Modified Hodge Test
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Microoganisms for Modified Hodge Test are Now Available from Microbiologics®
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Microbiologics has recently added the Clinical Laboratory Standards Institute (CLSI) recommended quality control microorganisms for the Modified Hodge Test (MHT) to their product range. The MHT is an important tool for detecting Klebsiella pneumoniae carbapenemase (KPC) in Enterobacteriaceae.
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A Guide to Performing the Modified Hodge Test Using Microbiologics® QC Microorganisms
Background to Modified Hodge Test
KPCs are class A carbapenemases that reside on transferable plasmids and are capable of inactivating carbapenems, such as imipenem and meropenem. Since carbapenems are often used to treat infections caused by extended-spectrum beta lactamase (ESBL)-producing Gram-negative bacteria, carbapenemase production in Enterobacteriaceae can significantly limit treatment options for life-threatening diseases. KPCs occur most commonly in Klebsiella pneumoniae but have been seen in other species of Enterobacteraciae as well.

CLSI (Clinical Laboratory Standards Institute) recommends the MHT be performed before reporting carbapenem susceptibility results if a clinical isolate has an elevated but susceptible carbapenem MIC. Susceptibility results may be reported without performing the MHT if a clinical isolate is intermediate or resistant to carbapenems, but clinical laboratories may want to perform the MHT for infection control and epidemiological reasons.
Methodology
To perform the MHT, a suspension of the carbapenem susceptible strain of E. coli ATCC® 25922™* (Microbiologics 0335) is prepared, diluted, and swabbed in lawn-like fashion across a Mueller Hinton plate. A 10 µg meropenem or ertapenem susceptibility disk is placed in the center of the test plate. The test microorganism is streaked in a straight line from the edge of the disk to the edge of the plate. The plate is incubated overnight. A positive test will show growth of the E. coli ATCC® 25922™* on the microorganism streak line towards the carbapenem disk. A negative test will show no growth of the E. coli on the microorganism streak line.

A positive test indicates carbapenemase production by the test microorganism. By producing carbapenemase, the test microorganism is able to inactivate the carbapenem that diffuses from the disk after the disk has been placed on the Mueller Hinton Agar. This allows carbapenem susceptible E. coli ATCC® 25922™* to grow toward the disk. A negative test indicates no carbapenemase production by the test microorganism.

The quality control microorganisms used in the MHT are as follows:

MHT positive Klebsiella pneumoniae, ATCC® BAA-1705™* (Microbiologics 01005)
MHT negative Klebsiella pneumoniae, ATCC® BAA-1706™* (Microbiologics 01006)

The recommended Microbiologics products for Modifed Hodge Test are listed in the table below.

Detailed instructions for the MHT can be found in the CLSI book, "Performance Standards for Antimicrobial Susceptibility Testing: Nineteenth Informational Supplement". The procedure is also described by CDC in a pamphlet available for download below called, "Modified Hodge Test for Carbapenemase Detection in Enterobacteriaceae".
References
CLSI. 2009. Performance Standards for Antimicrobial Susceptibility Testing: Nineteenth Informational Supplement. CLSI document M100-S19, pages 136-139. Wayne, PA; Clinical Laboratory Standards Institute.
CDC. 2009. Modified Hodge Test for Carbapenemase Detection in Enterobacteriaceae. CDC Protocol. Centers for Disease Control and Prevention Antimicrobial Resistance Team. CDC, Atlanta GA.
CDC. Slide Presentation. 2009. Jean B. Patel. Carbapenem-Resistant Enterobacteriaceae (CRE) Detection and Control.
CDC. Slide Presentation. 2009. Jean B. Patel. VISA, hVISA, β-lactamases in Enterobacteriaceae
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Literature Description Size File1
A Guide to Performing the Modified Hodge Test Using Microbiologics® QC Microorganisms (The above MicorBioLogics® article as a pdf file) 144KB Download MicroBioLogics MHT Article
Modified Hodge Test for Carbapenemase Detection in Enterobacteriaceae (CDC Article) 125KB Download CDC MHT Article
Note 1: Click on the Adobe Acrobat  icon to download the file
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Item Code Product Description Pack Size List Price
Carbapenem Susceptible E. coli ATCC® 25922™*
MB-0335P KWIK-STIK Escherichia coli ATCC® 25922™ 2/pk $79.00
MB-0335K KWIK-STIK Escherichia coli ATCC® 25922™ 6/pk $165.00
MB-0335L LYFO DISK Escherichia coli ATCC® 25922™* 6/vial $140.00
MHT positive Klebsiella pneumoniae, ATCC® BAA-1705™*
MB-01005P KWIK-STIK Klebsiella pneumoniae ATCC® BAA-1705™* 2/pk $88.00
MB-01005K KWIK-STIK Klebsiella pneumoniae ATCC® BAA-1705™* 6/pk $195.00
MB-01005L LYFO DISK Klebsiella pneumoniae ATCC® BAA-1705™* 6/vial $170.00
MHT negative Klebsiella pneumoniae, ATCC® BAA-1706™*
MB-01006P KWIK-STIK Klebsiella pneumoniae ATCC® BAA-1706™* 2/pk $88.00
MB-01006K KWIK-STIK Klebsiella pneumoniae ATCC® BAA-1706™* 10/pk $195.00
MB-01006L LYFO DISK Klebsiella pneumoniae ATCC® BAA-1706™* 6/vial $170.00
Note 1: Click on the Item Code to go to Online Prices and Ordering
Note 2: Prices are exclusive of GST and local packing, handling and delivery charges
Look for the ATCC Licensed Derivative® Emblem for products derived from ATCC® cultures
Microbiologics® is registered trademark of Microbiologics, Inc. St Cloud, MN, USA
LYFO DISK® is a registered trademark of Microbiologics, Inc. St Cloud, MN, USA. KWIK-STIK™ is a trademark of Microbiologics, Inc in the United States and other countries
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