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Bacterial Infections
relatively inexpensive compared with rapid molecular methods and is To date none of these studies presents a full cost-effectiveness
suitable for testing both large and small numbers of samples. comparative assessment of the tests within the specific context of the
various defined components of universal screening, and this is much
Rapid Molecular Methods needed. The conclusion of the NHS QIS report was that with the data
PCR tests target MRSA-specific DNA sequences. Whereas in the past that were available in 2007, chromogenic medium was the preferred
this method required a sample enrichment step, PCR systems for universal screening method.
8
As further information becomes
detecting MRSA are now available for the direct screening of samples. available, this assessment must be kept under regular scrutiny.
The advantage of such methods over culture methods is speed, with
results reported to be available in two to three hours or less.
16,17
This Some Clinical Consequences of Universal
can be of great advantage when a rapid result is required. However, Methicillin-resistant Staphylococcus aureus
the cost per test for PCR is much higher than for culture methods and Screening Programmes
there are still question marks in terms of its sensitivity
18
and The success rates for decolonisation administered without clinical
supervision solely by patients in the community remains to be
determined. This is not an inconsequential matter given the quite
complex regimen involved of daily use of the relatively unpleasant
Several method comparison trials are
combination of antibacterial shampoo and bodywash with application of
now becoming available to help antibacterial nasal ointment. There must also be a real concern that the
differentiate the strengths and
wider usage of these materials may lead to resistance progression, and
mupirocin is a principle worry in this regard. In moving to implement
weaknesses of the different approaches
universal MRSA screening for inpatients only, the desired broader
to methicillin-resistant Staphylococcus
population impact of reduced MRSA rates becomes increasingly
challenged as care moves further to day and 23-hour approaches.
aureus screening.
Conclusions
As discussed, the needs of pre-admission screening differ from those of
specificity.
16
Several method comparison trials are now becoming emergency screening and the methods available have different strengths
available to help differentiate the strengths and weaknesses of the and weaknesses. There is no doubt that the approach of universal MRSA
different approaches to MRSA screening. For example, in a comparison screening for inpatient care offers an important opportunity for
of the IDI-MRSA PCR assay (BD GeneOhm) and the GenoType MRSA improving the control of this tenacious, difficult to manage and high-
Direct PCR assay (Hain Lifescience) versus three commercially available profile condition. However, we must be aware that there are insufficient
chromogenic media, the performance of the GenoType MRSA Direct data at present to promote the widespread adoption of such screening in
PCR assay was on a par with that of the culture media (with all scenarios and, while moving ahead to implement schemes,
sensitivities of 68–75%), whereas the IDI-MRSA PCR assay achieved a organisations should audit the cost- and clinical effectiveness of the
sensitivity of 94%.
17
However, this contrasts with the finding of schemes while looking to adopt fresh approaches to maximise benefit.
Rossney et al., who compared the IDI-MRSA PCR assay with traditional
culture methods (overnight in salt broth followed by incubation on At the heart of introducing universal MRSA screening is an acceptance
blood agar) and found that the PCR assay achieved only 82% that if it is successful it will need to bring with it its own demise – at what
sensitivity against culture methods from all specimen types. This work stage does universal inpatient MRSA screening become inappropriate?
also highlighted a potential concern with the ability of the PCR assay We should be thinking about this now and recognising the broader
to detect isolates carrying SCCmec type 5, one of the SCCmec sociological, reputational and public/patient influences that will come to
elements associated with community-acquired MRSA.
18
bear on the question. ■
1. EARSS Annual Report, 2006. Available at:
www.rivm.nl/earss/ 8. NHS Quality Improvement Scotland, The clinical and cost aureus colonisation in an active surveillance program, J Clin
Images/EARSS%202006%20Def_tcm61-44176.pdf effectiveness of screening for meticillin-resistant Staphylococcus Microbiol, 2008;46(9):3101–3.
