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

Ultra-small gold nanoparticle-coupled MOF-808 enabled sensitive detection of bacteria at neutral pH

Metal-organic framework (MOF)-based mimics are considered star materials to replace natural enzymes. However, their activity is generally limited to acidic conditions, which severely restricts their applications in biological systems where neutral pH is commonly required. Herein, a Zr(IV)-based MOF (MOF-808)/gold nanoparticle (AuNP) hybrid (called Hybrid-60) that shows superior peroxidase-like (POD-like) activity in both acidic and neutral media was prepared by in-situ growth of ultra-small AuNPs (UsAuNPs, ∼3.5 nm) on MOF-808. In comparison with the conventional AuNPs and MOF-808 nanozymes, Hybrid-60 demonstrated ∼8.04- and ∼6.74-time enhanced POD-like activities and superior high activity under neutral conditions, which broke the pH limitation. Furthermore, Hybrid-60 exhibited good tolerance to extreme pH value, concentrated salinity, and high-temperature environments. Taking Staphylococcus aureus (S. aureus) as a model analyte, we developed a simple immune sandwich assay using Hybrid-60 as colorimetric nanotags (ISAHC). A dual recognition strategy using anti-S. aureus antibody and concanavalin A-labeled Hybrid-60 was proposed to specifically capture and high-affinity label the target S. aureus. Then, leveraging the high POD-like activity of Hybrid-60, a simple and specific detection of S. aureus at nearly neutral pH was realized with a wide linear range (1 × 102-1 × 105 CFU/mL) and a low detection limit (32 CFU/mL). Moreover, the ISAHC method enabled one to detect the target S. aureus in human urine and serum with satisfactory recoveries from 93.8 % to 111.0 %, which indicates its clinical applicability. This study provides a new approach to develop neutral nanozymes and facilitate the point-of-care detection of bacteria.

Early fibrin biofilm development in cardiovascular infections

The single most common microbe causing cardiovascular infections is Staphylococcus aureus (S. aureus). S. aureus produces coagulase that converts fibrinogen to fibrin, which is incorporated into biofilms. This process aids in adherence to intravascular structures, defense against the host immune system, and resistance to antimicrobial treatment. Despite its significance, fibrin formation in S. aureus biofilms remains poorly understood. Therefore, this study aimed to elucidate the early development of cardiovascular biofilms. Clinically isolated coagulase-positive S. aureus and coagulase-negative Staphylococcus lugdunensis (S. lugdunensis) from patients with cardiovascular infections, and a coagulase mutant S. aureus Δcoa, were grown in tryptic soy broth (TSB), Iscove's Modified Dulbecco's Medium (IMDM), and pooled human plasma, with or without porcine heart valves. Bacterial growth, metabolic activity, and bacterial fibrinogen utilization were measured over 24 h at 37 °C. Time-lapse confocal microscopy was used to visualize and track biofilm development. S. aureus exhibited more growth in TSB and human plasma than S. lugdunensis and S. aureus Δcoa, but showed similar growth in IMDM after 24 h. Peak metabolic activity for all isolates was highest in TSB and lowest in human plasma. The presence of porcine valves caused strain-dependent alterations in time to peak metabolic activity. Confocal imaging revealed fibrin-based biofilm development exclusively in the coagulase-producing S. aureus strains. Between 2 and 6 h of biofilm development, 74.9 % (p = 0.034) of the fibrinogen from the medium was converted to fibrin. Variations in fibrin network porosity and density were observed among different coagulase-producing S. aureus strains. Fibrin formation is mediated by S. aureus coagulase and first strands occurred within 3 h for clinical strains after exposure to human plasma. This study stresses the importance of experimental design given the bacterial changes due to different media and substrates and provides insights into the early pathogenesis of S. aureus cardiovascular biofilms.

Toxicological assessment of citral and geraniol: Efflux pump inhibition in Staphylococcus aureus and invertebrate toxicity

This study aimed to evaluate the antibacterial activity against multi-drug-resistant strains carrying efflux pumps and assess their toxicity on Drosophila melanogaster and Aedes aegypti models. Microdilution tests in broth were performed to determine the Minimum Inhibitory Concentration (MIC). The efflux pump inhibition was evaluated by analyzing the reduction in antibiotic MIC and Ethidium Bromide (EtBr) MIC when combined with the products. Mortality assay and negative geotaxis were conducted on D. melanogaster specimens, and insecticidal activity assays were performed on A. aegypti larvae. Only geraniol reduced the antibiotic MIC when combined, reducing from 64 µg/mL to 16 µg/mL in the 1199B strain of S. aureus. When combined with EtBr, both geraniol and citral reduced EtBr MIC, with geraniol decreasing from 64 µg/mL to 16 µg/mL and citral decreasing from 64 µg/mL to 32 µg/mL. Regarding the S. aureus K2068 strain, geraniol reduced the antibiotic MIC from 16 µg/mL to 8 µg/mL, and citral reduced it from 16 µg/mL to 4 µg/mL. In combination with EtBr, all monoterpenes reduced MIC from 64 µg/mL to 32 µg/mL. Both products exhibited toxicity in D. melanogaster; however, citral showed higher toxicity with a precisely determined LC50 of 2.478 μL. As for the insecticidal action on A. aegypti, both products demonstrated toxicity with cumulative effects and dose-dependent mortality.

Antimicrobial and antibiofilm activity of prepared thymol@UIO-66 and thymol/ZnONPs@UIO-66 nanoparticles against Methicillin-resistant Staphylococcus aureus: A synergistic approach

This study introduces a novel approach to enhance the antibacterial properties of UIO-66 by incorporating both Thymol and ZnO nanoparticles within its framework which represents a significant advancement like exhibiting a synergistic antibacterial effect, providing a prolonged and controlled release, and mitigating cytotoxicity associated with the release of free ZnO nanoparticles by combining these two antimicrobial agents within a single, well-defined metal-organic framework. UIO-66 frameworks are investigated as carriers for the natural antimicrobial agent, Thymol, and ZnONPs offering a novel drug delivery system for antibacterial applications. Results demonstrated 132, 90, 184, and 223 nm sizes for UIO-66, ZnONPs, UIO-66 encapsulated Thymol, and UIO-66 encapsulated both Thymol and ZnONPs, respectively. Successful encapsulation of the antibacterial drug with a high entrapment efficiency of 64 % for Thymol was approved, and 49 % in-vitro release of Thymol was achieved for 72 hours. In-vitro antibacterial assays revealed promising results, with the drug-loaded nanoparticles exhibiting significantly lower MIC values and enhanced bactericidal activity against S. Aureus bacterial strains compared to the free drug, as demonstrated by agar disk diffusion and time-kill assays. MIC values reduced from a range of 31.25-250 µg/ml for free Thymol and 12.5-100 µg/ml for free ZnONPs to 3.9-62.5 µg/ml for Thymol@UIO-66 and 1.95-15.63 µg/ml for Thymol/ZnONPs@UIO-66. According to the results, the mixture of both Thymol and ZnONPs had 41 % and 16 % more antibiofilm activities in comparison with free Thymol and free ZnONPs, respectively. Furthermore, Thymol@UIO-66 had 25 % higher antibiofilm activities relative to not-encapsulated Thymol and ZnONPs, and this improvement was even 46 % more in Thymol/ZnONPs@UIO-66 in comparison with Thymol@UIO-66. Overall, this study demonstrates the potential of Thymol/ZnONPs@UIO-66 frameworks as a promising drug delivery platform for effective antibacterial therapy. This approach to overcome antibiotic resistance and improve treatment efficacy potentially.

Community-acquired methicillin-resistant Staphylococcus aureus : is it still a significant pathogen for skin and soft tissue infections? A 30-year overview

PURPOSE OF REVIEW

The prevalence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) in skin and soft tissue infections (SSTI) has significantly changed in recent decades. We conducted a literature review to determine whether this microorganism, which became increasingly common as a cause of SSTI in the 2000s, still plays a significant role in these infections today.

RECENT FINDINGS

Over the past 30 years, there has been a pattern of increase and then decrease in these infections. The highest frequency was observed in the United States, to the extent that guidelines recommended empirical antibiotic treatment for this pathogen in SSTI. Clone USA300 is the primary causative agent in the United States. In Europe, SSTI are much less common than in the United States, and the presence of this clone has been significantly lower. A decrease in the frequency of SSTI and CA-MRSA has been observed in developed countries. However, the spread of specific clones in Latin America, Asia and Africa highlights the need for rigorous global surveillance.

SUMMARY

In recent years, the prevalence of CA-MRSA SSTI has decreased in developed countries. However, globalisation, immigration and intercontinental travel have favoured the spread of some clones with epidemic potential. It remains to be seen whether the current lower frequency will be maintained or whether these clones will give rise to a new wave.

Evaluation of the safety and probiotic properties of Limosilactobacillus fermentum BGI-AF16, a uric acid-lowering probiotic strain

Some beneficial microorganisms in the intestine have the potential to degrade uric acid, offering a novel strategy for the prevention of hyperuricemia. In this study, the safety and probiotic potentials of Limosilactobacillus fermentum BGI-AF16 were evaluated by whole genome sequence analysis and in vitro experiments. Based on the gene analysis of antibiotic resistance and virulence factors, L. fermentum BGI-AF16 has been shown to be safe. We identified probiotic-related genes by genome annotation tools and conducted in vitro experiments to evaluate the ability of L. fermentum BGI-AF16 to inhibit pathogenic bacteria, tolerate a simulated gastrointestinal environment, and degrade uric acid. The results from in vitro experiments showed that L. fermentum BGI-AF16 had inhibitory effects on four clinically relevant pathogens and was highly tolerant to the gastrointestinal environment. In addition, L. fermentum BGI-AF16 was able to rapidly degrade uric acid within the first hour, and the strain could degrade 56.36 ± 2.32 % of uric acid by the third hour. The genome of the strain contains genes encoding flavin adenine dinucleotide (FAD)-dependent urate hydroxylase (EC.1.14.13.113), an enzyme that directly metabolizes uric acid. And the strain has a complete uric acid metabolic pathway. These results suggest that L. fermentum BGI-AF16 is a probiotic candidate with significant potential for reducing uric acid level.

