title: Evaluation of boronic acid disk tests for differentiating KPC-possessing Klebsiella pneumoniae isolates in the clinical laboratory.
abstract: The worldwide increase in the occurrence and dissemination of KPC beta-lactamases among gram-negative pathogens makes critical the early detection of these enzymes. Boronic acid disk tests using different antibiotic substrates were evaluated for detection of KPC-possessing Klebsiella pneumoniae isolates. A total of 57 genotypically confirmed KPC-possessing K. pneumoniae isolates with varying carbapenem MICs were examined. To measure the specificity of the tests, 106 non-KPC-possessing isolates (89 K. pneumoniae and 17 Escherichia coli isolates) were randomly selected among those exhibiting reduced susceptibility to cefoxitin, expanded-spectrum cephalosporins, or carbapenems. As many as 56, 53, and 40 of the non-KPC-possessing isolates harbored extended-spectrum beta-lactamases, metallo-beta-lactamases, and plasmid-mediated AmpC beta-lactamases, respectively. By use of CLSI methodology and disks containing imipenem, meropenem, or cefepime, either alone or in combination with 400 microg of boronic acid, all 57 KPC producers gave positive results (sensitivity, 100%) whereas all 106 non-KPC producers were negative (specificity, 100%). The meropenem duplicate disk with or without boronic acid demonstrated the largest differences in inhibition zone diameters between KPC producers and non-KPC producers. By use of disks containing ertapenem, all isolates were correctly differentiated except for five AmpC producers that gave false-positive results (sensitivity, 100%; specificity, 95.3%). These practical and simple boronic acid disk tests promise to be very helpful for the accurate differentiation of KPC-possessing K. pneumoniae isolates, even in regions where different broad-spectrum beta-lactamases are widespread.
authors.affiliation: Department of Microbiology, Medical School, University of Athens, Athens, Greece. atsakris@med.uoa.gr
authors.forename: Athanassios
authors.initials: A
authors.lastname: Tsakris
authors.forename: Ioulia
authors.initials: I
authors.lastname: Kristo
authors.forename: Aggeliki
authors.initials: A
authors.lastname: Poulou
authors.forename: Katerina
authors.initials: K
authors.lastname: Themeli-Digalaki
authors.forename: Alexandros
authors.initials: A
authors.lastname: Ikonomidis
authors.forename: Dimitra
authors.initials: D
authors.lastname: Petropoulou
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; D001431:Bacteriological Techniques / Q000379:methods*; D001897:Boronic Acids / Q000378:metabolism*; D005189:False Positive Reactions; D006801:Humans; D007711:Klebsiella pneumoniae / Q000737:chemistry* / Q000187:drug effects / Q000201:enzymology* / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests / Q000379:methods; D012680:Sensitivity and Specificity; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000032:analysis*; D047090:beta-Lactams / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D001897:Boronic Acids; D047090:beta-Lactams; D001618:beta-Lactamases