UpToDate
Official reprint from UpToDate®
www.uptodate.com ©2016 UpToDate®

Rapid detection of methicillin-resistant Staphylococcus aureus

Authors
Joshua Freeman, MBChB, FRCPA
Arthur Morris, MD, D(ABMM)
Section Editor
Daniel J Sexton, MD
Deputy Editor
Elinor L Baron, MD, DTMH

INTRODUCTION

Approaches to rapid detection of methicillin-resistant Staphylococcus aureus (MRSA) include rapid culture methods and molecular techniques. A number of studies have examined the role of rapid detection methods as a component of MRSA control strategies. Molecular diagnostic methods can reduce the "turnaround time" for detection of MRSA colonization, leading to earlier isolation of colonized patients and lower rates of MRSA transmission. Other studies have evaluated the role of molecular and rapid culture methods as ways to rapidly detect MRSA from positive blood cultures.

Laboratory tools for rapid detection will be discussed here; the microbiology of MRSA and clinical issues related to MRSA surveillance are discussed in detail separately. (See "Methicillin-resistant Staphylococcus aureus (MRSA): Microbiology" and "Methicillin-resistant Staphylococcus aureus (MRSA) in adults: Prevention and control".)

SAMPLING SITE

The anterior nares are the most common site for methicillin-resistant S. aureus carriage; sampling multiple anatomical sites increases sensitivity [1-3]. Lower sensitivities have been observed for nonnasal sample sites, perhaps due to lower colonization rates or higher quantities of competing flora at these sites. Rectal swabs are likely to contain polymerase chain reaction inhibitors and therefore are of limited utility when molecular methods are used [4].

LABORATORY TOOLS

Cefoxitin disk screen test — By definition, all methicillin-resistant S. aureus (MRSA) isolates carry the mecA gene, which confers resistance to all beta-lactam antibiotics, including cephalosporins and carbapenems. Apart from using molecular methods to detect the mecA gene directly, the most accurate phenotypic test for the presence of the mecA gene in S. aureus is the cefoxitin disk diffusion test. Cefoxitin is used because it is a more potent inducer of mecA expression than other agents such as oxacillin and the test results are relatively easy to interpret. The test involves incubating a lawn of the test isolate on Mueller Hinton agar +2% sodium chloride under standardized conditions with a cefoxitin disk (30 mcg). According to the Clinical and Laboratory Standards Institute (CLSI), a zone of growth inhibition around the cefoxitin disk of ≥22 mm rules out MRSA; a zone size <22 mm indicates that the mecA gene is present and the isolate should be reported as MRSA [5].

Rapid culture

Chromogenic agar — Rapid culture makes use of chromogenic agar, which contains media substrates that change color in the presence of S. aureus; selectivity for MRSA is achieved by incorporation of antibiotics into the agar. Use of such agar allows identification of MRSA from primary isolation plates within 24 to 48 hours, obviating the need for additional subcultures or biochemical tests [6].

        

