Personal protective equipment use among dental healthcare personnel during the coronavirus disease 2019 (COVID-19) pandemic and the impact of an educational video in clinical practice

OBJECTIVE

Dental healthcare personnel (DHCP) are at high risk of exposure to coronavirus disease 2019 (COVID-19). We sought to identify how DHCP changed their use of personal protective equipment (PPE) as a result of the COVID-19 pandemic, and to pilot an educational video designed to improve knowledge of proper PPE use.

DESIGN

The study comprised 2 sets of semistructured qualitative interviews.

SETTING

The study was conducted in 8 dental clinics in a Midwestern metropolitan area.

PARTICIPANTS

In total, 70 DHCP participated in the first set of interviews; 63 DHCP participated in the second set of interviews.

METHODS

In September-November 2020 and March-October 2021, we conducted 2 sets of semistructured interviews: (1) PPE use in the dental community during COVID-19, and (2) feedback on the utility of an educational donning and doffing video.

RESULTS

Overall, 86% of DHCP reported having prior training. DHCP increased the use of PPE during COVID-19, specifically N95 respirators and face shields. DHCP reported real-world challenges to applying infection control methods, often resulting in PPE modification and reuse. DHCP reported double masking and sterilization methods to extend N95 respirator use. Additional challenges to PPE included shortages, comfort or discomfort, and compatibility with specialty dental equipment. DHCP found the educational video helpful and relevant to clinical practice. Fewer than half of DHCP reported exposure to a similar video.

CONCLUSIONS

DHCP experienced significant challenges related to PPE access and routine use in dental clinics during the COVID-19 pandemic. An educational video improved awareness and uptake of appropriate PPE use among DHCP.

Assessment of dental health care personnel protocol deviations and self-contamination during personal protective equipment donning and doffing

Background

Dental health care personnel (DHCP) may be at increased risk of exposure to severe acute respiratory syndrome coronavirus 2, the virus that causes COVID-19, as well as other clinically important pathogens. Proper use of personal protective equipment (PPE) reduces occupational exposure to pathogens. The authors performed an assessment of PPE donning and doffing practices among DHCP, using a fluorescent marker as a surrogate for pathogen transmission.

Methods

Participants donned PPE (that is, disposable gown, gloves, face mask, and eye protection) and the fluorescent marker was applied to their palms and abdomen. DHCP then doffed PPE according to their usual practices. The donning and doffing processes were video recorded, areas of fluorescence were noted, and protocol deviations were assessed. Statistical analyses included frequency, type, and descriptions of protocol deviations and factors associated with fluorescence.

Results

Seventy DHCP were enrolled. The donning and doffing steps with the highest frequency of protocol deviations were hand hygiene (66% of donning and 78% of doffing observations involved a deviation) and disposable gown use (63% of donning and 60% of doffing observations involved a deviation). Fluorescence was detected on 69% of DHCP after doffing, most frequently on hands. An increasing number of protocol deviations was significantly associated with increased risk of fluorescence. DHCP with a gown doffing deviation, excluding doffing out of order, were more likely to have fluorescence detected.

Conclusions

DHCP self-contamination was common with both donning and doffing PPE.

Practical Implications

Proper use of PPE is an important component of occupational health.

Isolation of SARS-CoV-2 in Viral Cell Culture in Immunocompromised Patients With Persistently Positive RT-PCR Results

