Staphylococcus aureus biofilm: a complex developmental organism

Honeycomb-inspired ZIF-sealed interface enhances osseointegration via anti-infection and osteoimmunomodulation

Implant-associated infections (IAIs) pose a significant threat to orthopedic surgeries. Bacteria colonizing the surface of implants disrupt bone formation-related cells and interfere with the osteoimmune system, resulting in an impaired immune microenvironment and osteogenesis disorders. Inspired by nature, a zeolitic imidazolate framework (ZIF)-sealed smart drug delivery system on Ti substrates (ZSTG) was developed for the "natural-artificial dual-enzyme intervention (NADEI)" strategy to address these challenges. The subtle sealing design of ZIF-8 on the TiO2 nanotubes ensured glucose oxidase (GOx) activity and prevented its premature leakage. In the acidic infection microenvironment, the degradation of ZIF-8 triggered the rapid release of GOx, which converted glucose into H2O2 for disinfection. The Zn2+ released from degraded ZIF-8, as a DNase mimic, can hydrolyze extracellular DNA, which further enhances H2O2-induced disinfection and prevents biofilm formation. Importantly, Zn2+-mediated M2 macrophage polarization significantly improved the impaired osteoimmune microenvironment, accelerating bone repair. Transcriptomics revealed that ZSTG effectively suppressed the inflammatory cascade induced by lipopolysaccharide while promoting cell proliferation, homeostasis maintenance, and bone repair. In vitro and in vivo results confirmed the superior anti-infective, osteoimmunomodulatory, and osteointegrative capacities of the ZSTG-mediated NADEI strategy. Overall, this smart bionic platform has significant potential for future clinical applications to treat IAIs.

Molecular detection of virulence genes in Staphylococcus aureus isolated from wild pigeons (Columba domestica livia) in KwaZulu-Natal in South Africa

The current study aimed to determine virulence determinants among S. aureus isolated from wild pigeons and houseflies around hospital areas in the Greater Durban area, South Africa. Following enrichment and bacterial growth, DNA extraction using the boiling method was performed. Overall, 57 out of 252 samples (22.6%) were positive for S. aureus. Six known virulence genes were tested, where five known virulence determinants were positive and none of the S. aureus isolates were positive to coagulase (coa) gene. The highest prevalence rates were found in the genes encoding haemolysins, with the hla and hld genes having 8 (14%) and 9 (15.8%) positive isolates respectively. The sea, LukS/F-PV, and spa genes had 5 (8.8%), 4 (7%), and 2 (3.5%) positive isolates respectively. These results demonstrated the detection of pathogenic S. aureus from hospital environment in Durban, South Africa which may account for the emergence staphylococcal infections. The findings of the present study highlights the significant role of wild pigeons and houseflies as potenital infectious disease vectors in a One Health context.

SCCmec transformation requires living donor cells in mixed biofilms

Methicillin-resistant Staphylococcus aureus (MRSA) is an important human pathogen that has emerged through the horizontal acquisition of the staphylococcal cassette chromosome mec (SCCmec). Previously, we showed that SCCmec from heat-killed donors can be transferred via natural transformation in biofilms at frequencies of 10-8-10-7. Here, we show an improved transformation assay of SCCmec with frequencies up to 10-2 using co-cultured biofilms with living donor cells. The Ccr-attB system played an important role in SCCmec transfer, and the deletion of ccrAB recombinase genes reduced the frequency ∼30-fold. SCCmec could be transferred from either MRSA or methicillin-resistant coagulase-negative staphylococci to some methicillin-sensitive S. aureus recipients. In addition, the transformation of other plasmid or chromosomal genes is enhanced by using living donor cells. This study emphasizes the role of natural transformation as an evolutionary ability of S. aureus and in MRSA emergence.

A review of chemical signaling mechanisms underlying quorum sensing and its inhibition in Staphylococcus aureus

Staphylococcus aureus is a significant bacterium responsible for multiple infections and is a primary cause of fatalities among patients in hospital environments. The advent of pathogenic bacteria such as methicillin-resistant S. aureus revealed the shortcomings of employing antibiotics to treat bacterial infectious diseases. Quorum sensing enhances S. aureus's survivability through signaling processes. Targeting the key components of quorum sensing has drawn much interest nowadays as a promising strategy for combating infections caused by bacteria. Concentrating on the accessory gene regulator quorum-sensing mechanism is the most commonly suggested anti-virulence approach for S.aureus. Quorum quenching is a common strategy for controlling illnesses triggered by microorganisms since it reduces the pathogenicity of bacteria and improves bacterial biofilm susceptibility to antibiotics, thus providing an intriguing prospect for drug discovery. Quorum sensing inhibition reduces selective stresses and constrains the emergence of antibiotic resistance while limiting bacterial pathogenicity. This review examines the quorum sensing mechanisms involved in S. aureus, quorum sensing targets and gene regulation, environmental factors affecting quorum sensing, quorum sensing inhibition, natural products as quorum sensing inhibitory agents and novel therapeutical strategies to target quorum sensing in S. aureus as drug developing technique to augment conventional antibiotic approaches.

Prospects and challenges for the application of tissue engineering technologies in the treatment of bone infections

Osteomyelitis is a devastating disease caused by microbial infection in deep bone tissue. Its high recurrence rate and impaired restoration of bone deficiencies are major challenges in treatment. Microbes have evolved numerous mechanisms to effectively evade host intrinsic and adaptive immune attacks to persistently localize in the host, such as drug-resistant bacteria, biofilms, persister cells, intracellular bacteria, and small colony variants (SCVs). Moreover, microbial-mediated dysregulation of the bone immune microenvironment impedes the bone regeneration process, leading to impaired bone defect repair. Despite advances in surgical strategies and drug applications for the treatment of bone infections within the last decade, challenges remain in clinical management. The development and application of tissue engineering materials have provided new strategies for the treatment of bone infections, but a comprehensive review of their research progress is lacking. This review discusses the critical pathogenic mechanisms of microbes in the skeletal system and their immunomodulatory effects on bone regeneration, and highlights the prospects and challenges for the application of tissue engineering technologies in the treatment of bone infections. It will inform the development and translation of antimicrobial and bone repair tissue engineering materials for the management of bone infections.

Antibiofilm activity of carotenoid crocetin against Staphylococcal strains

Staphylococcus aureus and Staphylococcus epidermidis stand as notorious threats to human beings owing to the myriad of infections they cause. The bacteria readily form biofilms that help in withstanding the effects of antibiotics and the immune system. Intending to combat the biofilm formation and reduce the virulence of the pathogens, we investigated the effects of carotenoids, crocetin, and crocin, on four Staphylococcal strains. Crocetin was found to be the most effective as it diminished the biofilm formation of S. aureus ATCC 6538 significantly at 50 µg/mL without exhibiting bactericidal effect (MIC >800 µg/mL) and also inhibited the formation of biofilm by MSSA 25923 and S. epidermidis at a concentration as low as 2 µg/mL, and that by methicillin-resistant S. aureus MW2 at 100 µg/mL. It displayed minimal to no antibiofilm efficacy on the Gram-negative strains Escherichia coli O157:H7 and Pseudomonas aeruginosa as well as a fungal strain of Candida albicans. It could also curb the formation of fibrils, which partly contributes to the biofilm formation in S. epidermidis. Additionally, the ADME analysis of crocetin proclaims how relatively non-toxic the chemical is. Also, crocetin displayed synergistic antibiofilm characteristics in combination with tobramycin. The presence of a polyene chain with carboxylic acid groups at its ends is hypothesized to contribute to the strong antibiofilm characteristics of crocetin. These findings suggest that using apocarotenoids, particularly crocetin might help curb the biofilm formation by S. aureus and S. epidermidis.

Medical Device-Associated Biofilm Infections and Multidrug-Resistant Pathogens

Medical devices such as venous catheters (VCs) and urinary catheters (UCs) are widely used in the hospital setting. However, the implantation of these devices is often accompanied by complications. About 60 to 70% of nosocomial infections (NIs) are linked to biofilms. The main complication is the ability of microorganisms to adhere to surfaces and form biofilms which protect them and help them to persist in the host. Indeed, by crossing the skin barrier, the insertion of VC inevitably allows skin flora or accidental environmental contaminants to access the underlying tissues and cause fatal complications like bloodstream infections (BSIs). In fact, 80,000 central venous catheters-BSIs (CVC-BSIs)-mainly occur in intensive care units (ICUs) with a death rate of 12 to 25%. Similarly, catheter-associated urinary tract infections (CA-UTIs) are the most commonlyhospital-acquired infections (HAIs) worldwide.These infections represent up to 40% of NIs.In this review, we present a summary of biofilm formation steps. We provide an overview of two main and important infections in clinical settings linked to medical devices, namely the catheter-asociated bloodstream infections (CA-BSIs) and catheter-associated urinary tract infections (CA-UTIs), and highlight also the most multidrug resistant bacteria implicated in these infections. Furthermore, we draw attention toseveral useful prevention strategies, and advanced antimicrobial and antifouling approaches developed to reduce bacterial colonization on catheter surfaces and the incidence of the catheter-related infections.

