SARS-CoV-2 is the cause of an ongoing pandemic that has infected over 36 million and killed over 1 million people. Informed implementation of government public health policies depends on accurate data on SARS-CoV-2 immunity at population scale. We hypothesized that detection of SARS-CoV-2 salivary antibodies could serve as a non-invasive alternative to serological testing for monitoring of SARS-CoV-2 infection and seropositivity at population scale. We developed a multiplex SARS-CoV-2 antibody immunoassay based on Luminex technology that comprised 12 CoV antigens, mostly derived from SARS-CoV-2 nucleocapsid (N) and spike (S). Saliva and sera collected from confirmed COVID-19 cases and from the pre-COVID-19 era were tested for IgG, IgA and IgM to the antigen panel. Matched saliva and serum IgG responses (n=28) were significantly correlated. The salivary anti-N IgG response resulted in highest sensitivity (100%), exhibiting a positive response in 24/24 RT-PCR-confirmed COVID-19 cases sampled at >14 days post-symptom onset (DPSO), whereas the salivary anti-receptor binding domain (RBD) IgG response yielded 100% specificity. Temporal kinetics of IgG in saliva were consistent with those observed in blood and indicated that most individuals seroconvert around 10 DPSO. Algorithms employing a combination of the IgG response to N and S antigens result in high diagnostic accuracy (100%) as early as 10 DPSO. These results support the use of saliva-based antibody testing as a non-invasive and scalable alternative to blood-based antibody testing.

Non-invasive SARS-CoV-2 antibody testing is urgently needed to estimate the incidence and prevalence of SARS-CoV-2 infection at the general population level. Precise knowledge of population immunity could allow government bodies to make informed decisions about how and when to relax stay-at-home directives and to reopen the economy. We hypothesized that salivary antibodies to SARS-CoV-2 could serve as a non-invasive alternative to serological testing for widespread monitoring of SARS-CoV-2 infection throughout the population. We developed a multiplex SARS-CoV-2 antibody immunoassay based on Luminex technology and tested 167 saliva and 324 serum samples, including 134 and 118 negative saliva and serum samples, respectively, collected before the COVID-19 pandemic, and 33 saliva and 206 serum samples from participants with RT-PCR-confirmed SARS-CoV-2 infection. We evaluated the correlation of results obtained in saliva vs. serum and determined the sensitivity and specificity for each diagnostic media, stratified by antibody isotype, for detection of SARS-CoV-2 infection based on COVID-19 case designation for all specimens. Matched serum and saliva SARS-CoV-2 antigen-specific IgG responses were significantly correlated. Within the 10-plex SARS-CoV-2 panel, the salivary anti-nucleocapsid (N) protein IgG response resulted in the highest sensitivity for detecting prior SARS-CoV-2 infection (100% sensitivity at ≥10 days post-SARS-CoV-2 symptom onset). The salivary anti-receptor binding domain (RBD) IgG response resulted in 100% specificity. Among individuals with SARS-CoV-2 infection confirmed with RT-PCR, the temporal kinetics of IgG, IgA, and IgM in saliva were consistent with those observed in serum. SARS-CoV-2 appears to trigger a humoral immune response resulting in the almost simultaneous rise of IgG, IgM and IgA levels both in serum and in saliva, mirroring responses consistent with the stimulation of existing, cross-reactive B cells. SARS-CoV-2 antibody testing in saliva can play a critically important role in large-scale 'sero'-surveillance to address key public health priorities and guide policy and decision-making for COVID-19.

Antimicrobial use (AMU) in animal agriculture contributes to antimicrobial resistance (AMR) in humans, which imposes significant health and economic costs on society. Economists call these costs negative externalities, societal costs that are not properly reflected in market prices. We review the relevant literature and develop a model to quantify the external costs of AMU in animal agriculture on AMR in humans. Parameters required for this estimate include ( a) the health and economic burden of AMR in humans,( b) the impact of AMU in animal agriculture on AMR in animals, ( c) the fraction of AMR in humans attributable to animal agriculture, and ( d) AMU in animals. We use a well-documented historic case to estimate an externality cost of about US$1,500 per kilogram of fluoroquinolones administered in US broiler chicken production. Enhanced data collection, particularly on the third and fourth parameters, is urgently needed to quantify more fully the externalities of AMU in animal agriculture.

Oral fluid (hereafter saliva) offers a non-invasive sampling method for the detection of SARS-CoV-2 antibodies. However, data comparing performance of salivary tests against commercially-available serologic and neutralizing antibody (nAb) assays are lacking. This study compared the performance of a multiplex salivary SARS-CoV-2 IgG assay targeting antibodies to nucleocapsid (N), receptor binding domain (RBD) and spike (S) antigens to three commercially-available SARS-CoV-2 serology enzyme immunoassays (EIAs) (Ortho Vitros, Euroimmun, and BioRad) and nAb. Paired saliva and plasma samples were collected from 101 eligible COVID-19 convalescent plasma (CCP) donors >14 days since PCR+ confirmed diagnosis. Concordance was evaluated using positive (PPA) and negative (NPA) percent agreement, overall percent agreement (PA), and Cohen’s kappa coefficient. The range between salivary and plasma EIAs for SARS-CoV-2-specific N was PPA: 54.4-92.1% and NPA: 69.2-91.7%, for RBD was PPA: 89.9-100% and NPA: 50.0-84.6%, and for S was PPA: 50.6-96.6% and NPA: 50.0-100%. Compared to a plasma nAb assay, the multiplex salivary assay PPA ranged from 62.3% (N) and 98.6% (RBD) and NPA ranged from 18.8% (RBD) to 96.9% (S). Combinations of N, RBD, and S and a summary algorithmic index of all three (N/RBD/S) in saliva produced ranges of PPA: 87.6-98.9% and NPA: 50-91.7% with the three EIAs and ranges of PPA: 88.4-98.6% and NPA: 21.9-34.4% with the nAb assay. A multiplex salivary SARS-CoV-2 IgG assay demonstrated comparable performance to three commercially-available plasma EIAs and a nAb assay, and may be a viable alternative to assist in screening CCP donors and monitoring population-based seroprevalence and vaccine antibody response.

