Staphylococcus aureus: the current state of disease, pathophysiology and strategies for prevention

Volatiles extracted from Melaleuca Rugulosa (Link) Craven leaves: comparative profiling, bioactivity screening, and metabolomic analysis

BACKGROUND

Melaleuca species (family Myrtaceae) are characterized by their wide-ranging applications as antimicrobials and in skin-related conditions. Herein, we estimated the volatile profile and biological significance of M. rugulosa (Link) leaves for the first time supported by a dereplication protocol.

MATERIALS AND METHODS

Volatile components were extracted using hydrodistillation (HD), supercritical fluid (SF), and headspace (HS) techniques and identified using GC/MS. The variations among the three extracts were assessed using principal component analysis and orthogonal partial least square discriminant analysis (OPLS-DA). The extracted volatiles were tested for radical scavenging activity, anti-aging, and anti-hyperpigmentation potential. Finally, disc diffusion and broth microdilution assays were implemented to explore the antibacterial capacity against Streptococcus pyogenes, Staphylococcus aureus, Clostridium perfringens, and Pseudomonas aeruginosa.

RESULTS

The yield of the SF technique (0.8%) was three times higher than HD. GC/MS analysis revealed that the oxygenated compounds are the most proponents in the three extracts being 95.93% (HD), 80.94% (HS), and 48.4% (SF). Moreover, eucalyptol (1,8-cineol) represents the major component in the HD-EO (89.60%) and HS (73.13%) volatiles, while dl-α-tocopherol (16.27%) and α-terpineol (11.89%) represent the highest percentage in SF extract. Regarding the bioactivity profile, the HD-EO and SF-extract showed antioxidant potential in terms of oxygen radical absorbance capacity, and β- carotene assays, while exerting weak activity towards DPPH. In addition, they displayed potent anti-elastase and moderate anti-collagenase activities. The HD-EO exhibited potent anti-tyrosinase activity, while the SF extract showed a moderate level compared to tested controls. OPLS-DA and dereplication studies predicted that the selective antibacterial activity of HD-EO to S. aureus was related to eucalyptol, while SF extract to C. perfringens was related to α-tocopherol.

CONCLUSIONS

M. rugulosa leaves are considered a vital source of bioactive volatile components that are promoted for controlling skin aging and infection. However, further safety and clinical studies are recommended.

Chemical analysis, antibacterial and anti-inflammatory effect of Achillea fragrantissima essential oil growing wild in Egypt

BACKGROUND

Achillea fragrantissima (F. Asteraceae) is traditionally used to treat skin infections and inflammation. The present work intended to prepare essential oils (EOs) from A. fragrantissima aerial parts growing widely in Egypt and investigate its antibacterial activity against skin-related pathogens and in vitro cell-based anti-inflammatory activity.

METHODS

EOs of the fresh aerial parts were extracted by hydrodistillation (HD), microwave-assisted hydrodistillation (MAHD), and head-space (HS), while those of the dried ones were prepared by supercritical fluid (SF). The result EOs were analyzed using GC/MS. The antibacterial activity was evaluated alongside Pseudomonas aeruginosa ATCC 9027, Escherichia coli ATCC 8739, Staphylococcus aureus ATCC 25923, Streptococcus pyogenes ATCC 12344, Clostridium perfringens ATCC 13124 by agar diffusion, microwell dilution, and biofilm formation tests. The anti-inflammatory activity was evaluated by measuring tumor necrosis factor-alpha (TNF-α), interleukin 2 (IL-2), and 6 (IL-6) in lipopolysaccharides (LPS)- stimulated RAW 264.7 cells using ELISA assays in addition, expression of nitric oxide synthase (iNOS) was measured via western blot.

RESULTS

The SF method gave the highest EO yield (1.50 mL v/w). Oxygenated components constituted the highest percentage in the four methods, 84.14, 79.21, 73.29 and 33.57% in the HS, HD, MAHD, and SF, respectively. Moreover, variation in the amount of identified compounds was apparent; in HS EO α-thujone (29.37%), artemisia ketone (19.59%), and santolina alcohol (14.66%) are major components, while α-thujone (20.38%) and piperatone (12.09%) were significant in HD. Moreover, ( +)-spathulenol (12.22%) and piperatone (10.48%) were significant in MAHD, while piperatone (14.83%) and β-sitosterol (11.07%) were significant in SF EO. HD, MAHD, and SF EOs exhibited susceptibility against P. aeruginosa (IZ = 9-14 mm), E. coli (11-13 mm), and C. perfringens (IZ = 10-14 mm) in agar diffusion assay. MAHD EOs demonstrated potent growth inhibition (MICs = 0.25-2 mg/mL), followed by HD EOs (MICs = 13-52 mg/mL) to all tested microorganisms in well microdilution assay. Also, they exert MBC values equal to or higher than the MICs. Furthermore, SF EOs inhibited the biofilm formation of all tested microorganisms by 65.12-80.84%. Specifically, MAHD and HD EOs efficiently suppress the biofilm of S. pyogenes (77.87%) and P. aeruginosa (60. 29%), respectively. Ultimately, HD and SF EOs showed anti-inflammatory activity by suppressing the TNF-α, IL-2, and IL-6 release and iNOS expression in LPS-stimulated RAW 264.7 macrophages.

CONCLUSION

A. fragrantissima EO is rich in oxygenated volatile compounds with antibacterial and anti-inflammatory activities. It is encouraged as a bioactive agent for adjusting skin infections, though additional studies are essential for their safety in clinical settings.

Cross-sectional Hospital-based Investigation on Clinical Characteristics of Pediatric Staphylococcus aureus Isolates in a Beijing Hospital from 2013 to 2022

Background

Staphylococcus aureus (S. aureus) was a prevalent pathogenic bacterium among children. Due to the extensive use of antibiotics, the sensitivity of S. aureus to these drugs has gradually declined. Since the 1960s, methicillin-resistant Staphylococcus aureus (MRSA) has emerged and spread worldwide, becoming a primary cause of both healthcare-associated (HA) and community-acquired (CA) infections. This retrospective study aimed to highlight the significance of S. aureus among bacteria isolated from children in Beijing, China, and to elucidate its antimicrobial resistance patterns.

Methods

Data on all S. aureus infections from 2013 to 2022 were collected from the microbiology department of Beijing Children's Hospital. Only the first isolate from the same kind of specimen was analyzed. Antimicrobial susceptibility tests were carried out by Vitek 2 automated system (bio Mérieux, France) or Kirby-Bauer disc diffusion method, according to the guidelines recommended by the Clinical and Laboratory Standards Institute (CLSI).

Results

During the decade-long research period, a total of 47,062 bacterial isolates were isolated from 433,081 submitted specimens, with 6477 of these isolates identified as S. aureus. The majority of patients with S. aureus infections belonged to the age group of infants under one-year-old, accounting for 37.9% of cases. S. aureus isolates were predominantly found in the Pneumology Department, and the most common source of these isolates was lower respiratory tract specimens, comprising 34.3% of the total. The resistance rates of S. aureus to penicillin and erythromycin were notably high, at 89.5% and 73.8%, respectively. In contrast, the resistance rates to linezolid, vancomycin, rifampicin, and moxifloxacin were remarkably low, at 0.0%, 0.0%, 1.3%, and 3.9%, respectively. The detection rate of MRSA was 27.8%. MRSA isolates were predominantly found in the newborn group, ICU, and sterile body fluids.

Conclusion

In our study, the most prevalent specimen type was derived from the lower respiratory tract, whereas the highest positive rate was observed in ear secretions. These findings underscored the pressing necessity for ongoing antimicrobial resistance (AMR) surveillance and the revision of treatment guidelines, particularly given the elevated detection of MRSA in ICU wards, sterile body fluids, and the neonatal age group. MRSA exhibited significant resistance to all β-lactam antibiotics, erythromycin, and ciprofloxacin. Therefore, future research endeavors should prioritize examining specific antimicrobial resistance populations and potential intervention strategies, as these were vital in mitigating the dissemination of antimicrobial-resistant isolates.

Crotalaria madurensis flavonol glycosides' antibacterial activity against Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) infections are prevalent in hospitals and often lead to significant health complications. This study aimed to explore the chemical composition of the aerial part of Crotalaria madurensis and evaluate its antioxidant and antibacterial properties. The impact of gamma irradiation on the antibacterial properties of the plant extract and metabolite 1 against MRSA was also examined. Fourier-transform infrared (FTIR) analysis was conducted on the filtrates of untreated MRSA and MRSA treated with the plant extract and metabolite 1. Four flavonol glycosides were identified as gossypetin 8-methoxy, 3-O-β-D-xylopyranoside (metabolite 1), gossypetin 8-O-β-D-glucopyranoside (metabolite 2), kaempferol 3-O-β-D-glucpyranoside (Astragalin, metabolite 3), and herbacetin 7-methoxy-3-O-β-D-glucopyranoside (metabolite 4). All metabolites exhibited significant antioxidant properties using different assays. The antibacterial efficacy of the extract and metabolite 1, which showed substantial antioxidant properties compared to the other isolated metabolites, was evaluated. Both the plant extract and metabolite 1 significantly reduced the viability and cell count of MRSA at concentrations of 1.0 and 0.5 mg/ml. The antibacterial activity of the plant extract and metabolite 1 was assessed after gamma irradiation at 50 and 100 Gy, which did not significantly affect the antibacterial efficiency. FTIR analysis indicated that the plant extract and metabolite 1 significantly altered the band frequency values, bandwidth, and peak intensity % of the treated MRSA filtrate. Molecular docking studies suggested that metabolite 1 exhibited the highest antioxidant and anti-MRSA activity, with strong binding scores like the ligand, indicating an effective interaction and high affinity between metabolite 1 and the target molecule.

