The remarkably multifunctional fibronectin binding proteins of Staphylococcus aureus

Cutibacterium acnes invades submicron osteocyte lacuno-canalicular networks following implant-associated osteomyelitis

Cutibacterium acnes, part of normal skin flora, is increasingly recognized as an opportunistic pathogen capable of causing chronic prosthetic joint infections (PJI) associated with total hip and knee arthroplasty. However, there is a paucity of literature examining the pathogenesis of C. acnes during PJI. To study this, we developed an implant-associated osteomyelitis murine model in which 8-10-week-old C57BL6 mice were subjected to transtibial implantation of titanium or stainless-steel L-shaped pins contaminated with C. acnes. Postsurgery, mice were killed on Days 14 and 28 for terminal assessments of (1) bacterial load in bone, implant, and internal organs (heart, spleen, kidney, and liver), (2) bone osteolysis (micro-CT), (3) abscess formation (histology), and (4) systematic electron microscopy (EM). In vitro scanning EM (SEM) confirmed that C. acnes can form biofilms on stainless-steel and titanium implants. In mice, C. acnes could persist for 28 days in the tibia. Also, we observed C. acnes dissemination to internal organs. C. acnes chronic osteomyelitis revealed markedly reduced bone osteolysis and abscess formation compared to Staphylococcus aureus infections. Importantly, transmission EM (TEM) investigation revealed the presence of C. acnes within canaliculi, demonstrating that C. acnes can invade the osteocyte lacuno-canalicular networks (OLCN) within bone. Our preliminary pilot study, for the first time, revealed that the OLCN in bone can be a reservoir for C. acnes and potentially provides a novel mechanism of why C. acnes chronic implant-associated bone infections are difficult to treat.

Genomic evolution of ST228 SCCmec-I MRSA 10 years after a major nosocomial outbreak

In this study, we investigated the genomic changes in a major methicillin-resistant Staphylococcus aureus (MRSA) clone following a significant outbreak at a hospital. Whole-genome sequencing of MRSA isolates was utilized to explore the genomic evolution of post-outbreak MRSA strains. The epidemicity of the clone declined over time, coinciding with the introduction of multimodal infection control measures. A genome-wide association study (GWAS) identified multiple genes significantly associated with either high or low epidemic success, indicating alterations in mobilome, virulence, and defense mechanisms. Random Forest models pinpointed a gene related to fibrinogen binding as the most influential predictor of epidemicity. The decline of the MRSA clone may be attributed to various factors, including the implementation of new infection control measures, single nucleotide polymorphisms accumulation, and the genetic drift of a given clone. This research underscores the complex dynamics of MRSA clones, emphasizing the multifactorial nature of their evolution. The decline in epidemicity seems linked to alterations in the clone's genetic profile, with a probable shift towards decreased virulence and adaptation to long-term carriage. Understanding the genomic basis for the decline of epidemic clones is crucial to develop effective strategies for their surveillance and management, as well as to gain insights into the evolutionary dynamics of pathogen genomes.

Diclofenac sodium effectively inhibits the biofilm formation of Staphylococcus epidermidis

Staphylococcus epidermidis is an opportunistic pathogen commonly implicated in medical device-related infections. Its propensity to form biofilms not only leads to chronic infections but also exacerbates the issue of antibiotic resistance, necessitating high-dose antimicrobial treatments. In this study, we explored the use of diclofenac sodium, a non-steroidal anti-inflammatory drug, as an anti-biofilm agent against S. epidermidis. In this study, crystal violet staining and confocal laser scanning microscope analysis showed that diclofenac sodium, at subinhibitory concentration (0.4 mM), significantly inhibited biofilm formation in both methicillin-susceptible and methicillin-resistant S. epidermidis isolates. MTT assays demonstrated that 0.4 mM diclofenac sodium reduced the metabolic activity of biofilms by 25.21-49.01% compared to untreated controls. Additionally, the treatment of diclofenac sodium resulted in a significant decrease (56.01-65.67%) in initial bacterial adhesion, a crucial early phase of biofilm development. Notably, diclofenac sodium decreased the production of polysaccharide intercellular adhesin (PIA), a key component of the S. epidermidis biofilm matrix, in a dose-dependent manner. Real-time quantitative PCR analysis revealed that diclofenac sodium treatment downregulated biofilm-associated genes icaA, fnbA, and sigB and upregulated negative regulatory genes icaR and luxS, providing potential mechanistic insights. These findings indicate that diclofenac sodium inhibits S. epidermidis biofilm formation by affecting initial bacterial adhesion and the PIA synthesis. This underscores the potential of diclofenac sodium as a supplementary antimicrobial agent in combating staphylococcal biofilm-associated infections.

Distribution of Nosocomial Pathogens and Antimicrobial Resistance among Patients with Burn Injuries in China: A Comprehensive Research Synopsis and Meta-Analysis

INTRODUCTION

Over the past decade, numerous studies have described the types of pathogens and their antibiotic resistance patterns in patients with burn injuries in China; however, the findings have generally been inconsistent. We conducted a literature search and meta-analysis to summarize the infection spectra and antimicrobial resistance patterns in patients with burn injuries.

METHODS

We searched the PubMed, Embase, Web of Science, China National Knowledge Infrastructure, China Biomedical Literature, Wanfang, and Weipu databases for relevant articles published between January 2010 and December 2023. The DerSimonian-Laird random-effects model was used to estimate the proportions and 95% confidence intervals (CIs) of pathogens among Chinese patients with burn injuries. Meta-regression analyses were performed to explore differences in the proportions of pathogens among different subgroups and their resistance patterns. This study was registered with PROSPERO (CRD42024514386).

RESULTS

The database searches yielded 2017 records; after removing duplicates and conducting initial screening, 219 articles underwent full-text screening. Ultimately, 60 studies comprising a total of 62,819 isolated strains reported the proportions of pathogens in patients with burn injuries and were included in this meta-analysis. Meta-analyses were conducted on 18 types of pathogens. The most common pathogens causing infections in Chinese patients with burn injuries were Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae, and Staphylococcus epidermidis. Similar results were observed in the subgroup analysis focusing on wound infections. Since 2015, there has been a significant decrease in the proportion of Pseudomonas aeruginosa (R2 = 4.89%) and a significant increase in the proportion of Klebsiella pneumoniae (R2 = 9.60%). In terms of antibiotic resistance, there has been a significant decrease in the resistance of Staphylococcus aureus to multiple antibiotics and an increasing trend in the resistance of Klebsiella pneumoniae.

CONCLUSIONS

We systematically summarized the epidemiological characteristics and antibiotic resistance patterns of pathogens among individuals suffering from burns in China, thus providing guidance for controlling wound infections and promoting optimal empirical antimicrobial therapy. The observed high levels of antibiotic resistance underscore the need for ongoing monitoring of antibiotic usage trends.

Staphylococcal superantigen-like protein 3 triggers murine mast cell adhesion by binding to CD43 and augments mast cell activation

Staphylococcus aureus is a noteworthy pathogen in allergic diseases, as four staphylococcal exotoxins activate mast cells, a significant contributor to inflammation, in an IgE-independent manner. Although the adhesion of mast cells is an essential process for their immune responses, only a small number of exotoxins have been reported to affect the process. Here, we demonstrated that staphylococcal superantigen-like (SSL) 3, previously identified as a toll-like receptor 2 agonist, induced the adhesion of murine bone marrow-derived mast cells to culture substratum. SSL3-induced adhesion was mediated by fibronectin in an Arg-Gly-Asp (RGD) sequence-dependent manner, suggesting the integrins were involved in the process. Additionally, SSL3 was found to bind to an anti-adhesive surface protein CD43. SSL3 induced the adhesion of HEK293 cells expressing exogenous CD43, suggesting that CD43 is the target molecule for adhesion induced by SSL3. Evaluation of SSL3-derived mutants showed that the C-terminal region (253-326), specifically T285 and H307, are necessary to induce adhesion. SSL3 augmented the IL-13 production of mast cells in response to immunocomplex and SSL12. These findings reveal a novel function of SSL3, triggering cell adhesion and enhancing mast cell activation. This study would clarify the correlation between S. aureus and allergic diseases such as atopic dermatitis.

Eliminating the invading extracellular and intracellular FnBp+ bacteria from respiratory epithelial cells by autophagy mediated through FnBp-Fn-Integrin α5β1 axis

Background

We previously found that the respiratory epithelial cells could eliminate the invaded group A streptococcus (GAS) through autophagy induced by binding a fibronectin (Fn) binding protein (FnBp) expressed on the surface of GAS to plasma protein Fn and its receptor integrin α5β1 of epithelial cells. Is autophagy initiated by FnBp+ bacteria via FnBp-Fn-Integrin α5β1 axis a common event in respiratory epithelial cells?

Methods

We chose Staphylococcus aureus (S. aureus/S. a) and Listeria monocytogenes (L. monocytogenes/L. m) as representatives of extracellular and intracellular FnBp+ bacteria, respectively. The FnBp of them was purified and the protein function was confirmed by western blot, viable bacteria count, confocal and pull-down. The key molecule downstream of the action axis was detected by IP, mass spectrometry and bio-informatics analysis.