Advancements in synthetic methodologies and biological applications of lawsone derivatives

2-Hydroxy-1,4-naphthoquinone, widely recognized as lawsone, is a natural dye obtained from the henna plant (Lawsonia inermis), known for its biological activity and diverse applications in biochemistry and analytical chemistry. As a versatile precursor, it plays a crucial role in synthesizing a wide range of structurally diverse and bioactive molecular scaffolds. This review highlights recent progress in the development of lawsone derivatives, emphasizing their extensive biological activities, such as anticancer, antimicrobial, antioxidant, antimalarial, and metabolic enzyme-targeting activities, as well as their structure-activity relationships. Remarkably, this is the first detailed exploration covering both the biological activities and chemical synthesis of significant lawsone derivatives from 2016 to the present.

Integrated spectroscopic and MD simulation approach to decipher the effect of pH on the structure function of Staphylococcus aureus thymidine kinase

Staphylococcus aureus is a major human pathogen responsible for a variety of clinical infections, becoming increasingly resistant to antibiotics. To address this challenge, there is a need to identify new cellular targets and innovative approaches to expand treatment options. One such target is thymidine kinase (TK), a crucial enzyme in the pyrimidine salvage pathway, which plays a key role in the phosphorylation of thymidine, an essential component in DNA synthesis and repair. In this study, we have successfully cloned, expressed, and purified the TK protein. A comprehensive investigation into how different pH levels affect the structure and functional activity of TK, using a combination of spectroscopy, classical molecular dynamics simulations, and enzyme activity assays was conducted. Our study revealed that variation in pH disrupts secondary and tertiary structures of TK with noticeable aggregate formation at pH 5.0. Enzyme activity studies demonstrated that TK exhibited its maximum kinase activity within the physiological pH range. These findings strongly suggest a connection between structural changes and enzymatic activity, which was further supported by the agreement between the spectroscopic features we measured and the results of our MD simulations. Our study provides a deeper insight into the structural features of TK, which could potentially be harnessed for the development of therapeutic strategies aimed at combatting infectious diseases. Conformational dynamics plays an essential role in the design and development of effective inhibitors. Considering the effects of pH on the conformational dynamics of TK, our findings may be implicated in the development of potent and selective inhibitors.Communicated by Ramaswamy H. Sarma.

NLRP3 inflammasome in health and disease (Review)

Activation of inflammasomes is the activation of inflammation‑related caspase mediated by the assembly signal of multi‑protein complex and the maturity of inflammatory factors, such as IL‑1β and IL‑18. Among them, the Nod‑like receptor family pyrin domain containing 3 (NLRP3) inflammasome is the most thoroughly studied type of inflammatory corpuscle at present, which is involved in the occurrence and development of numerous human diseases. Therefore, targeting the NLRP3 inflammasome has become the focus of drug development for related diseases. In this paper, the research progress of the NLRP3 inflammasome in recent years is summarized, including the activation and regulation of NLRP3 and its association with diseases. A deep understanding of the regulatory mechanism of NLRP3 will be helpful to the discovery of new drug targets and the development of therapeutic drugs.

Design of Natterins-based peptides improves antimicrobial and antiviral activities

The biochemical analysis of animal venoms has been intensifying over the years, enabling the prediction of new molecules derived from toxins, harnessing the therapeutic potential of these molecules. From the venom of the fish Thalassophryne nattereri, using in silico methods for predicting antimicrobial and cell-penetrating peptides, two peptides from Natterins with promising characteristics were synthesized and subjected to in vitro and in vivo analysis. The peptides were subjected to stability tests and antimicrobial assays, cytotoxicity in murine fibroblast cells, antiviral assays against the Chikungunya virus, and the toxicity on G. mellonella was also evaluated. The findings underscore the peptides' robust stability under varying temperatures and pH conditions and resistance to proteolytic degradation. The peptides demonstrated significant antimicrobial efficacy, minimal cytotoxicity, and low hemolytic activity. Although their antiviral efficacy was limited, they showed potential at specific stages of viral replication. The in vivo toxicity tests indicated a favorable safety profile. These findings suggest that this approach can aid in the development of antimicrobial agents, offering a faster and personalized method to combat microbial infections, and represent a promising discovery in venom biotechnology research.

Novel antimicrobial strategies for diabetic foot infections: addressing challenges and resistance

AIMS

This review examines the challenges posed by Diabetic Foot Infections (DFIs), focusing on the impact of neuropathy, peripheral arterial disease, immunopathy, and the polymicrobial nature of these infections. The aim is to explore the factors contributing to antimicrobial resistance and assess the potential of novel antimicrobial treatments and drug delivery systems in improving patient outcomes.

METHOD

A comprehensive analysis of existing literature on DFIs was conducted, highlighting the multifactorial pathogenesis and polymicrobial composition of these infections. The review delves into the rise of antimicrobial resistance due to the overuse of antimicrobials, biofilm formation, and microbial genetic adaptability. Additionally, it considers glycemic control, patient adherence, and recurrence rates as contributing factors to treatment failure. Emerging therapies, including new antimicrobial classes and innovative drug delivery systems, were evaluated for their potential efficacy.

RESULTS

DFIs present unique treatment challenges, with high rates of antimicrobial resistance and poor response to standard therapies. Biofilm formation and the genetic adaptability of pathogens worsen resistance, complicating treatment. Current antimicrobial therapies are further hindered by poor glycemic control and patient adherence, leading to recurrent infections. Novel antimicrobial classes and innovative delivery systems show promise in addressing these challenges by offering more targeted, effective treatments. These new approaches aim to reduce resistance and improve treatment outcomes.

CONCLUSION

DFIs remain a clinical challenge due to their multifactorial nature and antimicrobial resistance. The development of novel antimicrobials and drug delivery systems is crucial to improving patient outcomes and combating resistance. Future research should focus on enhancing treatment efficacy, reducing resistance, and addressing patient adherence to reduce the burden of DFIs.

Wall teichoic acid glycosylation of bovine-associated Staphylococcus aureus strains

Staphylococcus aureus (S. aureus) is one of the major causes of bovine mastitis, a disease with detrimental effects on health and wellbeing. Current control measures are costly, laborious and not always effective in eradicating S. aureus. The cell wall-linked polysaccharide wall teichoic acid (WTA) is highly immunogenic in humans and is considered as a prospective vaccine antigen based on promising pre-clinical studies in animals. WTA consist of polymerized ribitol-phosphate backbone that is modified with N-acetylglucosamine (GlcNAc) moieties in different configurations by the glycosyltransferases TarS (β-1,4-GlcNAc), TarM (α-1,4-GlcNAc) and TarP (β-1,3-GlcNAc). This study aimed to characterize the presence and genetic variation in tarS, tarM and tarP in bovine-associated S. aureus strains and how this impacts WTA-glycoprofile. Bioinformatic analyses of a whole genome sequence database consisting of 1047 S. aureus, 10 S. schweitzeri, and 6 S. argenteus strains showed that over 99% of strains contained tarS, 34 % also contained tarM, while 5 % of the strains encoded tarP in addition to tarS. The distribution of WTA-glycosyltransferase genes was similar to what has been reported for human-associated S. aureus strains. Phenotypic analysis of WTA glycosylation by flow cytometry corroborated with tarS/tarM/tarP gene presence. The WTA glycoprofile was variable between bovine-associated strains and the levels and ratios of GlcNAcylation were affected by growth conditions. Interestingly, a divergent tarM allele was present in strains of clonal complexes (CC) 49 and the mastitis-associated CC151, but its function was similar to canonical tarM. In conclusion, we demonstrated that bovine-associated S. aureus strains show similar variation in WTA GlcNAc decoration as human S. aureus strains, despite the presence of a divergent tarM allele.

Recreational Facilities as Reservoirs for Multidrug-Resistant Staphylococcus aureus

Antibiotic-resistant pathogens in public settings present a growing risk to human health. Staphylococcus aureus often asymptomatically colonizes human skin, while virulent strains cause soft tissue infections, osteomyelitis, endocarditis, and are associated with cystic fibrosis. Here we investigated the presence and distribution of multidrug-resistant S. aureus on exercise equipment in university recreation facilities. Equipment sampled included barbells (n = 10), dumbbell handles (n = 15), kettle bell handles (n = 5), ellipticals (n = 5), treadmills (n = 5), cable attachments (n = 5). Mannitol salt agar, CHROMagar-MRSA, Gram staining and latex agglutination testing were useds to isolate and identify S. aureus, including methicillin-resistant S. aureus. Kirby-Bauer disc-diffusion assay was utilized to determine antibiotic susceptibility profiles. Results show 42% of 456 S. aureus isolates from 45 different equipment surfaces were ampicillin resistant. Of 60 representative ampicillin-resistant isolates, 92% were resistant to additional antibiotics with the majority resistant to erythromycin (40%) and sulfisoxazole (75%). Multidrug resistance to three or more drugs was observed in 73% of the ampicillin-resistant subpopulation. These results indicate recreational facilities may serve as reservoirs for multi-drug resistant S. aureus including methicillin-resistant S. aureus (MRSA) and regular disinfection of equipment is warranted for safeguarding public health.

