Comparison of different phenotypic and molecular methods for detection of methicillin-resistant Staphylococcus aureus in intensive care patients.

Detection of methicillin-resistant Staphylococcus aureus (MRSA) has been problematic ever since its discovery. This work was performed to evaluate the effectiveness of different phenotypic methods for MRSA detection in intensive care patients. Three hundred and eighty-nine specimens from 100 patients were inoculated onto mannitol salt agar. All S. aureus isolates were examined by four selective culture media [ORSAB, MSO, MSA-Cefox, OAS], two disc diffusion methods [CDD and ODD], and MicroScan panel for MRSA. Polymerase chain reaction (PCR) for mecA gene was performed as the gold standard. S. aureus isolates were revealed from 56 patients, 41 of them were found to be MRSA by PCR. CDD yielded the best sensitivity (97.6%), followed by ODD and MSA-Cefox (92.7%). CDD, MSA-Cefox and OAS showed the best specificity (100%). In conclusion, MSA-Cefox and CDD showed improved sensitivity and excellent specificity compared to other methods. It is advisable to use the two methods for MRSA detection if PCR is not available.