Results

We found that different FnBp from both S. aureus and L. monocytogenes could initiate autophagy through FnBp-Fn-integrin α5β1 axis and this could be considered a universal event, by which host tries to remove invading bacteria from epithelial cells. Importantly, we firstly reported that S100A8, as a key molecule downstream of integrin β1 chain, is highly expressed upon activation of integrin α5β1, which in turn up-regulates autophagy.

Conclusions

Various FnBp from FnBp+ bacteria have the ability to initiate autophagy via FnBp-Fn-Integrin α5β1 axis to promote the removal of invading bacteria from epithelial cells in the presence of fewer invaders. S100A8 is a key molecule downstream of Integrin α5β1 in this autophagy pathway.

Palladium(II) Metal Complex Fabricated Titanium Implant Mitigates Dual-Species Biofilms in Artificial Synovial Fluid

Metallodrugs have a potent application in various medical fields. In the current study, we used a novel Palladium(II) thiazolinyl picolinamide complex that was directly fabricated over the titanium implant to examine its potency in inhibiting dual-species biofilms and exopolysaccharides. Additionally, inhibition of mono- and dual-species biofilms by coated titanium plates in an in vitro joint microcosm was performed. The study was carried out for 7 days by cultivating mono- and dual-species biofilms on titanium plates placed in both growth media and artificial synovial fluid (ASF). By qPCR analysis, the interaction of co-cultured biofilms in ASF and the alteration in gene expression of co-cultured biofilms were studied. Remarkable alleviation of biofilm accumulation and EPS secretion was observed on the coated titanium plates. The effective impairment of biofilms and EPS matrix of biofilms on Pd(II)-E-coated titanium plates were visualized by Scanning Electron Microscopy. Moreover, coated titanium plates improved the adhesion of osteoblast cells, which is crucial for a bone biomaterial. The potential bioactivity of coated plates was also confirmed at the molecular level using qPCR analysis. The stability of coated plates in ASF for 7 days was examined with FESEM-EDAX analysis. Collectively, the present study provided an excellent anti-infective effect on Pd(II)-E-coated titanium plates without affecting their biocompatibility with bone cells.

Host-Bacterium Interaction Mechanisms in Staphylococcus aureus Endocarditis: A Systematic Review

Staphylococci sp. are the most commonly associated pathogens in infective endocarditis, especially within high-income nations. This along with the increasing burden of healthcare, aging populations, and the protracted infection courses, contribute to a significant challenge for healthcare systems. A systematic review was conducted using relevant search criteria from PubMed, Ovid's version of MEDLINE, and EMBASE, and data were tabulated from randomized controlled trials (RCT), observational cohort studies, meta-analysis, and basic research articles. The review was registered with the OSF register of systematic reviews and followed the PRISMA reporting guidelines. Thirty-five studies met the inclusion criteria and were included in the final systematic review. The role of Staphylococcus aureus and its interaction with the protective shield and host protection functions was identified and highlighted in several studies. The interaction between infective endocarditis pathogens, vascular endothelium, and blood constituents was also explored, giving rise to the potential use of antiplatelets as preventative and/or curative agents. Several factors allow Staphylococcus aureus infections to proliferate within the host with numerous promoting and perpetuating agents. The complex interaction with the hosts' innate immunity also potentiates its virulence. The goal of this study is to attain a better understanding on the molecular pathways involved in infective endocarditis supported by S. aureus and whether therapeutic avenues for the prevention and treatment of IE can be obtained. The use of antibiotic-treated allogeneic tissues have marked antibacterial action, thereby becoming the ideal substitute in native and prosthetic valvular infections. However, the development of effective vaccines against S. aureus still requires in-depth studies.

Investigation of Peptidoglycan-Associated Lipoprotein of Acinetobacter baumannii and Its Interaction with Fibronectin To Find Its Therapeutic Potential

Acinetobacter baumannii causes hospital-acquired infections and is responsible for high mortality and morbidity. The interaction of this bacterium with the host is critical in bacterial pathogenesis and infection. Here, we report the interaction of peptidoglycan-associated lipoprotein (PAL) of A. baumannii with host fibronectin (FN) to find its therapeutic potential. The proteome of A. baumannii was explored in the host-pathogen interaction database to filter out the PAL of the bacterial outer membrane that interacts with the host's FN protein. This interaction was confirmed experimentally using purified recombinant PAL and pure FN protein. To investigate the pleiotropic role of PAL protein, different biochemical assays using wild-type PAL and PAL mutants were performed. The result showed that PAL mediates bacterial pathogenesis, adherence, and invasion in host pulmonary epithelial cells and has a role in the biofilm formation, bacterial motility, and membrane integrity of bacteria. All of the results suggest that PAL's interaction with FN plays a vital role in host-cell interaction. In addition, the PAL protein also interacts with Toll-like receptor 2 and MARCO receptor, which suggests the role of PAL protein in innate immune responses. We have also investigated the therapeutic potential of this protein for vaccine and therapeutic design. Using reverse vaccinology, PAL's potential epitopes were filtered out that exhibit binding potential with host major histocompatibility complex class I (MHC-I), MHC-II, and B cells, suggesting that PAL protein is a potential vaccine target. The immune simulation showed that PAL protein could elevate innate and adaptive immune response with the generation of memory cells and would have subsequent potential to eliminate bacterial infection. Therefore, the present study highlights the interaction ability of a novel host-pathogen interacting partner (PAL-FN) and uncovers its therapeutic potential to combat infection caused by A. baumannii.

The Role of Platelets in Infective Endocarditis

Over the last decade, the incidence of infective endocarditis (IE) has increased, with a change in the frequency of causative bacteria. Early evidence has substantially demonstrated the crucial role of bacterial interaction with human platelets, with no clear mechanistic characterization in the pathogenesis of IE. The pathogenesis of endocarditis is so complex and atypical that it is still unclear how and why certain bacterial species will induce the formation of vegetation. In this review, we will analyze the key role of platelets in the physiopathology of endocarditis and in the formation of vegetation, depending on the bacterial species. We provide a comprehensive outline of the involvement of platelets in the host immune response, investigate the latest developments in platelet therapy, and discuss prospective research avenues for solving the mechanistic enigma of bacteria-platelet interaction for preventive and curative medicine.

Staphylococcus aureus Fibronectin-Binding Proteins Contribute to Colonization of the Female Reproductive Tract

Methicillin-resistant Staphylococcus aureus (MRSA) is an opportunistic pathogen and frequent colonizer of human skin and mucosal membranes, including the vagina, with vaginal colonization reaching nearly 25% in some pregnant populations. MRSA vaginal colonization can lead to aerobic vaginitis (AV), and during pregnancy, bacterial ascension into the upper reproductive tract can lead to adverse birth outcomes. USA300, the most prominent MRSA lineage to colonize pregnant individuals, is a robust biofilm former and causative agent of invasive infections; however, little is known about how it colonizes and ascends in the female reproductive tract (FRT). Our previous studies showed that a MRSA mutant of seven fibrinogen-binding adhesins was deficient in FRT epithelial attachment and colonization. Using both monolayer and multilayer air-liquid interface cell culture models, we determine that one class of these adhesins, the fibronectin binding proteins (FnBPA and FnBPB), are critical for association with human vaginal epithelial cells (hVECs) and hVEC invasion through interactions with α₅β₁ integrin. We observe that both FnBPs are important for biofilm formation as single and double fnbAB mutants exhibit reduced biofilm formation on hVECs. Using heterologous expression of fnbA and fnbB in Staphylococcus carnosus, FnBPs are also found to be sufficient for hVEC cellular association, invasion, and biofilm formation. In addition, we found that an ΔfnbAB mutant displays attenuated ascension in our murine vaginal colonization model. Better understanding of MRSA FRT colonization and ascension can ultimately inform treatment strategies to limit MRSA vaginal burden or prevent ascension, especially during pregnancy and in those prone to AV.

The FnBPA from methicillin-resistant Staphylococcus aureus promoted development of oral squamous cell carcinoma

Background

Oral squamous cell carcinoma (OSCC) is the most common tumor in the oral cavity. Methicillin-resistant Staphylococcus aureus (MRSA) were highly detected in OSCC patients; however, the interactions and mechanisms between drug-resistant bacteria (MRSA) and OSCC are not clear.

Aim

The aim of this study was to investigate the promotion of MRSA on the development of OSCC.

Methods

MRSA and MSSA (methicillin-susceptible) strains were employed to investigate the effect on the proliferation of OSCC in vitro and vivo.

Results

All of the MRSA strains significantly increased the proliferation of OSCC cells and MRSA arrested the cell cycles of OSCC cells in the S phase. MRSA activated the expression of TLR-4, NF-κB and c-fos in OSCC cells. MRSA also promoted the development of squamous cell carcinoma in vivo. The virulence factor fnbpA gene was significantly upregulated in all MRSA strains. By neutralizing FnBPA, the promotions of MRSA on OSCC cell proliferation and development of squamous cell carcinoma were significantly decreased. Meanwhile, the activation of c-fos and NF-κB by MRSA was also significantly decreased by FnBPA antibody.

