Formation of Single-Species and Multispecies Biofilm by Isolates from Septic Transfusion Reactions in Platelet Bag Model

During 2018-2021, eight septic transfusion reactions occurred from transfusion of platelet units contaminated with Acinetobacter spp., Staphylococcus saprophyticus, Leclercia adecarboxylata, or a combination of those environmental organisms. Whether biofilm formation contributed to evasion of bacterial risk mitigations, including bacterial culture, point-of-care testing, or pathogen-reduction technology, is unclear. We designed a 12-well plate-based method to evaluate environmental determinants of single-species and multispecies biofilm formation in platelets. We evaluated bacteria isolated from septic transfusion reactions for biofilm formation by using crystal violet staining and enumeration of adherent bacteria. Most combinations of bacteria had enhanced biofilm production compared with single bacteria. Combinations involving L. adecarboxylata had increased crystal violet biofilm production and adherent bacteria. This study demonstrates that transfusion-relevant bacteria can produce biofilms well together. More work is needed to clarify the effect of biofilms on platelet bacterial risk control strategies, but US Food and Drug Administration-recommended strategies remain acceptable.

Meta-analysis of bacterial growth characteristics in platelet components: Refining the inputs of a simulation analysis comparing the relative safety of testing strategies

BACKGROUND

The relative safety of bacterial risk control strategies for platelets that include culture with or without rapid testing has been compared using simulation analysis. A wide range of bacterial lag and doubling times were included. However, published data on growth rates are available and these data have not been synthesized. We conducted a systematic review and meta-analysis to estimate growth rates and used these estimates to refine a comparative safety analysis of bacterial risk control strategies in the FDA guidance STUDY DESIGN AND METHODS: Data were extracted from published studies on bacterial growth rates in platelet components during storage. These data were used to estimate the practical range of growth rates. This refined the inputs for a simulation model comparing the safety of the testing strategies.

RESULTS

In total, 108 growth curves for 11 different aerobic organisms were obtained. Doubling times ranged from 0.8 to 12 h, but the lower 90% range was approximately 1-5 h. The revised comparative safety simulation using the narrower 1-5-h range showed similar rankings to the prior simulation, with 48-h large-volume delayed sampling with 7-day expiration (48C-7) demonstrating the lowest-ranking relative performance at the 103 and 105 colony forming unit (CFU)/mL exposure thresholds.

DISCUSSION

This was a two-step study. First, meta-analysis of published data on aerobic bacterial growth rates in stored platelets showed the vast majority of doubling times were 1-5 h. Next, an updated comparative safety simulation yielded similar results to a prior study, with 48C-7 showing the least favorable relative safety performance.

Comparison of Bacterial Risk in Cryo AHF and Pathogen Reduced Cryoprecipitated Fibrinogen Complex

Until November 2020, cryoprecipitated antihaemophilic factor (cryo AHF) was the only United States Food and Drug Administration (FDA)-approved fibrinogen source to treat acquired bleeding. The post-thaw shelf life of cryo AHF is limited, in part, by infectious disease risk. Concerns over product wastage demand that cryo AHF is thawed as needed, with thawing times delaying the treatment of coagulopathic patients. In November 2020, the FDA approved Pathogen Reduced Cryoprecipitated Fibrinogen Complex for the treatment and control of bleeding, including massive hemorrhage, associated with fibrinogen deficiency. Pathogen Reduced Cryoprecipitated Fibrinogen Complex (also known as INTERCEPT^® Fibrinogen Complex, IFC) has a five-day post-thaw room-temperature shelf life. Unlike cryo AHF, manufacturing of IFC includes broad spectrum pathogen reduction (Amotosalen + UVA), enabling this extended post-thaw shelf life. In this study, we investigated the risk of bacterial contamination persisting through the cryoprecipitation manufacturing process of cryo AHF and IFC. Experiments were performed which included spiking plasma with bacteria prior to cryoprecipitation, and bacterial survival was analyzed at each step of the manufacturing process. The results show that while bacteria survive cryo AHF manufacturing, IFC remains sterile through to the end of shelf life and beyond. IFC, with a five-day post-thaw shelf life, allows the product to be sustainably thawed in advance, facilitating immediate access to concentrated fibrinogen and other key clotting factors for the treatment of bleeding patients.

