Label-Free Quantitative Proteomics Distinguishes General and Site-Specific Host Responses to Pseudomonas aeruginosa Infection at the Ocular Surface

Quantitative proteomics reveals unique responses to antimicrobial treatments in clinical Pseudomonas aeruginosa isolates

IMPORTANCE

Pseudomonas aeruginosa is an important pathogen often associated with hospital-acquired infections and chronic lung infections in people with cystic fibrosis. P. aeruginosa possesses a wide array of intrinsic and adaptive mechanisms of antibiotic resistance, and the regulation of these mechanisms is complex. Label-free quantitative proteomics is a powerful tool to compare susceptible and resistant strains of bacteria and their responses to antibiotic treatments. Here we compare the proteomes of three isolates of P. aeruginosa with different antibiotic resistance profiles in response to five challenge conditions. We uncover unique and shared proteome changes for the widely used laboratory strain PAO1 and two isolates of the Liverpool epidemic strain of P. aeruginosa, LESlike1 and LESB58. Our data set provides insight into antibiotic resistance in clinically relevant Pseudomonas isolates and highlights proteins, including those with uncharacterized functions, which can be further investigated for their role in adaptive responses to antibiotic treatments.

Bone protein analysis via label-free quantitative proteomics in patients with periprosthetic joint infection

Periprosthetic joint infection (PJI) is a catastrophic complication of arthroplasty. The treatment of PJI often requires multiple operations and long-term use of antibiotics, making PJI a substantial health and economic burden for patients. Therefore, there is an urgent need to elucidate the pathological mechanism of PJI to explore new therapeutic methods. This study aimed to explore proteomics changes in bone tissue around the prosthesis during PJI development, to explain the pathological mechanism and to provide new treatment ideas. Ten patients who underwent revision surgery at our institution were included: 5 patients with Staphylococcus aureus PJI and 5 patients with aseptic failure. The proteomics changes in bone tissues after PJI were investigated by label-free quantitative proteomics, and the pathways affected by the differential proteins were analyzed by GO annotation, GO enrichment analysis, KEGG enrichment analysis and protein-protein interaction network analysis. We identified 435 differentially expressed proteins (DEPs), with 213 upregulated and 222 downregulated proteins. Analysis revealed activation of immune-related pathways, such as complement and coagulation cascades, phagocytosis, and neutrophil activation, and inhibition of energy metabolism pathways represented by the TCA cycle. We also observed an altered balance between osteoblasts and osteoclasts during S. aureus PJI. We hope that these processes will reveal new treatment ideas. SIGNIFICANCE: PJI is a catastrophic complication of arthroplasty. When infection occurs, bacteria may invade periprosthetic bone tissue to escape immunity and cause damage. So far, only few studies focused on the changes of proteomics associated to PJI. This is the first study to describe the proteomics changes of periprosthetic bone tissue of patients with PJI. We found that the pathological process of S. aureus PJI mainly involves activation of the immune system, decreased energy metabolism, and an altered balance of osteoblasts and osteoclasts.

Quantitative Proteomic Profiling of Murine Ocular Tissue and the Extracellular Environment

Mass spectrometry-based proteomics provides a robust and reliable method for detecting and quantifying changes in protein abundance among samples, including cells, tissues, organs, and supernatants. Physical damage or inflammation can compromise the ocular surface permitting colonization by bacterial pathogens, commonly Pseudomonas aeruginosa, and the formation of biofilms. The interplay between P. aeruginosa and the immune system at the site of infection defines the host's ability to defend against bacterial invasion and promote clearance of infection. Profiling of the ocular tissue following infection describes the nature of the host innate immune response and specifically the presence and abundance of neutrophil-associated proteins to neutralize the bacterial biofilm. Moreover, detection of unique proteins produced by P. aeruginosa enable identification of the bacterial species and may serve as a diagnostic approach in a clinical setting. Given the emergence and prevalence of antimicrobial resistant bacterial strains, the ability to rapidly diagnose a bacterial infection promoting quick and accurate treatment will reduce selective pressure towards resistance. Furthermore, the ability to define differences in the host immune response towards bacterial invasion enhances our understanding of innate immune system regulation at the ocular surface. Here, we describe murine ocular infection and sample collection, as well as outline protocols for protein extraction and mass spectrometry profiling from corneal tissue and extracellular environment (eye wash) samples. © 2020 Wiley Periodicals LLC. Basic Protocol 1: Murine model of ocular infection Basic Protocol 2: Murine model sample collection Basic Protocol 3: Protein extraction from eye wash Basic Protocol 4: Protein extraction from corneal tissue Basic Protocol 5: Mass spectrometry-based proteomics and bioinformatics from eye wash and corneal tissue samples.

Corneal Infection Models: Tools to Investigate the Role of Biofilms in Bacterial Keratitis

Bacterial keratitis is a corneal infection which may cause visual impairment or even loss of the infected eye. It remains a major cause of blindness in the developing world. Staphylococcus aureus and Pseudomonas aeruginosa are common causative agents and these bacterial species are known to colonise the corneal surface as biofilm populations. Biofilms are complex bacterial communities encased in an extracellular polymeric matrix and are notoriously difficult to eradicate once established. Biofilm bacteria exhibit different phenotypic characteristics from their planktonic counterparts, including an increased resistance to antibiotics and the host immune response. Therefore, understanding the role of biofilms will be essential in the development of new ophthalmic antimicrobials. A brief overview of biofilm-specific resistance mechanisms is provided, but this is a highly multifactorial and rapidly expanding field that warrants further research. Progression in this field is dependent on the development of suitable biofilm models that acknowledge the complexity of the ocular environment. Abiotic models of biofilm formation (where biofilms are studied on non-living surfaces) currently dominate the literature, but co-culture infection models are beginning to emerge. In vitro, ex vivo and in vivo corneal infection models have now been reported which use a variety of different experimental techniques and animal models. In this review, we will discuss existing corneal infection models and their application in the study of biofilms and host-pathogen interactions at the corneal surface.