Conclusion

MRSA promoted development of OSCC, and the FnBPA protein was the critical virulence factor. Targeting virulence factors is a new method to block the interaction between a drug-resistant pathogen and development of tumors.

In Silico Genome-Scale Analysis of Molecular Mechanisms Contributing to the Development of a Persistent Infection with Methicillin-Resistant Staphylococcus aureus (MRSA) ST239

The increasing frequency of isolation of methicillin-resistant Staphylococcus aureus (MRSA) limits the chances for the effective antibacterial therapy of staphylococcal diseases and results in the development of persistent infection such as bacteremia and osteomyelitis. The aim of this study was to identify features of the MRSA_ST239 0943-1505-2016 (SA943) genome that contribute to the formation of both acute and chronic musculoskeletal infections. The analysis was performed using comparative genomics data of the dominant epidemic S. aureus lineages, namely ST1, ST8, ST30, ST36, and ST239. The SA943 genome encodes proteins that provide resistance to the host's immune system, suppress immunological memory, and form biofilms. The molecular mechanisms of adaptation responsible for the development of persistent infection were as follows: amino acid substitution in PBP2 and PBP2a, providing resistance to ceftaroline; loss of a large part of prophage DNA and restoration of the nucleotide sequence of beta-hemolysin, that greatly facilitates the escape of phagocytosed bacteria from the phagosome and formation of biofilms; dysfunction of the AgrA system due to the presence of psm-mec and several amino acid substitutions in the AgrC; partial deletion of the nucleotide sequence in genomic island vSAβ resulting in the loss of two proteases of Spl-operon; and deletion of SD repeats in the SdrE amino acid sequence.

Novel Requirement for Staphylococcal Cell Wall-Anchored Protein SasD in Pulmonary Infection

Staphylococcus aureus can complicate preceding viral infections, including influenza virus. A bacterial infection combined with a preceding viral infection, known as superinfection, leads to worse outcomes than a single infection. Most of the pulmonary infection literature focuses on the changes in immune responses to bacteria between homeostatic and virally infected lungs. However, it is unclear how much of an influence bacterial virulence factors have in single or superinfection. Staphylococcal species express a broad range of cell wall-anchored proteins (CWAs) that have roles in host adhesion, nutrient acquisition, and immune evasion. We screened the importance of these CWAs using mutants lacking individual CWAs in vivo in both bacterial pneumonia and influenza superinfection. In bacterial pneumonia, the lack of individual CWAs leads to various decreases in bacterial burden, lung damage, and immune infiltration into the lung. However, the presence of a preceding influenza infection partially abrogates the requirement for CWAs. In the screen, we found that the uncharacterized CWA S. aureus surface protein D (SasD) induced changes in both inflammatory and homeostatic lung markers. We further characterized a SasD mutant (sasD A50.1) in the context of pneumonia. Mice infected with sasD A50.1 have decreased bacterial burden, inflammatory responses, and mortality compared to wild-type S. aureus. Mice also have reduced levels of interleukin-1β (IL-1β), likely derived from macrophages. Reductions in IL-1β transcript levels as well as increased macrophage viability point at differences in cell death pathways. These data identify a novel virulence factor for S. aureus that influences inflammatory signaling within the lung. IMPORTANCE Staphylococcus aureus is a common commensal bacterium that can cause severe infections, such as pneumonia. In the lung, viral infections increase the risk of staphylococcal pneumonia, leading to combined infections known as superinfections. The most common virus associated with S. aureus pneumonia is influenza, and superinfections lead to worse patient outcomes than either infection alone. While there is much known about how the immune system differs between healthy and virally infected lungs, the role of bacterial virulence factors in single and superinfection is less understood. The significance of our research is identifying bacterial components that play a role in the initiation of lung injury, which could lead to future therapies to prevent pulmonary single or superinfection with S. aureus.

Mycoplasma Bovis adhesins and their target proteins

Bovine mycoplasmosis is an important infectious disease of cattle caused by Mycoplasma bovis (M. bovis) which poses a serious threat to the breeding industry. Adhesin is involved in the initial process of M. bovis colonization, which is closely related to the infection, cell invasion, immune escape and virulence of this pathogenic microorganism. For the reason that M. bovis lacks a cell wall, its adhesin is predominantly located on the surface of the cell membrane. The adhesins of M. bovis are usually identified by adhesion and adhesion inhibition analysis, and more than 10 adhesins have been identified so far. These adhesins primarily bind to plasminogen, fibronectin, heparin and amyloid precursor-like protein-2 of host cells. This review aims to concisely summarize the current knowledge regarding the adhesins of M. bovis and their target proteins of the host cell. Additionally, the biological characteristics of the adhesin will be briefly analyzed.

Interaction of the Staphylococcus aureus Surface Protein FnBPB with Corneodesmosin Involves Two Distinct, Extremely Strong Bonds

Attachment of Staphylococcus aureus to human skin corneocyte cells plays a critical role in exacerbating the severity of atopic dermatitis (AD). Pathogen-skin adhesion is mediated by bacterial cell-surface proteins called adhesins, including fibronectin-binding protein B (FnBPB). FnBPB binds to corneodesmosin (CDSN), a glycoprotein exposed on AD patient corneocytes. Using single-molecule experiments, we demonstrate that CDSN binding by FnBPB relies on a sophisticated two-site mechanism. Both sites form extremely strong bonds with binding forces of ∼1 and ∼2.5 nN albeit with faster dissociation rates than those reported for homologues of the adhesin. This previously unidentified two-binding site interaction in FnBPB illustrates its remarkable variety of adhesive functions and is of biological significance as the high strength and short bond lifetime will favor efficient skin colonization by the pathogen.

The Role of Staphylococcal Biofilm on the Surface of Implants in Orthopedic Infection

Despite advanced implant sterilization and aseptic surgical techniques, implant-associated infection remains a major challenge for orthopedic surgeries. The subject of bacterial biofilms is receiving increasing attention, probably as a result of the wide acknowledgement of the ubiquity of biofilms in the clinical environment, as well as the extreme difficulty in eradicating them. Biofilm can be defined as a structured microbial community of cells that are attached to a substratum and embedded in a matrix of extracellular polymeric substances (EPS) that they have produced. Biofilm development has been proposed as occurring in a multi-step process: (i) attachment and adherence, (ii) accumulation/maturation due to cellular aggregation and EPS production, and (iii) biofilm detachment (also called dispersal) of bacterial cells. In all these stages, characteristic proteinaceous and non-proteinaceous compounds are expressed, and their expression is strictly controlled. Bacterial biofilm formation around implants shelters the bacteria and encourages the persistence of infection, which could lead to implant failure and osteomyelitis. These complications need to be treated by major revision surgeries and extended antibiotic therapies, which could lead to high treatment costs and even increase mortality. Effective preventive and therapeutic measures to reduce risks for implant-associated infections are thus in urgent need.

Strategies to prevent, curb and eliminate biofilm formation based on the characteristics of various periods in one biofilm life cycle

Biofilms are colonies of bacteria embedded inside a complicated self-generating intercellular. The formation and scatter of a biofilm is an extremely complex and progressive process in constant cycles. Once formed, it can protect the inside bacteria to exist and reproduce under hostile conditions by establishing tolerance and resistance to antibiotics as well as immunological responses. In this article, we reviewed a series of innovative studies focused on inhibiting the development of biofilm and summarized a range of corresponding therapeutic methods for biological evolving stages of biofilm. Traditionally, there are four stages in the biofilm formation, while we systematize the therapeutic strategies into three main periods precisely:(i) period of preventing biofilm formation: interfering the colony effect, mass transport, chemical bonds and signaling pathway of plankton in the initial adhesion stage; (ii) period of curbing biofilm formation:targeting several pivotal molecules, for instance, polysaccharides, proteins, and extracellular DNA (eDNA) via polysaccharide hydrolases, proteases, and DNases respectively in the second stage before developing into irreversible biofilm; (iii) period of eliminating biofilm formation: applying novel multifunctional composite drugs or nanoparticle materials cooperated with ultrasonic (US), photodynamic, photothermal and even immune therapy, such as adaptive immune activated by stimulated dendritic cells (DCs), neutrophils and even immunological memory aroused by plasmocytes. The multitargeted or combinational therapies aim to prevent it from developing to the stage of maturation and dispersion and eliminate biofilms and planktonic bacteria simultaneously.

