CRPA Isolate Submission and Laboratory Testing - Minnesota Dept. of Health

CRPA Isolate Submission and Laboratory Testing

The term CRPA refers to carbapenem-resistant Pseudomonas aeruginosa. Some CRPA produce enzymes called carbapenemases that break apart carbapenems; these are referred to as carbapenemase-producing CRPA (CP-CRPA). Currently, the most common type of carbapenemase found in P. aeruginosa globally is the Verona integron-encoded metallo-β-lactamase, or VIM. The genes encoding carbapenemases are often located on plasmids that are easily spread between organisms.

It is important for laboratories to utilize the current Clinical and Laboratory Standards Institute (CLSI) breakpoints for Pseudomonas aeruginosa and carbapenems in order to appropriately identify CRPA.

On this page:
Criteria for submission of isolates
Appropriate specimen types
Specimen submission forms
Shipping to MDH-PHL
Laboratory testing for CP-CRPA
Outbreak and surveillance testing

Criteria for submission of isolates

  • P. aeruginosa isolates resistant to a carbapenem according to the following CLSI breakpoints (current CLSI standard) should be reported and an isolate submitted to the MDH-PHL:
Antibiotic MIC (µg/mL)
Imipenem ≥ 8
Meropenem ≥ 8
Doripenem ≥ 8

  • Isolates found to carry a carbapenemase enzyme (such as VIM) as demonstrated by testing methods such as polymerase chain reaction (PCR), CarbaNP, etc.

Appropriate specimen types

  • A pure, low passage CRPA isolate is preferred as some carbapenem resistance mechanisms are plasmid-based and can be lost following multiple subcultures.
  • Submit isolate on a non-inhibitory, non-selective agar plate or slant (e.g. Sheep blood agar, Tryptic soy agar, etc.)

Specimen submission forms

MDH-PHL requests the following documentation to be included with each CRE isolate submission:

Shipping to MDH-PHL

  • Ship specimens to MDH-PHL by an overnight delivery service or local courier.
    Note: It is the responsibility of the submitting laboratory to determine the appropriate packaging and shipping for patient specimens and culture isolates. See U.S. Department of Transportation Regulations: Hazardous materials shipping for more information. Attention: Non-MDH link
  • Isolates can be shipped at either room temperature or with refrigeration.
  • Ship to:
    Minnesota Department of Health
    Public Health Laboratory
    Attn: Biological Accessioning
    601 Robert St. N
    St. Paul, Minnesota 55155-2531

Laboratory Testing for Carbapenemase-Producing CRPA

MDH CRPA outbreak and surveillance testing

  • MDH-PHL has the capacity to provide outbreak investigation testing for CP-CRPA to Minnesota health care facilities, if necessary
  • MDH-PHL can also provide guidance on outbreak detection protocols to be used in your facility. Call MDH Public Health Laboratory for consultation at 651-201-5073.


MDH-PHL Special Microbiology Laboratory is available during regular business hours for consultation on CRPA testing and result interpretation at 651-201-5073.

Updated Tuesday, 24-Jul-2018 10:28:30 CDT