Controlled Evaluation of the IDI-MRSA Assay for Detection of Colonization by Methicillin-Resistant Staphylococcus aureus in Diverse Mucocutaneous Specimens

Abstract

Rapid and reliable detection of methicillin-resistant Staphylococcus aureus (MRSA) carriers is crucial for the effective control of MRSA transmission in healthcare facilities. The aim of this study was to verify the performance of the IDI-MRSA real-time PCR assay for direct MRSA detection in diverse mucocutaneous swabs from hospitalized patients. Swabs from nares (n ‫؍‬ 522) and skin or other superficial sites (n ‫؍‬ 478) were prospectively collected for MRSA screening from 466 patients admitted to an 858-bed teaching hospital. Swabs were inoculated onto selective chromogenic MRSA-ID agar, buffer extraction solution for IDI-MRSA assay, and enrichment broth. MRSA was detected by culture in 100 specimens from 47 patients. Compared to enrichment culture, the sensitivity and specificity of the PCR assay were 81.0 and 97.0%, respectively, and its positive and negative predictive values were 75.0 and 97.9%, respectively. The IDI-MRSA assay was more sensitive on swabs from nares (90.6%) than from other body sites (76.5%, P < 0.01). The PCR assay detected MRSA in 42 of 47 patients with culture positive study samples. Of 26 patients with culture-negative but PCR-positive study samples, 11 were probable true MRSA carriers based on patient history and/or positive culture on a new sample. The median turnaround time for PCR results was 19 h versus 3 days for agar culture results and 6 days for enrichment culture results. These data confirm the value of IDI-MRSA assay for rapid screening of MRSA mucocutaneous carriage among hospitalized patients. Cost-effectiveness studies are warranted to evaluate the impact of this assay on infection control procedures in healthcare settings.Methicillin-resistant Staphylococcus aureus (MRSA) is one of the major nosocomial pathogens responsible for a wide spectrum of infections, including skin and soft tissue infections, pneumonia, bacteraemia, surgical site infections, and catheterrelated infections. In Europe, up to 50% of nosocomial bloodstream S. aureus infections are due to MRSA. In Belgium, the proportion of MRSA isolates from blood cultures in hospitalized patients has risen from 22% in 1999 to 31.4% in 2005 (8). MRSA isolation from an inpatient is associated with increased risk of nosocomial infection and an excess of morbidity and hospitalization costs (4). The main mode of MRSA transmission is from MRSA-colonized or -infected patients to another one through indirect contact via the transiently colonized hands of healthcare workers. Therefore, the rapid identification of MRSA carriers is essential for implementation of targeted infection control measures to prevent dissemination. Active surveillance cultures for MRSA are now part of clinical practice recommendations both in Europe and the United States (16,18,22). The current Belgian recommendations for MRSA screening are to culture swabs from nares and other skin and mucosal sites with enrichment broths and selective media. However, the results of the conventional screening methods are generally not available before 48 h, in spite ...

Rapid Detection of Methicillin-Resistant Staphylococcus aureus (MRSA) in Diverse Clinical Specimens by the BD GeneOhm MRSA Assay and Comparison with Culture

“…Seventeen initially inhibited specimens (1.0%) were eventually included in the data analysis because results were available after freezing and repeating the PCR. Our initial inhibition rate (1.4%) is well in line with that observed by others using Stuart's liquid medium (8,26). Some authors (5,16,17) who used an agar-based medium reported higher inhibition rates and, therefore, pretreated the swabs before performing PCR.…”

“…This may be explained by the use of enrichment broth as the reference method, which yields conceivably a higher sensitivity than does direct plating (17,20,23). Overall sensitivity of PCR for all swabs (n ϭ 1,595) in Amies agar corresponds well to the results reported previously using Stuart's medium (sensitivity ranging from 81% to 92.3%) (3,8,19,22,26). However, a direct comparison of Amies agar with Stuart's medium for the same clinical specimens has not been undertaken yet.…”

Comparison of the BD GeneOhm Methicillin-Resistant Staphylococcus aureus (MRSA) PCR Assay to Culture by Use of BBL CHROMagar MRSA for Detection of MRSA in Nasal Surveillance Cultures from an At-Risk Community Population

“…The high NPV in this study (97.9%) and those reported by others (7,15,18,21) suggests that this assay provides a rapid method for the identification of persons who are not colonized with MRSA and in that context is likely to be useful for epidemiologic or surveillance activities, whether in a community setting as described in this evaluation or in a health care environment.…”

Rapid Differentiation of Methicillin-Susceptible Staphylococcus aureus from Methicillin-Resistant S. aureus and MIC Determinations by Isothermal Microcalorimetry

“…One of the reasons for this is the time required for detection, which is still at least 48 h by conventional methods (4,11). A faster MRSA detection method would allow faster interventions and rapid implementation of targeted infection control measures (3,6,9).…”