Clinical Prevalence, Antibiogram Profiling and Gompertz Growth Kinetics of Resistant Staphylococcus epidermidis Treated with Nanoparticles of Rosin Extracted from Pinus roxburghii

The rise of methicillin-resistant Staphylococcus epidermidis (MRSE) makes it difficult to treat infections that increase morbidity and mortality rates in various parts of the world. The study’s objectives include identifying the clinical prevalence, antibiogram profile, and Gompertz growth kinetics of MRSE treated with synthetically created nanoparticles of rosin obtained from Pinus roxburghii. A total of 64 of 200 clinical isolates of S. epidermidis (32% of the total) displayed sensitivity (40.62%) and resistance (59.37%) to seven different antibiotic classes. The most sensitive patterns of antibiotic resistance were seen in 20 (78.95%) and 24 (94.74%) isolates of MRSE against piperacillin/tazobactam and cephradine, respectively. Fosfomycine was found to be the most effective antibiotic against MRSE in 34 (89.47%) isolates, followed by amoxicillin. Successfully produced, described, and used against MRSE were rosin maleic anhydride nanoparticles with a size range of 250 nm to 350 nm. Five different concentrations of 25, 50, 75, 100, and 150 mg mL⁻¹ rosin maleic anhydride nanoparticles were investigated to treat MRSE resistance. According to Gompertz growth kinetics, the maximal growth response was 32.54% higher and the lag phase was also 10.26% longer compared to the control when the amount of rosin maleic anhydride nanoparticles was increased in the MRSE. Following the application of rosin maleic anhydride nanoparticles, the growth period is extended from 6 to 8 h. A potential mechanism for cell disintegration and distortion is put forth. This investigation came to the conclusion that rosin maleic anhydride nanoparticles better interfere with the surface of MRSE and demonstrated a preferred bacteriostatic action.

Infective Endocarditis in High-Income Countries

Infective endocarditis remains an illness that carries a significant burden to healthcare resources. In recent times, there has been a shift from Streptococcus sp. to Staphylococcus sp. as the primary organism of interest. This has significant consequences, given the virulence of Staphylococcus and its propensity to form a biofilm, rendering non-surgical therapy ineffective. In addition, antibiotic resistance has affected treatment of this organism. The cohorts at most risk for Staphylococcal endocarditis are elderly patients with multiple comorbidities. The innovation of transcatheter technologies alongside other cardiac interventions such as implantable devices has contributed to the increased risk attributable to this cohort. We examined the pathophysiology of infective endocarditis carefully. Inter alia, the determinants of Staphylococcus aureus virulence, interaction with host immunity, as well as the discovery and emergence of a potential vaccine, were investigated. Furthermore, the potential role of prophylactic antibiotics during dental procedures was also evaluated. As rates of transcatheter device implantation increase, endocarditis is expected to increase, especially in this high-risk group. A high level of suspicion is needed alongside early initiation of therapy and referral to the heart team to improve outcomes.

Phenotypic and Genotypic Characterization of Macrolide, Lincosamide and Streptogramin B Resistance among Clinical Methicillin-Resistant Staphylococcus aureus Isolates in Chile

Macrolides, lincosamides, and type B streptogramins (MLSB) are important therapeutic options to treat methicillin-resistant Staphylococcus aureus (MRSA) infections; however, resistance to these antibiotics has been emerging. In Chile, data on the MLSB resistance phenotypes are scarce in both community-(CA) and hospital-acquired (HA) MRSA isolates. Antimicrobial susceptibility to MLSB was determined for sixty-eight non-repetitive isolates of each HA-(32) and CA-MRSA (36). Detection of SCCmec elements, ermA, ermB, ermC, and msrA genes was performed by PCR. The predominant clones were SCCmec I-ST5 (HA-MRSA) and type IVc-ST8 (CA-MRSA). Most of the HA-MRSA isolates (97%) showed resistance to clindamycin, erythromycin, azithromycin, and clarithromycin. Among CA-MRSA isolates, 28% were resistant to erythromycin, azithromycin, and 25% to clarithromycin. All isolates were susceptible to linezolid, vancomycin, daptomycin and trimethoprim/sulfamethoxazole, and over 97% to rifampicin. The ermA gene was amplified in 88% of HA-MRSA and 17% of CA-MRSA isolates (p < 0.001). The ermC gene was detected in 6% of HA-SARM and none of CA-SARM isolates, whereas the msrA gene was only amplified in 22% of CA-MRSA (p < 0.005). Our results demonstrate the prevalence of the cMLSB resistance phenotype in all HA-MRSA isolates in Chile, with the ermA being the predominant gene identified among these isolates.

Staphylococcus aureus adhesion to the host

Staphylococcus aureus is a pathobiont capable of colonizing and infecting most tissues within the human body, resulting in a multitude of different clinical outcomes. Adhesion of S. aureus to the host is crucial for both host colonization and the establishment of infections. Underlying the pathogen's success is a complex and diverse arsenal of adhesins. In this review, we discuss the different classes of adhesins, including a consideration of the various adhesion sites throughout the body and the clinical outcomes of each infection type. The development of therapeutics targeting the S. aureus host-pathogen interaction is a relatively understudied area. Due to the increasing global threat of antimicrobial resistance, it is crucial that innovative and alternative approaches are considered. Neutralizing virulence factors, through the development of antivirulence agents, could reduce bacterial pathogenicity and the ever-increasing burden of S. aureus infections. This review provides insight into potentially efficacious adhesion-associated targets for the development of novel decolonizing and antivirulence strategies.

Transition metal complex laminated bioactive implant alleviates Methicillin Resistant Staphylococcus aureus virulence

Orthopedic implant infections cause a serious threat after implantation. The major source of implant infection is biofilms which are highly tolerant to antibiotics due to the presence of rigid biofilm matrix. Hence to overcome biofilm mediated implant infections, we developed a novel antibiofilm agent, palladium (II) thiazolinyl picolinamide complex (Pd(II)-E). From our study, it was found that Pd(II)-E have profound biofilm inhibition activity and also reduced various virulence factors of Methicillin resistant Staphylococcus aureus (MRSA) including slime synthesis, Phenol soluble modulin (PSM) mediated spreading, Exopolysaccharides production and staphyloxanthin synthesis. Further, Pd(II)-E was coated over the titanium plates which was confirmed using EDX (Energy Dispersive X-Ray) analysis. The Pd(II)-E coated plates were able to prevent the biofilm formation on them which was evident under a Scanning electron microscope (SEM) and several virulent genes were found to be downregulated in the biofilms on the coated titanium plates which confirmed by qPCR. From our findings, it was found that Pd(II)-E coated titanium implants would be an effective alternate approach for preventing biofilm mediated implant infections.

Effects of Imipenem-containing Niosome nanoparticles against high prevalence methicillin-resistant Staphylococcus Epidermidis biofilm formed

We aim to assess the antibacterial and anti-biofilm properties of Niosome-encapsulated Imipenem. After isolating Staphylococcus epidermidis isolates and determining their microbial sensitivity, their ability to form biofilms was examined using plate microtiter assay. Various formulations of Niosome-encapsulated Imipenem were prepared using the thin-film hydration method, Minimum Biofilm Inhibitory Concentration (MBIC) and Minimum Inhibitory Concentration (MIC) were determined, and biofilm genes expression was examined. Drug formulations’ toxicity effect on HDF cells were determined using MTT assay. Out of the 162 separated S. epidermidis, 106 were resistant to methicillin. 87 MRSE isolates were vancomycin-resistant, all of which could form biofilms. The F1 formulation of niosomal Imipenem with a size of 192.3 ± 5.84 and an encapsulation index of 79.36 ± 1.14 was detected, which prevented biofilm growth with a BGI index of 69% and reduced icaD, FnbA, EbpS biofilms’ expression with P ≤ 0.001 in addition to reducing MBIC and MIC by 4–6 times. Interestingly, F1 formulation of niosomal Imipenem indicated cell viability over 90% at all tested concentrations. The results of the present study indicate that Niosome-encapsulated Imipenem reduces the resistance of MRSE to antibiotics in addition to increasing its anti-biofilm and antibiotic activity, and could prove useful as a new strategy for drug delivery.

Interactions between the foreign body reaction and Staphylococcus aureus biomaterial-associated infection. Winning strategies in the derby on biomaterial implant surfaces

Biomaterial-associated infections (BAIs) are an increasing problem where antibiotic therapies are often ineffective. The design of novel strategies to prevent or combat infection requires a better understanding of how an implanted foreign body prevents the immune system from eradicating surface-colonizing pathogens. The objective of this review is to chart factors resulting in sub-optimal clearance of Staphylococcus aureus bacteria involved in BAIs. To this end, we first describe three categories of bacterial mechanisms to counter the host immune system around foreign bodies: direct interaction with host cells, modulation of intercellular communication, and evasion of the immune system. These mechanisms take place in a time frame that differentiates sterile foreign body reactions, BAIs, and soft tissue infections. In addition, we identify experimental interventions in S. aureus BAI that may impact infectious mechanisms. Most experimental treatments modulate the host response to infection or alter the course of BAI through implant surface modulation. In conclusion, the first week after implantation and infection is crucial for the establishment of an S. aureus biofilm that resists the local immune reaction and antibiotic treatment. Although established and chronic S. aureus BAI is still treatable and manageable, the focus of interventions should lie on this first period.