Characterization of the Antibacterial Activity of an SiO2 Nanoparticular Coating to Prevent Bacterial Contamination in Blood Products

Technological innovations and quality control processes within blood supply organizations have significantly improved blood safety for both donors and recipients. Nevertheless, the risk of transfusion-transmitted infection remains non-negligible. Applying a nanoparticular, antibacterial coating at the surface of medical devices is a promising strategy to prevent the spread of infections. In this study, we characterized the antibacterial activity of an SiO₂ nanoparticular coating (i.e., the “Medical Antibacterial and Antiadhesive Coating” [MAAC]) applied on relevant polymeric materials (PM) used in the biomedical field. Electron microscopy revealed a smoother surface for the MAAC-treated PM compared to the reference, suggesting antiadhesive properties. The antibacterial activity was tested against selected Gram-positive and Gram-negative bacteria in accordance with ISO 22196. Bacterial growth was significantly reduced for the MAAC-treated PVC, plasticized PVC, polyurethane and silicone (90–99.999%) in which antibacterial activity of ≥1 log reduction was reached for all bacterial strains tested. Cytotoxicity was evaluated following ISO 10993-5 guidelines and L929 cell viability was calculated at ≥90% in the presence of MAAC. This study demonstrates that the MAAC could prevent bacterial contamination as demonstrated by the ISO 22196 tests, while further work needs to be done to improve the coating processability and effectiveness of more complex matrices.

Factors Involved in the onset of infection following bacterially contaminated platelet transfusions

Transfusion of platelet concentrates (PCs) is associated with several adverse patient reactions, the most common of which are febrile non-hemolytic transfusion reactions (FNHTRs) and transfusion-associated bacterial-infection/transfusion-associated sepsis (T-ABI/TA-S). Diagnosis of T-ABI/T-AS requires a positive blood culture (BC) result from the transfusion recipient and also a positive identification of bacterial contamination within a test aliquot of the transfused PC. In a significant number of cases, clinical symptoms post-transfusion are reported by the clinician, yet the BCs from the patient and/or PC are negative. The topic of 'missed bacterial detection' has therefore been the focus of several primary research studies and review articles, suggesting that biofilm formation in the blood bag and the presence of viable but non-culturable (VBNC) pathogens are the major causes of this missed detection. However, platelets are emerging as key players in early host responses to infection and as such, the aforementioned biofilm formation could elicit 'platelet priming', which could lead to significant immunological reactions in the host, in the absence of planktonic bacteria in the host bloodstream. This review reflects on what is known about missed detection and relates this to the emerging understanding of the effect of bacterial contamination on the platelets themselves and the significant role played by platelets in exacerbation of an immune response to infection within the transfusion setting.

The staphylococcal exopolysaccharide PIA - Biosynthesis and role in biofilm formation, colonization, and infection

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PIA is a key extracellular matrix component in staphylococci and other bacteria.

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PIA is a cationic, partially deacetylated N-acetylglucosamine polymer.

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PIA has a major role in bacterial biofilms and biofilm-associated infection.

Exopolysaccharide is a key part of the extracellular matrix that contributes to important mechanisms of bacterial pathogenicity, most notably biofilm formation and immune evasion. In the human pathogens Staphylococcus aureus and S. epidermidis, as well as in many other staphylococcal species, the only exopolysaccharide is polysaccharide intercellular adhesin (PIA), a cationic, partially deacetylated homopolymer of N-acetylglucosamine, whose biosynthetic machinery is encoded in the ica locus. PIA production is strongly dependent on environmental conditions and controlled by many regulatory systems. PIA contributes significantly to staphylococcal biofilm formation and immune evasion mechanisms, such as resistance to antimicrobial peptides and ingestion and killing by phagocytes, and presence of the ica genes is associated with infectivity. Due to its role in pathogenesis, PIA has raised considerable interest as a potential vaccine component or target.