Immunocompromised adults can have prolonged acute respiratory syndrome coronavirus 2 (SARS-CoV-2) positive RT-PCR results, long after the initial diagnosis of coronavirus disease 2019 (COVID-19). This study aimed to determine if SARS-CoV-2 virus can be recovered in viral cell culture from immunocompromised adults with persistently positive SARS-CoV-2 RT-PCR tests. We obtained 20 remnant SARS-CoV-2 PCR positive nasopharyngeal swabs from 20 immunocompromised adults with a positive RT-PCR test ≥14 days after the initial positive test. The patients' 2nd test samples underwent SARS-CoV-2 antigen testing, and culture with Vero-hACE2-TMPRSS2 cells. Viral RNA and cultivable virus were recovered from the cultured cells after qRT-PCR and plaque assays. Of 20 patients, 10 (50%) had a solid organ transplant and 5 (25%) had a hematologic malignancy. For most patients, RT-PCR Ct values increased over time. There were 2 patients with positive viral cell cultures; one patient had chronic lymphocytic leukemia treated with venetoclax and obinutuzumab who had a low viral titer of 27 PFU/mL. The second patient had marginal zone lymphoma treated with bendamustine and rituximab who had a high viral titer of 2 x 106 PFU/mL. Most samples collected ≥7 days after an initial positive SARS-CoV-2 RT-PCR had negative viral cell cultures. The 2 patients with positive viral cell cultures had hematologic malignancies treated with chemotherapy and B cell depleting therapy. One patient had a high concentration titer of cultivable virus. Further data are needed to determine risk factors for persistent viral shedding and methods to prevent SARS-CoV-2 transmission from immunocompromised hosts.

354. SARS-CoV-2 Viral Viability Culture and Sequencing from Immunocompromised Patients with Persistently Positive SARS-CoV-2 PCR Results

Background

Immunocompromised (IC) patients (pts) can have prolonged SARS-CoV-2 PCR positivity, even after resolution of COVID-19 symptoms. This study aimed to determine if viable virus could be detected in samples collected > 21 days after an initial positive (pos) SARS-CoV-2 PCR in IC pts.

Methods

We obtained 20 remnant SARS-CoV-2 PCR pos nasopharyngeal swabs from IC pts (bone marrow or solid organ transplant, high dose steroids, immunosuppressive medications) with a pos repeat PCR within the previous 30 days. The repeat specimens were cultured on Vero-hACE2-TMPRSS2 cells and incubated for 96 hours to assess viral viability. Viable RNA and infectious virus in the cultured cells were measured by qPCR and infectious plaque assays. RNA sequencing was performed on a HiSeq platform (Illumina). Samples also underwent SARS-CoV-2 antigen (Ag) testing (BD Veritor). Clinical data were extracted from the electronic health record by chart review.

Results

Pt characteristics are in Table 1. Viral cultures from the repeat specimen were negative (neg) for 18 pts and pos for 2 (Table 2). Pt 1 is a 60M treated with obinatuzumab 19 days prior to his first pos PCR test, with repeat specimen collected 21 days later (cycle threshold (Ct) not available). Pt 1 had a low viral titer (27 PFU/mL) & a D614G mutation on sequencing. Pt 2 is a 75M treated with rituximab 10 days prior to his first pos PCR test, with repeat specimen collected 23 days later (Ct 27.56/27.74). Pt 2 had a high viral titer (2e6 PFU/mL) and D614G, S98F, and S813I mutations.

Demographics of Study Population (N=20)

Conclusion

90% of specimens collected > 21 days after an initial pos SARS-CoV-2 PCR did not have viable virus detected on their repeat specimen. The 2 pts with pos viral cultures had active hematologic malignancies treated with an anti-CD20 mAb at the time of COVID-19 diagnosis. One pt had a high concentration of active, viable virus. No known variants of concern were noted in this cohort, collected in Q2 2020, though prolonged replication is a risk for variant development. Further data are needed about risk factors for persistent viable viral shedding & methods to prevent transmission of viable virus from IC hosts.

