Prevalence of human erythrovirus B19 DNA in healthy Belgian blood donors and correlation with specific antibodies against structural and non-structural viral proteins.

BACKGROUND AND OBJECTIVES: Human parvovirus (erythrovirus) B19 is recognized as a major contaminant of blood and blood products. To reduce the risk of contamination, plasma-pool screening and exclusion of highly viraemic donations are recommended. The objectives of this study were to estimate the prevalence of B19 DNA in our blood-donor population, to determine the appropriate pool size to be tested (taking into account parameters such as prevalence, viral load, test sensitivity, and the efficacy of inactivation procedures), and to correlate viral loads with the serological status of donors as regards antibodies against different viral proteins. MATERIALS AND METHODS: Pools of different sizes were tested for B19, using a sensitive nested polymerase chain reaction (PCR) as well as an simple, un-nested, less sensitive PCR. Positive pools were resolved to the level of individual donations, and the viral load and serological markers were determined. RESULTS: Of 16,859 donations, 27 (one of 625) were found to be B19 DNA positive, with viral loads ranging from 10(2) to > 10(7) IU/ml. Twenty-five of the positive donations were tested for VP-specific anti-B19 antibodies, and eight (32%) were negative for both immunoglobulin (Ig)M and IgG. They were probably collected in the preseroconversion window period or from chronic carriers without detectable antibodies. We regarded the seven (28%) IgM-positive donors as being in the early phase of infection. The remaining 10 (40%) IgM-negative, IgG-positive donors were probably carriers of persistent infection (i.e. PCR positive despite the presence of IgG antibodies), as suggested by their low viral loads (< 10(4) IU/ml). Fifteen out of 36 major pools contained one or more contaminated donations. Among these, 12 tested positive by nested PCR and only three by un-nested PCR, this reflecting a viral load of > 10(4) IU/ml. CONCLUSIONS: By testing all donations as pools of 480 by un-nested PCR, and resolving positive pools to identify the responsible donations, it is possible to ensure that the viral load in fractionation pools (5000 donations) remains < 10(3) IU/ml, compatible with the efficacy of inactivation procedures and complying with Food and Drug Administration (FDA) recommendations.

PCR detects HCV RNA in a plasma pool contaminated by a single preseroconversion donation of genotype 5a.

BACKGROUND AND OBJECTIVES: To determine the prevalence of HCV-RNA-positive plasma pools in Belgium, to validate our PCR method and to increase the safety of the released blood products. MATERIALS AND METHODS: Plasma pools consisting each of about 5,000 donations from Belgian unpaid volunteer blood donors were analysed by PCR for the presence of HCV RNA. Two different extraction methods were compared and validated. RESULTS: Two out of 367 plasma pools were found to be HCV RNA positive and were discarded. For one of these two pools, the look-back procedure identified an anti-HCV-negative contaminated donation. The HCV genotype of both the contaminated pool and the donation was 5a, a genotype rare in Europe. The viral load of the preseroconverted donation was 2.9 x 10(7) gEq/ml according to the bDNA method. CONCLUSION: In the case of plasma derivatives, various important steps are already included to increase safety. Nucleic acid testing of manufacturing plasma pools ensures that viral load in the starting material is as low as possible.

Immediate implants: indications and clinical decision making.

This paper is intended to describe the current concepts in timing of implant placement, and to address some of the controversies surrounding implants and bone grafting.

Treatment of the failing implant: case reports.

Three case reports of treatment of the failing implant are presented. The implants were immobile but had lost a significant amount of osseous support. The cause of failure was determined to be a combination of bacterial and occlusal traumatogenic insult. The defects were debrided and the implant surface was detoxified with tetracycline. Decalcified freeze-dried bone allograft was implanted in the osseous defects and covered with expanded polytetrafluoroethylene material in accordance with principles of guided tissue regeneration. The barrier membrane was removed 6 to 8 weeks after placement. Eight months to 1 year posttreatment, all sites demonstrated a substantial reduction in probing depth, a gain in clinical attachment, and bone fill of the defects adjacent to the implant.

Sensitivity of Escherichia coli to cephaloridine at different growth rates.

Steady-state populations of Escherichia coli B/r were treated with cephaloridine at minimal inhibitory concentrations. The antibiotic sensitivity of the cells and the localization of spheroplast emergence along the cell surface were examined as a function of cell length and growth rate. In fast-growing populations (greater than 1 division per h) the sites of cephaloridine interaction occurred preferentially at the cell pole in the smaller cells and at the cell center in dividing cells. At decreasing growth rates the cells became more resistant to cephaloridine, and a gradual shift from the cell pole toward the cell center was observed for the sphere position. A similar growth rate-dependent change in localization was found for sucrose-induced plasmolysis vacuoles.