Investigating the translational value of Periprosthetic Joint Infection (PJI) models to determine the risk and severity of Staphylococcal biofilms

With the advent of antibiotic-eluting polymeric materials for targeting recalcitrant infections, using preclinical models to study biofilm is crucial for improving the treatment efficacy in periprosthetic joint infections. The stratification of risk and severity of infections is needed to develop an effective clinical dosing framework with better outcomes. Here, using in-vivo and in-vitro implant-associated infection models, we demonstrate that methicillin-sensitive and resistant Staphylococcus aureus (MSSA and MRSA) have model-dependent distinct implant and peri-implant tissue colonization patterns. The maturity of biofilms and the location (implant vs tissue) were found to influence the antibiotic susceptibility evolution profiles of MSSA and MRSA and the models were able to capture the differing host-microbe interactions in vivo. Gene expression studies revealed the molecular heterogeneity of colonizing bacterial populations. The comparison and stratification of the risk and severity of infection across different preclinical models provided in this study can aid in guiding clinical dosing to effectively prevent or treat PJI.

Exploration of agr types, virulence-associated genes, and biofilm formation ability in Staphylococcus aureus isolates from hemodialysis patients with vascular access infections

Introduction

Staphylococcus aureus, is a pathogen commonly encountered in both community and hospital settings. Patients receiving hemodialysis treatment face an elevated risk of vascular access infections (VAIs) particularly Staphylococcus aureus, infection. This heightened risk is attributed to the characteristics of Staphylococcus aureus, , enabling it to adhere to suitable surfaces and form biofilms, thereby rendering it resistant to external interventions and complicating treatment efforts.

Methods

Therefore this study utilized PCR and microtiter dish biofilm formation assay to determine the difference in the virulence genes and biofilm formation among in our study collected of 103 Staphylococcus aureus, isolates from hemodialysis patients utilizing arteriovenous grafts (AVGs), tunneled cuffed catheters (TCCs), and arteriovenous fistulas (AVFs) during November 2013 to December 2021.

Results

Our findings revealed that both MRSA and MSSA isolates exhibited strong biofilm production capabilities. Additionally, we confirmed the presence of agr types and virulence genes through PCR analysis. The majority of the collected isolates were identified as agr type I. However, agr type II isolates displayed a higher average number of virulence genes, with MRSA isolates exhibiting a variety of virulence genes. Notably, combinations of biofilm-associated genes, such as eno-clfA-clfB-fib-icaA-icaD and eno-clfA-clfB-fib-fnbB-icaA-icaD, were prevalent among Staphylococcus aureus, isolates obtained from vascular access infections.

Discussion

These insights contribute to a better understanding of the molecular characteristics associated with Staphylococcus aureus, infections in hemodialysis patients and provided more targeted and effective treatment approaches.

Deciphering the dynamics of methicillin-resistant Staphylococcus aureus biofilm formation: from molecular signaling to nanotherapeutic advances

Methicillin-resistant Staphylococcus aureus (MRSA) represents a global threat, necessitating the development of effective solutions to combat this emerging superbug. In response to selective pressures within healthcare, community, and livestock settings, MRSA has evolved increased biofilm formation as a multifaceted virulence and defensive mechanism, enabling the bacterium to thrive in harsh conditions. This review discusses the molecular mechanisms contributing to biofilm formation across its developmental stages, hence representing a step forward in developing promising strategies for impeding or eradicating biofilms. During staphylococcal biofilm development, cell wall-anchored proteins attach bacterial cells to biotic or abiotic surfaces; extracellular polymeric substances build scaffolds for biofilm formation; the cidABC operon controls cell lysis within the biofilm, and proteases facilitate dispersal. Beside the three main sequential stages of biofilm formation (attachment, maturation, and dispersal), this review unveils two unique developmental stages in the biofilm formation process for MRSA; multiplication and exodus. We also highlighted the quorum sensing as a cell-to-cell communication process, allowing distant bacterial cells to adapt to the conditions surrounding the bacterial biofilm. In S. aureus, the quorum sensing process is mediated by autoinducing peptides (AIPs) as signaling molecules, with the accessory gene regulator system playing a pivotal role in orchestrating the production of AIPs and various virulence factors. Several quorum inhibitors showed promising anti-virulence and antibiofilm effects that vary in type and function according to the targeted molecule. Disrupting the biofilm architecture and eradicating sessile bacterial cells are crucial steps to prevent colonization on other surfaces or organs. In this context, nanoparticles emerge as efficient carriers for delivering antimicrobial and antibiofilm agents throughout the biofilm architecture. Although metal-based nanoparticles have been previously used in combatting biofilms, its non-degradability and toxicity within the human body presents a real challenge. Therefore, organic nanoparticles in conjunction with quorum inhibitors have been proposed as a promising strategy against biofilms. As nanotherapeutics continue to gain recognition as an antibiofilm strategy, the development of more antibiofilm nanotherapeutics could offer a promising solution to combat biofilm-mediated resistance.

Staphylococcus aureus and biofilms: transmission, threats, and promising strategies in animal husbandry

Staphylococcus aureus (S. aureus) is a common pathogenic bacterium in animal husbandry that can cause diseases such as mastitis, skin infections, arthritis, and other ailments. The formation of biofilms threatens and exacerbates S. aureus infection by allowing the bacteria to adhere to pathological areas and livestock product surfaces, thus triggering animal health crises and safety issues with livestock products. To solve this problem, in this review, we provide a brief overview of the harm caused by S. aureus and its biofilms on livestock and animal byproducts (meat and dairy products). We also describe the ways in which S. aureus spreads in animals and the threats it poses to the livestock industry. The processes and molecular mechanisms involved in biofilm formation are then explained. Finally, we discuss strategies for the removal and eradication of S. aureus and biofilms in animal husbandry, including the use of antimicrobial peptides, plant extracts, nanoparticles, phages, and antibodies. These strategies to reduce the spread of S. aureus in animal husbandry help maintain livestock health and improve productivity to ensure the ecologically sustainable development of animal husbandry and the safety of livestock products.

A review on antimicrobial strategies in mitigating biofilm-associated infections on medical implants

Biomedical implants are crucial in providing support and functionality to patients with missing or defective body parts. However, implants carry an inherent risk of bacterial infections that are biofilm-associated and lead to significant complications. These infections often result in implant failure, requiring replacement by surgical restoration. Given these complications, it is crucial to study the biofilm formation mechanism on various biomedical implants that will help prevent implant failures. Therefore, this comprehensive review explores various types of implants (e.g., dental implant, orthopedic implant, tracheal stent, breast implant, central venous catheter, cochlear implant, urinary catheter, intraocular lens, and heart valve) and medical devices (hemodialyzer and pacemaker) in use. In addition, the mechanism of biofilm formation on those implants, and their pathogenesis were discussed. Furthermore, this article critically reviews various approaches in combating implant-associated infections, with a special emphasis on novel non-antibiotic alternatives to mitigate biofilm infections.

Anatomical, pathological, and histological features of experimental respiratory infection of birds by biofilm-forming bacteria Staphylococcus aureus

Background and Aim

The pathogenesis of staphylococcal infections is mediated by virulence factors, such as enzymes, toxins, and biofilms, which increase the resistance of microorganisms to host immune system evasion. Testing and searching for standardized multi-level algorithms for the indication and differentiation of biofilms at the early stages of diagnosis will contribute to the development of preventive measures to control the critical points of technology and manage dangerous risk factors for the spread of infectious diseases. This research aimed to study the main stages of Staphylococcus aureus biofilm formation in in vitro experiments and to analyze the dynamics of respiratory syndrome development in chickens infected with these bacteria.

Materials and Methods

Experimental reproduction of the infectious process was performed using laboratory models: 10-day-old White Leghorn chickens (n = 20). Before the experiments, the birds were divided into two groups according to the principle of analogs: Group I (control, n = 10): the birds were intranasally inoculated with 0.5 cm3 of 0.9% NaCl solution; Group II (experiment, n = 10): the birds were intranasally inoculated with a suspension of S. aureus bacteria, 0.5 cm3, concentration 1 billion/cm3.

Results

Colonization of individual areas of the substrate under study in vitro occurred gradually from the sedimentation and adhesion of single motile planktonic cells to the attachment stage of microcolony development. Staining preparations with gentian violet due to the "metachromosia" property of this dye are a quick and fairly simple way to differentiate cells and the intercellular matrix of biofilms. Fixation with vapors of glutaraldehyde and osmium tetroxide preserves the natural architecture of biofilms under optical and scanning electron microscopy. Pure cultures of S. aureus microorganisms were isolated from the blood, lungs, small intestine, liver, kidneys, and spleen after 5-10 days during experimental infection of chickens. Clinical signs of respiratory syndrome developed within 5-6 days after infection. Acute and subacute serous-fibrinous airsacculitis, characterized by edema and thickening of the membranes of the air sacs and the presence of turbid, watery, foamy contents in the cavity, was the most characteristic pathomorphological sign. The signs of acute congestive hyperemia and one-sided serous-fibrinous pneumonia developed with significant thickening of fibrinous deposits. In Garder's gland, there was an increase in the number of secretory sections, indicating hypersecretion of the glands. In the lymphoid follicles of Meckel's diverticulum, leukocytes, usually lymphocytes, and pseudoeosinophils were detected.

Conclusions

Hydration and heteromorphism of the internal environment of biofilms determine the localization of differentiated cells in a three-dimensional matrix for protection against adverse factors. The most characteristic pathomorphological sign was the development of acute and subacute serous-fibrinous airsacculitis when reproducing the infectious process in susceptible models. There was a significant thickening of fibrinous deposits and signs of acute congestive hyperemia and one or two serous-fibrinous pneumonia developed.

