Clinical Blood Culture Samples Research Articles

Comparison of a Sepsityper® kit and in-house membrane filtration methods for rapidly diagnosing positive blood cultures via MALDI‒TOF MS

BackgroundRapidly identifying pathogens and determining their antimicrobial susceptibilities using samples directly from flagged blood culture bottles pose significant challenges for clinical laboratories. Thus, a cost-effective and efficient sample-processing method is urgently needed to address this issue. To fulfill this need, we developed a novel protocol to rapidly identify pathogens and determine their antimicrobial susceptibilities using samples directly from blood culture bottles. MethodsSamples were either processed by the Sepsityper kit or our in-house methods. In our approach, we processed the samples using either a nonionic surfactant (Triton X-100) or a NaOH-sodium dodecyl sulfate (SDS) solution, followed by membrane filtration (MF) and centrifugation. Subsequently, the samples were analyzed using MALDI-TOF mass spectrometry (MS) for identification and the Vitek® 2 for antimicrobial susceptibility determination. ResultsIn this study, 122 clinical blood culture samples were analyzed, and our MF protocol displayed enhanced accuracy in identifying gram-positive organisms (n = 58) and gram-negative bacilli (n = 64) compared to the Sepsityper method. In particular, the Triton-MF and SDS-MF techniques outperformed Sepsityper in identifying gram-negative bacilli, with accuracy rates of 92.2 %, 85.9 %, and 78.1 %, respectively. Notably, both the Triton-MF and SDS-MF methods exhibited high categorical agreement (CA) for antimicrobial susceptibility testing (AST) for carbapenem against Enterobacterales, with CAs of 100 % and 98.7 %, respectively. Additionally, both methods exhibited a perfect CA and essential agreement of 100 % for Enterococcus faecium AST for vancomycin. ConclusionThese findings strongly indicate that our MF methods have the potential to streamline the identification and AST of bacteria in positive blood cultures.

Evaluation of a nucleic acid amplification system, GENECUBE, for rapid detection of staphylococcal nuc and mecA in blood culture samples

ObjectiveThis study determined whether the GENECUBE rapid nucleic acid amplification test could directly detect nuc and mecA genes in clinical blood culture samples of Staphylococcus and various other pathogens. MethodsBetween September 2020 and December 2021, 537 blood culture samples from 192 patients with suspected bacteremia were tested using conventional assays (MicroScan WalkAway96 or VITEK 2 systems) and GENECUBE nuc and mecA assays. Isolates from samples with discrepant results between the conventional and GENECUBE assays were further evaluated using MALDI-TOF mass spectrometry, disk diffusion testing using cefoxitin, broth microdilution testing using oxacillin, and sequencing for mecA. Bacterial solutions containing a mixture of methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus epidermidis (MRSE) were prepared to evaluate the limit of detection (LOD) of mecA. ResultsUsing conventional assays as the reference, the sensitivity, specificity, and positive and negative predictive values (95 % confidence interval) of GENECUBE were 100 % (96.8–100 %), 100 % (99.1–100 %), 100 % (96.8–100 %), and 100 % (99.1–100 %), respectively, for nuc detection and 100 % (96.1–100 %), 98.9 % (97.4–99.6 %), 94.9 % (88.5–98.3 %), and 100 % (99.2–100 %), respectively, for mecA detection. Sequencing analysis of five samples identified as methicillin-sensitive staphylococci using conventional assays and methicillin-resistant staphylococci using GENECUBE revealed the presence of methicillin-resistant isolates in all samples. The estimated LOD of mecA was 104 colony-forming units (CFU)/mL of MRSE with GENECUBE, compared with 105 CFU/mL with conventional assays. ConclusionThe GENECUBE assay accurately detected mecA in positive blood culture samples and had higher sensitivity than conventional assays.

Evaluation of the Speed, Accuracy and Precision of the QuickMIC Rapid Antibiotic Susceptibility Testing Assay With Gram-Negative Bacteria in a Clinical Setting.