Synthesis and antibacterial activities of heterocyclic ring-fused 20(S)-protopanaxadiol derivatives

Multidrug-resistant (MDR) bacterial infections are becoming a life-threatening issue in public health; therefore, it is urgent to develop novel antibacterial agents for treating infections caused by MDR bacteria. The 20(S)-protopanaxadiol (PPD) derivative 9 was identified as a novel antibacterial hit compound in screening of our small synthetic natural product-like (NPL) library. A series of novel PPD derivatives with heterocyclic rings fused at the C-2 and C-3 positions of the A-ring were synthesized and their antibacterial activities against Staphylococcus aureus (S. aureus) Newman strain and MDR S. aureus strains (USA300, NRS-1, NRS-70, NRS-100, NRS-108, NRS-271, XJ017, and XJ036) were evaluated. Among these compounds, quinoxaline derivative 56 (SH617) exhibited the highest activity with MICs of 0.5-4 μg/mL against the S. aureus Newman strain and the eight MDR S. aureus strains. Its antibacterial activity was comparable to that of the positive control, vancomycin. In the zebrafish, 56 revealed no obvious toxicity even at a high administered dose. In vivo, following a lethal infection induced by USA300 strains in zebrafish, 56 exhibited significantly increased survival rates in a dose-dependent manner.

A review of pathogenic airborne fungi and bacteria: unveiling occurrence, sources, and profound human health implication

Airborne fungi and bacteria have been extensively studied by researchers due to their significant effects on human health. We provided an overview of the distribution and sources of airborne pathogenic microbes, and a detailed description of the detrimental effects that these microorganisms cause to human health in both outdoor and indoor environments. By analyzing the large body of literature published in this field, we offered valuable insights into how airborne microbes influence our well-being. The findings highlight the harmful consequences associated with the exposure to airborne fungi and bacteria in a variety of natural and human-mediated environments. Certain demographic groups, including children and the elderly, immunocompromised individuals, and various categories of workers are particularly exposed and vulnerable to the detrimental effect on health of air microbial pollution. A number of studies performed up to date consistently identified Alternaria, Cladosporium, Penicillium, Aspergillus, and Fusarium as the predominant fungal genera in various indoor and outdoor environments. Among bacteria, Bacillus, Streptococcus, Micrococcus, Enterococcus, and Pseudomonas emerged as the dominant genera in air samples collected from numerous environments. All these findings contributed to expanding our knowledge on airborne microbe distribution, emphasizing the crucial need for further research and increased public awareness. Collectively, these efforts may play a vital role in safeguarding human health in the face of risks posed by airborne microbial contaminants.

Time-calibrated phylogenetic and chromosomal mobilome analyses of Staphylococcus aureus CC398 reveal geographical and host-related evolution

An international collection of Staphylococcus aureus of clonal complex (CC) 398 from diverse hosts spanning all continents and a 30 year-period is studied based on whole-genome sequencing (WGS) data. The collection consists of publicly available genomic data from 2994 strains and 134 recently sequenced Swiss methicillin-resistant S. aureus (MRSA) CC398 strains. A time-calibrated phylogeny reveals the presence of distinct phylogroups present in Asia, North and South America and Europe. European MRSA diverged from methicillin-susceptible S. aureus (MSSA) at the beginning of the 1950s. Two major European phylogroups (EP4 and EP5), which diverged approximately 1974, are the main drivers of MRSA CC398 spread in Europe. Within EP5, an emergent MRSA lineage spreading among the European horse population (EP5-Leq) diverged approximately 1996 from the pig lineage (EP5-Lpg), and also contains human-related strains. EP5-Leq is characterized by staphylococcal cassette chromosome mec (SCCmec) IVa and spa type t011 (CC398-IVa-t011), and EP5-Lpg by CC398-SCCmecVc-t011. The lineage-specific antibiotic resistance and virulence gene patterns are mostly mediated by the acquisition of mobile genetic elements like SCCmec, S. aureus Genomic Islands (SaGIs), prophages and transposons. Different combinations of virulence factors are present on S. aureus pathogenicity islands (SaPIs), and novel antimicrobial resistance gene containing elements are associated with certain lineages expanding in Europe. This WGS-based analysis reveals the actual evolutionary trajectory and epidemiological trend of the international MRSA CC398 population considering host, temporal, geographical and molecular factors. It provides a baseline for global WGS-based One-Health studies of adaptive evolution of MRSA CC398 as well as for local outbreak investigations.

Liposomal Rifabutin-A Promising Antibiotic Repurposing Strategy against Methicillin-Resistant Staphylococcus aureus Infections

Methicillin-resistant Staphylococcus aureus (M RSA) infections, in particular biofilm-organized bacteria, remain a clinical challenge and a serious health problem. Rifabutin (RFB), an antibiotic of the rifamycins class, has shown in previous work excellent anti-staphylococcal activity. Here, we proposed to load RFB in liposomes aiming to promote the accumulation of RFB at infected sites and consequently enhance the therapeutic potency. Two clinical isolates of MRSA, MRSA-C1 and MRSA-C2, were used to test the developed formulations, as well as the positive control, vancomycin (VCM). RFB in free and liposomal forms displayed high antibacterial activity, with similar potency between tested formulations. In MRSA-C1, minimal inhibitory concentrations (MIC) for Free RFB and liposomal RFB were 0.009 and 0.013 μg/mL, respectively. Minimum biofilm inhibitory concentrations able to inhibit 50% biofilm growth (MBIC50) for Free RFB and liposomal RFB against MRSA-C1 were 0.012 and 0.008 μg/mL, respectively. Confocal microscopy studies demonstrated the rapid internalization of unloaded and RFB-loaded liposomes in the bacterial biofilm matrix. In murine models of systemic MRSA-C1 infection, Balb/c mice were treated with RFB formulations and VCM at 20 and 40 mg/kg of body weight, respectively. The in vivo results demonstrated a significant reduction in bacterial burden and growth index in major organs of mice treated with RFB formulations, as compared to Control and VCM (positive control) groups. Furthermore, the VCM therapeutic dose was two fold higher than the one used for RFB formulations, reinforcing the therapeutic potency of the proposed strategy. In addition, RFB formulations were the only formulations associated with 100% survival. Globally, this study emphasizes the potential of RFB nanoformulations as an effective and safe approach against MRSA infections.

Multifunctional fucoidan-loaded Zn-MOF-encapsulated microneedles for MRSA-infected wound healing

Infected wound healing remains a challenging task in clinical practice due to several factors: (I) drug-resistant infections caused by various pathogens, (II) persistent inflammation that hinders tissue regeneration and (III) the ability of pathogens to persist intracellularly and evade antibiotic treatment. Microneedle patches (MNs), recognized for their effecacious and painless subcutaneous drug delivery, could greatly enhance wound healing if integrated with antibacterial functionality and tissue regenerative potential. A multifunctional agent with subcellular targeting capability and contained novel antibacterial components, upon loading onto MNs, could yield excellent therapeutic effects on wound infections. In this study, we sythesised a zeolitic imidazolate framework-8 nanoparticles (ZIF-8 NPs) loaded with low molecular weight fucoidan (Fu) and further coating by hyaluronic acid (HA), obtained a multifunctional HAZ@Fu NPs, which could hinders Methicillin-resistant Staphylococcus aureus (MRSA) growth and promotes M2 polarization in macrophages. We mixed HAZ@Fu NPs with photocrosslinked gelatin methacryloyl (GelMA) and loaded it into the tips of the MNs (HAZ@Fu MNs), administered to mice model with MRSA-infected full-thickness cutaneous wounds. MNs are able to penetrate the skin barrier, delivering HAZ@Fu NPs into the dermal layer. Since cells within infected tissues extensively express the HA receptor CD44, we also confirmed the HA endows the nanoparticles with the ability to target MRSA in subcellular level. In vitro and in vivo murine studies have demonstrated that MNs are capable of delivering HAZ@Fu NPs deep into the dermal layers. And facilitated by the HA coating, HAZ@Fu NPs could target MRSA surviving at the subcellular level. The effective components, such as zinc ions, Fu, and hyaluronic acid could sustainably released, which contributes to antibacterial activity, mitigates inflammation, promotes epithelial regeneration and fosters neovascularization. Through the RNA sequencing of macrophages post co-culture with HAZ@Fu, the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis reveals that the biological functionalities associated with wound healing could potentially be facilitated through the PI3K-Akt pathway. The results indicate that the synergistic application of HAZ@Fu NPs with biodegradable MNs may serve as a significant adjunct in the treatment of infected wounds. The intricate mechanisms driving its biological effects merit further investigation.

