Screening for colonization with methicillin-resistant Staphylococcus aureus (MRSA) is a key aspect of infection control to limit the nosocomial spread of this organism. Current methods for the detection of MRSA in clinical microbiology laboratories, including molecularly based techniques, require a culture step and the isolation of pure colonies that result in a minimum of 20 to 24 h until a result is known. We describe a qualitative in vitro diagnostic test for the rapid detection of MRSA directly from nasal swab specimens (IDI-MRSA; Infectio Diagnostic, Inc., Sainte-Foy, Québec, Canada), based upon a real-time PCR and direct detection of MRSA via amplicon hybridization with a fluorogenic target-specific molecular beacon probe. Samples from 288 patients were analyzed for the presence of MRSA with the IDI-MRSA assay, compared to detection by either direct plating or enrichment broth selective culture methods. The diagnostic values for this MRSA screening method were 91.7% sensitivity, 93.5% specificity, 82.5% positive predictive value, and 97.1% negative predictive value when compared to culture-based methods. The time from the start of processing of specimen to result was approximately 1.5 h. In our hands, the IDI-MRSA assay is a sensitive and specific test for detection of nasal colonization with MRSA and providing for same-day results, allowing more efficient and effective use of infection control resources to control MRSA in health care facilities.

We evaluated the Prodesse ProFlu-1 real-time reverse transcription-PCR multiplex assay with the SmartCycler instrument for the detection of human respiratory syncytial virus (RSV) and influenza A and B viruses in comparison to conventional cell culture and antigen immunoassays with the BD Directigen A؉B and Binax NOW RSV assays over two successive respiratory virus seasons. Ninety-two percent of the 361 specimens tested were nasopharyngeal aspirates obtained from individual patients, of which 119 were positive for RSV and 59 were positive for influenza virus. The median age of the patients whose specimens were positive for RSV and influenza virus were 6.3 months and 42.4 years, respectively. The specificity of all of the methods tested was >99%, and the individual sensitivities of NOW RSV, RSV culture, Directigen A؉B, influenza virus culture, and the Proflu-1 PCR for influenza/RSV were 82% (95% confidence interval [CI], 73 to 88), 57% (95% CI, 44 to 69), 59% (95% CI, 44 to 72), 54% (95% CI, 38 to 69), and 98% (95% CI, 93 to 100)/95% (95% CI, 85 to 99), respectively. In a clinical setting where viral isolation is performed to confirm rapid antigen immunoassay results for these common respiratory viruses, one-step real-time reverse transcriptase PCR testing can be a more sensitive and timely confirmatory method.Human respiratory syncytial virus (RSV) and influenza A and B viruses are respiratory pathogens associated with substantial morbidity and mortality annually (43). Virtually all children become infected with RSV within 2 years after birth, and 1% require hospitalization (15). Although the importance of RSV as a cause of pneumonia and brochiolitis in young children is well recognized (21), the most serious morbidity and highest mortality associated with both RSV and influenza virus circulation occurs disproportionately among elderly persons (43). The first-line tests used to detect these virus infections in many hospitals are antigen-based immunoassays. It has been demonstrated that antigen immunoassays have exceedingly poor sensitivity in detecting RSV and influenza virus infections in the elderly, seriously limiting their utility for detecting and confirming institutional or community outbreaks (7,13,38). This study was intended to evaluate the performance of viral isolation in cell culture, one-step real-time multiplex reverse transcription-PCR (RT-PCR), and antigen immunoassays for the detection of influenza virus and RSV in respiratory specimens from adults and children during two respiratory virus seasons. MATERIALS AND METHODS Specimens.Upper respiratory tract specimens were collected from 353 individual symptomatic patients during two successive winter respiratory virus seasons encompassing

