Impact of SARS-CoV-2 pandemic among health care workers in a secondary teaching hospital in Spain

BACKGROUND

The COVID-19 pandemic has posed a huge challenge to healthcare systems and their personnel worldwide. The study of the impact of SARS-CoV-2 infection among healthcare workers (HCW), through prevalence studies, will let us know viral expansion, individuals at most risk and the most exposed areas in healthcare organizations. The aim of this study is to gauge the impact of SARS-CoV-2 pandemic in our hospital workforce and identify groups and areas at increased risk.

METHODS AND FINDINGS

This is a cross-sectional and incidence study carried out on healthcare workers based on molecular and serological diagnosis of SARS-CoV-2 infection. Of the 3013 HCW invited to participate, 2439 (80.9%) were recruited, including 674 (22.4%) who had previously consulted at the Occupational Health Service (OHS) for confirmed exposure and/or presenting symptoms suggestive of COVID-19. A total of 411 (16.9%) and 264 (10.8%) healthcare workers were SARS-CoV-2 IgG and rRT-PCR positive, respectively. The cumulative prevalence considering all studies (IgG positive HCW and/or rRT-PCR positive detection) was 485 (19.9%). SARS-CoV-2 IgG-positive patients in whom the virus was not detected were 221 (9.1%); up to 151 of them (68.3%) did not report any compatible symptoms nor consult at the OHS for this reason. Men became more infected than women (25% vs 18.5%, p = 0.0009), including when data were also classified by age. COVID-19 cumulative prevalence among the HCW assigned to medical departments was higher (25.2%) than others, as well as among medical staff (25.4%) compared with other professional categories (p<0.01).

CONCLUSIONS

The global impact of the COVID-19 pandemic on HCW of our centre has been 19.9%. Doctors and medical services personnel have had the highest prevalence of SARS-CoV-2 infection, but many of them have not presented compatible symptoms. This emphasizes the performance of continuous surveillance methods of the most exposed health personnel and not only based on the appearance of symptoms.

A Model for Fluid Secretion in Rhodnius Upper Malpighian Tubules (UMT)

We have measured fluid secretion rate in Rhodnius prolixus upper Malpighian tubules (UMT) stimulated to secrete with 5-OH-tryptamine. We used double perfusions in order to have access separately to the basolateral and to the apical cell membranes. Thirteen pharmacological agents were applied: ouabain, Bafilomycin A(1), furosemide, bumetanide, DIOA, Probenecid, SITS, acetazolamide, amiloride, DPC, BaCl(2), pCMBS and DTT. These agents are known to block different ion transport functions, namely ATPases, co- and/or counter-transporters and ion and water channels. The basic assumption is that water movement changes reflect changes in ion transport mechanisms, which we localize as follows: (i) At the basolateral cell membrane, fundamental are a Na(+)-K(+)-2Cl(-) cotransporter and a Cl(-)-HCO(3) (-) exchanger; of intermediate importance are the Na(+)-K(+)-ATPase, Cl(-) channels and Rp-MIP water channels; K(+) channels play a lesser role: (ii) At the apical cell membrane, most important are a K(+)-Cl(-) cotransport that is being located for the first time, a V-H(+)-ATPase; and a Na(+)-H(+) exchanger; a urate-anion exchanger and K(+) channels are less important, while Cl(-) channels are not important at all. A tentative model for the function of the UMT cell is presented.

Fluid secretion in Rhodnius upper malpighian tubules (UMT): water osmotic permeabilities and morphometric studies

We have measured the osmotic permeability of the basolateral cell membrane (Poscb) and compared it with the transepithelial permeability (Poste) to calculate the paracellular (Posp) permeability of the upper malpighian tubules (UMT) of the 5th instar of Rhodnius prolixus under several experimental conditions, namely, at rest and after stimulation to secrete with 5-HT, each under control conditions (no treatment), after treatment with pCMBS, and after addition of pCMBS and DTT. Secretion rate is negligible at rest. During stimulation mean secretion rate is 43.5 nl/cm2 sec. Secretion is severely curtailed by pCMBS and fully restored by DTT. Poscb = 9.4 (resting, control); 5.8 (control + pCMBS); 10.7 (control + pCMBS + DTT); 20.6 (stimulated, control); 14.7 (stimulated + pCMBS); 49.1 (stimulated + pCMBS + DTT) (x10?4 cm3/cm2 sec Osm). Calculated Posp are higher than the transcellular permeability, Posc, at rest and after stimulation. Electron micrograph morphometry of UMT sections show that cells significantly decrease their volume after stimulation. Lateral intercellular space (LIS) and basolateral extracellular labyrinth (BEL) are barely discernible at rest. LIS and BEL are widely dilated in stimulated UMT. Thus, ions have restricted access to the deep and narrow basolateral cell membrane indentations at rest, but they have ready access to cell membrane indentations after stimulation, because of the opening of LIS and BEL. These findings are discussed in relation to isosmotic secretion. The rate-limiting step for paracellular movement is located at the smooth septate junctions.

