The Interactions Between Bacteria, Platelets Bags and Platelets

Bacterial contamination of blood products is a major risk in transfusion medicine, with bacterial attachment and biofilm formation a potential source for false negative results of bacterial platelet contamination. Understanding platelet bag (PB) surface properties could improve understanding of how bacteria adhere to these surfaces. PB surfaces were analysed using scanning electron microscopy, optical surface profiling, Fourier transform infrared spectroscopy, RAMAN spectroscopy, goniometry, energy dispersive X-ray and a tensiometer. Initial findings demonstrated that the PBs had two distinct surfaces, a rough diamond patterned surface and a smoother surface. Two surface altering methods were used; PBs surfaces were flattened to remove surface features, which can increase bacterial attachment, and treated with low temperature atmospheric pressure plasma, with flattening demonstrating surface feature changes and plasma treatment being unsuitable. Staphylococcus epidermidis and Serratia marcescens biofilms grown on the surfaces demonstrated reduced biomass formation on the flattened surface after 5 days. Conditioning films on the surfaces of the bacteria, human plasma and human plasma combined with one of the bacteria demonstrated that the human plasma alone altered the surface properties the most, especially the roughness, surface chemistry and surface physicochemistry. When human plasma was combined with bacteria, changes were also determined but differed to when human plasma was tested alone. Finally, testing the effects of bacteria on platelets demonstrated that planktonic bacteria had little effect on platelet activation and viability, whilst biofilms halved platelet aggregation but did not affect activation. Western blots demonstrated that protein expression could be affected, particularly by biofilms. Further, release of RANTES by the platelets was doubled when incubated with bacterial biofilms. The results demonstrated the significance surface properties had on bacterial attachment and biofilm formation as well as how conditioning films altered the surface properties and how biofilms were able to affect platelets

Non-chlorine detergent formulations as an alternative for unpasteurised milk removal from stainless steel surfaces

Hygiene is a major concern in the dairy industry, and detergents based on hypochlorite have commonly been utilised for cleaning-in-place (CIP) regimes. However, due to concerns about chlorate residues entering the milk processing chain, new detergent alternatives that are free of chlorate sources are required. Two new formulations were developed based on ethylenediaminetetraacetic acid (EDTA) and wetting agents. Stainless steel surfaces were fouled with milk and cleaned once or 10 times using water, a caustic-EDTA product, a sodium hypochlorite product, an acid, or new cleaning formulations (Product A and Product B). The results demonstrated that the use of acid did not result in successful cleaning. The two new products performed well, with Product B performing equivalently during cleaning compared with the established hypochlorite or caustic-EDTA products. Product A exhibited better cleanliness than the other detergents tested. When allergen removal was considered, residual material was found to be retained on the surfaces, regardless of the cleaning type used. This study suggests that the new product formulations may be used to replace hypochlorite-based detergents to increase the hygienic status of a surface

The effect of the surface properties of poly(methyl methacrylate) on the attachment, adhesion and retention of fungal conidia

Poly(methyl methacrylate) (PMMA) surfaces, (commercial PMMA (PMMAc), spin coated PMMA (PMMAsc) and a 90% methylmethacrylate/10% 3-methacryloxypropyltrimethoxysilane random copolymer (P(MMA-co-gMPS)) were used to determine the effect of surface properties on conidia biofouling. The contact angles of the substrates demonstrated that the PMMAsc and the P(MMA-co-gMPS) polymer (62.8°) were more wettable than the PMMAc surface (71.0°). The PMMAsc had the greatest roughness value (32.0 nm) followed by the PMMAc (3.0 nm), then P(MMA-co-gMPS) (1 nm). Aspergillus niger 1957 conidia were spherical, smooth and hydrophobic (12.1%). Aspergillus niger 1988 conidia were spherical with spikes and hydrophobic (17.1%). Aureobasidium pullulans was elliptical with longitudinal ridges and hydrophilic (79.9%). Following attachment assays, cPMMA attached the greatest numbers of conidia. Following the adhesion and retention assays (washing step included in the protocol), A. niger 1957 and A. niger 1988 were least adhered to the P(MMA-co-gMPS) surface, whilst A. pulluans was least adhered to the PMMAsc surface. This work demonstrated that in the absence of a washing step, only the surface properties influenced the conidia attachment, whilst in the presence of a washing step, both the properties of the surfaces and the conidia affected conidia adhesion and retention. Hence, the methodology used (with or without a washing step) should reflect the environment in which the surface is to be applied

Molybdenum Disulphide Surfaces to Reduce Staphylococcus aureus and Pseudomonas aeruginosa Biofilm Formation.