We evaluated the durability of IgG responses specific to SARS-CoV-2 nucleocapsid (N), receptor binding domain (RBD), and spike (S) antigens in saliva up to 8 months after RT-PCR-confirmed COVID-19 using a multiplex salivary assay. We estimated a half-life of 64 days (d) (95% CI: 49, 80 d) for N, 100 d for RBD (95% CI: 58, 141 d), and 148 d (95% CI: 62, 238 d) for S IgG responses in saliva, consistent with half-life estimates previously reported in blood. Saliva can serve as an alternative to blood to monitor humoral immune responses on a large scale following natural SARS-CoV-2 infection and vaccination for surveillance and assessment of population immunity.

Staphylococcus aureus ST45 is a major global MRSA lineage with a huge strain diversity and a high clinical impact. It is one of the most prevalent carrier lineages but also frequently causes severe invasive disease such as bacteremia. Little is known about its evolutionary history. In this study, we used whole genome sequencing to analyze a large collection of 451 diverse ST45 isolates from six continents and 26 countries. De novo assembled genomes were used to understand genomic plasticity and to perform coalescent analyses. The ST45 population contained two distinct sublineages, which correlated with the isolates' geographical origin. One sublineage primarily consisted of European/North American isolates, whilst the second sublineage primarily consisted of African and Australian isolates. Bayesian analysis predicted ST45 originated in North Western Europe about 500 years ago. Isolation time, host and clinical symptoms did not correlate with phylogenetic groups. Our phylogenetic analyses suggest multiple acquisitions of the SCCmec element and key virulence factors throughout the evolution of the ST45 lineage.

Gram-positive organisms are often found in association with burn wounds. A paucity of information exists regarding the accumulation and fate of virulence factors from these bacteria. The superantigenic exotoxins produced by Staphylococcus aureus are potent immunomodulating proteins and have also been described to localize in the kidney. The aim of this work was to demonstrate renal accumulation of toxic shock syndrome toxin-1 (TSST-1) and staphylococcal enterotoxin B (SEB) in a methicillin-resistant S. aureus burn wound infection. Twelve Sprague Dawley rats were subjected to partial-thickness burns (2 × 2 cm) using an aluminum billet. On postburn day 1, the wounds were inoculated with a toxin-producing strain of methicillin-resistant Skin biopsies and serum were obtained on postburn days 3, 6, and 10 along with necropsies for three animals each day. An enzyme-linked immunosorbent assay was used to quantify amounts of TSST-1 and SEB. Immunohistochemistry was used to localize SEB, TSST-1, and cleaved caspase-3 in renal tissue, and quantitative real-time polymerase chain reaction was used to assess erythropoietin and endothelin-1 messenger RNA (mRNA) in renal tissue. Baseline skin and plasma levels of TSST-1 and SEB were not detectable. Skin biopsy TSST-1 levels were detected on all postburn days and peaked at a mean value of 39.35 ng/ml on day 6; SEB was found in the skin and kidney only on postburn days 6 and 10. An enzyme-linked immunosorbent assay of renal tissue for TSST-1 and SEB demonstrated significantly higher (P < .05) mean toxin concentrations on postburn day 10: 10.87 ng/ml for TSST-1 and 0.67 ng/ml for SEB. Immunohistochemistry of renal tissue demonstrated increased stain intensity for SEB, TSST-1, and cleaved caspase-3 over time. Quantitative real-time polymerase chain reaction demonstrated decreased expression erythropoietin mRNA and increased expression of endothelin-1 mRNA relative to negative controls (P < .01). In a burn wound infection model that is nonlethal and lacks bacteremia, TSST-1 and SEB traverse cutaneous wounds and localize to the kidney. These potent virulence factors may contribute to the induction of apoptosis, and may alter homeostasis via renal pathophysiology.

Mortality rates in burn patients increase if they experience complications of infection. Frequently, the organisms associated with such infections are Staphylococci, including antibiotic-resistant species such as methicillin-resistant Staphylococcus aureus. Virulence factor production can further complicate treatment as a localized toxin presence may derail the healing process and allow a more invasive infection, while a toxin that becomes systemic can induce shock and cause host immune disruption. Male rats were anesthetized and subjected to full-thickness burn wounds. One day postinjury, wounds were inoculated with Toxic Shock Syndrome Toxin-1-producing methicillin-resistant S. aureus. Animals were then divided into three treatment groups: vancomycin, linezolid, or positive control. For nine additional days, animals received twice-daily antibiotics and wound assessments, blood draws, and wound biopsies were performed. All animals had wound quantitative cultures that exceeded 1 × 10 colony forming units (CFU) per gram 1 day after inoculation. Linezolid treatment significantly reduced the bacterial counts in the wounds. Positive controls and vancomycin-treated animals had toxins in their wounds by day 5 and this remained throughout the study (ranging from 20-80 ng/ml). Linezolid-treated animals had significant decrease in toxin production (< 5 ng/ml), and in most cases toxins were undetectable. No animals became systemically infected with bacteria at any point during the study. Superantigen production in burn wounds has morbid consequences in terms of long-term wound healing. A S. aureus burn wound infection model was created that allowed the study of the effect of two standard-use antibiotics on local burn wound pathophysiology. Most noteworthy is that low-dose linezolid arrested toxin production in the wound.