Incidence, prevalence, and management of MRSA bacteremia across patient populations-a review of recent developments in MRSA management and treatment

The anti-MRSA resource: a comprehensive archive of anti-MRSA peptides and essential oils

Methicillin-resistant Staphylococcus aureus (MRSA), a major cause of fatalities due to Antimicrobial Resistance (AMR), can act as an opportunistic pathogen despite being part of the normal human flora. MRSA infections, such as skin infections, pneumonia, sepsis, and surgical site infections, have risen significantly, with bloodstream infection cases increasing from 21% in 2016 to 35% in 2020. This surge has prompted research into alternative treatments like nanomaterials, photodynamic therapy, antimicrobial peptides (AMPs), and essential oils (EOs). AMPs and EOs have shown higher success rates compared to other alternatives, gaining significant attention for their effectiveness against MRSA. In this perspective, we have created a database for peptides and EOs that have been discovered to treat MRSA. Manual data curation was done to get related information on each of the anti-MRSA EOs and AMPs from the PubMed articles. This led to the curation of 1789 peptides (1029 unique) and 863 EOs (671 unique) that have been reported against MRSA. This was followed by database creation and the development of tools for sequence analysis and determination of physiochemical properties. This resource has been named 'The Anti-MRSA Resource' or 'TAMRSAR' which we believe will aid in future drug development efforts to combat the diseases caused by MRSA. The database is accessible on any web browser at the URL: https://bblserver.org.in/tamrsar/.

Prevalence of bacteremia and antimicrobial resistance pattern among patients in South Lebanon

BACKGROUND

Bacteremia is a leading cause of morbidity and mortality worldwide. Rising prevalence and antimicrobial resistance (AMR) are critical public health issues. This study aims to determine the prevalence of bacteremia and the AMR pattern among patients in South Lebanon.

METHODS

A cross-sectional study analyzed 76 positive blood cultures from Hammoud and Labib Hospitals in South Lebanon between September 2023 and March 2024. The phenotype and antimicrobial susceptibility of gram-positive and gram-negative were determined by using disk diffusion. Genotypically, polymerase chain reaction was used to detect the carbapenemase-resistant Enterobacterales (CRE), extended-spectrum β-lactamases (ESBL), and methicillin-resistant Staphylococcus aureus genes.

RESULTS

Out of 76 isolates, 38 (50%) were gram-positive and 38 (50%) were gram-negative. Escherichia coli was the most common among gram-negative (18. 42%), with 10.52% ESBL and 3.94% CRE. Staphylococcus coagulase negative was the most common among gram-positive (40.78%), followed by Staphylococcus aureus (6.57%), with 3.94% methicillin-resistant S. aureus. The prevalent ESBL gene was CTX-M (100%), and for the CRE, NDM (66.66%) was the most common gene. Regarding S. aureus, 66.66% were mecA.

DISCUSSION

The diverse bacteremia isolates and resistance genes in South Lebanon reflect global variability in incidence and resistance profiles.

CONCLUSIONS

High rates of bacteremia and AMR in South Lebanon underscore the need for effective antibiotic stewardship programs.

Antibiotic Resistance in Fermented Foods Chain: Evaluating the Risks of Emergence of Enterococci as an Emerging Pathogen in Raw Milk Cheese

Fermented foods, particularly fermented dairy products, offer significant health benefits but also present serious concerns. Probiotic bacteria, such as lactic acid bacteria (LAB), found in these foods have been strongly linked to the selection and dissemination of antibiotic resistance genes (ARGs). This study aims to examine the potential risks associated with fermented foods, despite their importance in human nutrition, by analyzing the entire production chain from raw material acquisition to storage. Focusing on cheese production as a key fermented food, the study will investigate various aspects, including dairy farm management, milk acquisition, milk handling, and the application of good manufacturing practices (GMP) and good hygiene practices (GHP) in cheese production. The findings of this review highlight that ARGs found in LAB are similar to those observed in hygiene indicator bacteria like E. coli and pathogens like S. aureus. The deliberate use of antibiotics in dairy farms and the incorrect use of disinfectants in cheese factories contribute to the prevalence of antibiotic-resistant bacteria in cheeses. Cheese factories, with their high frequency of horizontal gene transfer, are environments where the microbiological diversity of raw milk can enhance ARG transfer. The interaction between the raw milk microbiota and other environmental microbiotas, facilitated by cross-contamination, increases metabolic communication between bacteria, further promoting ARG transfer. Understanding these bacterial and ARG interactions is crucial to ensure food safety for consumers.

