الفهرس 
History of blood transfusionOnly 14 pages are availabe for public view
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Abstract
Bacterial contamination of blood and its cellular components remains an unresolved problem in transfusion medicine, and is considered to be the most common microbiological cause of transfusion associated morbidity and mortality. This is because contaminated units may contain large numbers of virulent bacteria as well as, endotoxins that are considered to be fatal to the recipients.
Endotoxins are high-molecular weight complexes of lipopolysaccharides that constitute the major cell wall component in all Gram-negative bacterial families. These molecules have been intensively investigated because of the increasing appreciation of their potentially pathogenic role in a wide variety of human disease states.
Transfusion transmitted bacterial contamination has been identified as the most common and severe infectious complication associated with transfusion. Gram negative rods have been considered to be the cause of the most severe septic transfusion reactions and most of the deaths associated with bacterial contamination of blood components.
The symptoms and signs of transfusion-related bacterial infection are nonspecific and may mimic noninfectious transfusion reactions. Severe reactions are more common after receipt of contaminated erythrocytes, because more virulent Gram-negative bacteria are involved. Platelet recipients are often immune-compromised and may also suffer from severe sequelae.
The initial signs and symptoms, when they occur, include fever and chills, which usually begin shortly after (within 2 hours) the start of the transfusion. The clinical severity of a transfusion-associated septic reaction can vary considerably, depending on recipient characteristics, such as underlying disease, leukocytic count, the status of immune system, and whether the recipient is receiving concomitant antibiotic therapy.
The pre-transfusion detection of bacteria is an important potential method to reduce the risk of transfusion-associated bacteremia and septic reactions. However, no single currently available laboratory technique is ideal.
The ideal characteristics of a bacterial detection method are that it is simple, practical, rapid, sensitive, specific, and inexpensive.
Various approaches to detect bacterial contamination besides visual inspection before release of the component are culture, endotoxin assays and detection of bacterial nucleic acids by amplification techniques. Other tests such as determining pH or glucose levels, or direct bacterial staining with Gram’s stain or acridine orange have similarly not been very useful due to relatively low sensitivity when compared with bacterial concentrations that can cause sepsis.
The Limulus amebocyte lysate assay has been the method of choice for the detection and quantization of endotoxin/lipopolysaccharides in serum and plasma since the test was first described.
A wide variety of measures have been proposed in order to reduce the frequency of transfusion-associated septic reactions and many of these measures are being actively investigated, and in some countries being instituted. To reduce the risk of blood contamination the following measures should be followed: donor screening, skin preparation, diversion of the initial blood draw, leukodepletion, pathogen reduction and reducing recipient exposure.
The present study aimed to:
1. Detect endotoxins and bacterial agents in collected blood bags.
2. Detect the transmission of endotoxins to the recipients of the blood bags with detectable endotoxins.
3. Detect the transmission of bacterial agents to the recipients of the blood bags with isolated bacterial agents.
The study involved 100 randomly selected blood bags and the recipients of these blood bags. They were all examined by LAL assay using gel clot method for detection of endotoxins and by blood culture technique for the detection of bacterial contamination.
- The following samples were collected:
1. About 10 ml of blood were aseptically withdrawn from each of one hundred blood bags.
2. About 10 ml of venous blood were aseptically withdrawn from each recipient of the 100 studied blood bags from a phlebotomy site other than that used for transfusion. The studied recipients were categorized as follows:
1. Recipients of blood bags with detectable endotoxins, who developed reactions during transfusion.
2. Recipients of blood bags with detectable endotoxins, who did not develop any reactions either during transfusion or immediately after the completion of transfusion.
3. Recipients of blood bags with no detectable endotoxins, but showed signs and symptoms of pyrogenic reactions.
Each collected blood sample (from blood bags and their recipients) was divided into two portions; one of which was used for cultural procedures and the other was used for the detection of endotoxin by LAL assay which is an enzymatic reaction and the enzymes are located in granules in the amebocytes. This reaction leads to clot formation in a cascade of enzyme activation steps.
Cultures were aerobically incubated at 37oC and daily examined for evidence of bacterial growth up to 7 days. When signs of growth appeared, full identification of isolated colonies was carried out.
The results of this study showed that:
1. Bacterial contamination was found in only one blood bag (1%) by blood culture technique.
2. Endotoxin was detected in five blood bags (5%) using LAL assay (gel clot method).
3. The only bag that gave positive blood culture yielded the growth of S. aureus, which was mostly a skin associated organism and was considered as a contaminant related to either procedure during donor venipuncture, or obtaining the sample for culture.
4. None of the 100 studied recipients of blood bags revealed positive blood culture.
5. Only one recipient of the five positive blood bags for endotoxin yielded a positive result for endotoxin after blood transfusion.
6. Only one recipient showed signs and symptoms of pyrogenic reactions following blood transfusion. This case suffered from multiple organ failure and died.
7. Most of positive blood bags by LAL assay for endotoxins (60%) have been stored for a duration of more than 7 days.
8. The most commonly associated clinical condition among male recipients was liver cirrhosis which accounted for (30.6%), while among females the most commonly associated clinical condition was breast carcinoma (42.1%).
It is concluded from this study that:
1. A complete & thorough questionnaire should be fulfilled for all blood donors to exclude bacterial infections and high risk factors.
2. A complete aseptic technique should be applied during blood donation and transfusion to lower the rate of bacterial contamination.
3. LAL assay is a rapid, easy to perform, and a highly sensitive test. It can detect as little as 0.03 endotoxin units per ml using the gel-clot method.
4. Not all endotoxins and bacterial agents could be transmitted to the recipients of blood bags, it depends on their volume and whether the recipient is on antibiotic therapy or not.
5. Selection of blood bags with the highest quality standards is essential for optimum blood management including collection, separation, preservation and transfusion.
6. Long duration of storage of blood bags contribute to their contamination. In this study most of positive blood bags by LAL assay for endotoxins (60%) have been stored for more than 7 days.