Sepsis from an apheresis platelet contaminated with Acinetobacter calcoaceticus/baumannii complex bacteria and Staphylococcus saprophyticus after pathogen reduction

BACKGROUND

Strategies to reduce platelet (PLT) bacterial contamination include donor screening, skin disinfection, sample diversion, bacterial culture, pathogen reduction (PR), and day-of-transfusion tests. We report bacterial sepsis following a pathogen-reduced PLT transfusion.

CASE REPORT

An adult male with relapsed acute lymphoblastic leukemia was successfully treated for central catheter-associated Staphylococcus aureus bacteremia. A peripherally inserted central catheter (PICC) was placed. Chills, rigors, and flushing developed immediately after PICC-infused pathogen-reduced PLTs, progressing to septic shock requiring intensive care management.

METHODS

PICC and peripheral blood (PB), transfused bag saline flushes (TBFs), environmental samples, and the pathogen-reduced untransfused co-component (CC) were cultured. Plasma metagenomic and bacterial isolate whole-genome sequencing; PLT mitochondrial DNA (mtDNA) testing of untransfused CC and TBF; CC testing for amotosalen (S-59)/S-59 photoproducts; isolate PR studies (INTERCEPT); and TBF polymerase chain reaction for recipient Y-chromosome DNA were performed.

RESULTS

PB and PICC cultures grew Acinetobacter calcoaceticus/baumannii complex (ACBC). TBF was gram-positive; mass spectrometry identified ACBC and Staphylococcus saprophyticus (SS). CC Gram stain and cultures were negative. Environmental cultures, some done after decontamination, were ACBC/SS negative. Posttransfusion patient plasma and TBF ACBC sequences were genetically identical. No Y-chromosome signal was detected in TBF. S-59 photoproducts and evidence of mtDNA amplification inhibition were found in the CC. Spiking PR studies showed >5.9-log inactivation for both isolates. Donor skin cultures for Acinetobacter were negative.

CONCLUSION

CC sterility, PR studies, residual S-59 photoproducts, and mtDNA amplification inhibition suggest successful PR. Unidentified environmental sources and inherent or acquired bag defects may have contributed to postmanufacturing pathogen-reduced PLT contamination.

The comparative safety of bacterial risk control strategies for platelet components: a simulation study

BACKGROUND

Bacterial contamination of platelets is a problem that can lead to harmful septic transfusion reactions. The US Food and Drug Administration published a guidance in September 2019 detailing several permissible risk control strategies. Our objective was to compare the safety of each bacterial testing strategy for apheresis platelets.

STUDY DESIGN AND METHODS

We used simulation to compare safety of the nine risk control strategies involving apheresis platelet testing. The primary outcome was the risk of exposure. An exposure event occurred if a patient received platelets exceeding a specific contamination threshold (>0, 10³ , and 10⁵ colony-forming units (CFU/mL). We generated a range of bacterial contamination scenarios (inoculum size, doubling time, lag time) and compared risk of exposure for each policy in each contamination scenario. We then computed the average risk difference over all scenarios.

RESULTS

At the 0 CFU/mL exposure threshold, two-step policies that used secondary culture ranked best (all top three), while single-step 24-hour culture with 3-day expiration ranked last (ninth). This latter policy performed well (median rank of 1) at both the 10³ and 10⁵ CFU/mL thresholds, but 48-hour culture with 7-day expiration performed relatively poorly. At these higher thresholds, median ranks of two-step policies that used secondary culture were again top three. Two-step policies that used rapid testing improved at the higher (10⁵ CFU/mL) harm threshold, with median rankings between 1 and 5.

CONCLUSION

Two-step policies that used secondary culture were generally safer than single-step policies. Performance of two-step policies that used rapid testing depended on the CFU per milliter threshold of exposure used.

