Efficacy of detergent-based cleaning and wiping against SARS-CoV-2 on high-touch surfaces

Efficacy of cleaning methods against SARS-CoV-2 suspended in either 5% soil load (SARS-soil) or simulated saliva (SARS-SS) was evaluated immediately (hydrated virus, T0) or 2 hours post-contamination (dried virus, T2). Hard water dampened wiping (DW) of surfaces, resulted in 1.77-3.91 log reduction (T0) or 0.93-2.41 log reduction (T2). Incorporating surface pre-wetting by spraying with a detergent solution (D + DW) or hard water (W + DW) just prior to dampened wiping did not unilaterally increase efficacy against infectious SARS-CoV-2, however, the effect was nuanced with respect to surface, viral matrix, and time. Cleaning efficacy on porous surfaces (seat fabric, SF) was low. W + DW on stainless steel (SS) was as effective as D + DW for all conditions except SARS-soil at T2 on SS. DW was the only method that consistently resulted in > 3-log reduction of hydrated (T0) SARS-CoV-2 on SS and ABS plastic. These results suggest that wiping with a hard water dampened wipe can reduce infectious virus on hard non-porous surfaces. Pre-wetting surfaces with surfactants did not significantly increase efficacy for the conditions tested. Surface material, presence or absence of pre-wetting, and time post-contamination affect efficacy of cleaning methods.

Evaluation of surface disinfection methods to inactivate the beta coronavirus Murine Hepatitis Virus

The list of EPA-approved disinfectants for coronavirus features many products for use on hard, non-porous materials. There are significantly fewer products registered for use on porous materials. Further, many common, high-touch surfaces fall in between non-porous materials such as glass and porous materials such as soft fabrics. The objective of this study was to assess the efficacy of selected commercially available disinfectant products against coronaviruses on common, high-touch surfaces. Four disinfectants (Clorox Total 360, Bleach solution, Vital Oxide, and Peroxide Multi-Surface Cleaner) were evaluated against Murine Hepatitis Virus A59 (MHV) as a surrogate coronavirus for SARS-CoV-2. MHV in cell culture medium was inoculated onto four materials: stainless steel, latex-painted drywall tape, Styrene Butadiene rubber (rubber), and bus seat fabric. Immediately (T0) or 2-hr (T2) post-inoculation, disinfectants were applied by trigger-pull or electrostatic sprayer and either held for recommended contact times (Spray only) or immediately wiped (Spray and Wipe). Recovered infectious MHV was quantified by median tissue culture infectious dose assay. Bleach solution, Clorox Total 360, and Vital Oxide were all effective (>3-log₁₀ reduction or complete kill of infectious virus) with both the Spray Only and Spray and Wipe methods on stainless steel, rubber, and painted drywall tape when used at recommended contact times at both T0 and T2 hr. Multi-Surface Cleaner unexpectedly showed limited efficacy against MHV on stainless steel within the recommended contact time; however, it showed increased (2.3 times greater efficacy) when used in the Spray and Wipe method compared to Spray Only. The only products to achieve a 3-log₁₀ reduction on fabric were Vital Oxide and Clorox Total 360; however, the efficacy of Vital Oxide against MHV on fabric was reduced to below 3-log₁₀ when applied by an electrostatic sprayer compared to a trigger-pull sprayer. This study highlights the importance of considering the material, product, and application method when developing a disinfection strategy for coronaviruses on high-touch surfaces.

Residual Antimicrobial Coating Efficacy Against SARS-CoV-2

AIMS

This study evaluated the residual efficacy of commercially available antimicrobial coatings or films against SARS-CoV-2 on nonporous surfaces.

METHOD AND RESULTS

Products were applied to stainless steel or ABS plastic coupons and dried overnight. Coupons were inoculated with SARS-CoV-2 in the presence of 5% soil load. Recovered infectious SARS-CoV-2 was quantified by TCID50 assay. Tested product efficacies ranged from <1.0 to >3.0 log₁₀ reduction at a 2-hour contact time. The log₁₀ reduction in recovered infectious SARS-CoV-2 ranged from 0.44 to 3 log₁₀ reduction on stainless steel and 0.25 to >1.67 log₁₀ on ABS plastic. The most effective products tested contained varying concentrations (0.5 to 1.3%) of the same active ingredient: 3- (trihydroxysilyl) propyldimethyloctadecyl ammonium chloride. Products formulated with other quaternary ammonium compounds were less effective against SARS-CoV-2 in this test.

