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Indian J Med Microbiol. 2014 Oct-Dec;32(4):414-8. doi: 10.4103/0255-0857.142258.

A possible alternative to the error prone modified Hodge test to correctly identify the carbapenemase producing Gram-negative bacteria.

Author information

1
Department of Microbiology, Christian Medical College, Vellore, Tamil Nadu, India.

Abstract

CONTEXT:

The modified Hodge test (MHT) is widely used as a screening test for the detection of carbapenemases in Gram-negative bacteria. This test has several pitfalls in terms of validity and interpretation. Also the test has a very low sensitivity in detecting the New Delhi metallo-β-lactamase (NDM). Considering the degree of dissemination of the NDM and the growing pandemic of carbapenem resistance, a more accurate alternative test is needed at the earliest.

AIMS:

The study intends to compare the performance of the MHT with the commercially available Neo-Sensitabs - Carbapenemases/Metallo-β-Lactamase (MBL) Confirmative Identification pack to find out whether the latter could be an efficient alternative to the former.

SETTINGS AND DESIGN:

A total of 105 isolates of Klebsiella pneumoniae resistant to imipenem and meropenem, collected prospectively over a period of 2 years were included in the study.

SUBJECTS AND METHODS:

The study isolates were tested with the MHT, the Neo-Sensitabs - Carbapenemases/MBL Confirmative Identification pack and polymerase chain reaction (PCR) for detecting the blaNDM-1 gene.

RESULTS:

Among the 105 isolates, the MHT identified 100 isolates as carbapenemase producers. In the five isolates negative for the MHT, four were found to produce MBLs by the Neo-Sensitabs. The Neo-Sensitabs did not have any false negatives when compared against the PCR.

CONCLUSIONS:

The MHT can give false negative results, which lead to failure in detecting the carbapenemase producers. Also considering the other pitfalls of the MHT, the Neo-Sensitabs--Carbapenemases/MBL Confirmative Identification pack could be a more efficient alternative for detection of carbapenemase production in Gram-negative bacteria.

PMID:
25297027
DOI:
10.4103/0255-0857.142258
[Indexed for MEDLINE]
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