The processes involved in cell death are complex, and individual techniques measure specific fractions of the total population. The interaction of Candida albicans with amphotericin B was measured with fluorescent probes with different cellular affinities. These were used to provide qualitative and quantitative information of physiological parameters which contribute to fungal cell viability. SYBR Green I and 5,(6)-carboxyfluorescein were used to assess membrane integrity, and bis-(1,3-dibutylbarbituric acid)trimethine oxonol and 3,3-dihexyloxacarbocyanine iodide were used to evaluate alterations in membrane potential. The fluorescent indicators were compared with replication competency, the conventional indicator of viability. By using these tools, the evaluation of the response of C. albicans to amphotericin B time-kill curves delineated four categories which may represent a continuum between alive and dead. The data showed that replication competency (CFU per milliliter) as determined by conventional antifungal susceptibility techniques provided only an estimate of inhibition. Interpretation of fluorescent staining characteristics indicated that C. albicans cells which were replication incompetent after exposure to greater than 0.5 μg of amphotericin B per ml still maintained degrees of physiological function.

Currently, serological assays using either indirect immunofluorescence assay or enzyme-linked immunosorbent assay (ELISA) are performed to evaluate the status of Epstein-Barr virus (EBV) infection in humans. Although these methods are reliable, they are limited to testing an antibody response to a single viral antigen per reaction, thus necessitating a panel of assays to complete the evaluation. In contrast, a new bead-based method (BioPlex 2200; Bio-Rad Laboratories, Hercules, Calif.) can analyze the humoral response to multiple antigens in a single tube. This approach potentially reduces overall cost, turnaround time, and sample volume. The aim of this study was to evaluate the multiplexed EBV serologic assays performed on the BioPlex 2200 platform compared to results of conventional heterophile and ELISA-based assays. A total of 167 nonconsecutive, stored serum samples from adult and pediatric patients submitted for EBV serologic studies were used in the evaluation. Concordance between results generated by the BioPlex 2200 system and conventional assays was calculated. The anti-EA-D assay had the lowest concordance at 91%. The BioPlex 2200 system showed 97% agreement with conventional heterophile and anti-nuclear antigen assays and 92% agreement with the anti-VCA IgG and immunoglobulin M assays. Agreement between the BioPlex 2200 system and conventional testing was 92% with respect to categorization of acute versus nonacute EBV disease. The correlation between these two systems with regard to assignment into one of four categories of EBV status was also good (82%). In summary, there is excellent correlation between contemporary EBV serologic testing and the BioPlex 2200 system.

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A comparative evaluation of the reference National Committee for Clinical Laboratory Standards (NCCLS) broth microdilution method with a novel fluorescent carboxyfluorescein diacetate (CFDA)-modified microdilution method for the susceptibility testing of fluconazole was conducted with 68 Candida strains, including 53 Candida albicans, 5 Candida tropicalis, 5 Candida glabrata, and 5 Candida parapsilosis strains. We found trailing endpoints and discordant fluconazole MICs of <8 g/ml at 24 h and of >64 g/ml at 48 h for 12 of the C. albicans strains. These strains satisfy the definition of the low-high MIC phenotype. All 12 low-high phenotype strains were correctly shown to be susceptible at 48 h with the CFDA-modified microdilution method. For the 41 non-low-high phenotype C. albicans strains, the CFDA-modified microdilution method yielded 97.6% (40 of 41 strains) agreement within ؎1 dilution at 24 h compared with the reference method and 92.7% (38 of 41 strains) agreement within ؎1 dilution at 48 h compared with the reference method. The five strains each from C. tropicalis, C. glabrata, and C. parapsilosis that were tested showed 100% agreement within ؎2 dilutions for the two methods being evaluated.Candida is the fourth most common cause of nosocomial bloodstream infection in the United States (2, 4), and the rate of primary bloodstream infections continue to increase (3, 9). In the Americas, Candida albicans is the species most frequently isolated from the bloodstream (16). Candidemia is often difficult to diagnose and refractory to therapy. The attributable mortality rate is 38% in the United States (28) and between 19 and 23% in Canada (9,25,29).Use of the broad-spectrum antifungal fluconazole for the treatment of serious systemic Candida infections has increased. Fluconazole is a less toxic alternative to amphotericin B and has been recommended as primary therapy for candidemia in nonneutropenic and stable neutropenic patients who have not received prior fluconazole treatment and in whom Candida krusei is unlikely (5, 24). In vitro susceptibility testing for fluconazole is of clinical importance, as therapeutic success depends substantially on achieving plasma fluconazole levels that are sufficiently higher than MICs (22).Despite great advances in the standardization of antifungal susceptibility testing, azole endpoint determination continues to be problematic and subjective and a major source of interlaboratory variability (6, 18, 23). The trailing-growth phenomenon is often responsible for these difficulties, whereby partial inhibition of fungal growth occurs over the range of azole concentrations (6,13,14,23).Previous work has demonstrated the utility of using fluorescent dyes to assess the viability of C. albicans exposed to amphotericin B (10). We have investigated the use of the vitalityspecific dye carboxyfluorescein diacetate (CFDA) in the standardized NCCLS M27-A broth microdilution method (12) to assess the susceptibility of Candida spp. to fluconazole. In this study we compared the NCCLS microdilu...