CONCLUSIONS

The residual antimicrobial products tested showed varied effectiveness against SARS-CoV-2 as a function of product tested. Several products were identified as efficacious against SARS-CoV-2 on both stainless steel and ABS plastic surfaces under the conditions evaluated. Differences in observed efficacy may be due to variation in active ingredient formulation; efficacy is, therefore, difficult to predict based upon listed active ingredient and its concentration.

SIGNIFICANCE AND IMPACT

This study highlights formulation-specific efficacy of several products against SARS-CoV-2 and may inform future development of residual antiviral products for use on nonporous surfaces. The identification of antimicrobial coatings or films showing promise to inactivate SARS-CoV-2 suggests that these products may be worth future testing and consideration.

Prevalence of Influenza A Virus in Exhibition Swine during Arrival at Agricultural Fairs

The exhibition swine at agricultural fairs provides a critical human-swine interface that allows for the bidirectional transmission of influenza A virus (IAV). Previous IAV surveillance at the end of fairs has resulted in frequent detection of IAV-infected swine; little is known, however, about the frequency with which swine arrive at fairs already infected with IAV. We investigated the IAV prevalence among exhibition swine entering fairs to better understand the epidemiology of IAV in this unique human-swine interface. In 2014, snout wipes were collected from 3547 swine during the first day of nine agricultural exhibitions in Indiana and Ohio. Samples were screened for IAV using rRT-PCR and positive samples were inoculated into cultured cells for virus isolation. The overall IAV prevalence detected among swine arriving at exhibitions was 5.3% (188/3547) via rRT-PCR and 1.5% (53/3547) via virus isolation, with IAV being detected and recovered from swine at 5 of the 9 exhibitions. Within the fairs with IAV-positive swine, the individual exhibition IAV prevalence ranged from 0.2% (1/523) to 34.4% (144/419) using rRT-PCR and 0.2% (1/523) to 10.3% (43/419) with virus isolation. Single IAV subtypes were detected at three of the fairs but subtype diversity was detected among the pigs at two fairs as both H1N1 and H3N2 were recovered from incoming swine. At two of the exhibitions, a temporal relationship was observed between the order of the individual swine in sampling and the associated IAV rRT-PCR results, indicating the fomite transmission of IAV through common contact surfaces may occur. With the knowledge that a small proportion of swine arrive at fairs shedding IAV, resources should be directed towards preventive strategies focused on limiting transmission during fairs to protect swine and humans during exhibitions.

Environment of tryptophan 57 in porcine fructose-1,6-bisphosphatase studied by time-resolved fluorescence and site-directed mutagenesis

The environment of Trp57, introduced by the mutation of a tyrosine in the dynamic loop of porcine liver fructose-1,6-bisphosphatase (FBPase), was examined using time-resolved fluorescence and directed mutation. The Trp57 enzyme was studied previously by X-ray crystallography and steady-state fluorescence, the latter revealing an unexpected redshift in the wavelength of maximum fluorescence emission for the R-state conformer. The redshift was attributed to the negative charge of Asp127 in contact with the indole side chain of Trp57. Time-resolved fluorescence experiments here reveal an indole side chain less solvent exposed and more rigid in the R-state, than in the T-state of the enzyme, consistent with X-ray crystal structures. Replacement of Asp127 with an asparagine causes a 6 nm blueshift in the wavelength of maximum fluorescence emission for the R-state conformer, with little effect on the emission maximum of the T-state enzyme. The data here support the direct correspondence between X-ray crystal structures of FBPase and conformational states of the enzyme in solution, and provide a clear example of the influence of microenvironment on the fluorescence properties of tryptophan.

Subperiosteal and intraosseous connective tissue grafts for pocket reduction: a 9- to 13-year retrospective case series report

BACKGROUND

Recent histological evidence has documented that grafted palatal connective tissue is capable of forming a new attachment to previously exposed roots in the treatment of gingival recession. No clinical studies have tested the ability of connective tissue that has been implanted beneath the periosteum into periodontal osseous defects to reduce probing depth and increase clinical attachment levels. This study reports the long-term clinical effect of subperiosteal and intraosseous connective tissue grafts on deep periodontal pockets.

METHODS

Connective tissue (CT) grafts were placed in 32 periodontal pockets on 27 patients. Grafts were classified into 3 groups. Type I grafts had 50% or more vascular surface contact and were < or = 2.5 mm thick. Type II grafts had 50% or more contact but were > 2.5 mm thick, and Type III grafts had less than 50% vascular contact regardless of thickness. Twelve of 14 Type I sites, 9 of 15 Type II sites, and 3 of 3 Type III sites were analyzed 9 to 13 years following treatment.