MurG as a potential target of quercetin in Staphylococcus aureus supported by evidence from subtractive proteomics and molecular dynamics

The rise of methicillin-resistant Staphylococcus aureus (MRSA) as a major public health threat underscores a critical need for new antibacterial strategies. Quercetin is a naturally occurring flavonoid with a range of bioactivities, including antibacterial activity against S. aureus. However, how quercetin inhibits S. aureus and binds to its potential molecular target is not well understood. Understanding the interaction of quercetin with potential bacterial targets may provide crucial insights for developing modified derivatives with better drug-like properties. To investigate potential targets of quercetin in S. aureus, we employed a targeted subtractive proteomics approach, which identified the glycosyltransferase MurG as a novel quercetin target. Through rigorous molecular docking and extensive 250 ns molecular dynamics simulations, quercetin was shown to bind stably to MurG, suggesting a mechanism that interferes with the critical peptidoglycan biosynthesis pathway. Molecular Mechanics Generalized Born Surface Area (MM-GBSA) analyses provided quantitative evidence of the complex's stability, indicating a strong and stable interaction with potential therapeutic implications. Principal Component Analysis (PCA) further validated the reduction in MurG's structural flexibility upon quercetin binding, reinforcing the hypothesis that this interaction could effectively inhibit its biological function. The identification of its interaction with MurG provides a foundation for the development of novel, more effective antibacterial agents. This strategy, facilitated by subtractive proteomics, could also be adapted to target other resistant pathogens, demonstrating broad applicability in the fight against antibiotic resistance.

Mechanistic insights into the multitarget synergistic efficacy of farrerol and β-lactam antibiotics in combating methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA), a principal causative agent of infections worldwide, urgently requires innovative interventions to counter its increasing risk. The present study revealed the profound impact of farrerol (FA), a robust bioactive agent, on the virulence and resistance mechanisms of MRSA. Our in-depth investigation revealed that FA significantly mitigated the β-lactam resistance of MRSA USA300, an achievement attributed to its precise interference with the BlaZ and Pbp2a protein. Additionally, FA indirectly diminishes the oligomerization of PBP2a by disrupting pigment synthesis, further contributing to its efficacy. In addition, FA extends its functional footprint beyond resistance modulation, exhibiting substantial antivirulence efficacy through selective inhibition of the accessory gene regulator (Agr) system, thereby significantly curbing MRSA pathogenicity in A549 cell and murine models. This study comprehensively explored the multiple impacts of FA on MRSA, shedding light on its versatile role as a BlaZ suppressor, pigment synthesis regulator, and AgrA activity modulator. These intricate findings firmly position FA as a compelling therapeutic candidate for addressing MRSA infections in the clinic.

Endophytic bacteria of Gracilaria edulis in combating human bacterial pathogens by PPDHMP - A crude to single molecule product development approach

Resistance in human bacterial pathogens and lack of novel antibiotic development has led to the need for new antibiotics. Therefore, the current study was focused on endophytic bacteria from Gracilaria edulis, an edible seaweed, capable of synthesizing novel bioactive compounds with potential applications in the inhibition of human pathogens. The endophyte, identified as Bacillus subtilis through 16S rRNA gene sequencing, exhibited significant antibacterial activity against bacterial human pathogens. Using GC-MS, FTIR and NMR the lead compound was identified as Pyrrolo[1,2-α] pyrazine-1,4-dione, hexahydro-3-(2-methylpropyl) (PPDHMP). Optimized media using glucose, proline, and valine significantly enhanced the production of PPDHMP which was observed by the increase in zone of inhibition. Molecular docking of PPDHMP indicated a high binding affinity to beta-lactamase, suggesting its potential as a beta-lactamase inhibitor. PPDHMP exhibited cell wall inhibitory activity and ADMET analysis revealed promising pharmacokinetic and toxicity profiles indicating its potential for further evaluation as an oral antibiotic candidate. Phytotoxicity assessments and hemolytic assay confirmed the non-toxic nature of the metabolites produced. This research highlights the immense potential of marine endophytes in addressing the escalating issue of antibiotic resistance and paves the way for innovative solutions in antimicrobial therapy.

Analysis of co-occurrence of type II toxin-antitoxin systems and antibiotic resistance determinants in Staphylococcus aureus

Toxin-antitoxin (TA) systems consist of toxic proteins and their inhibitors, and were originally shown to ensure plasmid maintenance in bacterial populations. Over time, however, TA systems have also been identified on bacterial chromosomes, raising questions about their roles unrelated to plasmid stability. Among the eight currently recognized types of TA systems, type II has been the most extensively investigated. Type II systems are often found in pathogenic bacterial species, including staphylococci. Staphylococcus aureus, a notorious human pathogen, harbors multiple type II TA systems, both plasmid- and chromosome-encoded, while their potential relation to virulence remains to be addressed. Here, we investigate the co-occurrence of TA systems and antibiotic resistance (AR) determinants in S. aureus, focusing on the potential negative impact of type II toxin RNases on antibiotic resistance. We considered both well-characterized and newly characterized TA loci of S. aureus. Our findings demonstrate a relationship between TA systems and AR determinants, wherein TA systems negatively affect antibiotic resistance. Due to substantial selective pressure, the migration of TA systems from plasmids to chromosomes results in their inactivation. This observation may be an important factor shaping the spread and evolution of both TA systems and AR determinants in bacteria. We exemplify this phenomenon in detail using the well-known PemIK-Sa1 system and a newly identified SCCmec-related PemIK-Sa6 system characterized in this study.

IMPORTANCE

Toxin-antitoxin (TA) systems are entities unique to bacteria. They are involved in the maintenance of mobile genetic elements (MGEs), regulation of gene expression and bacterial virulence. Staphylococcus aureus is a dangerous human pathogen with increasing antibiotic resistance (AR). The maintenance and dissemination of AR determinants is often driven by MGEs, which link AR and TA systems. Our study identified a negative correlation between TA systems and AR determinants in S. aureus. Furthermore, we have shown that the expression of a toxic component of an exemplary TA system negatively affects antibiotic resistance. We argue that in particular strains, a selective pressure maintains either the TA system or AR determinant. Alternatively, TA systems are inactivated by mutations when present together with AR determinants to maintain the functionality of the latter. Our observations uncover an important factor shaping the spread and evolution of both TA systems and AR determinants in bacteria, which is especially relevant to pathogenic species.

An mRNA Display Approach for Covalent Targeting of a Staphylococcus aureus Virulence Factor

Staphylococcus aureus (S. aureus) is an opportunistic human pathogen that causes over one million deaths around the world each year. We recently identified a family of serine hydrolases termed fluorophosphonate binding hydrolases (Fphs) that play important roles in lipid metabolism and colonization of a host. Because many of these enzymes are only expressed in Staphylococcus bacteria, they are valuable targets for diagnostics and therapeutics. Here, we developed and screened highly diverse cyclic peptide libraries using mRNA display with a genetically encoded oxadiazolone (Ox) electrophile that was previously shown to potently and covalently inhibit multiple Fph enzymes. By performing multiple rounds of counter selections with WT and catalytic dead FphB, we were able to tune the selectivity of the resulting selected cyclic peptides containing the Ox residue toward the active site serine. From our mRNA display hits, we developed potent and selective fluorescent probes that label the active site of FphB at single digit nanomolar concentrations in live S. aureus bacteria. Taken together, this work demonstrates the potential of using direct genetically encoded electrophiles for mRNA display of covalent binding ligands and identifies potent new probes for FphB that have the potential to be used for diagnostic and therapeutic applications.

Evaluation of aminoglycoside- and methicillin-resistant Staphylococcus aureus: phenotypic and genotypic insights from clinical specimens in Ardabil, Iran

BACKGROUND

Combination therapy including an aminoglycoside antibiotic and a cell-wall active agent is considered the most suitable option to treat invasive infections with methicillin-resistant Staphylococcus aureus (MRSA). Dual drug therapy enhances the effectiveness of treatment and reduces the risk of resistance development. This study aims to elucidate the phenotypic and molecular resistance to aminoglycosides and methicillin, and the molecular epidemiologic characteristics of S. aureus in Ardabil northwest Iran.

METHODS

Totally, 118 S. aureus isolates collected from clinical specimens were investigated. Identification was performed using standard microbiological and molecular approaches. Aminoglycoside and methicillin resistance were evaluated using the disk diffusion assay, and the minimum inhibitory concentrations (MICs) of aminoglycosides were determined via the agar dilution method. The mecA gene encoding methicillin resistance and aminoglycoside modifying enzymes (AMEs) genes were detected using PCR. Molecular epidemiologic features of the isolates were determined using staphylococcal cassette chromosome mec (SCCmec) typing spa typing and ERIC-PCR assays.

RESULTS

Of the isolates, 42.4% (n = 50) and 57.6% (n = 68) were identified as MRSA and MSSA, respectively. All MRSA isolates were mecA-positive. Among MRSA isolates, SCCmec type IVa (17; 34%) was predominant, followed by types IVc, V, III, II, and I. Resistance rates to gentamicin, kanamycin, tobramycin, and amikacin were 16.1%, 17.8%, 8.5%, and 8.5%, respectively. Overall, the aminoglycoside resistance and most non-aminoglycoside antibiotics were significantly higher in MRSA versus MSSA isolates. The prevalence of AME genes was as follows: aac(6')-Ie-aph(2'') (30; 76.9%), aph(2'')-Ib (22; 56.4%), and ant(4')-Ia (14; 35.9%). About 60% of aminoglycoside-resistant isolates harbored ≥ 2 AME genes. The t030 type was the most common spa type identified. The ERIC-PCR profiles categorized the isolates into 19 unique ERIC types.

CONCLUSIONS

This study reveals high aminoglycoside and methicillin resistance in S. aureus isolates from Ardabil hospitals. Predominant SCCmec type IVa and spa type t030 indicate specific molecular patterns. These findings highlight the need for continuous surveillance and targeted treatment strategies for MRSA infections.

CLINICAL TRIAL NUMBER

Not applicable.

