Transcriptional events during the recovery from MRSA lung infection: a mouse pneumonia model

Effects of low-frequency ultrasound combined with anti-MRSA agents on the mouse model of pulmonary infection

The treatment of methicillin-resistant Staphylococcus aureus (MRSA)-induced pneumonia with antibiotics alone poses considerable challenges. To address these challenges, low-frequency ultrasound (LFU) emerges as a promising approach. In this study, a mouse pneumonia model was established through intratracheal injection of MRSA to investigate the therapeutic efficacy of LFU in combination with antibiotics. Minimal inhibitory concentration was assessed, and the distribution of antibiotics in the lung and plasma was determined using liquid chromatography coupled with mass spectrometry. Various parameters, including the survival rate, histopathology, lung bacterial clearance, and the expressions of cytokines and inflammation-related genes, were evaluated before and after treatment. Compared with the infection group, both the antibiotic-alone groups [vancomycin (VCM), linezolid, and contezolid (CZD)] and the groups in combination with LFU demonstrated an improvement in the survival status of mice. The average colony-forming units of lung tissue in the LFU combination groups were lower compared with the antibiotic-alone groups. While no significant changes in C-reactive protein and procalcitonin in plasma and bronchoalveolar lavage fluid were observed, histopathological results revealed reduced inflammatory damage in LFU combination groups. The secretion of interleukin-6 and tumor necrosis factor-alpha was decreased by the combination treatment, particularly in the VCM + LFU group. Furthermore, the expressions of MRSA virulence factors (hla and agrA) and inflammation-related genes (Saa3, Cxcl9, and Orm1) were further reduced by the combinations of LFU and antibiotics. Additionally, LFU treatment facilitated the distribution of VCM and CZD in mouse lung tissue at 30 and 45 min, respectively, after dosage.IMPORTANCETreating pneumonia caused by methicillin-resistant Staphylococcus aureus (MRSA) with antibiotics alone poses significant challenges. In this in vivo study, we present compelling evidence supporting the efficacy of low-frequency ultrasound (LFU) as a promising approach to overcome these obstacles. Our findings demonstrated that LFU enhanced the effectiveness of vancomycin, linezolid, and contezolid in an MRSA pneumonia model. The combination of LFU with anti-MRSA agents markedly improved the survival rate of mice, accelerated the clearance of pulmonary bacteria, reduced inflammatory injury, inhibited the production of MRSA endotoxin, and enhanced the distribution of antibiotics in lung tissue. The application of LFU in the treatment of pulmonary infections held substantial significance. We believe that readers of your journal will find this topic of considerable interest.

Antibiotic resistance and drug modification: Synthesis, characterization and bioactivity of newly modified potent pleuromutilin derivatives with a substituted piperazine moiety

Antibiotic-resistant bacteria pose a major global public health concern, owing to the lack of effective antibacterial drugs. Consequently, the discovery and development of innovative antibacterial drug classes with unique mechanisms of action are urgently needed. In this study, we designed, synthesised, and tested a series of novel pleuromutilin derivatives with piperazine linker substituted by amino acids moieties to determine their antibacterial properties. Most synthesized compounds exhibited potent activities against Staphylococcus aureus (S. aureus), methicillin-resistant S. aureus (MRSA), and methicillin-resistant Staphylococcus epidermidis. Compound 6l, the most potent antibacterial agent created in this study, displayed a rapid bactericidal activity against MRSA, Klebsiella pneumoniae and S. aureus cfr N12. Moreover, pharmacokinetics study of compound 6l exhibited good PK performance with a low in vivo clearance (CL = 1965 mL/h/kg) and a suitable half-life (T_1/2 = 11.614 ± 5.123 h). Molecular docking experiments revealed the binding model of compound 6l to the unmethylated A2503 of peptidyl transferase centre of 23S rRNA. Interaction pattern of 6l with cfr-mediated ribosomes revealed by molecular dynamics. Moreover in vivo mouse systemic infection experiments with compound 6l revealed its effectiveness against MRSA and S. aureus cfr N12 with the ED₅₀ of 11.08 mg/kg and 14.63 mg/kg body weight, respectively.