The role of Staphylococcus aureus quorum sensing in cutaneous and systemic infections

BACKGROUND

Staphylococcus aureus is a leading cause of human bacterial infections worldwide. It is the most common causative agent of skin and soft tissue infections, and can also cause various other infections, including pneumonia, osteomyelitis, as well as life-threatening infections, such as sepsis and infective endocarditis. The pathogen can also asymptomatically colonize human skin, nasal cavity, and the intestine. S. aureus colonizes approximately 20-30% of human nostrils, being an opportunistic pathogen for subsequent infection. Its strong ability to silently spread via human contact makes it difficult to eradicate S. aureus. A major concern with S. aureus is its capacity to develop antibiotic resistance and adapt to diverse environmental conditions. The variability in the accessory gene regulator (Agr) region of the genome contributes to a spectrum of phenotypes within the bacterial population, enhancing the likelihood of survival in different environments. Agr functions as a central quorum sensing (QS) system in S. aureus, allowing bacteria to adjust gene expression in response to population density. Depending on Agr expression, S. aureus secretes various toxins, contributing to virulence in infectious diseases. Paradoxically, expressing Agr may be disadvantageous in certain situations, such as in hospitals, causing S. aureus to generate Agr mutants responsible for infections in healthcare settings.

MAIN BODY

This review aims to demonstrate the molecular mechanisms governing the diverse phenotypes of S. aureus, ranging from a harmless colonizer to an organism capable of infecting various human organs. Emphasis will be placed on QS and its role in orchestrating S. aureus behavior across different contexts.

SHORT CONCLUSION

The pathophysiology of S. aureus infection is substantially influenced by phenotypic changes resulting from factors beyond Agr. Future studies are expected to give the comprehensive understanding of S. aureus overall profile in various settings.

Fever-like temperature impacts on Staphylococcus aureus and Pseudomonas aeruginosa interaction, physiology, and virulence both in vitro and in vivo

BACKGROUND

Staphylococcus aureus (SA) and Pseudomonas aeruginosa (PA) cause a wide variety of bacterial infections and coinfections, showing a complex interaction that involves the production of different metabolites and metabolic changes. Temperature is a key factor for bacterial survival and virulence and within the host, bacteria could be exposed to an increment in temperature during fever development. We analyzed the previously unexplored effect of fever-like temperatures (39 °C) on S. aureus USA300 and P. aeruginosa PAO1 microaerobic mono- and co-cultures compared with 37 °C, by using RNAseq and physiological assays including in vivo experiments.

RESULTS

In general terms both temperature and co-culturing had a strong impact on both PA and SA with the exception of the temperature response of monocultured PA. We studied metabolic and virulence changes in both species. Altered metabolic features at 39 °C included arginine biosynthesis and the periplasmic glucose oxidation in S. aureus and P. aeruginosa monocultures respectively. When PA co-cultures were exposed at 39 °C, they upregulated ethanol oxidation-related genes along with an increment in organic acid accumulation. Regarding virulence factors, monocultured SA showed an increase in the mRNA expression of the agr operon and hld, pmsα, and pmsβ genes at 39 °C. Supported by mRNA data, we performed physiological experiments and detected and increment in hemolysis, staphyloxantin production, and a decrease in biofilm formation at 39 °C. On the side of PA monocultures, we observed an increase in extracellular lipase and protease and biofilm formation at 39 °C along with a decrease in the motility in correlation with changes observed at mRNA abundance. Additionally, we assessed host-pathogen interaction both in vitro and in vivo. S. aureus monocultured at 39οC showed a decrease in cellular invasion and an increase in IL-8-but not in IL-6-production by A549 cell line. PA also decreased its cellular invasion when monocultured at 39 °C and did not induce any change in IL-8 or IL-6 production. PA strongly increased cellular invasion when co-cultured at 37 and 39 °C. Finally, we observed increased lethality in mice intranasally inoculated with S. aureus monocultures pre-incubated at 39 °C and even higher levels when inoculated with co-cultures. The bacterial burden for P. aeruginosa was higher in liver when the mice were infected with co-cultures previously incubated at 39 °C comparing with 37 °C.

CONCLUSIONS

Our results highlight a relevant change in the virulence of bacterial opportunistic pathogens exposed to fever-like temperatures in presence of competitors, opening new questions related to bacteria-bacteria and host-pathogen interactions and coevolution.

Expression and characterization of novel chimeric endolysin CHAPk-SH3bk against biofilm-forming methicillin-resistant Staphylococcus aureus

The continuous evolution of antibiotic resistance in methicillin-resistant Staphylococcus aureus (MRSA) due to the misuse of antibiotics lays out the need for the development of new antimicrobials with higher activity and lower resistance. In this study, we have expressed novel chimeric endolysin CHAPk-SH3bk derived from LysK to investigate its antibacterial activity against planktonic and biofilm-forming MRSA. The molecular docking and MD simulation results identified critical amino acids (ASP47, ASP56, ARG71, and Gly74) of CHAPk domain responsible for its catalytic activity. Chimeric endolysin CHAPk-SH3bk showed an effective binding to peptidoglycan fragment using 14 hydrogen bonds. The in-vitro antibacterial assays displayed higher activity of CHAPk against planktonic MRSA with 2-log10 reduction in 2 h. Both CHAPk and CHAPk-SH3bk displayed bactericidal activity against MRSA with ∼4log10 and ∼3.5log10 reduction in 24 h. Biofilm reduction activity displayed CHAPk-SH3bk reduced 33 % and 60 % of hospital-associated ATCC®BAA-44™ and bovine origin SA1 respectively. The CHAPk treatment reduced 47 % of the preformed biofilm formed by bovine-origin MRSA SA1. This study indicates an effective reduction of preformed MRSA biofilms of human and animal origin using novel chimeric construct CHAPk-SH3bk. Stating that the combination and shuffling of different domains of phage endolysin potentially increase its bacteriolytic effectiveness against MRSA.

Safety and effectiveness of fifth generation cephalosporins for the treatment of methicillin-resistant staphylococcus aureus bloodstream infections: a narrative review exploring past, present, and future

INTRODUCTION

Methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infection (BSI) is a major issue in healthcare, since it is often associated with endocarditis or deep site foci. Relevant morbidity and mortality associated with MRSA-BSIs forced the development of new antibiotic strategies; in particular, this review will focus the attention on fifth-generation cephalosporins (ceftaroline/ceftobiprole), that are the only ß-lactams active against MRSA.

AREAS COVERED

The review discusses the available randomized controlled trials and real-world observational studies conducted on safety and effectiveness of ceftaroline/ceftobiprole for the treatment of MRSA-BSIs. Finally, a proposal of MRSA-BSI treatment flowchart, based on fifth-generation cephalosporins, is described.

EXPERT OPINION

The use of anti-MRSA cephalosporins is an acceptable choice either in monotherapy or combination therapy for the treatment of MRSA-BSIs due to their relevant effectiveness and safety. Particularly, their use may be advisable in combination therapy in case of severe infections (including endocarditis or persistent bacteriemia) or in monotherapy in subjects at higher risk of drugs-induced toxicity with older regimens. On the contrary, caution should be taken in case of suspected/ascertained central nervous system infections due to inconsistent data regarding penetration of these drugs in cerebrospinal fluid and brain tissues.

Identification of a Staphylococcus aureus amidase catalytic domain inhibitor to prevent biofilm formation by sequential virtual screening, molecular dynamics simulation and biological evaluation

Staphylococcus aureus (S. aureus) is one of the common causes of implant associated biofilm infections and their biofilms are resistant to antibiotics. S. aureus amidase (AM) protein, a cell wall hydrolase that cleaves the amide bond between N-acetylmuramic acid and L-alanine residue of the stem peptide, is several fold over-expressed under biofilm conditions. Previous studies demonstrated an autolysin mutant in S. aureus that lacks the AM protein, is highly impaired in biofilm development. We carried out a structure-based small molecule design using the crystal structure of AM protein catalytic domain to identify inhibitors that can block amidase activity and therefore inhibits S. aureus biofilm formation. Sequential virtual screening followed by pharmacokinetic analysis and bioassay studies filtered 25 small molecules from different databases. Two compounds from the SPECS database, SPECS-1 and SPECS-2, were selected based on the best docking score and minimum biofilm inhibitory concentration towards S. aureus biofilms. SPECS-1 and SPECS-2 were further tested for their structural/energetic stability in complex with the AM protein using molecular dynamics simulation and MM-GBSA techniques. In vitro, biofilm inhibition studies on different surfaces confirmed that treatment with SPECS-1 and SPECS-2 at a concentration of 250 μg/ml exhibited significant prevention and disruption of S. aureus biofilms. Finally, the in vitro anti-biofilm activities of these two compounds were validated against Methicillin-resistant S. aureus clinical isolates. We concluded that the discovered compounds SPECS-1 and SPECS-2 are safe and exhibit biofilm preventive and disruption activity for inhibiting the S. aureus biofilms and hence can be used to treat implant-associated biofilm infections.

