title: Comparative evaluation of combined-disk tests using different boronic acid compounds for detection of klebsiella pneumoniae carbapenemase-producing enterobacteriaceae clinical isolates.
abstract: The accurate phenotypic detection of Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacteriaceae is an increasing necessity worldwide. We evaluated the performance of boronic acid combined-disk tests using as substrate imipenem or meropenem and as inhibitor of KPC production 300 μg aminophenylboronic acid (APBA), 600 μg APBA, or 400 μg phenylboronic acid (PBA). Tests were considered positive when an increase in the growth-inhibitory zone around a carbapenem disk with KPC inhibitor was 5 mm or greater of the growth-inhibitory zone diameter around the disk containing carbapenem alone. The comparison of the combined-disk tests was performed with 112 genotypically confirmed KPC-possessing Enterobacteriaceae isolates. To measure the specificity of the tests, 127 genotypically confirmed KPC-negative Enterobacteriaceae isolates that were nonsusceptible to at least one carbapenem were chosen for testing. Using disks containing imipenem without and with 300 μg APBA, 600 μg APBA, or 400 μg PBA, 72, 92, and 112 of the KPC producers, respectively, gave positive results (sensitivities, 64.3%, 82.1%, and 100%, respectively). Using disks containing meropenem without and with 300 μg APBA, 600 μg APBA, or 400 μg PBA, 87, 108, and 112 of the KPC producers, respectively, gave positive results (sensitivities, 77.7%, 96.4%, and 100%, respectively). Among KPC producers, the disk potentiation tests using meropenem and PBA demonstrated the largest differences in inhibition zones (P < 0.001). All combined-disk tests correctly identified 124 of the 127 non-KPC producers (specificity, 97.6%). This comparative study showed that PBA is the most effective inhibitor of KPC enzymes, and its use in combined-disk tests with meropenem may give the most easily interpreted results.
authors.affiliation: Department of Microbiology, Medical School, University of Athens, 11527 Athens, Greece. atsakris@med.uoa.gr
authors.forename: Athanassios
authors.initials: A
authors.lastname: Tsakris
authors.forename: Katerina
authors.initials: K
authors.lastname: Themeli-Digalaki
authors.forename: Aggeliki
authors.initials: A
authors.lastname: Poulou
authors.forename: Georgia
authors.initials: G
authors.lastname: Vrioni
authors.forename: Evangelia
authors.initials: E
authors.lastname: Voulgari
authors.forename: Vasiliki
authors.initials: V
authors.lastname: Koumaki
authors.forename: Antonella
authors.initials: A
authors.lastname: Agodi
authors.forename: Spyros
authors.initials: S
authors.lastname: Pournaras
authors.forename: Danai
authors.initials: D
authors.lastname: Sofianou
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000378:metabolism*; D001897:Boronic Acids / Q000378:metabolism*; D004755:Enterobacteriaceae / Q000201:enzymology*; D004756:Enterobacteriaceae Infections / Q000382:microbiology; D005838:Genotype; D006801:Humans; D015378:Imipenem / Q000494:pharmacology; D000077731:Meropenem; D008826:Microbial Sensitivity Tests / Q000379:methods; D010641:Phenotype; D012680:Sensitivity and Specificity; D013845:Thienamycins / Q000494:pharmacology; D001618:beta-Lactamases / Q000378:metabolism*; D047090:beta-Lactams / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D001897:Boronic Acids; D013845:Thienamycins; D047090:beta-Lactams; D015378:Imipenem; D001618:beta-Lactamases; C063912:carbapenemase; D000077731:Meropenem