Carbapenem-Resistant Organisms (CRO)

VDH Quick Guide for Nursing Home Infection Preventionists: CROs/CPOs (09/07/2023

Infection Prevention for Acute Care and Long-Term Acute Care Hospitals (04/28/2023)

Infection Prevention for Long-Term Care Facilities (04/28/2023)

CDC Guide to Infection Prevention for Outpatient Settings

• Some CROs are caused by a specific resistance mechanism called carbapenemases, which are enzymes that directly break apart the carbapenem antibiotic making it ineffective.
• Because carbapenemase genes are often located on mobile genetic elements (e.g., plasmids), transfer of resistance among/across Enterobacteriaceae or other gram-negative organisms is enhanced, resulting in the potential for widespread transmission.
• Those organisms are called  carbapenemase-producing or "CP."
• To slow the spread of CPOs, VDH recommends following the CDC Containment Strategy.

Infections caused by CPOs have been identified in all Virginia regions. Carbapenemase genes that have been identified in the United States are presented in Table 1. Determining the carbapenemase gene responsible for carbapenem resistance is critical to the public health response and for clinical decision-making.

Table 1. Carbapenemase Genes

In Virginia, a systematic public health response and investigation occurs upon identification of every CPO case. The public health response involves:

1. Promptly detecting the presence of carbapenemases in clinical specimens or pan-resistant isolates;
2. Collecting the least amount of information needed to determine appropriate recommendations based on CDC Containment Strategy Guidance;
3. Verifying appropriate infection control measures (e.g., contact precautions, private room) are implemented by the healthcare facility to stop transmission, and performing onsite assessments of infection prevention practices;
4. Identifying affected patients, determining whether transmission to other patients is occurring or has occurred, and recommending appropriate infection control measures to stop further transmission;
5. Facilitating colonization screenings of high-risk healthcare contacts so that additional infection prevention measures can be put into place; and
6. Continuing to work with the facility or setting on enhanced surveillance and implementation of infection prevention practices.

• VDH Containment Strategy
• VDH Onsite Infection Prevention and Control Assessment
• VDH CPO Colonization Screening Recommendations

Virginia Reportable Disease List in PDF Format

Report all carbapenemase-producing organisms (CPO), infection or colonization, to your local health department (LHD)

• Submit a laboratory report and/or Epi-1 form; see Table 1.
• Include available antimicrobial susceptibility testing (AST) results.

Submit carbapenem-resistant Enterobacteriaceae (CRE) and carbapenem-resistant Pseudomonas aeruginosa (CRPA) isolates to the Division of Consolidated Laboratory Services (DCLS) for further public health testing unless the laboratory is capable of conducting a comparable level of testing for carbapenemase-production as DCLS; see Table 1. This additional testing is not available for other CROs at this time.

• Use the DCLS Clinical Microbiology/Virology Request Form.
• Include available AST results with specimen submissions.

Table 1. Recommendations for Isolate Submission to DCLS and Reporting to LHD Based on Hospital/ Reference Laboratory Testing and Electronic Laboratory Reporting (ELR) Capacity

^ Hospitals using an out-of-state reference laboratory must include these findings in the ELR messages if their laboratory information system is able to do so. If not, submit to public health by fax or mail.
⁺ Please contact the HAI/AR Program to inquire if your laboratory can be exempt from sending CRE and CRPA isolates for further testing at DCLS.
* Per agreement with Virginia Department of Health, except when requested for further public health testing.

1. Identify CRE and CRPA isolates that produce a carbapenemase and classify the type of carbapenemase present.
2. Identify early, high-priority results that would require immediate notification to the Centers for Disease Control and Prevention (CDC), and be potentially characterized further at the regional antibiotic resistance laboratory or CDC:
   • Pan-resistance
   • CP-CRE with resistance mechanism other than Klebsiella pneumoniae carbapenemase (KPC)
   • Any CP-CRPA
   • mcr-type resistance
   • Suspected novel resistance mechanism
3. Facilitate submission of isolates with high-priority results to the regional antibiotic resistance laboratory or CDC for additional testing.

Testing algorithm conducted at DCLS for Enterobacteriaceae and P. aeruginosa isolates that meet carbapenem AST results requirements (refer to DCLS CRE/CRPA testing instructions)

1. Confirm species identification by MALDI-TOF (Bruker Biotyper)
2. Antimicrobial susceptibility testing (AST) by broth microdilution for all CRE and mCIM-positive CRPA
3. Phenotypic testing for carbapenemase production by modified carbapenem inactivation method (mCIM)
   4. Molecular detection of resistance mechanisms (KPC, NDM, OXA-48-like, VIM, IMP, mcr-1 and mcr-2) by real-time PCR for all CRE and mCIM-positive CRPA

Refer to DCLS CRE/CRPA testing instructions

1. Submit pure suspect CRE or CRPA isolates on slant or plate media. Ship isolates at room temperature.
2. Submit a completed DCLS Clinical Microbiology/Virology Request Form and AST results for each isolate. Testing will be delayed if AST results are not received.
3. Turnaround time for reporting results will be within 6 business days of specimen receipt.
4. Alert value results will be verbally reported within 1 working day of results. Non-alert-value, positive results will be verbally reported within 2 working days of results.
5. A hard copy report of final test results will be provided to the submitter by mail.