Development and Regulation of the Extreme Biofilm Formation of Deinococcus radiodurans R1 under Extreme Environmental Conditions

To grow in various harsh environments, extremophiles have developed extraordinary strategies such as biofilm formation, which is an extremely complex and progressive process. However, the genetic elements and exact mechanisms underlying extreme biofilm formation remain enigmatic. Here, we characterized the biofilm-forming ability of Deinococcus radiodurans in vitro under extreme environmental conditions and found that extremely high concentrations of NaCl or sorbitol could induce biofilm formation. Meantime, the survival ability of biofilm cells was superior to that of planktonic cells in different extreme conditions, such as hydrogen peroxide stress, sorbitol stress, and high UV radiation. Transcriptome profiles of D. radiodurans in four different biofilm development stages further revealed that only 13 matched genes, which are involved in environmental information processing, carbohydrate metabolism, or stress responses, share sequence homology with genes related to the biofilm formation of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. Overall, 64% of the differentially expressed genes are functionally unknown, indicating the specificity of the regulatory network of D. radiodurans. The mutation of the drRRA gene encoding a response regulator strongly impaired biofilm formation ability, implying that DrRRA is an essential component of the biofilm formation of D. radiodurans. Furthermore, transcripts from both the wild type and the drRRA mutant were compared, showing that the expression of drBON1 (Deinococcus radioduransBON domain-containing protein 1) significantly decreased in the drRRA mutant during biofilm development. Further analysis revealed that the drBON1 mutant lacked the ability to form biofilm and DrRRA, and as a facilitator of biofilm formation, could directly stimulate the transcription of the biofilm-related gene drBON1. Overall, our work highlights a molecular mechanism mediated by the response regulator DrRRA for controlling extreme biofilm formation and thus provides guidance for future studies to investigate novel mechanisms that are used by D. radiodurans to adapt to extreme environments.

Repurposing of the antimalarial agent tafenoquine to combat MRSA

IMPORTANCE

This study represents the first investigation into the antimicrobial effect of TAF against S. aureus and its potential mechanisms. Our data highlighted the effects of TAF against MRSA planktonic cells, biofilms, and persister cells, which is conducive to broadening the application of TAF. Through mechanistic studies, we revealed that TAF targets bacterial cell membranes. In addition, the in vivo experiments in mice demonstrated the safety and antimicrobial efficacy of TAF, suggesting that TAF could be a potential antibacterial drug candidate for the treatment of infections caused by multiple drug-resistant S. aureus.

Host-microbe interactions in chronic rhinosinusitis biofilms and models for investigation

Chronic rhinosinusitis (CRS) is a debilitating condition characterized by long-lasting inflammation of the paranasal sinuses. It affects a significant portion of the population, causing a considerable burden on individuals and healthcare systems. The pathogenesis of CRS is multifactorial, with bacterial infections playing a crucial role in CRS development and persistence. In recent years, the presence of biofilms has emerged as a key contributor to the chronicity of sinusitis, further complicating treatment and exacerbating symptoms. This review aims to explore the role of biofilms in CRS, focusing on the involvement of the bacterial species Staphylococcus aureus and Pseudomonas aeruginosa, their interactions in chronic infections, and model systems for studying biofilms in CRS. These species serve as an example of how microbial interplay can influence disease progression and exemplify the need for continued investigation and innovation in CRS research.

Bacteriophage endolysin Ply113 as a potent antibacterial agent against polymicrobial biofilms formed by enterococci and Staphylococcus aureus

Antibiotic resistance in Enterococcus faecium, Enterococcus faecalis, and Staphylococcus aureus remains a major public health concern worldwide. Furthermore, these microbes frequently co-exist in biofilm-associated infections, largely nullifying antibiotic-based therapy. Therefore, it is imperative to develop an efficient therapeutic strategy for combating infections caused by polymicrobial biofilms. In this study, we investigated the antibacterial and antibiofilm activity of the bacteriophage endolysin Ply113 in vitro. Ply113 exhibited high and rapid lytic activity against E. faecium, E. faecalis, and S. aureus, including vancomycin-resistant Enterococcus and methicillin-resistant S. aureus isolates. Transmission electron microscopy revealed that Ply113 treatment led to the detachment of bacterial cell walls and considerable cell lysis. Ply113 maintained stable lytic activity over a temperature range of 4-45°C, over a pH range of 5.0-8.0, and in the presence of 0-400 mM NaCl. Ply113 treatment effectively eliminated the mono-species biofilms formed by E. faecium, E. faecalis, and S. aureus in a dose-dependent manner. Ply113 was also able to eliminate the dual-species biofilms of E. faecium-S. aureus and E. faecalis-S. aureus. Additionally, Ply113 exerted potent antibacterial efficacy in vivo, distinctly decreasing the bacterial loads in a murine peritoneal septicemia model. Our findings suggest that the bacteriophage endolysin Ply113 is a promising antimicrobial agent for the treatment of polymicrobial infections.

Staphylococcal superantigen-like protein 10 enhances the amyloidogenic biofilm formation in Staphylococcus aureus

Staphylococcus aureus is a highly infectious pathogen that represents a significant burden on the current healthcare system. Bacterial attachment to medical implants and host tissue, and the establishment of a mature biofilm, play an important role in chronic diseases such as endocarditis, osteomyelitis and wound infections. These biofilms decrease bacterial susceptibility to antibiotics and immune defences, making the infections challenging to treatment. S. aureus produces numerous exotoxins that contribute to the pathogenesis of the bacteria. In this study, we have identified a novel function of staphylococcal superantigen-like protein 10 (SSL10) in enhancing the formation of staphylococcal biofilms. Biofilm biomass is significantly increased when SSL10 is added exogenously to bacterial cultures, whereas SSL2 and SSL12 are found to be less active. Exogenously added SSL10 mask the surface charge of the bacterial cells and lowers their zeta potential, leading to the aggregation of the cells. Moreover, the biofilm formation by SSL10 is governed by amyloid aggregation, as evident from spectroscopic and microscopic studies. These findings thereby give the first overview of the SSL-mediated amyloid-based biofilm formation and further drive the future research in identifying potential molecules for developing new antibacterial therapies against Staphylococcus aureus.

Characteristics of Staphylococcus aureus biofilm matured in tryptic soy broth, low-fat milk, or whole milk samples along with inactivation by 405 nm light combined with folic acid

In the present study, the characteristics of Staphylococcus aureus biofilms matured in tryptic soy broth (TSB), low-fat milk, or whole milk samples were identified along with their resistance to 405 nm light with or without folic acid. Phenotypic properties of carbohydrate and protein contents in extracellular polymeric substance (EPS) of S. aureus biofilms matured in different conditions were identified. The carbohydrate content was higher in the biofilm matured in low-fat milk (1.27) than the samples matured in whole milk (0.58) and TSB (0.10). Protein content in the EPS of biofilm was higher in the sample matured in whole milk (6.59) than the samples matured in low-fat milk (3.24) and TSB (2.08). Moreover, the maturation condition had a significant effect on the membrane lipid composition of the biofilm, producing more unsaturated fatty acids in biofilm matured in milk samples. These changes in biofilm matured in milk samples increased the resistance of S. aureus to 405 nm light in the presence of folic acid (LFA). Additionally, transcriptomic analysis was conducted to identify the response of S. aureus biofilm to LFA treatment. Several genes related to DNA and protein protection from oxidative stress along with biofilm accumulation were overexpressed in the LFA-treated biofilms. These results indicate the maturation of S. aureus biofilm in various samples and the biofilms responses to bactericidal treatments.

Insights into the Mechanisms of Reuterin against Staphylococcus aureus Based on Membrane Damage and Untargeted Metabolomics

Reuterin is a dynamic small-molecule complex produced through glycerol fermentation by Limosilactobacillus reuteri and has potential as a food biopreservative. Despite its broad-spectrum antimicrobial activity, the underlying mechanism of action of reuterin is still elusive. The present paper aimed to explore the antibacterial mechanism of reuterin and its effects on membrane damage and the intracellular metabolome of S. aureus. Our results showed that reuterin has a minimum inhibitory concentration of 18.25 mM against S. aureus, based on the 3-hydroxypropionaldehyde level. Key indicators such as extracellular electrical conductivity, membrane potential and permeability were significantly increased, while intracellular pH, ATP and DNA were markedly decreased, implying that reuterin causes a disruption to the structure of the cell membrane. The morphological damage to the cells was confirmed by scanning electron microscopy. Subsequent metabolomic analysis identified significant alterations in metabolites primarily involved in lipid, amino acid, carbohydrate metabolism and phosphotransferase system, which is crucial for cell membrane regulation and energy supply. Consequently, these findings indicated that the antibacterial mechanism of reuterin initially targets lipid and amino acid metabolism, leading to cell membrane damage, which subsequently results in energy metabolism disorder and, ultimately, cell death. This paper offers innovative perspectives on the antibacterial mechanism of reuterin, contributing to its potential application as a food preservative.

