Research article

Evaluation of BacLite Rapid MRSA, a rapid culture based screening test for the detection of ciprofloxacin and methicillin resistant S. aureus (MRSA) from screening swabs

Gemma Johnson¹ , Michael R Millar^1,2 , Stuart Matthews³ , Margaret Skyrme³ , Peter Marsh⁴ , Emma Barringer⁵ , Stephen O'Hara⁵ and Mark Wilks^1,2

¹  Division of Infection, Barts and the London NHS Trust, London, UK

²  Centre for Infectious Diseases, Institute of Cell and Molecular Sciences, Barts and the London School of Medicine and Dentistry, Queen Mary, University of London, UK

³  Department of Microbiology, Salisbury District Hospital, Salisbury, UK

⁴  Health Protection Agency South East, Southampton General Hospital, Southampton, UK

⁵  Acolyte Biomedica, Porton Down Science Park, Salisbury, UK

author email corresponding author email

BMC Microbiology 2006, 6:83doi:10.1186/1471-2180-6-83

Published:	29 September 2006

Abstract

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is a major nosocomial pathogen worldwide. The need for accurate and rapid screening methods to detect MRSA carriers has been clearly established. The performance of a novel assay, BacLite Rapid MRSA (Acolyte Biomedica, UK) for the rapid detection (5 h) and identification of hospital associated ciprofloxacin resistant strains of MRSA directly from nasal swab specimens was compared to that obtained by culture on Mannitol salt agar containing Oxacillin (MSAO) after 48 h incubation.

Results

A total of 1382 nasal screening swabs were tested by multiple operators. The BacLite Rapid MRSA test detected 142 out of the 157 confirmed MRSA that were detected on MSAO giving a diagnostic sensitivity of 90.4, diagnostic specificity of 95.7% and a negative predictive value of 98.7%. Of the 15 false negatives obtained by the BacLite Rapid MRSA test, seven grew small amounts (< 10 colonies of MRSA) on the MSAO culture plate and five isolates were ciprofloxacin sensitive. However there were 13 confirmed BacLite MRSA positive samples, which were negative by the direct culture method, probably due to overgrowth on the MSAO plate. There were 53 false positive results obtained by the BacLite Rapid MRSA test at 5 h and 115 cases where MRSA colonies were tentatively identified on the MSAO plate when read at 48 h, and which subsequently proved not to be MRSA.

Conclusion

The Baclite MRSA test is easy to use and provides a similar level of sensitivity to conventional culture for the detection of nasal carriage of MRSA with the advantage that the results are obtained much more rapidly.