SUMMARYAttachment and neuritic transport of herpes simplex virus (HSV) type 1 (McIntyre) were studied in a cell culture system with dissociated cells of rat dorsal root ganglia. The two-chamber cell culture system containing a diffusion barrier penetrated by neurites of cultured sensory neurons permitted infection of neurites extending outside the diffusion barrier without exposure of the neuronal cell soma. HSV adsorbed to neuritic extensions and reached the neuronal soma within 1.5 h post-inoculation. Neuritic uptake and transport of HSV were inhibited in the presence of cytochalasin B. Internalization of virus in neurites was preceded by attachment of virus to the neurite plasma membrane. Neurites transported viral nucleocapsids (NC) through the diffusion barrier of the cultures. Destruction of the neuritic extensions before or shortly after peripheral virus inoculation blocked spread of infection to the cell soma. No infection was established when neuritic extensions were exposed to viral NC and NC were then not observed inside the neurite plasma membrane. Virus produced in neurons, when HSV was inoculated into the inner culture chamber containing the neuronal cell bodies, was transported as enveloped virus in cytoplasmic vesicles from the neuronal cell body towards the periphery. Schwann cells were infected by viropexis. Shortly after infection virions were observed in vacuoles of the cytoplasm.

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A 20-ml blood sample was collected from adult patients with suspected bloodstream infections and distributed equally into the four volume-controlled bottles of a blood culture set consisting of aerobic and anaerobic BACTEC Plus/F bottles and aerobic and anaerobic BacT/Alert FAN bottles. All bottles were incubated in their respective instruments for a standard 5-day protocol or until the instruments signalled positivity. Samples in all bottles with negative results by these instruments were terminally subcultured. A total of 8,390 blood culture sets were obtained during the study period, of which 4,402 (52.5%) met the study criteria. Of these, 946 (21.5%) were positive either by instrument signal or by additional terminal subculture of all negative bottles and yielded growth of microorganisms. Five hundred eighty-nine (13.4%) blood culture sets were considered to have recovered 663 clinically significant organisms. When both the BACTEC and the BacT/Alert systems were used, 465 positive sets were detected; BACTEC alone detected 52 positive sets and BacT/Alert alone detected 72 (P = 0.09). No differences were found between the two systems in microbial recovery rate from blood cultures obtained from patients on antibiotic therapy. Significantly more members of the family Enterobacteriaceae (P < 0.01) were detected from patients without antimicrobial therapy by BacT/Alert than by BACTEC. The false-negative rates were 0.20% for BACTEC and 0.32% for BacT/Alert. A significantly higher false-positive rate was found for BACTEC (P < 0.0001). Both systems were comparable for the time to detection of microorganisms. However, gram-positive bacteria were detected faster by BACTEC andEnterobacteriaceae were detected faster on average by BacT/Alert. We concluded that both systems are comparable in their abilities to recover aerobic and anaerobic organisms from blood cultures and a terminal subculture might not be necessary for either of the two systems. The increased positivity rate when using an anaerobic bottle in a two-bottle blood culture set is due to the additional blood volume rather than to the use of an anaerobic medium.

Continuous cellular incorporation of choline molecules is essential for DNA binding to competent pneumococci. The choline molecules are incorporated into the cell surface at the equatorial region of the cocci. As a working hypothesis, it is proposed that DNA molecules enter these bacteria at the growing zone(s) of the cell envelope.The presence of choline residues in the teichoic acid portion of the pneumococcal cell envelope (1) is essential for several physiological functions of this bacterium. Not only is choline required for growth (2), but biosynthetic replacement of choline in the cell surface by structural analogs (such as ethanolamine) causes several striking physiological changes in the bacteria (2-5); one such change is a defect in cell division that prevents the physical separation of daughter cells from one another. The incorporation of new choline molecules into the cell surface takes place at a distinct growing zone, localized at the equatorial region of pneumococci (6). We now describe evidence which suggests that the cell-surface changes that make pneumococci capable of absorbing and integrating extracellular DNA are in some way coupled to the functioning of the growing zone of the cell envelope. MATERIALS AND METHODSCultures of the R36A strain of Diplococcus pneumoniae were used in all experiments at a concentration of 107-108 cells/ml. The composition of a chemically defined (Cd) (7) and a semisynthetic (C) (8) medium was described earlier. An enriched defined medium (Cden) was prepared by supplementing Cd medium with all the amino acids present in acid-hydrolyzed casein, at the same concentrations as in the C medium. "Choline-phase" and "ethanolamine-phase" bacteria were grown in Cden medium supplemented with 5 MLg/ml of choline or 40 Mg/ml of ethanolamine, respectively. Bacterial growth was monitored with a Coleman nephelometer. Cells were transferred from one medium to another by filtration (Millipore filters, pore size 0.45 Mm). Radioactive tracers were used at 5 Mg/ml and 1 MCi/ml concentrations, unless otherwise noted. The incorporation of radioactive tracers into cold trichloroacetic acid (TCA)-insoluble material was measured by collecting the samples on glass-fiber disks (Schleicher and Schuell); after drying, the disks were counted in a toluene-based scintillator in a scintillation spectrometer (Unilux, Nuclear-Chicago). The preparation and assay of competence factor (CF) (9) and transforming DNA (10), determination of CF-receptor activity (11), and the tests for the competence-specific agglutinin (12) were all performed by published procedures. The concentration of CF during the "activation" assay was usually 100-500 Units (13) per ml. Lysis sensitivity of pneumococci was determined as follows: 0.9 ml of the culture was pipetted into tubes prepared with 0.1 ml of phosphate buffer (1 M, pH 8) and 50 Ml of a 5% solution of deoxycholate. The preparation of Bacillus subtilis DNA labeled with [3H]thymidine and radioautography of cell-bound DNA were described (14). Pneumococcal DNA ...

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