Identification of Transcriptome Biomarkers for Severe COVID-19 with Machine Learning Methods

The rapid spread of COVID-19 has become a major concern for people's lives and health all around the world. COVID-19 patients in various phases and severity require individualized treatment given that different patients may develop different symptoms. We employed machine learning methods to discover biomarkers that may accurately classify COVID-19 in various disease states and severities in this study. The blood gene expression profiles from 50 COVID-19 patients without intensive care, 50 COVID-19 patients with intensive care, 10 non-COVID-19 individuals without intensive care, and 16 non-COVID-19 individuals with intensive care were analyzed. Boruta was first used to remove irrelevant gene features in the expression profiles, and then, the minimum redundancy maximum relevance was applied to sort the remaining features. The generated feature-ranked list was fed into the incremental feature selection method to discover the essential genes and build powerful classifiers. The molecular mechanism of some biomarker genes was addressed using recent studies, and biological functions enriched by essential genes were examined. Our findings imply that genes including UBE2C, PCLAF, CDK1, CCNB1, MND1, APOBEC3G, TRAF3IP3, CD48, and GZMA play key roles in defining the different states and severity of COVID-19. Thus, a new point of reference is provided for understanding the disease's etiology and facilitating a precise therapy.

MRSA-induced endothelial permeability and acute lung injury are attenuated by FTY720 S-phosphonate

Disruption of the lung endothelial barrier is a hallmark of acute respiratory distress syndrome (ARDS), for which no effective pharmacologic treatments exist. Prior work has demonstrated that FTY720 S-phosphonate (Tys), an analog of sphingosine-1-phosphate (S1P) and FTY720, exhibits potent endothelial cell (EC) barrier protective properties. In this study, we investigated the in vitro and in vivo efficacy of Tys against methicillin-resistant Staphylococcus aureus (MRSA), a frequent bacterial cause of ARDS. Tys-protected human lung EC from barrier disruption induced by heat-killed MRSA (HK-MRSA) or staphylococcal α-toxin and attenuated MRSA-induced cytoskeletal changes associated with barrier disruption, including actin stress fiber formation and loss of peripheral VE-cadherin and cortactin. Tys-inhibited Rho and myosin light chain (MLC) activation after MRSA and blocked MRSA-induced NF-κB activation and release of the proinflammatory cytokines, IL-6 and IL-8. In vivo, intratracheal administration of live MRSA in mice caused significant vascular leakage and leukocyte infiltration into the alveolar space. Pre- or posttreatment with Tys attenuated MRSA-induced lung permeability and levels of alveolar neutrophils. Posttreatment with Tys significantly reduced levels of bronchoalveolar lavage (BAL) VCAM-1 and plasma IL-6 and KC induced by MRSA. Dynamic intravital imaging of mouse lungs demonstrated Tys attenuation of HK-MRSA-induced interstitial edema and neutrophil infiltration into lung tissue. Tys did not directly inhibit MRSA growth or viability in vitro. In conclusion, Tys inhibits lung EC barrier disruption and proinflammatory signaling induced by MRSA in vitro and attenuates acute lung injury induced by MRSA in vivo. These results support the potential utility of Tys as a novel ARDS therapeutic strategy.

IL-33-mediated Eosinophilia Protects against Acute Lung Injury

Pneumonia-induced lung injury and acute respiratory distress syndrome can develop because of an inappropriate inflammatory response to acute infections, leading to a compromised alveolar barrier. Recent work suggests that hospitalized patients with allergies/asthma are less likely to die of pulmonary infections and that there is a correlation between survival from acute respiratory distress syndrome and higher eosinophil counts; thus, we hypothesized that eosinophils associated with a type 2 immune response may protect against pneumonia-induced acute lung injury. To test this hypothesis, mice were treated with the type 2–initiating cytokine IL-33 intratracheally 3 days before induction of pneumonia with airway administration of a lethal dose of Staphylococcus aureus. Interestingly, IL-33 pretreatment promoted survival by inhibiting acute lung injury: amount of BAL fluid proinflammatory cytokines and pulmonary edema were both reduced, with an associated increase in oxygen saturation. Pulmonary neutrophilia was also reduced, whereas eosinophilia was strongly increased. This eosinophilia was key to protection; eosinophil reduction eliminated both IL-33–mediated protection against mortality and inhibition of neutrophilia and pulmonary edema. Together, these data reveal a novel role for eosinophils in protection against lung injury and suggest that modulation of pulmonary type 2 immunity may represent a novel therapeutic strategy.

