastname: McCracken
authors.forename: Laura F
authors.initials: LF
authors.lastname: Mataseje
authors.forename: Vivian
authors.initials: V
authors.lastname: Loo
authors.forename: Andrew
authors.initials: A
authors.lastname: Walkty
authors.forename: Heather J
authors.initials: HJ
authors.lastname: Adam
authors.forename: Daryl J
authors.initials: DJ
authors.lastname: Hoban
authors.forename: George G
authors.initials: GG
authors.lastname: Zhanel
authors.forename: Michael R
authors.initials: MR
authors.lastname: Mulvey
mesh_terms: D000151:Acinetobacter Infections / Q000188:drug therapy / Q000382:microbiology*; D040981:Acinetobacter baumannii / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D015373:Bacterial Typing Techniques; D002170:Canada; D002648:Child; D002675:Child, Preschool; D016172:DNA Fingerprinting; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007362:Intensive Care Units; D008297:Male; D000077731:Meropenem; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D058889:Molecular Typing; D011552:Pseudomonas Infections / Q000188:drug therapy / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D013845:Thienamycins / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D013845:Thienamycins; D000077731:Meropenem