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ABSTRACTSepsis is a major cause of morbidity, mortality, and increased medical expense. Rapid diagnosis improves outcomes and reduces costs. The FilmArray blood culture identification panel (BioFire Diagnostics LLC, Salt Lake City, UT), a highly multiplexed PCR assay, can identify 24 etiologic agents of sepsis (8 Gram-positive, 11 Gram-negative, and 5 yeast species) and three antimicrobial resistance genes (mecA, vanA/B, and blaKPC) from positive blood culture bottles. It provides results in about 1 h with 2 min for assay setup. We present the results of an eight-center trial comparing the sensitivity and specificity of the panel with those of the laboratories' standard phenotypic identification techniques, as well as with molecular methods used to distinguish Acinetobacter baumanniifrom other members of the A. calcoaceticus-A. baumanniicomplex and to detect antimicrobial resistance genes. Testing included 2,207 positive aerobic blood culture samples, 1,568 clinical and 639 seeded. Samples were tested fresh or were frozen for later testing within 8 h after the bottles were flagged as positive by an automated blood culture system. At least one organism was detected by the panel in 1,382 (88.1%) of the positive clinical specimens. The others contained primarily off-panel organisms. The panel reported multiple organisms in 81 (5.86%) positive clinical specimens. The unresolved blood culture identification sensitivity for all target detections exceeded 96%, except for Klebsiella oxytoca(92.2%), which achieved 98.3% sensitivity after resolution of an unavoidable phenotypic error. The sensitivity and specificity for vanA/Band blaKPCwere 100%; those for mecAwere 98.4 and 98.3%, respectively.

ABSTRACTCandidaspecies are common causes of bloodstream infections (BSI), with high mortality. Four species cause >90% of CandidaBSI: C. albicans, C. glabrata, C. parapsilosis, and C. tropicalis. Differentiation of Candidaspp. is important because of differences in virulence and antimicrobial susceptibility. CandidaQuickFISH BC, a multicolor, qualitative nucleic acid hybridization assay for the identification of C. albicans(green fluorescence), C. glabrata(red fluorescence), and C. parapsilosis(yellow fluorescence), was tested on Bactec and BacT/Alert blood culture bottles which signaled positive on automated blood culture devices and were positive for yeast by Gram stain at seven study sites. The results were compared to conventional identification. A total of 419 yeast-positive blood culture bottles were studied, consisting of 258 clinical samples (89 C. glabrata, 79 C. albicans, 23 C. parapsilosis, 18 C. tropicalis, and 49 other species) and 161 contrived samples inoculated with clinical isolates (40 C. glabrata, 46 C. albicans, 36 C. parapsilosis, 19 C. tropicalis, and 20 other species). A total of 415 samples contained a single fungal species, with C. glabrata(n= 129; 30.8%) being the most common isolate, followed by C. albicans(n= 125; 29.8%), C. parapsilosis(n= 59; 14.1%), C. tropicalis(n= 37; 8.8%), and C. krusei(n= 17; 4.1%). The overall agreement (with range for the three major Candidaspecies) between the two methods was 99.3% (98.3 to 100%), with a sensitivity of 99.7% (98.3 to 100%) and a specificity of 98.0% (99.4 to 100%). This study showed that CandidaQuickFISH BC is a rapid and accurate method for identifying C. albicans, C. glabrata, and C. parapsilosis, the three most common Candidaspecies causing BSI, directly from blood culture bottles.

ABSTRACTSepsis caused by Staphylococcus aureusis a major health problem worldwide. Better outcomes are achieved when rapid diagnosis and determination of methicillin susceptibility enable early optimization of antimicrobial therapy. Eight large clinical laboratories, seven from the United States and one from Scotland, evaluated the combination of the StaphylococcusQuickFISH BC and the new mecA XpressFISH assay (both AdvanDx, Woburn, MA, USA) for the detection of methicillin-resistant S. aureusin positive blood cultures. Blood cultures flagged as positive by automated blood culture instruments and demonstrating only Gram-positive cocci in clusters on Gram stain were tested by QuickFISH, a 20-min assay. If only S. aureuswas detected, mecA XpressFISH testing followed. The recovered S. aureusisolates were tested by cefoxitin disk diffusion as the reference method. The QuickFISH assay results were concordant with the routine phenotypic testing methods of the testing laboratories in 1,211/1,221 (99.1%) samples and detected 488/491 S. aureusorganisms (sensitivity, 99.4%; specificity, 99.6%). Approximately 60% of the samples (730) contained coagulase-negative staphylococci or nonstaphylococci as assessed by the QuickFISH assay and were not tested further. The 458 compliant samples positive exclusively for S. aureusby the QuickFISH assay were tested by the mecA XpressFISH assay, which detected 209 of 211 methicillin-resistant S. aureusorganisms (sensitivity, 99.1%; specificity, 99.6%). The mecA XpressFISH assay also showed high reproducibility, with 534/540 tests performed by 6 operators over 5 days achieving reproducible results (98.9% agreement). The combination of the StaphylococcusQuickFISH BC and mecA XpressFISH assays is sensitive, specific, and reproducible for the detection of methicillin-resistant S. aureusand yields complete results in 2 h after the blood culture turns positive.

ABSTRACTTigecycline is one of the few remaining therapeutic options for extensively drug-resistant (XDR) Gram-negative bacilli (GNB). MICs of tigecycline to Acinetobacter baumanniihave been reported to be elevated when determined by the Etest compared to determinations by the broth microdilution (BMD) method. The study aim was to compare the susceptibility of GNB to tigecycline by four different testing methods. GNB were collected from six health care systems (25 hospitals) in southeast Michigan from January 2010 to September 2011. Tigecycline MICs among A. baumannii, carbapenem-resistant Enterobacteriaceae(CRE), extended-spectrum ß-lactamase (ESBL)-producing Enterobacteriaceae, and susceptible Enterobacteriaceaeisolates were determined by Etest, BMD, Vitek-2, and MicroScan. Nonsusceptibility was categorized as a tigecycline MIC of =4 µg/ml for both A. baumanniiand Enterobacteriaceae. The study included 4,427 isolates: 2,065 ESBL-producing Enterobacteriaceae, 1,105 A. baumannii, 888 susceptible Enterobacteriaceae, and 369 CRE isolates. Tigecycline nonsusceptibility among A. baumanniiisolates was significantly more common as determined by Etest compared to that determined by BMD (odds ratio [OR], 10.3; P< 0.001), MicroScan (OR, 12.4; P< 0.001), or Vitek-2 (OR, 9.4; P< 0.001). These differences were not evident with the other pathogens. Tigecycline MICs varied greatly according to the in vitrotesting methods among A. baumanniiisolates. Etest should probably not be used by laboratories for tigecycline MIC testing of A. baumanniiisolates, since MICs are significantly elevated with Etest compared to those determined by the three other methods.

ABSTRACTWhen 13 of 13 nasal wash specimens from a single pediatrician's office tested positive for low quantities of Bordetella pertussisDNA, we suspected prelaboratory contamination. Investigation revealed that Pentacel and Adacel vaccines contain high copy numbers of B. pertussisDNA, which can be aerosolized, causing false-positive B. pertussisPCR results.

Clostridioides difficileis the leading cause of diarrhea in hospitalized U.S. patients and results in over 400,000 cases of C. difficileinfection per year. C. difficileinfections have mortality rates of 6 to 30% and significantly increase health care costs, because of increased length of stay and increased frequency of readmissions due to recurrences. Efforts to reduce the spread of C. difficilein hospitals have led to the development of rapid sensitive diagnostic methods.