Guidelines for submission of Staphylococcus aureus isolates (including MRSA)

To ensure the most appropriate use of the Staphylococcus Reference Services, please:

• Request typing only if you intend to act upon the results
• Ensure that the Consultant Microbiologist and/or Infection Control Team have confirmed there are good reasons for submission
• State hypothesis to be tested, ie how typing will make a difference

In outbreaks

(a temporal and spatial cluster above the normal baseline)

• Send the minimum number of isolates needed to inform local practice (this should rarely be more than half). Store temporally related isolates.
• Give priority to isolates that cause invasive or serious infection during the course of an outbreak. Avoid sending multiple isolates from single patients or environmental isolates, without prior discussion
• Where possible, use surrogate markers such as urease and antimicrobial resistance profiles to assist with presumptive identification of UK epidemic MRSA (EMRSA 15 is urease-negative; EMRSA-16 is urease-positive).
• Refer representative isolates with significantly different phenotypes eg in antibiotic susceptibilities, pigmentation and /or haemolysis.

In endemic situations

If surrogate markers are being used for strain monitoring or to identify any locally endemic strains, particularly EMRSA-15 and EMRSA-16, we are willing to analyse a few representative isolates for you from time to time, eg up to 10 isolates every 6 months.

Suspected toxin-mediated disease

We would like to receive an isolate from cases of suspected toxin-mediated disease e.g. staphylococcal toxic shock syndrome, impetigo and scalded skin syndrome for toxin gene profiling. In addition, we would like to receive isolates from suspected PVL-related disease e.g. serious skin and soft tissue infection and necrotising pneumonia for analysis.

Further information is available from the HPR archives [external link].

A brief questionnaire will be included with the report, which we would appreciate you completing and returning to us.

Community-Associated MRSA

There are many different lineages of community-associated MRSA, all of which are distinct from healthcare-associated MRSA. Typically, C-MRSA are heterogeneously resistant to oxacillin and unusually susceptible to antimicrobials other than ?-lactams, particularly ciprofloxacin. We would like to receive such isolates for further characterisation.

Further information is available from the CDR archives [external link]

Anomalous findings

State the anomaly to be investigated eg slide coagulase of DNase negative S. aureus. Please check for purity, Gram stain and catalase activity before sending.

Antibiotic resistance

Request antibiotic susceptibility tests only when necessary to assist in clinical management or local studies eg anomalous or doubtful test results, unusual or clinically significant results, necessary quantitation (eg MIC of first encountered mupirocin-resistant isolates), unexpected resistance (eg to vancomycin). Queries about antibiotic susceptibility tests should be made to 020 8327 7237 (MICs) or 020 8327 7255 (mecA/mupA).

Food-related isolates

All isolates relating to incidents of food poisoning of food contamination should be sent directly to the Food Safety Monitoring Laboratory. Further information can be obtained by telephoning 020 8327 7539/6521.

Non-food-related isolates

Please send all non-food-related isolates to the Staphylococcus Reference Laboratory. Further information can be obtained by telephoning 020 8327 7227/8.
For further details of the services available in the Staphylococcus Reference Laboratory, please visit the Staphylococcus Reference Unit.

If you have any queries, please contact us on 020 8327 7227/8.

Last reviewed: 8 October 2010