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

Ferrous sulfate remodels the properties of sodium alginate-based hydrogel and facilitates the healing of wound infection caused by MRSA

Frequent occurrence of wound infection caused by multiple-resistant bacteria (MRB) has posed a serious challenge to the current healthcare system relying on antibiotics. The development of novel antimicrobial materials with high safety and efficacy to heal wound infection is of great importance in combating this crisis. Herein, we prepared a promising antibacterial hydrogel by cross-linking ferrous ions (Fe2+) with the deprotonated carboxyl anion in sodium alginate (Na-ALG) to cure wound infections caused by methicillin-resistant Staphylococcus aureus (MRSA). Interestingly, ferrous-modified Na-ALG (Fe-ALG) hydrogel demonstrated better properties compared to the traditional Na-ALG-based hydrogels, including injectability, self-healing, appropriate fluidity, high-water retention, potent MRSA-killing efficacy, and excellent biocompatibility. Importantly, the addition of Fe2+ enhances the antibacterial efficacy of the Na-ALG hydrogel, enabling it to effectively eliminate MRSA and accelerate the healing of antibiotic-resistant bacterial-infected wounds in a remarkably short period (10 days). This modification not only facilitates wound closure and fur generation, but also mitigates systemic inflammation, thereby effectively impeding the spread of MRSA to the lungs. Taken together, Fe-ALG hydrogel is a promising therapeutic material for treating wound infections by Staphylococcus aureus, especially by antibiotic-resistant strains like MRSA.

YjbH contributes to Staphylococcus aureus skin pathology and immune response through Agr-mediated α-toxin regulation

Staphylococcus aureus is the most common cause of skin and soft tissue infections (SSTIs) with Methicillin-Resistant S. aureus (MRSA) strains being a major contributor in both community and hospital settings. S. aureus relies on metabolic diversity and a large repertoire of virulence factors to cause disease. This includes α-hemolysin (Hla), an integral player in tissue damage found in various models, including SSTIs. Previously, we identified a role for the Spx adapter protein, YjbH, in the regulation of several virulence factors and as an inhibitor of pathogenesis in a sepsis model. In this study, we found that YjbH is critical for tissue damage during SSTI, and its absence leads to decreased proinflammatory chemokines and cytokines in the skin. We identified no contribution of YjbI, encoded on the same transcript as YjbH. Using a combination of reporters and quantitative hemolysis assays, we demonstrated that YjbH impacts Hla expression and activity both in vitro and in vivo. Additionally, expression of Hla from a non-native promoter reversed the tissue damage phenotype of the ΔyjbIH mutant. Lastly, we identified reduced Agr activity as the likely cause for reduced Hla production in the ΔyjbH mutant. This work continues to define the importance of YjbH in the pathogenesis of S. aureus infection as well as identify a new pathway important for Hla production.

Small regulatory RNA RSaX28 promotes virulence by reinforcing the stability of RNAIII in community-associated ST398 clonotype Staphylococcus aureus

Staphylococcus aureus (S. aureus) is a notorious pathogen that cause metastatic or complicated infections. Hypervirulent ST398 clonotype strains, remarkably increased in recent years, dominated Community-associated S. aureus (CA-SA) infections in the past decade in China. Small RNAs like RNAIII have been demonstrated to play important roles in regulating the virulence of S. aureus, however, the regulatory roles played by many of these sRNAs in the ST398 clonotype strains are still unclear. Through transcriptome screening and combined with knockout phenotype analysis, we have identified a highly transcribed sRNA, RSaX28, in the ST398 clonotype strains. Sequence analysis revealed that RSaX28 is highly conserved in the most epidemic clonotypes of S. aureus, but its high transcription level is particularly prominent in the ST398 clonotype strains. Characterization of RSaX28 through RACE and Northern blot revealed its length to be 533nt. RSaX28 is capable of promoting the hemolytic ability, reducing biofilm formation capacity, and enhancing virulence of S. aureus in the in vivo murine infection model. Through IntaRNA prediction and EMSA validation, we found that RSaX28 can specifically interact with RNAIII, promoting its stability and positively regulating the translation of downstream alpha-toxin while inhibiting the translation of Sbi, thereby regulating the virulence and biofilm formation capacity of the ST398 clonotype strains. RSaX28 is an important virulence regulatory factor in the ST398 clonotype S. aureus and represents a potential important target for future treatment and immune intervention against S. aureus infections.

Within-host genomic evolution of methicillin-resistant Staphylococcus aureus in long-term carriers

Assessing the genomic evolution of Staphylococcus aureus can help us understand how the bacteria adapt to its environment. In this study, we aimed to assess the mutation rate within 144 methicillin-resistant Staphylococcus aureus (MRSA) carriers with a carriage time from 4 to 11 years, including some carriers who belonged to the same households. We found that 23 of the 144 individuals had completely different MRSA types over time and were therefore not long-term carriers of the same MRSA. From the remaining 121 individuals, we performed whole-genome sequencing (WGS) on 424 isolates and then compared these pairwise using core genome multilocus sequence typing (cgMLST) and single-nucleotide polymorphism (SNP) analyses. We found a median within-host mutation rate in long-term MRSA carriers of 4.9 (3.4-6.9) SNPs/genome/year and 2.7 (1.8-4.2) allelic differences/genome/year, when excluding presumed recombination. Furthermore, we stratified the cohort into subgroups and found no significant difference between the median mutation rate of members of households, individuals with presumed continued exposure, e.g., from travel and persons without known continued exposure. Finally, we found that SNPs occurred at random within the genes in our cohort. KEY POINTS: • Median mutation rate within long-term MRSA carriers of 4.9 (3.4-6.9) SNPs/genome/year • Similar median mutation rates in subgroups (households, travelers) • No hotspots for SNPs within the genome.

Panicum maximum Jacq. mediated green synthesis of silver nanoparticles: synthesis, characterization, and biological activities supported by molecular docking

This study uses the aerial parts of Panicum maximum total extract (PMTE) to synthesize silver nanoparticles (AgNPs) in an environmentally friendly manner. TEM, SEM, FTIR, X-ray powder diffraction (XRD), Zeta potential, UV, and FTIR were used to characterize the green silver nanoparticles (PM-AgNPs). PM-AgNPs were evaluated as anticancer agents compared to (PMTE) against breast (MCF-7), lung (A549), and ovary adenocarcinoma (SKOV3) human tumour cells. The antibacterial activity of AgNPs was assessed against Staphylococcus aureus isolates. The PM-AgNPs had an absorbance of 418 nm, particle size of 15.18 nm, and zeta potential of -22.4 mV, ensuring the nanosilver's stability. XRD evaluated the crystallography nature of the formed PM-AgNPs. The cytotoxic properties of PM-AgNPs on MCF-7 and SKOV 3 were the strongest, with IC50s of 0.13 ± 0.015 and 3.5 ± 0.5 g/ml, respectively, as compared to A549 (13 ± 3.2 µg/mL). The increase in the apoptotic cells was 97.79 ± 1.61 and 96.6 ± 1.91% for MCF-7 and SKOV3 cell lines, respectively. PM-AgNPs were found to affect the membrane integrity and membrane permeability of 50 and 43.75% of the tested isolates, respectively. Also, PM-AgNPs have recorded a reduction in the biofilm formation of S. aurues. These results suggest using PM-AgNPs to treat breast and ovarian cancers.

Discovery of quaternized pyridine-thiazole-ruthenium complexes as potent anti-Staphylococcus aureus agents

Quaternization of ruthenium complexes may be a promising strategy for the development of new antibiotics. In response to the increasing bacterial resistance, we integrated the quaternary amine structure into the design of ruthenium complexes and evaluated their antibacterial activity. All the ruthenium complexes showed good antibacterial activity against the tested Staphylococcus aureus (S. aureus). Ru-8 was the most effective antibacterial agent that displayed excellent antibacterial activity against S. aureus (MIC = 0.78-1.56 μg/mL). In vitro experiments showed that all nine ruthenium complexes had low hemolytic toxicity to rabbit erythrocytes. Notably, Ru-8 was found to disrupt bacterial cell membranes, alter their permeability, and induce ROS production in bacteria, all the above leading to the death of bacteria without inducing drug resistance. To further explore the antibacterial activity of Ru-8in vivo, we established a mouse skin wound infection model and a G. mellonella larvae infection model. Ru-8 exhibited significant antibacterial efficacy against S. aureus in vivo and low toxicity to mouse tissues. The Ru-8 showed low toxicity to Raw264.7 cells (mouse monocyte macrophage leukemia cells). This study indicates that the ruthenium complex ruthenium quaternary was a promising strategy for the development of new antibacterial agents.