The rapidly changing landscape of antimicrobial resistance poses a challenge for empirical antibiotic therapy in severely ill patients and highlights the need for fast antibiotic susceptibility diagnostics to guide treatment. Traditional methods for antibiotic susceptibility testing (AST) of bacteria such as broth microdilution (BMD) or the disc diffusion method (DDM) are comparatively slow and show high variability. Rapid AST methods under development often trade speed for resolution, sometimes only measuring responses at a single antibiotic concentration. QuickMIC is a recently developed lab-on-a-chip system for rapid AST. Here we evaluate the performance of the QuickMIC method with regard to speed, precision and accuracy in comparison to traditional diagnostic methods. 151 blood cultures of clinical Gram-negative isolates with a high frequency of drug resistance were tested using the QuickMIC system and compared with BMD for 12 antibiotics. To investigate sample turnaround time and method functionality in a clinical setting, another 41 clinical blood culture samples were acquired from the Uppsala University Hospital and analyzed on site in the clinical laboratory with the QuickMIC system, and compared with DDM for 8 antibiotics routinely used in the clinical laboratory. The overall essential agreement between MIC values obtained by QuickMIC and BMD was 83.4%, with an average time to result of 3 h 2 min (SD: 24.8 min) for the QuickMIC method. For the clinical dataset, the categorical agreement between QuickMIC and DDM was 96.8%, whereas essential and categorical agreement against BMD was 91.0% and 96.7%, respectively, and the total turnaround time as compared to routine diagnostics was shown to be reduced by 40% (33 h vs. 55 h). Interexperiment variability was low (average SD: 44.6% from target MIC) compared to the acceptable standard of ±1 log2 unit (i.e. -50% to +100% deviation from target MIC) in BMD. We conclude that the QuickMIC method can provide rapid and accurate AST, and may be especially valuable in settings with high resistance rates, and for antibiotics where wildtype and antibiotic-resistant bacteria have MIC distributions that are close or overlapping.

Performance of dRAST on Prospective Clinical Blood Culture Samples in a Simulated Clinical Setting and on Multidrug-Resistant Bacteria.

ABSTRACTThere is an utmost need for rapid antimicrobial susceptibility testing (AST) of bacteria causing bloodstream infections (BSI). The dRAST (QuantaMatrix Inc., Seoul) is a commercial method that can be performed directly from positive blood cultures. The present study aims to evaluate the performance of the dRAST on prospective clinical blood culture samples. A sample prescreening algorithm based on clinical routine was used to choose relevant clinical positive blood culture samples for testing on the dRAST. Rapid identification via short-term culture followed by matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) was used during the test run, and dRAST results were compared to European Committee on Antimicrobial Susceptibility Testing (EUCAST) disk diffusion as the reference method. The performance of the dRAST was also evaluated on selected multidrug resistant (MDR) isolates in simulated blood cultures. Using the sample pre-screening algorithm, 242 clinical blood culture samples were selected and tested on the dRAST, of which 200 (82.6%) gave valid AST tests results comprising 76 Gram-positive and 124 Gram-negative samples. AST measurements from the dRAST and disk diffusion from clinical samples had an overall agreement rate of 95.5%. When using simulated blood culture samples of 31 selected MDR isolates, the agreement between dRAST and disk diffusion was 87.2%. While the agreement rates were high, it was noted that the dRAST was not reliable for AST of certain antibiotic–bacteria combinations. In conclusion, the present study demonstrates that dRAST delivers rapid AST results from blood cultures and using a prescreening algorithm for sample selection is important in implementation of modern AST methods such as dRAST.IMPORTANCE There is an utmost need for rapid antimicrobial susceptibility testing (AST) of bacteria causing bloodstream infections (BSI). The dRAST (QuantaMatrix Inc., Seoul) is a rapid AST method that can be performed directly from positive blood cultures. The dRAST gives results in 6 h compared to conventional AST methods that needs 18-20 h of incubation. The present study aims to evaluate the performance of the dRAST in a clinical setting with the use of a sample selection algorithm to reduce incompatible sample numbers. The study found that while the agreement rates between dRAST and reference AST methods were high, it was noted that the dRAST was not reliable for AST of certain antibiotic–bacteria combinations. In conclusion, the present study demonstrates that dRAST delivers rapid AST results from blood cultures and using a prescreening algorithm for sample selection is important in implementation of modern AST methods such as dRAST.

