Acta Scientific Medical Sciences (ASMS)(ISSN: 2582-0931)

Research Article Volume 6 Issue 6

Evaluation of a Chromogenic Medium for the Identification and Isolation of MRSA

Ede Tyrell1*, Lorenzo Richards1, Tanesha Mentore1, Shemuel Ben Lewi1 and Nazara Roach2

1School of Allied Health, College of Medical Sciences, University of Guyana, Guyana
2Eureka Medical Labs, Guyana

*Corresponding Author: Ede Tyrell, Lecturer, School of Allied Health, College of Medical Sciences, University of Guyana, Guyana.

Received: April 18, 2022; Published: May 20, 2022


Introduction: We sought to evaluate the screening ability of the chromogenic medium, HardyCHROMTM MRSA, for the identification of Methicillin Resistant Staphylococcus aureus (MRSA) from clinical specimens at 24 hours and 48 hours of incubation.

Materials and Methods: 100 Staphylococcus aureus isolates were obtained from 162 non-repetitive clinical specimens which included: pus aspirates, blood cultures, urine; ear, wound and vaginal swabs. Stool specimens were excluded due to the possible interference of commensals. Suspected isolates of S. aureus were confirmed using Mannitol Salt Agar (MSA) and the coagulase test.

Two methods were compared for the detection of MRSA: (1) The Reference method -Kirby-Bauer disk diffusion method with a 30 (µg) cefoxitin disk on Mueller Hinton Agar (MHA) and (2) The Test method – observation of HardyCHROM™ MRSA after 24 and 48 hours. For the Reference method, a zone diameter zone diameter of ≤21 mm was an indication that the isolate was MRSA, while ≥22 mm was identified as Methicillin Sensitive Staphylococcus aureus (MSSA). Pink to magenta colonies on HardyCHROM™ MRSA were interpreted as MRSA. No growth after 48 hours was documented as MSSA.

Results: A total of 100 Staphylococcus aureus isolates, obtained from 162 non-repetitive clinical specimens were processed. The specimens were mainly pus aspirates (36%), blood cultures (27%) and wound swabs (13%). After 24 hours, the sensitivity, specificity, PPV and NPV of HardyCHROM™ MRSA were 96.9%, 5.6%, 64.6% and 50.0% respectively. At 48 hours, the sensitivity, specificity, PPV and NPV of HardyCHROM™ MRSA were 96.9%, 0%, 63.3% and 0%, respectively. Using McNemar’s test, to compare the two tests, a significant difference (p value <0.05) was found at 24 hours and 48 hours incubation

Conclusions: We concluded that because of the high sensitivity of HardyCHROM™ MRSA, this medium would be effective in the screening of patients or staff to identify persons with an MRSA infection or those carrying MRSA.

Keywords: Methicillin Resistant; Staphylococcus aureus; Chromogenic Media; Screening; Clinical Specimens; Identification