Understanding the Role of the Antioxidant Drug Erdosteine and Its Active Metabolite on Staphylococcus aureus Methicillin Resistant Biofilm Formation

Increasing numbers of researches have suggested that some drugs with reactive oxygen species (ROS)-mediated mechanisms of action modulate biofilm formation of some pathogenic strains. However, the full contribution of ROS to biofilm development is still an open question. In this paper, the correlations between the antioxidant drug Erdosteine (Er) and its active Metabolite I (Met I), ROS and biofilm development of two strains of methicillin resistant Staphylococcus aureus are presented. Experiments revealed that Er and Met I at 2 and 5 mg/L increased up to three orders of magnitude the number of biofilm-dwelling cells, while the content of ROS within the biofilms was reduced above the 87%, with a major effect of Met I in comparison to Er. Comparative proteomics showed that, 5 mg/L Met I modified the expression of 30% and 65% of total proteins in the two strains respectively. Some proteins involved in cell replication were upregulated, and a nitric oxide-based mechanism is assumed to modulate the biofilm development by changing quorum sensitive pathways. Additionally, several proteins involved in virulence were downregulated in the presence of Met I, suggesting that treated cells, despite being greater in number, might have lost part of their virulence.

Host blood proteins as bridging ligand in bacterial aggregation as well as anchor point for adhesion in the molecular pathogenesis of Staphylococcus aureus infections

Fibronectin (Fn) and fibrinogen (Fg) are major host proteins present in the extracellular matrix, blood, and coatings on indwelling medical devices. The ability of Staphylococcus aureus to cause infections in humans depends on favorable interactions with these host ligands. Closely related bacterial adhesins, fibronectin-binding proteins A and B (FnBPA, FnBPB) were evaluated for two key steps in pathogenesis: clumping and adhesion. Experiments utilized optical spectrophotometry, flow cytometry, and atomic force microscopy to probe FnBPA/B alone or in combination in seven different strains of S. aureus and Lactococcus lactis, a Gram-positive surrogate that naturally lacks adhesins to mammalian ligands. In the absence of soluble ligands, both FnBPA and FnBPB were capable of interacting with adjacent FnBPs from neighboring bacteria to mediate clumping. In the presence of soluble host ligands, clumping was enhanced particularly under shear stress and with Fn present in the media. FnBPB exhibited greater ability to clump compared to FnBPA. The strength of adhesion was similar for immobilized Fn to FnBPA and FnBPB. These findings suggest that these two distinct but closely related bacterial adhesins, have different functional capabilities to interact with host ligands in different settings (e.g., soluble vs. immobilized). Survival and persistence of S. aureus in a human host may depend on complementary roles of FnBPA and FnBPB as they interact with different conformations of Fn or Fg (compact in solution vs. extended on a surface) present in different physiological spaces.

PIP5KIγ90-generated phosphatidylinositol-4,5-bisphosphate promotes the uptake of Staphylococcus aureus by host cells

Staphylococcus aureus, a Gram-positive pathogen, invades cells mainly in an integrin-dependent manner. As the activity or conformation of several integrin-associated proteins can be regulated by phosphatidylinositol-4,5-bisphosphate (PI-4,5-P₂ ), we investigated the roles of PI-4,5-P₂ and PI-4,5-P₂ -producing enzymes in cellular invasion by S. aureus. PI-4,5-P₂ accumulated upon contact of S. aureus with the host cell, and targeting of an active PI-4,5-P₂ phosphatase to the plasma membrane reduced bacterial invasion. Knockdown of individual phosphatidylinositol-4-phosphate 5-kinases revealed that phosphatidylinositol-4-phosphate 5-kinase γ (PIP5KIγ) plays an important role in bacterial internalization. Specific ablation of the talin and FAK-binding motif in PIP5KIγ90 reduced bacterial invasion, which could be rescued by reexpression of an active, but not inactive PIP5KIγ90. Furthermore, PIP5KIγ90-deficient cells showed normal basal PI-4,5-P₂ levels in the plasma membrane but reduced the accumulation of PI-4,5-P₂ and talin at sites of S. aureus attachment and overall lower levels of FAK phosphorylation. These results highlight the importance of local synthesis of PI-4,5-P₂ by a focal adhesion-associated lipid kinase for integrin-mediated internalization of S. aureus.

Bacterial Biofilms and Their Implications in Pathogenesis and Food Safety

Biofilm formation is an integral part of the microbial life cycle in nature. In food processing environments, bacterial transmissions occur primarily through raw or undercooked foods and by cross-contamination during unsanitary food preparation practices. Foodborne pathogens form biofilms as a survival strategy in various unfavorable environments, which also become a frequent source of recurrent contamination and outbreaks of foodborne illness. Instead of focusing on bacterial biofilm formation and their pathogenicity individually, this review discusses on a molecular level how these two physiological processes are connected in several common foodborne pathogens such as Listeria monocytogenes, Staphylococcus aureus, Salmonella enterica and Escherichia coli. In addition, biofilm formation by Pseudomonas aeruginosa is discussed because it aids the persistence of many foodborne pathogens forming polymicrobial biofilms on food contact surfaces, thus significantly elevating food safety and public health concerns. Furthermore, in-depth analyses of several bacterial molecules with dual functions in biofilm formation and pathogenicity are highlighted.

Molecular characterization of Staphylococcus aureus isolates derived from severe pneumonia: a retrospective monocentre study

BACKGROUND

Staphylococcus aureus is endowed with a repertoire of virulence factors potentially implicated in its pathogenicity and ability to cause invasive disease. The main objective of this study was to describe the bacterial genotype, including virulence genes and affiliation to clonal complexes (CCs), encountered in severe pneumonia.

METHODS

DNA microarray was used to analyse 18 S. aureus isolates from patients hospitalized with severe pneumonia between 2017 and 2019.

RESULTS

Among 18 S. aureus isolates, 14 were methicillin-susceptible S. aureus (MSSA), and 4 methicillin-resistant S. aureus (MRSA). There were 14 community-acquired, 3 healthcare-associated, and 1 hospital-acquired infections. Different radiological presentations were observed: necrotizing pneumonia (n = 8, 44%), alveolar consolidation (n = 7, 39%), alveolar-interstitial infiltrates (n = 3, 17%). Sixteen patients (89%) required ICU hospitalization, 13 (72%) an invasive mechanical ventilation, and 12 (67%) a vasopressor support. Mortality affected 6 patients (33%). Panton-Valentine leukocidin (PVL), staphylococcal enterotoxins, toxic shock syndrome toxine-1 (TSST-1) encoding genes were documented in nine (50%), 12 (67%), one (6%) of the isolates, respectively. Accessory regulator gene group I was the most reported (n = 9, 50%) and was found in five deaths. The majority of isolates were affiliated to CC152 (n = 6), followed by CC15 (n = 3), CC45 (n = 2), CC30 (n = 2), CC1 (n = 2), CC8 (n = 1), CC9 (n = 1), and CC25 (n = 1). All the CC152 isolates were PVL-positive.

CONCLUSION

CC152-PVL positive S. aureus strains were the most prevalent in severe pneumonia. Other virulence gene profiles were found coupled to additional clonal lineages. A genotyping strategy contributes to describe the current circulating strains and bacterial genetic backgrounds.

Host-Pathogen Adhesion as the Basis of Innovative Diagnostics for Emerging Pathogens

Infectious diseases are an existential health threat, potentiated by emerging and re-emerging viruses and increasing bacterial antibiotic resistance. Targeted treatment of infectious diseases requires precision diagnostics, especially in cases where broad-range therapeutics such as antibiotics fail. There is thus an increasing need for new approaches to develop sensitive and specific in vitro diagnostic (IVD) tests. Basic science and translational research are needed to identify key microbial molecules as diagnostic targets, to identify relevant host counterparts, and to use this knowledge in developing or improving IVD. In this regard, an overlooked feature is the capacity of pathogens to adhere specifically to host cells and tissues. The molecular entities relevant for pathogen–surface interaction are the so-called adhesins. Adhesins vary from protein compounds to (poly-)saccharides or lipid structures that interact with eukaryotic host cell matrix molecules and receptors. Such interactions co-define the specificity and sensitivity of a diagnostic test. Currently, adhesin-receptor binding is typically used in the pre-analytical phase of IVD tests, focusing on pathogen enrichment. Further exploration of adhesin–ligand interaction, supported by present high-throughput “omics” technologies, might stimulate a new generation of broadly applicable pathogen detection and characterization tools. This review describes recent results of novel structure-defining technologies allowing for detailed molecular analysis of adhesins, their receptors and complexes. Since the host ligands evolve slowly, the corresponding adhesin interaction is under selective pressure to maintain a constant receptor binding domain. IVD should exploit such conserved binding sites and, in particular, use the human ligand to enrich the pathogen. We provide an inventory of methods based on adhesion factors and pathogen attachment mechanisms, which can also be of relevance to currently emerging pathogens, including SARS-CoV-2, the causative agent of COVID-19.