Rapid molecular detection of pathogenic microorganisms and antimicrobial resistance markers in blood cultures: evaluation and utility of the next-generation FilmArray Blood Culture Identification 2 panel

Rapid detection of pathogens causing bloodstream infections (BSI) directly from positive blood cultures is of highest importance in order to enable an adequate and timely antimicrobial therapy. In this study, the utility and performance of a recently launched next-generation fully automated test system, the Biofire FilmArray® Blood Culture Identification 2 (BCID2) panel, was evaluated using a set of 103 well-characterized microbial isolates including 29 antimicrobial resistance genes and 80 signal-positive and 23 signal-negative clinical blood culture samples. The results were compared to culture-based reference methods, MALDI-TOF, and/or 16S rDNA sequencing. Of the clinical blood culture samples, 68 were monomicrobial (85.0%) and 12 polymicrobial (15.0%). Six samples contained ESBL (blaCTX-M), two MRSA (mecA), and three MRSE (mecA) isolates. In overall, the FilmArray BCID2 panel detected well on-panel targets and resistance markers from mono- and polymicrobial samples. However, one Klebsiella aerogenes and one Bacteroides ovatus were undetected, and the assay falsely reported one Shigella flexneri as Escherichia coli. Hence, the sensitivity and specificity for detecting microbial species were 98.8% (95%CI, 95.8–99.9%) and 99.9% (95%CI, 99.8–99.9%), respectively. The sensitivity and specificity for detecting of resistance gene markers were 100%. The results were available within 70 min from signal-positive blood cultures with minimal hands-on time. In conclusion, the BCID2 test allows reliable and simplified detection of a vast variety of clinically relevant microbes causing BSI and the most common antimicrobial resistance markers present among these isolates.

649. Clinical Implementation of a Rapid Susceptibility Testing Procedure, Directly From a Positive Blood Culture Using the Vitek®2 System on Gram Negative Rods

BackgroundThe national average of identification and susceptibility for organisms isolated from positive blood culture to final susceptibility based on growth on solid media is 48 hours. The goal of this research was to prove that the Vitek®2 (bioMérieux, Inc.) system can provide an accurate and reliable susceptibility result directly from positive blood culture for Gram negative rods and reduce the turnaround time (TAT) from positive blood culture to the final susceptibility.MethodsAn FDA-modified validation procedure was performed on positive blood cultures directly from the bottle to the VITEK®2 System for susceptibility testing. The protocol tested and validated an aliquot of 50uL of blood directly from the positive bottle into 10 mL of saline (1:200). The solution was vortexed and 3mL were placed in the VITEK®2 test tube. This protocol was intended only for Gram negative rods using the AST-GN70, AST-GN81 & AST-GN801 cards. This protocol followed the CLSI M52 and M100 guidelines.Results515 organisms from clinical blood culture samples from July 2018 to October 2019 were evaluated. Organisms included, but were not limited to: E. coli, K. pneumoniae, Enterobacter spp., and P. aeruginosa, Proteus spp., Salmonella spp., Acinetobacter spp., and S. maltophilia. There were 5,201 drug/bug combinations. AdventHealth Orlando achieved an essential agreement of 99.32% (n=5,166), minor error 0.74% (n=39) major error 0.02% (n=1) and very major error 0.49% (n=2). A 100% agreement was achieved on detection of ESBL, CRE, and MDR organisms.ConclusionRapid direct blood culture protocol using the VITEK®2 System and the AST-GN cards is accurate, reliable and can be performed with less than 1 minute hands-on time. The protocol can be implemented in any laboratory at no additional costs or modification where the current VITEK®2 AST-GN panels are in use. This protocol was clinically implemented at AdventHealth Orlando on July 15, 2019. Compared with the national average of 72 hours, the TAT obtained during this study was 23 hours from positive blood culture to final susceptibility, a significant reduction of 25 hours. The authors encourage bioMérieux Inc. to evaluate and explore the opportunity to expand the use of the VITEK®2 system for this application with the appropriate clinical trial.Disclosures All Authors: No reported disclosures

The smart activatable P2&3TT probe allows accurate, fast, and highly sensitive detection of Staphylococcus aureus in clinical blood culture samples