Biochemical evaluation and ligand binding studies on glycerophosphodiester phosphodiesterase from Staphylococcus aureus using STD-NMR spectroscopy and molecular docking analysis

Glycerophosphodiester phosphodiesterase (GDPD) is a highly conserved enzyme in both prokaryotic and eukaryotic organisms. It catalyses the hydrolysis of various glycerophosphodiesters into glycerol-3-phosphate and corresponding alcohols, which serve as building blocks in several biosynthetic pathways. This enzyme is a well-known virulence factor in many pathogenic bacteria, including Staphylococcus aureus, and is thus considered a potential drug target. In this study, competent E. coli BL21(DE3)pLysS expression cells were used to express the GDPD enzyme from vancomycin-resistant Staphylococcus aureus (VRSA), which was then purified using size exclusion and anion exchange chromatography. The hydrolytic activity of GDPD was evaluated on the non-physiological substrate bis(p-nitrophenyl) phosphate (BpNPP), which indicated functional activity of the enzyme. 79 drugs were evaluated for their inhibitory potential against GDPD enzyme by the colorimetric assay. Out of 79 drugs, 13 drugs, including tenofovir (1), adenosine (2), clioquinol (11), bromazepam (12), lamotrigine (13), sulfadiazine (14), azathioprine (15), nicotine (16), sitagliptin PO4 (17), doxofylline (18), clindamycin phosphate (19), gentamycin sulphate (20), and ceftriaxone sodium (21) revealed varying degrees of inhibitory potential with IC50 values in the range of 400 ± 0.007-951 ± 0.016 µM. All drugs were also evaluated for their binding interactions with the target enzyme by saturation transfer difference (STD-NMR) spectroscopy. 10 drugs demonstrated STD interactions and hence, showed binding affinity with the enzyme. Exceptionally, tenofovir (1) was identified to be a better inhibitor with an IC50 value of 400 ± 0.007 µM, as compared to the standard EDTA (ethylenediaminetetraacetic acid) (IC50 = 470 ± 0.008 µM). Moreover, molecular docking studies have identified key interactions of the ligand (tenofovir) with the binding site residues of the enzyme.

Interactions of plumbagin with five common antibiotics against Staphylococcus aureus in vitro

Staphylococcus aureus is the main culprit, causing a variety of severe clinical infections. At the same time, clinics are also facing the severe situation of antibiotic resistance. Therefore, effective strategies to address this problem may include expanding the antimicrobial spectrum by exploring alternative sources of drugs or delaying the development of antibiotic resistance through combination therapy so that existing antibiotics can continue to be used. Plumbagin (PLU) is a phytochemical that exhibits antibacterial activity. In the present study, we investigated the in vitro antibacterial activity of PLU. We selected five antibiotics with different mechanisms and inhibitory activities against S. aureus to explore their interaction with the combination of PLU. The interaction of combinations was evaluated by the Bliss independent model and visualized through response surface analysis. PLU exhibited potent antibacterial activity, with half maximal inhibitory concentration (IC50) and minimum inhibitory concentration (MIC) values against S. aureus of 1.73 μg/mL and 4 μg/mL, respectively. Synergism was observed when PLU was combined with nitrofurantoin (NIT), ciprofloxacin (CPR), mecillinam (MEC), and chloramphenicol (CHL). The indifference of the trimethoprim (TMP)-PLU pairing was demonstrated across the entire dose-response matrix, but significant synergy was observed within a specific dose region. In addition, no antagonistic interactions were indicated. Overall, PLU is not only a promising antimicrobial agent but also has the potential to enhance the growth-inhibitory activity of some antibiotics against S. aureus, and the use of the interaction landscape, along with the dose-response matrix, for analyzing and quantifying combination results represents an improved approach to comprehending antibacterial combinations.

Antimicrobial Resistance Patterns of Staphylococcus Aureus Isolated at a General Hospital in Vietnam Between 2014 and 2021

Purpose

Staphylococcus aureus is a commensal bacteria species that can cause various illnesses, from mild skin infections to severe diseases, such as bacteremia. The distribution and antimicrobial resistance (AMR) pattern of S. aureus varies by population, time, geographic location, and hospital wards. In this study, we elucidated the epidemiology and AMR patterns of S. aureus isolated from a general hospital in Vietnam.

Methods

This was a cross-sectional study. Data on all S. aureus infections from 2014 to 2021 were collected from the Microbiology department of Military Hospital 103, Vietnam. Only the first isolation from each kind of specimen from a particular patient was analyzed using the Cochran-Armitage and chi-square tests.

Results

A total of 1130 individuals were diagnosed as S. aureus infection. Among them, 1087 strains were tested for AMR features. Most patients with S. aureus infection were in the age group of 41-65 years (39.82%). S. aureus isolates were predominant in the surgery wards, and pus specimens were the most common source of isolates (50.62%). S. aureus was most resistant to azithromycin (82.28%), erythromycin (82.82%), and clindamycin (82.32%) and least resistant to teicoplanin (0.0%), tigecycline (0.16%), quinupristin-dalfopristin (0.43%), linezolid (0.62%), and vancomycin (2.92%). Methicillin-resistant S. aureus (MRSA) and multidrug-resistant (MDR) S. aureus were prevalent, accounting for 73.02% and 60.90% of the total strains respectively, and the strains isolated from the intensive care unit (ICU) had the highest percentage of multidrug resistance (77.78%) among the wards.

Conclusion

These findings highlight the urgent need for continuous AMR surveillance and updated treatment guidelines, particularly considering high resistance in MRSA, MDR strains, and ICU isolates. Future research focusing on specific resistant populations and potential intervention strategies is crucial to combat this rising threat.

An insights into emerging trends to control the threats of antimicrobial resistance (AMR): an address to public health risks

Antimicrobial agents are used to treat microbial ailments, but increased use of antibiotics and exposure to infections in healthcare facilities and hospitals as well as the excessive and inappropriate use of antibiotics at the society level lead to the emergence of multidrug-resistant (MDR) bacteria. Antimicrobial resistance (AMR) is considered a public health concern and has rendered the treatment of different infections more challenging. The bacterial strains develop resistance against antimicrobial agents by limiting intracellular drug accumulation (increasing efflux or decreasing influx of antibiotics), modification and inactivation of drugs and its targets, enzymatic inhibition, and biofilm formation. However, the driving factors of AMR include the sociocultural and economic circumstances of a country, the use of falsified and substandard medicines, the use of antibiotics in farm animals, and food processing technologies. These factors make AMR one of the major menaces faced by mankind. In order to promote reciprocal learning, this article summarizes the current AMR situation in Pakistan and how it interacts with the health issues related to the COVID-19 pandemic. The COVID-19 pandemic aids in illuminating the possible long-term impacts of AMR, which are less immediate but not less severe since their measures and effects are equivalent. Impact on other sectors, including the health industry, the economy, and trade are also discussed. We conclude by summarizing the several approaches that could be used to address this issue.

In vitro antibacterial and anti-biofilm potential of an endophytic Schizophyllum commune

The emergence of antibiotic resistance in pathogens is one of the major health concerns facing mankind as different bacterial strains have developed resistance to antibiotics over the period of time due to overuse and misuse of antibiotics. Besides this, ability to form biofilms is another major factor contributing to antibiotic resistance, which has necessitated the need for exploration for novel and effective compounds with ability to inhibit biofilm formation. Endophytic fungi are reported to exhibit antibacterial and anti-biofilm potential and could serve as a potent source of novel antibacterial compounds. Majority of the bioactivities have been reported from fungi belonging to phylum Ascomycota. Endophytic basidiomycetes, inspite of their profound ability to serve as a source of bioactive compounds have not been exploited extensively. In present study, an attempt was made to assess the antibacterial, anti-biofilm and biofilm dispersion potential of an endophytic basidiomycetous fungus Schizophyllum commune procured from the culture collection of our lab. Ethyl acetate extract of S. commune showed good antibacterial activity against Staphylococcus aureus, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica and Vibrio cholerae. Minimum inhibitory concentration and minimum bactericidal concentration of the extract were in the range of 1.25-10 mg/ml against the tested bacterial pathogens. The mode of action was determined to be bactericidal which was further confirmed by time kill studies. Good anti-biofilm activity of S. commune extract was recorded against K. pneumoniae and S. enterica, which was further validated by fluorescence microscopy. The present study highlights the importance of endophytic basidiomycetes as source of therapeutic compounds.

Human monoclonal antibodies against Staphylococcus aureus A protein identified by high-throughput single-cell sequencing of phase I clinical volunteers' B cells

Methicillin-resistant Staphylococcus aureus, poses a significant threat through infections in both community and hospital settings. To address this challenge, we conducted a phase I clinical trial study involving a recombinant Staphylococcus aureus vaccine. Utilizing peripheral blood lymphocytes from 64 subjects, we isolated antigen-specific memory B cells for subsequent single-cell sequencing. Among the 676 identified antigen-binding IgG1+ clones, we selected the top 10 antibody strains for construction within expression vectors. Successful expression and purification of these monoclonal antibodies led to the discovery of a highly expressed human antibody, designated as IgG-6. This antibody specifically targets the pentameric form of the Staphylococcus aureus protein A (SpA5). In vivo assessments revealed that IgG-6 provided prophylactic protection against MRSA252 infection. This study underscores the potential of human antibodies as an innovative strategy against Staphylococcus aureus infections, offering a promising avenue for further research and clinical development.