Sphingosine is able to prevent and eliminate Staphylococcus epidermidis biofilm formation on different orthopedic implant materials in vitro

Abstract

Periprosthetic infection (PPI) is a devastating complication in joint replacement surgery. On the background of an aging population, the number of joint replacements and associated complications is expected to increase. The capability for biofilm formation and the increasing resistance of different microbes to antibiotics have complicated the treatment of PPI, requiring the need for the development of alternative treatment options. The bactericidal effect of the naturally occurring amino alcohol sphingosine has already been reported. In our study, we demonstrate the antimicrobial efficacy of sphingosine on three different strains of biofilm producing Staphylococcus epidermidis, representing one of the most frequent microbes involved in PPI. In an in vitro analysis, sphingosine’s capability for prevention and treatment of biofilm-contamination on different common orthopedic implant surfaces was tested. Coating titanium implant samples with sphingosine not only prevented implant contamination but also revealed a significant reduction of biofilm formation on the implant surfaces by 99.942%. When testing the antimicrobial efficacy of sphingosine on sessile biofilm-grown Staphylococcus epidermidis, sphingosine solution was capable to eliminate 99.999% of the bacteria on the different implant surfaces, i.e., titanium, steel, and polymethylmethacrylate. This study provides evidence on the antimicrobial efficacy of sphingosine for both planktonic and sessile biofilm-grown Staphylococcus epidermidis on contaminated orthopedic implants. Sphingosine may provide an effective and cheap treatment option for prevention and reduction of infections in joint replacement surgery.

Key messages

• Here we established a novel technology for prevention of implant colonization by sphingosine-coating of orthopedic implant materials.

• Sphingosine-coating of orthopedic implants prevented bacterial colonization and significantly reduced biofilm formation on implant surfaces by 99.942%.

• Moreover, sphingosine solution was capable to eliminate 99.999% of sessile biofilm-grown Staphylococcus epidermidis on different orthopedic implant surfaces.

Long-term effects of cataract surgery with topical levofloxacin on ocular bacterial flora

PURPOSE

To clarify the long-term effect of topical antibiotics on the ocular bacterial flora after cataract surgery.

SETTING

Miyata Eye Hospital, Miyazaki, Japan.

DESIGN

Prospective case series.

METHODS

Patients who had cataract surgery between November 2014 and January 2015 were included. Levofloxacin 1.5% was administered 4 times a day by topical instillation from 3 days before surgery to 1 month postoperatively. The conjunctival sacs of patients were scraped before the procedure and 0, 3, 6, 9, and 12 months after the last instillation. The samples were cultured, and minimum inhibitory concentrations (MICs) of levofloxacin for Staphylococcus epidermidis and Propionibacterium acnes were evaluated using mixed-effects models.

RESULTS

The study evaluated 50 patients. Diverse bacterial species, predominantly S epidermidis and P acnes, were isolated before the application of topical levofloxacin. Bacterial diversity was substantially reduced after the final topical levofloxacin application and subsequently increased after 3 months. However, the geometric mean levofloxacin MICs for S epidermidis isolates were still significantly higher at 0 months and 3 months than before treatment (P < .01 and P = .03, respectively) and reached pretreatment levels 6 months and 12 months after the last application. Propionibacterium acnes did not show significant changes in the geometric mean levofloxacin MIC over time.

CONCLUSION

The restoration of the bacterial flora required more than 6 months after cataract surgery and topical levofloxacin.

The peptidoglycan and biofilm matrix of Staphylococcus epidermidis undergo structural changes when exposed to human platelets

Staphylococcus epidermidis is a bacterium frequently isolated from contaminated platelet concentrates (PCs), a blood product used to treat bleeding disorders in transfusion patients. PCs offer an accidental niche for colonization of S. epidermidis by forming biofilms and thus avoiding clearance by immune factors present in this milieu. Using biochemical and microscopy techniques, we investigated the structural changes of the peptidoglycan (PG) and the biofilm matrix of S. epidermidis biofilms formed in whole-blood derived PCs compared to biofilms grown in glucose-supplemented trypticase soy broth (TSBg). Both, the PG and the biofilm matrix are primary mechanisms of defense against environmental stress. Here we show that in PCs, the S. epidermidis biofilm matrix is mainly of a proteinaceous nature with extracellular DNA, in contrast to the predominant polysaccharide nature of the biofilm matrix formed in TSBg cultures. PG profile studies demonstrated that the PG of biofilm cells remodels during PC storage displaying fewer muropeptides variants than those observed in TSBg. The PG muropeptides contain two chemical modifications (amidation and O-acetylation) previously associated with resistance to antimicrobial agents by other staphylococci. Our study highlights two key structural features of S. epidermidis that are remodeled when exposed to human platelets and could be used as targets to reduce septic transfusions events.