Evaluating infection risk associated with Staphylococcus aureus nasal carriage in blood donors: a prospective multicentre study in Denmark

OBJECTIVE

To investigate whether Staphylococcus aureus nasal carriage influences susceptibility to community-acquired S. aureus-associated infection and any other bacterial infection risk in healthy individuals.

METHODS

This prospective cohort study included blood donors aged 18-70 years between 2014-2021 in Denmark. A nasal swab cultivated for S. aureus defined carriage type (exposure) and infection endpoints were redeemed antibacterial prescriptions or ICD-10 diagnoses from national registers. Adjusted incidence rate ratio (IRR) was estimated using Poisson regression for prescriptions while Cox regression estimated hazard ratio for diagnoses.

RESULTS

Of 8,738 included participants, 3,503 (40.5%) were carriers. During a median follow-up of 3.8 years (IQR: 2.4-5.1), 1,110 participants redeemed dicloxacillin/flucloxacillin and 1,412 redeemed topical fusidic acid prescriptions while 378 participants received hospital treatment for infections during 3.4 years (IQR: 1.9-4.6). Nasal carriers redeemed dicloxacillin and topical fusidic acid prescriptions more often than non-carriers (IRR 1.40 [95% CI: 1.24-1.58] and IRR 1.22 [1.10-1.36], respectively). Participants who redeemed one dicloxacillin prescription were six times more likely to redeem another within two years. Among these, carriers had a higher incidence of redeeming additional dicloxacillin prescriptions than non-carriers (absolute risk, 19.0% vs 12.9%, respectively; IRR 1.46 [1.17-1.84]). S. aureus nasal carriage was not associated with higher risk of redeeming other antibacterial prescriptions nor with risk of hospital-treated S. aureus and any other bacterial infections.

CONCLUSION

In this study comprising healthy adults, nasal carriers with S. aureus exhibited an increased risk of redeemed dicloxacillin and topical fusidic acid prescriptions, but nasal carriage was not associated with any other types of bacterial infection. Findings suggest that nasal carriage elevates the burden of community-acquired S. aureus infections.

Computational insights into the inhibition of cell division in Staphylococcus aureus: Towards novel therapeutics

Staphylococcus aureus, a gram-positive bacterium, causes infective endocarditis, osteoarticular, skin, and respiratory infections. The emergence of multidrug-resistant strains, particularly Methicillin-resistant Staphylococcus aureus (MRSA), has caused a 21-35 % rise in bloodstream infections, complicating treatment strategies. Filamentous temperature-sensitive protein Z (FtsZ), a critical protein involved in bacterial cell division, forms a Z-ring at the division site, making it a key target for novel antibacterial therapies. In this study, 1165 phytochemicals were screened, and three lead molecules namely, Aromadendrin, Leucopelargonidin, and 7-Deacetoxy-7-oxogedunin were identified based on their favorable physicochemical properties, drug-likeness, and estimated binding affinities (- 11.73 kcal/mol, - 10.77 kcal/mol, and - 10.38 kcal/mol, respectively) against FtsZ. 100 ns Molecular dynamics simulations conducted in triplicates confirmed the stability of the FtsZ-ligand complexes.Binding free energy calculations revealed that IMPHY003535 (Leucopelargonidin) exhibited the most favorable binding free energy (-27.25 kcal/mol), followed by 7-Deacetoxy-7-oxogedunin (-15.31 kcal/mol) and Aromadendrin (-13.38 kcal/mol). Leucopelargonidin emerged as the most promising inhibitor, highlighting its potential as a lead compound for developing antibacterial agents targeting FtsZ. These findings demonstrate the significant role of phytochemicals in combating antibiotic resistance and the importance of further optimization, including in vivo studies, to assess their therapeutic potential, which could provide new treatment avenues to overcome bacterial resistance mechanisms.

A silent opponent: Staphylococcus aureus and its impact on wrestlers

Community acquired methicillin resistant Staphylococcus aureus infections have surged dramatically over the past decade. Athletes in contact sports, especially wrestlers, represent a unique subset of young, healthy individuals who are at heightened risk for transmitting methicillin resistant Staphylococcus aureus. The sport of wrestling has seen a significant increase in participation, particularly among adolescents, underscoring its growing popularity and the urgent need to address this issue. Unfortunately, the rates of community acquired methicillin resistant Staphylococcus aureus have followed a similar upward trend. Treatment options for community acquired methicillin resistant Staphylococcus aureus vary, ranging from topical or systemic antibiotics to more invasive interventions like incision, drainage, and intralesional injections. Preventive measures are also essential and include avoiding shared equipment, meticulous mat and gear cleaning, and eliminating bacterial colonization. While existing research supports the effectiveness of decolonization strategies in hospital settings, there is a pressing need to adapt and implement these approaches within the wrestling community. Current prevention methods, such as mat cleaning and skin checks before competitions, are insufficient on their own. By adopting more comprehensive decolonization protocols tailored to the wrestling environment, we can better protect athletes and reduce the incidence of community acquired methicillin resistant Staphylococcus aureus skin infections.

Machine learning-based prediction model for patients with recurrent Staphylococcus aureus bacteremia

BACKGROUND

Staphylococcus aureus bacteremia (SAB) remains a significant contributor to both community-acquired and healthcare-associated bloodstream infections. SAB exhibits a high recurrence rate and mortality rate, leading to numerous clinical treatment challenges. Particularly, since the outbreak of COVID-19, there has been a gradual increase in SAB patients, with a growing proportion of (Methicillin-resistant Staphylococcus aureus) MRSA infections. Therefore, we have constructed and validated a pediction model for recurrent SAB using machine learning. This model aids physicians in promptly assessing the condition and intervening proactively.

METHODS

The patients data is sourced from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database version 2.2. The patients were divided into training and testing datasets using a 7:3 random sampling ratio. The process of feature selection employed two methods: Recursive Feature Elimination (RFE) and Least Absolute Shrinkage and Selection Operator (LASSO). Prediction models were built using Extreme Gradient Boosting (XGBoost), Random Forest (RF), Logistic Regression (LR), Support Vector Machine (SVM), and Artificial Neural Network (ANN). Model validation included Receiver Operating Characteristic (ROC) analysis, Decision Curve Analysis (DCA), and Precision-Recall Curve (PRC). We utilized SHAP (SHapley Additive exPlanations) values to demonstrate the significance of each feature and explain the XGBoost model.

RESULTS

After screening, MRSA, PTT, RBC, RDW, Neutrophils_abs, Sodium, Calcium, Vancomycin concentration, MCHC, MCV, and Prognostic Nutritional Index(PNI) were selected as features for constructing the model. Through combined evaluation using ROC、 DCA and PRC, XGBoost demonstrated the best predictive performance, achieving an AUC value of 0.76 (95% CI: 0.66-0.85) in ROC and 0.56 (95% CI: 0.37-0.75) in PRC. Building a website based on the Xgboost model. SHAP illustrated the feature importance ranking in the XGBoost model and provided examples to explain the XGBoost model.

CONCLUSIONS

The adoption of XGBoost for model development holds widespread acceptance in the medical domain. The prediction model for recurrent SAB, developed by our team, aids physicians in timely diagnosis and treatment of patients.

Staphylococcal SplA and SplB serine proteases target ubiquitin(-like) specific proteases

Staphylococcus aureus is a Gram-positive opportunistic pathogen that has colonized nearly 30% of the human population and can cause life-threatening infections. S. aureus exports a variety of virulence factors, such as a novel set of extracellular serine protease-like proteins (Spls). Spls are expressed by most clinical isolates of S. aureus, but their pathophysiological substrates and role during the infection are largely unknown. Here we characterized the substrate and cleavage specificity of recombinantly expressed SplA and SplB proteins. We identified a group of ubiquitin or ubiquitin-like modifying enzymes including deubiquitinating enzymes from human as well as from bacterial sources to be so far unknown SplA and SplB substrates. Distinct cleavage sites within these substrates for SplA (YLY↓T, FMY↓N) and SplB (VCD↓S) were identified by mass spectrometry and confirmed by site-directed mutagenesis of the target proteins. Since many cellular immune signaling pathways are tightly regulated by ubiquitination, the specific cleavage of ubiquitin modifying enzymes strongly suggests a specific role of Spls in manipulating immune signaling and in competing with other bacteria.

Non-Membrane Active Peptide Resensitizes MRSA to β-Lactam Antibiotics and Inhibits S. aureus Virulence

Methicillin-resistant Staphylococcus aureus (MRSA) is a serious global health threat due to its high morbidity and mortality rates, creating a dire need for novel therapeutic strategies. Antimicrobial peptides (AMPs), with broad-spectrum activity and low propensity for resistance development, show promise as effective antibiotic adjuvants to reverse multidrug-resistance in bacteria. Herein, it is uncovered that a potent and non-toxic AMP termed GN1 substantially resensitizes MRSA to multiple β-lactam antibiotics at low concentrations. Mechanistic studies indicate that GN1 functions by suppressing both the production and enzymatic activity of MRSA-associated resistance determinants, including penicillin-binding protein 2a (PBP2a) and β-lactamase. Additionally, GN1 exhibits a robust anti-virulence profile by inhibiting MRSA biofilm formation and staphyloxanthin production. Furthermore, GN1 induces bacterial metabolic perturbation, resulting in glutamate accumulation and oxidative damage. Importantly, the combination of GN1 with β-lactam antibiotics effectively mitigates MRSA-induced infections in the animal infection models. Collectively, these findings suggest that GN1 represents a potent β-lactam adjuvant and anti-virulence agent, offering a safe and versatile solution to combat MRSA infections.

Efficacy of Staphylococcus aureus nasal decolonization at hospital admission on reduction of any infections within 90 days - a systematic review and meta-analysis

BACKGROUND

Infections with Staphylococcus aureus (S. aureus) are associated with excess mortality and costs. Simple interventions, such as decolonization protocols, might help to reduce subsequent infections, especially in settings in which S. aureus is of major clinical relevance, such as healthcare-associated infections.