Antibodies to coagulase of Staphylococcus aureus crossreact to Efb and reveal different binding of shared fibrinogen binding repeats

Staphylococcus aureus pathology is caused by a plethora of virulence factors able to combat multiple host defence mechanisms. Fibrinogen (Fg), a critical component in the host coagulation cascade, plays an important role in the pathogenesis of this bacterium, as it is the target of numerous staphylococcal virulence proteins. Amongst its secreted virulence factors, coagulase (Coa) and Extracellular fibrinogen-binding protein (Efb) share common Fg binding motives and have been described to form a Fg shield around staphylococcal cells, thereby allowing efficient bacterial spreading, phagocytosis escape and evasion of host immune system responses. Targeting these proteins with monoclonal antibodies thus represents a new therapeutic option against S. aureus. To this end, here we report the selection and characterization of fully human, sequence-defined, monoclonal antibodies selected against the C-terminal of coagulase. Given the functional homology between Coa and Efb, we also investigated if the generated antibodies bound the two virulence factors. Thirteen unique antibodies were isolated from naïve antibodies gene libraries by antibody phage display. As anticipated, most of the selected antibodies showed cross-recognition of these two proteins and among them, four were able to block the interaction between Coa/Efb and Fg. Furthermore, our monoclonal antibodies could interact with the two main Fg binding repeats present at the C-terminal of Coa and distinguish them, suggesting the presence of two functionally different Fg-binding epitopes.

CodY: An Essential Transcriptional Regulator Involved in Environmental Stress Tolerance in Foodborne Staphylococcus aureus RMSA24

Staphylococcus aureus (S. aureus), as the main pathogen in milk and dairy products, usually causes intoxication with vomiting and various kinds of inflammation after entering the human body. CodY, an important transcriptional regulator in S. aureus, plays an important role in regulating metabolism, growth, and virulence. However, little is known about the role of CodY on environmental stress tolerance. In this research, we revealed the role of CodY in environmental stress tolerance in foodborne S. aureus RMSA24. codY mutation significantly reduced the tolerance of S. aureus to desiccation and oxidative, salt, and high-temperature stresses. However, S. aureus was more tolerant to low temperature stress due to mutation of codY. We found that the expressions of two important heat shock proteins-GroEL and DanJ-were significantly down-regulated in the mutant codY. This suggests that CodY may indirectly regulate the high- and low-temperature tolerance of S. aureus by regulating the expressions of groEL and danJ. This study reveals a new mechanism of environmental stress tolerance in S. aureus and provides new insights into controlling the contamination and harm caused by S. aureus in the food industry.

Crystal Structure of Staphopain C from Staphylococcus aureus

Staphylococcus aureus is a common opportunistic pathogen of humans and livestock that causes a wide variety of infections. The success of S. aureus as a pathogen depends on the production of an array of virulence factors including cysteine proteases (staphopains)-major secreted proteases of certain strains of the bacterium. Here, we report the three-dimensional structure of staphopain C (ScpA2) of S. aureus, which shows the typical papain-like fold and uncovers a detailed molecular description of the active site. Because the protein is involved in the pathogenesis of a chicken disease, our work provides the foundation for inhibitor design and potential antimicrobial strategies against this pathogen.

A wound-friendly antibacterial hyaluronic acid dressing with on-demand removability for infected wound healing

BACKGROUND

Antibacterial activity and on-demand removability are key characteristics governing the effectiveness of clinic wound dressing. However, the excellent tissue adhesion of new dressings is often overemphasized without a detailed discussion of dressing replacement. Besides, the inherent antibacterial ability of dressings is beneficial for promoting the healing of infected wound. Therefore, we rationally design an injectable antibacterial wound dressing with on-demand removability to accelerate infected wound healing.

METHOD

We design this wound dressing with a simple and feasible method based on the electrostatic self-assembly of hyaluronic acid and ε-polylysine. We investigated the efficacy of this dressing in terms of its microtopography, rheology, self-healing performance, adhesive ability, antimicrobial, hemostatic, on-demand removal properties, and wound healing promotion through various tests.

RESULTS

The prepared dressing possesses injectability, self-healing ability and antibacterial activity, showing NaCl-triggered on-demand dissolution due to the disruption of electrostatic interactions. When used as dressings for healing full-thickness wounds, it could effectively accelerate wound healing by killing bacteria, downregulating inflammation, promoting collagen deposition, enhancing keratinocyte migration and angiogenesis due to its excellent adhesion ability, favorable hemostatic property, and potent antibacterial performance.

CONCLUSION

All results indicate that this is a simple and practical dressing for clinical application. This strategy provides a novel idea for developing on-demand removal dressings with antibacterial and injectable properties.

Antibacterial and anti-biofilm activity of radezolid against Staphylococcus aureus clinical isolates from China

Although the potent antibacterial ability of radezolid against Staphylococcus aureus has been widely reported worldwide, its antibacterial and anti-biofilm activity against the S. aureus clinical isolates from China remains elusive. In this study, the minimum inhibitory concentration (MIC) of radezolid was determined in S. aureus clinical isolates from China using the agar dilution method, and the relationship between radezolid susceptibility and ST distribution was also investigated. The anti-biofilm activity of radezolid against S. aureus was determined by a crystal violet assay and compared with that of linezolid and contezolid. The quantitative proteomics of S. aureus treated with radezolid was analyzed, and the genetic mutations in radezolid-induced resistant S. aureus were determined by whole-genome sequencing. The dynamic changes in transcriptional expression levels of several biofilm-related genes were analyzed by quantitative RT-PCR. Our data showed that radezolid MIC ranged from ≤0.125 to 0.5 mg/L, which was almost 1/4 × MIC of linezolid against S. aureus, indicating the greater antibacterial activity of radezolid than linezolid. The S. aureus clinical isolates with radezolid MICs of 0.5 mg/L were most widely distributed in ST239 of MRSA and ST7 of MSSA. Moreover, the more robust anti-biofilm activity of radezolid with subinhibitory concentrations (1/8 × MIC and 1/16 × MIC) was demonstrated against S. aureus when compared with that of contezolid and linezolid. Genetic mutations were found in glmS, 23S rRNA, and DUF1542 domain-containing protein in radezolid-induced resistant S. aureus selected by in vitro induction of drug exposure. Quantitative proteomic analysis of S. aureus indicated that the global expression of some biofilm-related and virulence-related proteins was downregulated. Quantitative RT-PCR further confirmed that the expressions of some downregulated biofilm-related proteins, including sdrD, carA, sraP, hlgC, sasG, spa, sspP, fnbA, and oatA, were decreased after 12 h and 24 h of exposure to radezolid. Conclusively, radezolid shows robust antibacterial and anti-biofilm activity against S. aureus clinical isolates from China when compared with contezolid and linezolid.

A challenging high-risk surgery for necrotizing pneumonia in a right bilobed lung

BACKGROUND

Necrotizing pneumonia is rare in children and is one of the most serious complications of a lung infection caused by antibiotic failure. We present a 12-year-old leukopenic child with a long-lasting lung infection, presenting as having a lung hydatid cyst, but diagnosing with necrotizing pneumonia in the right bilobed lung. Failure to medical treatment and ongoing leukopenia justified surgical intervention with positive results.

CASE PRESENTATION

The patient was referred to our teaching hospital's pediatric surgery department. He had previously been diagnosed with intestinal tuberculosis (TB) and received anti-TB treatment. On referral to our hospital, the patient was suffering from restlessness, frequent coughing, fever, vomiting, and diarrhea. Following the completion of the clinical work-up, a blood test revealed leukopenia (white blood cell count of 2100/microliter), a normal platelet count, and a lesion in the right lung. Computerized tomography scanning (CT-Scan) image reported a lung hydatid cyst. In the pediatrics ward, a broad-spectrum antibiotics regimen with triple-antibiotic therapy (linezolid, vancomycin, and metronidazole) was instituted and continued for a week with no response, but worsening of the condition. In the pediatric surgery ward, our decision for surgical intervention was due to the failure of medical treatment because of a pulmonary lesion. Our team performed right lung upper lobe anterior segment wedge resection due to necrotizing pneumonia and followed the patient 45 days post-operation with a reasonable result.

CONCLUSION

Living in remote rural areas with low resources and inaccessibility to proper and specialized diagnostic and treatment centers will all contribute to an improper diagnosis and treatment of lung infection. In total, all of these will increase the morbidity and mortality due to lung necrosis in the pediatric population, regardless of their age. In low-resource facilities, high-risk patients can benefit from surgical intervention to control the ongoing infection process.