Group V Phospholipase A2 Mediates Endothelial Dysfunction and Acute Lung Injury Caused by Methicillin-Resistant Staphylococcus Aureus

Lung endothelial dysfunction is a key feature of acute lung injury (ALI) and clinical acute respiratory distress syndrome (ARDS). Previous studies have identified the lipid-generating enzyme, group V phospholipase A2 (gVPLA2), as a mediator of lung endothelial barrier disruption and inflammation. The current study aimed to determine the role of gVPLA2 in mediating lung endothelial responses to methicillin-resistant Staphylococcus aureus (MRSA, USA300 strain), a major cause of ALI/ARDS. In vitro studies assessed the effects of gVPLA2 inhibition on lung endothelial cell (EC) permeability after exposure to heat-killed (HK) MRSA. In vivo studies assessed the effects of intratracheal live or HK-MRSA on multiple indices of ALI in wild-type (WT) and gVPLA2-deficient (KO) mice. In vitro, HK-MRSA increased gVPLA2 expression and permeability in human lung EC. Inhibition of gVPLA2 with either the PLA2 inhibitor, LY311727, or with a specific monoclonal antibody, attenuated the barrier disruption caused by HK-MRSA. LY311727 also reduced HK-MRSA-induced permeability in mouse lung EC isolated from WT but not gVPLA2-KO mice. In vivo, live MRSA caused significantly less ALI in gVPLA2 KO mice compared to WT, findings confirmed by intravital microscopy assessment in HK-MRSA-treated mice. After targeted delivery of gVPLA2 plasmid to lung endothelium using ACE antibody-conjugated liposomes, MRSA-induced ALI was significantly increased in gVPLA2-KO mice, indicating that lung endothelial expression of gVPLA2 is critical in vivo. In summary, these results demonstrate an important role for gVPLA2 in mediating MRSA-induced lung EC permeability and ALI. Thus, gVPLA2 may represent a novel therapeutic target in ALI/ARDS caused by bacterial infection.

Cigarette Smoke and Nicotine-Containing Electronic-Cigarette Vapor Downregulate Lung WWOX Expression, Which Is Associated with Increased Severity of Murine Acute Respiratory Distress Syndrome

A history of chronic cigarette smoking is known to increase risk for acute respiratory distress syndrome (ARDS), but the corresponding risks associated with chronic e-cigarette use are largely unknown. The chromosomal fragile site gene, WWOX, is highly susceptible to genotoxic stress from environmental exposures and thus an interesting candidate gene for the study of exposure-related lung disease. Lungs harvested from current versus former/never-smokers exhibited a 47% decrease in WWOX mRNA levels. Exposure to nicotine-containing e-cigarette vapor resulted in an average 57% decrease in WWOX mRNA levels relative to vehicle-treated controls. In separate studies, endothelial (EC)-specific WWOX knockout (KO) versus WWOX flox control mice were examined under ARDS-producing conditions. EC WWOX KO mice exhibited significantly greater levels of vascular leak and histologic lung injury. ECs were isolated from digested lungs of untreated EC WWOX KO mice using sorting by flow cytometry for CD31+ CD45-cells. These were grown in culture, confirmed to be WWOX deficient by RT-PCR and Western blotting, and analyzed by electric cell impedance sensing as well as an FITC dextran transwell assay for their barrier properties during methicillin-resistant Staphylococcus aureus or LPS exposure. WWOX KO ECs demonstrated significantly greater declines in barrier function relative to cells from WWOX flox controls during either methicillin-resistant S. aureus or LPS treatment as measured by both electric cell impedance sensing and the transwell assay. The increased risk for ARDS observed in chronic smokers may be mechanistically linked, at least in part, to lung WWOX downregulation, and this phenomenon may also manifest in the near future in chronic users of e-cigarettes.

