The National Meticillin-Resistant Staphylococcus aureus (MRSA) Reference Laboratory (NMRSARL) supports efforts to prevent and control the spread of MRSA in Ireland by:
The National Meticillin-Resistant Staphylococcus aureus (MRSA) Reference Laboratory (NMRSARL) provides a national service to microbiology staff in Irish hospitals on MRSA isolates for:
Advice is provided on:
NMRSARL investigates MRSA isolates from microbiology laboratories in Irish hospitals.
NMRSARL does not investigate patient specimens for MRSA. Send fresh subcultures on nutrient agar slopes from 18-h subcultures grown in pure culture on blood agar as soon as possible after isolation (or fresh subcultures from isolates stored at or below -20°C). Isolates must be accompanied by NMRSARL laboratory investigation forms NMRSARL Request Form. Isolates submitted to the NMRSARL as part of the EARS-Net project must accompany an EARS-Net form NMRSARL User Manual 2024.
Confirmation of meticillin resistance
Isolates giving equivocal results with the standard tests for species identification of S. aureus are tested by PCR to detect the species specific nuc gene. Isolates with borderline resistance to meticillin are tested by oxacillin gradient minimum inhibitory concentration by PCR to detect the mecA and mecC genes.
spa typing involves sequencing of the staphylococcal protein A gene (spa) to recognise mutations or repeat insertion/deletion events that can cause changes in the polymorphic X region of the spa gene. It has become a well-established discriminatory method for outbreak investigations but has also been shown to be useful for long-term epidemiological studies. The availability of MLST data associated with spa types on an online database facilitates comparison of Irish isolates with isolates from all other countries.
Antimicrobial resistance monitoring
Antimicrobial resistance is an increasingly serious threat to global public health with increasing resistance threatening the effective prevention and treatment of infections caused by bacteria, parasites, viruses and fungi. Resistance among isolates recovered in Irish healthcare facilities and the community is monitored using a panel of frequently used agents using disk diffusion methods. In addition, resistance to newer antibiotics including linezolid, daptomycin and ceftaroline is monitored using broth microdilution.
GISA (glycopeptide intermediate resistant staphylococcus aureus) screen
All referred isolates are screened for glycopeptide resistance using teicoplanin and vancomycin agar screening plates. Isolates positive on screening are tested by gradient minimum inhibitory concentration determination against vancomycin and teicoplanin using a CLSI Macromethod and if required a modified population analysis profile is performed.
Part of NMRSARL’s current work is the routine monitoring of MRSA strains prevalent in Ireland. This is done in conjunction with the HPSC by epidemiological typing of MRSA isolates received from Irish hospitals that participate in the European Antimicrobial Resistance Surveillance Network (EARSNet). This information is used to monitor the changes in the MRSA population in Ireland.
Detection of Virulence Factors
PCR tests for the detection of the panton-valentine leucocidin (PVL) toxin, and exfoliative toxins, virulence factors associated with MRSA and MSSA strains causing skin and soft tissue infection in the community is investigated in NMRSARL.
Staphylococci other than MRSA
Many of the tests performed in the Reference Laboratory are useful in the investigation of other staphylococci. Epidemiological typing of MSSA by spa typing and species identification of CNS by phenotypic methods will be undertaken on request.
The Quality Management System of the NMRSARL ensures that prompt, quality assured and clinically appropriate service is provided to users throughout Ireland. This is done through a process of quality planning which is the part of quality management focused on setting quality objectives and specifying necessary operational processes and related resources to fulfil quality objectives. Should you require details of the accreditation status of the NMRSARL please contact the laboratory directly.
The NMRSARL has a continuing commitment to research and development activities relevant to the work of the laboratory and collaborates with a number of external agencies to ensure the best possible service is provided to our users in line with international developments in the area of MRSA.
Areas of interest include: