Timely intervention and control of a novel coronavirus (COVID-19) outbreak at a large skilled nursing facility-San Francisco, California, 2020.

OBJECTIVE: To describe epidemiologic and genomic characteristics of a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak in a large skilled-nursing facility (SNF), and the strategies that controlled transmission. DESIGN, SETTING, AND PARTICIPANTS: This cohort study was conducted during March 22-May 4, 2020, among all staff and residents at a 780-bed SNF in San Francisco, California. METHODS: Contact tracing and symptom screening guided targeted testing of staff and residents; respiratory specimens were also collected through serial point prevalence surveys (PPSs) in units with confirmed cases. Cases were confirmed by real-time reverse transcription-polymerase chain reaction testing for SARS-CoV-2, and whole-genome sequencing (WGS) was used to characterize viral isolate lineages and relatedness. Infection prevention and control (IPC) interventions included restricting from work any staff who had close contact with a confirmed case; restricting movement between units; implementing surgical face masking facility-wide; and the use of recommended PPE (ie, isolation gown, gloves, N95 respirator and eye protection) for clinical interactions in units with confirmed cases. RESULTS: Of 725 staff and residents tested through targeted testing and serial PPSs, 21 (3%) were SARS-CoV-2 positive: 16 (76%) staff and 5 (24%) residents. Fifteen cases (71%) were linked to a single unit. Targeted testing identified 17 cases (81%), and PPSs identified 4 cases (19%). Most cases (71%) were identified before IPC interventions could be implemented. WGS was performed on SARS-CoV-2 isolates from 4 staff and 4 residents: 5 were of Santa Clara County lineage and the 3 others were distinct lineages. CONCLUSIONS: Early implementation of targeted testing, serial PPSs, and multimodal IPC interventions limited SARS-CoV-2 transmission within the SNF.

The anti-microbial peptide TP359 attenuates inflammation in human lung cells infected with Pseudomonas aeruginosa via TLR5 and MAPK pathways.

Pseudomonas aeruginosa infection induces vigorous inflammatory mediators secreted by epithelial cells, which do not necessarily eradicate the pathogen. Nonetheless, it reduces lung function due to significant airway damage, most importantly in cystic fibrosis patients. Recently, we published that TP359, a proprietary cationic peptide had potent bactericidal effects against P. aeruginosa, which were mediated by down-regulating its outer membrane biogenesis genes. Herein, we hypothesized that TP359 bactericidal effects could also serve to regulate P. aeruginosa-induced lung inflammation. We explored this hypothesis by infecting human A549 lung cells with live P. aeruginosa non-isogenic, mucoid and non-mucoid strains and assessed the capacity of TP359 to regulate the levels of elicited TNFα, IL-6 and IL-8 inflammatory cytokines. In all instances, the mucoid strain elicited higher concentrations of cytokines in comparison to the non-mucoid strain, and TP359 dose-dependently down-regulated their respective levels, suggesting its regulation of lung inflammation. Surprisingly, P. aeruginosa flagellin, and not its lipopolysaccharide moiety, was the primary inducer of inflammatory cytokines in lung cells, which were similarly down-regulated by TP359. Blocking of TLR5, the putative flagellin receptor, completely abrogated the capacity of infected lung cells to secrete cytokines, underscoring that TP359 regulates inflammation via the TLR5-dependent signaling pathway. Downstream pathway-specific inhibition studies further revealed that the MAPK pathway, essentially p38 and JNK are necessary for induction of P. aeruginosa elicited inflammatory cytokines and their down-regulation by TP359. Collectively, our data provides evidence to support exploring the relevancy of TP359 as an anti-microbial and anti-inflammatory agent against P. aeruginosa for clinical applications.

Novel cationic peptide TP359 down-regulates the expression of outer membrane biogenesis genes in Pseudomonas aeruginosa: a potential TP359 anti-microbial mechanism.

BACKGROUND: Antimicrobial peptides (AMPs) are a class of antimicrobial agents with broad-spectrum activities. Several reports indicate that cationic AMPs bind to the negatively charged bacterial membrane causing membrane depolarization and damage. However, membrane depolarization and damage may be insufficient to elicit cell death, thereby suggesting that other mechanism(s) of action could be involved in this phenomenon. In this study, we investigated the antimicrobial activity of a novel antimicrobial peptide, TP359, against two strains of Pseudomonas aeruginosa, as well as its possible mechanisms of action. RESULTS: TP359 proved to be bactericidal against P. aeruginosa as confirmed by the reduced bacteria counts, membrane damage and cytoplasmic membrane depolarization. In addition, it was non-toxic to mouse J774 macrophages and human lung A549 epithelial cells. Electron microscopy analysis showed TP359 bactericidal effects by structural changes of the bacteria from viable rod-shaped cells to those with cell membrane damages, proceeding into the efflux of cytoplasmic contents and emergence of ghost cells. Gene expression analysis on the effects of TP359 on outer membrane biogenesis genes underscored marked down-regulation, particularly of oprF, which encodes a major structural and outer membrane porin (OprF) in both strains studied, indicating that the peptide may cause deregulation of outer membrane genes and reduced structural stability which could lead to cell death. CONCLUSION: Our data shows that TP359 has potent antimicrobial activity against P aeruginosa. The correlation between membrane damage, depolarization and reduced expression of outer membrane biogenesis genes, particularly oprF may suggest the bactericidal mechanism of action of the TP359 peptide.