Antibacterial Optimization of Highly Deformed Titanium Alloys for Spinal Implants

The goal of the work was to develop materials dedicated to spine surgery that minimized the potential for infection originating from the transfer of bacteria during long surgeries. The bacteria form biofilms, causing implant loosening, pain and finally, a risk of paralysis for patients. Our strategy focused both on improvement of antibacterial properties against bacteria adhesion and on wear and corrosion resistance of tools for spine surgery. Further, a ~35% decrease in implant and tool dimensions was expected by introducing ultrahigh-strength titanium alloys for less-invasive surgeries. The tested materials, in the form of thin, multi-layered coatings, showed nanocrystalline microstructures. Performed direct-cytotoxicity studies (including lactate dehydrogenase activity measurement) showed that there was a low probability of adverse effects on surrounding SAOS-2 (Homo sapiens bone osteosarcoma) cells. The microbiological studies (e.g., ISO 22196 contact tests) showed that implanting Ag nanoparticles into Ti/Ti_xN coatings inhibited the growth of E. coli and S. aureus cells and reduced their adhesion to the material surface. These findings suggest that Ag-nanoparticles present in implant coatings may potentially minimize infection risk and lower inherent stress.

Staphylococcus aureus Toxins: Promoter or Handicap during Infection?

Staphylococcus aureus is an opportunistic and versatile pathogen that can cause several diseases, which range from acute and destructive, to chronic and difficult-to-treat infections [...].

Bacterial Targets of Antibiotics in Methicillin-Resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most prevalent bacterial pathogens and continues to be a leading cause of morbidity and mortality worldwide. MRSA is a commensal bacterium in humans and is transmitted in both community and healthcare settings. Successful treatment remains a challenge, and a search for new targets of antibiotics is required to ensure that MRSA infections can be effectively treated in the future. Most antibiotics in clinical use selectively target one or more biochemical processes essential for S. aureus viability, e.g., cell wall synthesis, protein synthesis (translation), DNA replication, RNA synthesis (transcription), or metabolic processes, such as folic acid synthesis. In this review, we briefly describe the mechanism of action of antibiotics from different classes and discuss insights into the well-established primary targets in S. aureus. Further, several components of bacterial cellular processes, such as teichoic acid, aminoacyl-tRNA synthetases, the lipid II cycle, auxiliary factors of β-lactam resistance, two-component systems, and the accessory gene regulator quorum sensing system, are discussed as promising targets for novel antibiotics. A greater molecular understanding of the bacterial targets of antibiotics has the potential to reveal novel therapeutic strategies or identify agents against antibiotic-resistant pathogens.

AFM in cellular and molecular microbiology

The unique capabilities of the atomic force microscope (AFM), including super-resolution imaging, piconewton force-sensitivity, nanomanipulation and ability to work under physiological conditions, have offered exciting avenues for cellular and molecular biology research. AFM imaging has helped unravel the fine architectures of microbial cell envelopes at the nanoscale, and how these are altered by antimicrobial treatment. Nanomechanical measurements have shed new light on the elasticity, tensile strength and turgor pressure of single cells. Single-molecule and single-cell force spectroscopy experiments have revealed the forces and dynamics of receptor-ligand interactions, the nanoscale distribution of receptors on the cell surface and the elasticity and adhesiveness of bacterial pili. Importantly, recent force spectroscopy studies have demonstrated that extremely stable bonds are formed between bacterial adhesins and their cognate ligands, originating from a catch bond behaviour allowing the pathogen to reinforce adhesion under shear or tensile stress. Here, we survey how the versatility of AFM has enabled addressing crucial questions in microbiology, with emphasis on bacterial pathogens. TAKE AWAYS: AFM topographic imaging unravels the ultrastructure of bacterial envelopes. Nanomechanical mapping shows what makes cell envelopes stiff and resistant to drugs. Force spectroscopy characterises the molecular forces in pathogen adhesion. Stretching pili reveals a wealth of mechanical and adhesive responses.

Pathogenic effects of inhibition of mTORC1/STAT3 axis facilitates Staphylococcus aureus-induced pyroptosis in human macrophages

BACKGROUND

Pyroptosis is a recently identified pathway of caspase-mediated cell death in response to microbes, lipopolysaccharide, or chemotherapy in certain types of cells. However, the mechanism of how pyroptosis is regulated is not well-established.

METHODS

Herein, the intracellular bacteria were detected by staining and laser confocal microscopy and TEM. Live/dead cell imaging assay was used to examine macrophage death. Western blot and immunohistochemical staining were used to examine the protein changes. IFA was used to identify typical budding vesicles of pyroptosis and the STAT3 nuclear localization. SEM was used to observe the morphological characteristics of pyroptosis. ELISA was used to detect the level of inflammatory cytokines. Pyroptosis was filmed in macrophages by LSCM.

RESULTS

S. aureus was internalized by human macrophages. Intracellular S. aureus induced macrophage death. S. aureus invasion increased the expression of NLRP3, Caspase1 (Casp-1 p20) and the accumulation of GSDMD-NT, GSDMD-NT pore structures, and the release of IL-1β and IL-18 in macrophages. Macrophages pyroptosis induced by S. aureus can be abrogated by blockage of S. aureus phagocytosis. The pyroptosic effect by S. aureus infection was promoted by either rapamycin or Stattic, a specific inhibitor for mTORC1 or STAT3. Inhibition of mTORC1 or STAT3 induced pyroptosis. mTORC1 regulated the pyroptosic gene expression through governing the nuclear localization of STAT3. mTORC1/STAT3 axis may play a regulatory role in pyroptosis within macrophages.

CONCLUSIONS

S. aureus infection induces human macrophage pyroptosis, inhibition of mTORC1/STAT3 axis facilitates S. aureus-induced pyroptosis. mTORC1 and STAT3 are associated with pyroptosis. Our findings demonstrate a regulatory function of the mTORC1/STAT3 axis in macrophage pyroptosis, constituting a novel mechanism by which pyroptosis is regulated in macrophages. Video Abstract Macrophages were infected with S. aureus for 3 h (MOI 25:1), and pyroptosis was filmed in macrophages by laser confocal microscopy. A representative field was recorded. Arrow indicates lysing dead cell.

Phenotypic Characterization and Whole Genome Analysis of a Strong Biofilm-Forming Staphylococcus aureus Strain Associated With Subclinical Bovine Mastitis in Colombia

Staphylococcus aureus represent a serious threat to public health due to food safety, antibiotic resistance, and the potential zoonotic transmission of strains between dairy cattle and humans. Biofilm formation by S. aureus results in chronicity of the infections which confers protection against the immune response and antibiotics. Likewise, biofilm allows the exchange of mobile genetic material among different strains through microbial interactions inside the matrix. In Colombia, where S. aureus continues to be one of the main pathogens isolated from bovine intramammary infections and where milking by hand is highly frequent, there are knowledge gaps on the zoonotic potential of the strains. Therefore, the aim of this work was to characterize genotypically and phenotypically the S. aureus Sa1FB strain with strong biofilm production and to perform genomic and phenotypic comparisons with other relevant S. aureus strains (native and references strains). These results show a highly productive strain of biofilm and a low ability of cell invasion compared to the other two native strains. In addition, high genomic similarity between S. aureus Sa1FB and the reference strains was observed, despite of the differences reported at the clinical level. However, Sa1FB exhibited special features in terms of mobile genetic elements, highlighting its ability to accept foreign genetic material. Indeed, this could increase mutation, pathogenesis, and adaptability to new hosts, representing a risk for people in contact with the milk obtained from animals infected with these strains. These results present the relevance of surveillance for early detection of emergent clones with zoonotic potential, which reduces the risk of occupational exposure and their spread in the community.

Adhesin genes and biofilm formation among pediatric Staphylococcus aureus isolates from implant-associated infections

BACKGROUND

Microbial surface component recognizing adhesive matrix molecules (MSCRAMMs) facilitate Staphylococcus aureus adherence to host tissue. We hypothesized that S. aureus isolates from implant-associated infections (IAIs) would differ in MSCRAMM profile and biofilm formation in vitro compared to skin and soft tissue infection (SSTI) isolates.

METHODS

Pediatric patients and their isolates were identified retrospectively. IAI and SSTI isolates were matched (1:4). Pulsed field gel electrophoresis was performed to group isolates as USA300 vs. non-USA300. Whole genome sequencing was performed and raw sequence data were interrogated for presence of MSCRAMMs (clfA, clfB, cna, ebh, efb, fnbpA, fnbpB, isdA, isdB, sdrC, sdrD, sdrE), biofilm-associated (icaA,D,B,C), and Panton-Valentine leukocidin (lukSF-PV) genes, accessory gene regulator group, and multilocus sequence types. In vitro biofilm formation was assessed for 47 IAI and 47 SSTI isolates using a microtiter plate assay. Conditional logistic regression was performed for analysis of matched data (STATA11, College Station, TX).