RESULTS

Clinical attachment level change differed significantly between the graft types on survivor teeth (P < 0.05): Type III had 2 mm loss (95% confidence interval [CI]: 0.4 to 3.6), while Type II and Type I grafts had a 2.7 mm gain (95% CI: 2.0 to 3.4) and 4.3 mm gain (95% CI: 3.3 to 5.2), respectively. Similar substantial differences were presented for changes in probing depth and recession.

CONCLUSIONS

This long-term (9 to 13 years) retrospective case-series analysis suggests substantial improvements in periodontal clinical measures for Type I CT grafts in deep periodontal pockets. Randomized trials are required to evaluate this promising procedure.

Subperiosteal connective tissue grafts for pocket reduction and preservation of gingival esthetics: a case report

BACKGROUND

Clinical studies and recent histological evidence following mucogingival surgery for the treatment of gingival recession have documented that when closely adapted to a previously exposed root surface, connective tissue is capable of forming a new attachment. Despite these findings, no clinical tests have been conducted to examine the ability of connective tissue to reduce probing depth (PD) and increase clinical attachment levels (CAL) when it is implanted into periodontal osseous defects. The purpose of this paper is to report the clinical results on a patient following 2 subperiosteal connective tissue grafts.

METHODS

Subperiosteal connective tissue grafts were placed in 2 sites of periodontal bone loss and deep pocketing in one patient. Following flap reflection and root preparation, a connective tissue graft 1.5 to 2.0 mm in thickness was draped and sutured over each osseous defect and then completely covered by the external flap.

RESULTS

Ten months following subperiosteal connective tissue grafting, tooth #7 had 4 mm of CAL gain. Tooth #10 had 3 mm of CAL gain 8 months postoperatively. Both teeth had 1 mm gain in gingival recession. Both teeth probed 3 mm postoperatively.

CONCLUSIONS

When connective tissue was grafted into 2 periodontal osseous defects, there were significant reductions in probing depth and gains in CAL. There was minimal postoperative gingival recession. The new clinical attachment gain remained stable for 8 to 10 months following subperiosteal connective tissue grafting.

Spontaneous subunit exchange in porcine liver fructose-1,6-bisphosphatase

No evidence to date suggests the possibility of subunit exchange between tetramers of mammalian fructose-1,6-bisphosphatase. An engineered fructose-1,6-bisphosphatase, with subunits of altered electrostatic charge, exhibits spontaneous subunit exchange with wild-type enzyme in the absence of ligands. The exchange process reaches equilibrium in approximately 5 h at 4 degrees C, as monitored by non-denaturing gel electrophoresis and anion exchange chromatography. Active site ligands, such as fructose 6-phosphate, abolish subunit exchange at the level of the monomer, but permit dimer-dimer exchanges. AMP, alone or in the presence of active site ligands, abolishes all exchange processes. Exchange phenomena may play a role in the kinetic mechanism of allosteric regulation of fructose-1,6-bisphosphatase.

The N-terminal segment of recombinant porcine fructose-1,6-bisphosphatase participates in the allosteric regulation of catalysis

Residues 1--10 of porcine fructose-1,6-bisphosphatase (FBPase) are poorly ordered or are in different conformations, sensitive to the state of ligation of the enzyme. Deletion of the first 10 residues of FBPase reduces k(cat) by 30-fold and Mg(2+) affinity by 20-fold and eliminates cooperativity in Mg(2+) activation. Although a fluorescent analogue of AMP binds with high affinity to the truncated enzyme, AMP itself potently inhibits only 50% of the enzyme activity. Additional inhibition occurs only when the concentration of AMP exceeds 10 mm. Deletion of the first seven residues reduces k(cat) and Mg(2+) affinity significantly but has no effect on AMP inhibition. The mutation of Asp(9) to alanine reproduces the weakened affinity for Mg(2+) observed in the deletion mutants, and the mutation of Ile(10) to aspartate reproduces the AMP inhibition of the 10-residue deletion mutant. Changes in the relative stability of the known conformational states for loop 52--72, in response to changes in the quaternary structure of FBPase, can account for the phenomena above. Some aspects of the proposed model may be relevant to all forms of FBPase, including the thioredoxin-regulated FBPase from the chloroplast.