2. Department of Health, Clean, Safe, Care: Reducing Infection aureus (MRSA), Health Technology Assessment Report 9, 2007. 14. Batra R, Eziefula AC, Wyncoll D, Edgeworth J, Throat and rectal
and Saving Lives, 2008. Available at:
www.nhshealthquality.org swabs may have an important role in MRSA screening of
3. Centre for Infections Mandatory Surveillance Team, Health 9. Health Protection Scotland (HPS) MRSA Screening Programme, critically ill patients, Intensive Care Med, 2008;34:1703–6.
Protection Agency, Summary points and commentary for MRSA 2008. Available at:
www.hps.scot.nhs.uk/haiic/sshaip/mrsa 15. Gurran C, Holliday MG, Perry JD, et al., A Novel Selective
bacteraemia data derived from mandatory surveillance, screeningprogramme.aspx Medium for the Detection of Methicillin-Resistant
September 2008.
www.hpa.org.uk/web/HPAwebFile/HP 10. Ritchie KA, Kohli H, Reilly J, Donaghy M, A trial of universal Staphylococcus aureus Enabling Results Reporting in Under
Aweb_C/1221638192568 screening for MRSA in Scotland. Rapid response to Wilcox, MH, 24hrs, J Hosp Inf, 2002;52:148–51.
4. Department of Health, Saving Lives: Reducing Infection, Screening for MRSA, BMJ, 2008;336:899–900. 16. Rajan L, Smyth E, Humphreys H, Screening for MRSA in ICU
Delivering Clean and Safe Care. Screening for MRSA 11. Coello R, Jimenez J, Garcia M, et al., Prospective study of patients. How does PCR compare with culture?, J Infect, 2007;
colonisation. A strategy for NHS Trusts: a Summary of Best infection colonisation and carriage of methicillin-resistant 55(4):353–7.
Practice, 2007. Staphylococcus aureus in an outbreak affecting 990 patients, 17. van Hal SJ, Stark D, Lockwood B, et al., Methicillin-resistant
5. Wigglesworth N, Wilcox MH, Prospective evaluation of hospital Eur J Clin Microbiol Infect Dis, 1994;13(1):74–81. Staphylococcus aureus (MRSA) detection: comparison of two
isolation room capacity, J Hosp Infect, 2006;63:156–61. 12. Naderer OJ, Anderson M, Roberts K, et al., Case detection of molecular methods (IDI-MRSA PCR assay and GenoType MRSA
6. Kluytmans J, Success in MRSA control, European Hospital, 26 Staphylococcus aureus colonization: screening of the anterior Direct PCR assay) with three selective MRSA agars (MRSA ID,
June 2007. nares (AN) and throat (T), Abstract K-3353, 48th Annual MRSASelect, and CHROMagar MRSA) for use with infection-
7. French G, MRSA – ‘Learning from the Best’ conference, speech Interscience Conference on Antimicrobial Agents and control swabs, J Clin Microbiol, 2007;45(8):2486–90.
summary. Available at:
www.dh.gov.uk/en/Publichealth/Health Chemotherapy (ICAAC) and the Infection Diseases Society of 18. Rossney AS, Herra CM, Fitzgibbon MM, et al., Evaluation of the
protection/Healthcareacquiredinfection/Healthcareacquiredgener America (IDSA) 46th Annual Meeting, 2008. IDI-MRSA assay on the SmartCycler real-time PCR platform for
alinformation/Thedeliveryprogrammetoreducehealthcareassociat 13. Currie A, Davis L, Odrobina E, Sensitivities of Nasal and Rectal rapid detection of MRSA from screening specimens, Eur J Clin
edinfectionsHCAIincludingMRSA/DH_4102049 Swabs for detection of Methicillin reisistant Staphylococcus Microbiol Infect Dis, 2007;26(7):459–66.
84 EUROPEAN INFECTIOUS DISEASE
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