Sponge Whirl-Pak Sampling Method and Droplet Digital RT-PCR Assay for Monitoring of SARS-CoV-2 on Surfaces in Public and Working Environments

The SARS-CoV-2 can spread directly via saliva, respiratory aerosols and droplets, and indirectly by contact through contaminated objects and/or surfaces and by air. In the context of COVID-19 fomites can be an important vehicle of virus transmission and contribute to infection risk in public environments. The aim of the study was to analyze through surface sampling (sponge method) the presence of SARS-CoV-2 in public and working environments, in order to evaluate the risk for virus transmission. Seventy-seven environmental samples were taken using sterile sponges in 17 animal farms, 4 public transport buses, 1 supermarket and 1 hotel receptive structure. Furthermore, 246 and 93 swab samples were taken in the farms from animals and from workers, respectively. SARS-CoV-2 detection was conducted by real-time RT-PCR and by digital droplet RT-PCR (dd RT-PCR) using RdRp, gene E and gene N as targets. None of the human and animal swab samples were positive for SARS-CoV-2, while detection was achieved in 20 of the 77 sponge samples (26%) using dd RT-PCR. Traces of the RdRp gene, gene E and gene N were found in 17/77 samples (22%, average concentration 31.2 g.c./cm², range 5.6 to 132 g.c./cm²), 8/77 samples (10%, average concentration 15.1 g.c./cm², range 6 to 36 g.c./cm²), and in 1/77 (1%, concentration 7.2 g.c./cm²). Higher detection rates were associated with sampling in animal farms and on public transport buses (32% and 30%) compared to the supermarket (21%) and the hotel (no detection). The result of the study suggests that the risk of contamination of surfaces with SARS-CoV-2 increases in environments in which sanitation strategies are not suitable and/or in highly frequented locations, such as public transportation. Considering the analytical methods, the dd RT-PCR was the only approach achieving detection of SARS-CoV-2 traces in environmental samples. Thus, dd RT-PCR emerges as a reliable tool for sensitive SARS-CoV-2 detection.

Loss of microvascular negative charges accompanied by interstitial edema in septic rats' heart

We studied the effect of Gram-negative sepsis on negative charges of heart capillaries and myocardial cells. We used a rat model of multiorgan failure, with ruthenium red (RR) and polyethyleneimine (PEI) as cationic binding tracers. Twenty-four hours after induction of sepsis, negative charges had decreased in glycocalyx and basement membrane of myocardial capillary endothelial cells. There were substantial amounts of interstitial edema. Density of anionic charges in the sarcolemmal glycocalyx complex of cardiac cells was markedly reduced. Myocardial cells' mitochondria consistently showed morphologic changes, whose severity ranged between stages II and IV C of Trump. Thirteen days after induction of sepsis, capillary endothelial and myocardial cells had recovered almost completely and showed no intracellular edema. Gram-negative sepsis caused a significant reduction in negative charges normally present in the microvascular wall as well as on myocardial cells. Consequently, several membranes limiting the various compartments of heart tissue lost their structural integrity. This morphometric data could explain the development of protein-rich interstitial edema and defective cell volume regulation observed in cardiac muscle of endotoxin-shocked animals. This myocardial edema may be at the origin of the cardiac dysfunction observed in both experimental and human septic shock.

Protamine sulfate induces enhanced peritoneal permeability to proteins

We present a direct link between the neutralization of anionic sites by intraperitoneal protamine and a rise in protein passage to the peritoneal cavity during isosmotic peritoneal dialysis in rabbits. Each experiment included two 1-hour exchanges. No drugs were added in the first exchange. In group A (control) there were no drugs in the second hour either. In group B, protamine (50 micrograms/ml) was added to the second exchange volume. In group C, protamine and heparin (50 U/ml) were added. In groups A and C, appearance curves of metabolites during the first (baseline) and the second (experimental) hours were not statistically different. In group B, differences for urea, glucose and uric acid were not significant, but they were highly so for protein (increase of 100%, p less than 0.01). Transperitoneal passage of albumin is substantially enhanced by protamine. Neutralization of protamine with heparin prevents this, showing that availability of anionic sites is the crucial limiting factor. Protamine did not significantly affect the transfer of small neutral molecules.

Anionic fixed charges in the fenestrated capillaries of the mouse mesentery

Previous studies showed the existence of submesothelial fenestrated capillaries in the human parietal and rabbit diaphragmatic peritoneum, as well as in the mouse mesentery. The present study demonstrates the presence of electronegative fixed charges at the luminal aspect of endothelial cells, as well as long the subendothelial basement membrane of the fenestrated capillaries of the mouse mesentery. This situation will eventually preclude the transfenestral passage of anionic plasma proteins. On the other hand, fenestrated capillaries are much more permeable to water and small-molecular-size solutes than those of the continuous type. Therefore, the high hydraulic conductivity of fenestrae may well imply that a substantial part of water and small solutes leave the blood compartment through the fenestral channels.

Decreased density distribution of mesenteric and diaphragmatic microvascular anionic charges during murine abdominal sepsis

Pulmonary edema of sepsis is a consequence of increased transmural conductance for water and proteins at the level of lung microvessels induced by vasoactive endogenous mediators, liberated after activation of complement by bacterial endotoxins. Intermittent opening of interendothelial junctions at the level of post-capillary venules has been implicated as being the pathway for the leaking plasma proteins and water. Microvascular basement membranes and endothelial cell surfaces have fixed anionic charges (AS) which prevent the escape of plasma proteins from the circulation as well as the adhesion of blood cells to the luminal endothelium. The density distribution of these AS was substantially reduced in visceral and systemic microvessels during murine abdominal sepsis. This observation suggest that MOF secondary to sepsis is the consequence of a severe and generalized alteration of the microvascular electronegative charge, induced by liberation of inflammatory mediators.