The monotopic quinone reductases from Staphylococcus aureus

Staphylococcus aureus, a Gram-positive bacterium, is an opportunistic pathogen and one of the most frequent causes for community acquired and nosocomial infections that has become a major public health threat due to the increased incidence of its drug resistance. Although being a prominent pathogen, its energetic metabolism is still underexplored, and its respiratory enzymes have been escaping attention. S. aureus can adapt to different environmental conditions by performing both aerobic and anaerobic respirations, which is particularly important as it frequently colonizes niches with different oxygen concentrations. This adaptability is derived from the composition of its respiratory chain, specifically from the presence of terminal electron acceptor reductases. The plasticity of S. aureus energy metabolism is enlarged by the ten quinone reductases encoded in its genome, eight of them being monotopic proteins. The role of these proteins is critical as they connect the different catabolic pathways to the respiratory chain. In this work, we identify, describe, and revise the monotopic quinone reductases present in S. aureus, providing an integrated view of its respiratory chain.

Advances in antibacterial activity of zinc oxide nanoparticles against Staphylococcus aureus (Review)

Nanoparticles (NPs) are one of the promising strategies to deal with bacterial infections. As the main subset of NPs, metal and metal oxide NPs show destructive power against bacteria by releasing metal ions, direct contact of cell membranes and antibiotic delivery. Recently, a number of researchers have focused on the antibacterial activity of zinc oxide nanoparticles (ZnO NPs) against Staphylococcus aureus (S. aureus). Currently, there is a lack of a comprehensive review on ZnO NPs against S. aureus. Therefore, in this review, the antibacterial activity against S. aureus of ZnO NPs made by various synthetic methods was summarized, particularly the green synthetic ZnO NPs. The synergistic antibacterial effect against S. aureus of ZnO NPs with antibiotics was also summarized. Furthermore, the present review also emphasized the enhanced activities against S. aureus of ZnO nanocomposites, nano-hybrids and functional ZnO NPs.

Immunoinformatic approach for multi-epitope vaccine design against Staphylococcus aureus based on hemolysin proteins

Staphylococcus aureus is a common bacterium that causes a variety of infections in humans. This microorganism produces several virulence factors, including hemolysins, which contribute to its disease-causing ability. The treatment of S. aureus infections typically involves the use of antibiotics. However, the emergence of antibiotic-resistant strains has become a major concern. Therefore, vaccination against S. aureus has gained attention as an alternative approach. Vaccination has the advantage of stimulating the immune system to produce specific antibodies that can neutralize bacteria and prevent infection. However, developing an effective vaccine against S. aureus has proven to be challenging. This study aimed to use in silico methods to design a multi-epitope vaccine against S. aureus infection based on hemolysin proteins. The designed vaccine contained four B-cell epitopes, four CTL epitopes, and four HTL epitopes, as well as the ribosomal protein L7/L12 and pan-HLA DR-binding epitope, included as adjuvants. Furthermore, the vaccine was non-allergenic and non-toxic with the potential to stimulate the TLR2-, TLR-4, and TLR-6 receptors. The predicted vaccine exhibited a high degree of antigenicity and stability, suggesting potential for further development as a viable vaccine candidate. The population coverage of the vaccine was 94.4 %, indicating potential widespread protection against S. aureus. Overall, these findings provide valuable insights into the design of an effective multi-epitope vaccine against S. aureus infection and pave the way for future experimental validations.

Computational exploration of natural compounds targeting Staphylococcus aureus: inhibiting AgrA promoter binding for antimicrobial intervention

Staphylococcus aureus is a highly virulent nosocomial pathogen that poses a significant threat to individuals exposed to healthcare settings. Due to its sophisticated machinery for producing virulence factors, S. aureus can cause severe and potentially fatal infections in humans. This study focuses on the response regulator AgrA, which plays a crucial role in regulating the production of virulence factors in S. aureus. The objective is to identify natural compounds that can inhibit the binding of AgrA to its promoter site, thus inhibiting the expression of virulence genes. To achieve this, a pharmacophore model was generated using known drugs and applied to screen the ZINC natural product database. The resulting compounds were subjected to molecular docking-based virtual screening against the C-terminal DNA binding domain of AgrA. Three compounds, namely ZINC000077269178, ZINC000051012304, and ZINC000004266026, were shortlisted based on their strong affinity for key residues involved in DNA binding and transcription initiation. Subsequently, the unbound and ligand-bound complexes were subjected to a 200 ns molecular dynamics simulation to assess their conformational stability. Various analyses, including RMSD, RMSF, Rg, SASA, Principal Component Analysis, and Gibbs free energy landscape, were conducted on the simulation trajectory. The RMSD profile indicated similar fluctuations in both bound and unbound structures, while the Rg profile demonstrated the compactness of the protein without any unfolding during the simulation. Furthermore, Principal component analysis revealed that ligand binding reduced the overall atomic motion of the protein whereas free energy landscape suggested the energy variations obtained in complexes.Communicated by Ramaswamy H. Sarma.

Characterization of virulence factors and antimicrobial resistance in Staphylococcus spp. isolated from clinical samples

The virulence factors, antibiotic resistance patterns, and the associated genetic elements have been investigated in Staphylococcus species. A total of 100 strains has been isolated from clinical samples in the Microbiology Laboratory of Hesperia Hospital, Modena, Italy, and identified as Staphylococcus aureus (65), Staphylococcus epidermidis (24), Staphylococcus hominis (3), Staphylococcus saprophyticus (3), and Staphylococcus warneri (5). All the strains were analyzed to determine phenotypic and genotypic characters, notably the virulence factors, the antibiotics susceptibility, and the genetic determinants. The highest percentage of resistance in Staphylococcus spp. was found for erythromycin and benzylpenicillin (87% and 85%, respectively). All S. aureus, two S. epidermidis (8.3%), and one S. saprophyticus (33.3%) strains were resistant to oxacillin. The methicillin resistance gene (mecA) was detected by polymerase chain reaction (PCR) amplification in 65 S. aureus strains and in 3 coagulase-negative staphylococci (CoNS) (8.6%). With regard to the virulence characteristics, all the S. aureus were positive to all virulence tests, except for slime test. Among the CoNS isolates, 19 (79.1%) S. epidermidis and one (33.3%) S. saprophyticus strains resulted positive for the slime test only. The results obtained are useful for a more in-depth understanding of the function and contribution of S. aureus and CoNS antibiotic resistance and virulence factors to staphylococcal infections. In particular, the production of slime is very important for CoNS, a virulence factor frequently found in infections caused by these strains. Further investigations on the genetic relatedness among strains of different sources will be useful for epidemiological and monitoring purposes and will enable us to develop new strategies to counteract the diffusion of methicillin-resistant S. aureus (MRSA) and CoNS strains not only in clinical field, but also in other related environments.

Preparation of ceftiofur-encapsulated hen-egg low-density lipoproteins and their antibacterial effects on intracellular Staphylococcus aureus

Hen egg low-density lipoprotein (heLDL), as alternative of serum-derived LDL, was used as drug delivery system of ceftiofur (CEF). The CEF-loaded hen egg low-density lipoprotein (CEF-heLDL) with complete apolipoprotein structure and high drug loading rate was synthesized, possesses suitable particle size. CEF-heLDL undergoes cellular uptake and colocalizes with lysosomes in vitro. An intracellular infection model of the bovine endometrial epithelial cells and a coeliac-induced inflammation model of mice by Staphylococcus aureus (S. aureus) were established, and significantly lower intracellular S. aureus levels of CEF-heLDL group than CEF-free group (P < 0.001) was observed. The antibacterial efficacy was sustained for 24 h. Up to 400 mg/kg of CEF-heLDL, 20 times the clinical practice, were intraperitoneally administrated, and no significant toxicity signs on mice were observed. HeLDLs is an effective, safe, and cheap drug carrier, and could also be used for transmembrane delivering other antibiotics.

Cationic homopolypeptides: A versatile tool to design multifunctional antimicrobial nanocoatings

Postoperative infections are the most common complications faced by surgeons after implant surgery. To address this issue, an emerging and promising approach is to develop antimicrobial coatings using antibiotic substitutes. We investigated the use of polycationic homopolypeptides in a layer-by-layer coating combined with hyaluronic acid (HA) to produce an effective antimicrobial shield. The three peptide-based polycations used to make the coatings, poly(l-arginine) (PAR), poly(l-lysine), and poly(l-ornithine), provided an efficient antibacterial barrier by a contact-killing mechanism against Gram-positive, Gram-negative, and antibiotic-resistant bacteria. Moreover, this activity was higher for homopolypeptides containing 30 amino-acid residues per polycation chain, emphasizing the impact of the polycation chain length and its mobility in the coatings to deploy its contact-killing antimicrobial properties. However, the PAR-containing coating emerged as the best candidate among the three selected polycations, as it promoted cell adhesion and epithelial monolayer formation. It also stimulated nitric oxide production in endothelial cells, thereby facilitating angiogenesis and subsequent tissue regeneration. More interestingly, bacteria did not develop a resistance to PAR and (PAR/HA) also inhibited the proliferation of eukaryotic pathogens, such as yeasts. Furthermore, in vivo investigations on a (PAR/HA)-coated hernia mesh implanted on a rabbit model confirmed that the coating had antibacterial properties without causing chronic inflammation. These impressive synergistic activities highlight the strong potential of PAR/HA coatings as a key tool in combating bacteria, including those resistant to conventional antibiotics and associated to medical devices.