Mutations in the hinge of a dynamic loop broadly influence functional properties of fructose-1,6-bisphosphatase

Loop 52-72 of porcine fructose-1,6-bisphosphatase may play a central role in the mechanism of catalysis and allosteric inhibition by AMP. The loop pivots between different conformational states about a hinge located at residues 50 and 51. The insertion of proline separately at positions 50 and 51 reduces k(cat) by up to 3-fold, with no effect on the K(m) for fructose 1,6-bisphosphate. The K(a) for Mg(2+) in the Lys(50) --> Pro mutant increases approximately 15-fold, whereas that for the Ala(51) --> Pro mutant is unchanged. Although these mutants retain wild-type binding affinity for AMP and the fluorescent AMP analog 2'(3')-O-(trinitrophenyl)adenosine 5'-monophosphate, the K(i) for AMP increases 8000- and 280-fold in the position 50 and 51 mutants, respectively. In fact, the mutation Lys(50) --> Pro changes the mechanism of AMP inhibition with respect to Mg(2+) from competitive to noncompetitive and abolishes K(+) activation. The K(i) for fructose 2,6-bisphosphate increases approximately 20- and 30-fold in the Lys(50) --> Pro and Ala(51) --> Pro mutants, respectively. Fluorescence from a tryptophan introduced by the mutation of Tyr(57) suggests an altered conformational state for Loop 52-72 due to the proline at position 50. Evidently, the Pro(50) mutant binds AMP with high affinity at the allosteric site, but the mechanism of allosteric regulation of catalysis has been disabled.

Tryptophan fluorescence reveals the conformational state of a dynamic loop in recombinant porcine fructose-1,6-bisphosphatase

Wild-type porcine fructose-1,6-bisphosphatase (FBPase) has no tryptophan residues. Hence, the mutation of Try57 to tryptophan places a unique fluorescent probe in the structural element (loop 52-72) putatively responsible for allosteric regulation of catalysis. On the basis of steady-state kinetics, circular dichroism spectroscopy, and X-ray crystallography, the mutation has little effect on the functional and structural properties of the enzyme. Fluorescence intensity from the Trp57 mutant is maximal in the presence of divalent cations, fructose 6-phosphate and orthophosphate, which together stabilize an R-state conformation in which loop 52-72 is engaged with the active site. The level of fluorescence emission decreases monotonically with increasing levels of AMP, an allosteric inhibitor, which promotes the T-state, disengaged-loop conformation. The titration of various metal-product complexes of the Trp57 mutant with fructose 2,6-bisphosphate (F26P(2)) causes similar decreases in fluorescence, suggesting that F26P(2) and AMP individually induce similar conformational states in FBPase. Fluorescence spectra, however, are sensitive to the type of divalent cation (Zn(2+), Mn(2+), or Mg(2+)) and suggest conformations in addition to the R-state, loop-engaged and T-state, loop-disengaged forms of FBPase. The work presented here demonstrates the utility of fluorescence spectroscopy in probing the conformational dynamics of FBPase.

The subpedicle connective tissue graft. A bilaminar reconstructive procedure for the coverage of denuded root surfaces

A mucogingival grafting procedure has been developed to cover denuded root surfaces. This procedure, the subpedicle connective tissue graft, is a bilaminar graft that is composed of a free connective tissue graft and an overlying pedicle graft. By overlaying grafted free connective tissue with a pedicle, the otherwise compromised section of free graft which covers a denuded root surface is supplied by plasmatic circulation from capillaries in the vascular portion of the pedicle allowing it to survive. In this report 29 teeth were treated and monitored for as long as 42 months. In the group with advanced recession of 7 to 10 mm, there was an average of 88% coverage. The subpedicle graft created a healthy, functional, and esthetic result that appeared resistant to further breakdown. The subpedicle graft is indicated when a single surgical procedure is desired that will predictably cover denuded root surfaces when there is inadequate keratinized gingiva available for a pedicle graft and where the prognosis is poor for root coverage with a free gingival graft.

The continuing evolution of the categorical course concept

The Society's initial venture in the categorical course was an overwhelming success. Future offerings coordinated between the RSNA, ACR and ARRS could play an outstanding role in recertification.

Development potentialities of marrow tissue culture cells surviving programmed freezing

Monkey bone marrow cells that had undergone programmed freezing in liquid nitrogen were cultured for two weeks and then were implanted autogenously within millipore filter chambers. Marrow tissue was formed from this cellular implantation. This tissue appeared similar to mature marrow consisting of hematopoietic as well as connective tissue elements.