RESULTS

Forty-seven IAI and 188 SSTI isolates were studied. IAI isolates were more often methicillin susceptible S. aureus and non-USA300 vs. SSTI isolates [34 (72%) vs. 79 (42%), p = 0.001 and 38 (81%) vs. 57 (30%) p <0.001, respectively]. Greater than 98% of isolates carried clfA, clfB, efb, isdA, isdB, and icaA,D,B,C while cna was more frequently found among IAI vs. SSTI isolates (p = 0.003). Most isolates were strong biofilm producers.

CONCLUSIONS

S. aureus IAI isolates were significantly more likely to be MSSA and non-USA300 than SSTI isolates. Carriage of MSCRAMMs and biofilm formation did not differ significantly between isolates. Evaluation of genetic polymorphisms and gene expression profiles are needed to further delineate the role of adhesins in the pathogenesis of IAIs.

Vacuolar escape of foodborne bacterial pathogens

The intracellular pathogens Listeria monocytogenes, Salmonella enterica, Shigella spp. and Staphylococcus aureus are major causes of foodborne illnesses. Following the ingestion of contaminated food or beverages, pathogens can invade epithelial cells, immune cells and other cell types. Pathogens survive and proliferate intracellularly via two main strategies. First, the pathogens can remain in membrane-bound vacuoles and tailor organellar trafficking to evade host-cell defenses and gain access to nutrients. Second, pathogens can rupture the vacuolar membrane and proliferate within the nutrient-rich cytosol of the host cell. Although this virulence strategy of vacuolar escape is well known for L. monocytogenes and Shigella spp., it has recently become clear that S. aureus and Salmonella spp. also gain access to the cytosol, and that this is important for their survival and growth. In this Review, we discuss the molecular mechanisms of how these intracellular pathogens rupture the vacuolar membrane by secreting a combination of proteins that lyse the membranes or that remodel the lipids of the vacuolar membrane, such as phospholipases. In addition, we also propose that oxidation of the vacuolar membrane also contributes to cytosolic pathogen escape. Understanding these escape mechanisms could aid in the identification of new therapeutic approaches to combat foodborne pathogens.

A Review of Current Knowledge on Staphylococcus agnetis in Poultry

Simple Summary

This literature review provides a synthesis and evaluation of the current knowledge on Staphylococcus agnetis (S. agnetis) and its implications in poultry pathology. Recent studies revealed that S. agnetis can cause bacterial chondronecrosis with osteomyelitis (BCO), endocarditis, and septicemia in broiler chickens. Lameness constitutes one of the major health and welfare problems causing huge economic losses in the poultry industry. To date, a range of infectious and non-infectious factors have been associated with lameness in poultry. Among bacteria of the genus Staphylococcus, Staphylococcus aureus is the main species associated with locomotor problems. This contrasts with S. agnetis, which until recently had not been considered as a poultry pathogen. Previously only reported in cattle, S. agnetis has expanded its host range to chickens, and due to its unique characteristics has become recognized as a new emerging pathogen. The genotypic and phenotypic similarities between S. agnetis and other two staphylococci (S. hyicus and S. chromogenes) make this pathogen capable of escaping recognition due to misidentification. Although a significant amount of research on S. agnetis has been conducted, many facts about this novel species are still unknown and further studies are required to understand its full significance in poultry pathology.

Abstract

This review aims to summarize recent discoveries and advancements regarding the characteristics of Staphylococcus agnetis (S. agnetis) and its role in poultry pathology. S. agnetis is an emerging pathogen that was primarily associated with mastitis in dairy cattle. After a presumed host jump from cattle to poultry, it was identified as a pathological agent in broiler chickens (Gallus gallus domesticus), causing lameness induced by bacterial chondronecrosis with osteomyelitis (BCO), septicemia, and valvular endocarditis. Economic and welfare losses caused by lameness are global problems in the poultry industry, and S. agnetis has been shown to have a potential to induce high incidences of lameness in broiler chickens. S. agnetis exhibits a distinct repertoire of virulence factors found in many different staphylococci. It is closely related to S. hyicus and S. chromogenes, hence infections caused by S. agnetis may be misdiagnosed or even undiagnosed. As there are very few reports on S. agnetis in poultry, many facts about its pathogenesis, epidemiology, routes of transmission, and the potential impacts on the poultry industry remain unknown.

Statins potentiate the antibacterial effect of platelets on Staphylococcus aureus

Platelets have largely demonstrated their implication in anti-infectious immunity. This effect is ensured by the secreted molecules stored mostly in platelet alpha granules. Previous studies have reported that Staphylococcus aureus showed sensitivity to this antibacterial effect of platelets. Statins, for their part, have shown a modulating effect on platelet activation. Furthermore, several studies have reported a protective effect of statins in staphylococcal endocarditis. The aim of this study was to investigate the influence of statins on the antibacterial effect of washed platelets. Blood samples were collected from healthy donors (n = 35). PRP was prepared according to the ISTH recommendation. Bacteria were incubated for four hours with untreated-washed platelets, or rather treated by statins and/or GPIIbIIIa antagonists. In order to evaluate the antibacterial effect, the platelet-bacteria mix was spread on the blood agar to count the number of colonies after 18 hours of incubation. Measurement of CD 41 and CD62P expression by flow cytometry was performed to evaluate the effect of statin on bacterial-induced platelet activation. Statins have shown a potentiation of the antibacterial effect of washed platelets (p < .01 for Atorvastatin and Rosuvastatin and p < .001 for Fluvastatin vs untreated washed platelets condition). This effect of statins was dose-dependent and was more significant at 20 μM. The addition of Fluvastatin to platelet-bacterial mix significantly increased the expression of platelet CD41 and CD62P (p < .05 and p < .01 vs resting washed platelets, respectively). Tirofiban, GPIIbIIIa antagonist, reversed the antibacterial effect of washed platelets and suppressed the potentiating effect of statins. Our study demonstrated that statins potentiate the anti-staphylococcal effect of washed platelets. This result may explain the beneficial effect of statins on Staphylococcus aureus infective endocarditis. Further studies are therefore required to explain this effect at the molecular level and to assess its impact in vivo.

Binding Strength of Gram-Positive Bacterial Adhesins

Bacterial pathogens are equipped with specialized surface-exposed proteins that bind strongly to ligands on host tissues and biomaterials. These adhesins play critical roles during infection, especially during the early step of adhesion where the cells are exposed to physical stress. Recent single-molecule experiments have shown that staphylococci interact with their ligands through a wide diversity of mechanosensitive molecular mechanisms. Adhesin-ligand interactions are activated by tensile force and can be ten times stronger than classical non-covalent biological bonds. Overall these studies demonstrate that Gram-positive adhesins feature unusual stress-dependent molecular interactions, which play essential roles during bacterial colonization and dissemination. With an increasing prevalence of multidrug resistant infections caused by Staphylococcus aureus and Staphylococcus epidermidis, chemotherapeutic targeting of adhesins offers an innovative alternative to antibiotics.

Adhesin genes and biofilm formation among pediatric Staphylococcus aureus isolates from implant-associated infections

Background

Microbial surface component recognizing adhesive matrix molecules (MSCRAMMs) facilitate Staphylococcus aureus adherence to host tissue. We hypothesized that S. aureus isolates from implant-associated infections (IAIs) would differ in MSCRAMM profile and biofilm formation in vitro compared to skin and soft tissue infection (SSTI) isolates.

Methods

Pediatric patients and their isolates were identified retrospectively. IAI and SSTI isolates were matched (1:4). Pulsed field gel electrophoresis was performed to group isolates as USA300 vs. non-USA300. Whole genome sequencing was performed and raw sequence data were interrogated for presence of MSCRAMMs (clfA, clfB, cna, ebh, efb, fnbpA, fnbpB, isdA, isdB, sdrC, sdrD, sdrE), biofilm-associated (icaA,D,B,C), and Panton-Valentine leukocidin (lukSF-PV) genes, accessory gene regulator group, and multilocus sequence types. In vitro biofilm formation was assessed for 47 IAI and 47 SSTI isolates using a microtiter plate assay. Conditional logistic regression was performed for analysis of matched data (STATA11, College Station, TX).

Results

Forty-seven IAI and 188 SSTI isolates were studied. IAI isolates were more often methicillin susceptible S. aureus and non-USA300 vs. SSTI isolates [34 (72%) vs. 79 (42%), p = 0.001 and 38 (81%) vs. 57 (30%) p <0.001, respectively]. Greater than 98% of isolates carried clfA, clfB, efb, isdA, isdB, and icaA,D,B,C while cna was more frequently found among IAI vs. SSTI isolates (p = 0.003). Most isolates were strong biofilm producers.

Conclusions

S. aureus IAI isolates were significantly more likely to be MSSA and non-USA300 than SSTI isolates. Carriage of MSCRAMMs and biofilm formation did not differ significantly between isolates. Evaluation of genetic polymorphisms and gene expression profiles are needed to further delineate the role of adhesins in the pathogenesis of IAIs.