Acute kidney injury in Staphylococcus aureus bacteraemia: a recurrent events analysis

OBJECTIVES

To estimate risk factors for acute kidney injury (AKI) and the effect of AKI on mortality in Staphylococcus aureus bacteraemia, while taking into account recurrent AKI episodes, competing risks, time-varying variables, and time-varying effects.

METHODS

We performed an unplanned analysis using data from a multicentre cohort study of patients with Staphylococcus aureus bacteraemia (SAB). The primary outcome was cumulative incidence of AKI, according to Kidney Disease Improving Global Outcomes definitions.

RESULTS

We included 453 patients in this study of whom 194 (43%) patients experienced one or more AKI episodes. Age (hazard ratio (HR) 1.013, 95% CI 1.001-1.024), Charlson comorbidity index (HR 1.07, 95% CI 1.01-1.14), prior chronic kidney disease (HR 1.76, 95% CI 1.28-2.42), septic shock (HR 3.28, 95% CI 2.31-4.66), persistent bacteraemia (HR 1.53, 95% CI 1.08-2.17), and vancomycin therapy (HR 1.80, 95% CI 1.05-3.09) were independently associated with AKI, but flucloxacillin, cefazolin, rifampicin, and aminoglycoside therapy were not. After adjustment for confounders and immortal time bias, AKI was associated with an increased risk of 90-day mortality (HR 4.26, 95% CI 2.91-6.23).

DISCUSSION

The incidence of AKI in SAB is high and a substantial proportion of patients develop recurrent episodes of AKI after recovery. AKI is specifically linked to the use of vancomycin and not to anti-staphylococcal penicillins. The clinical outcome of patients with SAB complicated by AKI is worse than previously estimated.

Cellulose from bacteria as a delivery system for improved treatment of infectious diseases: A review of updates and prospects

Cellulose from bacteria is a high-purity biomaterial naturally produced by bacteria as part of their metabolic process. Although it inherently lacks antimicrobial activity, its modification with bioactive substances can significantly enhance its efficacy beyond that of the original compounds. This biomaterial features a unique ability to retain substantial quantities of liquids within its three-dimensional network, making it a prime candidate for biomedical applications. Versatile in its properties, it can be utilized across various industries. Previous research has highlighted its capacity to exhibit antimicrobial properties and to encapsulate nanostructured materials, thereby augmenting its antibacterial effectiveness. This review focuses on the use of cellulose from bacteria as a carrier for active compounds, specifically targeting antibacterial activity against drug-resistant strains. We explore its role in innovative bacterial cellulose-based systems, which present a promising solution for tackling bacterial resistance. This review aims to showcase the potential of bacterial cellulose in developing new devices and treatment strategies that address critical concerns in global health.

ESKAPE pathogens: antimicrobial resistance, epidemiology, clinical impact and therapeutics

The rise of antibiotic resistance and a dwindling antimicrobial pipeline have been recognized as emerging threats to public health. The ESKAPE pathogens - Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp. - were initially identified as critical multidrug-resistant bacteria for which effective therapies were rapidly needed. Now, entering the third decade of the twenty-first century, and despite the introduction of several new antibiotics and antibiotic adjuvants, such as novel β-lactamase inhibitors, these organisms continue to represent major therapeutic challenges. These bacteria share several key biological features, including adaptations for survival in the modern health-care setting, diverse methods for acquiring resistance determinants and the dissemination of successful high-risk clones around the world. With the advent of next-generation sequencing, novel tools to track and combat the spread of these organisms have rapidly evolved, as well as renewed interest in non-traditional antibiotic approaches. In this Review, we explore the current epidemiology and clinical impact of this important group of bacterial pathogens and discuss relevant mechanisms of resistance to recently introduced antibiotics that affect their use in clinical settings. Furthermore, we discuss emerging therapeutic strategies needed for effective patient care in the era of widespread antimicrobial resistance.

Antibiofilm and wound healing efficacy of rhamnolipid biosurfactant against pathogenic bacterium Staphylococcus aureus

The present study evaluates the in-vitro antibiofilm activity against the biofilm formed by Staphylococcus aureus, and the wound-healing efficacy of two different types of rhamnolipids produced by Pseudomonas aeruginosa strain JS29 in S.aureus infected wounds. The biosurfactant production was carried out in a mineral salt medium supplemented with 2 % Glucose and 2 % Glycerol individually and thus were designated as RL-Glu and RL-Gly respectively. 0.5 mg/ml of RL-Glu and RL-Gly demonstrated 90 % growth inhibition of S. aureus while exhibiting bactericidal activity at 4 mg/ml of RL-Glu and 1 mg/ml of RL-Gly. Both types of rhamnolipid cause changes in membrane permeability leading to pathogens' non-viability. 90 % inhibition of biofilm formation by S. aureus was observed at 2 mg/ml of RL-Glu and 0.5 mg/ml of RL-Gly, while 0.5 mg/ml of both rhamnolipid disrupted 90 % of the preformed biofilm. 0.5 mg/ml of RL-Glu and RL-Gly decreases the production of exopolysaccharides and also causes structural alteration. 0.5 mg/ml of RL-Glu and RL-Gly were found to exhibit effective wound healing efficacy in S. aureus infected wounds within 7 days of treatment. Histopathological studies of wound sites revealed efficient wound management by both the rhamnolipid. LCMS and GCMS characterization of the biosurfactant revealed that JS29 produces different rhamnolipid congeners when grown on different carbon sources, thereby influencing the antimicrobial, antibiofilm, and wound healing efficacy of rhamnolipid.

Self-activated hydrogel cascade reactor integrated with glucose oxidase and silver nanoparticle for enhanced treatment of bacterial infection

The recognition of silver nanoparticles (AgNPs) as a nanozyme with peroxidase-like activity has offered a promising solution to address the challenges of bacterial resistance and argyria risk. However, the catalytic efficacy of AgNPs is limited by the need for a strong acidic environment and high concentrations of hydrogen peroxide (H2O2). In this work, we developed a self-activated hydrogel cascade reactor (AUGP) for enhanced treatment of bacterial infection. The AUGP integrates the properties of glucose oxidase (GOx) and polyacrylamide (pAAm) hydrogel microsphere. The confinement effect of pAAm hydrogel microsphere enables glucose oxidation to occur in a confined space, which creates an acidic environment to activate AgNPs activity, initiating the cascade reaction between GOx and AgNPs. Meanwhile, the confinement effect facilitates the accumulation of a high local concentration of H2O2, allowing AUGP to generate hydroxyl radicals (•OH) without the need for external H2O2. Additionally, the release of Ag+ from AUGP is achieved upon the generation of •OH. The synergistic action of Ag+ and •OH confers exceptional antibacterial efficacy to AUGP. Importantly, the etching effect of H2O2 ensures the absence of any residual AgNPs, reducing the risk of argyria. In vivo studies validated the efficacy of AUGP in wound disinfection with minimal toxicity.

Portable SERS biosensor based on aptamer-assisted catalytic hairpin assembly signal amplification for ultrasensitive detection of Staphylococcus aureus

Bacteria infections pose a serious threat to public health, and it is urgent to develop facile and accurate detection methods. To meet the important need, a potable and high-sensitive surface enhanced Raman scattering (SERS) biosensor based on aptamer recognition and catalytic hairpin assembly (CHA) signal amplification was proposed for point-of-care detection of Staphylococcus aureus (S. aureus). The SERS biosensor contains three parts: recognition probes, SERS sensing chip, and SERS tags. The feasibility of the strategy was verified by gel electrophoresis, and the one-step test route was optimized. The bacteria SERS biosensor has a good linear relationship ranging from 10 to 107 CFU mL-1 with high sensitivity low to 5 CFU mL-1, and shows excellent specificity, uniformity, and repeatability on S. aureus identification and enumeration, which can distinguish S. aureus from other bacteria. The SERS biosensor shows a good recovery rate (95.73 %-109.65 %) for testing S. aureus spiked in milk, and has good practicability for detecting S. aureus infected mouse wound, which provides a facile and reliable approach for detection of trace bacteria in the real samples.

A case of multiple cerebral hemorrhages followed by shower emboli

An 87-year-old woman was admitted to our hospital (day 0) because of acute disorientation caused by multiple acute intracerebral hemorrhages. T2*-weighted magnetic resonance imaging (MRI) at admission revealed multiple subcortical old microbleeds indicative of cerebral amyloid angiopathy. Microbleeds in the right cerebellar hemisphere and acute spotty ischemia in the left cerebellum were also identified. The patient had been afebrile, and blood examinations on day 7 were within normal limits of inflammatory findings without antibiotics. On day 11, she developed a high fever and blood culture was performed. Her fever resolved within 2 days of antibiotic administration, although subsequent findings revealed her blood culture was positive for Staphylococcus aureus. Echocardiogram revealed bacterial vegetation in the mitral valve and moderate mitral regurgitation, with a diagnosis of infectious endocarditis (IE). Follow-up MRI demonstrated multiple spotty acute infarctions and an increased number of microbleeds. The patient may have been infected via peripheral infusions administered during the first few days after admission. However, considering the coexistence of acute hemorrhagic and ischemic lesions on MRI, as well as the acute lesions in the cerebellum, it is possible that IE was already latent on admission, and that the multiple brain hemorrhages might have been caused by IE rather than by cerebral amyloid angiopathy.

