Bloodstream infection is a serious condition associated with significant morbidity and mortality. The outcome of these infections can be positively affected by the early implementation of effective antibiotic therapy based on the identification of the infecting organism and genetic markers associated with antibiotic resistance. In this study, we evaluated the microarray-based Verigene Gram-negative blood culture (BC-GN) assay in the identification of 8 genus or species targets and 6 genetic resistance determinants in positive blood culture broths. A total of 1,847 blood cultures containing Gram-negative organisms were tested using the BC-GN assay. This comprised 729 prospective fresh, 781 prospective or retrospective frozen, and 337 simulated cultures representing 7 types of aerobic culture media. The results were compared to those with standard bacterial culture and biochemical identification with nucleic acid sequence confirmation of the resistance determinants. Among monomicrobial cultures, the positive percent agreement (PPA) of the BC-GN assay with the reference method was as follows; Escherichia coli, 100%; Klebsiella pneumoniae, 92.9%; Klebsiella oxytoca, 95.5%; Enterobacter spp., 99.3%; Pseudomonas aeruginosa, 98.9%; Proteus spp., 100%; Acinetobacter spp., 98.4%; and Citrobacter spp., 100%. All organism identification targets demonstrated >99.5% negative percent agreement (NPA) with the reference method. Of note, 25/26 cultures containing K. pneumoniae that were reported as not detected by the BC-GN assay were subsequently identified as Klebsiella variicola. The PPA for identification of resistance determinants was as follows; bla CTX-M , 98.9%; bla KPC , 100%; bla NDM , 96.2%; bla OXA , 94.3%; bla VIM , 100%; and bla IMP , 100%. All resistance determinant targets demonstrated >99.9% NPA. Among polymicrobial specimens, the BC-GN assay correctly identified at least one organism in 95.4% of the broths and correctly identified all organisms present in 54.5% of the broths. The sample-to-result processing and automated reading of the detection microarray results enables results within 2 h of culture positivity. Bloodstream infection (BSI) is a serious and life-threatening condition that has been associated with 25% to 80% mortality (1, 2). The outcome of BSI can be dependent on host factors, such as underlying comorbidities, and microbiological factors, including the type of infecting organism and its susceptibility to antibiotics. It is estimated that up to 30% of hospital-acquired BSI are attributable to Gram-negative organisms (3). Infections caused by these bacteria, particularly when acquired in the hospital, have been associated with 15% to 29% increased crude mortality rates compared with those of the case controls (4, 5). This is particularly true for infections with multidrug-resistant organisms, including those harboring extended-spectrum ␤-lactamases (ESBLs) or carbapenemases, which have been associated with prolonged hospital stay and increased 30-day mortality (6, 7).Perhaps the most important in...

Nathan Ledeboer and colleagues assess the performance of a diagnostic platform for detecting Gram-positive bacteria in blood cultures, an important step in the diagnosis and treatment of patients with sepsis. Please see later in the article for the Editors' Summary

Cupriavidus pauculus is a water microorganism rarely isolated from clinical specimens. We describe a pseudo-outbreak in which multiple strains that were associated with moistening of culturette swabs with tap water were isolated from a single clinic before collecting the patient specimen. CASE REPORTIn a period of 6 weeks, 27 skin and superficial site swab specimens were submitted from an outpatient clinic to the clinical microbiology laboratory for bacterial culture. The specimens were plated onto blood agar (BA; Becton Dickinson, MD), MacConkey (Becton Dickinson, MD), and chocolate agar (CA; Becton Dickinson, MD) per routine procedure. Eleven of the clinical specimens grew an unusual bacterium. After 24 h, the colonies were smooth, round, and colorless on BA and CA and nonfermentative on MacConkey agar. The cultures were negative for common skin flora, such as coagulase negative Staphylococcus or Corynebacterium spp., and other commonly isolated wound pathogens, such as Staphylococcus aureus or Pseudomonas aeruginosa (6). The organisms were found to be Gram negative and catalase and oxidase positive and were reported as "Pseudomonas-like" nonfermenting bacilli by the MicroScan WalkAway system (Siemens Healthcare Diagnostics, IL).Because of the uncommon nature and the presence of this bacterium in multiple specimens in a short span of time, further investigation was undertaken. All the specimens originated from a single hospital-affiliated outpatient clinic and were submitted by the same physician's office. The swab specimens had been collected with double culturette swabs (BBL CultureSwab; BD Diagnostics, Sparks, MD) from various skin and wound sites from patients with various comorbidities and of different age groups. The clinic was contacted, and unopened culturette swabs of the same lot number were requested to rule out contamination. The uninoculated culturettes plated onto BA, CA, MacConkey, and colistin nalidixic acid (CNA; Remel, KS) plates did not yield any growth, thereby ruling out contamination. The clinic was contacted again for a detailed account of specimen collection methods. Upon further inquiries, it was discovered that the culturette swabs were moistened with tap water before collecting the patient specimen. A tap water sample from the clinic sink was requested and plated onto BA, CA, MacConkey, and CNA plates by using a swab, and it grew a "Pseudomonas-like" nonfermenting bacilli morphologically similar to the patient isolates.A total of six isolates and the water isolate were separately referred to the Ohio Department of Health Laboratory and to the Centers for Disease Control and Prevention (CDC) reference laboratories for further identification. The isolates were identified as Cupriavidus (Ralstonia, Wautersia) pauculus based on morphology and biochemical tests. The following tests were reported positive: oxidase, catalase, citrate, and urea. The following were negative: indole, nitrate, methyl red-VogesProskauer, gelatin, and esculin. There was no acid production from glucose, xylose, ma...