Analyzing the adhesion mechanism of FnBPA, a surface adhesin from Staphylococcus aureus on its interaction with nanoparticle

Staphylococcus aureus expresses many Microbial Surface Recognizing Adhesive Matrix Molecules (MSCRAMM's) to recognize host extracellular matrix (ECM) molecules to initiate colonization. The MSCRAMM, fibronectin binding protein A (FnBPA), is an important adhesin for S. aureus infection. FnBPA also binds with fibrinogen (Fg) by using a unique ligand binding mechanism called dock, lock and latch. Nanoparticles, especially nanosilver particles have been widely used in a variety of biomedical applications which includes disease diagnosis and treatment, drug delivery and implanted medical device coating. In a biological system, when protein molecules encounter nanoparticle, they can be absorbed onto its surface which results in the formation of protein corona. In the present study, we have analysed the fibrinogen binding ability of rFnBPA_(189-512) in the presence of silver nanoparticles by employing techniques like gel shift assay, Western blot, size exclusion chromatography, enzyme-linked immunosorbent assay, bio-layer interferometry and circular dichroism spectroscopy. The results indicate that rFnBPA_(189-512) is unable to bind to Fg in the presence of a nanoparticle. This could be due to the inaccessibility of the Fg binding site and conformational change in rFnBPA_(189-512). With nanoparticles, rFnBPA_(189-512) undergoes significant structural changes as the β-sheet content has drastically reduced to 10% from the initial 60% at higher concentration of the nanoparticle. Pathogenic bacteria interact with its surrounding environment through their surface molecules which includes MSCRAMMs. Therefore MSCRAMMs play an important role when bacteria encounter nanoparticles. The results of the present study suggest that the orientation of the protein during the absorption on the surface of a nanoparticle as well as the concentration of the nanoparticle, will dictate the function of the absorbed protein and in this case the Fg binding property of rFnBPA_(189-512).

Prevalence and Therapies of Antibiotic-Resistance in Staphylococcus aureus

Infectious diseases are the second most important cause of human death worldwide; Staphylococcus aureus (S. aureus) is a very common human pathogenic microorganism that can trigger a variety of infectious diseases, such as skin and soft tissue infections, endocarditis, osteomyelitis, bacteremia, and lethal pneumonia. Moreover, according to the sensitivity to antibiotic drugs, S. aureus can be divided into methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA). In recent decades, due to the evolution of bacteria and the abuse of antibiotics, the drug resistance of S. aureus has gradually increased, the infection rate of MRSA has increased worldwide, and the clinical anti-infective treatment for MRSA has become more difficult. Accumulating evidence has demonstrated that the resistance mechanisms of S. aureus are very complex, especially for MRSA, which is resistant to many kinds of antibiotics. Therefore, understanding the drug resistance of MRSA in a timely manner and elucidating its drug resistance mechanism at the molecular level are of great significance for the treatment of S. aureus infection. A large number of researchers believe that analyzing the molecular characteristics of S. aureus can help provide a basis for designing effective prevention and treatment measures against hospital infections caused by S. aureus and further monitor the evolution of S. aureus. This paper reviews the research status of MSSA and MRSA, the detailed mechanisms of the intrinsic antibiotic resistance and the acquired antibiotic resistance, the advanced research on anti-MRSA antibiotics and novel therapeutic strategies for MRSA treatment.

The role of staphopain a in Staphylococcus aureus keratitis

Staphylococcus aureus is a common bacterial isolate from cases of microbial keratitis. The virulence factors that contribute to its pathogenicity during this disease have not been fully resolved. The aim of the current study was to examine the effects of the extracellular protease Staphopain A on corneal virulence. Two strains were used, one Staph 38 that gives a high pathology score during keratitis and a less virulent strain ATCC 8325-4. The effect of inhibition of Staphopain by general or specific protease inhibitors on adhesion of strains to fibronectin-coated glass or PMMA was determined. This was followed by an analysis of the effect of Staphopain A on the ability of the bacteria to adhere to and invade corneal epithelial cells. Finally, the effect of inhibiting Staphopain A on pathogenesis in a mouse model of keratitis was studied. Staphopain A increased the adhesion of strains to fibronectin-coated substrata and inhibition of Staphopain A reduced adhesion. The inhibition of Staphopain A by staphostatin A significantly decreased both association with and invasion into human corneal epithelial cells by 15-fold for strain Saur38. Inhibition of Staphopain A significantly reduced the pathology associated with S. aureus keratitis, reducing the infecting numbers of bacteria from 1.8x10⁵ to <1x10⁴ cells/cornea (p ≤ 0.001), significantly reducing the corneal pathology score (p ≤ 0.038) and reducing the numbers of infiltrating PMNs. This study shows that Staphopain increases adhesion and invasion of corneal cells due to increasing fibronectin binding and its inhibition has a significant impact on pathogenicity of S. aureus during keratitis.

Phenotypic Characterization and Whole Genome Analysis of a Strong Biofilm-Forming Staphylococcus aureus Strain Associated With Subclinical Bovine Mastitis in Colombia

Staphylococcus aureus represent a serious threat to public health due to food safety, antibiotic resistance, and the potential zoonotic transmission of strains between dairy cattle and humans. Biofilm formation by S. aureus results in chronicity of the infections which confers protection against the immune response and antibiotics. Likewise, biofilm allows the exchange of mobile genetic material among different strains through microbial interactions inside the matrix. In Colombia, where S. aureus continues to be one of the main pathogens isolated from bovine intramammary infections and where milking by hand is highly frequent, there are knowledge gaps on the zoonotic potential of the strains. Therefore, the aim of this work was to characterize genotypically and phenotypically the S. aureus Sa1FB strain with strong biofilm production and to perform genomic and phenotypic comparisons with other relevant S. aureus strains (native and references strains). These results show a highly productive strain of biofilm and a low ability of cell invasion compared to the other two native strains. In addition, high genomic similarity between S. aureus Sa1FB and the reference strains was observed, despite of the differences reported at the clinical level. However, Sa1FB exhibited special features in terms of mobile genetic elements, highlighting its ability to accept foreign genetic material. Indeed, this could increase mutation, pathogenesis, and adaptability to new hosts, representing a risk for people in contact with the milk obtained from animals infected with these strains. These results present the relevance of surveillance for early detection of emergent clones with zoonotic potential, which reduces the risk of occupational exposure and their spread in the community.

Prevalence and Therapies of Antibiotic-Resistance in Staphylococcus aureus

Infectious diseases are the second most important cause of human death worldwide; Staphylococcus aureus (S. aureus) is a very common human pathogenic microorganism that can trigger a variety of infectious diseases, such as skin and soft tissue infections, endocarditis, osteomyelitis, bacteremia, and lethal pneumonia. Moreover, according to the sensitivity to antibiotic drugs, S. aureus can be divided into methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA). In recent decades, due to the evolution of bacteria and the abuse of antibiotics, the drug resistance of S. aureus has gradually increased, the infection rate of MRSA has increased worldwide, and the clinical anti-infective treatment for MRSA has become more difficult. Accumulating evidence has demonstrated that the resistance mechanisms of S. aureus are very complex, especially for MRSA, which is resistant to many kinds of antibiotics. Therefore, understanding the drug resistance of MRSA in a timely manner and elucidating its drug resistance mechanism at the molecular level are of great significance for the treatment of S. aureus infection. A large number of researchers believe that analyzing the molecular characteristics of S. aureus can help provide a basis for designing effective prevention and treatment measures against hospital infections caused by S. aureus and further monitor the evolution of S. aureus. This paper reviews the research status of MSSA and MRSA, the detailed mechanisms of the intrinsic antibiotic resistance and the acquired antibiotic resistance, the advanced research on anti-MRSA antibiotics and novel therapeutic strategies for MRSA treatment.

Staphylococcus aureus Pneumonia: Preceding Influenza Infection Paves the Way for Low-Virulent Strains

Staphylococcus aureus is a facultative pathogenic bacterium that colonizes the nasopharyngeal area of healthy individuals, but can also induce severe infection, such as pneumonia. Pneumonia caused by mono- or superinfected S.aureus leads to high mortality rates. To establish an infection, S. aureus disposes of a wide variety of virulence factors, which can vary between clinical isolates. Our study aimed to characterize pneumonia isolates for their virulent capacity. For this, we analyzed isolates from colonization, pneumonia due to S. aureus, and pneumonia due to S. aureus/influenza virus co-infection. A total of 70 strains were analyzed for their virulence genes and the host–pathogen interaction was analyzed through functional assays in cell culture systems. Strains from pneumonia due to S. aureus mono-infection showed enhanced invasion and cytotoxicity against professional phagocytes than colonizing and co-infecting strains. This corresponded to the high presence of cytotoxic components in pneumonia strains. By contrast, strains obtained from co-infection did not exhibit these virulence characteristics and resembled strains from colonization, although they caused the highest mortality rate in patients. Taken together, our results underline the requirement of invasion and toxins to cause pneumonia due to S. aureus mono-infection, whereas in co-infection even low-virulent strains can severely aggravate pneumonia.