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microbial diseases laboratory branch

Test Name - Modified Carbapenem Inhibition Method

Pre-Approval Required:

​Carbapenem resistant Escherichia coli, Klebsiella oxytoca, Klebsiella pneumonia, Klebsiella aerogenes, Enterobacter species and Pseudomonas aeruginosa that meet the criteria listed in the FAQ and ‘Acceptable Specimen type for testing section’ can be routinely submitted. Please routinely submit Pan non-susceptible Pseudomonas aeruginosa, and Enterobacterales isolates, including other than those listed above for surveillance testing. Testing is available for carbapenem resistant Enterobacterales other than those listed above and but pre-approval is required prior to submission. mCIM testing is not available for carbapenem resistant Acinetobacter spp. (CRAB). Please see FAQ for tests currently available for CRAB. Contact the HAI program at or MDL at for pre-approval.​ ​

Supplemental Information or Form:

Human sources

Acceptable Sample/Specimen Type for Testing:

Pure culture isolate.

​​Isolate must be identified to at least the genus level by the submitter.

Mixed cultures received in MDL will not be tested.

​Isolates must meet one of the following criteria

Please Note: If the species is intrinsically resistant to a carbapenem antibiotic (for example Proteus and Morganella morganii and imipenem) they must also be resistant to another relevant carbapenem. Please refer to the FAQ and contact MDL to request a review of the available AST results prior to submission as needed.

​​​Carbapenem resistant Enterobacterales (CRE)

Enterobacterales must be resistant to at least one relevant carbapenem, i.e., imipenem, ertapenem, doripenem, or meropenem.

Carbapenem-resistant Pseudomonas aeruginosa (CRPA)

Submit carbapenem-resistant P. aeruginosa isolates that are resistant to imipenem, meropenem, or doripenem by standard AST methods (i.e., MIC of ≥ 8 µg/mL) and Nonsusceptible (i.e., intermediate or resistant MIC ≥ 16µg/ml) to cefepime or ceftazidime.

​​​​mCIM is not validated for Acinetobacter spp. and isolates will not be tested. Please see FAQ for testing available for CRAB at MDL. 

Very rarely isolates can carry a carbapenemase gene and not express it. These isolates may test positive for a carbapenemase gene via a genotypic assay but not demonstrate carbapenem resistance in a phenotypic assay such as AST or mCIM. Isolates with a positive genotypic result that do not demonstrate carbapenem resistance can be tested at MDL or sent out to other ARLN labs for further testing. Please contact MDL prior to submission of these or other unusual isolates. ​

Minimum Volume Required:

Not Applicable

Storage & Preservation of Sample/Specimen Prior to Shipping:

Store at ambient temperature.


Ship cultures on nonselective nutrient or similar agar in tubes with leak-proof screw cap closures.

Sample/Specimen Labeling:

Two patient identifiers on the specimen container and on the test requisition are required.

Shipping Instructions, Including Specimen Handling Requirements:

Ship at ambient temperature.

Test Methodology:

Phenotypic testing

Turnaround Time:

14 days

Interferences & Limitations:

The results of the mCIM are for epidemiological purposes, and are not intended to guide or monitor treatment for carbapenem resistant bacterial infections.

Additional Information:


MDL Points of Contact:

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