Update on the detection of beta-exotoxin in Bacillus thuringiensis strains by HPLC analysis

AIMS

The current work aimed to study the presence of beta-exotoxin by high-performance liquid chromatography (HPLC) in supernatant fluids from final whole cultures of the 69 type strains and 13 subtypes of Bacillus thuringiensis strains, as well as from some insecticidal strains.

METHODS AND RESULTS

Results from HPLC and bioassays with Ephestia kuhniella (Lepidoptera Pyralidae) were compared. Type I beta-exotoxin was only detected in type strains representing serotypes H1, H9 and H10a,10b. Discrepancies between HPLC and bioassays were found in H8a,8b and some insecticidal strains, which suggests the occurrence of another soluble toxin different from type I beta-exotoxin, possibly type II beta-exotoxin.

CONCLUSION

This study shows the need to use bioassays to determine the presence of beta-exotoxin activity. However, HPLC is a fast and sensitive technique if only type I beta-exotoxin is to be determined. The occurrence of beta-exotoxin in a type strain does not imply production of this metabolite by other strains belonging to the same serovar.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results complete the characterization of type strains belonging to the International Entomopathogenic Bacillus Collection (Institut Pasteur, Paris, France).

Identification of a new water channel (Rp-MIP) in the Malpighian tubules of the insect Rhodnius prolixus

Malpighian tubules (MT) of Rhodnius prolixus transport fluid at very high rates. To identify whether aquaporins (AQPs) are present in the MT of R. prolixus, total ribonucleic acid (RNA) was isolated from MT and used in a reverse transcription, polymerase chain reaction (RT-PCR), with two degenerate primers to highly conserved regions of the members of the AQPs family. A deoxyribonucleic acid (DNA) fragment of 370 bp was amplified; its sequence revealed a novel protein, representing a new member of the major intrinsic protein (MIP) family. The complementary DNA (cDNA) sequence of this new MIP protein was cloned by using RNA from MT and the rapid amplification of cDNA ends (RACE) technique. The cDNA had 1133 bp and the largest open reading frame coded for a protein of 286 amino acids, named R. prolixus major intrinsic protein (Rp-MIP). The hydrophobicity profile of the amino acid sequence predicts six transmembrane domains. Northern blot analysis of MT RNA showed a single transcript of about 1-1.3 kb for Rp-MIP. RT-PCR of single isolated MT and in situ hybridization analysis showed Rp-MIP transcripts in both proximal and distal segments. Expression of Rp-MIP in Xenopus laevis oocytes doubled the osmotic water permeability Pf, indicating that Rp-MIP may function as an aquaporin protein in the MT of the insect and thus may participate in urine formation in R. prolixus.

Identification of psi3Tom20, a novel processed pseudogene of the human Tom20 gene, and complete characterization of psi1Tom20 and psi2Tom20

We report the identification and characterization of psi3Tom20, a novel processed pseudogene of the human Tom20 (hTom20) gene, which is 96.2% similarity with the hTom20 cDNA and is 5' and 3' truncated. In addition, we present the complete characterization of psi2Tom20 and psi2Tom20, the two other recently reported members of this pseudogene family. Comparison of the sequences of psi3Tom20 with that of the previously reported psi2Tom20 revealed and corrected an error in the previously determined sequence of psi2Tom20. A detailed analysis of these three pseudogenes, including their flanking regions, is presented. It suggests they probably arose from mRNAs that were polyadenylated at different sites. Possible mechanisms involved in their integration as retroposons are also discussed.

Length of the selectivity filter of aquaporin-1

We have characterized the selectivity filter of the water channel aquaporin-1 (AQP1) of proximal straight tubules (PST), as an equivalent cylindrical structure with a diameter of approximately 4.5 A, where water molecules single file. We report here efforts to evaluate its length. PST were dissected from rabbit kidneys, held with pipettes in a chamber bathed in a buffered mannitol isosmotic solution (MBS, 295 mOsm/kg). Changes in tubule cell volume with time (dV/Adt), were monitored, on line, with an inverted microscope, a TV camera and an image processor. Osmotic permeability coefficients, Pos, and reflection coefficients (sigma s) were measured with several solutes: mannitol (M), raffinose (R), sucrose (S), glycerol (G), acetamide (A) and urea (U). For this purpose PST were suddenly exposed (in approximately 80 ms and for 20 s) to a hyperosmolality step (delta Cs) achieved by adding to MBS a delta Cs of 35 mOsm/kg of either R, S, M, G, A or U. Cells shrunk within 500 ms of t = 0 to their osmometric volume and remained shrunk for the 20 s of the delta Cs. Pos was measured from the shrinking curves; Pos = 3000 +/- 25 microns/s with either R, S, M, G, A or U. This procedure also allowed to calculate sigma s; sigma s = 1.00 for R, S, M, G, A and U, indicating that these solutes do not penetrate the water channel. In contrast, the shrinking curves produced by a delta Cs = 35 mOsm/kg formamide (F) were 1/5th to 1/6th slower and smaller (subosmometric) than those produced by a delta Cs = 35 mOsm/kg of R, S, M, G, A or U. Furthermore, with F, cells did not remain shrunk. They recovered their original volume within 3 s. Pos (measured with F) is denoted as Pos*; Pos* = 480 +/- 30 microns/s. sigma s, formamide (denoted sigma sp) = 0.16 +/- 0.01. Use of sigma sp and Pos* values in Hill's equations for the bimodal theory of osmosis leads to n = 2-3, n being the number of water molecules single filing within the channel selectivity filter, whose length must lie within 6 to 9 A, a value lower than previous values calculated from the Pos/Pd* ratio.