Disclosures

Victoria J. Fraser, MD, CDC Epicenters (Grant/Research Support)Cigna/Express Scripts (Other Financial or Material Support, Spouse is Chief Clinical Officer)Doris Duke Fund to Retain Clinical Scientists (Grant/Research Support, Research Grant or Support)Foundation for Barnes-Jewish Hospital (Grant/Research Support, Research Grant or Support)NIH (Grant/Research Support, Research Grant or Support) Victoria J. Fraser, MD, Centers for Disease Control and Prevention (Individual(s) Involved: Self): Grant/Research Support, Research Grant or Support; Cigna/Express Scripts (Individual(s) Involved: Spouse/Partner): Employee; Doris Duke Charitable Foundation (Individual(s) Involved: Self): Grant/Research Support, Research Grant or Support; National Institutes of Health (Individual(s) Involved: Self): Grant/Research Support, Research Grant or Support; The Foundation for Barnes-Jewish Hospital (Individual(s) Involved: Self): Grant/Research Support, Research Grant or Support Michael S. Diamond, MD, PhD, Carnival Corporation (Consultant)Emergent BioSolutions (Grant/Research Support)Fortress Biotech (Consultant)Immunome (Advisor or Review Panel member)Inbios (Consultant)Moderna (Grant/Research Support, Advisor or Review Panel member)Vir Biotechnology (Consultant, Grant/Research Support) Carey-Ann Burnham, PhD, BioFire (Grant/Research Support, Other Financial or Material Support)bioMerieux (Grant/Research Support)Cepheid (Consultant, Grant/Research Support)Luminex (Grant/Research Support)Roche (Other Financial or Material Support) Carey-Ann Burnham, PhD, BioFire (Individual(s) Involved: Self): Grant/Research Support; bioMerieux (Individual(s) Involved: Self): Grant/Research Support, Scientific Research Study Investigator, Speakers’ bureau; Cepheid (Individual(s) Involved: Self): Consultant, Grant/Research Support, Scientific Research Study Investigator; Luminex (Individual(s) Involved: Self): Scientific Research Study Investigator Hilary Babcock, MD, MPH, FIDSA, FSHEA, Nothing to disclose

Characterization of gastric mucosal membranes. IX. Fractionation and purification of K+-ATPase-containing vesicles by zonal centrifugation and free-flow electrophoresis technique

Methods are described for purification of a vesicular membrane fraction of hog gastric mucosa using differential centrifugation, density gradient separation on zonal rotors and free-flow electrophoresis. As a result a fraction is obtained enriched 40-fold in terms of K(+)-ATPase and free of any other enzyme marker other than K(+)-activated p-nitrophenyl phosphatase. The 5'-nucleotidase and basal Mg(2+)-ATPase are clearly separated from the latter enzymes. Osmotic shock, Triton X-100 treatment or K+ ionophores increased the K(+)-ATPase activity in isotonic conditions, but K(+)-p-nitrophenyl phosphatase is not affected by these treatments, nor is the ATPase activity in the presence of NH4+. The results suggest that the electrophoretic fraction contains a major population of tight vesicles, whose permeability to K+ is rate limiting for the ATPase activity but not for the p-nitrophenyl phosphatase activity. It is concluded that K+ site for the ATPase is internal whereas the K+ site for the p-nitrophenyl phosphatase is external, hence, the K+ site must be mobile across the membrane.

Mechanism of activation of fructose-2,6-bisphosphatase by cAMP-dependent protein kinase

The bisphosphatase reaction sequence of rat liver 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase involves a phosphoenzyme intermediate. Catalysis is activated in vitro by cAMP-dependent protein kinase-catalyzed phosphorylation. We investigated the mechanism of this activation by studying the effect of protein kinase-catalyzed phosphorylation on the formation and breakdown of the phosphoenzyme intermediate. The significant findings were as follows. 1) Phosphorylation decreased the rate of phosphoenzyme formation. 2) More importantly, phosphorylation increased the much slower rate of phosphoenzyme breakdown both in the absence and presence of the regulatory ligands, inorganic phosphate and alpha-glycerol phosphate. The increase in the rate of phosphoenzyme breakdown correlated with the degree of activation of the bisphosphatase; both were increased about 2-fold. 3) The potent inhibition of phosphoenzyme breakdown by fructose 6-phosphate indicates that, in the catalytic sequence, the release of nascent fructose 6-phosphate from the active site precedes phosphoenzyme breakdown and Pi release. 4) Phosphorylation reduced the fructose 6-phosphate inhibition of phosphoenzyme breakdown both in the absence and presence of phosphate and alpha-glycerol phosphate. 5) Phosphorylation decreased the potent substrate inhibition which occurs at physiological substrate concentrations. It appears that protein kinase-catalyzed phosphorylation activates fructose-2,6-bisphosphatase by promoting the dissociation of fructose 6-phosphate and fructose 2,6-bisphosphate from the same phosphoenzyme intermediate, hastening its exposure to water and thereby relieving both product and substrate inhibitions.