AIM

To determine if S. aureus decolonization protocols, using a nasal ointment and applied at hospital admission, reduce the risk of infection.

SEARCH METHODS

MEDLINE, EMBASE and clinicaltrials.gov were searched for all randomized controlled trials investigating the use of nasal ointments for decolonization for patients at hospital admission and reporting on infections within 90 days. Data were pooled as risk ratios using a random-effects model. The Cochrane RoB 2 tool and GRADE were used to assess the risk of bias and quality of evidence.

RESULTS

Four (0.5%) of 833 screened studies with a total of 4,150 patients met eligibility criteria. The overall certainty of evidence ranged from low to moderate across outcomes. Nasal S. aureus decolonization likely reduces infections (6.9% vs. 9.5%; rate ratio (RR): 0.73 (95%CI 0.57; 0.93)) and may increase microbiological eradication (82.7% vs. 55.2%; RR: 1.80 (95%CI 0.73; 4.44) compared to placebo. It may not reduce mortality (2.5 vs. 2.4; RR: 1.02 (95%CI 0.67; 1.54) but also not lead to increased adverse effects (0.7% vs 0.6%; RR: 1.01, 95% CI 0.45; 2.30). Results were consistent across subgroups and sensitivity analyses.

Characterization of agr-like Loci in Lactiplantibacillus plantarum and L. paraplantarum and Their Role in Quorum Sensing and Virulence Inhibition of Staphylococcus aureus

The pathogenicity of Staphylococcus aureus is largely regulated by the agr quorum sensing (QS) system encoded by agrBDCA, which coordinates virulence factor production through secretion and sensing of auto-inducing peptides (AIPs). agr-like systems are also present in coagulase-negative staphylococci, and several of these encode AIPs that inhibit S. aureus QS. In lactic acid bacteria, a similar locus was previously identified in Lactiplantibacillus plantarum WCSF1 termed lamBDCA. Here, we characterized the lamBDCA locus in L. plantarum LMG 13556 and L. paraplantarum CIRM-BIA 1870, and explored the effects on S. aureus QS. Notably, we found that co-cultivation with L. paraplantarum significantly inhibits S. aureus QS and hemolysin production, while less so for L. plantarum. The inhibition by L. paraplantarum was lost upon disruption of its lamBDCA locus, suggesting that the L. paraplantarum AIP mediates cross-species interference with S. aureus agr activation. Transcriptomic analysis revealed that lamBDCA in L. paraplantarum controls the expression of genes belonging to various functional categories, including stress response and metabolism. The latter includes genes encoding riboflavin (B2 vitamin) biosynthesis, which enabled the growth of the L. paraplantarum lamB mutant in the presence of roseoflavin, a toxic riboflavin analogue. Collectively, our results show that L. paraplantarum CIRM-BIA 1870 interferes with S. aureus virulence gene expression through QS suppression, and they implicate QS in the probiotic properties of L. paraplantarum.

Early cytokine signatures and clinical phenotypes discriminate persistent from resolving MRSA bacteremia

BACKGROUND

Staphylococcus aureus bacteremia (SAB) is a prevalent life-threatening infection often caused by methicillin-resistant S. aureus (MRSA). Up to 30% of SAB patients fail to clear infection even with gold-standard anti-MRSA antibiotics. This phenomenon is termed antibiotic-persistent MRSA bacteremia (APMB). The mechanisms driving APMB are complex and involve host phenotypes significantly impacting the immune response. Thus, defining early immune signatures and clinical phenotypes that differentiate APMB from antibiotic resolving (AR)MB could aid therapeutic success.

METHODS

We assessed 38 circulating cytokines and chemokines using affinity proteomics in 74 matched pairs of vancomycin-treated SAB cases identified as ARMB or APMB after 5 days of blood culture.

RESULTS

Unsupervised hierarchical clustering segregated APMB from ARMB based on differential levels of IL-10, IL-12p40, IL-13, CCL4, and TGFα. Additionally, CXCL1, CCL22 and IL-17A significantly differed between APMB and ARMB when correlated with diabetes, dialysis, metastatic infection, or cardiac vegetation. Combining immune signatures with these relevant clinical phenotypes sharply increased accuracy of discriminating APMB outcome to 79.1% via logistic regression modeling. Finally, classification-regression tree analysis revealed explicit analyte thresholds associated with APMB outcome at presentation especially in patients with metastatic infection.

CONCLUSIONS

Collectively, this study identifies previously unrecognized cytokine and chemokine signatures that distinguish APMB and ARMB at presentation and in the context of host clinical characteristics associated with increased disease severity. Validation of a biomarker signature that accurately predicts outcomes could guide early therapeutic strategies and interventions to reduce risks of persistent SAB that are associated with worsened morbidity and mortality.

TSST-1 promotes colonization of Staphylococcus aureus within the vaginal tract by activation of CD8+ T cells

Toxic shock syndrome toxin-1 (TSST-1) is a superantigen produced by Staphylococcus aureus and is the determinant of menstrual toxic shock syndrome (mTSS); however, the impact of TSST-1 on the vaginal environment beyond mTSS is not understood. Herein, we assessed how TSST-1 affects vaginal colonization by S. aureus, host inflammatory responses, and changes in microbial communities within the murine vagina. We demonstrated that TSST-1 induced a CD8+ T-cell-dependent inflammatory response in 24 h that correlated with S. aureus persistence within the vaginal tract. This increase was due to superantigen-dependent T-cell activation that triggered a change in microbial composition within the vaginal tract. Altogether, this study demonstrates that within the vaginal tract, TSST-1 modulates the vaginal microbiota to favor the survival of S. aureus in the absence of mTSS.IMPORTANCEToxic shock syndrome toxin-1 (TSST-1) is a superantigen toxin produced from Staphylococcus aureus that causes the menstrual form of toxic shock syndrome. This research demonstrates that TSST-1 also has a wider function within the vaginal tract than previously expected. We show that TSST-1, by activating CD8+ T cells, induces an inflammatory environment that modifies the vaginal microbiota to favor colonization by S. aureus. These are important findings as S. aureus can colonize the human vaginal tract efficiently and subsequently trigger dysbiosis within the microbial communities leading to several adverse outcomes such as decreased fertility, increased risks for sexually transmitted diseases, and issues related to pregnancy and birth.

Eradication of Antibiotic-Resistant Gram-Positive Bacteria and Biofilms by Rationally Designed AIE-Active Iridium(III) Complexes Derived from Cyclometalating 2-Phenylquinoline and Ancillary Bipyridyl Ligands

Antibiotic resistance caused by Gram-positive bacteria is a growing global human health threat. Selective discrimination and eradication of Gram-positive bacteria and their biofilms is challenging. Therapeutic strategies with multiple modes of action are urgently needed to address the increase in Gram-positive bacteria-resistant nosocomial infections. In this work, we have presented rationally designed aggregation-induced emission (AIE)-active cationic cyclometalated iridium(III) complexes derived from 2-phenylquinoline and 2,2'-bipyridine ligands for Gram-positive antibacterial studies. The AIE properties of these complexes were exploited for selective discrimination between Gram-positive and Gram-negative bacteria. These complexes displayed good antimicrobial activity against critical Gram-positive ESKAPE pathogens with minimum inhibitory concentrations in the low micromolar range but were inactive against Gram-negative pathogens. Importantly, the complexes can inhibit biofilm formation and eradicate bacteria from mature biofilms, which are major causes of persistent infections and antibiotic resistance and are more difficult to eliminate. In addition, these complexes showed low hemolytic activity against mammalian cells and a high therapeutic index, indicating good selectivity. Interestingly, the complexes kill bacteria through a variety of modes of mechanism, including ROS generation, cell membrane disruption, and depolarization and the loss of bacterial membrane integrity. These findings offer opportunities for designing metal AIEgens to treat Gram-positive bacterial infections effectively.

Altitudinal influence on survival mechanisms, nutritional composition, and antimicrobial activity of Moringa Peregrina in the summer climate of Fujairah, UAE

Extreme environments significantly impact the metabolic profiles of plants, leading to variations in chemical composition and bioactivity. This study investigates the effects of altitude, plant part age, and light exposure on the chemical composition and antimicrobial properties of Moringa peregrina. Based on our results, mineral contents were plant location dependent; while dry matter, ash, total digestible nutrients (TDN), fibre, protein, and tannins, were greater in the samples from the mountain. Vitamin E was more concentrated in the wadi. Vitamin A, selenium, phenols, and heavy metals were undetectable in both environments. Antimicrobial assays revealed stronger activity in mountain samples than the other locations. Age-dependent analyses showed that nitrogen, protein, ash, and electrolyte leakage were higher in young plant parts, whereas chlorophyll a and b levels were elevated in mature leaves and younger branches, particularly in lower elevations. Interestingly, young leaves from mountain regions had higher chlorophyll concentrations compared to mature leaves, contrasting with trends at other elevations. Photosynthetic photon flux density (PPFD) measurements were also highest in the mountain region. These findings suggest that M. peregrina employs diverse metabolic adaptations for survival in challenging environments, potentially offering socioeconomic value to indigenous communities through its bioactive properties.