Oral mucositis and microbial status in acute lymphoblastic leukemia subjects undergoing high-dose chemotherapy

Aim: To assess oral microbial status in patients with acute lymphoblastic leukemia (ALL) undergoing high-dose chemotherapy and to unravel possible associations between nosocomial pathogens and the establishment of chemotherapy-induced oral mucositis (CIOM). Methods: Oral mucosa, saliva, and peripheral blood samples were collected from 46 ALL subjects one day prior to chemotherapy (D0) and 2 weeks after treatment initiation (D14). Clinical intraoral inspection was performed by a single practitioner, with mucositis classification performed according to the WHO oral toxicity scale. Blood components were quantified by automatic flow cytometry, while oral Staphylococcus aureus and Pseudomonas aeruginosa were detected by Polymerase Chain Reaction with species-specific primers. Associations among bacteria and clinical findings were determined by Fisher’s Exact test, longitudinal bacterial changes by paired Macnemar, and correlations among blood parameters and mucositis status or bacteria via Mann-Whitney. Results: S. aureus displayed higher detection rates at D14 (p < 0.05) and was positively associated with mucositis, adoption of a non-solid diet (all p < 0.001), nausea and fever (all p < 0.05). Conversely, P. aeruginosa did not correlate to CIOM clinical parameters. At the systemic standpoint, lower hemoglobin levels associated with CIOM and fever events (all p < 0.01). Conclusion: The study evidences S. aureus as a potential pathogen in ALL-CIOM, reaffirming microbial control as an important preventive measure during high-dose immunosuppressive therapy. The weight of non-white-blood-cell parameters should be validated as novel CIOM biomarkers in prospective research.

Comprehensive Study of Components and Antimicrobial Properties of Essential Oil Extracted from Carum carvi L. Seeds

Carum carvi L. belongs to the Apiaceae family and is widely used as a vegetable, food spice, preservative, and herbal medicine. This study investigated the impact of essential oil extracted from Carum carvi L. seeds (CEO) on methicillin-resistant Staphylococcus aureus (MRSA) and its possible action mechanism. The dominant chemical components of CEO determined by GC-MS were carvone and limonene. It was observed that CEO had a considerable inhibitory effect against the growth of planktonic bacteria and biofilm in MRSA cells. Untargeted metabolomics based on GC-Q-TOF-MS was used to analyze the possible mechanism of the interaction of MRSA with CEO. It was determined that there were 63 different metabolites based on fold change values greater than 1.5 or less than 1.5, p < 0.05, VIP > 1, which demonstrated amino acid metabolism in MRSA was significantly affected by CEO. In conclusion, CEO has a potent antimicrobial property and has promising potential for use in food and drugs.

Amide containing NBTI antibacterials with reduced hERG inhibition, retained antimicrobial activity against gram-positive bacteria and in vivo efficacy

Novel bacterial topoisomerase inhibitors (NBTIs) are new promising antimicrobials for the treatment of multidrug-resistant bacterial infections. In recent years, many new NBTIs have been discovered, however most of them struggle with the same issue - the balance between antibacterial activity and hERG-related toxicity. We started a new campaign by optimizing the previous series of NBTIs, followed by the design and synthesis of a new, amide-containing focused NBTI library to reduce hERG inhibition and maintain antibacterial activity against Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). This optimization strategy yielded the lead compound 12 that exhibits potent antibacterial activity against Gram-positive bacteria, reduced hERG inhibition, no cardiotoxicity in zebrafish model, and a favorable in vivo efficacy in a neutropenic murine thigh infection model of MRSA infection.

A novel gdmH-related gene, ghl, involved in environmental stress tolerance and vancomycin susceptibility in milk-derived Staphylococcus aureus

Staphylococcus aureus is one of the main microorganisms that contaminate dairy products and pickled foods, and has a great impact on economy and human health. GdmH-related proteins, as important functional units widely present in Staphylococcus species, have not been reported in S. aureus so far. In this study, we identified a gdmH-related gene, named ghl. We found that mutation of ghl gene could decrease the tolerance of environmental stresses (heat, desiccation, salt and hydrogen peroxide) of S. aureus and enhanced the capacities of biofilm formation. In addition, the ghl mutant was more sensitive to vancomycin on CAMHB solid plates but more resistant to vancomycin in CAMHB liquid medium compared to wild type RMSA24. These results indicated that ghl is an important factor to respond to environmental stress in foodborne S. aureus. This paper for the first time reported that a GdmH-related protein plays an important role in environmental tolerance, providing a new direction for the follow-up study of GdmH-related proteins, as well as a potential target gene for further research on the tolerance mechanism of Staphylococcus aureus in food processing and the control of biofilm formation.

Breathable, antifreezing, mechanically skin-like hydrogel textile wound dressings with dual antibacterial mechanisms

Hydrogels are emerging as the most promising dressings due to their excellent biocompatibility, extracellular matrix mimicking structure, and drug loading ability. However, existing hydrogel dressings exhibit limited breathability, poor environmental adaptability, potential drug resistance, and limited drug options, which extremely restrict their therapeutic effect and working scenarios. Here, the current research introduces the first paradigm of hydrogel textile dressings based on novel gelatin glycerin hydrogel (glyhydrogel) fibers fabricated by the Hofmeister effect based wet spinning. Benefiting from the unique knitted structure, the textile dressing features excellent breathability (1800 times that of the commercially available 3 M dressing) and stretchability (535.51 ± 38.66%). Furthermore, the glyhydrogel textile dressing can also withstand the extreme temperature of −80 °C, showing the potential for application in subzero environments. Moreover, the introduction of glycerin endows the textile dressing with remarkable antibacterial property and expands the selection of loaded drugs (e.g., clindamycin). The prepared glyhydrogel textile dressing shows an excellent infected wound healing effect with a complete rat skin closure within 14 days. All these functions have not been achievable by traditional hydrogel dressings and provide a new approach for the development of hydrogel dressings.

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A brand-new dressing, hydrogel textile, has been fabricated for the first time with unprecedented breathability.

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An innovative preparation process for hydrogel fiber has been proposed for the first time.

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More outstanding glyhydrogel textile dressing has been created to show extremely low-temperature resistance.

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Dual mechanisms of antibiotic-free glycerin and lipophilic antibiotics provide a powerful antibacterial treatment.

Phage transcription activator RinA regulates Staphylococcus aureus virulence by governing sarA expression

BACKGROUND

Staphylococcus aureus is a major human pathogen, that can lead to various community- and hospital-acquired infections. RinA is a transcription activator of S. aureus phage φ 11 involved in phage packaging and virulence gene transfer. However, little is known about the molecular mechanism of RinA in the regulation of virulence.

OBJECTIVE

We aimed to explore a novel contribution of RinA in the regulation of virulence and provide a new drug target in the treatment of S. aureus infections.

METHODS

The specific functions of RinA in S. aureus were analyzed by the methods of growth curve, real-time quantitative PCR (RT-qPCR), subcellular localization, electrophoretic mobility shift assay (EMSA), infection model of Galleria mellonella larvae and the mouse subcutaneous abscess model.

RESULTS

In this study, we demonstrated that RinA is a protein evenly distributed in the cytoplasm of S. aureus, and its deletion could cause the growth defects. RT-qPCR and EMSA determined that rinA could negatively regulate the expression of sarA by directly binding to its promoter, and vice versa. The Galleria mellonella larvae infection and mouse subcutaneous abscess models revealed that the rinA mutant strain exhibited obvious virulence defects. When sarA is knocked out, the virulence of S.aureus had no significantly changes whether rinA is knocked out or not.

CONCLUSION

Our fndings demonstrated that phage transcription activator RinA regulates S. aureus virulence by governing sarA expression.

Multiomics characterization of methicillin-resistant Staphylococcus aureus (MRSA) isolates with heterogeneous intermediate resistance to vancomycin (hVISA) in Latin America

BACKGROUND

Heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) compromise the clinical efficacy of vancomycin. The hVISA isolates spontaneously produce vancomycin-intermediate Staphylococcus aureus (VISA) cells generated by diverse and intriguing mechanisms.

OBJECTIVE

To characterize the biomolecular profile of clinical hVISA applying genomic, transcriptomic and metabolomic approaches.

METHODS

39 hVISA and 305 VSSA and their genomes were included. Core genome-based Bayesian phylogenetic reconstructions were built and alterations in predicted proteins in VISA/hVISA were interrogated. Linear discriminant analysis and a Genome-Wide Association Study were performed. Differentially expressed genes were identified in hVISA-VSSA by RNA-sequencing. The undirected profiles of metabolites were determined by liquid chromatography and hydrophilic interaction in six CC5-MRSA.

RESULTS

Genomic relatedness of MRSA associated to hVISA phenotype was not detected. The change Try38 → His in Atl (autolysin) was identified in 92% of the hVISA. We identified SNPs and k-mers associated to hVISA in 11 coding regions with predicted functions in virulence, transport systems, carbohydrate metabolism and tRNA synthesis. Further, capABCDE, sdrD, esaA, esaD, essA and ssaA genes were overexpressed in hVISA, while lacABCDEFG genes were downregulated. Additionally, valine, threonine, leucine tyrosine, FAD and NADH were more abundant in VSSA, while arginine, glycine and betaine were more abundant in hVISA. Finally, we observed altered metabolic pathways in hVISA, including purine and pyrimidine pathway, CoA biosynthesis, amino acid metabolism and aminoacyl tRNA biosynthesis.

