We compared the FilmArray RP (Idaho Technology, Inc., Salt Lake City, UT) and the xTAG RVP (Luminex Corporation, Toronto, Canada) multiplex respiratory virus PCR methods for the detection of respiratory viruses in a set of 200 patient specimens frozen at ؊70°C after standard viral culture and antigen detection methods were done. Both systems detected between 40 to 50% more viruses than traditional methods, primarily rhinoviruses and human metapneumovirus. The FilmArray RP detected significantly more total viruses either alone or as part of mixed infections than the xTAG RVP, as well as an additional 21.6% more respiratory syncytial viruses. The xTAG RVP requires 5 to 6 h with 2.5 to 3 h of hands-on time, while the FilmArray RP takes about an hour with 3 to 5 min of hands-on time, making it much easier to perform.Multiplex reverse transcriptase respiratory virus PCR has been shown to be more sensitive than standard respiratory virus culture, direct fluorescent-antigen, and direct enzymelinked immunosorbent assay (ELISA) antigen detection methods (1, 2, 7-9, 13-14, 16, 20). Viral culture is labor-intensive, detects some viruses (e.g., rhinovirus and coronavirus) poorly, and requires 3 to 5 days to detect most agents. Consequently, results are generally not available early in the clinical decisionmaking process. Direct fluorescent-antibody assay (DFA) and chromatographic immunoassays are rapid enough to support real-time clinical decisions, but DFA is highly labor-intensive and chromatographic immunoassays are relatively insensitive. The FilmArray RP multiplex respiratory virus panel uses a pouch system that contains all reagents for the identification of 18 respiratory viruses and 3 bacterial respiratory pathogens in about 1 h after inoculation of a patient sample, obviating both labor and turnaround time (TAT) issues. We compared the performance of the FilmArray RP with that of the FDAcleared Luminex xTAG RVP multiplex panel by using 200 retrospective clinical respiratory virus culture samples.

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We previously observed marked synergy between daptomycin and both rifampin and ampicillin against vancomycin-resistant enterococci (VRE). Because the synergy between daptomycin and ampicillin was observed for 100% of VRE strains with high-level ampicillin resistance (ampicillin MIC of >128 g/ml), we looked for synergy between daptomycin and other ␤-lactams against 18 strains of methicillin-resistant Staphylococcus aureus (MRSA) by employing a time-kill method using Mueller-Hinton broth supplemented to 50 mg of Ca 2؉ /liter. All strains were resistant to oxacillin (16 of 18 strains were resistant at drug concentrations of >256 g/ml), and all strains were susceptible to daptomycin (the MIC at which 90% of the tested isolates were inhibited was 1 g/ml). Daptomycin was tested at concentrations of 2, 1, 0.5, 0.25, 0.125, and 0.0625 g/ml alone or in combination with oxacillin at a fixed concentration of 32 g/ml. Synergy was found for all 18 strains with daptomycin at one-half the MIC in combination with 32 g of oxacillin/ml, and synergy was found for 11 of 18 strains (61%) with daptomycin at one-fourth the MIC or less in combination with oxacillin. At 24 h, the daptomycin-oxacillin combination with daptomycin at one-half the MIC showed bactericidal activity against all 18 strains, and the combination with one-fourth the daptomycin MIC showed bactericidal activity against 9 of 18 strains. We also used a novel screening method to look for synergy between daptomycin and other ␤-lactams. In this approach, daptomycin was incorporated into Ca Daptomycin is a novel lipopeptide antibiotic with bactericidal activity against a wide range of clinically important grampositive bacteria, including vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA). In a recent study, we found synergy between daptomycin and both rifampin and ampicillin against VRE (12a). In that work, a screening technique was used to test daptomycin with 18 other antibiotics, and promising combinations were further tested by time-kill studies. In brief, daptomycin was added to Ca 2ϩ -supplemented Mueller-Hinton broth at subinhibitory concentrations, and the Etest-determined MIC of individual antibiotics on agar containing daptomycin was compared with the MIC on agar without daptomycin. When MRSA strains were studied with this method, combinations of daptomycin and ␤-lactams were found to warrant further study. In this report, we present comparative results for several daptomycin-␤-lactam combinations by the screening method and confirmative time-kill studies using combinations of daptomycin and oxacillin or ampicillin-sulbactam for 18 strains of MRSA. MATERIALS AND METHODSEighteen randomly selected strains of MRSA were obtained from the clinical microbiology laboratory at Shands Hospital at the University of Florida, Gainesville, between January and March 2002. All isolates were tested for relatedness by pulsed-field gel electrophoresis at the Mayo Medical Laboratories, Rochester, Minn. Five isolates were different from ea...

We assessed the reproducibility of the microdilution checkerboard method for measuring antibiotic synergy. Five strains of Pseudomonas aeruginosa were tested with four antibiotic combinations by using 10 replicates each. Twenty-five percent of replicate sets gave discordant classification results (i.e., a 7:3 or worse split in categorization). Determination of the individual MICs of each antibiotic alone was excellent; all 10 replicates were within 1 twofold dilution for 95% of the 80 sets of 10 replicates. The microdilution checkerboard method either should not be used or should be used with at least five replicates per determination, with .80% agreement among the replicates required for classification.The microdilution checkerboard has been one of the traditional methods for the measurement of antibiotic synergy. Synergy has generally been defined as requiring a fourfold reduction in the MIC of both antibiotics in combination, compared with each used alone, i.e., a fractional inhibitory concentration (FIC) index of c0.5 (5). Since there is an inherent 1-dilution variability in the determination of the MIC of each antibiotic used alone (8), this variability is additive and could become significant for the combination wells. We therefore decided to determine how much inherent variability occurs with microdilution checkerboard synergy testing under ideal conditions, namely, replicate microdilution plates inoculated on the same day with the same inoculum by as meticulous a technique as possible. We tested microdilution checkerboard plates prepared by two different methods, using five strains of Pseudomonas aeruginosa and four antibiotic combinations.(This work was presented at the 92nd

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