Copper Nanoparticles Synthesized by Chemical Reduction with Medical Applications

Copper nanoparticles (CuNPs) have attracted attention due to their low cost and high specific surface area. In this work, a simple and inexpensive two-step synthesis method was proposed to prepare highly stable and well-dispersed spherical CuNPs in solution with a particle size of approximately 37 nm. Synthesis of CuNPs was carried on in the presence of complexing agent trisodium citrate (TSC), while for the chemical reduction step, sodium borohydride (NaBH4) was used. Taking into account the potential of this type of nanoparticles, their synthesis and characterization represent a current and relevant topic in the field. The ability to control the size, shape and properties of CuNPs by adjusting the synthesis parameters (pH, precursor:stabilizer:reductant ratio, homogenization time, temperature) offers extraordinary flexibility in the development of these materials. The combination of characterization techniques such as SEM, EDX, UV-Vis, Raman, FT-IR and AFM provides a thorough understanding of the structure and properties of CuNPs, allowing the modulation of the properties of the obtained nanoparticles in the desired direction. Based on the studies, the copper reduction mechanism was proposed. For the theoretical verification of the size of the experimentally obtained spherical CuNPs, Mie theory was applied. A stability study of the synthesized CuNPs in optimal conditions was performed using UV-Vis analysis at specific time intervals (1, 3, 30 and 60 days), the sample being kept in the dark, inside a drawer at 25 °C. The CuNPs obtained after setting the optimal synthesis parameters (Cu(II):TSC:BH4+ = 1:1:0.2, pH = 5, homogenization time 60 min and temperature 25 °C) were then tested to highlight their antibacterial effect on some reference bacterial strains. The obtained CuNPs demonstrated very good antimicrobial efficacy compared to traditional antimicrobials, for both Gram-negative and Gram-positive bacteria. This may reduce the development of antimicrobial resistance, an urgent medical issue. After evaluating the cytotoxic effects of CuNPs on the SKBR3 cancer cell line, a significant decrease in cell proliferation was observed at the 0.5 mg/mL concentration, with a reduction of 89% after 60 h of cultivation. Higher concentrations of CuNPs induced a more rapid cytotoxic effect, leading to an accelerated decline in cell viability.

Staphylococcus aureus in Inflammation and Pain: Update on Pathologic Mechanisms

Staphylococcus aureus (S. aureus) is a Gram-positive bacterium of significant clinical importance, known for its versatility and ability to cause a wide array of infections, such as osteoarticular, pulmonary, cardiovascular, device-related, and hospital-acquired infections. This review describes the most recent evidence of the pathogenic potential of S. aureus, which is commonly part of the human microbiota but can lead to severe infections. The prevalence of pathogenic S. aureus in hospital and community settings contributes to substantial morbidity and mortality, particularly in individuals with compromised immune systems. The immunopathogenesis of S. aureus infections involves intricate interactions with the host immune and non-immune cells, characterized by various virulence factors that facilitate adherence, invasion, and evasion of the host's defenses. This review highlights the complexity of S. aureus infections, ranging from mild to life-threatening conditions, and underscores the growing public health concern posed by multidrug-resistant strains, including methicillin-resistant S. aureus (MRSA). This article aims to provide an updated perspective on S. aureus-related infections, highlighting the main diseases linked to this pathogen, how the different cell types, virulence factors, and signaling molecules are involved in the immunopathogenesis, and the future perspectives to overcome the current challenges to treat the affected individuals.

Genomic characterization of healthcare-associated ST5 MRSA causing severe pseudomembranous enteritis in intensive care unit

BACKGROUND

Methicillin resistant Staphylococcus aureus (MRSA) is one of the main causes of hospital-acquired infections, but the diagnosis of MRSA pseudomembranous enteritis has faded in recent years. Here, we reported a pseudomembranous enteritis case in a young male patient caused by ST5 MRSA.

METHODS

Clinical data of the patient were collected from medical records. Mass spectrometry identification, antimicrobial susceptibility testing, whole genome sequencing, as well as resistance and virulence genes detection of MRSA strain were performed.

RESULTS

A 27-year-old young man with acute pancreatitis and septic shock in the intensive care unit passed large volume of intestine-like "stool" with more than 200 centimetres in length. A large number of Gram-positive cocci was persistently found in the stool samples. Histopathological examination of the intestine-like stool revealed that this stool was actually pseudomembrane, consisting of fibrinous exudate, inflammatory cells and clusters of gram-positive cocci adjacent to the luminal border. The patient was suspected for diagnosis of pseudomembranous enteritis. Stool and gastric juice cultures were positive for MRSA. These strains belonged to ST5-SCCmec II-t311, and harbored abundant virulence genes, especially enterotoxin genes. They contained not only sea, sec3, sel, but an enterotoxin gene cluster (egc, seg, sei, sem, sen, seo, yent1 and yent2), which may serve as an enterotoxin gene nursery. Besides, the strains were related to the isolates of the same hospital between 2013 and 2015, and there may be nosocomial transmission.

CONCLUSIONS

The severe clinical symptoms in this patient and the described virulence genes all suggested that these ST5 strains belonged to a kind of hypervirulent MRSA lineage. At the same time, the analysis of cgMLST indicated that there might be nosocomial transmission, which required the society to pay more attention to this highly virulent nosocomial clone.

Impeding Biofilm-Forming Mediated Methicillin-Resistant Staphylococcus aureus and Virulence Genes Using a Biosynthesized Silver Nanoparticles-Antibiotic Combination

Methicillin-resistant Staphylococcus aureus (MRSA) continues to represent a significant clinical challenge, characterized by consistently elevated rates of morbidity and mortality. Care regimen success is still difficult and necessitates assessing new antibiotics as well as supplemental services, including source control and searching for alternative approaches to combating it. Hence, we propose to synthesize silver nanoparticles (Ag-NPs) by employing a cell-free filter (CFF) of Streptomyces sp. to augment antibiotic activity and combat biofilm-forming MRSA. Seven bacterial isolates from clinical samples were identified, antibiotics were profiled with Vitek-2, and the phenotypic detecting of biofilm with Congo red medium and microplate assay was carried out. The PCR technique was used for detecting genes (icaA and icaD) coded in biofilm forming. The characterization of Ag-NPs was performed using several analytical methods, such as UV spectroscopy, dynamic light scattering (DLS), zeta potential measurement, transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The antibacterial properties of Ag-NPs and oxacillin-Ag-NPs were assessed against standard strains and clinical isolates by employing the agar well diffusion technique and the microdilution assay. The biogenic synthesis Ag-NPs resulted in uniformly spherical particles, with an average size of 20 nm. These Ag-NPs demonstrated significant activity against biofilm-forming MRSA, with minimum inhibitory concentrations (MICs) ranging from 12 to 15 μg/mL. Additionally, Ag-NPs completely impede biofilm formation by MRSA at sublethal doses of 0.75 MICs. The expression levels of the icaA and icaD genes were reduced by 1.9- to 2.2- and 2.4- to 2.8-fold, respectively. A significant synergistic effect was noted when Ag-NPs were used in combination with oxacillin, leading to reduced MICs of 1.87 μg/mL for oxacillin and 4.0 μg/mL for Ag-NPs against MRSA. The FICi of 0.375 further validated the synergistic relationship between oxacillin and Ag-NPs at the concentrations of 1.87 and 4 μg/mL. Findings from the time-kill test demonstrated the highest reduction in log10 (CFU)/mL of the initial MRSA inoculum after 12-hour exposure. The cytotoxicity analysis of Ag-NPs revealed no significant cytotoxic effects on the human skin cell line HFB-4 at low concentrations, with IC50 values of 61.40 µg/mL for HFB-4 and 34.2 µg/mL for HepG-2. Comparable with oxacillin-Ag-NPs, Ag-NPs showed no cytotoxic effects on HFB-4 at different concentrations and exhibited an IC50 value of 31.2 against HepG-2-cells. In conclusion, the biosynthesis of Ag-NPs has demonstrated effective antibacterial activity against MRSA and has completely hindered biofilm formation, suggesting a valuable alternative for clinical applications.

Exploring combination treatment options for persistent methicillin-susceptible Staphylococcus aureus bacteremia

PURPOSE

This review explores the management of persistent methicillin-susceptible Staphylococcus aureus bacteremia (SAB), emphasizing the importance of timely intervention due to SAB's association with metastatic dissemination, relapse, and mortality.

SUMMARY

The literature analysis first delves into risk factors for persistent SAB, highlighting the need for effective treatment strategies. The subsequent focus is on combination strategies for persistent SAB. Daptomycin, ertapenem, ceftaroline, fosfomycin, rifampin, and gentamicin are explored as adjuncts to cefazolin or antistaphylococcal penicillins. Daptomycin combination therapy is assessed through in vivo and clinical studies, indicating potential benefits, especially with higher-risk sources of infection. Ertapenem combination therapy has been demonstrated to have a synergistic effect with cefazolin, presenting a viable salvage option. Rifampin's ability to penetrate biofilm is examined, with discussion of inconclusive evidence on mortality benefits. The review also considers stewardship implications, discussing concerns such as resistance emergence, adverse events, and increased costs associated with combination therapy. Mathematical models suggest combination therapy as an effective approach to prevent resistance. Adverse events vary with each combination, and duration of therapy remains diverse across studies in the absence of well-established dosing guidelines.

CONCLUSION

The review provides a thorough exploration of the literature on treatment of persistent SAB, underscoring the need for evidence-based guidelines, further studies, and clinical judgment in tailoring treatment strategies. The multifaceted analysis contributes valuable insights for clinicians managing this challenging condition.

Antimicrobial Resistance Surveillance of Skin and Soft Tissue Infections: Hospital-Wide Bacterial Species and Antibiograms to Inform Management at a Zonal Tertiary Hospital in Mwanza, Tanzania

Purpose

The National Action Plan on antimicrobial resistance (NAP-AMR) in Tanzania is focused on blood stream infections and urinary tract infections despite skin and soft tissue infections (SSTIs) being common. This study assessed the proportion of laboratory-confirmed SSTIs, identify bacterial species involved, analyze AMR phenotypes, and investigate the risk factors associated with multidrug-resistant (MDR) SSTIs.

