Modified Hodge Test (MHT) for
Carbapenemase detection
Modified Hodge Test (MHT) is a simple phenotypic test for detection of presence of
carbapenemase enzyme in bacteria.
Positive MHT test is observed in
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Klebsiella pneumoniae carbapenemase (KPC),
Metallo Beta lactamase (MBL)
and the SME-1 in Serratia marcescens.
Modified Hodge Test (MHT) has been suggested as screening tests for carbapenemases.
It is based on the inactivation of a carbapenem by carbapenemase -producing strains (test
isolate) that enable a carbapenem -susceptible indicator strain (E. coli ATCC® 25922) to
extend growth towards a carbapenem-containing disc along the streak of inoculum of the test
strain. Positive test result gives cloverleaf-like indentation.
The MHT performed on a 100 mm MHA plate.
Escherichia coli ATCC 25922 (indicator organism)
(1) K. pneumoniae ATCC BAA 1705, positive result
(2) K. pneumoniae ATCC BAA 1706, negative result; and
(3) a clinical isolate, positive result