We performed a blinded study to compare repetitive-sequence PCR and multilocus sequence typing for genotyping hospital-and community-acquired methicillin-resistant Staphylococcus aureus (MRSA). The MRSA strains that were sequence type 8 (ST8), staphylococcal cassette chromosome mec (SCCmec) type IV, and Panton-Valentine leukocidin-positive clustered separately from those that were ST5 and SCCmec type II.

Amphotericin B treatment was previously shown to inhibit Candida albicans reproduction and reduce the fluorescence of vitality-specific dyes without causing a corresponding increase in the fluorescence of the mortality-specific dyes bis-(1,3-dibutylbarbituric acid)trimethine oxonol and SYBR Green ⌱. In the present study, we have confirmed these results and have shown that the numbers of CFU are reduced by 99.9% by treatment with 0.5 g of amphotericin B per ml for 10 h at 35°C. This reduction was not due to fungal cell death. First, the level of reduction of the tetrazolium salt 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium hydroxide increased in the presence of concentrations of amphotericin B that caused greater than 90% reductions in the numbers of CFU. Second, fungal cells treated with amphotericin B at a concentration of 0.5 g/ml were resuscitated by further incubation at 22°C for 15 h in the continued presence of amphotericin B. Third, recovery of the ability to replicate was prevented by sequential treatment with 20 g of miconazole per ml, which also increased the fluorescence of mortality-specific dyes to near the maximal levels achieved with 0.9 g of amphotericin B per ml. Sequential treatment with fluconazole and flucytosine did not increase the levels of staining with the mortality-specific dyes. Itraconazole was less effective than ketoconazole, which was less effective than miconazole. The practice of equating the loss of the capacity of C. albicans to form colonies with fungal cell death may give incorrect results in assays with amphotericin B, and the results of assays with caution with other antifungal agents that are lipophilic or that possess significant postantifungal effects may need to be interpreted.Candida is the fourth most common cause of nosocomial bloodstream infections in the United States (10), and the rate of primary bloodstream infections continues to increase (3). The most frequently isolated Candida species in these infections is Candida albicans. Candidemia is also frequently refractory to therapy, and the rate of mortality attributable to candidemia has been estimated to be 38% (36). Despite recent advances in the development of antifungal agents, amphotericin B (AMB) still remains the drug of choice for the treatment of life-threatening systemic infections (14), and the activity of AMB is the standard to which the activities of other antifungal agents are compared. AMB binds with the sterol ergosterol, resulting in the loss of membrane integrity and osmotic stability (5).The process of cell replication deactivation is believed to involve stepwise changes in the physiological state of a cell that render an intermediate form that is incapable of initiating replicative processes but that is still capable of metabolism (21, 27). Thus, the loss of replication competency is an early event in a phase of decline that eventually leads to cell death (19,27).We have previously examined the effects of AMB on the vitality and mortality of C. albicans cell...