CONCLUSIONS

Our results show that the mechanism of hVISA involves major changes in regulatory systems, expression of virulence factors and reduction in glycolysis via TCA cycle. This work contributes to the understanding of the development of this complex resistance mechanism in regional strains.

Asterias pectinifera-Derived Collagen Peptides Mixed with Halocynthia roretzi Extracts Exhibit Anti-Photoaging Activities during Exposure to UV Irradiation, and Antibacterial Properties

Asterias pectinifera, a species of starfish and cause of concern in the aquaculture industry, was recently identified as a source of non-toxic and highly water-soluble collagen peptides. In this study, we investigated the antioxidant and anti-photoaging functions of compounds formulated using collagen peptides from extracts of Asterias pectinifera and Halocynthia roretzi (AH). Our results showed that AH compounds have various skin protective functions, including antioxidant effects, determined by measuring the scavenging activity of 2,2-diphenyl-1-picrylhydrazyl radicals, as well as anti-melanogenic effects, determined by measuring tyrosinase inhibition activity. To determine whether ethosome-encapsulated AH compounds (E(AH)) exert ultraviolet (UV)-protective effects, human dermal fibroblasts or keratinocytes were incubated with E(AH) before and after exposure to UVA or UVB. E(AH) treatment led to inhibition of photoaging-induced secretion of matrix metalloproteinase-1 and interleukin-6 and -8, which are associated with inflammatory responses during UV irradiation. Finally, the antibacterial effects of AH and E(AH) were confirmed against both gram-negative and gram-positive bacteria. Our results indicate that E(AH) has the potential for use in the development of cosmetics with a range of skin protective functions.

PurN Is Involved in Antibiotic Tolerance and Virulence in Staphylococcus aureus

Staphylococcus aureus can cause chronic infections which are closely related to persister formation. Purine metabolism is involved in S. aureus persister formation, and purN, encoding phosphoribosylglycinamide formyltransferase, is an important gene in the purine metabolism process. In this study, we generated a ΔpurN mutant of the S. aureus Newman strain and assessed its roles in antibiotic tolerance and virulence. The ΔpurN in the late exponential phase had a significant defect in persistence to antibiotics. Complementation of the ΔpurN restored its tolerance to different antibiotics. PurN significantly affected virulence gene expression, hemolytic ability, and biofilm formation in S. aureus. Moreover, the LD₅₀ (3.28 × 10¹⁰ CFU/mL) of the ΔpurN for BALB/c mice was significantly higher than that of the parental strain (2.81 × 10⁹ CFU/mL). Transcriptome analysis revealed that 58 genes that were involved in purine metabolism, alanine, aspartate, glutamate metabolism, and 2-oxocarboxylic acid metabolism, etc., were downregulated, while 24 genes involved in ABC transporter and transferase activity were upregulated in ΔpurN vs. parental strain. Protein-protein interaction network showed that there was a close relationship between PurN and GltB, and SaeRS. The study demonstrated that PurN participates in the formation of the late exponential phase S. aureus persisters via GltB and regulates its virulence by activating the SaeRS two-component system.

Synergistic Microbicidal Effect of AUR and PEITC Against Staphylococcus aureus Skin Infection

Given the increasing prevalence of Staphylococcus aureus antibiotic resistance, there is an urgent need to repurpose approved drugs with known pharmacology and toxicology as an alternative therapeutic strategy. We have reported that the sustained monotherapy of auranofin (AUR) inevitably resulted in reduced susceptibility or even the emergence of resistance to AUR in S. aureus. However, whether drug combination could increase antibacterial activity while preventing AUR resistance is still unknown. Here, we focused on the important role of AUR combined with phenethyl isothiocyanate (PEITC) in skin infection and determined the synergistic antimicrobial effect on S. aureus by using checkerboard assays and time-kill kinetics analysis. This synergistic antimicrobial activity correlated with increased reactive oxygen species (ROS) generation, disruption of bacterial cell structure, and inhibition of biofilm formation. We also showed that AUR synergized with PEITC effectively restored the susceptibility to AUR via regulating thioredoxin reductase (TrxR) and rescued mice from subcutaneous abscesses through eliminating S. aureus pathogens, including methicillin-resistant S. aureus (MRSA). Collectively, our study indicated that the AUR and PEITC combination had a synergistic antimicrobial impact on S. aureus in vitro and in vivo. These results suggest that AUR and PEITC treatment may be a promising option for S. aureus infection.

Delineating the Role of the msaABCR Operon in Staphylococcal Overflow Metabolism

Staphylococcus aureus is an important human pathogen that can infect almost every organ system, resulting in a high incidence of morbidity and mortality. The msaABCR operon is an important regulator of several staphylococcal phenotypes, including biofilm development, cell wall crosslinking, antibiotic resistance, oxidative stress, and acute and chronic implant-associated osteomyelitis. Our previous study showed that, by modulating murein hydrolase activity, the msaABCR operon negatively regulates the proteases that govern cell death. Here, we report further elucidation of the mechanism of cell death, which is regulated by the msaABCR operon at the molecular level in the USA300 LAC strain. We showed that deletion of msaABCR enhances weak-acid-dependent cell death, because, in the biofilm microenvironment, this mutant strain consumes glucose and produces acetate and acetoin at higher rates than wild-type USA300 LAC strain. We proposed the increased intracellular acidification leads to increased cell death. MsaB, a dual-function transcription factor and RNA chaperone, is a negative regulator of the cidR regulon, which has been shown to play an important role in overflow metabolism and programmed cell death during biofilm development in S. aureus. We found that MsaB binds directly to the cidR promoter, which represses expression of the cidR regulon and prevents transcription of the cidABC and alsSD operons. In addition, we observed that pyruvate induced expression of the msaABCR operon (MsaB). The results reported here have enabled us to decipher the role of the msaABCR operon in staphylococcal metabolic adaption during biofilm development.

Lactic Acid Bacteria from Gamecock and Goat Originating from Phitsanulok, Thailand: Isolation, Identification, Technological Properties and Probiotic Potential

From independent swab samples of the cloaca of indigenous gamecocks (CIG), anus of healthy baby goats (AHG), and vagina of goats (VG) originating from Phitsanulok, Thailand, a total of 263 isolates of lactic acid bacteria (LAB) were collected. Only three isolates, designated C707, G502, and V202, isolated from CIG, AHG, and VG, respectively, exhibited an excellent inhibitory zone diameter against foodborne pathogenic bacteria when evaluated by agar spot test. Isolates C707 and G502 were identified as Enterococcus faecium, whereas V202 was identified as Pediococcus acidilactici, based on 16S rRNA sequence analysis. When foodborne pathogenic bacteria were co-cultured with chosen LAB in mixed BHI-MRS broth at 39°C, their growth was suppressed. These LAB were found to be capable of surviving in simulated stomach conditions. Only the isolate G502 was able to survive in the conditions of simulated intestinal juice. This research suggests that selected LAB could be used as a food/feed supplement to reduce foodborne pathogenic bacteria and improve the safety of animal-based food or feed.

Oxidative Stress-Mediated Antibacterial Activity of the Total Flavonoid Extracted from the Agrimonia pilosa Ledeb. in Methicillin-Resistant Staphylococcusaureus (MRSA)

(1) Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a zoonotic pathogen that causes endocarditis, pneumonia, and skin diseases in humans and livestock. (2) Methods: The antibacterial effect of the total flavonoid against MRSA (ATCC43300) extracted from the Agrimonia pilosa Ledeb. (A. pilosa Ledeb) was evaluated by the microdilution method. The oxidative stresses in MRSA were evaluated by the levels of intracellular hydrogen peroxide (H₂O₂), reactive oxygen species (ROS), and oxidative stress-related genes. The DNA oxidative damage was tested by the 8-hydroxy-2′-deoxyguanosine (8-OHdG) and DNA gel electrophoresis. The differentially expressed proteins were determined by the method of SDS-PAGE and NanoLC-ESI-MS/MS, while the mRNAs of differential proteins were determined by Real-Time PCR. The changes of ultra-structures in MRSA were observed by Transmission Electron Microscope (TEM). (3) Results: The minimum inhibitory concentration (MIC) of the total flavonoid against MRSA was recorded as 62.5 μg/mL. After treatment with the total flavonoid, the levels of intracellular H₂O₂ and ROS were increased and the gene expressions against oxidative stress (SodA, katA, TrxB) were decreased (p < 0.01), while the gene expression for oxidative stress (PerR) was increased (p < 0.01). The level of intracellular 8-OHdG in MRSA was increased (p < 0.01) and the DNA was damaged. The results of TEM also showed that the total flavonoid could destroy the ultra-structures in the bacteria. (4) Conclusions: The total flavonoid extracted from the A. pilosa Ledeb can induce the oxidative stress that disturbed the energy metabolism and protein synthesis in MRSA.

Staphylococcus aureus-A Known Opponent against Host Defense Mechanisms and Vaccine Development-Do We Still Have a Chance to Win?