Photodynamic toluidine blue-gold nanoconjugates as a novel therapeutic for Staphylococcal biofilms

Staphylococci are among the most frequent bacteria known to cause biofilm-related infections. Pathogenic biofilms represent a global healthcare challenge due to their high tolerance to antimicrobials. In this study, water soluble polyethylene glycol (PEG)-coated gold nanospheres (28 ppm) and nanostars (15 ppm) with electrostatically adsorbed photosensitizer (PS) Toluidine Blue O (TBO) ∼4 μM were successfully synthesized and characterized as PEG-GNPs@TBO and PEG-GNSs@TBO. Both nanoconjugates and the TBO 4 μM solution showed remarkable, if similar, antimicrobial photodynamic inactivation (aPDI) effects at 638 nm, inhibiting the formation of biofilms by two Staphylococcal strains: a clinical methicillin-resistant Staphylococcus aureus (MRSA) isolate and Staphylococcus epidermidis (S. epidermidis) RP62A. Alternatively in biofilm eradication treatments, the aPDI effects of PEG-GNSs@TBO were more effective and yielded a 75% and 50% reduction in viable count of MRSA and S. epidermidis RP62A preformed biofilms, respectively and when compared with untreated samples. This reduction in viable count was even greater than that obtained through aPDI treatment using a 40 μM TBO solution. Confocal laser microscopy (CLSM) and scanning electron microscope (SEM) images of PEG-GNSs@TBO's aPDI treatments revealed significant changes in the integrity and morphology of biofilms, with fewer colony masses. The generation of reactive oxygen species (ROS) upon PEG-GNSs@TBO's aPDI treatment was detected by CLSM using a specific ROS fluorescent probe, demonstrating bright fluorescence red spots across the surfaces of the treated biofilms. Our findings shine a light on the potential synergism between gold nanoparticles (AuNPs) and photosensitizers in developing novel nanoplatforms to target Staphylococcal biofilm related infections.

The Controversial Effect of Antibiotics on Methicillin-Sensitive S. aureus: A Comparative In Vitro Study

Methicillin-sensitive Staphylococcus (S.) aureus (MSSA) bacteremia remains a global challenge, despite the availability of antibiotics. Primary treatments include β-lactam agents such as cefazolin and flucloxacillin. Ongoing discussions have focused on the potential synergistic effects of combining these agents with rifampicin or fosfomycin to combat infections associated with biofilm formation. Managing staphylococcal infections is challenging due to antibacterial resistance, biofilms, and S. aureus's ability to invade and replicate within host cells. Intracellular invasion shields the bacteria from antibacterial agents and the immune system, often leading to incomplete bacterial clearance and chronic infections. Additionally, S. aureus can assume a dormant phenotype, known as the small colony variant (SCV), further complicating eradication and promoting persistence. This study investigated the impact of antibiotic combinations on the persistence of S. aureus 6850 and its stable small colony variant (SCV strain JB1) focusing on intracellular survival and biofilm formation. The results from the wild-type strain 6850 demonstrate that β-lactams combined with RIF effectively eliminated biofilms and intracellular bacteria but tend to select for SCVs in planktonic culture and host cells. Higher antibiotic concentrations were associated with an increase in the zeta potential of S. aureus, suggesting reduced membrane permeability to antimicrobials. When using the stable SCV mutant strain JB1, antibiotic combinations with rifampicin successfully cleared planktonic bacteria and biofilms but failed to eradicate intracellular bacteria. Given these findings, it is reasonable to report that β-lactams combined with rifampicin represent the optimal treatment for MSSA bacteremia. However, caution is warranted when employing this treatment over an extended period, as it may elevate the risk of selecting for small colony variants (SCVs) and, consequently, promoting bacterial persistence.

Carbon-infiltrated carbon nanotubes inhibit the development of Staphylococcus aureus biofilms

Staphylococcus aureus forms biofilms that cause considerable morbidity and mortality in patients who receive implanted devices such as prosthetics or fixator pins. An ideal surface for such medical devices would inhibit biofilm growth. Recently, it was reported that surface modification of stainless steel materials with carbon-infiltrated carbon nanotubes (CICNT) inhibits the growth of S. aureus biofilms. The purpose of this study was to investigate this antimicrobial effect on titanium materials with CICNT coated surfaces in a variety of surface morphologies and across a broader spectrum of S. aureus isolates. Study samples of CICNT-coated titanium, and control samples of bare titanium, a common implant material, were exposed to S. aureus. Viable bacteria were removed from adhered biofilms and quantified as colony forming units. Scanning electron microscopy was used to qualitatively analyze biofilms both before and after removal of cells. The CICNT surface was found to have significantly fewer adherent bacteria than bare titanium control surfaces, both via colony forming unit and microscopic analyses. This effect was most pronounced on CICNT surfaces with an average nanotube diameter of 150 nm, showing a 2.5-fold reduction in adherent bacteria. Since S. aureus forms different biofilm structures by isolate and by growth conditions, we tested 7 total isolates and found a significant reduction in the biofilm load in six out of seven S. aureus isolates tested. To examine whether the anti-biofilm effect was due to the structure of the nanotubes, we generated an unstructured carbon surface. Significantly more bacteria adhered to a nonstructured carbon surface than to the 150 nm CICNT surface, suggesting that the topography of the nanotube structure itself has anti-biofilm properties. The CICNT surface possesses anti-biofilm properties that result in fewer adherent S. aureus bacteria. These anti-biofilm properties are consistent across multiple isolates of S. aureus and are affected by nanotube diameter. The experiments performed in this study suggest that this effect is due to the nanostructure of the CICNT surface.

S. aureus biofilm metabolic activity correlates positively with patients' eosinophil frequencies and disease severity in chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is a persistent inflammation of the sinus mucosa. Recalcitrant CRS patients are unresponsive to medical and surgical interventions and often present with nasal polyps, tissue eosinophilia, and Staphylococcus aureus dominant mucosal biofilms. However, S. aureus sinonasal mucosal colonisation occurs in the absence of inflammation, questioning the role of S. aureus in CRS pathogenesis. Here, we aimed to investigate the relationship between S. aureus biofilm metabolic activity and virulence genes, innate immune cells, and disease severity in CRS. Biospecimens, including sinonasal tissue and nasal swabs, and clinical datasets, including disease severity scores, were obtained from CRS patients and non-CRS controls. S. aureus isolates were grown into biofilms in vitro, characterised, and sequenced. The patients' innate immune response was evaluated using flow cytometry. S. aureus was isolated in 6/19 (31.58%) controls and 23/53 (43.40%) CRS patients of 72 recruited patients. We found increased S. aureus biofilm metabolic activity in relation to increased eosinophil cell frequencies and disease severity in recalcitrant CRS cases. Mast cell frequencies were higher in tissue samples of patients carrying S. aureus harbouring lukF.PV, sea, and fnbB genes. Patients with S. aureus harbouring lukF.PV and sdrE genes had more severe disease. This offers insights into the pathophysiology of CRS and could lead to the development of more targeted therapies.

A New In Vitro Blood Flow Model for the Realistic Evaluation of Antimicrobial Surfaces

Device-associated bloodstream infections can cause serious medical problems and cost-intensive postinfection management, defining a need for more effective antimicrobial coatings. Newly developed coatings often show reduced bacterial colonization and high hemocompatibility in established in vitro tests, but fail in animal studies or clinical trials. The poor predictive power of these models is attributed to inadequate representation of in vivo conditions. Herein, a new single-pass blood flow model, with simultaneous incubation of the test surface with bacteria and freshly-drawn human blood, is presented. The flow model is validated by comparative analysis of a recently developed set of antiadhesive and contact-killing polymer coatings, and the corresponding uncoated polycarbonate surfaces. The results confirm the model's ability to differentiate the antimicrobial activities of the studied surfaces. Blood activation data correlate with bacterial surface coverage: low bacterial adhesion is associated with low inflammation and hemostasis. Shear stress correlates inversely with bacterial colonization, especially on antiadhesive surfaces. The introduced model is concluded to enable the evaluation of novel antimicrobial materials under in vivo-like conditions, capturing interactions between bacteria and biomaterials surfaces in the presence of key components of the ex vivo host response.

Antimicrobial peptidase lysostaphin at subinhibitory concentrations modulates staphylococcal adherence, biofilm formation, and toxin production

BACKGROUND

The ability of antimicrobial agents to affect microbial adherence to eukaryotic cell surfaces is a promising antivirulence strategy for combating the global threat of antimicrobial resistance. Inadequate use of antimicrobials has led to widespread instances of suboptimal antibiotic concentrations around infection sites. Therefore, we aimed to examine the varying effect of an antimicrobial peptidase lysostaphin (APLss) on staphylococcal adherence to host cells, biofilm biomass formation, and toxin production as a probable method for mitigating staphylococcal virulence.

RESULTS

Initially, soluble expression in E. coli and subsequent purification by immobilized-Ni2+ affinity chromatography (IMAC) enabled us to successfully produce a large quantity of highly pure ~ 28-kDa His-tagged mature APLss. The purified protein exhibited potent inhibitory effects against both methicillin-sensitive and methicillin-resistant staphylococcal strains, with minimal inhibitory concentrations (MICs) ranging from 1 to 2 µg/mL, and ultrastructural analysis revealed that APLss-induced concentration-specific changes in the morphological architecture of staphylococcal surface membranes. Furthermore, spectrophotometric and fluorescence microscopy revealed that incubating staphylococcal strains with sub-MIC and MIC of APLss significantly inhibited staphylococcal adherence to human vaginal epithelial cells and biofilm biomass formation. Ultimately, transcriptional investigations revealed that APLss inhibited the expression of agrA (quorum sensing effector) and other virulence genes related to toxin synthesis.

CONCLUSIONS

Overall, APLss dose-dependently inhibited adhesion to host cell surfaces and staphylococcal-associated virulence factors, warranting further investigation as a potential anti-staphylococcal agent with an antiadhesive mechanism of action using in vivo models of staphylococcal toxic shock syndrome.

Teat-apex colonizer Bacillus from healthy cows antagonizes mastitis-causing Staphylococcus aureus biofilms

Staphylococcus aureus is the most frequent causal agent of bovine mastitis, which is largely responsible for milk production losses worldwide. The pathogen's ability to form stable biofilms facilitates intramammary colonization and may explain disease persistence. This virulence factor is also highly influential in the development of chronic intramammary infections refractory to antimicrobial therapy, which is why novel therapies that can tackle multiple targets are necessary. Since udder microbiota have important implications in mastitis pathogenesis, they offer opportunities to develop alternative prophylactic and therapeutic strategies. Here, we observed that a Bacillus strain from the teat apex of lactating cows was associated to reduce colonization by S. aureus. The strain, identified as Bacillus sp. H21, was able to antagonize in-formation or mature S. aureus biofilms associated to intramammary infections without affecting cell viability. When exploring the metabolite responsible for this activity, we found that a widespread class of Bacillus exopolysaccharide, levan, eliminated the pathogenic biofilm under evaluated conditions. Moreover, levan had no cytotoxic effects on bovine cellular lines at the biologically active concentration range, which demonstrates its potential for pathogen control. Our results indicate that commensal Bacillus may counteract S. aureus-induced mastitis, and could therefore be used in novel biotechnological strategies to prevent and/or treat this disease.

Advancing understanding of microbial biofilms through machine learning-powered studies

Microbial biofilms are prevalent in various environments and pose significant challenges to food safety and public health. The biofilms formed by pathogens can cause food spoilage, foodborne illness, and infectious diseases, which are difficult to treat due to their enhanced antimicrobial resistance. While the composition and development of biofilms have been widely studied, their profound impact on food, the food industry, and public health has not been sufficiently recapitulated. This review aims to provide a comprehensive overview of microbial biofilms in the food industry and their implication on public health. It highlights the existence of biofilms along the food-producing chains and the underlying mechanisms of biofilm-associated diseases. Furthermore, this review thoroughly summarizes the enhanced understanding of microbial biofilms achieved through machine learning approaches in biofilm research. By consolidating existing knowledge, this review intends to facilitate developing effective strategies to combat biofilm-associated infections in both the food industry and public health.

The combinatorial applications of 1,4-naphthoquinone and tryptophan inhibit the biofilm formation of Staphylococcus aureus

Microorganisms embedded within an extracellular polymeric matrix are known as biofilm. The extensive use of antibiotics to overcome the biofilm-linked challenges has led to the emergence of multidrug-resistant strains. Staphylococcus aureus is one such nosocomial pathogen that is known to cause biofilm-linked infections. Thus, novel strategies have been adopted in this study to inhibit the biofilm formation of S. aureus. Two natural compounds, namely, 1,4-naphthoquinone (a quinone derivative) and tryptophan (aromatic amino acid), have been chosen as they could independently show efficient antibiofilm activity. To enhance the antibiofilm potential, the two compounds were combined and tested against the same organism. Several experiments like crystal violet (CV) assay, protein estimation, extracellular polymeric substance (EPS) extraction, and estimation of metabolic activity confirmed that the combination of the two compounds could significantly inhibit the biofilm formation of S. aureus. To comprehend the underlying mechanism, efforts were further directed to understand whether the two compounds could inhibit biofilm formation by compromising the cell surface hydrophobicity of the bacteria. The results revealed that the cell surface hydrophobicity got reduced by ~ 49% when the compounds were applied together. Thus, the combinations could show enhanced antibiofilm activity by attenuating cell surface hydrophobicity. Further studies revealed that the selected concentrations of the compounds could disintegrate (~ 70%) the pre-existing biofilm of the test bacteria without showing any antimicrobial activity. Hence, the combined application of tryptophan and 1,4-naphthoquinone could be used to inhibit the biofilm threats of S. aureus.

Probiotics and Their Bioproducts: A Promising Approach for Targeting Methicillin-Resistant Staphylococcus aureus and Vancomycin-Resistant Enterococcus

Antibiotic resistance is a serious global health problem that poses a threat to the successful treatment of various bacterial infections, especially those caused by methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE). Conventional treatment of MRSA and VRE infections is challenging and often requires alternative or combination therapies that may have limited efficacy, higher costs, and/or more adverse effects. Therefore, there is an urgent need to find new strategies to combat antibiotic-resistant bacteria. Probiotics and antimicrobial peptides (AMPs) are two promising approaches that have shown potential benefits in various diseases. Probiotics are live microorganisms that confer health benefits to the host when administered in adequate amounts. AMPs, usually produced with probiotic bacteria, are short amino acid sequences that have broad-spectrum activity against bacteria, fungi, viruses, and parasites. Both probiotics and AMPs can modulate the host immune system, inhibit the growth and adhesion of pathogens, disrupt biofilms, and enhance intestinal barrier function. In this paper, we review the current knowledge on the role of probiotics and AMPs in targeting multi-drug-resistant bacteria, with a focus on MRSA and VRE. In addition, we discuss future directions for the clinical use of probiotics.

The biofilm proteome of Staphylococcus aureus and its implications for therapeutic interventions to biofilm-associated infections

Staphylococcus aureus is a major healthcare concern due to its ability to inflict life-threatening infections and evolve antibiotic resistance at an alarming pace. It is frequently associated with hospital-acquired infections, especially device-associated infections. Systemic infections due to S. aureus are difficult to treat and are associated with significant mortality and morbidity. The situation is worsened by the ability of S. aureus to form social associations called biofilms. Biofilms embed a community of cells with the ability to communicate with each other and share resources within a polysaccharide or protein matrix. S. aureus establish biofilms on tissues and conditioned abiotic surfaces. Biofilms are hyper-tolerant to antibiotics and help evade host immune responses. Biofilms exacerbate the severity and recalcitrance of device-associated infections. The development of a biofilm involves various biomolecules, such as polysaccharides, proteins and nucleic acids, contributing to different structural and functional roles. Interconnected signaling pathways and regulatory molecules modulate the expression of these molecules. A comprehensive understanding of the molecular biology of biofilm development would help to devise effective anti-biofilm therapeutics. Although bactericidal agents, antimicrobial peptides, bacteriophages and nano-conjugated anti-biofilm agents have been employed with varying levels of success, there is still a requirement for effective and clinically viable anti-biofilm therapeutics. Proteins that are expressed and utilized during biofilm formation, constituting the biofilm proteome, are a particularly attractive target for anti-biofilm strategies. The proteome can be explored to identify potential anti-biofilm drug targets and utilized for rational drug discovery. With the aim of uncovering the biofilm proteome, this chapter explores the mechanism of biofilm formation and its regulation. Furthermore, it explores the antibiofilm therapeutics targeted against the biofilm proteome.

Surface grafting of polymeric catheters and stents to prevent biofilm formation of pathogenic bacteria

BACKGROUND

Tecothane (medical grade of polyurethane) is strongly involved in the fabrication of metallic and polymeric-based medical devices (e.g., catheters and stents) as they can withstand cardiac cycle-related forces without deforming or failing, and they can mimic tissue behavior. The main problem is microbial contamination and formation of pathogenic biofilms on such solid surfaces within the human body. Accordingly, our hypothesis is the coating of tecothane outer surfaces with antibacterial agents through the electro-deposition or chemical grafting of anti-biofilm agents onto the stent and catheter surfaces.

RESULTS

Tecothane is grafted with itaconic acid for cross-linking the polyethyleneimine (PEI) as the protective-active layer. Accordingly, the grafting of poly-itaconic acid onto the Tecothane was achieved by three different methods: wet-chemical approach, electro-polymerization, or by using plasma treatment. The successful modifications were verified using Fourier Transform Infrared (FTIR) spectroscopy, grafting percentage calculations, electrochemical, and microscopic monitoring of biofilm formation. The grafting efficiency of itaconic acid was over 3.2% (w/w) at 60 ℃ after 6 h of the catheter chemical modification. Bio-electrochemical signals of biofilms have been seriously reduced after chemical modification because of the inhibition of biofilm formation (for both Pseudomonas aeruginosa and Staphylococcus aureus) over a period of 9 days.

CONCLUSION

Chemical functionalization of the polyurethane materials with the antimicrobial and anti-biofilm agents led to a significant decrease in the formation of pathogenic biofilms. This promising proof-concept will open the door to explore further surface protection with potential anti-biofilm agents providing better and sustainable productions of stents and catheters biomaterials.

Antivirulence activities of retinoic acids against Staphylococcus aureus

Multidrug-resistant bacteria such as Staphylococcus aureus constitute a global health problem. Gram-positive S. aureus secretes various toxins associated with its pathogenesis, and its biofilm formation plays an important role in antibiotic tolerance and virulence. Hence, we investigated if the metabolites of vitamin A1 might diminish S. aureus biofilm formation and toxin production. Of the three retinoic acids examined, 13-cis-retinoic acid at 10 μg/mL significantly decreased S. aureus biofilm formation without affecting its planktonic cell growth (MIC >400 μg/mL) and also inhibited biofilm formation by Staphylococcus epidermidis (MIC >400 μg/mL), but less affected biofilm formation by a uropathogenic Escherichia coli strain, a Vibrio strain, or a fungal Candida strain. Notably, 13-cis-retinoic acid and all-trans-retinoic acid significantly inhibited the hemolytic activity and staphyloxanthin production by S. aureus. Furthermore, transcriptional analysis disclosed that 13-cis-retinoic acid repressed the expressions of virulence- and biofilm-related genes, such as the two-component arlRS system, α-hemolysin hla, nuclease (nuc1 and nuc2), and psmα (phenol soluble modulins α) in S. aureus. In addition, plant and nematode toxicity assays showed that 13-cis-retinoic acid was only mildly toxic at concentrations many folds higher than its effective antibiofilm concentrations. These findings suggest that metabolites of vitamin A1, particularly 13-cis-retinoic acid, might be useful for suppressing biofilm formation and the virulence characteristics of S. aureus.