Changes in stresses sensitivity of ohmic heating-induced sublethally injured Staphylococcus aureus during repair: Potential mechanisms at the cellular and molecular levels

Ohmic heating (OH), an emerging food processing technology employed in the food processing industry, raises potential food safety concerns due to the recovery of sublethally injured pathogens such as Staphylococcus aureus (S. aureus). In the present study, sensitivity to various stress conditions and the changes in cellular-related factors of OH-injured S. aureus during repair were investigated. The results indicated that liquid media differences (nutrient broth (NB), phosphate-buffered saline (PBS), milk, and cucumber juice) affected the recovery process of injured cells. Nutrient enrichment determines the bacterial repair rate, and the rates of repair for these media were milk > NB > cucumber juice > PBS. The sensitivity of injured cells to various stressors, including different acids, temperature, nisin, simulated gastric fluid, and bile salt, increased during the injury phase and subsequently diminished upon repair. Additionally, the intracellular ATP content, enzyme activities (Na+/K+-ATPase, Ca2+/Mg2+-ATPase, and T-ATPase) and ion concentrations (Mg2+, K+, and Ca2+) gradually increased during repair. After 5 h of repair, the intracellular substances content of cell's was significantly higher than that of the injured bacteria without repair, while some indicators (e.g., Na+/K+-ATPase, K+, and Ca2+) were not restored to the untreated level. The results of this study indicated that OH-injured S. aureus exhibited strengthened resistance post-recovery, potentially due to the restoration of cellular structures. These findings have implications for optimizing food storage conditions and advancing OH processes in the food industry.

Low concentrations of tetrabromobisphenol A promote the biofilm formation of methicillin-resistant Staphylococcus aureus

The effect and underlying mechanism of tetrabromobisphenol A (TBBPA), a plastic additive, on biofilm formation of methicillin-resistant Staphylococcus aureus (MRSA USA300) remain unknown. This study first investigated the impact of different concentrations of TBBPA on the growth and biofilm formation of USA300. The results indicated that a low concentration (0.5 mg/L) of TBBPA promoted the growth and biofilm formation of USA300, whereas high concentrations (5 mg/L and 10 mg/L) of TBBPA had inhibitory effects. Further exploration revealed that the low concentration of TBBPA enhance biofilm formation by promoting the synthesis of extracellular proteins, release of extracellular DNA (eDNA), and production of staphyloxanthin. RTqPCR analysis demonstrated that the low concentration of TBBPA upregulated genes associated with extracellular protein synthesis (sarA, fnbA, fnbB, aur) and eDNA formation (atlA) and increased the expression of genes involved in staphyloxanthin biosynthesis (crtM), suggesting a potential mechanism for enhanced resistance of USA300 to adverse conditions. These findings shed light on how low concentrations of TBBPA facilitate biofilm formation in USA300 and highlight the indirect impact of plastic additives on pathogenic bacteria in terms of human health. In the future, in-depth studies about effects of plastic additives on pathogenicity of pathogenic bacteria should be conducted. CAPSULE: The protein and eDNA contents in biofilms of methicillin-resistant Staphylococcus aureus are increased by low concentrations of TBBPA.

Vaccines and monoclonal antibodies to prevent healthcare-associated bacterial infections

SUMMARYHealthcare-associated infections (HAIs) represent a burden for public health with a high prevalence and high death rates associated with them. Pathogens with a high potential for antimicrobial resistance, such as ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) and Clostridioides difficile, are responsible for most HAIs. Despite the implementation of infection prevention and control intervention, globally, HAIs prevalence is stable and they are mainly due to endogenous pathogens. It is undeniable that complementary to infection prevention and control measures, prophylactic approaches by active or passive immunization are needed. Specific groups at-risk (elderly people, chronic condition as immunocompromised) and also healthcare workers are key targets. Medical procedures and specific interventions are known to be at risk of HAIs, in addition to hospital environmental exposure. Vaccines or monoclonal antibodies can be seen as attractive preventive approaches for HAIs. In this review, we present an overview of the vaccines and monoclonal antibodies in clinical development for prevention of the major bacterial HAIs pathogens. Based on the current state of knowledge, we look at the challenges and future perspectives to improve prevention by these means.

Ultrasonic nanotechnology for the effective management of Staphylococcus aureus skin infections: an update

Ultrasonic nanotechnology represents a groundbreaking advancement in the management of Staphylococcus aureus skin infections, addressing the significant limitations of conventional treatments. S. aureus poses substantial challenges, including antibiotic resistance and biofilm formation, necessitating novel and effective approaches. By harnessing the power of ultrasonic waves and nanostructures, this technology offers a precise mechanism to disrupt bacterial cells, enhancing antibiotic susceptibility and facilitating the eradication of bacterial colonies. This innovative approach not only improves treatment outcomes, but also offers a non-invasive and highly efficient alternative to traditional methods. Recent studies have demonstrated the remarkable efficacy of ultrasonic nanotechnology, showcasing its ability to revolutionize the treatment paradigm for S. aureus infections. Ongoing research is dedicated to refining treatment protocols, developing new nanostructures, and assessing clinical applicability, with a focus on overcoming challenges such as scalability and long-term effectiveness. This review provides a comprehensive overview of the current state of ultrasonic nanotechnology in combating S. aureus skin infections, detailing its mechanism of action, summarizing key research findings, and highlighting its superiority over conventional modalities. Accumulating evidence underscores its potential as a pivotal development in modern science and technology, promising significant advancements in infection management strategies. As research continues to evolve, the optimization of protocols, exploration of innovative applications, and translation into clinical practice are poised to further solidify the transformative impact of ultrasonic nanotechnology in the medical field.

The role of male hormones in bacterial infections: enhancing Staphylococcus aureus virulence through testosterone-induced Agr activation

Staphylococcus aureus is a notorious pathogen predominantly involved in skin and soft tissue infections, exhibiting a distinct innate sex bias. This study explores the influence of testosterone on the virulence of S. aureus and elucidates its underlying mechanisms. Utilizing a skin abscess model in intact and castrated male mice, we assessed the effects of testosterone on S. aureus pathogenicity. Compared to controls, castrated mice showed significantly reduced abscess sizes and decreased bacterial loads, highlighting the role of testosterone in modulating the severity of S. aureus infections. In vitro experiments revealed that testosterone enhances the hemolytic activity, cytotoxicity, and oxidative stress resistance of S. aureus. Real-time quantitative PCR analysis showed a significant upregulation of the genes encoding α-hemolysin (hla) and phenol-soluble modulin (psmα). Importantly, testosterone treatment significantly enhanced the expression of the accessory gene regulator (Agr) quorum-sensing system components (agrC, agrA, agrB, agrD), while the SaeRS system (saeR, saeS, and sbi) exhibited only slight changes. Gene knockout experiments revealed that deletion of agrC, rather than saeRS and agrBD, abolishes the testosterone-induced enhancement of hemolysis and gene expression, underscoring the key role of AgrC. Molecular docking simulations indicated a direct interaction between testosterone and AgrC protein, with a strong binding affinity at the active site residue SER201. This study provides new insights into the mechanistic basis of how testosterone enhances the pathogenicity of S. aureus, potentially contributing to increased male susceptibility to S. aureus infections and offering a targeted approach for therapeutic interventions.

Genome-based model for differentiating between infection and carriage Staphylococcus aureus

Staphylococcus aureus (S. aureus) is a clinically significant opportunistic pathogen, which can colonize multiple body sites in healthy individuals and cause various life-threatening diseases in both children and adults worldwide. The genetic backgrounds of S. aureus that cause infection versus asymptomatic carriage vary widely, but the potential genetic elements (k-mers) associated with S. aureus infection remain unknown, which leads to difficulties in differentiating infection isolates from harmless colonizers. Here, we address the disease-associated k-mers by using a comprehensive genome-wide association study (GWAS) to compare the genetic variation of S. aureus isolates from clinical infection sites (272 isolates) with nasal carriage (240 isolates). This study uncovers consensus evidence that certain k-mers are overrepresented in infection isolates compared with carriage isolates, indicating the presence of specific genetic elements associated with S. aureus infection. Moreover, the random forest (RF) model achieved a classification accuracy of 77% for predicting disease status (infection vs carriage), with 68% accuracy for a single highest-ranked k-mer, providing a simple target for identifying high-risk genotypes. Our findings suggest that the disease-causing S. aureus is a pathogenic subpopulation harboring unique genomic variation that promotes invasion and infection, providing novel targets for clinical interventions.