Oral hygiene might prevent cancer

Many evidences support that species from the Human Oral Microbiome Database such as Fusobacterium nucleatum or Bacteroides, linked previously to periodontitis and appendicitis, play a role in colorectal cancer (CRC), including metastasis. These typically oral species are invasive anaerobes that form biofilms in their virulent state. Aspirin (a NSAID) has been recently included into routine CRC prevention rationale. NSAIDs can prevent the growth of neoplastic lesions by inhibiting COX enzymes and another set of recently identified COX-independent targets, which include the WNT, AMPK and MTOR signaling pathways, the crosstalk between nucleoli and NF-κB transcriptional activity in apoptosis, and the biochemistry of platelets. These are signaling pathways related to tumor-promoting inflammation. In this process, pathogens or simple deregulation of the microbiota play an important role in CRC. Aspirin and other NSAIDs are efficient inhibitors of biofilm formation and able to control periodontitis development preventing inflammation related to the microbiota of the gingival tissue, so its seems plausible to include this pathway in the mechanisms that aspirin uses to prevent CRC. We propose arguments suggesting that current oral hygiene methods and other future developments against periodontitis might prevent CRC and probably other cancers, alone or in combination with other options; and that the multidisciplinary studies needed to prove this hypothesis might be relevant for cancer prevention.

Development of Antifouling and Bactericidal Coatings for Platelet Storage Bags Using Dopamine Chemistry

Platelets have a limited shelf life, due to the risk of bacterial contamination and platelet quality loss. Most platelet storage bags are made of a mixture of polyvinyl chloride with a plasticizer, denoted as pPVC. To improve biocompatibility of pPVC with platelets and to inhibit bacterial biofilm formation, an antifouling polymer coating is developed using mussel-inspired chemistry. A copolymer of N,N-dimethylacrylamide and N-(3-aminopropyl)methacrylamide hydrochloride is synthesized and coupled with catechol groups, named DA51-cat. Under mild aqueous conditions, pPVC is first equilibrated with an anchoring polydopamine layer, followed by a DA51-cat layer. Measurements show this coating decreases fibrinogen adsorption to 5% of the control surfaces. One-step coating with DA51-cat does not coat pPVC efficiently although it is sufficient for coating silicon wafers and gold substrates. The dual layer coating on platelet bags resists bacterial biofilm formation and considerably decreases platelet adhesion. A cationic antimicrobial peptide, E6, is conjugated to DA51-cat then coated on silicon wafers and introduces bactericidal activity to these surfaces. Time-of-flight second ion-mass spectroscopy is successfully applied to characterize these surfaces. pPVC is widely used in medical devices; this method provides an approach to controlling biofouling and bacterial growth on it without elaborate surface modification procedures.

Comparative analysis between biofilm formation and gene expression in Staphylococcus epidermidis isolates

AIM

To understand the relationship between ica, aap and bhp gene expression and the implications in biofilm formation in selected clinical and commensal Staphylococcus epidermidis isolates.

MATERIAL & METHODS

Isolates were analyzed regarding their biofilm-forming capacity, biochemical matrix composition, biofilm spatial organization and expression of biofilm-related genes.

RESULTS

On polysaccharide intercellular adhesin-dependent biofilms, aap and bhp contributions for the biofilm growth were negligible, despite very high levels of expression. In contrast, smaller increases in icaA expression contributed significantly to biofilm growth. Interestingly, no biological differences were observed between clinical and commensal strains.

CONCLUSION

These results reinforce the concept that S. epidermidis is an 'accidental pathogen,' and that the ica operon is the main mechanism of biofilm formation in clinical and commensal isolates.

Bacterial contamination of platelet components not detected by BacT/ALERT®

OBJECTIVES

To investigate the possible causes for false negative results in BacT/ALERT^® 3D Signature System despite bacterial contamination of platelet units.

BACKGROUND

The Northern Ireland Blood Transfusion Service (NIBTS) routinely extends platelet component shelf life to 7 days. Components are sampled and screened for bacterial contamination using an automated microbial detection system, the BacT/ALERT^® 3D Signature System. We report on three platelet components with confirmed bacterial contamination, which represent false negative BacT/ALERT^® results and near-miss serious adverse events.