Cyclodextrin: A prospective nanocarrier for the delivery of antibacterial agents against bacteria that are resistant to antibiotics

Supramolecular chemistry introduces us to the macrocyclic host cyclodextrin, which has a hydrophobic cavity. The hydrophobic cavity has a higher affinity for hydrophobic guest molecules and forms host-guest complexation with non-covalent interaction. Three significant cyclodextrin kinds are α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin. The most often utilized is β-cyclodextrin (β-CD). An effective weapon against bacteria that are resistant to antibiotics is cyclodextrin. Several different kinds of cyclodextrin nanocarriers (β-CD, HP-β-CD, Meth-β-CD, cationic CD, sugar-grafted CD) are utilized to enhance the solubility, stability, dissolution, absorption, bioavailability, and permeability of the antibiotics. Cyclodextrin also improves the effectiveness of antibiotics, antimicrobial peptides, metallic nanoparticles, and photodynamic therapy (PDT). Again, cyclodextrin nanocarriers offer slow-release properties for sustained-release formulations where steady-state plasma antibiotic concentration is needed for an extended time. A novel strategy to combat bacterial resistance is a stimulus (pH, ROS)-responsive antibiotics released from cyclodextrin carrier. Once again, cyclodextrin traps autoinducer (AI), a crucial part of bacterial quorum sensing, and reduces virulence factors, including biofilm formation. Cyclodextrin helps to minimize MIC in particular bacterial strains, keep antibiotic concentrations above MIC in the infection site and minimize the possibility of antibiotic and biofilm resistance. Sessile bacteria trapped in biofilms are more resistant to antibiotic therapy than bacteria in a planktonic form. Cyclodextrin also involves delivering antibiotics to biofilm and resistant bacteria to combat bacterial resistance.

Evaluation of the Antibacterial Effect of Aurone-Derived Triazoles on Staphylococcus aureus

Infections caused by antibiotic-resistant bacteria continue to pose a significant public health threat despite their overall decreasing numbers in the last two decades. One group of compounds fundamental to the search for new agents is low-cost natural products. In this study, we explored a group of newly synthesized novel aurone-derived triazole compounds to identify those with pharmaceutical potential as inhibitors of antibiotic-resistant Staphylococcus aureus. Using the broth microdilution method, antibacterial activities against methicillin-resistant S. aureus ATCC 43300 (MRSA) and methicillin-sensitive S. aureus ATCC 29213 (MSSA) were identified for four aurone-derived triazole compounds, AT106, AT116, AT125, and AT137, using the half-maximal inhibitory concentrations for the bacteria (IC50) and mammalian cell lines (CC50). Compounds AT125 and AT137 were identified to have pharmaceutical potential as the IC50 values against MRSA were 5.412 µM and 3.870 µM, whereas the CC50 values measured on HepG2 cells were 50.57 µM and 39.81 µM, respectively, resulting in selectivity indexes (SI) > 10. Compounds AT106 and AT116 were also selected for further study. IC50 values for these compounds were 5.439 µM and 3.178 µM, and the CC50 values were 60.33 µM and 50.87 µM, respectively; however, SI values > 10 were for MSSA only. Furthermore, none of the selected compounds showed significant hemolytic activity for human erythrocytes. We also tested the four compounds against S. aureus biofilms. Although AT116 and AT125 successfully disrupted MSSA biofilms, there was no measurable potency against MRSA biofilms. Checkerboard antibiotic assays to identify inhibitory mechanisms for these compounds indicated activity against bacterial cell membranes and cell walls, supporting the pharmaceutical potential for aurone-derived triazoles against antibiotic-resistant bacteria. Examining structure-activity relationships between the four compounds in this study and other aurone-derived triazoles in our library suggest that substitution with a halogen on either the salicyl ring or triazole aryl group along with triazoles having nitrile groups improves anti-Staphylococcal activity with the location of the functionality being very important.

Fever-like temperature impacts on Staphylococcus aureus and Pseudomonas aeruginosa interaction, physiology, and virulence both in vitro and in vivo

Background

Staphylococcus aureus and Pseudomonas aeruginosa cause a wide variety of bacterial infections and coinfections, showing a complex interaction that involves the production of different metabolites and metabolic changes. Temperature is a key factor for bacterial survival and virulence and within the host, bacteria could be exposed to an increment in temperature during fever development. We analyzed the previously unexplored effect of fever-like temperatures (39°C) on S. aureus USA300 and P. aeruginosa PAO1 microaerobic mono- and co-cultures compared with 37°C, by using RNAseq and physiological assays including in-vivo experiments.

Results

In general terms both temperature and co-culturing had a strong impact on both PA and SA with the exception of the temperature response of monocultured PA. We studied metabolic and virulence changes on both species. Altered metabolic features at 39°C included arginine biosynthesis and the periplasmic glucose oxidation in S. aureus and P. aeruginosa monocultures respectively. When PA co-cultures were exposed at 39°C they upregulated ethanol oxidation related genes along with an increment in organic acid accumulation. Regarding virulence factors, monocultured SA showed an increase in the mRNA expression of the agr operon and hld, pmsα and pmsβ genes at 39°C. Supported by mRNA data, we performed physiological experiments and detected and increment in hemolysis, staphylxantin production and a decrease in biofilm formation at 39°C. On the side of PA monocultures, we observed increase in extracellular lipase and protease and biofilm formation at 39°C along with a decrease in motility in correlation with changes observed at mRNA abundance. Additionally, we assessed host-pathogen interaction both in-vitro and in-vivo . S. aureus monocultured at 39°C showed a decrease in cellular invasion and an increase in IL-8 -but not in IL-6- production by A549 cell line. PA also decreased its cellular invasion when monocultured at 39°C and did not induce any change in IL-8 or IL-6 production. PA strongly increased cellular invasion when co-cultured at 37°C and 39°C. Finally, we observed increased lethality in mice intranasally inoculated with S. aureus monocultures pre-incubated at 39°C and even higher levels when inoculated with co-cultures. The bacterial burden for P. aeruginosa was higher in liver when the mice were infected with co-cultures previously incubated at 39°C comparing with 37°C.

Conclusion

Our results highlight a relevant change in the virulence of bacterial opportunistic pathogens exposed to fever-like temperatures in presence of competitors, opening new questions related to bacteria-bacteria and host-pathogen interactions and coevolution.

Chemical composition of Piper gaudichaudianum Kunth essential oil and evaluation of its antimicrobial and modulatory effects on antibiotic resistance, antibiofilm, and cell dimorphism inhibitory activities

Essential oils extracted from many plant species have different biological activities, among which microbial activity stands out. Species of the genus Piper have antimicrobial potential against different species of bacteria and fungi. In this sense, the present study aimed to determine the chemical composition of the essential oil from the leaves of Piper gaudichaudianum (EOPG), as well as to investigate their antimicrobial activity and their modulatory effect on the Norfloxacin resistance in the Staphylococcus aureus SA1199B strain overproducer of the NorA efflux pump. Furthermore, their inhibitory activities on the biofilm formation as well as on the cellular differentiation of C. albicans were evaluated. Gas chromatography analysis identified 24 compounds, such as hydrocarbon sesquiterpenes (54.8%) and oxygenated sesquiterpenes (28.5%). To investigate the antimicrobial potential of EOPG against S. aureus, E. coli, and C. albicans, a microdilution assay was performed, and no intrinsic antimicrobial activity was observed. On the other hand, the oil potentiated the activity of Norfloxacin against the SA1199B strain, indicating that EOPG could be used in association with Norfloxacin against S. aureus strains resistant to this antibiotic. EOPG also inhibited S. aureus biofilm formation, as evidenced by the crystal violet assay. In the dimorphism assay, EOPG was able to inhibit the cell differentiation process in C. albicans. Results indicate that EOPG could be used in association with Norfloxacin in the treatment of infections caused by resistant S. aureus strains overproducing the NorA efflux pump. Furthermore, its ability to inhibit the formation of hyphae by C. albicans suggests that EOPG could also be applied in the prevention and/or treatment of fungal infections.

Revisiting ESKAPE Pathogens: virulence, resistance, and combating strategies focusing on quorum sensing

The human-bacterial association is long-known and well-established in terms of both augmentations of human health and attenuation. However, the growing incidents of nosocomial infections caused by the ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter sp.) call for a much deeper understanding of these organisms. Adopting a holistic approach that includes the science of infection and the recent advancements in preventing and treating infections is imperative in designing novel intervention strategies against ESKAPE pathogens. In this regard, this review captures the ingenious strategies commissioned by these master players, which are teamed up against the defenses of the human team, that are equally, if not more, versatile and potent through an analogy. We have taken a basketball match as our analogy, dividing the human and bacterial species into two teams playing with the ball of health. Through this analogy, we make the concept of infectious biology more accessible.