IMPORTANCE

Defining the disease-causing isolates is the first step toward disease control. However, the disease-associated genetic elements of Staphylococcus aureus remain unknown, which leads to difficulties in differentiating infection isolates from harmless carriage isolates. Our comprehensive genome-wide association study (GWAS) found consensus evidence that certain genetic elements are overrepresented among infection isolates than carriage isolates, suggesting that the enrichment of disease-associated elements may promote infection. Notably, a single k-mer predictor achieved a high classification accuracy, which forms the basis for early diagnostics and interventions.

Antivirulence activities of Rutin-loaded chitosan nanoparticles against pathogenic Staphylococcus aureus

BACKGROUND

Staphylococcus aureus is an infectious bacterium that is frequently found in healthcare settings and the community. This study aimed to prepare rutin-loaded chitosan nanoparticles (Rut-CS NPs) and assess their antibacterial activity against pathogenic strains of S. aureus.

RESULTS

The synthesized Rut-CS NPs exhibited an amorphous morphology with a size ranging from 160 to 240 nm and a zeta potential of 37.3 mV. Rut-CS NPs demonstrated significant antibacterial activity against S. aureus strains. Following exposure to Rut-CS NPs, the production of staphyloxanthin pigment decreased by 43.31-89.63%, leading to increased susceptibility of S. aureus to hydrogen peroxide. Additionally, visual inspection of cell morphology indicated changes in membrane integrity and permeability upon Rut-CS NPs exposure, leading to a substantial increase (107.07-191.08%) in cytoplasmic DNA leakage in the strains. Furthermore, ½ MIC of Rut-CS NPs effectively inhibited the biofilm formation (22.5-37.5%) and hemolytic activity (69-82.59%) in the S. aureus strains.

CONCLUSIONS

Our study showcases that Rut-CS NPs can serve as a novel treatment agent to combat S. aureus infections by altering cell morphology and inhibiting virulence factors of S. aureus.

Computational Screening of T-Muurolol for an Alternative Antibacterial Solution against Staphylococcus aureus Infections: An In Silico Approach for Phytochemical-Based Drug Discovery

Staphylococcus aureus infections present a significant threat to the global healthcare system. The increasing resistance to existing antibiotics and their limited efficacy underscores the urgent need to identify new antibacterial agents with low toxicity to effectively combat various S. aureus infections. Hence, in this study, we have screened T-muurolol for possible interactions with several S. aureus-specific bacterial proteins to establish its potential as an alternative antibacterial agent. Based on its binding affinity and interactions with amino acids, T-muurolol was identified as a potential inhibitor of S. aureus lipase, dihydrofolate reductase, penicillin-binding protein 2a, D-Ala:D-Ala ligase, and ribosome protection proteins tetracycline resistance determinant (RPP TetM), which indicates its potentiality against S. aureus and its multi-drug-resistant strains. Also, T-muurolol exhibited good antioxidant and anti-inflammatory activity by showing strong binding interactions with flavin adenine dinucleotide (FAD)-dependent nicotinamide adenine dinucleotide phosphate (NAD(P)H) oxidase, and cyclooxygenase-2. Consequently, molecular dynamics (MD) simulation and recalculating binding free energies elucidated its binding interaction stability with targeted proteins. Furthermore, quantum chemical structure analysis based on density functional theory (DFT) depicted a higher energy gap between the highest occupied molecular orbital and lowest unoccupied molecular orbital (EHOMO-LUMO) with a lower chemical potential index, and moderate electrophilicity suggests its chemical hardness and stability and less polarizability and reactivity. Additionally, pharmacological parameters based on ADMET, Lipinski's rules, and bioactivity score validated it as a promising drug candidate with high activity toward ion channel modulators, nuclear receptor ligands, and enzyme inhibitors. In conclusion, the current findings suggest T-muurolol as a promising alternative antibacterial agent that might be a potential phytochemical-based drug against S. aureus. This study also suggests further clinical research before human application.

Characterising the role of enolase in a stable Small Colony Variant of Staphylococcus aureus isolated from a diabetic foot infection patient with osteomyelitis

The switch to alternate cell types by Staphylococcus aureus creates sub-populations even within an active population, that are highly resilient, tolerant to antibiotics and lack clinical symptoms of infection. These cells present a challenge for clinical treatment where even after initial intervention has seemingly cleared the infection, these alternate cell types persist within tissue to revert and cause disease. Small colony variants (SCV) are a cell type which facilitate persistent infection but clinically isolated SCVs are often unstable in laboratory conditions. We have isolated a pair of S. aureus isolates from an individual patient with osteomyelitis presenting with heterogenous phenotypes; a stable SCV (sSCV) and a SCV that reverts upon laboratory culturing to the usual, active and non-SCV cell type. Thus we are able use this pair to investigate and compare the genetic mechanisms that underlie the clinical variatons of SCV phenotype. The switch to the sSCV phenotype was associated with frameshift mutations in the enolase eno and the histidine kinase arlS. The phenoptye of the sSCV was an impeded growth dependent on amino acid catabolism and modulated biofilm. These mutations present potentially a new molecular mechanism which confer persistence within osteomyelitis.

Nanoarchitectonics of in Situ Antibiotic-Releasing Acicular Nanozymes for Targeting and Inducing Cuproptosis-like Death to Eliminate Drug-Resistant Bacteria

A series of progress has been made in the field of antimicrobial use of nanozymes due to their superior stability and decreased susceptibility to drug resistance. However, catalytically generated reactive oxygen species (ROS) are insufficient for coping with multidrug-resistant organisms (MDROs) in complex wound environments due to their low targeting ability and insufficient catalytic activity. To address this problem, chemically stable copper-gallic acid-vancomycin (CuGA-VAN) nanoneedles were successfully constructed by a simple approach for targeting bacteria; these nanoneedles exhibit OXD-like and GSH-px-like dual enzyme activities to produce ROS and induce bacterial cuproptosis-like death, thereby eliminating MDRO infections. The results of in vitro experiments showed that the free carboxylic acid of GA could react with the free ammonia of teichoic acid in the methicillin-resistant Staphylococcus aureus (MRSA) cell wall skeleton. Thus, CuGA-VAN nanoneedles can rapidly "capture" MRSA in liquid environments, releasing ROS, VAN and Cu2+ on bacterial surfaces to break down the MRSA barrier, destroying the biofilm. In addition, CuGA-VAN effectively promoted wound repair cell proliferation and angiogenesis to facilitate wound healing while ensuring biosafety. According to transcriptome sequencing, highly internalized Cu2+ causes copper overload toxicity; downregulates genes related to the bacterial glyoxylate cycle, tricarboxylic acid cycle, and oxidative respiratory chain; and induces lipid peroxidation in the cytoplasm, leading to bacterial cuproptosis-like death. In this study, CuGA-VAN was cleverly designed to trigger a cascade reaction of targeting, drug release, ROS-catalyzed antibacterial activity and cuproptosis-like death. This provides an innovative idea for multidrug-resistant infections.

Laurocapram, a transdermal enhancer, boosts cephalosporin's antibacterial activity against Methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA), a notorious bacterium with high drug resistance and easy recurrence after surgery, has posed significant clinical treatment challenges. In the current scarcity of new antibiotics, the identification of adjuvants to existing antibiotics is a promising approach to combat infections caused by multidrug-resistant Gram-positive bacteria. The in vitro synergy test, which included a MIC assay, time-kill curve, antimicrobial susceptibility testing, and live/dead bacteria staining assay, revealed that laurocapram, a widely used chemical transdermal enhancer, could potentiate the antibacterial activity of cephalosporins against MRSA. In vitro, laurocapram combined with cefixime showed an excellent synergistic activity against MRSA (FICI = 0.28 ± 0.00). In addition, the combination of laurocapram and cefixime may inhibited the formation of MRSA biofilm and caused cell membrane damage. Following that, we discovered that combining laurocapram with cefixime could alleviate the symptoms of mice in the MRSA skin infection model and the MRSA pneumonia model. In conclusion, laurocapram is a promising and low-cost antibacterial adjuvant, providing a new strategy for further exploring the use of lower doses of cephalosporins to combat MRSA infection.

