Article

Comparison of MRSASelect Agar, CHROMagar Methicillin-Resistant Staphylococcus aureus (MRSA) Medium, and Xpert MRSA PCR for detection of MRSA in Nares: diagnostic accuracy for surveillance samples with various bacterial densities.

Southern Arizona VA Health Care System, Tucson, Arizona, USA.
Journal of clinical microbiology (Impact Factor: 4.23). 10/2009; 47(12):3933-6. DOI: 10.1128/JCM.00601-09
Source: PubMed

ABSTRACT Rapid laboratory methods provide optimal support for active surveillance efforts to screen for methicillin-resistant Staphylococcus aureus (MRSA). Most laboratories struggle to determine the optimal use of resources, considering options to balance cost, speed, and diagnostic accuracy. To assess the performance of common methods, the first comparison of MRSASelect agar (MS) and CHROMagar MRSA (CA), with and without broth enrichment followed by a 24-h subculture to MS, was performed. Results were compared to those of the Xpert MRSA assay. For direct culture methods, the agreement between MS and CA was 98.8%. At 18 h, direct MS identified 93% of all positive samples from direct culture and 84% of those identified by the Xpert MRSA. For Trypticase soy broth-enriched MS culture, incubated overnight and then subcultured for an additional 24 h, the agreement with Xpert MRSA was 96%. The agreement between direct MS and Xpert MRSA was 100% when semiquantitative culture revealed a bacterial density of 2+ or greater; however, discrepancies between culture and Xpert MRSA arose for MRSA bacterial densities of 1+ or less, indicating low density as a common cause of false-negative culture results. Since 1+ or less was established as the most common MRSA carrier state, broth enrichment or PCR may be critical for the identification of all MRSA carriers who may be reservoirs for transmission. In this active-surveillance convenience sample, the use of broth enrichment followed by subculture to MS offered a low-cost but sensitive method for MRSA screening, with performance similar to that of Xpert MRSA PCR.

1 Bookmark
 · 
109 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Cluster randomised crossover trial with seven wards randomly allocated to intervention or control arm.
    PLoS ONE 01/2014; 9(5):e96310. · 3.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A meticillin-resistant Staphylococcus aureus (MRSA) polymerase chain reaction assay (Xpert(®) MRSA, Cepheid) was assessed for point-of-care testing (POCT) used by healthcare assistants in an orthopaedic pre-admission clinic and on a vascular ward to reduce turnaround time. POCT results were compared with the routine swabs taken for culture. The POCT assay was easy to use, the turnaround time for negative results was greatly reduced, and sensitivity was 75.0% in the pre-admission clinic and 80.0% in the vascular ward. There were 27 POCT-positive/culture-negative results, but there was no evidence of MRSA infection or colonization in these patients for at least a year post procedure. POCT for MRSA colonization performed beyond the laboratory has important advantages over laboratory-based methods and should be explored further.
    Journal of Hospital Infection 04/2014; · 2.78 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Background: The Xpert® CT/NG (Cepheid Sunnyvale, CA) is a rapid, fully automated real-time polymerase chain reaction test that simultaneously detects Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG).It has high sensitivity and specificity, but also includes a Specimen Adequacy Control (SAC). SAC controls for false negative results by confirming adequate patient sample and appropriate testing conditions. SAC is quantified by its cycle threshold (Ct ), the number of cycles required to detect the presence of a single copy human gene. A lower SAC indicates an earlier Ct and more human cellular material detected. Our objectives were to describe the frequency and distribution of SAC Ct values and observe any correlations with detected infections. Methods: Urine samples from 1382 HIV-1-infected pregnant women, collected at the time of labor/delivery underwent Xpert® CT/NG testing. Mean SAC Ct values and standard deviation (SD) were calculated. Student’s t-test was used to compare mean SAC Ct values to a reference of urine samples negative for CT and NG. Results: The urine CT positivity was 17.9% (248/1382) and NG, 4.6% (63/1382). The mean SAC Ct value in urine from women without CT or NG was 28.09 (SD: 4.12) and higher than the mean SAC Ct value for CT positive specimens (27.29, SD: 3.84(P=.0054)), NG positive specimens (26.23, SD: 3.09(P<.0001)), and specimens positive for both CT and NG (26.41, SD: 3.01(P=.0027)). Conclusion: Lower SAC Ct values were significantly associated with chlamydial and gonococcal infections. Further studies should be conducted to determine the utility of SAC Ct values for identifying the presence of increased human cellular material and infection.
    Journal of Microbiology & Experimentation. 08/2014; 1(4):26.

Full-text

Download
39 Downloads
Available from
Jun 1, 2014