Genomic and functional analysis of the host response to acute simian varicella infection in the lung

Varicella Zoster Virus (VZV) is the causative agent of varicella and herpes zoster. Although it is well established that VZV is transmitted via the respiratory route, the host-pathogen interactions during acute VZV infection in the lungs remain poorly understood due to limited access to clinical samples. To address these gaps in our knowledge, we leveraged a nonhuman primate model of VZV infection where rhesus macaques are intrabronchially challenged with the closely related Simian Varicella Virus (SVV). Acute infection is characterized by immune infiltration of the lung airways, a significant up-regulation of genes involved in antiviral-immunity, and a down-regulation of genes involved in lung development. This is followed by a decrease in viral loads and increased expression of genes associated with cell cycle and tissue repair. These data provide the first characterization of the host response required to control varicella virus replication in the lung and provide insight into mechanisms by which VZV infection can cause lung injury in an immune competent host.

Omics Approaches for the Study of Adaptive Immunity to Staphylococcus aureus and the Selection of Vaccine Candidates

Staphylococcus aureus is a dangerous pathogen both in hospitals and in the community. Due to the crisis of antibiotic resistance, there is an urgent need for new strategies to combat S. aureus infections, such as vaccination. Increasing our knowledge about the mechanisms of protection will be key for the successful prevention or treatment of S. aureus invasion. Omics technologies generate a comprehensive picture of the physiological and pathophysiological processes within cells, tissues, organs, organisms and even populations. This review provides an overview of the contribution of genomics, transcriptomics, proteomics, metabolomics and immunoproteomics to the current understanding of S. aureus‑host interaction, with a focus on the adaptive immune response to the microorganism. While antibody responses during colonization and infection have been analyzed in detail using immunoproteomics, the full potential of omics technologies has not been tapped yet in terms of T-cells. Omics technologies promise to speed up vaccine development by enabling reverse vaccinology approaches. In consequence, omics technologies are powerful tools for deepening our understanding of the “superbug” S. aureus and for improving its control.

Evolution of resistance to a last-resort antibiotic in Staphylococcus aureus via bacterial competition

Antibiotic resistance is a key medical concern, with antibiotic use likely being an important cause. However, here we describe an alternative route to clinically relevant antibiotic resistance that occurs solely due to competitive interactions among bacterial cells. We consistently observe that isolates of Methicillin-resistant Staphylococcus aureus diversify spontaneously into two distinct, sequentially arising strains. The first evolved strain outgrows the parent strain via secretion of surfactants and a toxic bacteriocin. The second is resistant to the bacteriocin. Importantly, this second strain is also resistant to intermediate levels of vancomycin. This so-called VISA (vancomycin-intermediate S. aureus) phenotype is seen in many hard-to-treat clinical isolates. This strain diversification also occurs during in vivo infection in a mouse model, which is consistent with the fact that both coevolved phenotypes resemble strains commonly found in clinic. Our study shows how competition between coevolving bacterial strains can generate antibiotic resistance and recapitulate key clinical phenotypes.

The accessory gene regulator (agr) controls Staphylococcus aureus virulence in a murine intracranial abscesses model

Background

Intracranial abscesses are associated with high mortality. Staphylococcus aureus is one of the main pathogens that cause intracranial infection. Until now, there is no report to identify the key effectors of S. aureus during the intracranial infection.

Methods

The murine intracranial abscesses model induced by S. aureus was constructed. The vital sign and survival rate of mice were observed to evaluate the infection. Histological examination was used to diagnose the pathological alterations of mouse tissues. The sensitivity of S. aureus to whole blood was evaluated by whole-blood killing assay.

Results

In murine intracranial abscesses model, it was shown that the mortality caused by the accessory gene regulator (agr) locus deficient strain was significant decreased compared with its parent strain. Moreover, we found that RNAIII, the effector of agr system, was essential for the intracranial infection caused by S. aureus. In the further investigation, it was shown that restoration the expression of α-toxin in agr deficient strain could partially recover the mortality in the murine intracranial abscesses model.

Conclusion

Our data suggested that the agr system of S. aureus is an important virulence determinant in the induction and mortality of intracranial abscesses in mice.