The main purpose of this review is to present justification for the urgent need to implement specific prophylaxis of invasive Staphylococcus aureus infections. We emphasize the difficulties in achieving this goal due to numerous S. aureus virulence factors important for the process of infection and the remarkable ability of these bacteria to avoid host defense mechanisms. We precede these considerations with a brief overview of the global necessitiy to intensify the use of vaccines against other pathogens as well, particularly in light of an impasse in antibiotic therapy. Finally, we point out global trends in research into modern technologies used in the field of molecular microbiology to develop new vaccines. We focus on the vaccines designed to fight the infections caused by S. aureus, which are often resistant to the majority of available therapeutic options.

Design, Synthesis, and Biological Evaluation of Densely Substituted Dihydropyrano[2,3-c]pyrazoles via a Taurine-Catalyzed Green Multicomponent Approach

An efficient taurine-catalyzed green multicomponent approach has been described for the first time to synthesize densely substituted therapeutic core dihydropyrano[2,3-c]pyrazoles. Applications of the developed synthetic strategies and technologies revealed the synthesis of a series of newly designed 1,4-dihydropyrano[2,3-c]pyrazoles containing isonicotinamide, spirooxindole, and indole moieties. Detailed in silico analysis of the synthesized analogues revealed their potential to bind wild-type and antibiotic-resistant variants of dihydrofolate reductase, a principal drug target enzyme for emerging antibiotic-resistant pathogenic Staphylococcus aureus strains. Hence, the synthesized dihydropyrano[2,3-c]pyrazole derivatives presented herein hold immense promise to develop future antistaphylococcal therapeutic agents.

Clonality, virulence genes, and antibiotic resistance of Staphylococcus aureus isolated from blood in Shandong, China

BACKGROUND

Bloodstream infection (BSI) caused by Staphylococcus aureus (S. aureus) can be life-threatening and pose a great challenge to infection control and clinical treatment. However, little information exists regarding the characterization of S. aureus in BSI patients in Shandong, China. To identify the clonality, virulence genes, and antibiotic resistance of S. aureus in blood, a total of 101 nonrepetitive blood isolates were collected. The antibiotic resistance phenotypes were determined, and virulence genes were analyzed with polymerase chain reaction (PCR). Finally, the genetic relatedness was investigated with Staphylococcus chromosomal cassette mec (SCCmec) typing for methicillin-resistant S. aureus (MRSA) isolates, Staphylococcal protein A (spa), and multilocus sequence typing (MLST) for all of 101 isolates.

RESULTS

Of the 101 S. aureus isolates, 24 MRSA isolates and 77 methicillin-susceptible S. aureus (MSSA) isolates were identified. Overall, MRSA isolates had higher resistance rates than MSSA isolates when exposed to any of the 15 antibiotics tested in this study except for trimethoprim/sulfamethoxazole. Among the 17 virulence genes tested in this study, hla, hld, and hlg could be detected in all isolates. MRSA isolates were more likely to carry seb and hlb genes, while MSSA isolates were more likely to carry seg and sei genes. Thirty-five sequence types (STs) and 49 spa types were identified, of which ST59-t437 and ST398-t571 were the most abundant. These two genotypes were also the most abundant ST-spa types in MRSA and MSSA isolates, but their abundances shifted over time, with ST398-t571 being the predominant genotype from 2016 to 2017, and ST59-t437 from 2018 to 2020. Besides, all the ST59-t437 isolates harbored hlgb gene, whereas most (88.9%) ST398-t571 did not. In addition, twenty-four MRSA isolates were subject to SCCmec typing. SCCmec IVa was the most prevalent SCCmec type, and all the ST59-t437 MRSA isolates were SCCmec IVa. We also observed 15 new STs, and some of them were MRSA.

CONCLUSION

These findings provide additional observations and epidemiological data for blood S. aureus isolates, which can improve future infection-control measures and aid in potential clinical treatments in hospitals and other clinical settings.

Effect of biofilm on the survival of Staphylococcus aureus isolated from raw milk in high temperature and drying environment

Microbial contamination in dairy products is a momentous factor affecting food safety. Studies have shown that Staphylococcus aureus, which is an important causative agent of a range of infectious and foodborne diseases, may remain in raw milk after a series of complex processing processes. Although most S. aureus possess biofilm formation capacity, there are few studies concerning the role of biofilm formation of this bacterium in stress tolerance and longtime survival in the dairy products. In this study, we selected 5 S. aureus (RMSA1, RMSA2, RMSA3, RMSA4 and RMSA5) isolates from raw milk and investigated their virulence and biofilm characteristics. Results from biofilm assays showed that all 6 S. aureus strains (5 dairy isolates and 1 human-derived model strain NCTC8325) could form complete biofilms in vitro. The reverse transcription-PCR experiments confirmed that multiple genes related to virulence factors and biofilm formation were expressed in the 6 strains. Furthermore, we simulated the high temperature (at 60 °C for 30 min) and drying pressure (at 37 °C for 24 h) during dairy processing to detect the survival rate of strains culturedunderbiofilm or planktonic condition. The data showed that under high temperature and dry conditions, the survival rates of strains cultured under biofilm conditions were much higher than that of strains cultured under planktonic conditions. In addition, the adversity resistance associated with biofilm formation was more obvious in the milk-isolated strains compared with strain NCTC8325. This study provides evidence regarding the mechanisms of stress resistance of S. aureus strains isolated from raw milk and contribute to prevention of dairy product contamination caused by this bacterium.

The impact of human vaccines on bacterial antimicrobial resistance. A review

At present, the dramatic rise in antimicrobial resistance (AMR) among important human bacterial pathogens is reaching a state of global crisis threatening a return to the pre-antibiotic era. AMR, already a significant burden on public health and economies, is anticipated to grow even more severe in the coming decades. Several licensed vaccines, targeting both bacterial (Haemophilus influenzae type b, Streptococcus pneumoniae, Salmonella enterica serovar Typhi) and viral (influenza virus, rotavirus) human pathogens, have already proven their anti-AMR benefits by reducing unwarranted antibiotic consumption and antibiotic-resistant bacterial strains and by promoting herd immunity. A number of new investigational vaccines, with a potential to reduce the spread of multidrug-resistant bacterial pathogens, are also in various stages of clinical development. Nevertheless, vaccines as a tool to combat AMR remain underappreciated and unfortunately underutilized. Global mobilization of public health and industry resources is key to maximizing the use of licensed vaccines, and the development of new prophylactic vaccines could have a profound impact on reducing AMR.

Bacillus licheniformis and Bacillus subtilis, Probiotics That Induce the Formation of Macrophage Extracellular Traps

Probiotics are considered living microorganisms that help preserve the health of the host who uses them. Bacillus are a genus of Gram-positive bacteria used as probiotics for animal and human consumption. They are currently distributed in various commercial forms. Two of the species used as probiotics are B. licheniformis and B. subtilis. Macrophages are central cells in the immune response, being fundamental in the elimination of microbial pathogens, for which they use various mechanisms, including the formation of extracellular traps (METs). There have been very few studies carried out on the participation of macrophages in response to the interaction of probiotics of the genus Bacillus with the host. In this work, we used macrophages from the J774A mouse cell line.1, and we found that they are susceptible to infection by the two Bacillus species. However, both species were eliminated as the infection progressed. Using confocal microscopy, we identified the formation of METs from the first hours of infection, which were characterized by the presence of myeloperoxidase (MPO) and citrullinated histone (Hit3Cit). Quantitative data on extracellular DNA release were also obtained; release was observed starting in the first hour of infection. The induction of METs by B. licheniformis caused a significant decrease in the colony-forming units (CFU) of Staphylococcus aureus. The induction of METS by bacteria of the Bacillus genus is a mechanism that participates in controlling the probiotic and potentially pathogenic bacteria such as S. aureus. The induction of METs to control pathogens may be a novel mechanism that could explain the beneficial effects of probiotics of the genus Bacillus.

Galleria mellonella as an infection model: an in-depth look at why it works and practical considerations for successful application

The larva of the greater wax moth Galleria mellonella is an increasingly popular model for assessing the virulence of bacterial pathogens and the effectiveness of antimicrobial agents. In this review, we discuss details of the components of the G. mellonella larval immune system that underpin its use as an alternative infection model, and provide an updated overview of the state of the art of research with G. mellonella infection models to study bacterial virulence, and in the evaluation of antimicrobial efficacy. Emphasis is given to virulence studies with relevant human and veterinary pathogens, especially Escherichia coli and bacteria of the ESKAPE group. In addition, we make practical recommendations for larval rearing and testing, and overcoming potential limitations of the use of the model, which facilitate intra- and interlaboratory reproducibility.