Subscribers log in here

To continue reading this article, you must log in with your personal, hospital, or group practice subscription. For more information or to purchase a personal subscription, click below on the option that best describes you:
Literature review current through: Nov 2016. | This topic last updated: Tue Feb 23 00:00:00 GMT 2016.
The content on the UpToDate website is not intended nor recommended as a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your own physician or other qualified health care professional regarding any medical questions or conditions. The use of this website is governed by the UpToDate Terms of Use ©2016 UpToDate, Inc.
References
Top
  1. Reyes RC, Stoakes L, Milburn S, et al. Evaluation of a new chromogenic medium for the detection of methicillin-resistant Staphylococcus aureus carriage on nasal and perianal specimens. Diagn Microbiol Infect Dis 2008; 60:225.
  2. Bishop EJ, Grabsch EA, Ballard SA, et al. Concurrent analysis of nose and groin swab specimens by the IDI-MRSA PCR assay is comparable to analysis by individual-specimen PCR and routine culture assays for detection of colonization by methicillin-resistant Staphylococcus aureus. J Clin Microbiol 2006; 44:2904.
  3. Rohrer S, Tschierske M, Zbinden R, Berger-Bächi B. Improved methods for detection of methicillin-resistant Staphylococcus aureus. Eur J Clin Microbiol Infect Dis 2001; 20:267.
  4. Desjardins M, Guibord C, Lalonde B, et al. Evaluation of the IDI-MRSA assay for detection of methicillin-resistant staphylococcus aureus from nasal and rectal specimens pooled in a selective broth. J Clin Microbiol 2006; 44:1219.
  5. Performance Standards for Antimicrobial Susceptibility Testing; Twenty-Second Informational Supplement. Clinical and Laboratory Standards Institute, Wayne, PA 2012.
  6. Malhotra-Kumar S, Haccuria K, Michiels M, et al. Current trends in rapid diagnostics for methicillin-resistant Staphylococcus aureus and glycopeptide-resistant enterococcus species. J Clin Microbiol 2008; 46:1577.
  7. Pape J, Wadlin J, Nachamkin I. Use of BBL CHROMagar MRSA medium for identification of methicillin-resistant Staphylococcus aureus directly from blood cultures. J Clin Microbiol 2006; 44:2575.
  8. Compernolle V, Verschraegen G, Claeys G. Combined use of Pastorex Staph-Plus and either of two new chromogenic agars, MRSA ID and CHROMagar MRSA, for detection of methicillin-resistant Staphylococcus aureus. J Clin Microbiol 2007; 45:154.
  9. van Hal SJ, Stark D, Lockwood B, et al. Methicillin-resistant Staphylococcus aureus (MRSA) detection: comparison of two molecular methods (IDI-MRSA PCR assay and GenoType MRSA Direct PCR assay) with three selective MRSA agars (MRSA ID, MRSASelect, and CHROMagar MRSA) for use with infection-control swabs. J Clin Microbiol 2007; 45:2486.
  10. Cherkaoui A, Renzi G, François P, Schrenzel J. Comparison of four chromogenic media for culture-based screening of meticillin-resistant Staphylococcus aureus. J Med Microbiol 2007; 56:500.
  11. Perry JD, Davies A, Butterworth LA, et al. Development and evaluation of a chromogenic agar medium for methicillin-resistant Staphylococcus aureus. J Clin Microbiol 2004; 42:4519.
  12. Nahimana I, Francioli P, Blanc DS. Evaluation of three chromogenic media (MRSA-ID, MRSA-Select and CHROMagar MRSA) and ORSAB for surveillance cultures of methicillin-resistant Staphylococcus aureus. Clin Microbiol Infect 2006; 12:1168.
  13. Louie L, Soares D, Meaney H, et al. Evaluation of a new chromogenic medium, MRSA select, for detection of methicillin-resistant Staphylococcus aureus. J Clin Microbiol 2006; 44:4561.
  14. Hansen M, Silvis W, Kaiser P, Lehn N. Comparison of four different MRSA-selective plates for MRSA screening, abstr. 2719. Abstr. 46th Intersci Conf Antimicrob Agents Chemother, September 27-30, 2006.
  15. Stoakes L, Reyes R, Daniel J, et al. Prospective comparison of a new chromogenic medium, MRSASelect, to CHROMagar MRSA and mannitol-salt medium supplemented with oxacillin or cefoxitin for detection of methicillin-resistant Staphylococcus aureus. J Clin Microbiol 2006; 44:637.
  16. Ben Nsira S, Dupuis M, Leclercq R. Evaluation of MRSA Select, a new chromogenic medium for the detection of nasal carriage of methicillin-resistant Staphylococcus aureus. Int J Antimicrob Agents 2006; 27:561.
  17. Ohara S, Malhotra-Kumar S, Haccuria K, et al. Novel rapid culture-based detection method for methicillin-resistant Staphylococcus [corrected] aureus. J Clin Microbiol 2008; 46:3181; author reply 381.
  18. O'Hara S, Gregory S, Taylor D et al. 2007 Evaluation of the 3M BacLite rapid MRSA test for the direct detection of MRSA from nasal and groin surveillance specimens, abstr 540, p. 162-163. Abstr. Annu. Meet. Infect. Dis. Soc. Am. Infectious Diseases Society of America, Arlington, VA.
  19. Bhowmick T, Weinstein MP, Rothberg J, et al. Controlled Evaluation of a Novel Method to Detect Staphylococcus aureus in Blood Cultures within 5 Hours. Presented at: American Society for Microbiology, Boston, September 12, 2010. http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=9fbfe494-6945-4d38-9ccb-1599f6c8cdaa&cKey=0188c349-3ec7-483d-aa67-0ff29c684149&mKey={93AEED6A-54D4-4EF6-99BD-A9B3CE9FACD9} (Accessed on June 08, 2011).
  20. US Food and Drug Administration. FDA clears first test to quickly diagnose and distinguish MRSA and MSSA. http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm254512.htm (Accessed on June 08, 2011).
