Prevention of Yersinia enterocolitica, Pseudomonas fluorescens, and Pseudomonas putida outgrowth in deliberately inoculated blood by a novel pathogen-reduction process

Stored Canine Whole Blood Units: What is the Real Risk of Bacterial Contamination?

Background

Bacterial contamination of whole blood (WB) units can result in transfusion‐transmitted infection, but the extent of the risk has not been established and may be underestimated in veterinary medicine.

Objectives

To detect, quantify, and identify bacterial microorganisms in 49 canine WB units during their shelf life.

Animals

Forty‐nine healthy adult dogs.

Methods

Forty‐nine WB units were included in the study. Immediately after collection, 8 sterile samples from the tube segment line of each unit were aseptically collected and tested for bacterial contamination on days 0, 1, 7, 14, 21, 28, 35, and 42 of storage. A qPCR assay was performed on days 0, 21, and 35 to identify and quantify any bacterial DNA.

Results

On bacterial culture, 47/49 blood units were negative at all time points tested, 1 unit was positive for Enterococcus spp. on days 0 and 1, and 1 was positive for Escherichia coli on day 35. On qPCR assay, 26 of 49 blood units were positive on at least 1 time point and the bacterial loads of the sequences detected (Propionobacterium spp., Corynebacterium spp., Caulobacter spp., Pseudomonas spp., Enterococcus spp., Serratia spp., and Leucobacter spp.) were <80 genome equivalents (GE)/μL.

Conclusions and Clinical Importance

Most of the organisms detected were common bacteria, not usually implicated in septic transfusion reactions. The very low number of GE detected constitutes an acceptable risk of bacterial contamination, indicating that WB units have a good sanitary shelf life during commercial storage.

Detection of bacterial contamination and DNA quantification in stored blood units in 2 veterinary hospital blood banks

Blood transfusions in veterinary medicine have become increasingly more common and are now an integral part of lifesaving and advanced treatment in small and large animals. Important risks associated with transfusion of blood products include the transmission of various infectious diseases. Several guidelines suggest what infectious agents to screen for in canine and feline transfusion medicine. However, while the risk of bacterial contamination of blood products during storage and administration has not been documented in veterinary medicine, it has emerged as a cause of morbidity and mortality in human transfusion medicine. Clinical experience shows that the majority of blood component bacterial contaminations are caused by only a few species. Unlike other types of bacteria, psychrotolerant species like Pseudomonas spp. and Serratia spp. can proliferate during the storage of blood units at 4°C from a very low titer at the time of blood collection to a clinically significant level (> 10(5) CFU/mL) causing clinical sepsis resulting from red blood cell concentrate transfusions in human medicine. The purpose of this report was to describe the detection and quantification procedures applied in 4 cases of bacterial contamination of canine and feline blood units, which suggest the need for further investigations to optimize patients' safety in veterinary transfusion medicine.

Developing pathogen reduction technologies for RBC suspensions

Numerous studies have evaluated a wide variety of photosensitizers and alkylating agents as candidates for a pathogen reduction process to be used in RBC suspensions. The methodologies that produce robust inactivation of pathogens with maintenance of RBC properties during storage involve those that specifically target nucleic acids. This has been demonstrated through in vitro studies by flexible photosensitizers, which specifically target nucleic acid but do not engage in photochemistry when free in solution and nucleic acid alkylating agents in conjunction with extracellular quencher(s) to protect against RBC membrane alkylation. The flexible photosensitizer method must be scaled up to entire units, and toxicology studies would need to be performed for further development. Clinical trials will ultimately be necessary to further develop either flexible photosensitizers or nucleic acid alkylating methods with quenchers for use in Transfusion Medicine.

