Improving the efficiency of the modified Hodge test in KPC-producing Klebsiella pneumoniae isolates by incorporating an EDTA disk.

Carbapenemase-producing Klebsiella pneumoniae have emerged as an important pathogens in nosocomial infections with high mortality rate. Although the modified Hodge test (MHT) is recommended for phenotypic detection of carbapenemase-producing Enterobacteriaceae, high false-positive rates were reported for MHT results. The MHT has acceptable sensitivity (98.0 %), but it lacks specificity (73.6 %). In this study, we incorporated an EDTA disk test into the MHT (MHT-EDTA) to improve the efficiency in phenotypic detection of K. pneumoniae carbapenemase (KPC) of K. pneumoniae isolates. EDTA was used to lyse the cells of 123 carbapenem non-susceptible K. pneumoniae isolates to release the β-lactamases. The MHT-EDTA achieved 100 % sensitivity and specificity for KPC detection among K. pneumoniae isolates as compared to growth patterns of the indicator organism E. coli (ATCC 25922). This method could be carried out as part of routine work to provide useful information for the clinical management of K. pneumoniae infection.