Evidence for a phosphoenzyme intermediate in the reaction pathway of rat hepatic fructose-2,6-bisphosphatase

We re-examined the kinetics of the bisphosphatase reaction of rat hepatic 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase after depleting the enzyme of bound fructose 6-phosphate and found a hyperbolic dependence on fructose 2,6-bisphosphate at concentrations below 100 nM. The Michaelis constant was 4 nM, the Vmax was about 12 nmol X mg-1 X min-1 at 22 degrees C but the substrate inhibited at concentrations above 100 nM. Both phosphate and alpha-glycerol phosphate strongly inhibited phosphoenzyme formation and hydrolytic rate below 100 nM, but relieved the inhibition by substrate at higher concentrations probably by antagonizing substrate binding. A number of observations support the proposition that the phosphoenzyme is a necessary participant in catalysis. 1) The amount of phosphoenzyme measured during steady-state hydrolysis as a function of substrate concentration correlated with the velocity profile. 2) Rapid mixing experiments demonstrated that over a broad range of substrate concentrations phosphoenzyme formation was faster than the net rate of hydrolysis. 3) Both phosphate and alpha-glycerol phosphate inhibited the rate of phosphoenzyme formation and, at low substrate concentrations, reduced the steady-state phosphoenzyme levels. The latter correlated with inhibition of substrate hydrolysis. 4) Both phosphate and alpha-glycerol phosphate stimulate the rate of phosphoenzyme breakdown, consistent with their stimulation of substrate hydrolysis at high substrate concentrations. 5) The fractional rate of phosphoenzyme breakdown, which was pH and substrate dependent, multiplied by the amount of phosphoenzyme obtained in the steady state at that pH and substrate concentration approximated the observed rate of hydrolysis. We conclude that the phosphoenzyme is a reaction intermediate in the hepatic fructose-2,6-bisphosphatase reaction.

Evidence for two catalytic sites on 6-phosphofructo-2-kinase/fructose 2,6-bisphosphatase. Dynamics of substrate exchange and phosphoryl enzyme formation

The bifunctional enzyme 6-phosphofructo-2-kinase/fructose 2,6-bisphosphatase appears to be the only enzyme catalyzing the formation and hydrolysis of Fru-2,6-P2. The enzyme as we isolate it, contains a trace of tightly bound Fru-6-P. In this condition, it exhibited an ATPase activity comparable to its kinase activity. Inorganic phosphate stimulated all of its activities, by increasing the affinity for all substrates and increasing the Vmax of ATP and Fru-2,6-P2 hydrolysis. The enzyme catalyzed ADP/ATP and Fru-6-P/Fru-2,6-P2 exchanges at rates comparable to net reaction rates. It was phosphorylated by both [gamma-32P]ATP and [2-32P] Fru-2,6-P2, and the label from either donor was chased by either unlabeled donor, showing that the bound phosphate is hydrolyzed if not transferred to an acceptor ligand. The rate of labeling of the enzyme by [2-32P]Fru-2,6-P2 was 2 orders of magnitude greater than the maximal velocity of the bisphosphatase and therefore sufficiently fast to be a step in the hydrolysis. Both inorganic phosphate and Fru-6-P increased the rate and steady state of enzyme phosphorylation by ATP. Fru-2,6-P2 inhibited the ATPase and kinase reactions and Fru-6-P inhibited the Fru-2,6 bisphosphatase reaction while ATP and ADP had no effect. Removal of the trace of Fru-6-P by Glu-6-P isomerase and Glu-6-P dehydrogenase reduced enzyme phosphorylation by ATP to very low levels, greatly inhibited the ATPase, and rendered it insensitive to Pi, but did not affect ADP/ATP exchange. (alpha + beta)Methylfructofuranoside-6-P did not increase the rate or steady state labeling by ATP. These results suggest that labeling of the enzyme by ATP involved the production of [2-32P]Fru-2,6-P2 from the trace Fru-6-P. The 6-phosphofructo-2-kinase, fructose 2,6-bisphosphatase, and ATP/ADP exchange were all inhibited by diethylpyrocarbonate, suggesting the involvement of histidine residues in all three reactions. These results can be most readily explained in terms of two catalytic sites, a kinase site whose phosphorylation by ATP is negligible (or whose E-P is labile) and a Fru-2,6 bisphosphatase site which is readily phosphorylated by Fru-2,6-P2.