Pathogen inactivation: the definitive safeguard for the blood supply

CONTEXT

Pathogen inactivation provides a proactive approach to cleansing the blood supply. In the plasma fractionation and manufacturing industry, pathogen inactivation technologies have been successfully implemented resulting in no transmission of human immunodeficiency, hepatitis C, or hepatitis B viruses by US-licensed plasma derivatives since 1985. However, these technologies cannot be used to pathogen inactivate cellular blood components. Although current blood donor screening and disease testing has drastically reduced the incidence of transfusion-transmitted diseases, there still looms the threat to the blood supply of a new or reemerging pathogen. Of particular concern is the silent emergence of a new agent with a prolonged latent period in which asymptomatic infected carriers would donate and spread infection.

OBJECTIVE

To review and summarize the principles, challenges, achievements, prospective technologies, and future goals of pathogen inactivation of the blood supply.

DATA SOURCES

The current published English-language literature from 1968 through 2006 and a historical landmark article from 1943 are integrated into a review of this subject.

CONCLUSIONS

The ultimate goal of pathogen inactivation is to maximally reduce the transmission of potential pathogens without significantly compromising the therapeutic efficacy of the cellular and protein constituents of blood. This must be accomplished without introducing toxicities into the blood supply and without causing neoantigen formation and subsequent antibody production. Several promising pathogen inactivation technologies are being developed and clinically tested, and others are currently in use. Pathogen inactivation offers additional layers of protection from infectious agents that threaten the blood supply and has the potential to impact the safety of blood transfusions worldwide.

Pathogen inactivation techniques

The desire to rid the blood supply of pathogens of all types has led to the development of many technologies aimed at the same goal--eradication of the pathogen(s) without harming the blood cells or generating toxic chemical agents. This is a very ambitious goal, and one that has yet to be achieved. One approach is to shun the 'one size fits all' concept and to target pathogen-reduction agents at the Individual component types. This permits the development of technologies that might be compatible with, for example, plasma products but that would be cytocidal and thus incompatible with platelet concentrates or red blood cell units. The technologies to be discussed include solvent detergent and methylene blue treatments--designed to inactivate plasma components and derivatives; psoralens (S-59--amotosalen) designed to pathogen-reduce units of platelets; and two products aimed at red blood cells, S-303 (a Frale--frangible anchor-linker effector compound) and Inactine (a binary ethyleneimine). A final pathogen-reduction material that might actually allow one material to inactivate all three blood components--riboflavin (vitamin B2)--is also under development. The sites of action of the amotosalen (S-59), the S-303 Frale, Inactine, and riboflavin are all localized in the nucleic acid part of the pathogen. Solvent detergent materials act by dissolving the plasma envelope, thus compromising the integrity of the pathogen membrane and rendering it non-infectious. By disrupting the pathogen's ability to replicate or survive, its infectivity is removed. The degree to which bacteria and viruses are affected by a particular pathogen-reducing technology relates to its Gram-positive or Gram-negative status, to the sporulation characteristics for bacteria, and the presence of lipid or protein envelopes for viruses. Concerns related to photoproducts and other breakdown products of these technologies remain, and the toxicology of pathogen-reduction treatments is a major ongoing area of investigation. Clearly, regulatory agencies have a major role to play in the evaluation of these new technologies. This chapter will cover the several types of pathogen-reduction systems, mechanisms of action, the inactivation efficacy for specific types of pathogens, toxicology of the various systems and the published research and clinical trial data supporting their potential usefulness. Due to the nature of the field, pathogen reduction is a work in progress and this review should be considered as a snapshot in time rather than a clear picture of what the future will bring.

The development of phenothiazinium photosensitisers

Methylene blue has been widely used since the late 19th century in biomedical research, and was the lead compound in several important clinical areas, including therapeutics for malaria and schizophrenia. The photodynamic therapy (PDT) of cancer and, more recently, of microbial infection (photodynamic antimicrobial chemotherapy (PACT)) has also employed methylene blue and its congeners, among other chemical types, due to the low human toxicities and efficient photosensitising properties of the group. However, little work has been carried out in terms of derivative and structure-activity development, most reports covering standard, commercially available compounds. This review deals with the evolution of phenothiazinium photosensitisers for both PACT and PDT use.

