Objective PCR detection of methicillin-resistant Staphylococcus aureus (MRSA) colonisation was introduced in critical care areas of our hospital as being a sensitive/specific test with the benefit of rapid results compared with culture. When introduced on our neonatal unit (NNU), real-time PCR was compared with culture methods to detect MRSA nasal colonisation in newborn infants.
Methods Paired nasal swabs were collected weekly from infants on NNU over a 4-month period (September 2007 to January 2008). One swab was cultured and the other tested by PCR. The results were compared.
Results During this period, a total of 455 paired nasal swabs were taken (range 0–15 per infant). Three infants were known to be colonised with MRSA at the beginning and these were included. In total, there were 10 positive PCR results from five infants. In 4/5 of these infants MRSA was cultured from a nasal swab taken at the same time. The culture result took 1–2 days longer to obtain than the PCR result. There were no infants who cultured MRSA from nasal swabs when the PCR was negative (sensitivity 100%, specificity 98% compared with culture). One infant had a positive PCR result and isolated a sensitive S aureus by culture. This organism was later demonstrated to give a false positive PCR result.
Conclusion PCR appears a sensitive and specific method of detecting MRSA nasal colonisation with a rapid result 1–2 days before traditional culture. This gives prompt infection control information and may be particularly helpful in determining infection control measures for infants transferred in from other units.