The transcriptional changes of LrgA discriminates the responsiveness of Staphylococcus aureus towards blue light from that of photodynamic inactivation

Antimicrobial blue light (aBL) is utilized as a new approach to inhibit the growth of Staphylococcus aureus (S. aureus). Mediated by the endogenous chromophore, aBL possesses the similar photokilling property with aPDI (antimicrobial photodynamic inactivation), however, their mechanistic discrepancies in triggering the death of staphylococcal cells are not yet understood. Here, we describe the use of a 460-nm-LED to curb the viability of S. aureus. According to the results, the bacterial survival was sharply decreased when blue light was applied, reaching a maximum of 4.11 ± 0.04 log10 units. Moreover, the membrane integrity was damaged by aBL, causing the leakage of intracellular DNA. Transcriptomic analysis indicates the divergent gene expression upon either aBL or aPDI, with pathways such as transport, DNA repair, expression regulation and porphyrin massively affected by aBL. Among the commonly regulated genes, LrgA was underpinned on account of its involvement with biofilm formation and protein transport. By comparing the wildtype with the LrgA-overexpressing (LrgA+) strain, the survival rate, membrane penetration, surface structure and biofilm formation were, to a varying degree, improved for LrgA+, which may suggest that LrgA plays essential roles in modulating the responsiveness of S. aureus. Besides, LrgA may function through regulating the expression of autolysis-related systems. Finally, LrgA overexpression did not attenuate but aggravate the impairment induced by aPDI, showcasing a distinct responsive strategy from aBL. Taken together, this study unveils a unique molecular alteration for the aBL-mediated inactivation, providing the basis of utilizing blue light to reduce the harm brought by S. aureus.

Aspirin and Ticagrelor Versus Aspirin and Clopidogrel or Prasugrel and the Effect on Staphylococcal-associated Infections: A Real-world Study

PURPOSE

Antiplatelet therapy is used for the primary and secondary prevention of thrombotic diseases such as acute coronary syndrome (ACS). These patients are more vulnerable to infections, as such, strategies are required to mitigate these risks.

METHODS

We conducted a retrospective cohort study using TriNetX, a global federated health research network that includes both inpatient and outpatient electronic medical records from health care organizations worldwide. Patients ≥18 years old, after ACS, who were placed on aspirin and ticagrelor were compared with patients placed on aspirin and clopidogrel or prasugrel. Patients were identified using International Statistical Classification of Diseases and Related Health Problems terminology codes. After propensity score matching (1:1), a total of 239,358 patients were identified in each cohort. The primary outcomes of interest investigated were rates of (1) acute and subacute infective endocarditis, (2) sepsis of unknown origin, (3) staphylococcus arthritis, (4) cellulitis and acute lymphangitis, (5) Staphylococcus aureus bacteremia, and (6) staphylococcal pneumonia after initiation of treatment. Outcomes were analyzed at 1, 3, and 5 years.

FINDINGS

At 5 years, a combination of aspirin and ticagrelor, compared with a combination of aspirin and clopidogrel or prasugrel, was associated with significantly reduced rates of (1) acute and subacute endocarditis (hazard ratio [HR] plus 95% CI) (HR = 0.85; 0.77-0.945; P = 0.030), (2) sepsis of unknown origin (HR = 0.89; 95% CI, 0.86-0.91; P < 0.0001), (3) cellulitis and acute lymphangitis (HR = 0.89; 95% CI, 0.87-0.92; P < 0.0001, and (4) Staphylococcus aureus bacteremia (HR = 0.72; 95% CI, 0.61-0.85; P = 0.0007). However, a combination of aspirin and clopidogrel was associated with a marinally lower risk of staphylococcal pneumonia (HR = 1.04; 95% CI, 1.01-1.062; P < 0.0001).

IMPLICATIONS

A combination of aspirin and ticagrelor is associated with a lower rate of a variety of bacterial infections. This combination warrants further investigation in in-vitro studies to tease out mechanisms and through clinical randomized trials in groups who have ACS and are at high infection risk.

Clinical presentation and microbiological characteristics of community-acquired Staphylococcus aureus bacteraemia at a tertiary hospital in Costa Rica

Introduction. Staphylococcus aureus is a leading agent in community-acquired bacteraemia (CAB) and has been linked to elevated mortality rates and methicillin resistance in Costa Rica.Gap statement and aim. To update and enhance previous data obtained in this country, we analysed the clinical manifestations of 54 S. aureus CAB cases in a tertiary hospital and delineated the sequence types (STs), virulome, and resistome of the implicated isolates.Methodology. Clinical information was retrieved from patient files. Antibiotic susceptibility profiles were obtained with disc diffusion and automated phenotypic tests. Genomic data were exploited to type the isolates and for detection of resistance and virulence genes.Results. Primary infections predominantly manifested as bone and joint infections, followed by skin and soft tissue infections. Alarmingly, 70% of patients continued to exhibit positive haemocultures beyond 48 h of treatment modification, with nearly a quarter requiring mechanical ventilation or developing septic shock. The 30-day mortality rate reached an alarming 40%. More than 60% of the patients were found to have received suboptimal or inappropriate antibiotic treatment, and there was an alarming tendency towards the overuse of third-generation cephalosporins as empirical treatment. Laboratory tests indicated elevated creatinine levels, leukocytosis, and bandaemia within the first 24 h of hospitalization. However, most showed improvement after 48 h. The isolates were categorized into 13 STs, with a predominance of representatives from the clonal complexes CC72 (ST72), CC8 (ST8), CC5 (ST5, ST6), and CC1 (ST188). Twenty-four isolates tested positive for mecA, with ST72 strains accounting for 20. In addition, we detected genes conferring acquired resistance to aminoglycosides, MLSB antibiotics, trimethoprim/sulfamethoxazole, and mutations for fluoroquinolone resistance in the isolate collection. Genes associated with biofilm formation, capsule synthesis, and exotoxin production were prevalent, in contrast to the infrequent detection of enterotoxins or exfoliative toxin genes.Conclusions. Our findings broaden our understanding of S. aureus infections in a largely understudied region and can enhance patient management and treatment strategies.

Polymicrobial purulent pericarditis and peritoneal effusion in an immunocompromised patient with Staphylococcus aureus bacteraemia: a case report

Background

Polymicrobial pericarditis is an extremely rare and lethal form of pericarditis. Prompt initiation of appropriate antimicrobial treatment and pericardial drainage are crucial.

Case summary

A 57-year-old immunocompromised male patient presented to the emergency department due to dyspnoea, chest pain, and fever lasting for 7 days. Following clinical, laboratory, and imaging work-up, he was found to have pericardial effusion with signs of tamponade. After pericardiocentesis through subxiphoid and apical approaches, 800 mL of gross purulent fluid was obtained. Blood and pericardial fluid cultures confirmed the diagnosis of polymicrobial purulent pericarditis (Staphylococcus aureus and Bacteroides vulgatus). Further work-up revealed minor peritoneal effusion, and paracentesis fluid culture revealed the presence of S. aureus and, additionally, Candida albicans. After treatment initiation with intravenous antibiotics, pericardial, drainage and supportive measures, the patient's condition initially improved despite the development of constrictive pericarditis. However, he suddenly deteriorated after 37 days of hospitalization and passed away after 51 days of hospitalization.

Discussion

To the best of our knowledge, this is the first report of purulent pericarditis and purulent peritoneal effusion in the settings of S. aureus bacteraemia with an absent primary infection focus. Clinicians should be aware of treatment options for purulent pericarditis and consider intrapericardial fibrinolysis, especially in patients not suited for more invasive pericarditis treatment.

Sinigrin reduces the virulence of Staphylococcus aureus by targeting coagulase

Multi-resistant Staphylococcus aureus (S. aureus) infection is a significant global health concern owing to its high mortality and morbidity rates. Coagulase (Coa), a key enzyme that activates prothrombin to initiate host coagulation, has emerged as a promising target for anti-infective therapeutic approaches. This study identified sinigrin as a potent Coa inhibitor that significantly inhibited S. aureus-induced coagulation at concentration as low as 32 mg/L. Additionally, at a higher concentration of 128 mg/L, sinigrin disrupted the self-protection mechanism of S. aureus. Thermal shift and fluorescence-quenching assays confirmed the direct binding of sinigrin to the Coa protein. Molecular docking analysis predicted specific binding sites for sinigrin in the Coa molecule, and point mutation experiments highlighted the importance of Arg-187 and Asp-222 as critical binding sites for both Coa and sinigrin. In vivo studies demonstrated that the combination of sinigrin with oxacillin exhibited greater antibacterial efficacy than oxacillin alone in the treatment of S. aureus-induced pneumonia in mice. Furthermore, sinigrin was shown to reduce bacterial counts and inflammatory cytokine levels in the lung tissues of S. aureus-infected mice. In summary, sinigrin was shown to directly target Coa, resulting in the attenuation of S. aureus virulence, which suggests the potential of sinigrin as an adjuvant for future antimicrobial therapies.

