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4 - Retroviruses
- from Section 1 - Agents
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- By Brian C. Dow, Consultant Clinical Microbiologist; Head, Scottish National Blood Transfusion Service, National Microbiology Reference Unit, West of Scotland, Transfusion Centre, Glasgow, UK, Eberhard W. Fiebig, Associate Professor/Vice Chair, UCSF Department of Laboratory Medicine; Chief, Laboratory Medicine Service, San Francisco General Hospital, San Francisco, California, USA, Michael P. Busch, Director, Blood Systems Research Institute; Vice President Research and Scientific Programs, Blood Systems, Inc.; Professor of Laboratory Medicine, University of California, USA
- Edited by John A. J. Barbara, University of the West of England, Bristol, Fiona A. M. Regan, Marcela Contreras, University of the West of England, Bristol
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- Book:
- Transfusion Microbiology
- Published online:
- 12 January 2010
- Print publication:
- 24 April 2008, pp 59-66
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Summary
Retroviruses have a wide distribution in nature, with examples in insects, reptiles and nearly all mammals. The human retrovirus, human immunodeficiency virus (HIV 1 and 2), belongs to the lentivirus group of the retrovirus family, whilst human T-cell lymphotropic virus (HTLV I and II) belongs to the oncorna group. Human T-cell lymphotropic virus I and II are thought to have evolved from simian T-lymphotropic retroviruses that were transmitted to humans over the past centuries or millenia. Human immunodeficiency virus is thought to have derived from simian immunodeficiency viruses that are endemic in chimpanzees in Central Africa, and probably infected natives over the past century (Sharp et al., 2001).
Retroviruses are membrane-coated, single stranded RNA viruses that have a distinct genomic organization and require the presence of reverse transcriptase in their replication cycle. In a typical infection, retrovirus particles attach to the cell membrane, reverse transcriptase copies viral RNA into complementary double stranded DNA and this is integrated into the host cell chromosome. Host cell enzymes help virus and host regulatory genes complete the retrovirus lifecycle by producing virions that bud from the plasma membrane to infect other cells or organisms.
Human immunodeficiency viruses 1 and 2
Definition and characteristics of agent
Human immunodeficiency virus was discovered in the early 1980s by two groups of workers, Montagnier in France and Gallo in the USA. Originally described as human T cell lymphotropic virus type III (HTLV-III), the virus was shown to infect T-cell lymphocytes.
7 - Bacterial contamination in blood and blood components
- from Section 1 - Agents
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- By Carl P. McDonald, Head of Bacteriology, NHS Blood and Transplant Colindale, London, UK, M. A. Blajchman, Canadian Blood Services and McMaster University, Hamilton, Ontario, Canada, Brian C. Dow, Consultant, Clinical Microbiologist; Head, Scottish National Blood Transfusion Service, National Microbiology Reference Unit, West of Scotland, Transfusion Centre, Glasgow, UK
- Edited by John A. J. Barbara, University of the West of England, Bristol, Fiona A. M. Regan, Marcela Contreras, University of the West of England, Bristol
-
- Book:
- Transfusion Microbiology
- Published online:
- 12 January 2010
- Print publication:
- 24 April 2008, pp 87-116
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Summary
Introduction
Bacterial transmission remains a significant problem in transfusion medicine. This issue is not a new problem and was first identified more than 60 years ago with the first report of a bacterial transfusion-transmission from a blood component in 1941 (Novak, 1939; Strumia and McGraw, 1941). Since the 1970s remarkable progress has been made in increasing the safety of the blood supply with regard to viruses. Unfortunately, this has not been the case with bacterial contamination. Moreover, the continued emphasis in striving for ‘zero risk’ with regard to blood-borne viruses and in measures to prevent the ‘potential’ problem of prion transmission has possibly been to the detriment of resolving the issue of bacterial contamination. The current risk of receiving bacterially contaminated platelet concentrates, however, may be 1000 times higher than the combined risk of transfusion-transmitted infection with the human immunodeficiency virus (HIV), hepatitis C virus, hepatitis B virus and human T-cell lymphotropic virus (HTLV) (Blajchman, 2002).
In the USA, from 1985 to 1999, bacterial contamination was the most frequently reported cause of mortality after haemolytic reactions, accounting for over 10% (77/694) of transfusion fatalities (Centre for Biologics Evaluation and Research, 1999). From 1986 to 1991, 29 out of 182 (16%) transfusion-associated fatalities reported to the USA Food and Drug Administration (FDA) were caused by bacterial contamination of blood components (Hoppe, 1992).
From 1994 to 1998, the French Haemovigilance system attributed 18 deaths (four occurring in 1997) to blood components contaminated with bacteria (Debeir et al., 1999; Morel, 1999a).
12 - Confirmatory testing and donor re-admission
- from Section 2 - Selection and testing
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- By Alan D. Kitchen, Head, National Transfusion Microbiology Reference Laboratory, NHS Blood and Transplant Colindale, London, UK, Brian C. Dow, Consultant, Clinical Microbiologist; Head, Scottish National Blood Transfusion Service, National Microbiology Reference Unit, West of Scotland, Transfusion Centre, Glasgow, UK
- Edited by John A. J. Barbara, University of the West of England, Bristol, Fiona A. M. Regan, Marcela Contreras, University of the West of England, Bristol
-
- Book:
- Transfusion Microbiology
- Published online:
- 12 January 2010
- Print publication:
- 24 April 2008, pp 173-182
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Summary
Introduction
The major focus in ensuring the microbiological safety of the blood supply relies heavily on the primary screening of donated blood. Although routine donor screening assays are highly sensitive, this sensitivity is often achieved at the expense of specificity (0.05–0.5%) (Dow, 2000).
Blood donations found to be initially reactive at donor testing sites should be repeat tested in duplicate. Should any of the repeat tests result in reactivity, the donation is classified as ‘repeatedly reactive’, the donor is flagged on the donor database and samples are submitted to the designated national reference laboratory or other designated facility. Regardless of confirmatory test results, the donation and all its associated components will be excluded from transfusion.
Throughout the world, blood services have differing policies with regard to confirmation of microbiology reactive donations. Most developed countries' services are capable of performing adequate confirmation of reactive donations. However, some services use an alternative strategy of reporting reactivity directly to the donors, often resulting in considerable donor anxiety and potential personal expense to reach a confirmatory conclusion. Obviously, in areas of high endemicity, there is a higher predictive value associated with a repeat reactive result and in this situation, simpler confirmatory algorithms can be utilized. Generally though, in developed countries, donors have relatively low prevalences of infection and therefore more complex confirmatory algorithms, like those described in this chapter, are often necessary before notification to the apparently healthy volunteer donor.