Staphylococcus aureus bacteraemia (SAB) is associated with high mortality and morbidity rates. Yet, there is currently no adequate diagnostic test for early and rapid diagnosis of SAB. Therefore, this study was aimed at exploring the potential for clinical implementation of a nuclease-activatable fluorescent probe for early diagnosis of SAB. To this end, clinical blood culture samples from patients with bloodstream infections were incubated for 1 h with the “smart” activatable P2&3TT probe, the total assay time being less than 2 h. Cleavage of this probe by the secreted S. aureus enzyme micrococcal nuclease results in emission of a readily detectable fluorescence signal. Incubation of S. aureus-positive blood culture samples with the P2&3TT probe resulted in 50-fold higher fluorescence intensity levels than incubation with culture-negative samples. Moreover, incubation of the probe with non-S. aureus-positive blood cultures yielded essentially background fluorescence intensity levels for cultures with Gram-negative bacteria, and only ~ 3.5-fold increased fluorescence intensity levels over background for cultures with non-S. aureus Gram-positive bacteria. Importantly, the measured fluorescence intensities were dose-dependent, and a positive signal was clearly detectable for S. aureus-positive blood cultures with bacterial loads as low as ~ 7,000 colony-forming units/mL. Thus, the nuclease-activatable P2&3TT probe distinguishes clinical S. aureus-positive blood cultures from non-S. aureus-positive blood cultures and culture-negative blood, accurately, rapidly and with high sensitivity. We conclude that this probe may enhance the diagnosis of SAB.

Rapid antibiotic susceptibility testing of bacteria from patients\u2019 blood via assaying bacterial metabolic response with surface-enhanced Raman spectroscopy

Blood stream infection is one of the major public health issues characterized with high cost and high mortality. Timely effective antibiotics usage to control infection is crucial for patients’ survival. The standard microbiological diagnosis of infection however can last days. The delay in accurate antibiotic therapy would lead to not only poor clinical outcomes, but also to a rise in antibiotic resistance due to widespread use of empirical broad-spectrum antibiotics. An important measure to tackle this problem is fast determination of bacterial antibiotic susceptibility to optimize antibiotic treatment. We show that a protocol based on surface-enhanced Raman spectroscopy can obtain consistent antibiotic susceptibility test results from clinical blood-culture samples within four hours. The characteristic spectral signatures of the obtained spectra of Staphylococcus aureus and Escherichia coli—prototypic Gram-positive and Gram-negative bacteria—became prominent after an effective pretreatment procedure removed strong interferences from blood constituents. Using them as the biomarkers of bacterial metabolic responses to antibiotics, the protocol reported the susceptibility profiles of tested drugs against these two bacteria acquired from patients’ blood with high specificity, sensitivity and speed.

Simultaneous and high sensitive detection of Salmonella typhi and Salmonella paratyphi a in human clinical blood samples using an affordable and portable device

Enteric fever is one of the leading causes of infection and subsequent fatality (greater than 1.8 million) (WHO 2018), especially in the developing countries due to contaminated water and food inter twinned with unhygienic practices. Clinical gold standard technique of culture-based method followed by biochemical tests demand 72+ hours for diagnosis while newly developed techniques (like PCR, RT-PCR, DNA microarray etc.) suffer from high limit of detection or involve high-cost infrastructure or both. In this work, a quick and highly specific method, SMOL was established for simultaneous detection of Salmonella paratyphi A and Salmonella typhi in clinical blood samples. SMOL consists of (i) pre-concentration of S. typhi and S. paratyphi A cells using magnetic nanoparticles followed by (ii) cell lysis and DNA extraction (iii) amplification of select nucleic acids by LAMP technique and (iv) detection of amplified nucleic acids using an affordable portable device (costs less than $70). To identify the viability of target cells at lower concentrations, the samples were processed at two different time periods of t = 0 and t = 4h. Primers specific for the SPA2539 gene in S. paratyphi A and STY2879 gene in S. typhi were used for LAMP. Within 6h SMOL was able to detect positive and negative samples from 55 human clinical blood culture samples and detect the viability of the cells. The results were concordant with culture and biochemical tests as well as by qPCR. Statistical power analysis yielded 100%. SMOL results were concordant with culture and biochemical tests as well as by qPCR. The sensitive and affordable system SMOL will be effective for poor resource settings.

