Chromogenic Media vs Real-Time PCR for Nasal Surveillance of Methicillin-ResistantStaphylococcus aureus

Abstract

Surveillance for methicillin-resistant Staphylococcus aureus (MRSA) colonization can be an important element for infection control programs when managing a multidrug-resistant pathogen such as MRSA. The sensitivity and speed of laboratory testing affects the proportion of appropriate isolation days captured, which determines the success or failure of a MRSA control program. Chromogenic culture, CHROMagar MRSA (BBL, Becton Dickinson, Sparks, MD) and MRSASelect (Bio-Rad, Hercules, CA), with and without broth enrichment and real-time polymerase chain reaction (PCR; BD GeneOhm MRSA, BD Diagnostics, San Diego, CA), were compared and found to have a wide range of sensitivities (78.5%-98.2%), specificities (91.6%-100.0%), and turnaround times (2-72 hours). Real-time PCR provided the most rapid results and demonstrated the highest sensitivity followed by broth-enriched culture and then direct plating for MRSA detection in nasal swabs. There was no substantial difference in the labor required for any of the 3 approaches.

Comparison of clinical methods for the phenotypic detection of Methicillin resistant Staphylococcus aureus: Disc diffusion methods with BrillianceTM MRSA agar

“…Similar performance of a chromogenic medium and RT-PCR has also been reported in another study (Bischof et al, 2009). However, yet another study has reported that molecular techniques give quick results with high sensitivity (Paule et al, 2009). Brilliance TM MRSA agar (Oxoid) is also a good, cost effective medium for the detection of MRSA because cost of screening on conventional culture medium is similar to the cost of chromogenic medium.…”

Methicillin-Resistant Staphylococcus aureus Control in the 21st Century: Laboratory Involvement Affecting Disease Impact and Economic Benefit from Large Population Studies

“…Key to the decision process is selection of a testing system with sufficient sensitivity and result reporting time so that a combination of these factors will enable placing patients in contact precautions for 80% of the time they are in the hospital (9,25,26). This is critical since the most expensive AST program is one where testing is done, but MRSA clinical disease is not reduced, an outcome to be avoided.…”

Cepheid Xpert MRSA Cycle Threshold in Discordant Colonization Results and as a Quantitative Measure of Nasal Colonization Burden

“…Although they are less costly, direct chromogenic agar cultures are insensitive compared to PCR (15,22). Broth enrichment in tryptic soy broth (TSB) prior to plating has been shown to increase the sensitivity of chromogenic techniques but also increases the workload and the time to result, making this method problematic for routine use in the clinical microbiology laboratory (11).…”