The FilmArray platform (FA; BioFire, Salt Lake City, UT) is a closed diagnostic system allowing high-order multiplex PCR analysis with automated readout of results directly from positive blood cultures in 1 h. In the present study, we evaluated the clinical performance of the FilmArray blood culture identification (BCID) panel, which includes 19 bacteria, five yeasts, and three antibiotic resistance genes. In total, 206 blood culture bottles were included in the study. The FilmArray could identify microorganisms in 153/167 (91.6%) samples with monomicrobial growth. Thirteen of the 167 (7.8%) microorganisms were not covered by the FilmArray BCID panel. In 6/167 (3.6%) samples, the FilmArray detected an additional microorganism compared to blood culture. When polymicrobial growth was analyzed, the FilmArray could detect all target microorganisms in 17/24 (71%) samples. Twelve blood culture bottles that yielded a positive signal but showed no growth were also negative by FilmArray. In 3/206 (1.5%) bottles, the FilmArray results were invalid. The results of the FilmArray were reproducible, as demonstrated by the testing and retesting of five bottles in the same day and a longitudinal follow-up of five other blood cultures up to 4 weeks. The present study shows that the FilmArray is a rapid identification method with high performance in direct identification of bacteria and yeasts from positive blood culture bottles.

By combining a newly established single-cell cytotoxicity assay in agarose (16) with estimations of the maximum natural killer (NK) potential (Vmax) by 51Cr release that percentage of target-binding cells (TBC), the fraction of active killers among TBC, the kinetics of single-cell cytotoxicity, and the recycling of effector cells was studied. Using nylon wool-passed peripheral lymphocytes, approximately 10% of the cells will bind to NK- susceptible target cell lines. Most of these have receptors for IgG. Some 50% will go on to kill T cell targets and some 20% to kill the standard target cell K-562. As the individual NK cell is shown to have the capacity to recycle, i.e., to kill more than one target cell in the 3-h test period, and as recycling seems to vary between individuals, there is no consistent correlation between the number of TBC and 51Cr-release values. It seems as if the single-cell cytotoxicity assay, as presently performed in agarose, is a valuable complement to Vmax determinations by 51Cr-release to study the different steps involved in the cytolytic process: recognition, enzyme activation, and effector cell recycling. The discrimination between these steps will probably be necessary to define mechanisms influencing NK cells in different disease states as well as in learning more about the normal function and regulation of the human NK system.

The adhesiveness of 2 unencapsulated nonfimbriated strains of Haemophilus influenzae, 23459 and 23330, and the encapsulated fimbriated strain 770235 to extracellular matrix (ECM) and to its isolated components was studied, as was the potential of H. influenzae plasminogen receptors to enhance degradation of ECM and bacterial penetration through basement membrane. All strains exhibited efficient adhesiveness to reconstituted basement membrane and to ECM from cultured human endothelial cells. Strains 23459 and 23330 efficiently adhered to immobilized laminin, fibronectin, and various collagens. Strain 770235 adhered efficiently to fibronectin and type I and III collagens and with low efficiency to laminin. With all 3 strains, plasmin generated on H. influenzae plasminogen receptors degraded laminin and fibronectin as well as ECM from human endothelial cells. Plasmin bound on H. influenzae cells also potentiated penetration of bacteria through a basement membrane preparation reconstituted on membrane filters. These results give evidence for a role of ECM adherence and plasminogen activation in the spread of H. influenzae through tissue barriers.

180 bacterial strains representing 17 different species of gram positive cocci were tested for the ability to interact with human plasminogen. Receptors for plasminogen could be detected on 23/24 strains of S. pyogenes, 15/15 strains of S. equisimilis, 14/16 strains of human group G streptococci and 14/14 strains of S. pneumoniae. Eight of nineteen strains representing five species of alpha‐hemolytic streptococci were also positive. S. equisimilis demonstrated the highest uptake with a median value of 58 per cent (20%‐67%). On the other hand, all strains of S. agalactiae, the majority of S. faecalis and all S. aureus, S. epidermidis and S. saprophyticus strains tested were negative. The concentration of unlabelled plasminogen causing a 50 per cent reduction of bound tracer was between 50 and 150 nM. These estimates of the dissociation constant confirmed the specific nature of the interaction. Binding of plasminogen could be blocked by addition of plasmin‐aprotinin complex, suggesting that plasminogen and plasmin bind to the same receptor. Binding was also blocked by the plasminogen fragment kringle 1–3, but not by miniplasminogen, a fragment containing kringle 5 and the B‐chain region. As streptokinase interacts mainly with the B‐chain of plasmin it is clear that the bacterial receptor for plasminogen is not identical to streptokinase.