Antibacterial and anti-biofilm activities of antibiotic-free phosphatidylglycerol/docosahexaenoic acid lamellar and non-lamellar liquid crystalline nanoparticles

Infectious diseases, particularly those associated with biofilms, are challenging to treat due to an increased tolerance to commonly used antibiotics. This underscores the urgent need for innovative antimicrobial strategies. Here, we present an alternative simple-by-design approach focusing on the development of biocompatible and antibiotic-free nanocarriers from docosahexaenoic acid (DHA) that has the potential to combat microbial infections and phosphatidylglycerol (DOPG), which is attractive for use as a biocompatible prominent amphiphilic component of Gram-positive bacterial cell membranes. We assessed the anti-bacterial and anti-biofilm activities of these nanoformulations (hexosomes and vesicles) against S. aureus and S. epidermidis, which are the most common causes of infections on catheters and medical devices by different methods (including resazurin assay, time-kill assay, and confocal laser scanning microscopy on an in vitro catheter biofilm model). In a DHA-concentration-dependent manner, these nano-self-assemblies demonstrated strong anti-bacterial and anti-biofilm activities, particularly against S. aureus. A five-fold reduction of the planktonic and a four-fold reduction of biofilm populations of S. aureus were observed after treatment with hexosomes. The nanoparticles had a bacteriostatic effect against S. epidermidis planktonic cells but no anti-biofilm activity was detected. We discuss the findings in terms of nanoparticle-bacterial cell interactions, plausible alterations in the phospholipid membrane composition, and potential penetration of DHA into these membranes, leading to changes in their structural and biophysical properties. The implications for the future development of biocompatible nanocarriers for the delivery of DHA alone or in combination with other anti-bacterial agents are discussed, as novel treatment strategies of Gram-positive infections, including biofilm-associated infections.

Microbial mysteries: Staphylococcus aureus and the enigma of carcinogenesis

Staphylococcus aureus, a common human pathogen, has long been the focus of scientific investigation due to its association with various infections. However, recent research has unveiled a tantalizing enigma surrounding this bacterium and its potential involvement in carcinogenesis. Chronic S. aureus infections have been linked to an elevated risk of certain cancers, including skin cancer and oral cancer. This review explores the current state of knowledge regarding this connection, examining epidemiological evidence, pathogenic mechanisms, and biological interactions that suggest a correlation. Although initial studies point to a possible link, the precise mechanisms through which S. aureus may contribute to cancer development remain elusive. Emerging evidence suggests that the chronic inflammation induced by persistent S. aureus infections may create a tumor-promoting environment. This inflammation can lead to DNA damage, disrupt cellular signaling pathways, and generate an immunosuppressive microenvironment conducive to cancer progression. Additionally, S. aureus produces a variety of toxins and metabolites that can directly interact with host cells, potentially inducing oncogenic transformations. Despite these insights, significant gaps remain in our understanding of the exact biological processes involved. This review emphasizes the urgent need for more comprehensive research to clarify these microbiological mysteries. Understanding the role of S. aureus in cancer development could lead to novel strategies for cancer prevention and treatment, potentially transforming therapeutic approaches.

Staphylococcus aureus major cell division protein FtsZ assembly is inhibited by silibinin, a natural flavonolignan that also blocked bacterial growth and biofilm formation

The bacterial cell division protein FtsZ has been considered a potential therapeutic target due to its rapid treadmilling that induces cellular wall construction in bacteria. The current study discovered a novel antimicrobial compound, silibinin, a natural flavonolignan and its impact on the recombinant S. aureus FtsZ (SaFtsZ). Silibinin inhibited S. aureus Newman growth in a dose-dependent manner. The IC50 and MIC values for silibinin were 75 μM and 200 μM, respectively. It had no cytotoxicity against HEK293 cells in vitro. Silibinin also enlarged the bacterial cell morphology by ∼40 folds and showed antibiofilm property. It perturbed the S. aureus membrane potential both at IC50 conc. and at MIC conc. Further, it inhibited both the polymerization and GTPase activity of SaFtsZ. It did not inhibit tubulin assembly, a eukaryotic FtsZ homolog. A fluorescence quenching study yielded the Kd value for SaFtsZ-Silibinin interaction and binding stoichiometry 0.857 ± 0.188 μM and 1:1, respectively. Both in silico study and competition assay indicated that silibinin binds at the GTP binding site on SaFtsZ. The Ki value for the silibinin-mediated inhibition of SaFtsZ was 8.8 μM. Therefore, these findings have comprehensively shown the antimicrobial behavior of silibinin on S. aureus Newman cells targeting SaFtsZ.

Photodynamic therapy on mRNA levels in bacteria

Antimicrobial photodynamic therapy (aPDT) has shown efficacy in inactivating different bacterial species by photosensitizer-induced free radical production. Despite aPDT is considered unable to cause resistant strains, enzymatic pathways for detoxification of reactive oxygen species and transmembrane photosensitizer efflux systems could cause resistance to aPDT. Resistance mechanisms can be evaluated by measurement of mRNA from by quantitative reverse transcription polymerase chain reaction (RT-qPCR). Thus, the aim of this study was to access the mRNA level data obtained by RT-qPCR in bacterial cells submitted to photodynamic therapy. Studies performed on mRNA levels in bacteria after PDT were assessed on MEDLINE/Pubmed. The mRNA levels from genes related to various functions have been successfully evaluated in both Gram-positive and -negative bacteria after aPDT by RT-qPCR. Such an approach has improved the understanding of aPDT-induced effects, and reinforced the effectiveness of aPDT on bacteria, which can cause infections in different human tissues.

Synthesis, Characterization and Application of Advanced Antimicrobial Electrospun Polymers

The aim of this work was to synthesize, characterize and apply advanced antimicrobial biocompatible electrospun polymers suitable for medical implants for surgical repairs. Injuries to the musculoskeletal system often necessitate surgical repair, but current treatments can still lead to high failure rates, such as 40% for the repair of rotator cuff tears. Therefore, there is an urgent need for the development of new biocompatible materials that can effectively support the repair of damaged tissues. Additionally, infections acquired during hospitalization, particularly those caused by antibiotic-resistant bacteria, result in more fatalities than AIDS, tuberculosis, and viral hepatitis combined. This underscores the critical necessity for the advancement of antimicrobial implants with specialized coatings capable of combating Methicillin-resistant Staphylococcus aureus (MRSA) and Methicillin-sensitive Staphylococcus aureus (MSSA), two strains notoriously known for their antibiotic resistance. Therefore, we developed an antimicrobial coating incorporating nanoparticle mixtures using the sol-gel process and applied it to electrospun polycaprolactone (PCL) filaments, followed by thorough characterization by using spectroscopic (FTIR, Raman, NMR) microscopic (SEM and SEM-EDX), and tensile test. The results have shown that the integration of electro-spinning technology for yarn production, coupled with surface modification techniques, holds significant potential for creating antimicrobial materials suitable for medical implants for surgical repairs.

In vitro studies support clinical trials showing platelet-rich fibrin-mediated local delivery of antibiotics improves outcomes in impacted mandibular third molar surgery

Our previous clinical observations showed that platelet rich fibrin (PRF) can be used to deliver antibiotics to attenuate postoperative complications after unilaterally impacted mandibular third molar surgery (IMTMS). In order to begin understanding the mechanism involved in the beneficial in vivo effects of PRF-mediated delivery of antibiotics, in vitro studies were performed, which showed that PRF preparations containing amoxicillin/clavulanic acid or clindamycin significantly inhibited the growth of S. aureus bacteria. In our previous study, comparisons were made between control and treated groups. However, since variations among individual patients could possibly affect the results, the current study included patients with bilaterally symmetric impacted mandibular third molars, allowing us to compare control and antibiotic treatment within each patient. The effects of PRF preparations containing amoxicillin/clavulanic acid or clindamycin on IMTMS was tested in 60 clinical cases. Antibiotic-injected PRF treatment after bilaterally IMTMS resulted in significantly reduced pain, less use of analgesics, and reduced swelling and trismus compared to the control group (PRF without antibiotics) confirming our previous results after unilaterally IMTMS. The in vitro results support the hypothesis that in vivo delivery of antibiotics using PRF produces therapeutic effects after IMTMS by attenuating bacterial infection and inflammation.

Assessment In vitro and In silico of the Activity of Thiadiazines as NorA Efflux Pump Inhibitors

Antimicrobials fight microorganisms, preventing and treating infectious diseases. However, antimicrobial resistance (AMR) is a growing concern due to the inappropriate and excessive use of these drugs. Several mechanisms can lead to resistance, including efflux pumps such as the NorA pump in Staphylococcus aureus, which reduces the effectiveness of fluoroquinolones. Thiadiazines are heterocyclic compounds whose chemical structure resembles that of cephalosporins. Therefore, these compounds and their derivatives have been studied for their potential in combating increased bacterial resistance. To analyze this hypothesis, direct activity assays, antibiotic action-modifying activity, fluorescence assays to evaluate the retention of ethidium bromide inside bacteria, and molecular docking were carried out. These experiments involved serial dilutions in microplates against Staphylococcus aureus strain 1199B under the influence of six thiadiazine derivatives (IJ10, IJ11, IJ21, IJ22, IJ23, and IJ25). The tests revealed that, despite not showing effective direct activity, some thiadiazine derivatives (IJ11, IJ21, and IJ22) inhibited the function of the bromide pump both in microdilution tests and in fluorescence and docking assays. Particularly, the IJ11 compound stood out for its activity similar to efflux inhibitors, as well as its inhibition of the norfloxacin pump of this bacterium. Among the results of this study, it deserves to be highlighted for anchoring future experiments, as it represents the first investigation of this group of thiadiazine derivatives against the NorA pump.