METHODS

NIBTS protocols for risk reduction of bacterial contamination of platelet components are described. The methodology for bacterial detection using BacT/ALERT^® is outlined. Laboratory tests, relevant patient details and relevant follow-up information are analysed.

RESULTS

In all three cases, Staphylococcus aureus was isolated from the platelet residue and confirmed on terminal sub-culture using BacT/ALERT^® . In two cases, S. aureus with similar genetic makeup was isolated from the donors.

CONCLUSION

Risk reduction measures for bacterial contamination of platelet components are not always effective. Automated bacterial culture detection does not eliminate the risk of bacterial contamination. Visual inspection of platelet components prior to release, issue and administration remains an important last line of defence.

Efficiency of riboflavin and ultraviolet light treatment against high levels of biofilm-derived Staphylococcus epidermidis in buffy coat platelet concentrates

BACKGROUND AND OBJECTIVES

Staphylococcus epidermidis forms surface-attached aggregates (biofilms) in platelet concentrates (PCs), which are linked to missed detection during PC screening. This study was aimed at evaluating the efficacy of riboflavin-UV treatment to inactivate S. epidermidis biofilms in buffy coat (BC) PCs.

MATERIALS AND METHODS

Biofilm and non-biofilm cells from S. epidermidis ST-10002 and S. epidermidis AZ-66 were individually inoculated into whole blood (WB) units (~10⁶ colony-forming units (CFU)/ml) (N = 4-5). One spiked and three unspiked WB units were processed to produce a BC-PC pool. Riboflavin was added to the pool which was then split into two bags: one for UV treatment and the second was untreated. Bacterial counts were determined before and after treatment. In vitro PC quality was assessed by flow cytometry and dynamic light scattering.

RESULTS

Bacterial counts were reduced during BC-PC production from ~10⁶ CFU/ml in WB to 10³ -10⁴ CFU/ml in PCs (P < 0·0001). Riboflavin-UV treatment resulted in significantly higher reduction of S. epidermidis AZ-66 than strain ST-10002 (≥3·5 log reduction and 2·6-2·8 log reduction, respectively, P < 0·0001). Remaining bacteria post-treatment were able to proliferate in PCs. No differences in S. epidermidis inactivation were observed in PCs produced from WB inoculated with biofilm or non-biofilm cells (P > 0·05). Platelet activation was enhanced in PCs produced with WB inoculated with biofilms compared to non-biofilm cells (P < 0·05).

CONCLUSION

Riboflavin-UV treatment was similarly efficacious in PCs produced from WB inoculated with S. epidermidis biofilm or non-biofilm cells. Levels of biofilm-derived S. epidermidis ≥10³ CFU/ml were not completely inactivated; however, further testing is necessary with lower (real-life) bacterial levels.

INVESTIGATION OF BIOFILM FORMATION IN COAGULASE-NEGATIVE STAPHYLOCOCCI ISOLATED FROM PLATELET CONCENTRATE BAGS

Platelet Concentrates (PCs) are the blood components with the highest rate of bacterial contamination, and coagulase-negative staphylococci (CoNS) are the most frequently isolated contaminants. This study investigated the biofilm formation of 16 contaminated units out of 691 PCs tested by phenotypic and genotypic methods. Adhesion in Borosilicate Tube (ABT) and Congo Red Agar (CRA) tests were used to assess the presence of biofilm. The presence of icaADC genes was assessed by means of the Polymerase Chain Reaction (PCR) technique. With Vitek(r)2, Staphylococcus haemolyticus was considered the most prevalent CoNS (31.25%). The CRA characterized 43.8% as probable biofilm producers, and for the ABT test, 37.5%. The icaADC genes were identified in seven samples by the PCR. The ABT technique showed 85.7% sensitivity and 100% specificity when compared to the reference method (PCR), and presented strong agreement (k = 0.8). This study shows that species identified as PCs contaminants are considered inhabitants of the normal skin flora and they might become important pathogens. The results also lead to the recommendation of ABT use in laboratory routine for detecting biofilm in CoNS contaminants of PCs.