Identification and antimicrobial susceptibility testing of Gram-positive and Gram-negative bacteria from positive blood cultures using the Accelerate Pheno\u2122 system

Rapid identification and antimicrobial susceptibility testing remain a crucial step for early efficient therapy of bloodstream infections. Traditional methods require turnaround times of at least 2 days, while rapid procedures are often associated with extended hands-on time. The Accelerate Pheno™ System provides microbial identification results within 90 min and susceptibility data in approximately 7 h directly from positive blood cultures with only few minutes of hands-on time. The aim of this study was, therefore, to evaluate the performance of the Accelerate Pheno™ System in identification and antimicrobial susceptibility testing of both Gram-positive and Gram-negative bacteria directly from clinical blood culture samples. We analyzed 108 and 67 blood culture bottles using the Accelerate PhenoTest™ BC kit with software version v1.0 and the FDA-cleared version v1.2, respectively. Reliable identification was achieved for Enterobacteriaceae, staphylococci, and enterococci, with 76/80 (95%), 42/46 (91%), and 10/11 (91%) correct identifications. Limitations were observed in the identification of streptococci, including Streptococcus pneumoniae and Streptococcus pyogenes, and coagulase-negative staphylococci. Antimicrobial susceptibility results for Enterobacteriaceae, for amikacin, ertapenem, ciprofloxacin, gentamicin, meropenem, and piperacillin-tazobactam ranged between 86 and 100% categorical agreement. Using v1.2, results for ceftazidime showed 100% concordance with the reference method. For staphylococci, the overall performance reached 92% using v1.2. Qualitative tests for detection of methicillin or macrolide-lincosamide-streptogramin B (MLSB) resistance caused major and very major errors for isolates. Overall, the present data show that the Accelerate Pheno™ system can, in combination with Gram stain, be used as a rapid complementation to standard microbial diagnosis of bloodstream infections.

An Improved In-house MALDI-TOF MS Protocol for Direct Cost-Effective Identification of Pathogens from Blood Cultures.

Background: Bloodstream infection is a major cause of morbidity and mortality in hospitalized patients worldwide. Delays in the identification of microorganisms often leads to a poor prognosis. The application of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) directly to blood culture (BC) broth can potentially identify bloodstream infections earlier, and facilitate timely management.Methods: We developed an “in-house” (IH) protocol for direct MALDI-TOF MS based identification of organisms in positive BCs. The IH protocol was initially evaluated and improved with spiked BC samples, and its performance was compared with the commercial Sepsityper™ kit using both traditional and modified cut-off values. We then studied in parallel the performance of the IH protocol and the colony MS identifications in positive clinical BC samples using only modified cut-off values. All discrepancies were investigated by “gold standard” of gene sequencing.Results: In 54 spiked BC samples, the IH method showed comparable results with Sepsityper™ after applying modified cut-off values. Specifically, accurate species and genus level identification was achieved in 88.7 and 3.9% of all the clinical monomicrobial BCs (284/301, 94.4%), respectively. The IH protocol exhibited superior performance for Gram negative bacteria than for Gram positive bacteria (92.8 vs. 82.4%). For anaerobes and yeasts, accurate species identification was achieved in 80.0 and 90.0% of the cases, respectively. For polymicrobial cultures (17/301, 5.6%), MALDI-TOF MS correctly identified a single species present in all the polymicrobial BCs under the Standard mode, while using the MIXED method, two species were correctly identified in 52.9% of the samples. Comparisons based on BC bottle type, showed that the BACTEC™ Lytic/10 Anaerobic/F culture vials performed the best.Conclusion: Our study provides a novel and effective sample preparation method for MALDI-TOF MS direct identification of pathogens from positive BC vials, with a lower cost ($1.5 vs. $ 7) albeit a slightly more laborious extracting process (an extra 15 min) compared with Sepsityper™ kit.

Comparison of ‘time to detection’ values between BacT/ALERT VIRTUO and BacT/ALERT 3D instruments for clinical blood culture samples

ObjectivesThe early detection of bacteraemia and fungemia is of paramount importance to guide antimicrobial therapy in septic patients. In this study the ‘time to detection’ (TTD) value for the new blood culture system BacT/ALERT VIRTUO (VIRTUO) was evaluated in 1462 positive clinical bottles and compared with the TTD for 1601 positive clinical bottles incubated in the BacT/ALERT 3D system (BTA-3D). MethodsThe most representative microorganisms isolated from bottles incubated in both blood culture systems were divided into eight categories (in order of frequency): coagulase-negative staphylococci (CoNS), Escherichia coli, Enterobacteriaceae (other than E. coli), Staphylococcus aureus, Enterococcus spp, viridans group streptococci, Pseudomonas aeruginosa, and Candida spp. ResultsThe comparison of TTD values for the two blood culture systems strongly indicated that growth of the first five groups listed above was detected earlier with VIRTUO than with BTA-3D (p < 0.05). ConclusionsThe new VIRTUO blood culture system can reduce the TTD for more than 75% of isolated microorganisms.