Silver-coated carbon nanotubes downregulate the expression of Pseudomonas aeruginosa virulence genes: a potential mechanism for their antimicrobial effect.

The antimicrobial activity of silver-coated carbon nanotubes (AgCNTs) and their potential mode of action against mucoid and nonmucoid strains of Pseudomonas aeruginosa was investigated in vitro. The results showed that AgCNTs exhibited antimicrobial activity against both strains with minimum inhibitory concentrations of approximately 8 µg/mL, indicating a high sensitivity of P. aeruginosa to AgCNTs. AgCNTs were also bactericidal against both strains at the same minimum inhibitory concentration. Scanning and transmission electron-microscopy studies further revealed that a majority of the cells treated with AgCNTs transformed from smooth rod-shape morphology to disintegrated cells with broken/damaged membranes, resulting in leakage of cytoplasmic contents to produce ghost cells. The molecular effects of AgCNTs on P. aeruginosa genes involved in virulence and pathogenicity, stress response, and efflux pumps were evaluated for changes in their expression. Quantitative real-time PCR (qRT-PCR) showed that after exposure to AgCNTs, the expression levels of the rpoS, rsmZ, and oprD genes were significantly downregulated in both strains of P. aeruginosa compared to the untreated samples. These results suggest that the mechanism of action of AgCNTs may be attributed to their effect on cell-membrane integrity, downregulation of virulence-gene expression, and induction of general and oxidative stress in P. aeruginosa.

Novel pegylated silver coated carbon nanotubes kill Salmonella but they are non-toxic to eukaryotic cells.

BACKGROUND: Resistance of food borne pathogens such as Salmonella to existing antibiotics is of grave concern. Silver coated single walled carbon nanotubes (SWCNTs-Ag) have broad-spectrum antibacterial activity and may be a good treatment alternative. However, toxicity to human cells due to their physico-chemical properties is a serious public health concern. Although pegylation is commonly used to reduce metal nanoparticle toxicity, SWCNTs-Ag have not been pegylated as yet, and the effect of pegylation of SWCNTs-Ag on their anti-bacterial activity and cell cytotoxicity remains to be studied. Further, there are no molecular studies on the anti-bacterial mechanism of SWCNTs-Ag or their functionalized nanocomposites. MATERIALS AND METHODS: In this study we created novel pegylated SWCNTS-Ag (pSWCNTs-Ag), and employed 3 eukaryotic cell lines to evaluate their cytotoxicity as compared to plain SWCNTS-Ag. Simultaneously, we evaluated their antibacterial activity on Salmonella enterica serovar Typhimurium (Salmonella Typhimurium) by the MIC and growth curve assays. In order to understand the possible mechanisms of action of both SWCNTs-Ag and pSWCNTs-Ag, we used electron microscopy (EM) and molecular studies (qRT-PCR). RESULTS: pSWCNTs-Ag inhibited Salmonella Typhimurium at 62.5 µg/mL, while remaining non-toxic to human cells. By comparison, plain SWCNTs-Ag were toxic to human cells at 62.5 µg/mL. EM analysis revealed that bacteria internalized either of these nanocomposites after the outer cell membranes were damaged, resulting in cell lysis or expulsion of cytoplasmic contents, leaving empty ghosts. The expression of genes regulating the membrane associated metabolic transporter system (artP, dppA, and livJ), amino acid biosynthesis (trp and argC) and outer membrane integrity (ompF) protiens, was significantly down regulated in Salmonella treated with both pSWCNTs-Ag and SWCNTs-Ag. Although EM analysis of bacteria treated with either SWCNTs-Ag or pSWCNTs-Ag revealed relatively similar morphological changes, the expression of genes regulating the normal physiological processes of bacteria (ybeF), quorum sensing (sdiA), outer membrane structure (safC), invasion (ychP) and virulence (safC, ychP, sseA and sseG) were exclusively down regulated several fold in pSWCNTs-Ag treated bacteria. CONCLUSIONS: Altogether, the present data shows that our novel pSWCNTs-Ag are non-toxic to human cells at their bactericidal concentration, as compared to plain SWCNTS-Ag. Therefore, pSWCNTs-Ag may be safe alternative antimicrobials to treat foodborne pathogens.