Sepsis is among the top 10 causes of mortality in the United States. Rapid administration of antibiotics is one of the most important contributors to patient survival, yet only a limited number of methods exist for rapid identification of microbes cultivated from bloodstream infections, which can lead to sepsis. While traditional single-target molecular methods have been shown to greatly improve survival for septic patients by enabling rapid deescalation of broad-spectrum antibiotics, multiplex methods offer even greater possibilities. A novel multiplex method, PCR coupled to electrospray ionization mass spectrometry (PCR/ESI-MS), was used to identify the genus and species of microorganisms found to cause human bloodstream infections. DNA was directly extracted from 234 BacT-Alert blood culture bottles, and results were compared to those obtained by clinical reference standard methods. The study results demonstrated 98.7% and 96.6% concordance at the genus and species levels, respectively. Mixtures of microbes were identified in 29 blood culture bottles, including mixed species of the same genus, as well as mixtures containing Gram-positive and Gram-negative organisms, exemplifying the PCR/ESI-MS capability to identify multiple organisms simultaneously without the need for cultivation. This study demonstrates high analytical accuracy in comparison to routine subculture of blood culture bottles and phenotypic identification of microbes. Without foreknowledge of the microorganisms potentially present, the PCR/ESI-MS methods can deliver accurate results in as little as 5 to 6 h after a positive alarm from the automated blood culture system; however, current batch mode testing limits the method's clinical utility at this time.The ability to rapidly identify the causative agent of bloodstream infections (BSIs) is of paramount importance to clinical microbiology laboratories. Rapid identification significantly reduces the rates of patient mortality, reduces the use of unnecessary antibiotics, and lowers costs to the hospital (6,7,15). If untreated, BSIs can lead to sepsis or progress to severe sepsis, with one or more organ dysfunctions, which can ultimately result in septic shock and/or death.Death due to septic shock is currently the 10th leading cause of mortality in the United States (28). More notably, the rate of sepsis-related death is on the rise. In 2000, sepsis was ranked as the 13th leading cause of death (5), symbolizing a 139% increase in incidence over a 10-year period (8). It is estimated that approximately 215,000 deaths per year are sepsis related, and the costs associated with sepsis are exceedingly high, approximately $17 billion each year and rising, due to the length of hospital stay required (1).It is estimated that the survival increases by 7 to 10% for every hour of earlier administration of targeted antibiotics (34). Ideally, bacteria in the bloodstream should be identified as quickly as possible in order to administer the most appropriate antibiotics, as opposed to use of broad-spectrum antib...

Antistaphylococcal penicillins and cefazolin remain the primary treatments for infections with methicillin-susceptible Staphylococcus aureus (MSSA). The cefazolin inoculum effect (CzIE) causes the cefazolin MIC to be elevated in proportion to the number of bacteria in the inoculum.

Phenotypic antimicrobial susceptibilities are particularly valuable for P. aeruginosa due to the complexity of resistance mechanisms this organism can harbor.…

BackgroundThe Clinical and Laboratory Standards Institute (CLSI) updated fluoroquinolone breakpoints in 2019 in response to evolving resistance and new outcome data. The performance of updated antimicrobial susceptibility testing (AST) algorithms for ciprofloxacin with the 2019 breakpoints for Enterobacteriaceae and Pseudomonas aeruginosa was evaluated using the Accelerate Pheno™ system with contrived positive blood culture samples compared with broth microdilution (BMD).MethodsA total of 294 clinical isolates (100 P. aeruginosa, 82 Klebsiella spp., 56 E. coli, 24 Citrobacter spp., 14 Enterobacter spp., 15 Proteus spp., and 3 S. marcescens) were tested with ciprofloxacin. Aliquots of BD BACTEC™ Standard Aerobic media containing healthy donor blood were seeded with 10–100 bacterial cells and incubated until positivity. Aliquots of the positive blood cultures were run using the Accelerate PhenoTest™ BC kit on the Accelerate Pheno™ system according to the manufacturer instructions for use. Results were obtained using an updated ciprofloxacin algorithm and compared with CLSI standard reference BMD. Only samples with valid results with both the Accelerate Pheno™ system and reference BMD were included in analysis. Essential agreement (EA), categorical agreement (CA), very major error (VME), major error (ME) and minor error (mE) rates were calculated using 2019 CLSI breakpoints.ResultsEA and CA for all antimicrobial/organism combinations were >94%. There were 2 MEs (1 K. pneumoniae, 1 C. freundii) and no VMEs.ConclusionResults with the new research use only (RUO) algorithms are very good and meet FDA acceptance criteria for AST performance. These data will be submitted to the FDA for clearance, once FDA recognizes the CLSI breakpoints. Disclosures All authors: No reported disclosures.