Biological Evaluation of d-[18F]Fluoroalanine and d-[18F]Fluoroalanine-d3 as Positron Emission Tomography Imaging Tracers for Bacterial Infection

d-Amino acids such as d-alanine are substrates for bacterial peptidoglycan biosynthesis and are selectively taken up by bacteria and not mammalian cells. Consequently, d-amino acid metabolism is an attractive target for antibiotic discovery and the development of bacteria-specific imaging agents. d-Fluoroalanine and the deuterium-labeled analogue fludalanine (MK641) were originally explored as antibiotics by Merck but failed in clinical trials due to unaccepted toxicity. Herein, we synthesized a fluorine-18 labeled d-fluoroalanine, d-3-[18F]fluoroalanine (d-[18F]FAla), and its deuterated analogue, d-3-[18F]fluoroalanine-d3 (d-[18F]FAla-d3), and evaluated their capability to image bacterial infection. Both d-[18F]FAla and d-[18F]FAla-d3 can accumulate up to 0.64-0.78% ID/cc in the infectious area at 15 min postinjection. Despite the reduction of in vivo defluorination not being observed for deuterated 18F-labeled d-fluoroalanine, these radiolabeled d-alanine analogues were able to differentiate bacterial infection from sterile inflammation in a soft-tissue model of S. aureus infection.

Signal peptidase SpsB coordinates staphylococcal cell cycle, surface protein septal trafficking and LTA synthesis

Many cell wall anchored surface proteins of Gram-positive bacteria harbor a highly conserved YSIRK/G-S signal peptide (SPYSIRK+), which deposits surface protein precursors at the cell division septum where they are subsequently anchored to septal peptidoglycan. Previously we identified that LtaS-mediated lipoteichoic acid (LTA) synthesis regulates septal trafficking of YSIRK+ proteins in S. aureus. Interestingly, both LtaS and SPYSIRK+ are cleaved by the signal peptidase SpsB, but the biological implications remain unclear. Here we show that SpsB is required for cleaving SPSpA(YSIRK+) of staphylococcal surface protein A (SpA). Depletion of spsB not only diminished SPSpA processing but also abolished SpA septal localization. The mis-localization is attributed to the cleavage activity of SpsB, as an A37P mutation of SPSpA that disrupted SpsB cleavage also abrogated SpA septal localization. Strikingly, depletion of spsB led to aberrant cell morphology, cell cycle arrest and daughter cell separation defects. Localization studies showed that SpsB predominantly localized at the septum of dividing staphylococcal cells. Finally, we show that SpsB spatially regulates LtaS as spsB depletion enriched LtaS at the septum. Collectively, the data suggest a new dual-mechanism model mediated by SpsB: the abundant YSIRK+ proteins are efficiently processed by septal localized SpsB; SpsB cleaves LtaS at the septum, which spatially regulates LtaS activity contributing to YSIRK+ proteins septal trafficking. The study identifies SpsB as a novel and key regulator orchestrating protein secretion, cell cycle and cell envelope biogenesis.

Anti-Biofilm Effect of Hybrid Nanocomposite Functionalized with Erythrosine B on Staphylococcus aureus Due to Photodynamic Inactivation

Resistant biofilms formed by Staphylococcus aureus on medical devices pose a constant medical threat. A promising alternative to tackle this problem is photodynamic inactivation (PDI). This study focuses on a polyurethane (PU) material with an antimicrobial surface consisting of a composite based on silicate, polycation, and erythrosine B (EryB). The composite was characterized using X-ray diffraction and spectroscopy methods. Anti-biofilm effectiveness was determined after PDI by calculation of CFU mL-1. The liquid PU precursors penetrated a thin silicate film resulting in effective binding of the PU/silicate composite and the PU bulk phases. The incorporation of EryB into the composite matrix did not significantly alter the spectral properties or photoactivity of the dye. A green LED lamp and laser were used for PDI, while irradiation was performed for different periods. Preliminary experiments with EryB solutions on planktonic cells and biofilms optimized the conditions for PDI on the nanocomposite materials. Significant eradication of S. aureus biofilm on the composite surface was achieved by irradiation with an LED lamp and laser for 1.5 h and 10 min, respectively, resulting in a 10,000-fold reduction in biofilm growth. These results demonstrate potential for the development of antimicrobial polymer surfaces for modification of medical materials and devices.

Mechanistic insights and in vivo efficacy of thiosemicarbazones against methicillin-resistant Staphylococcus aureus

Staphylococcus aureus poses a significant threat in both community and hospital settings due to its infective and pathogenic nature combined with its ability to resist the action of chemotherapeutic agents. Methicillin-resistant S. aureus (MRSA) poses a critical challenge. Metal-chelating thiosemicarbazones (TSCs) have shown promise in combating MRSA and while previous studies hinted at the antimicrobial potential of TSCs, their mechanisms of action against MRSA are still under investigation. We screened a chemical library for anti-staphylococcal compounds and identified a potent molecule named R91 that contained the NNSN structural motif found within TSCs. We identified that R91 and several structural analogs exhibited antimicrobial activity against numerous S. aureus isolates as well as other Gram-positive bacteria. RNAseq analysis revealed that R91 induces copper and oxidative stress responses. Checkerboard assays demonstrated synergy of R91 with copper, nickel, and zinc. Mutation of the SrrAB two-component regulatory system sensitizes S. aureus to R91 killing, further linking the oxidative stress response to R91 resistance. Moreover, R91 was found to induce hydrogen peroxide production, which contributed to its antimicrobial activity. Remarkably, no mutants with elevated R91 resistance were identified, despite extensive attempts. We further demonstrate that R91 can be used to effectively treat an intracellular reservoir of S. aureus in cell culture and can reduce bacterial burdens in a murine skin infection model. Combined, these data position R91 as a potent TSC effective against MRSA and other Gram-positive bacteria, with implications for future therapeutic development.

Respiratory tract infections: an update on the complexity of bacterial diversity, therapeutic interventions and breakthroughs

Respiratory tract infections (RTIs) have a significant impact on global health, especially among children and the elderly. The key bacterial pathogens Streptococcus pneumoniae, Haemophilus influenzae, Klebsiella pneumoniae, Staphylococcus aureus and non-fermenting Gram Negative bacteria such as Acinetobacter baumannii and Pseudomonas aeruginosa are most commonly associated with RTIs. These bacterial pathogens have evolved a diverse array of resistance mechanisms through horizontal gene transfer, often mediated by mobile genetic elements and environmental acquisition. Treatment failures are primarily due to antimicrobial resistance and inadequate bacterial engagement, which necessitates the development of alternative treatment strategies. To overcome this, our review mainly focuses on different virulence mechanisms and their resulting pathogenicity, highlighting different therapeutic interventions to combat resistance. To prevent the antimicrobial resistance crisis, we also focused on leveraging the application of artificial intelligence and machine learning to manage RTIs. Integrative approaches combining mechanistic insights are crucial for addressing the global challenge of antimicrobial resistance in respiratory infections.

Acetyl-proteome profiling revealed the role of lysine acetylation in erythromycin resistance of Staphylococcus aureus

Background

Staphylococcus aureus (S. aureus), a prevalent human pathogen known for its propensity to cause severe infections, has exhibited a growing resistance to antibiotics. Lysine acetylation (Kac) is a dynamic and reversible protein post-translational modification (PTM), played important roles in various physiological functions. Recent studies have shed light on the involvement of Kac modification in bacterial antibiotic resistance. However, the precise relationship between Kac modification and antibiotic resistance in S. aureus remains inadequately comprehended.

Methods

We compared the differential expression of acetylated proteins between erythromycin-resistant (Ery-R) and erythromycin-susceptible (Ery-S) strains of S. aureus by 4D label-free quantitative proteomics technology. Additionally, we employed motif analysis, functional annotation and PPI network to investigate the acetylome landscape and heterogeneity of S. aureus. Furthermore, polysome profiling experiments were performed to assess the translational status of ribosome.

Results

6791 Kac sites were identified on 1808 proteins in S. aureus, among which 1907 sites in 483 proteins were quantified. A total of 548 Kac sites on 316 acetylated proteins were differentially expressed by erythromycin pressure. The differentially acetylated proteins were primarily enriched in ribosome assembly, glycolysis and lysine biosynthesis. Bioinformatic analyses implied that Kac modification of ribosomal proteins may play an important role in erythromycin resistance of S. aureus. Western bolt and polysome profiling experiments indicated that the increased Kac levels of ribosomal proteins in the resistant strain may partially offset the inhibitory effect of erythromycin on ribosome function.

Conclusions

Our findings confirm that Kac modification is related to erythromycin resistance in S. aureus and emphasize the potential roles of ribosomal proteins. These results expand our current knowledge of antibiotic resistance mechanisms, potentially guiding future research on PTM-mediated antibiotic resistance.