The burden of infections with multi-drug resistant organisms (MDRO) continues to increase globally and locally (1,2). A MDRO is defined as an organism that is resistant to three or more classes of antibiotics. Infections with these organisms can be challenging to manage as therapeutic antimicrobial options are limited. Therefore, various preventive measures are undertaken to prevent the evolution and spread of MDRO in healthcare settings. This includes screening prior to hospital admission in order to identify at-risk patients who are colonised with MDRO.

Sampling for MDRO

Screening for MDROs involves the collection of swab specimens from various anatomical sites that are usually colonised with these organisms. See table below.

Organism	Anatomical site
Methicillin-resistant Staphylococcus aureus (MRSA)	Bilateral nasal and groin swabs
Extended-spectrum B-lactamase (ESBL) producing Enterobacterales and Carbapenemase-producing organisms (CPOs)	Anal swab*
Vancomycin-resistant Enterococci (VRE)	Anal swab*
Carbapenem-resistant Acinetobacter baumannii (CRAB)	Bilateral axillary and groin swabs***
Candida auris**	Bilateral axillary and groin swabs***

* One anal swab is adequate for ESBL/ CPO and VRE screening.
** Screening for Candida auris is only recommended if there is a history of overseas hospital admission in the last 12 months.
*** If both CRAB and Candida auris screening are required; two sets of axillary and groin swabs should be collected.

Specimen collection guides

Swab specimens may be clinician- or patient-collected. Instructions for collection may be found on the this website under For Patients / “Prepare for My Tests”:

• Anal Swab Collection for ESBL, CPE, CPO, FREC and/or VRE screening
• Nasal and groin swab collection for MRSA screening
• Axilla and groin collection for Candida auris and/or carbapenem-resistant Acinetobacter (CRAB) screening

It is important that microbiology laboratories receive adequate specimens for MDRO screening, in order to optimise their diagnostic sensitivity. In particular, anal swabs should have evidence of faecal (brown) staining. This is used as a marker of rectal insertion of swab and adequate sampling.

The laboratory will decline to process anal swab specimens without evidence of faecal staining, and a recollect will need to be organised. Therefore, in order to avoid processing delays and inconvenience, it is imperative that patients are educated on appropriate self-sampling and checking for the adequacy (brown staining) of anal swab specimens.

Clinicians are advised to print copies of the collection guides (linked above) and use them as visual aids when instructing patients.

References:

• Lancet 2022; 399: 629–55. Global burden of bacterial antimicrobial resistance in 2019: a systematic analysis
• Antimicrobial resistance of organisms monitored and reported on by ESR. https://www.esr.cri.nz/our-research/nga-kete/infectious-disease-intelligence/antimicrobial-resistanceamr/

Download a PDF copy here.