The reduction of bacteria and biofilm formation is important when designing surfaces for use in industry. Molybdenum disulphide surfaces (MoS2SUR) were produced using MoS2 particle (MoS2PAR) sizes of 90 nm 2 µm and 6 µm containing MoS2PAR concentrations of 5%, 10%, 15% and 20%. These were tested to determine the efficacy of the MoS2SUR to impede bacterial retention and biofilm formation of two different types of bacteria, Staphylococcus aureus and Pseudomonas aeruginosa. The MoS2SUR were characterised using Fourier Transform InfraRed Spectroscopy, Ion Coupled Plasma Atomic Emission Spectroscopy, Scanning Electron Microscopy, Optical Profilometry and Water Contact Angles. The MoS2SUR made with the smaller 90 nm MoS2PAR sizes demonstrated smaller topographical shaped features. As the size of the incorporated MoS2PAR increased, the MoS2SUR demonstrated wider surface features, and they were less wettable. The increase in MoS2PAR concentration within the MoS2SUR groups did not affect the surface topography but did increase wettability. However, the increase in MoS2PAR size increased both the surface topography and wettability. The MoS2SUR with the smaller topographical shaped features, influenced the retention of the S. aureus bacteria. Increased MoS2SUR topography and wettability resulted in the greatest reduction in bacterial retention and the bacteria became more heterogeneously dispersed and less clustered across the surfaces. The surfaces that exhibited decreased bacterial retention (largest particle sizes, largest features, greatest roughness, most wettable) resulted in decreased biofilm formation. Cytotoxicity testing of the surface using cell viability demonstrated that the MoS2SUR were not toxic against HK-2 cells at MoS2PAR sizes of 90 nm and 2 µm. This work demonstrated that individual surfaces variables (MoS2SUR topographic shape and roughness, MoS2PAR size and concentration) decreased bacterial loading on the surfaces, which then decreased biofilm formation. By optimising MoS2SUR properties, it was possible to impede bacterial retention and subsequent biofilm formation

The Effect of Human Blood Plasma Conditioning Films on Platelet Transfusion Bag Surface Properties

Transfusion-associated bacterial infections continue to occur which may be due to the formation of bacterial biofilms on the inner surface of the blood bag. Plasticized poly (vinyl chloride) (p-PVC) platelet storage bags in three surface roughness states (rough, smooth and flattened) were used to determine the effect that a conditioning film (CF) of human plasma had on surface properties and its interaction with Staphylococcus epidermidis and Serratia marcescens. SEM and optical profilometry determined changes in surface roughness, whilst EDX and ATR-FTIR determined surface chemistry. The physicochemistry of the surfaces and bacteria was assessed using contact angle measurements and MATH assays respectively. When applied to a rougher surface, the CF reduced the surface topography, masked certain surface chemistry features and made the surfaces more hydrophilic. The CF reduced the adhesion of the bacteria to most of the hydrocarbons. When human plasma was combined with bacteria, most of the physicochemical properties changed similarly to those of human plasma alone, with the most significant changes observed after 24 h especially with Ser. marcescens. The results demonstrated that the presence of human plasma had a significant effect on the surface properties of the platelet bags and also on microbial interactions with the bag surface

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

Multifractal Analysis to Determine the Effect of Surface Topography on the Distribution, Density, Dispersion and Clustering of Differently Organised Coccal-Shaped Bacteria

The topographic features of surfaces are known to affect bacterial retention on a surface, but the precise mechanisms of this phenomenon are little understood. Four coccal-shaped bacteria, Staphylococcus sciuri, Streptococcus pyogenes, Micrococcus luteus, and Staphylococcus aureus, that organise in different cellular groupings (grape-like clusters, tetrad-arranging clusters, short chains, and diploid arrangement, respectively) were used. These differently grouped cells were used to determine how surface topography affected their distribution, density, dispersion, and clustering when retained on titanium surfaces with defined topographies. Titanium-coated surfaces that were smooth and had grooved features of 1.02 µm-wide, 0.21 µm-deep grooves, and 0.59 µm-wide, 0.17 µm-deep grooves were used. The average contact angle of the surfaces was 91°. All bacterial species were overall of a hydrophobic nature, although M. luteus was the least hydrophobic. It was demonstrated that the 1.02 µm-wide featured surface most affected Strep. pyogenes and S. sciuri, and hence the surfaces with the larger surface features most affected the cells with smaller dimensions. The 0.59 µm featured surface only affected the density of the bacteria, and it may be suggested that the surfaces with the smaller features reduced bacterial retention. These results demonstrate that the size of the topographical surface features affect the distribution, density, dispersion, and clustering of bacteria across surfaces, and this is related to the cellular organisation of the bacterial species. The results from this work inform how surface topographical and bacterial properties affect the distribution, density, dispersion, and clustering of bacterial retention