Identification of an antibiotic from an HTS targeting EF-Tu:tRNA interaction: a prospective topical treatment for MRSA skin infections

Because of the urgent need for new antibiotics to treat drug-resistant bacterial pathogens, we employed an assay that rapidly screens large quantities of compounds for their ability to interfere with bacterial protein synthesis, in particular, the delivery of amino acids to the ribosome via tRNA and elongation factor Tu (EF-Tu). We have identified a drug lead, named MGC-10, which kills Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), with a MIC of 6 µM, while being harmless to mammalian cells in vitro in that concentration range. The antibacterial activity of MGC-10 was broad against over 50 strains of antibiotic-resistant samples obtained from hospital infections, where MGC-10 inhibited all tested strains of MRSA. Extensive selection and screening with MGC-10 did not yield any resistant strains, indicating it may have universal antibacterial activity against S. aureus. Pharmacokinetics performed in mice suggested that MGC-10 was too toxic for systemic use; however, it appears to have potential as a topical treatment for difficult-to-treat wounds or skin infections by Gram-positive pathogens such as MRSA. In a mouse skin-infection model with MRSA, MGC-10 performed as well or better than the present topical drug of choice, mupirocin. MGC-10 showed little, if any, accumulation in the livers of topically treated mice. These results bode well for the future use of MGC-10 in clinical application as it could be used to treat a broad range of S. aureus skin infections that are resistant to known antibiotics.IMPORTANCEThere is a critical need for new antibiotics to treat bacterial infections caused by pathogens resistant to many if not all currently available antibiotics. We describe here the identification of a prospective new antibiotic from high-throughput screening of a chemical library. The screening was designed to detect the inhibition of formation of a complex required for bacterial protein synthesis in all bacteria, the "ternary complex," comprised of elongation factor Tu (EF-Tu), aminoacyl-tRNA, and GTP. The inhibitory compound, renamed MGC-10, was effective against all Gram-positive bacteria, including a wide variety of methicillin-resistant Staphylococcus aureus (MRSA) strains. Although apparently too toxic for systemic use, the compound was safe and effective for topical use for treating skin infections in a mouse model. No resistance to the compound has been detected thus far, suggesting the potential to develop this compound for topical use to treat infections, especially those caused by pathogens resistant to existing antibiotics.

Bactericidal and anti-quorum sensing activity of repurposing drug Visomitin against Staphylococcus aureus

With the growing antibiotic resistance in Staphylococcus aureus, it is imperative to develop innovative therapeutic strategies against new targets to reduce selective survival pressures and incidence of resistance. In S. aureus, interbacterial communication relies on a quorum sensing system that regulates gene expression and physiological activities. Here, we identified that Visomitin, an antioxidant small molecule, exhibited bactericidal efficacy against methicillin-resistant S. aureus and its high tolerance phenotypes like intracellular bacteria and persister cells without inducing resistance. Critically, sub-minimal inhibitory concentrations (sub-MICs) of Visomitin could serve as a potent quorum-quencher reducing virulence production (such as haemolysin and staphyloxanthin), along with inhibiting biofilm formation, self-aggregation, and colony spreading of S. aureus. These effects were probably mediated by interfering with the S. aureus accessory gene regulator quorum sensing system. In summary, our findings suggest that Visomitin shows dual antimicrobial effects, including bactericidal effects at the concentrations above MIC and quorum sensing inhibition effects at sub-MICs, which holds promise for treating MRSA-related refractory infections.

Wireless Optogenetic Targeting Nociceptors Helps Host Cells Win the Competitive Colonization in Implant-Associated Infections

The role of nociceptive nerves in modulating immune responses to harmful stimuli via pain or itch induction remains controversial. Compared to conventional surgery, various implant surgeries are more prone to infections even with low bacterial loads. In this study, an optogenetic technique is introduced for selectively activating peripheral nociceptive nerves using a fully implantable, wirelessly rechargeable optogenetic device. By targeting nociceptors in the limbs of awake, freely moving mice, it is found that activation induces anticipatory immunity in the innervated territory and enhances the adhesion of various host cells to the implant surface. This effect mediates acute immune cell-mediated killing of Staphylococcus aureus on implants and enables the host to win "implant surface competition" against Staphylococcus aureus. This finding provides new strategies for preventing and treating implant-associated infections.

Repurposing TAK-285 as An Antibacterial Agent against Multidrug-Resistant Staphylococcus aureus by Targeting Cell Membrane

Infections and antimicrobial resistance are becoming serious global public health crises. Multidrug-resistant Staphylococcus aureus (S. aureus) infections necessitate novel antimicrobial development. In this study, we demonstrated TAK-285, a novel dual HER2/EGFR inhibitor, exerted antibacterial activity against 17 clinical methicillin-resistant S. aureus (MRSA) and 15 methicillin sensitive S. aureus (MSSA) isolates in vitro, with a minimum inhibitory concentration (MIC) of 13.7 μg/mL. At 1 × MIC, TAK-285 completely inhibited the growth of S. aureus bacterial planktonic cells, and at 2 × MIC, it exhibited a superior inhibitory effect on intracellular S. aureus SA113-GFP compared to linezolid. Moreover, TAK-285 effectively inhibited biofilm formation at sub-MIC, eradicated mature biofilm and eliminated bacteria within biofilms, as confirmed by CLSM. Furthermore, the disruption of cell membrane permeability and potential was found by TAK-285 on S. aureus, suggesting its targeting of cell membrane integrity. Global proteomic analysis demonstrated that TAK-285 disturbed the metabolic processes of S. aureus, interfered with biofilm-related gene expression, and disrupted membrane-associated proteins. Conclusively, we repurposed TAK-285 as an antimicrobial with anti-biofilm properties against S. aureus by targeting cell membrane. This study provided strong evidence for the potential of TAK-285 as a promising antimicrobial agent against S. aureus.