Detection of bacteria in red blood cell concentrates by the Scansystem method

Bacterial contamination remains one of the major risks associated with blood product transfusion. The kinetics of bacterial growth in red blood cell concentrates (RBCC) is different than otherwise due to storage at 4 degrees C, conditions in which most bacteria do not survive. Psychrophilic bacteria such as Yersinia enterocolitica, however, can proliferate from a very low level of contamination to clinically significant levels at 4 degrees C and are known to cause severe transfusion-related infections. A screening method allowing the early detection of very low levels of bacteria in RBCC would improve transfusion safety. The Scansystem method has been previously described for detection of bacteria in platelet concentrates. We present here a modification of the system for detection of low levels of bacteria in RBCC. The Scansystem RBC kit protocol requires three steps, i.e., the agglutination and selective removal of RBCs, a labeling stage during which bacteria are labeled with a DNA-specific fluorophore, and finally recovery of bacteria on the surface of a black membrane for analysis using the Scansystem. The entire procedure from sampling to result can be completed in 90 min. Both gram-negative and gram-positive bacteria in RBCC are detected with a higher sensitivity than with currently available culture-based methods. The Scansystem RBC kit is shown to be sensitive enough to identify low-level bacterial contamination in a single unit tested in a pool of up to 20 RBCC samples (detection limit of between 1 and 10 CFU/ml depending on the bacterial strain). The method therefore lends itself to incorporation into high-sample-throughput screening programs.

Protecting the blood supply from emerging pathogens: the role of pathogen inactivation

Although the risk of infection by blood transfusion is relatively low, breakthrough infections still occur, Transfusion-related fatalities caused by infections continue to be reported, and blood is not tested for many potentially dangerous pathogens. The current paradigm for increasing the safety of the blood supply is the development and implementation of laboratory screening methods and restrictive donor criteria. When considering the large number of known pathogens and the fact that pathogens continue to emerge, it is clear that the utility of new tests and donor restrictions will continue to be a challenge when considering the cost of developing and implementing new screening assays, the loss of potential donors, and the risk of testing errors. Despite improving the safety of blood components, testing remains a reactive approach to blood safety. The contaminating organisms must be identified before sensitive tests can be developed. In contrast, pathogen inactivation is a proactive strategy designed to inactivate a pathogen before it enters the blood supply. Almost all pathogen inactivation technologies target nucleic acids, allowing for the inactivation of a variety of nucleic acid-containing pathogens within plasma, platelets, or red blood cells thus providing the potential to reduce transfusion-transmitted diseases. However, widespread use of a pathogen inactivation technology can only be realized when proven safe and efficacious and not cost-prohibitive.

Pathogen inactivation technology: cleansing the blood supply

The calculated residual infectious risk of HIV, hepatitis B virus (HBV) and hepatitis C virus (HCV) from blood transfusion is extremely low. However, the risk of bacterial contamination remains and a variety of other agents including emerging viruses, protozoa and tick-borne agents threaten blood supplies and undermine public confidence in blood safety. Traditional methods of donor screening and testing have limited ability to further reduce disease transmission and cannot prevent an emerging infectious agent from entering the blood supply. Pathogen inactivation technologies have all but eliminated the infectious risks of plasma-derived protein fractions, but as yet no technique has proved sufficiently safe and effective for traditional blood components. Half-way technologies can reduce the risk of pathogen transmission from fresh frozen plasma and cryoprecipitate. Traditional methods of mechanical removal such as washing and filtration have limited success in reducing the risk of cell-associated agents, but methods aimed at sterilizing blood have either proved toxic to the cells or to the recipients of blood components. Several promising methods that target pathogen nucleic acid have recently entered clinical testing.