Rapid and Simultaneous Detection of Five, Viable, Foodborne Pathogenic Bacteria by Photoinduced PMAxx-Coupled Multiplex PCR in Fresh Juice

Escherichia coli, Staphylococcus aureus, Shigella, Pseudomonas aeruginosa, and Klebsiella pneumoniae are common foodborne pathogens. In this study, the light-induced PMAxx-coupled multiplex PCR (PMAxx-mPCR) was established to detect the aforementioned five foodborne pathogens in fresh juice at the same time. Moreover, PMAxx pretreatment could effectively distinguish live bacteria from dead bacteria. The optimized PMAxx pretreatment conditions were incubation with a final concentration of 10 μmol/L PMAxx for 10 min and then photolysis for 8 min. After PMAxx pretreatment, the difference in Ct values with or without PMAxx was determined by quantitative real-time PCR. The results showed a significant difference in Ct value before and after PMAxx treatment. Finally, the bacteria-contaminated fresh juice samples treated with PMAxx dye were detected by mPCR. The detection limit of PMAxx-mPCR was 10² colony-forming units (CFU)/mL for E. coli, Shigella, P. aeruginosa, and K. pneumoniae and 10³ CFU/mL for S. aureus. Compared with mPCR detection of samples without PMAxx treatment, the proposed method solved the false-positive problem due to dead bacteria. Hence, an accurate and efficient method for the simultaneous detection of five types of pathogenic bacteria was established. This method could be applied to analytical procedures for ensuring food safety.

Fine-Tuning of Alkaline Residues on the Hydrophilic Face Provides a Non-toxic Cationic α-Helical Antimicrobial Peptide Against Antibiotic-Resistant ESKAPE Pathogens

Antibiotic-resistant ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) has become a serious threat to public health worldwide. Cationic α-helical antimicrobial peptides (CαAMPs) have attracted much attention as promising solutions in post-antibiotic era. However, strong hemolytic activity and in vivo inefficacy have hindered their pharmaceutical development. Here, we attempt to address these obstacles by investigating BmKn2 and BmKn2-7, two scorpion-derived CαAMPs with the same hydrophobic face and a distinct hydrophilic face. Through structural comparison, mutant design and functional analyses, we found that while keeping the hydrophobic face unchanged, increasing the number of alkaline residues (i.e., Lys + Arg residues) on the hydrophilic face of BmKn2 reduces the hemolytic activity and broadens the antimicrobial spectrum. Strikingly, when keeping the total number of alkaline residues constant, increasing the number of Lys residues on the hydrophilic face of BmKn2-7 significantly reduces the hemolytic activity but does not influence the antimicrobial activity. BmKn2-7K, a mutant of BmKn2-7 in which all of the Arg residues on the hydrophilic face were replaced with Lys, showed the lowest hemolytic activity and potent antimicrobial activity against antibiotic-resistant ESKAPE pathogens. Moreover, in vivo experiments indicate that BmKn2-7K displays potent antimicrobial efficacy against both the penicillin-resistant S. aureus and the carbapenem- and multidrug-resistant A. baumannii, and is non-toxic at the antimicrobial dosages. Taken together, our work highlights the significant functional disparity of Lys vs Arg in the scorpion-derived antimicrobial peptide BmKn2-7, and provides a promising lead molecule for drug development against ESKAPE pathogens.

Antistaphylococcal Activity of the FtsZ Inhibitor C109

Staphylococcus aureus infections represent a great concern due to their versatility and involvement in different types of diseases. The shortage of available clinical options, especially to treat multiresistant strains, makes the discovery of new effective compounds essential. Here we describe the activity of the previously described cell division inhibitor C109 against methicillin-sensitive and -resistant S. aureus strains. Antibiofilm activity was assessed using microtiter plates, confocal microscopy, and in an in vitro biofilm wound model. The ability of C109 to block FtsZ GTPase activity and polymerization was tested in vitro. Altogether, the results show that the FtsZ inhibitor C109 has activity against a wide range of S. aureus strains and support its use as an antistaphylococcal compound.

Castaneroxy A From the Leaves of Castanea sativa Inhibits Virulence in Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) represents one of the most serious infectious disease concerns worldwide, with the CDC labeling it a "serious threat" in 2019. The current arsenal of antibiotics works by targeting bacterial growth and survival, which exerts great selective pressure for the development of resistance. The development of novel anti-infectives that inhibit quorum sensing and thus virulence in MRSA has been recurrently proposed as a promising therapeutic approach. In a follow-up of a study examining the MRSA quorum sensing inhibitory activity of extracts of Italian plants used in local traditional medicine, 224C-F2 was reported as a bioactive fraction of a Castanea sativa (European chestnut) leaf extract. The fraction demonstrated high activity in vitro and effective attenuation of MRSA pathogenicity in a mouse model of skin infection. Through further bioassay-guided fractionation using reverse-phase high performance liquid chromatography, a novel hydroperoxy cycloartane triterpenoid, castaneroxy A (1), was isolated. Its structure was established by nuclear magnetic resonance, mass spectrometry and X-ray diffraction analyses. Isomers of 1 were also detected in an adjacent fraction. In a series of assays assessing inhibition of markers of MRSA virulence, 1 exerted activities in the low micromolar range. It inhibited agr::P3 activation (IC₅₀ = 31.72 µM), δ-toxin production (IC₅₀ = 31.72 µM in NRS385), supernatant cytotoxicity to HaCaT human keratinocytes (IC₅₀ = 7.93 µM in NRS385), and rabbit erythrocyte hemolytic activity (IC₅₀ = 7.93 µM in LAC). Compound 1 did not inhibit biofilm production, and at high concentrations it exerted cytotoxicity against human keratinocytes greater than that of 224C-F2. Finally, 1 reduced dermonecrosis in a murine model of MRSA infection. The results establish 1 as a promising antivirulence candidate for development against MRSA.

Biotechnological applications of versatile plant lipid transfer proteins (LTPs)

Plant AMPs are usually cysteine-rich, and can be classified in several classes, including lipid transfer proteins (LTPs). LTPs are small plant cationic peptides, and can be classified in two subclasses, LTP₁ (9-10 kDa) and LTP₂ (7 kDa). They have been identified and isolated from various plant species and can be involved in a number of processes, including responses against several phytopathogens. LTP₁ presents 4 parallel α- helices and a 3₁₀-helix fragment. These structures form a tunnel with large and small entrances. LTP₂ presents 3 parallel α- helices, which form a cavity with triangular structure. Both LTP subclasses present a hydrophobic cavity, which makes interaction with different lipids and general hydrophobic molecules possible. Several studies report a broad spectrum of activity of plant LTPs, including antibacterial, antifungal, antiviral, antitumoral, and insecticidal activity. Thus, these molecules can be employed in human and animal health as an alternative to the conventional treatment of disease, well as providing the source of novel drugs. However, employing peptides in human health can present challenges, such as the toxicity of peptides, the difference between the results found in in vitro assays and in pre-clinical or clinical tests and their low efficiency against Gram-negative bacteria. In this context, plant LTPs can be an interesting alternative means by which to bypass such challenges. This review addresses the versatility of plant LTPs, their broad spectrum of activities and their potential applications in human and animal health and in agricultural production, and examines challenges in their biotechnological application.

Staphylococcus aureus Ventilator-Associated Pneumonia: A Study of Bacterio-Epidemiological Profile and Virulence Factors

Ventilator-associated pneumonia (VAP) represents a major cause of nosocomial infections in the intensive care units in which Staphylococcus aureus is frequently involved. Better knowledge of this pathogen is required in order to enhance the patient’s treatment and care. In this article, we studied the bacteriological profile and virulence factors of S. aureus-related VAP on a 3-year period. We included a collection of S. aureus strains (n = 35) isolated from respiratory samples from patients diagnosed with VAP in the intensive care units. We studied the bacteriological aspects and we searched for the presence of virulence factors (SpA, FnbpA, Hla, and PVL genes) in the strains, and we also studied the clinical and biological aspects of the infections. The average age of our patients was of 36 years and they were predominantly males (sex ratio = 3.37). A severe head trauma or a history of coma was noted in 73.43% of the patients. The average duration of ventilation was 29 days. Among the studied strains, five were Methicillin-resistant S. aureus of which three expressed the mecA gene. Overall, the Hla gene was detected in 85.7% of the strains and it was more prevalent in Methicillin-susceptible than Methicillin-resistant strains (93.3% versus 40%; P = 0.014). FnbpA, Spa, and PVL genes were detected, respectively, in 80%, 45.7%, and 20% of the strains. Therefore, our studied strains were essentially associated with the production of Hla and FnbpA genes. It is, however, important to elucidate their expression in order to establish their role in the VAP pathogenesis.

Vaccination with Detoxified Leukocidin AB Reduces Bacterial Load in a Staphylococcus aureus Minipig Deep Surgical Wound Infection Model

Vaccines against Staphylococcus aureus have eluded researchers for >3 decades while the burden of staphylococcal diseases has increased. Early vaccine attempts mainly used rodents to characterize preclinical efficacy, and all subsequently failed in human clinical efficacy trials. More recently, leukocidin AB (LukAB) has gained interest as a vaccine antigen. We developed a minipig deep surgical wound infection model offering 3 independent efficacy readouts: bacterial load at the superficial and at the deep-seated surgical site, and dissemination of bacteria. Due to similarities with humans, minipigs are an attractive option to study novel vaccine candidates. With this model, we characterized the efficacy of a LukAB toxoid as vaccine candidate. Compared to control animals, a 3-log reduction of bacteria at the deep-seated surgical site was observed in LukAB-treated minipigs and dissemination of bacteria was dramatically reduced. Therefore, LukAB toxoids may be a useful addition to S. aureus vaccines and warrant further study.