Comparison of phenotypic and molecular methods in the detection of methicillin resistant Staphylococcus aureus and its implications

Background: Globally, Staphylococcus aureus is considered the most common cause of nosocomial infections. In recent times, there is a steady rise in the number of methicillin resistant S. aureus (MRSA) isolates. Aim: This study was done to find out the prevalence, antimicrobial sensitivity pattern and evaluation of different methods (cefoxitin disc diffusion [DD] method, Chrom agar and polymerase chain reaction [PCR]) in the detection of MRSA. Materials and Methods: A total of 100 S. aureus isolates from pus samples were identified by standard biochemical techniques. Antimicrobial susceptibility testing was done by Kirby Bauer′s DD method as per Clinical and Laboratory Standards Institute guidelines. D test was done to detect clindamycin resistance. Methicillin resistance was evaluated by cefoxitin DD method, Chrom agar (HiCrome MeReSa agar base and selective supplement) and reverse transcription-PCR. Result: Out of 100 S. aureus isolates, 34% were detected as MRSA by cefoxitin DD method. All these isolates were detected by Chrom agar within 24 h. Additional isolates were not detected even after 48 h of incubation. mecA gene was detected by PCR in all these 34 MRSA isolates. Conclusion: The early detection of MRSA is of prime importance in the prognosis of staphylococcal infections. An integrated awareness program, good hand wash technique, epidemiological studies and effective control measures are the goals for elimination of MRSA in hospitals