Gram-Positive Pneumonia

Disposable Peptidoglycan-Specific Biosensor for Noninvasive Real-Time Detection of Broad-Spectrum Gram-Positive Bacteria in Exhaled Breath Condensates

Rapidly identifying and quantifying Gram-positive bacteria are crucial to diagnosing and treating bacterial lower respiratory tract infections (LRTIs). This work presents a field-deployable biosensor for detecting Gram-positive bacteria from exhaled breath condensates (EBCs) based on peptidoglycan recognition using an aptamer. Dielectrophoretic force is employed to enrich the bacteria in 10 s without additional equipment or steps. Concurrently, the measurement of the sensor's interfacial capacitance is coupled to quantify the bacteria during the enrichment process. By incorporation of a semiconductor condenser, the whole detection process, including EBC collection, takes about 3 min. This biosensor has a detection limit of 10 CFU/mL, a linear range of up to 105 CFU/mL and a selectivity of 1479:1. It is cost-effective and disposable due to its low cost. The sensor provides a nonstaining, culture-free and PCR-independent solution for noninvasive and real-time diagnosis of Gram-positive bacterial LRTIs.

Gene expression analysis for pneumonia caused by Gram-positive bacterial infection

Gram-positive bacteria are an important pathogenic factor for bacterial pneumonia. The aim of the present study was to identify the differentially expressed genes (DEGs) and to explore their associated pathways or expression patterns. Expression profiling of gene arrays from two independent datasets, GSE6269 and GSE35716, were downloaded from the Gene Expression Omnibus. The DEGs between peripheral blood samples from healthy controls and patients with bacterial pneumonia were identified. The Functional Annotation Tool in the Database for Annotation, Visualization and Integrated Discovery was used to annotate and analyze the DEGs in Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Multiple proteins were used to generate a protein-protein interaction (PPI) network. A total of 624 (621 annotated) were identified in the GSE6269 dataset and 398 (295 annotated) DEGs were identified in the GSE35716 dataset between pneumonia and healthy samples. A total of 40 common DEGs were identified between the 2 datasets, including 4 downregulated and 32 upregulated DEGs. In the GO category cellular component, melanosome was highly enriched among 11 genes; in the category biological process, the three most enriched items were regulation of ruffle assembly, negative regulation of calcium ion transport and necroptotic process. In the KEGG terms, only the nuclear factor-κB signaling pathway (Homo sapiens 04064) was significantly enriched. In the PPI network, five genes (CCL4, TIMP metallopeptidase inhibitor 1, intercellular adhesion molecule 1, plasminogen activator, urokinase receptor and cathepsin B) were identified to have a high degree of interaction with other DEGs. In conclusion, these five genes may represent key genes associated with pneumonia caused by Gram-positive bacteria. All of these results provide primary information and basic knowledge to understand the mechanisms of the pathogenesis.

Staphylococcus aureus infections: epidemiology, pathophysiology, clinical manifestations, and management

Staphylococcus aureus is a major human pathogen that causes a wide range of clinical infections. It is a leading cause of bacteremia and infective endocarditis as well as osteoarticular, skin and soft tissue, pleuropulmonary, and device-related infections. This review comprehensively covers the epidemiology, pathophysiology, clinical manifestations, and management of each of these clinical entities. The past 2 decades have witnessed two clear shifts in the epidemiology of S. aureus infections: first, a growing number of health care-associated infections, particularly seen in infective endocarditis and prosthetic device infections, and second, an epidemic of community-associated skin and soft tissue infections driven by strains with certain virulence factors and resistance to β-lactam antibiotics. In reviewing the literature to support management strategies for these clinical manifestations, we also highlight the paucity of high-quality evidence for many key clinical questions.

E3 ligase subunit Fbxo15 and PINK1 kinase regulate cardiolipin synthase 1 stability and mitochondrial function in pneumonia

Acute lung injury (ALI) is linked to mitochondrial injury, resulting in impaired cellular oxygen utilization; however, it is unknown how these events are linked on the molecular level. Cardiolipin, a mitochondrial-specific lipid, is generated by cardiolipin synthase (CLS1). Here, we show that S. aureus activates a ubiquitin E3 ligase component, Fbxo15, that is sufficient to mediate proteasomal degradation of CLS1 in epithelia, resulting in decreased cardiolipin availability and disrupted mitochondrial function. CLS1 is destabilized by the phosphatase and tensin homolog (PTEN)-induced putative kinase 1 (PINK1), which binds CLS1 to phosphorylate and regulates CLS1 disposal. Like Fbxo15, PINK1 interacts with and regulates levels of CLS1 through a mechanism dependent upon Thr219. S. aureus infection upregulates this Fbxo15-PINK1 pathway to impair mitochondrial integrity, and Pink1 knockout mice are less prone to S. aureus-induced ALI. Thus, ALI-associated disruption of cellular bioenergetics involves bioeffectors that utilize a phosphodegron to elicit ubiquitin-mediated disposal of a key mitochondrial enzyme.