Dr Anand Deshpande P D Hinduja National Hospital & MRC
Mumbai
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While the blood bank community has successfully implemented the
high standards of blood screening for viral markers including NAT
screening, transmission of donor bacteria has clearly emerged as
the greatest infectious risk to transfusion safety Bacterial
contamination of blood products is a persistent but often
overlooked problem in Transfusion Medicine
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The dramatic decrease in risk of transfusion-transmitted viral
disease was accomplished by conversion from Paid to volunteer whole
blood donors in the 1970s. Increased direct questioning of donors
regarding risks for the Viruses and increased testing of collected
donor blood for antibodies, antigens and nucleic acid of these
viruses starting in the 1970s. Risk of hepatitis B may decrease
further with universal childhood vaccination. Not shown in the
graph are the rare risks of other transmissible diseases. The
dashed line indicates the unknown risks, if any, of new viruses and
other potentially emerging pathogens, such as prions that cause new
variant Creutzfeldt-Jakob Disease. (J of Am Med Ass, Feb 2001,
Volume 285, No 5; 579
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SHOT DATA
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CAP CHECKLIST TRM.44955PHASE II Does the laboratory have a
validated system to detect the presence of bacteria in platelet
concentrates ? For random donor platelets, any of the following
testing methods satisfy this checklist question: detection of
decreased pH or glucose by analytic instrument or dipstick; gram
stain; acridine orange stain. Though of low sensitivity, these
methods may detect units that are heavily contaminated by bacteria.
Culture or FDA- approved commercial detection systems have greater
sensitivity. The swirling technique is not recommended because of
its very low sensitivity.
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CAP CHECKLIST TRM.44955 Revised (Nov 2011)PHASE II Bacterial
Contamination in Platelets The enhanced sensitivity requirement
reflects the availability of multiple FDA-cleared quality control
strategies; insensitive methods including pH, glucose and
microscopy are no longer acceptable. Equivalent system is defined
as a system that has been validated to demonstrate comparable or
improved sensitivity in CFU/mL. If this testing is performed by the
supplier of platelet components, the laboratory can satisfy this
checklist requirement by having an agreement with the supplier to
be notified of supply units suspected of containing bacteria.
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Origin of bacteria From donor Unsuspected bacterimia
Venipuncture site Rarely during processing and storage At the time
of transfusion
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Risk estimates HIV / HCV / HAV 1 in a few million HBV 1 in 0.3
million Bacteria (RBCs) 1 in 30,000 Bacteria (Platelets) 1 in
3000
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Organisms in RBC component Yersinia entercolotica, Serratia
& Pseudomonas Y. enterocolitis fever, diarrhea Endotoxins
Initial lag phase rapidly proliferative after 20 25 days of storage
25 fatalities reported in USA (1995 2004) Risk of death 0.13 /
million Autologous
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Transfusion fatalities by organisms in Red cell transfusions
(25)
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Summary of Organisms from RBC Transfusions identified in the
BACON, SHOT and BACTHEM studies
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Organisms in Platelet component 50 -250 times higher risk than
viral infection Room temperature storage Organisms are varied
coagulase negative staphylococcus commonest, Bacillus Contamination
risk is 1:3000 approx, whereas Septic reactions occur in 1/4 th to
1/6 th of the contaminated platelets Fatalities gram negative
organisms Clinically, Fever-Hypertension-Sepsis-Death Sometimes
difficult to diagnose
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Plasma / Cryo Frozen state Rarely associated with
contamination
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Strategies to reduce risk of post transfusion sepsis BBacterial
Avoidance GGrowth inhibition DDetection EElimination
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I. Bacterial Avoidance A] Donor screening Careful selection of
healthy blood donors Recent dental procedures Recent use of
antibiotics/Medical & surgical interventions Problems e.g.
Yersinia sepsis retrospective analysis 50 % donors had GI symptoms
Special considerations Autologous blood units
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Bacterial avoidance B] Skin preparations Not possible to have
sterile venipuncture Sebaceous glands / Hair follicles Scarring or
dimpling Isopropyl alcohol + Iodine + Isopropyl alcohol
Chlorhexidine
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Percentage of Donors with Bacteria growth after skin
disinfection
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Bacterial avoidance C] Diversion Significant reduction in blood
contamination if first 10 -20 ml of blood is diverted to the pouch
Study from Netherlands 0.35 % - 0.21 % Expected to reduce gram
positive organisms
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Apheresis vs WBD platelets Significant reduction in sepsis
(John Hopkins study) 1:4818 1: 15098 Cultures with apheresis
platelets
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II. Growth inhibitors Optimising storage temperature Red cells
(1 0 6 0 C) Yersinia / Serratia Frozen - ? Practicality Platelets
(20 0 24 0 C) 4 0 C Temperature induced activation
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Growth inhibition Optimising storage time A. Red Cells Yersinia
sepsis in units > 25 days old Proposed to reduce shelf life for
25 days Rejected 20 % units > 25 days - Recruiting new donor -
Units < 25 days also causes sepsis
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B. Platelets Ideal would be 1 2 days Diagnostic disease markers
impossible (NAT/Culture)
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III. Bacterial detection No ideal procedure for detection of
bacteria Limitations Short shelf life of 5 days The amount of
bacterimia changes with time Contamination may occur during
sampling processes Innoculation may be very small
IV. Bacterial elimination Leucodepletion by filtration
Prestorage leucocyte filters Related to leucocyte phagocytosis
Related to direct filter binding mechanism No evidence that
prestorage leucocyte reduction by filtration contributed to
bacterial proliferation
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V. Pathogen inactivation Final common pathway Photodynamic and
photochemical methods
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UK experience - Poster at Cancun ISBT - 2012 1996 2010 40 cases
SHOT 33/40 platelet transfusion 9/33 fatalities NHS BacT / ALERT
for culture 0.03% confirmed positive No report of transmission of
bacteria by transfusion of platelets in 2011
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Factors affecting outcome of Transfusion of Bacterially
contaminated blood components
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Under reporting Septic or fatal reaction elderly, neonates or
patients immunocompromised by illness or chemo If patients on
antimicrobial therapy - severity Low levels of bacterial
contamination causes mild symptoms like fever and chills resembling
FNHTRs
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Conclusion . Significant progress in understanding Source
reduction by good skin preparation and diversion pouch Better and
specific method like Bact culture Towards safer blood and better
patient care
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Conclusion There is always another pathogen waiting its turn A
zero-risk blood supply is not achievable The safest transfusion is
still the one not infused.