Transport of water in proximal kidney tubules from whole tubules to single channels: length and section of the selectivity filter of aquaporin-1

Proximal straight tubule (PST) were dissected from rabbit kidneys, held with crimping pipettes in a chamber bathed in a buffered mannitol isosmotic solution (MBS, 295 mOsm/kg). Tubule cell volume changes with time (dV/Adt) after steps in MBS osmolality (delta Cs) were monitored on line with an inverted microscope, a TV camera and an image processor. Reflection coefficients sigma and osmotic permeability coefficients, Pos, for several solutes were measured using two methods. Method 1: sigma was calculated from the delta Csiso of impermeant and permeant solutes at which (dV/Adt)t-->0 = 0 (i.e., by a null point method). It is denoted as sigma 1. sigma 1 = 1.00 for mannitol (M), raffinose (R), sucrose (S), glycerol (G), acetamide (A) and urea (U). With formamide (F), sigma 1, Formamide = 0.62 +/- 0.05. These findings confirm our previous value of dp = 4.5 A for the diameter of the selectivity filter of the basolateral PST cell membrane water channel AQP1. Method 2: PST were exposed for 20 s to MBS made hyperosmotic by addition of a delta Cs of 35 mOsm/kg of R, S, M, G, A and U. Cells shrunk within 500 ms of t = 0 to their osmometric volume and remained shrunk for the 20 s of the osmotic challenge. Pos was measured from the shrinking curves. P(os) = 3000 +/- 25 microns/s with R, S, M, G, A and U. Method 2 also allowed to calculate sigma, denoted as sigma 2. sigma 2 = 1.00 for R, S, M, G, A and U. By contrast, the shrinking curve produced by a delta Cs of 35 mOsm/kg F was 1/5th to 1/6th slower and smaller (i.e., subosmometric) than that produced by a delta Cs of 35 mOsm/kg R, S, M, G, A and U. Furthermore, with F cells did not remain shrunk but recovered their original volume within 3 s. P(os) (measured with F) is denoted as P(os)*, P(os)* = 480 +/- 30 microns/s. sigma 2, Formamide = 0.16 +/- 0.01. Use of sigma 1, sigma 2 and P(os)* values in Hill's equations for the bimodal theory of osmosis leads to n = 2-9. Where n is the number of water molecules single filling within the channel selectivity filter, whose length must lie within 6 to 27 A, a value significantly lower than our previous value calculated from the P(os)/Pd* ratio.

The proximal straight tubule (PST) basolateral cell membrane water channel: selectivity characteristics

Proximal straight tubules (PST) were dissected from rabbit kidneys, held by crimping pipettes in a chamber and bathed in a buffered isosmotic (295 mOsm/kg) solution containing 200 mM mannitol (MBS). Changes in tubule diameter were monitored on line with an inverted microscope, TV camera and image processor. The PST were then challenged for 20 sec with MBS made 35 mOsm/kg hyperosmotic by addition of either NaCl, KCl, mannitol (M), glycerol (G), ethylene glycol (E), glycine (g), urea (U), acetamide (A) or formamide (F). With NaCl, KCl, M, G, E, g, U, and A, tubules shrunk osmometrically within 0.5 sec and remained shrunk for as long as 20 sec without recovering their original volume (sometimes A showed some recovery). PST barely shrunk with F and quickly recovered their original volume. The permeability coefficients were 0 microns/sec (NaCl, M, g, E and U), 1 micron/sec (A), 84 microns/sec (F) and 0.02 micron/sec (G). The reflection coefficients sigma = 1.0 (NaCl, KCl, M, G, E, g and U), 0.95 (A) and 0.62 (F). Similar sigma values were obtained by substituting 200 mOsm/kg M in MBS by either NaCl, KCl, G, E, g, U, a or F. The olive oil/water partition coefficients are 5 (M), 15 (U), 85 (A) and 75 (F) (all x 10(-5)). Thus, part of F permeates the cell membrane through the lipid bilayer. The probing molecules van der Waals diameters are 7.4 x 8.2 x 12.0 (M), 3.6 x 5.2 x 5.4 (U), 3.8 x 5.2 x 5.4 (A) and (3.4 x 4.5 x 5.4 (F) A.(ABSTRACT TRUNCATED AT 250 WORDS)