Usefulness of Multiplex Real-Time PCR for Simultaneous Pathogen Detection and Resistance Profiling of Staphylococcal Bacteremia.

Staphylococci are the leading cause of nosocomial blood stream infections. Fast and accurate identification of staphylococci and confirmation of their methicillin resistance are crucial for immediate treatment with effective antibiotics. A multiplex real-time PCR assay that targets mecA, femA specific for S. aureus, femA specific for S. epidermidis, 16S rRNA for universal bacteria, and 16S rRNA specific for staphylococci was developed and evaluated with 290 clinical blood culture samples containing Gram-positive cocci in clusters (GPCC). For the 262 blood cultures identified to the species level with the MicroScan WalkAway system (Siemens Healthcare Diagnostics, USA), the direct real-time PCR assay of positive blood cultures showed very good agreement for the categorization of staphylococci into methicillin-resistant S. aureus (MRSA), methicillin-susceptible S. aureus (MSSA), methicillin-resistant S. epidermidis (MRSE), methicillin-susceptible S. epidermidis (MSSE), methicillin-resistant non-S. epidermidis CoNS (MRCoNS), and methicillin-susceptible non-S. epidermidis CoNS (MSCoNS) (κ = 0.9313). The direct multiplex real-time PCR assay of positive blood cultures containing GPCC can provide essential information at the critical point of infection with a turnaround time of no more than 4 h. Further studies should evaluate the clinical outcome of using this rapid real-time PCR assay in glycopeptide antibiotic therapy in clinical settings.

Measurement of Microbial DNA Polymerase Activity Enables Detection and Growth Monitoring of Microbes from Clinical Blood Cultures

Surveillance of bloodstream infections (BSI) is a high priority within the hospital setting. Broth-based blood cultures are the current gold standard for detecting BSI, however they can require lengthy incubation periods prior to detection of positive samples. We set out to demonstrate the feasibility of using enzymatic template generation and amplification (ETGA)-mediated measurement of DNA polymerase activity to detect microbes from clinical blood cultures. In addition to routine-collected hospital blood cultures, one parallel aerobic blood culture was collected and immediately refrigerated until being transported for ETGA analysis. After refrigeration holding and transport, parallel-collected cultures were placed into a BACTEC incubator and ETGA time-course analysis was performed. Of the 308 clinical blood cultures received, 22 were BACTEC positive, and thus were initially selected for ETGA time course analysis. The ETGA assay detected microbial growth in all 22 parallel-positive blood cultures in less time than a BACTEC incubator and also yielded genomic DNA for qPCR-based organism identification. In summary, feasibility of detecting microbes from clinical blood culture samples using the ETGA blood culture assay was demonstrated. Additional studies are being considered towards development of clinically beneficial versions of this methodology.

Evaluation of the BinaxNOW PBP2a assay for the direct detection of methicillin resistance in Staphylococcus aureus from positive blood culture bottles

BinaxNOW® PBP2a rapid immunochromatographic assay is a novel test for the identification of methicillin resistance in Staphylococcus aureus from clinical blood culture samples based on detection of penicillin binding protein 2a. We have evaluated the utility of this assay to do a rapid diagnostic of methicillin susceptibility directly from blood culture bottles after identification of S. aureus in positive bottles by matrix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF) mass spectrometry. Twenty of 21 methicillin-resistant S. aureus (MRSA) samples from blood cultures were positive on direct immunochromatographic testing (sensitivity 95.24%, 95% confidence interval [CI] 74.13% to 99.75%), whereas 37 methicillin-susceptible S. aureus (MSSA) samples were negative (specificity 100%, 95% CI 88.99% to 99.75%). The combined use of MALDI-TOF mass spectrometry and BinaxNOW® PBP2a test is useful for the rapid identification of both MRSA and MSSA from blood cultures.

Direct detection of methicillin-resistant Staphylococcus aureus from blood cultures using an immunochromatographic immunoassay-based MRSA rapid kit for the detection of penicillin-binding protein 2a

Using an EZ-Step MRSA rapid kit, a novel screening test for methicillin-resistant Staphylococcus aureus (MRSA) that detects penicillin-binding protein 2a, 34 of 36 MRSA-positive clinical blood culture samples were positive on direct testing (sensitivity, 94.4%), whereas 21 of 21 methicillin-susceptible S. aureus-positive samples were negative (specificity, 100%).