Performance of the BD GeneOhm MRSA Achromopeptidase Assay for Real-Time PCR Detection of Methicillin-Resistant Staphylococcus aureus in Nasal Specimens

Abstract

We evaluated the BD GeneOhm MRSA achromopeptidase (ACP) assay, which incorporates a new specimen preparation approach. A total of 1,216 leftover nasal samples were tested; using culture as the gold standard, the sensitivity and specificity were 92% and 94.6%, respectively. The new lysis method provides good sensitivity and simplifies specimen preparation.Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of health care-associated infections and is responsible for increased hospital stays with high financial cost (7,19,24). In fact, by 2005 MRSA had a higher mortality rate than tuberculosis, salmonella infection, influenza, and HIV-AIDS combined within the United States (5). Moreover, Delorme and colleagues recently reported an increase of MRSA infections and disease rate in long-term care facility (LTCF) residents between 2006 and 2007 (6). There has been some success reported in the reduction of invasive infection since 2005, but most of the improvement was related to bloodstream infection and may be related to improved central venous catheter management in acute care hospitals (11). Another recent study has shown that a reduction in the rate of MRSA invasive infection must involve more than a general improvement in basic infection control practice, such as improved hand hygiene, since improved hand hygiene did not lower hospitalacquired MRSA colonization (14).MRSA detection is often followed by either decolonization or isolation to reduce MRSA prevalence within hospitals and in the community (4,8,10). In an elegant crossover study of the impact rapid testing has on MRSA transmission, Hardy and colleagues demonstrated significantly reduced transmission when surveillance testing was done using a real-time PCR assay, as opposed to no significant impact when routine, culture-based testing was utilized by the laboratory (9). Thus, rapid and reliable screening tests for MRSA detection are very important. Real-time PCR assays are fast, reliable, and accurate, which has been useful to reduce the incidence of MRSA disease (19,20).Paule and colleagues developed an achromopeptidase (ACP) lysis procedure for high-volume testing and compared its performance with the original BD GeneOhm MRSA lysis kit method (IDI-MRSA assay). The study results demonstrated that the assay performed equally well using both procedures (18). BD Diagnostics subsequently developed an ACP lysis method for use with the BD GeneOhm MRSA kit. The purpose of this current study was to assess the BD GeneOhm MRSA ACP assay for direct detection of MRSA in nasal specimens as part of an application to the U.S. FDA for clearance as an in vitro diagnostic device.Nasal swabs were collected using double-headed BBL culture swabs with liquid Stuart (Becton Dickinson, Sparks, MD) or liquid Amies (Becton Dickinson) transport medium; singleheaded Amies gel swabs without charcoal (Becton Dickinson) were also included. Excess, deidentified nasal specimens were used for testing after routine laboratory procedures were completed. The subjects enrolled ...

Comparison of the BD Max Methicillin-Resistant Staphylococcus aureus (MRSA) Assay and the BD GeneOhm MRSA Achromopeptidase Assay with Direct- and Enriched-Culture Techniques Using Clinical Specimens for Detection of MRSA

“…The observed differences in sensitivity and specificity between the two molecular assays were not statistically significant. The test characteristics of the BD Max MRSA assay are in the range of what has been observed before for the BD GeneOhm MRSA assay (3,8,11,20) and the ACP assay (17)(18)(19). Comparison of the two molecular assays gave a Cohen's kappa of 0.816, indicating good agreement.…”

“…Retesting resolved 29 of the tests. The unresolved rate of 4.2% is higher than reported (17) or indicated in the packaging insert but in the range that has been observed by others (1,16). Only 11 of the initial BD Max MRSA tests (1.4%) were unresolved, and all were resolved with retesting (difference between tests, P Ͻ 0.01, two-sided Fisher's exact test).…”

“…Positive predictive value (PPV) was 83.8% for the BD Max MRSA assay and 69.8% for the BD GeneOhm MRSA ACP assay (P ϭ 0.19, two-sided Fisher's exact test). The PPV for the BD GeneOhm MRSA ACP assay is within the range that has been observed before (3,8,(17)(18)(19)(20)(21); the slightly higher PPV for the new BD Max MRSA assay might help to avoid unnecessary infection control measures, especially in low-prevalence settings. Negative predictive values (NPVs) were high for both assays (99.7%).…”

“…It combines cell lysis, nucleic acid extraction, PCR setup, amplification, and detection in a single machine, thereby facilitating use of molecular tests. The aim of this study was to evaluate the BD Max MRSA assay, compared with the widely used BD GeneOhm MRSA achromopeptidase (ACP) assay (5,11,17,18,20), using direct and enriched culture as the reference method for detection of MRSA.…”

“…It combines cell lysis, nucleic acid extraction, PCR setup, amplification, and detection in a single machine, thereby facilitating use of molecular tests. The aim of this study was to evaluate the BD Max MRSA assay, compared with the widely used BD GeneOhm MRSA achromopeptidase (ACP) assay (5,11,17,18,20), using direct and enriched culture as the reference method for detection of MRSA.The study was conducted at the 2,000-bed tertiary care University Hospital Heidelberg from October 2011 to January 2012. Screening swabs (BBL CultureSwab, liquid Stuart; BD) collected from patients admitted to intermediate and intensive care units, from patients admitted from external hospitals, and from surgical patients with wound infections were used.…”