Clinical use
Screening stool and rectal swabs for the presence of carbapenemase producing enterobacterales.
Background
The term ‘carbapenemase’ relates to any β-lactamase that hydrolyses (breaks down) carbapenems. Carbapenems (including ertapenem, imipenem and meropenem) are antimicrobials of last resort and are crucial for preventing and treating life-threatening nosocomial infections. Carbapenemases pose a significant clinical risk, with their ability to destroy, and so may confer resistance to, carbapenems and most other β-lactams. Carbapenemases are found naturally in a few clinically relevant bacteria, such as Stenotrophomonas maltophilia, Aeromonas species, and ‘chryseobacteria’, including Elizabethkingia meningoseptica.
Detection of CPE from faeces or rectal swabs is performed via culture, requiring a minimum of 18 hours for incubation. Rectal specimens (with visible faecal material or discolouration) are the most sensitive for detecting CPE colonisation, alternatively a faecal specimen. Isolation of CPE by culture allows susceptibility testing and epidemiological typing where required. The laboratory at James Cook utilises commercially available specialist media designed for the isolation of CPE. When suspected CPEs are grown, molecular testing for detection of carbapenemase genes and susceptibility testing is performed. There are hundreds of genes associated with carbapenemase activity, the laboratory at James Cook aims to maintain the ability to detect the most identified genes using commercially available Polymerase Chain Reaction (PCR) platforms. However, there will be occasions where a carbapenemase is suspected but local testing is unable to identify the gene associated. In these instances, the Reference Laboratory Antimicrobial Resistance and Healthcare Associated Infections (AMRHAI), part of UKHSA’s Bacteria Reference Department (BRD) will complete a wider panel of molecular tests to identify the mechanism responsible.
Patient preparation
Infection Prevention and Control (IPC) policy HIC37 (Multi-resistant gram-negative bacteria), that can be found internally on the trust intranet, outlines the patients who fall into the groups which must be screened for CPE. If there is any doubt, discuss this with the IPC team or Microbiology.
Specimen requirements
All patients for screening:
- Rectal swab (visibly soiled with faecal matter) taken using a pink topped eSwab, OR
- Faeces (this may be more easily acquired) in a sterile universal.
- Ideally specimens should be collected before starting antimicrobial therapy.
A single rectal swab is sufficient to determine CPE colonisation status, unless the patient has previously been identified to be colonised with CPE. In addition to the above, patients with any wounds or the sites of invasive devices (such as central lines) can also be screened. Samples should be taken using a pink topped eSwab.
Minimum volume
Rectal swabs MUST have visible faecal matter or discolouration.
Limitations & restrictions
Rectal swabs that are not visibly soiled with faecal material may produce sub-optimal results.
Turnaround time
72 hours
Analysing laboratory
Microbiology Lab, James Cook University Hospital, Marton Road, TS4 3BW
Additional information
Further information on when patients need screening, the number of swabs to send, and where to send these from can be found in HIC37. If there is concern of an outbreak or patient’s have been exposed, please contact IPC.