Proteomics of host-bacterial interactions: new insights from dual perspectives

Mass-spectrometry (MS)-based proteomics is a powerful and robust platform for studying the interactions between biological systems during health and disease. Bacterial infections represent a significant threat to global health and drive the pursuit of novel therapeutic strategies to combat emerging and resistant pathogens. During infection, the interplay between a host and pathogen determines the ability of the microbe to survive in a hostile environment and promotes an immune response by the host as a protective measure. It is the protein-level changes from either biological system that define the outcome of infection, and MS-based proteomics provides a rapid and effective platform to identify such changes. In particular, proteomics detects alterations in protein abundance, quantifies protein secretion and (or) release, measures an array of post-translational modifications that influence signaling cascades, and profiles protein-protein interactions through protein complex and (or) network formation. Such information provides new insight into the role of known and novel bacterial effectors, as well as the outcome of host cell activation. In this Review, we highlight the diverse applications of MS-based proteomics in profiling the relationship between bacterial pathogens and the host. Our work identifies a plethora of strategies for exploring mechanisms of infection from dual perspectives (i.e., host and pathogen), and we suggest opportunities to extrapolate the current knowledgebase to other biological systems for applications in therapeutic discovery.

Exoproteomics for Better Understanding Pseudomonas aeruginosa Virulence

Pseudomonas aeruginosa is the most common human opportunistic pathogen associated with nosocomial diseases. In 2017, the World Health Organization has classified P. aeruginosa as a critical agent threatening human health, and for which the development of new treatments is urgently necessary. One interesting avenue is to target virulence factors to understand P. aeruginosa pathogenicity. Thus, characterising exoproteins of P. aeruginosa is a hot research topic and proteomics is a powerful approach that provides important information to gain insights on bacterial virulence. The aim of this review is to focus on the contribution of proteomics to the studies of P. aeruginosa exoproteins, highlighting its relevance in the discovery of virulence factors, post-translational modifications on exoproteins and host-pathogen relationships.

Optimization of inhalable liposomal powder formulations and evaluation of their in vitro drug delivery behavior in Calu-3 human lung epithelial cells

Inhalation therapy has advantages for the treatment of multidrug resistant bacterial lung infections with high drug concentrations at the infection sites in the airways and reduced systemic exposure. We have developed liposomal formulations for pulmonary delivery of synergistic ciprofloxacin (Cipro) and colistin (Col) as the potential candidate for treatment of lung infections caused by multidrug resistant Gram-negative bacteria. This study aims to: (1) further optimize the powder formulation by adding drying stabilizers (polyvinyl pyrrolidone or poloxamer) to protect the liposomes during spray-freeze-drying; (2) evaluate the transport and cellular uptake of drugs in a human lung epithelial Calu-3 cell model. The liposomal powder formulations were produced using the ultrasonic spray-freeze-drying technique. The optimal formulation (F5) used mannitol (8% w/v) and sucrose (2% w/v) as the internal lyoprotectants. Adding external lyoprotectants/aerosolization enhancers (i.e. 8% w/v mannitol, 2% w/v sucrose and 1%, w/w PVP 10) produced the superior rehydrated EE values of ciprofloxacin and colistin (50.2 ± 0.9% for Cipro and 37.8 ± 1.2% for Col) as well as satisfactory aerosol performance (FPF: 34.2 ± 0.8% for Cipro and 33.6 ± 0.9% for Col). The cytotoxicity study indicated that F5 with the colistin concentration at 50 μg/mL and ciprofloxacin at 200 μg/mL was not cytotoxic to human lung epithelial Calu-3 cells. The intracellular uptake of ciprofloxacin was concentration-dependent in Calu-3 cells and the uptake of A-B was more than that of B-A for all samples (p < 0.05). This study demonstrates that co-delivery of ciprofloxacin and colistin in a single liposome can lower the transport capability of both drugs across the Calu-3 cell monolayer and their accumulation in the cells. These findings indicate that co-loaded liposomal powder of ciprofloxacin and colistin is a promising potential treatment for respiratory infections caused by multidrug resistant Gram-negative bacteria.

Ruggedness testing of liquid chromatography-tandem mass spectrometry system components using microbiome-relevant methods and matrices

Recently, an opportunity to perform a broad ruggedness assessment of our liquid chromatography-tandem mass spectrometry (LC-MS/MS) system presented itself during the analytical planning phase of a large-scale human fecal microbiome study. The specific aim of this project was to study the microbial-mediated metabolism of a targeted set of bile acids/salts by mixed bacterial communities cultured from the feces of 12 healthy volunteers when grown in a custom growth medium and following exposure to different clinically-relevant antibiotics. The magnitude of this study offered a rare opportunity to significantly stress procedures and LC-MS/MS system components comprised in our bile acid/salt targeted metabolomics method. With this second specific aim in mind, we modified the sample analysis plan to include a series of figure-of-merit (FoM)-based tests that are commonly used in regulated bioanalytical labs to assess LC and MS system ruggedness for a specific assay - these FoM-based testing parameters were monitored continuously over the course of sample analysis and the results are presented in this report. In total, the assessment included 1206 sequential injections (180 calibration standards, 136 blank-internal standard samples, and 890 diluted medium samples) that took place over 8-days. Completion of the 8-days of non-stop sample analysis revealed no critical hardware or software failures, and the analysis of the FoM-based tests indicated no observable degradation of system performance over the number of samples and time tested. The FoM-based test metrics presented may be used as a template to assess the ruggedness of any LC-MS/MS-based targeted metabolomics workflow.