Inactivation of Gram-negative and Gram-positive bacteria in red cell concentrates using INACTINE PEN110 chemistry

BACKGROUND AND OBJECTIVES

The risk of transfusion-transmitted bacterial infections as a result of the presence of bacteria in blood is one of the major concerns in transfusion medicine. The purpose of this study was to investigate whether bacteria inoculated into red blood cell concentrates can be inactivated by the INACTINE PEN110 pathogen-reduction process. Four bacterial species were chosen for the study: anaerobic Gram-positive Clostridium perfringens and Propionibacterium acnes, known to be transfusion-transmitted; and two Gram-negative species, Acinetobacter johnsonii and Acinetobacter lwoffii, recently reported to be a common cause of transfusion-associated infections in Europe.

MATERIALS AND METHODS

Identical units of leucoreduced red cell concentrates were inoculated with A. johnsonii, A. lwoffii, C. perfringens, or P. acnes. The 4 degrees C control units were put on storage immediately after receiving the spike. The test units were subjected to PEN110 treatment and then stored. The bacterial titre in all units was monitored during a 6-week storage period.

RESULTS

The PEN110 inactivation of all tested bacterial strains was time- and titre-dependent. For A. johnsonii and A. lwoffii, no viable bacteria were detected in the units spiked with up to 10(4) colony-forming units (CFU)/ml and treated with PEN110. For red cell units spiked with 10(4)-10(5) CFU/ml of C. perfringens and P. acnes, no viable bacteria were detected in the units treated with PEN110. In control units, there was a gradual decrease in A. johnsonii, A. lwoffii and C. perfringens titres during cold storage, while P. acnes titres remained stable.

CONCLUSIONS

The PEN110 pathogen-reduction process was demonstrated to inactivate high titres of A. johnsonii, A. lwoffii, C. perfringens and P. acnes in red cell concentrates.

Inactivation of protozoan parasites in red blood cells using INACTINE PEN110 chemistry

BACKGROUND

The transmission of parasites, including Babesia, plasmodia, and Trypanosoma cruzi, via transfusions is an important public health concern. INACTINE technology is a pathogen-reduction process that utilizes PEN110, an electrophilic agent that inac-tivates a wide range of pathogens by disrupting nucleic acid replication. The present study investigated the effect of PEN110 treatment on the viability of protozoa in RBCs.

STUDY DESIGN AND METHODS

B. microti-parasitized RBCs from infected hamsters were treated with PEN110 and inoculated to naïve animals. Parasitemia was detected by blood smears and PCR. Human RBCs infected with P. falciparum were treated with PEN110 and incubated with fresh RBCs. P. falciparum multiplication was detected by blood smears. Human RBCs spiked with T. cruzi and treated with PEN110 were analyzed for the presence of live parasites using in-vitro infectivity assay or by inoculating susceptible mice.

RESULTS

Treatment of RBCs infected with B. microti or P. falciparum with 0.01 to 0.1 percent (vol/vol) PEN110 resulted in parasite inactivation to below the limit of detection during 24 hours. T. cruzi inoculated into human RBCs was inactivated below the limit of detection by 0.1 percent PEN110 after 3 hours.

CONCLUSION

The study demonstrates that treatment of blood with PEN110 is highly effective in eradicating transfusion-transmitted protozoan parasites.

Risk and prevention of transfusion-related sepsis

PURPOSE OF REVIEW

Transfusion-related sepsis is both the oldest recognized and most common transfusion-associated infectious risk. Despite an increased awareness and recognition of this problem, particularly with room-temperature stored platelets, strategies to prevent or reduce the occurrence of this problem have proved daunting.

RECENT FINDINGS

With the recent FDA approval of culture methods for platelet bacterial testing and the promulgation of accreditation standards by the College of American Pathologists and American Association of Blood Banks to limit and detect platelet bacterial contamination, it is anticipated that the frequency of this problem will now begin to diminish.

SUMMARY

As methods to reduce and/or inactivate pathogens emerge, it is hoped that transfusion-related sepsis will essentially disappear.