Patients and Methods

Analytical cross-sectional study was conducted between January and June 2023, involving 614 patients with SSTIs. Patients' information was collected using standard AMR surveillance tools, and either pus swabs or pus aspirate or necrotic tissues were collected and analyzed using standard microbiological procedures, WHONET and STATA software programs.

Results

The median age (interquartile range) of patients was 34 (14-54) years with males accounting for 54.4%. Laboratory-confirmed SSTIs was 72.5% (445/614), yielding 586 bacterial isolates. The most frequent SSTIs types were surgical site infections (30.0%), chronic wounds (27.9%), and traumatic wounds (19.7%). The commonest pathogens were Staphylococcus aureus (17.1%), Escherichia coli (17.1%), and K. pneumoniae (16.0%). The AMR phenotypes identified were methicillin resistant Staphylococcus aureus, 29.0%; Extended-spectrum beta lactamase producing Gram-negative bacteria, 47.3%; and carbapenem resistant Gram-negative bacteria, 12.9%. The overall MDR SSTIs was 40.9% (251/614) and was significantly higher among inpatients compared to outpatients [OR (95% CI); p-value: 1.86 (1.33-2.59); p-value<0.001].

Conclusion

Approximately three-quarter of patients have laboratory-confirmed SSTIs caused predominantly by MDR pathogens. Revisiting SSTIs treatment guidelines at BMC and inclusion of SSTIs in the on-going AMR surveillance in Tanzania are recommended.

Protection of Mice Vaccinated with a New B Cell and T Cell Epitopes Cocktail from Staphylococcus aureus Challenge in Skin Infection Model

Developing an effective vaccine against Staphylococcus aureus (S. aureus) is a key global health concern, especially with the increased reports of multidrug-resistant (MDR) S. aureus strains. Previous attempts for S. aureus vaccine development were unsuccessful. In this study, Manganese transport protein C (MABC) B cell epitopes, Nickel ABC transporter (NABC) B cell & T cell epitopes, and Phosphatidylinositol phosphodiesterase (PIc) B cell & T cell epitopes were used as a vaccine in mice skin infection model. Mice immunized with peptide mixture and MABC peptide group showed the best skin lesion healing results. The protection level was correlated with the highest IgG level, highest levels of interferon-gamma (INF γ), and lowest levels of interleukin-2 (IL-2). The peptide mixture group also showed the highest count of CD4/ CD8 cells. Results demonstrated that the inclusion of B cell and T cell epitopes of multiple genes improved both the humoral and cellular immunity and resulted in the best outcome in the skin infection mice model. A more expanded in-vivo study in different mice models is recommended for testing MABC, NABC, and PIc B cells and T cells peptides cocktail as promising S. aureus vaccine.

The Staphylococcus aureus non-coding RNA IsrR regulates TCA cycle activity and virulence

Staphylococcus aureus has evolved mechanisms to cope with low iron (Fe) availability in host tissues. Staphylococcus aureus uses the ferric uptake transcriptional regulator (Fur) to sense titers of cytosolic Fe. Upon Fe depletion, apo-Fur relieves transcriptional repression of genes utilized for Fe uptake. We demonstrate that an S. aureus Δfur mutant has decreased expression of acnA, which codes for the Fe-dependent enzyme aconitase. This prevents the Δfur mutant from growing with amino acids as sole carbon and energy sources. We used a suppressor screen to exploit this phenotype and determined that a mutation that decreases the transcription of isrR, which produces a regulatory RNA, increased acnA expression, thereby enabling growth. Directed mutation of bases predicted to facilitate the interaction between the acnA transcript and IsrR, decreased the ability of IsrR to control acnA expression in vivo and IsrR bound to the acnA transcript in vitro. IsrR also bound transcripts coding the alternate tricarboxylic acid cycle proteins sdhC, mqo, citZ and citM. Whole-cell metal analyses suggest that IsrR promotes Fe uptake and increases intracellular Fe not ligated by macromolecules. Lastly, we determined that Fur and IsrR promote infection using murine skin and acute pneumonia models.

Clinical and epidemiological differences in staphylococcal osteoarticular infections: insights for developing hospital-based infection control interventions

PURPOSE

Osteoarticular infections (OAI) are serious clinical conditions with Staphylococcus aureus and Coagulase-negative Staphylococcus (CoNS) responsible for up to two-thirds of cases. This work aimed to compare the epidemiological, clinical, and microbiological characteristics of OAI caused by S. aureus versus CoNS to aid in clinical management and infection control strategies.

METHODS

A single-centre retrospective study was performed at the Centro Hospitalar e Universitário de Coimbra for the period of January 2011 to December 2021. A total of 458 cases of OAI were gathered. Data was retrieved from medical records and statistical analysis was performed with SPSS.

RESULTS

S. aureus accounted for 60.7% of infections, followed by S. epidermidis (29.9%). Independent risk factors for S. aureus infections included being male (p < 0.001; OR = 0.47) and a history of osteomyelitis (p < 0.001; OR = 0.18). In contrast, CoNS infections were associated with older age (p = 0.018), carrying a prosthetic device (p < 0.001; OR = 2.92), and a prior periprosthetic infection (p = 0.023; OR = 1.86). Both groups exhibited significant antimicrobial resistance, with CoNS showing greater resistance to gentamicin, linezolid, teicoplanin and trimethoprim-sulfamethoxazole, while S. aureus was more commonly resistant to clindamycin.

CONCLUSION

Our findings show the distinct characteristics of OAI caused by S. aureus and CoNS, highlighting the need for targeted risk factor management and tailored empiric antibiotic therapy to reduce incidence and improve outcomes.

Killed whole-cell Staphylococcus aureus formulation in Montanide ISA266 and Alum adjuvants: different vaccine formulations varied in the vaccine's potency and efficacy

Immunotherapy can be a sensible alternative because invasive Staphylococcus aureus infection mortality, morbidity, and cost are still alarmingly high despite the development of multiple new medications to treat methicillin-resistant S. aureus infections. Herein, killed whole-cell Staphylococcus aureus was formulated in Montanide ISA266 and Alum adjuvants, and the potency and efficacy of the vaccine were studied. After the preparation of two kinds of whole-cell vaccine (bacterin and lysate), 20 µg of each vaccine candidate was formulated in Montanide ISA266 and Alum adjuvants, then subcutaneously injected in distinct groups. Blood samples were taken two weeks after each booster injection, and two booster shots were given at 2-week intervals. Sera were examined by ELISA for total IgG, isotypes (IgG1 and IgG2a), and cytokine production (IFN-γ and IL-4), respectively, to ascertain the kind of induced immune response. Experimental mice were challenged intraperitoneally with 5 × 108 CFU of bacteria 2 weeks after their last immunization, and the mortality rate and bacterial load were measured. Both immunogens elicited strong humoral immune responses, producing antibodies that improved opsonic capability, IFN-γ, and IL-4 production and protectivity in response to the experimental challenge. Compared to other immunized groups, the lysate formulation with Montanide ISA266 produced a greater antibody titer and IgG1 isotype and showed the highest vaccine potency. Additionally, combining the whole-cell vaccine (bacterin and lysate) with the adjuvant Montanide ISA266 increased IFN-γ and IL-4 cytokines response and protection in the experimental challenge. These findings show that avoiding S. aureus infection using active vaccination with inactivated whole-cell vaccines (bacterin and lysate) may be a successful strategy. The type of adjuvant in the vaccine formulation is important and influences vaccine potency and efficacy.

Dual role of Baimao-Longdan-Congrong-Fang in inhibiting Staphylococcus aureus virulence factors and regulating TNF-α/TNFR1/NF-κB/MMP9 axis

BACKGROUND

Baimao-Longdan-Congrong-Fang (BLCF), a traditional Chinese herbal formula described in the Taiping Shenghui Fang (998 AD), consists of medicinal plants with heat-clearing and tonifying properties. BLCF has a promise as a treatment for Staphylococcus aureus (S. aureus) pneumonia, according to its historical use and current pharmacological research.

PURPOSE

In this study, the inhibitory effects of BLCF on S. aureus virulence factors were evaluated in vitro, and its mechanisms of action were investigated in a methicillin-resistant S. aureus (MRSA) pneumonia mouse model.

METHODS

The inhibitory effect of BLCF on S. aureus virulence factors, including sortase A (SrtA) and α-hemolysin (Hla), was investigated by fluorescence resonance energy transfer (FRET) and hemolysis assays. A C57BL/6J mouse model of MRSA pneumonia was employed to evaluate its therapeutic efficacy. Accordingly, an integrated strategy of medicinal chemistry, network pharmacology analysis, GEO database analysis, bioinformatics, molecular docking, molecular dynamics simulation, GeneMANIA-based functional association (GMFA), and GSEA was used to identify and illustrate potential therapeutic targets and mechanisms. Subsequently, the mechanistic results were confirmed by Western blot analysis and RT-qPCR.

RESULTS

While BLCF exhibited weak inhibitory activity against S. aureus USA300, Newman, and SA37 strains, it significantly suppressed SrtA-related virulence functions without affecting bacterial growth. FRET and hemolysis assays confirmed that BLCF inhibited SrtA activity (IC50 = 1.25 mg/mL) while decreasing hemolytic activity. Furthermore, BLCF protected mice from MRSA infection, increasing their survival rates. Bioinformatics analysis identified 26 active compounds and 2 hub genes (Tnf and Mmp9) that were associated with 5 types of immune cell, including activated CD4 T cells, myeloid-derived suppressor cells, activated dendritic cells, macrophages, and mast cells. Molecular docking revealed 3 active compounds (isoacteoside, verbascoside, and echinacoside) that exhibited strong binding affinities to TNF, MMP9, and SrtA. Molecular dynamics simulations validated the stable interactions between isoacteoside and the target proteins, yielding binding energies of -136.76 ± 8.83 kJ/mol, -174.98 ± 14.89 kJ/mol, and -186.34 ± 9.06 kJ/mol, respectively. The therapeutic effect of BLCF was closely linked to the NF-κB signaling pathway, as revealed by GMFA and GSEA analyses. In vivo, BLCF reduced lung bacterial load, improved the wet/dry ratio, and decreased inflammatory cytokines, thereby enhancing lung histopathology through modulation of the TNF-α/TNFR1/NF-κB/MMP9 axis.

