بسم ا الرحمن الرحيم
BACTERIA IN DONOR BLOOD How to prevent? How to eliminate?
Akram Al-Hilali 2009 08/09/14
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How do bacteria enter the blood unit? ď Ź Most commonly from needle prick site at donation. Positive cultures are mostly skin contaminants. ď Ź Rarely donor has bacteria in his/her blood prior to donation. ď Ź Contamination after completion of donation due to faulty manufacture of bag or faulty sealing- far possibility. 08/09/14
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How serious is the contamination? Roughly 1 in 2000 platelet units. 1000 clinical cases per year in USA from platelet transfusion. Bacterial load tends to be high if platelet unit is contaminated, because of storage temperature. Could be fatal 08/09/14
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How do we prevent bacterial entry? First step Skin disinfection must be proper in procedure. Skin disinfectant must be effective. Isopropyl alcohol swab may be acceptable for sample taking, but not for blood donation. Povidone iodine or chlorhexidine in alcohol need to be used. Pierce needle I min after application This precaution will still allow some skin contaminants to pass into the blood because procedure is not followed or there is heavy skin bacterial flora. 08/09/14
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How do we prevent bacterial entry? Second step
We suppose that some bacteria have entered, in spite of 1st precaution. Units are left at room temperature for at least 2 hours for phagocytes to eliminate the bacteria. Storage of red cell units at 4oC will prevent multiplication of most bacteria. However, platelets are stored at room temperature, allowing multiplication of all bacteria. 08/09/14
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How do we prevent bacterial entry? Third step ď Ź Since bacterial contamination is obviously coming with the first small amount of blood introduced into the bag then we may get rid of this amount. ď Ź The trap-pouch was devised for this purpose. ď Ź Certainly, platelet contamination with bacteria and their transfer to recipients have been reduced, but not completely eliminated, by the three preventive steps. 08/09/14
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Can we prove or exclude bacterial contamination in a platelet unit? Culture of all units while quarantined. Practical? Non-culture quick indicatordemonstrated contamination by bacteria. Quality control on platelets should include bacterial culture. This will test our system but not exclude contamination of a particular, untested unit. 08/09/14
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BACTERIAL DETECTION SYSTEMS
PALL BDS Detection of bacteria By checking for oxygen Reduction.
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OTHER SYSTEMS FOR BACTERIAL DETECTION SCANSYSTEM: Bacteria are stuck on a black membrane. Fluorescence dye added and bacteria are detected by solid phase flow method. Ordinary Culture: takes at least a day. Dynamic light scattering by bacteria. Reagent strips (pH and glucose). Crude. Bacterial lysis and ATP measurement interference from leukocytes. Gene probe technology. None is practical 08/09/14
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How to eliminate bacterial contamination after the event? Photochemical methods Addition of an inactive chemical, that will be activated by UV light. Psoralen and Riboflavin are the most effective agents so far. Psoralen 59 is the best Psoralen so far tested and is available commercially, but only for red cells at present. It has to be removed from platelets after it plays its inactivation role. Riboflavin doe not need to be removed.
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How do Photo chemicals act? These compounds, when activated, will stick between the two spirals of DNA double helix and so prevent bacteria from functioning or multiplying. Therefore, they act on any cell with DNA, and even RNA. So, viruses, parasites and leukocytes are also eliminated 08/09/14
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Psoralen
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Prevention or Treatment? Prevention is obviously better, if it is possible to achieve reliably. It is also less expensive However, in places where all the preventive procedures are carried out few cases of bacterial transfer by platelet concentrate are still being reported. Also, those preventive procedures do not deal with viruses and parasites. All we need is more money. Available? 08/09/14
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