Pathogen inactivation of RBCs: PEN110 reproductive toxicology studies

BACKGROUND

The novel PEN110 chemistry (INACTINE, V.I. Technologies) process for the purification of blood for transfusions involves treating WBC-reduced RBCs with PEN110 to inactivate a wide spectrum of pathogens. The washed RBC preparation has a residual PEN110 level of less than 0.00005 mg per mL. It is important to verify that the trace amounts of residual PEN110 in blood prepared for transfusions will not produce adverse effects on reproduction, fertility, or fetal development.

STUDY DESIGN AND METHODS

A fertility and early embryonic development study was conducted in male and female Sprague-Dawley rats at IV doses of up to 0.5 mg PEN110 per kg of body weight following standard regulatory protocols. A fetal developmental study was conducted in Hra:(NZW)SPF pregnant rabbits at IV doses of up to 1.0 mg per kg of body weight following standard regulatory protocols. In both cases the highest dose was shown to be a maximum tolerated dose in pregnant animals based on body weight gain during pregnancy.

RESULTS

In the fertility and early embryonic development study, no treatment-related effects were noted on estrous cycles, pregnancy rate, implantation sites, corpora lutea, number of resorptions, and live embryos in female rats or sperm motility, sperm morphology, and sperm counts in male rats. In the fetal developmental study, PEN110 had no effect on embryofetal viability and growth. This is consistent with other data indicating that PEN110 is rapidly cleared by urinary excretion. On a mg per kg of body weight dose basis, the no-observed-effect level doses for rats in the fertility study and rabbits in the developmental study were 2,000 and 4,000 (320 and 1,300 scaled to dose per unit body surface area [DBSA]) times that which a person would receive given 1 unit of treated blood. Considering the cumulative animal dosages, the safety factor values increase to 48,000- and 60,000-fold (7,700 and 19,400 scaled to dose per unit body surface area).

CONCLUSION

These results indicate that the trace amount of residual PEN110 in the purified blood component is well below the level that could present a risk of reproductive toxicity to the patient.

West Nile virus in blood: stability, distribution, and susceptibility to PEN110 inactivation

BACKGROUND

The outbreak of West Nile virus (WNV) is the most recent reminder that the blood supply continues to be vulnerable to emerging and reemerging pathogens. A potentially prospective approach to reducing the risk of transfusion-transmitted infections of a known or newly emerging microbe is implementation of a broad-spectrum pathogen reduction technology. The purpose of this study was to evaluate the susceptibility of WNV to PEN110 inactivation in RBCs and to characterize the WNV interaction with blood, including the stability of WNV in RBCs stored at 1 to 6 degrees C, its distribution and infectivity, and its ability to infect WBCs.

STUDY DESIGN AND METHODS

Inactivation was performed with three WNV isolates spiked into WBC-reduced RBCs. The stability of the virus was evaluated by spiking two viral loads into RBCs followed by storing at 1 to 6 degrees C for up to 42 days. The distribution of the virus in plasma, RBCs, and PBMCs was evaluated with whole blood from infected hamsters. Finally, in vitro propagation of WNV was evaluated with the THP-1 cell line and primary monocytes.

RESULTS

The kinetics of PEN110 inactivation of WNV isolates RI-44, NJ-176, and 99-3494031 were fast and complete within 24 hours with reduction factors of 5 to 7 log plaque-forming units per mL. WNV remained infectious for up to 42 days at 1 to 6 degrees C. The WNV titers in whole blood, plasma, RBCs, and PBMC fractions were equally distributed and ranged from 2 to 3 log tissue culture infectious dose 50 percent per mL. Productive infection of stimulated monocytes and THP-1 cells was also demonstrated.

CONCLUSIONS

These studies demonstrated that PEN110 efficiently inactivated WNV in RBCs and whole blood from infected hamsters to the limit of detection. WNV survived in RBCs stored at 1 to 6 degrees C with a gradual loss of titer but infectivity could still be observed for up to 42 days. In addition, it was observed that WNV was equally distributed in all blood fractions including PBMCs and it was possible to establish productive infection of a human monocytic cell line and stimulated human monocytes.