CONCLUSIONS

BLCF can effectively treat MRSA pneumonia in mice by inhibiting SrtA activity, decreasing hemolytic activity, and regulating the TNF-α/TNFR1/NF-κB/MMP9 axis. These findings suggest BLCF, a traditional herbal formula, as a promising novel therapeutic approach to treat pneumonia.

Evaluation of Liposome-Encapsulated Vancomycin Against Methicillin-Resistant Staphylococcus aureus

Background/Objectives: Methicillin-resistant Staphylococcus aureus (MRSA) is a global health concern due to its resistance to conventional antibiotics. This study evaluated the efficacy of liposome-encapsulated vancomycin against MRSA using phospholipids extracted from egg yolk. Liposomes were prepared via the freeze-thaw method, yielding vesicles with an average diameter of 157.01 ± 33.04 nm and a polydispersity index (PDI) of 0.0442, indicating uniformity and stability. Antibacterial activity was assessed using the microdilution method. Liposome-encapsulated vancomycin demonstrated complete bacterial growth inhibition (100%) against MRSA ATCC 2758 at dilutions of 101 and 102, compared to only 50% inhibition by free vancomycin at 101. At higher dilutions (103), liposome-encapsulated vancomycin maintained 70% inhibition, whereas free vancomycin was ineffective. In vivo studies using a murine wound infection model revealed that wounds treated with liposome-encapsulated vancomycin achieved superior healing, with complete tissue regeneration observed by day 14. Histological analysis showed reduced inflammation and enhanced tissue recovery in liposome-encapsulated vancomycin-treated groups, compared to fibrosis and persistent necrosis in free vancomycin-treated groups. By enabling sustained drug release and improved bioavailability, liposomal formulations minimized required dosages and systemic toxicity, reducing the risk of resistance development. This study highlights the clinical potential of liposome-encapsulated vancomycin as a scalable, cost-effective treatment for MRSA, particularly in resource-limited settings.

Heme and immunity: The heme oxygenase dichotomy

Heme, an iron containing organic ring, is required for a diverse range of biological processes across all forms of life. Although this nutrient is essential, its pro-inflammatory and cytotoxic properties can lead to cellular damage. Heme oxygenase 1 (HO-1) is an endoplasmic reticulum (ER)-anchored enzyme that degrades heme, releasing equimolar amounts of carbon monoxide (CO), biliverdin (BV), and iron. The induction of HO-1 by heme presents an interesting dichotomy in the cell: CO and BV possess anti-inflammatory and antioxidant properties while free iron can be detrimental as it can generate hydroxyl radicals through the Fenton reaction. The heme/HO-1 axis is tightly regulated, and can influence cell fate, local tissue environments, and disease outcomes during pathogen infection. In this review we explore the role of heme during macrophage polarization and its ability to act as an immune activator while also examining the contribution of HO-1 and heme during infections with intracellular and extracellular pathogens. We highlight work from the emerging field of nutritional immunity of heme and iron, and how the substrates and byproducts of heme metabolism via HO-1 can be beneficial to the host or the pathogen depending on the context.

In situ dual-targeted drug delivery system for alleviating imaging and pathological damage in septic arthritis

Septic arthritis is a severe disease that damages articular cartilage and triggers a strong inflammatory response. Current treatments mainly depend on systemic antibiotics and lack effective intra-articular therapies, as well as standardized animal models, and precise detection methods. In this study, we present a drug delivery system responsive to the bacterial microenvironment for targeted inflammation control, along with an effective method for monitoring changes in septic arthritis in SD rats. This system consists a core with pH-sensitive metal-organic frameworks ZIF-8 loading anti-inflammatory drugs indomethacin and a shell with hybrid cell membranes from macrophages (MM) and platelets (PM), refer as MP@ZIF-8@IN. This system, which diverges from traditional treatments, enhances drug utilization, prolongs local retention, and allows for spontaneous release at the treatment site, thereby enabling the exclusive intra-articular treatment of septic arthritis. The drug delivery system inhibits the NF-κB pathway, reduces oxidative stress, and regulates macrophage polarization, preventing cartilage destruction. Additionally, in this standardized animal model utilizing the knee joints of SD rats, we have developed musculoskeletal ultrasound and magnetic resonance imaging for time-based monitoring, thus overcoming the limitation of conventional methods, which are unsuitable for soft tissue analysis. Our findings advance therapeutic strategies for septic arthritis and encourage further application of visualization techniques in related fields. STATEMENT OF SIGNIFICANCE: This study presents significant advancements in the treatment and understanding of septic arthritis. Our customized drug delivery system targets bacteria and macrophages, ensuring long-time drug retention and enhanced inflammation control, all while reducing reliance on antibiotics-an important step toward addressing antibiotic resistance. Additionally, we have refined septic arthritis animal models to establish clearer guidelines for intervention timing, grounded in clinical symptoms and imaging data. This addresses a critical gap in current research and offers a practical framework for future therapeutic approaches.

Antimicrobial Phenolic Materials: From Assembly to Function

Infectious diseases pose considerable challenges to public health, particularly with the rise of multidrug-resistant pathogens that globally cause high mortality rates. These pathogens can persist on surfaces and spread in public and healthcare settings. Advances have been made in developing antimicrobial materials to reduce the transmission of pathogens, including materials composed of naturally sourced polyphenols and their derivatives, which exhibit antimicrobial potency, broad-spectrum activity, and a lower likelihood of promoting resistance. This review provides an overview of recent advances in the fabrication of antimicrobial phenolic biomaterials, where natural phenolic compounds act as active antimicrobial agents or encapsulate other antimicrobial agents (e.g., metal ions, antimicrobial peptides, natural biopolymers). Various forms of phenolic biomaterials synthesized through these two strategies, including antimicrobial particles, capsules, hydrogels, and coatings, are summarized, with a focus on their application in wound healing, bone repair and regeneration, oral health, and antimicrobial coatings for medical devices. The potential of these advanced phenolic biomaterials provides a promising therapeutic approach for combating antimicrobial-resistant infections and reducing microbial transmission.

The role and mechanism of efflux pump norB in biofilm formation of Staphylococcus aureus

Staphylococcus aureus (S. aureus) is one of the notorious bacteria responsible for community and hospital infections. It can attach to the indwelling medical devices to form biofilms, which increases resistance to antibiotics and causes frequent chronic or persistent infections. This study attempted to determine the contribution and mechanism between the efflux pump norB gene and biofilm development in S. aureus. The expression levels of norB gene were detected by quantitative real-time polymerase chain reaction (qRT-PCR). The norB gene knockout strain USA300 ΔnorB was constructed by homologous recombination technology. Crystal violet staining was utilized to detect the biofilm formation ability. Differentially expressed genes between norB knockout strains and wild-type strains were screened by RNA-Seq technology and verified by qRT-PCR. In comparison to strains with weak biofilm development capacity, higher expression levels of the norB gene were detected in S. aureus strains that showed strong biofilm forming capabilities. The expression levels of norB were significantly up-regulated in biofilm bacteria in comparison to planktonic bacteria. The knockout of norB gene reduced the biofilm formation ability in S. aureus. The deletion of norB gene up-regulated the expression of genes related to biofilm formation including agrD, sdrC, sdrD, agrB, agrC, fnbB, nuc, lytS, lrgA, sdrE, agrA and saeS, and down-regulated the expression of genes related to biofilm formation including clfA, icaR, sarA and rot. In conclusion, the efflux pump norB gene serves as a crucial role in the production of biofilm, thus rendering it a promising avenue for biofilm suppression.

Infection prevention-how can we prevent transmission of community-onset methicillin-resistant Staphylococcus aureus?

BACKGROUND

Staphylococcus aureus is a versatile organism, capable of existing as a commensal organism while also possessing pathogenic potential. The emergence of clinically and genetically distinct strains of methicillin-resistant S. aureus (MRSA), termed community-onset MRSA (CO-MRSA), resulted in an epidemic of invasive and skin and soft tissue infections (SSTI) in otherwise healthy individuals without traditional risk factors. Colonization with S. aureus is a risk factor for developing infection and also a source of transmission to close contacts. Outbreaks of S. aureus SSTI have been described in crowded settings and within households. Thus, preventive strategies are essential to interrupt recurrent infections.

OBJECTIVES

The objective of this narrative review is to provide a comprehensive, evidence-based approach to prevent transmission of CO-MRSA. We highlight key clinical trials that emphasize the importance of household and environmental S. aureus colonization in propagating household transmission. Finally, we highlight research priorities to prevent S. aureus infection.

SOURCES

We cite primary literature from peer-reviewed publications as sources for this review.

CONTENT

Our recommended approach to the management of individuals presenting with skin abscesses includes optimal treatment of the initial infection and hygiene education. Decolonization measures should be recommended for individuals with recurrent SSTIs or whose household members have SSTIs. Targeted decolonization with topical antimicrobials should be prescribed to all affected individuals within the household.

IMPLICATIONS

S. aureus infections result in substantial mortality and morbidity because of the high incidence of recurrent skin infections. Although current decolonization strategies are beneficial, interventions are often costly to families and effectiveness wanes over time. Results from a recently completed trial evaluating integrated periodic decolonization and household environmental hygiene will further add to our understanding of what constitutes a sustainable decolonization approach. In addition, novel preventive strategies are being developed such as S. aureus vaccines, lytic agents, probiotics, microbiota transplants, and phage therapy.