  21. García-Álvarez L, Holden MT, Lindsay H, et al. Meticillin-resistant Staphylococcus aureus with a novel mecA homologue in human and bovine populations in the UK and Denmark: a descriptive study. Lancet Infect Dis 2011; 11:595.
  22. Shore AC, Deasy EC, Slickers P, et al. Detection of staphylococcal cassette chromosome mec type XI carrying highly divergent mecA, mecI, mecR1, blaZ, and ccr genes in human clinical isolates of clonal complex 130 methicillin-resistant Staphylococcus aureus. Antimicrob Agents Chemother 2011; 55:3765.
  23. Carroll KC. Rapid diagnostics for methicillin-resistant Staphylococcus aureus: current status. Mol Diagn Ther 2008; 12:15.
  24. Eigner U, Holfelder M, Wild U, et al. Evaluation of a rapid molecular dipstick assay for the direct detection of methicillin-resistant Staphylococcus aureus in clinical specimens, abstr. O-21. 17th Eur Congr Clin Microbiol Infect Dis, 30 March to 3 April 2007.
  25. Holfelder M, Eigner U, Turnwald AM, et al. Direct detection of methicillin-resistant Staphylococcus aureus in clinical specimens by a nucleic acid-based hybridisation assay. Clin Microbiol Infect 2006; 12:1163.
  26. Paule SM, Hacek DM, Kufner B, et al. Performance of the BD GeneOhm methicillin-resistant Staphylococcus aureus test before and during high-volume clinical use. J Clin Microbiol 2007; 45:2993.
  27. Rossney AS, Herra CM, Fitzgibbon MM, et al. Evaluation of the IDI-MRSA assay on the SmartCycler real-time PCR platform for rapid detection of MRSA from screening specimens. Eur J Clin Microbiol Infect Dis 2007; 26:459.
  28. Wolk DM, Picton E, Johnson D, et al. Multicenter evaluation of the Cepheid Xpert methicillin-resistant Staphylococcus aureus (MRSA) test as a rapid screening method for detection of MRSA in nares. J Clin Microbiol 2009; 47:758.
  29. Levi K, Towner KJ. Rapid detection of methicillin-resistant Staphylococcus aureus from screening enrichment broths by real-time PCR. Eur J Clin Microbiol Infect Dis 2005; 24:423.
  30. Daeschlein G, Assadian O, Daxboeck F, Kramer A. Multiplex PCR-ELISA for direct detection of MRSA in nasal swabs advantageous for rapid identification of non-MRSA carriers. Eur J Clin Microbiol Infect Dis 2006; 25:328.
  31. Wagenvoort JH, van de Cruijs MF, Meuwissen CT, et al. Comparison of an enrichment broth-enhanced commercial PCR procedure versus bacteriological culture for separating non-colonized from suspected or colonized MRSA individuals. Eur J Clin Microbiol Infect Dis 2007; 26:155.
  32. Levi K, Towner KJ. Detection of methicillin-resistant Staphylococcus aureus (MRSA) in blood with the EVIGENE MRSA detection kit. J Clin Microbiol 2003; 41:3890.
  33. Francois P, Pittet D, Bento M, et al. Rapid detection of methicillin-resistant Staphylococcus aureus directly from sterile or nonsterile clinical samples by a new molecular assay. J Clin Microbiol 2003; 41:254.
  34. Harbarth S, Masuet-Aumatell C, Schrenzel J, et al. Evaluation of rapid screening and pre-emptive contact isolation for detecting and controlling methicillin-resistant Staphylococcus aureus in critical care: an interventional cohort study. Crit Care 2006; 10:R25.
  35. Harbarth S, Fankhauser C, Schrenzel J, et al. Universal screening for methicillin-resistant Staphylococcus aureus at hospital admission and nosocomial infection in surgical patients. JAMA 2008; 299:1149.
  36. Francois P, Bento M, Renzi G, et al. Evaluation of three molecular assays for rapid identification of methicillin-resistant Staphylococcus aureus. J Clin Microbiol 2007; 45:2011.
  37. Stamper PD, Cai M, Howard T, et al. Clinical validation of the molecular BD GeneOhm StaphSR assay for direct detection of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus in positive blood cultures. J Clin Microbiol 2007; 45:2191.
  38. Hogg GM, McKenna JP, Ong G. Rapid detection of methicillin-susceptible and methicillin-resistant Staphylococcus aureus directly from positive BacT/Alert blood culture bottles using real-time polymerase chain reaction: evaluation and comparison of 4 DNA extraction methods. Diagn Microbiol Infect Dis 2008; 61:446.
  39. Misawa Y, Yoshida A, Saito R, et al. Application of loop-mediated isothermal amplification technique to rapid and direct detection of methicillin-resistant Staphylococcus aureus (MRSA) in blood cultures. J Infect Chemother 2007; 13:134.
  40. Gröbner S, Kempf VA. Rapid detection of methicillin-resistant staphylococci by real-time PCR directly from positive blood culture bottles. Eur J Clin Microbiol Infect Dis 2007; 26:751.
  41. Thomas LC, Gidding HF, Ginn AN, et al. Development of a real-time Staphylococcus aureus and MRSA (SAM-) PCR for routine blood culture. J Microbiol Methods 2007; 68:296.
  42. Wolk DM, Struelens MJ, Pancholi P, et al. Rapid detection of Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) in wound specimens and blood cultures: multicenter preclinical evaluation of the Cepheid Xpert MRSA/SA skin and soft tissue and blood culture assays. J Clin Microbiol 2009; 47:823.
  43. Stratidis J, Bia FJ, Edberg SC. Use of real-time polymerase chain reaction for identification of methicillin-resistant Staphylococcus aureus directly from positive blood culture bottles. Diagn Microbiol Infect Dis 2007; 58:199.
  44. Wang B, Jessamine P, Desjardins M, et al. Direct mecA polymerase chain reaction testing of blood culture bottles growing Gram-positive cocci and the clinical potential in optimizing antibiotic therapy for staphylococcal bacteremia. Diagn Microbiol Infect Dis 2013; 75:37.