Prodigiosin as an antibiofilm agent against multidrug-resistant Staphylococcus aureus

Staphylococcus aureus is known for forming bacterial biofilms that confer increased antimicrobial resistance. Combining antibiotics with antibiofilm agents is an alternative approach, but the antibiofilm ability of prodigiosin (PG), a potential antibiotic synergist, against antimicrobial-resistant (AMR) S. aureus remains to be understood. The antibiofilm activity of PG against 29 clinical AMR S. aureus strains was evaluated using crystal violet staining, and its synergistic effects with vancomycin (VAN) was confirmed using the checkerboard test. The viability and metabolic activity of biofilms and planktonic cells were also assessed. The results revealed that PG exhibited promising inhibitory activity against biofilm formation and synergistic activity with VAN. It effectively reduced the metabolic activity of biofilms and suppressed the production of exopolysaccharides, which might be attributed to the downregulation of biofilm-related genes such as sarA, agrA, and icaA. These findings suggest that PG could be used as a preventive coating or adjuvant against biofilms in clinical settings.

A genetic regulatory see-saw of biofilm and virulence in MRSA pathogenesis

Staphylococcus aureus is one of the most common opportunistic human pathogens causing several infectious diseases. Ever since the emergence of the first methicillin-resistant Staphylococcus aureus (MRSA) strain decades back, the organism has been a major cause of hospital-acquired infections (HA-MRSA). The spread of this pathogen across the community led to the emergence of a more virulent subtype of the strain, i.e., Community acquired Methicillin resistant Staphylococcus aureus (CA-MRSA). Hence, WHO has declared Staphylococcus aureus as a high-priority pathogen. MRSA pathogenesis is remarkable because of the ability of this "superbug" to form robust biofilm both in vivo and in vitro by the formation of polysaccharide intercellular adhesin (PIA), extracellular DNA (eDNA), wall teichoic acids (WTAs), and capsule (CP), which are major components that impart stability to a biofilm. On the other hand, secretion of a diverse array of virulence factors such as hemolysins, leukotoxins, enterotoxins, and Protein A regulated by agr and sae two-component systems (TCS) aids in combating host immune response. The up- and downregulation of adhesion genes involved in biofilm formation and genes responsible for synthesizing virulence factors during different stages of infection act as a genetic regulatory see-saw in the pathogenesis of MRSA. This review provides insight into the evolution and pathogenesis of MRSA infections with a focus on genetic regulation of biofilm formation and virulence factors secretion.

Biocompatible cationic polypeptoids with antibacterial selectivity depending on hydrophobic carbon chain length

The overuse of antibiotics has triggered a new infection crisis and natural antimicrobial peptides (AMPs) have been extensively studied as an alternative to fight microorganisms. Polypeptoids, or polypeptide-biomimetics, offer similar properties to polypeptides and a highly tunable structure that has been synthesized by various methods such as ring opening polymerization (ROP) using N-carboxyanhydride monomers. Simultaneous high antibacterial activity and biocompatibility of a structure by efficient synthesis is desired in the application of those materials. Herein, a series of cationic polypeptoids (PNBs) with variable side chain lengths was obtained by introducing positive charges to the main chain in one step and preserving the backbone structure, namely polypeptoids (PNBM, PNBE, PNBB) with different end groups (methyl (M), ethyl (E), butyl (B)). To address the issue of infection in interventional biomedical implants, we report cost-effective modified polyurethane (PU) films (PU-PNBM, PU-PNBE, PU-PNBB) as physical-biological synergistic antibacterial surfaces that overcome problems such as steric hindrance and the solubility of the materials. Antibacterial selectivity was achieved by regulating the different side chain lengths. When methyl and ethyl were used as hydrophobic side chains, they can only selectively kill Gram-positive Staphylococcus aureus. PNBB, the most hydrophobic and with a butyl side chain can kill both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus and inhibit the growth of bacterial biofilms. Effective in both solution and modified substrate, its biocompatibility is not compromised while the antibacterial properties are substantially improved. Furthermore, PU-PNBB films demonstrated their potential in vivo antimicrobial efficiency in a model of S. aureus infection established on mouse skin. The synthesis route and the surface modification strategies are convenient, providing a solution to the problem of poor biocompatibility in antimicrobial surface applications and a strategy for the use of peptide polymers for targeted therapy after specific infections in the biomedical field.

Pseudomonas aeruginosa's greenish-blue pigment pyocyanin: its production and biological activities

A subject of great interest is the bioprospecting of microorganisms and their bioactive byproducts, such as pigments. Microbial pigments have various benefits, including being safe to use due to their natural makeup, having therapeutic effects, and being produced all year round, regardless of the weather or location. Pseudomonas aeruginosa produces phenazine pigments that are crucial for interactions between Pseudomonas species and other living things. Pyocyanin pigment, which is synthesized by 90-95% of P. aeruginosa, has potent antibacterial, antioxidant, and anticancer properties. Herein, we will concentrate on the production and extraction of pyocyanin pigment and its biological use in different areas of biotechnology, engineering, and biology.

The degradation of chicken feathers by Ochrobactrum intermedium results in antioxidant and metal chelating hydrolysates and proteolytic enzymes for staphylococcal biofilm dispersion

The increase in the generation of chicken feathers, due to the large production of the poultry industry, has created the need to search for ecologically safer ways to manage these residues. As a sustainable alternative for recycling keratin waste, we investigated the ability of the bacterium Ochrobactrum intermedium to hydrolyze chicken feathers and the valorization of the resulting enzymes and protein hydrolysate. In submerged fermentation with three different inoculum sizes (2.5, 5.0, and 10.0 mg of bacterial cells per 50 mL of medium), the fastest degradation of feathers was achieved with 5.0 mg cells, in which a complete decomposition of the substrate (96 h) and earlier peaks of keratinolytic and caseinolytic activities were detected. In the resulting protein hydrolysate, we noticed antioxidant and Fe2+ and Cu2+ chelating activities. ABTS scavenging, Fe3+-reducing ability and metal chelating activities of the fermentative samples followed the same trend of feather degradation; as feather mass decreased in the media, these activities increased. Furthermore, we noticed about 47% and 60% dispersion of established 7-day biofilms formed by S. aureus after enzymatic treatment for 5 h and 24 h, respectively. These findings highlight the potential use of this bacterium as an environmentally friendly alternative to treat this poultry waste and offer valuable products.

Progress in the Prevalence, Classification and Drug Resistance Mechanisms of Methicillin-Resistant Staphylococcus aureus

Staphylococcus aureus is a common human pathogen with a variety of virulence factors, which can cause multiple infectious diseases. In recent decades, due to the constant evolution and the abuse of antibiotics, Staphylococcus aureus was becoming more resistant, the infection rate of MRSA remained high, and clinical treatment of MRSA became more difficult. The genetic diversity of MRSA was mainly represented by the continuous emergence of epidemic strains, resulting in the constant changes of epidemic clones. Different classes of MRSA resulted in different epidemics and resistance characteristics, which could affect the clinical symptoms and treatments. MRSA had also spread from traditional hospitals to community and livestock environments, and the new clones established a relationship between animals and humans, promoting further evolution of MRSA. Since the resistance mechanism of MRSA is very complex, it is important to clarify these resistance mechanisms at the molecular level for the treatment of infectious diseases. We firstly described the diversity of SCCmec elements, and discussed the types of SCCmec, its drug resistance mechanisms and expression regulations. Then, we described how the vanA operon makes Staphylococcus aureus resistant to vancomycin and its expression regulation. Finally, a brief introduction was given to the drug resistance mechanisms of biofilms and efflux pump systems. Analyzing the resistance mechanism of MRSA can help study new anti-infective drugs and alleviate the evolution of MRSA. At the end of the review, we summarized the treatment strategies for MRSA infection, including antibiotics, anti-biofilm agents and efflux pump inhibitors. To sum up, here we reviewed the epidemic characteristics of Staphylococcus aureus, summarized its classifications, drug resistance mechanisms of MRSA (SCCmec element, vanA operon, biofilm and active efflux pump system) and novel therapy strategies, so as to provide a theoretical basis for the treatment of MRSA infection.

Alterations in Antibiotic Susceptibility of Staphylococcus aureus and Klebsiella pneumoniae in Dual Species Biofilms

In the last decades, it has been shown that biofilm-associated infections in most cases are caused by rather two or even more pathogens than by single microorganisms. Due to intermicrobial interactions in mixed communities, bacteria change their gene expression profile, in turn leading to alterations in the biofilm structure and properties, as well as susceptibility to antimicrobials. Here, we report the alterations of antimicrobials efficiency in mixed biofilms of Staphylococcus aureus-Klebsiella pneumoniae in comparison with mono-species biofilms of each counterpart and discuss possible mechanisms of these alterations. In cell clumps detached from dual-species biofilms, S. aureus became insensitive to vancomycin, ampicillin, and ceftazidime compared to solely S. aureus cell clumps. In turn, the increased efficiency of amikacin and ciprofloxacin against both bacteria could be observed, compared to mono-species biofilms of each counterpart. Scanning electron microscopy and confocal microscopy indicate the porous structure of the dual-species biofilm, and differential fluorescent staining revealed an increased number of polysaccharides in the matrix, in turn leading to more loose structure and thus apparently providing increased permeability of the dual-species biofilm to antimicrobials. The qRT-PCR showed that ica operon in S. aureus became repressed in mixed communities, and polysaccharides are produced mainly by K. pneumoniae. While the molecular trigger of these changes remains undiscovered, detailed knowledge of the alterations in antibiotic susceptibility to given drugs opens doors for treatment correction options for S. aureus-K. pneumoniae biofilm-associated infections.