  1. Algammal AM., et al. “Methicillin-Resistant Staphylococcus aureus (MRSA): One Health Perspective Approach to the Bacterium Epidemiology, Virulence Factors, Antibiotic-Resistance, and Zoonotic Impact”. Infection and Drug Resistance 13 (2020): 3255-3265.
  2. Stone ND., et al. “Southeast Veterans Affairs Long-Term Care Methicillin-Resistant Staphylococcus aureus Methicillin-resistant Staphylococcus aureus (MRSA) nasal carriage in residents of Veterans Affairs long-term care facilities: role of antimicrobial exposure and MRSA acquisition”. Infection Control and Hospital Epidemiology 33.6 (2012): 551-557.
  3. Eveillard M., et al. “Carriage of Methicillin-Resistant Staphylococcus aureus among hospital employees: Prevalence, Duration, and Transmission to Households”. Infection Control and Hospital Epidemiology2 (2004): 114-120.
  4. Aung K., et al. “Prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in retail food in Singapore”. Antimicrobial Resistance and Infection Control94 (2017).
  5. Datta R and Huang S. “Risk of infection and death due to methicillin-resistant Staphylococcus aureus in long-term carriers”. Clinical Infectious Diseases: An Official Publication of the Infectious Diseases Society of America2 (2008): 176-181.
  6. Jenkins SG and Schuetz AN. “Current concepts in laboratory testing to guide antimicrobial therapy”. Mayo Clinic Proceedings3 (2012): 290-308.
  7. Creamer E., et al. “The effect of rapid screening for methicillin-resistant Staphylococcus aureus (MRSA) on the identification and earlier isolation of MRSA-positive patients”. Infection Control and Hospital Epidemiology4 (2010): 374-381.
  8. Gould I., et al. “Costs of healthcare-associated methicillin-resistant Staphylococcus aureus and its control”. Clinical Microbiology and Infection12 (2010): 1721-1728.
  9. Hart I. “A test for the early detection of MRSA: clinical benefits and financial savings” (2004).
  10. Adaleti R., et al. “Comparison of polymerase chain reaction and conventional methods in detecting methicillin-resistant Staphylococcus aureus”. Journal of Infection in Developing Countries1 (2008): 46-50.
  11. Skov R., et al. “Phenotypic detection of mecC-MRSA: cefoxitin is more reliable than oxacillin”. Journal of Antimicrobial Chemotherapy1 (2014) :133-135.
  12. Anand KB., et al. “Comparison of cefoxitin disc diffusion test, oxacillin screen agar, and PCR for mecA gene for detection of MRSA". Indian Journal of Medical Microbiology1 (2009): 27-29.
  13. Xu Z., et al. “Chromogenic media for MRSA diagnostics." Molecular Biology Reports11 (2016): 1205-1212.
  14. Merlino J., et al. “New Chromogenic Identification and Detection of Staphylococcus aureus and Methicillin-Resistant aureus”. Journal of Clinical Microbiology 38.6 (2000): 2378-2380.
  15. Brennan G., et al. “Evaluation of commercial chromogenic media for the detection of methicillin-resistant Staphylococcus aureus”. Journal of Hospital Infection3 (2016): 287-292.
  16. Malhotra-Kumar S., et al. “Current Trends in Rapid Diagnostics for Methicillin-Resistant Staphylococcus aureus and Glycopeptide-Resistant Enterococcus species”. Journal of Clinical Microbiology5 (2008): 1577-1587.
  17. Food and Drug Administration. “510 (k) Substantial Equivalence Determination Decision Summary Instrument Only” (2011).
  18. Clinical and Laboratory Standards Institute. M100S27_sample. “Performance standards for antimicrobial susceptibility testing. Performance Standards for Antimicrobial Susceptibility Testing”. (2017).
  19. Wong HB and Lim GH. “Measures of diagnostic accuracy: Sensitivity, specificity, PPV and NPV. Proceedings of Singapore Healthcare”. SGH-PGMI Press (2011).
  20. Monecke S., et al. “Population Structure of Staphylococcus aureus from Trinidad and Tobago”. PLoS ONE2 (2014): e89120.
  21. Brown PD and Ngeno C. “Antimicrobial resistance in clinical isolates of Staphylococcus aureus from hospital and community sources in southern Jamaica”. International Journal of Infectious Diseases3 (2007): 220-225.
  22. Orrett FA and Land M. “Methicillin-resistant Staphylococcus aureus prevalence: current susceptibility patterns in Trinidad”. BMC Infectious Diseases 6 (2006): 83.
  23. Rossato AM., et al. “Resistance profile to antimicrobials agents in methicillin-resistant Staphylococcus aureus isolated from hospitals in South Brazil between 2014-2019”. Revista da Sociedade Brasileira de Medicina Tropical 53 (2020).
  24. Center for Disease Control and Prevention. “Methicillin-resistant Staphylococcus aureus (MRSA): Laboratory Testing for MRSA”. (2018).
  25. Hartman B and Tomasz A. “Expression of methicillin resistance in heterogenous strains of Staphylococcus aureus”. Antimicrobial Agents and Chemotherapy1 (1986): 85-92.
  26. Dupieux C., et al. “Detection of mecC-positive Staphylococcus aureus: what to expect from immunological tests targeting PBP2a?" Journal of Clinical Microbiology6 (2017): 1961-1963.
  27. Ballhausen B., et al. “The mecA Homolog mecC confers resistance against β-Lactams in Staphylococcus aureus irrespective of genetic strain background”. Antimicrobial Agents and Chemotherapy7 (2014): 3791-3798.
  28. García-Álvarez L., et al. “Methicillin-resistant Staphylococcus aureus with a novel mecA homologue in human and bovine populations in the UK and Denmark: a descriptive study”. The Lancet Infectious Diseases 8 (2011): 595-603.


Citation: Ede Tyrell., et al. “Evaluation of a Chromogenic Medium for the Identification and Isolation of MRSA”.Acta Scientific Medical Sciences 6.6 (2022): 231-239.


Copyright: © 2022 Ede Tyrell., et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


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