Free-flow electrophoresis of an ascites mast-cell tumour

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The interaction of K+ with gastric parietal cells and gastric ATPase

The gastric H+ secretion in isolated cell requires K+ and is ATP dependent. There is also evidence in the cell system for Na+ inhibition of H+ secretion. The isolated gastric ATPase also shows K+ activation and inhibition by K+ or Na+ located on the ATP binding side of the enzyme, which corresponds to the cytoplasmic face of the enzyme. Gastric vesicles are activated in terms of transport activity by internal K+, and this site, inhibited by reagents that modify carboxyl groups, is required for enzyme turnover and transport.

Aspects of parietal cell biology: cells and vesicles

Many features of these gastric vesicles satisfy the requirements for the gastric H+ pump. For example, we have: (a) K+ requirement, (b) KA for K+ of about 30 mM; (c) identical cation sequence for tissue and vesicles, (d) similar anion sequence, (e) localization at the microvillus of the secretory canaliculus, (f) TI+ inhibiting H+ transport of both systems, and (g) the K+ gradient satisfying the osmotic gradient requirement for HCl-flow out of the parietal cell. Points that require explanation are lack of SCN- effects and regulation of KCl permeability.

Isolation and purification of normal and malignant colonic plasma membranes

Plasma membrane fractions from normal colon cells and a transplantable colon adenocarcinoma were isolated and purified by differential and zonal density centrifugation. Enrichment of normal and adenocarcinoma plasma membranes was found in zonal fractions I and II (ZI and ZII) following centrifugation in an 18--50% sucrose gradient. The distribution of various marker enzymes in normal colon preparations suggested an apical origin for the membranes obtained in zonal fraction I while zonal fraction II appeared to contain basal-lateral membrane fragments. Enzymatic analysis of the plasma membrane derived from the colon tumor indicated that these fractions possess a more uniform distribution of Na-K+ ATPase perhaps reflecting a dedifferentiated state. The plasma membrane fractions isolated should prove useful for investigation of transport and other properties of vesicles derived from malignant and normal colon cells.

Intermediates in fatty acid oxidation

1. Aqueous extracts of acetone-dried liver and kidney mitochondria, supplemented with NAD(+), CoA and phenazine methosulphate, efficiently convert fatty-acyl-CoA compounds into acetyl-CoA; the process was followed with an O(2) electrode. 2. Label from [1-(14)C]octanoyl-CoA appears in acetyl-CoA more rapidly than that from [8-(14)C]octanoyl-CoA. 3. Oxidation of [8-(14)C]octanoyl-CoA was terminated by addition of neutral ethanolic hydroxylamine and the resulting hydroxamates were separated chromatographically. Hydroxamate derivatives of 3-hydroxyoctanoyl-, hexanoyl-, butyryl- and acetyl-CoA were obtained. 4. These and other observations suggest that oxidation of octanoyl-CoA by extracts involves participation of free intermediates rather than uninterrupted complete degradation of individual molecules to acetyl-CoA by a multienzyme complex. 5. Intact liver mitochondria studied by the hydroxamate technique were also shown to form intermediates during oxidation of labelled octanoates. In addition to octanoylhydroxamate, [8-(14)C]octanoate gave rise to small amounts of hexanoyl-, butyryl- and 3-hydroxyoctanoyl-hydroxamate. In contrast with extracts, however, where the quantity of intermediates found was a significant fraction of the precursors, mitochondria oxidizing octanoate contained much larger quantities of octanoyl-CoA than of any other intermediate.

Occurrence of ascorbic acid in the yeast Lipomyces starkeyi

Ascorbic acid was identified in cultures of the yeast Lipomyces starkeyi. The acid was identified by preparing the Roe and Kuether chromogen and comparing its infrared spectrum with the spectra of chromogens derived from ascorbic and araboascorbic acids. After 5 days of growth on glucose medium the ascorbic acid concentration in cellular extracts was 214 μg/g wet weight.

