Combined use of the modified Hodge test and carbapenemase inhibition test for detection of carbapenemase-producing Enterobacteriaceae and metallo-β-lactamase-producing Pseudomonas spp.
BACKGROUND
We evaluated the combined use of the modified Hodge test (MHT) and carbapenemase inhibition test (CIT) using phenylboronic acid (PBA) and EDTA to detect carbapenemase-producing Enterobacteriaceae (CPE) and metallo-β-lactamase (MBL)-producing Pseudomonas spp.


METHODS
A total of 49 isolates of CPE (15 Klebsiella pneumoniae carbapenemase [KPC], 5 Guiana extended-spectrum β-lactamase [GES]-5, 9 New Delhi metallo-β-lactamase [NDM]-1, 5 Verona integron-encoded metallo-β-lactamase [VIM]-2, 3 imipenem-hydrolyzing β-lactamase [IMP], and 12 oxacillinase [OXA]-48-like), 25 isolates of MBL-producing Pseudomonas spp. (14 VIM-2 and 11 IMP), and 35 carbapenemase-negative controls were included. The MHT was performed for all isolates as recommended by the Clinical and Laboratory Standards Institute. Enhanced growth of the indicator strain was measured in mm with a ruler. The CIT was performed by directly dripping PBA and EDTA solutions onto carbapenem disks that were placed on Mueller-Hinton agar plates seeded with the test strain.


RESULTS
Considering the results of the MHT with the ertapenem disk in Enterobacteriaceae and Pseudomonas spp., the CIT with the meropenem disk in Enterobacteriaceae, and the imipenem disk in Pseudomonas spp., three combined disk tests, namely MHT-positive plus PBA-positive, EDTA-positive, and MHT-positive plus PBA-negative plus EDTA-negative, had excellent sensitivity and specificity for the detection of KPC- (100% sensitivity and 100% specificity), MBL- (94% sensitivity and 100% specificity), and OXA-48-like-producing isolates (100% sensitivity and 100% specificity), respectively.


CONCLUSIONS
Combined use of the MHT and CIT with PBA and EDTA, for the detection of CPE and MBL-producing Pseudomonas spp., is effective in detecting and characterizing carbapenemases in routine laboratories.
Department of Laboratory Medicine, Hallym University College of Medicine, Seoul, Korea.
Wonkeun
W
Song
Department of Laboratory Medicine, CHA Bundang Medical Center, CHA University, Seongnam, Korea.
Seong Geun
SG
Hong
Department of Laboratory Medicine, Research Institute of Bacterial Resistance, Yonsei University College of Medicine, Seoul, Korea.
Dongeun
D
Yong
Department of Laboratory Medicine, Research Institute of Bacterial Resistance, Yonsei University College of Medicine, Seoul, Korea.
Seok Hoon
SH
Jeong
Department of Laboratory Medicine, Hallym University College of Medicine, Seoul, Korea.
Hyun Soo
HS
Kim
Department of Laboratory Medicine, Hallym University College of Medicine, Seoul, Korea.
Han-Sung
HS
Kim
Department of Laboratory Medicine, Hallym University College of Medicine, Seoul, Korea.
Jae-Seok
JS
Kim
Department of Dental Hygiene, Silla University, Busan, Korea.
Il Kwon
IK
Bae
D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D001897:Boronic Acids / Q000737:chemistry / Q000494:pharmacology; D052978:Disk Diffusion Antimicrobial Tests / Q000379:methods*; D004492:Edetic Acid / Q000737:chemistry / Q000494:pharmacology; D004755:Enterobacteriaceae / Q000187:drug effects / Q000201:enzymology*; D004756:Enterobacteriaceae Infections / Q000175:diagnosis; D006801:Humans; D011549:Pseudomonas / Q000187:drug effects / Q000201:enzymology*; D011552:Pseudomonas Infections / Q000175:diagnosis; D012680:Sensitivity and Specificity; D001618:beta-Lactamases / Q000737:chemistry / Q000378:metabolism*
D001426:Bacterial Proteins; D001897:Boronic Acids; D004492:Edetic Acid; D001618:beta-Lactamases; C063912:carbapenemase; C010686:benzeneboronic acid
Carbapenemase inhibition test; EDTA; Enterobacteriaceae; Modified Hodge test; Phenylboronic acid; Pseudomonas spp.