Lipid synthesis in Lipomyces lipofer

The synthesis of lipids by cell-free fractions of Lipomyces lipofer was investigated by measuring the incorporation of acetate-14C and other radioactive precursors into lipid-soluble material. On the basis of cofactor requirements, the reaction to inhibitors, and the ability to incorporate appreciable quantities of malonate-14C, it was concluded that the malonyl-CoA pathway was the principal route of fatty acid synthesis in this yeast. By employing a means of cell dispersion less rigorous than previously used with yeasts, it was shown that the soluble portion (high-speed supernatant) of the cell was primarily involved in lipid synthesis. The mitochondrial fraction and the high-speed pellet (96 000 × g, 1 h) were inactive although the latter fraction was required for the maximum activity of the high-speed supernatant. The stimulatory activity of this pellet was very labile and showed a lag period before it became effective. Several lines of evidence suggested that the carboxylation of acetyl-CoA is the rate-limiting step in lipid synthesis which is accelerated by the high-speed pellet.

Participation of nicotinamide mononucleotide in pyridine nucleotide synthesis in tumor and host liver

Evidence is presented to show that nicotinamide-7-14C in low or high doses is incorporated into nicotinamide mononucleotide (NMN) by Ehrlich ascites cells and host liver in vivo. Nicotinamide mononucleotide formed from nicotinamide-7-14C has been isolated from incubations of Sephadex-treated extracts of ascites cell acetone powders with 5-phosphoribosyl-1-pyrophosphate and characterized by spectral and chemical analysis. The apparent Kmand Vmaxfor NMN synthesis from nicotinamide have been determined. NMN-14C has been shown to form NAD-14C in the same extracts in the presence of ATP, and the apparent Vmaxand Kmof this process have been determined. The role of NMN in NAD synthesis is discussed.

The mechanism of pyridine nucleotide synthesis in Ehrlich ascites carcinoma and host liver

Labeled nicotinamide–adenine dinucleotide (NAD) and nicotinic acid–adenine dinucleotide (NacAD) were identified following Dowex 2 (formate) chromatography of extracts of Ehrlich ascites cells and of livers of mice 3 and 6 h after injection of nicotinamide (Nam) (500 mg/kg) containing Nam-7-14C, and 3 h after injection of nicotinic acid (Nac) (50 mg/kg) containing Nac-7-14C into tumor-bearing animals. Labeled Nac mononucleotide (NacMN) was also identified in the liver extracts. The urinary metabolic products of the precursors were separated and partially characterized. Liver appeared to be somewhat more active in synthesis of NAD than tumor; the more efficient amidation of NacAD to NAD in liver probably contributes to this difference. The results are consistent with NacAD being an intermediate in NAD biosynthesis. Investigations of extracts of acetone powders of tumor provided evidence for two possible routes of synthesis (via NMN, and NacMN–NacAD): (1) Extracts incubated with Nam mononucleotide (NMN) and ATP formed NAD. (2) Extracts incubated with Nac-14C or Nam-14C with suitable supplementation gave rise to labeled NacMN, NacAD and NAD. These substances were isolated and their specific activities determined. Glutamine appeared to enhance NAD formation at the expense of NacAD. Although a net accumulation of NAD did not occur, the formation of Nam-14C from Nac-14C and the demonstration of NADase in the preparations suggested that NAD was formed but rapidly degraded.

The lipids of Lipomyces lipofer

As a preliminary to the study of lipid synthesis in Lipomyces lipofer, the nature of the lipid accumulated by this organism was investigated. Neutral lipids were found to predominate, especially in older cultures of high lipid content. The triglyceride fraction was the major component, with smaller quantities of hydrocarbon, free and esterified ergosterol, monoglyceride, diglyceride, and free fatty acid also present. Phosphatid-y-linositol constituted almost one-quarter of the phospholipid fraction. The phosphoglycerides of choline, serine and ethanolamine were also detected. Gas chromatographic evidence indicated that 16:0, 16:1, 18:0, 18:1, 18:2, 18:3 were the principal fatty acid components. The 18:1 fraction was shown by oxidative-cleavage studies to be primarily oleic acid. This fraction predominated, reaching a level of 69% of the total fatty acids in older cultures.