Spermidine Associated with Gut Microbiota Protects Against MRSA Bloodstream Infection by Promoting Macrophage M2 Polarization

Methicillin-resistant Staphylococcus aureus (MRSA) is a major human pathogen that causes various diseases. Extensive researches highlight the significant role of gut microbiota and its metabolites, particularly spermidine, in infectious diseases. However, the immunomodulatory mechanisms of spermidine in MRSA-induced bloodstream infection remain unclear. Here, we confirmed the protective effects of spermidine in bloodstream infection in mice. Spermidine reduced the bacterial load and expression of inflammatory factors by shifting the macrophage phenotype to an anti-inflammatory phenotype, ultimately prolonging the survival of the infected mice. The protective effect against MRSA infection may rely on the elevated expression of protein tyrosine phosphatase nonreceptor 2 (PTPN2). Collectively, these findings confirm the immunoprotective effects of spermidine via binding to PTPN2 in MRSA bloodstream infection, providing new ideas for the treatment of related infectious diseases.

The Functional Study of Response Regulator ArlR Mutants in Staphylococcus Aureus

Staphylococcus aureus is a major cause of hospital-associated infections worldwide. The organism's ability to form biofilms has led to resistance against current treatment options such as beta-lactams, glycopeptides, and daptomycin. The ArlRS two-component system is a crucial regulatory system necessary for S. aureus autolysis, biofilm formation, capsule synthesis, and virulence. This study aims to investigate the role of the arlR deletion mutant in the detection and activation of S. aureus. We created an arlR deleted mutant and complementary strains and characterized their impact on the strains using partial growth measurement. The quantitative real-time PCR was performed to determine the expression of icaA, and the microscopic images of adherent cells were captured at the optical density of 600 to determine the primary bacterial adhesion. The biofilm formation assay was utilized to investigate the number of adherent cells using crystal violet staining. Eventually, the Triton X-100 autolysis assay was used to determine the influence of arlR on the cell autolytic activities. Our findings indicate that the deletion of arlR reduced the transcriptional expression of icaA but not icaR in the ica operon, leading to decrease in polysaccharide intercellular adhesin (PIA) synthesis. Compared to the wild-type and the complementary mutants, the arlR mutant exhibited decreased in biofilm production but increased autolysis. It concluded that the S. aureus response regulatory ArlR influences biofilm formation, agglutination, and autolysis. This work has significantly expanded our knowledge of the ArlRS two-component regulatory system and could aid in the development of novel antimicrobial strategies against S. aureus.

Rifabutin: a repurposed antibiotic with high potential against planktonic and biofilm staphylococcal clinical isolates

Staphylococcus aureus poses a significant threat as an opportunistic pathogen in humans, and animal medicine, particularly in the context of hospital-acquired infections (HAIs). Effective treatment is a significant challenge, contributing substantially to the global health burden. While antibiotic therapy remains the primary approach for staphylococcal infections, its efficacy is often compromised by the emergence of resistant strains and biofilm formation. The anticipated solution is the discovery and development of new antibacterial agents. However, this is a time consuming and expensive process with limited success rates. One potential alternative for addressing this challenge is the repurposing of existing antibiotics. This study investigated the potential of rifabutin (RFB) as a repurposed antibiotic for treating S. aureus infections. The minimum inhibitory concentration (MIC) of rifabutin was assessed by the broth microdilution method, in parallel to vancomycin, against 114 clinical isolates in planktonic form. The minimum biofilm inhibitory concentration (MBIC50) was determined by an adaptation of the broth microdilution method, followed by MTT assay, against a subset of selected 40 clinical isolates organized in biofilms. The study demonstrated that RFB MIC ranged from 0.002 to 6.250 μg/mL with a MIC50 of 0.013 μg/mL. RFB also demonstrated high anti-biofilm activity in the subset of 40 clinical isolates, with confirmed biofilm formation, with no significant MBIC50 differences observed between the MSSA and MRSA strains, in contrast to that observed for the VAN. These results highlight the promising efficacy of RFB against staphylococcal clinical isolates with different resistance patterns, whether in planktonic and biofilm forms.

Antimicrobial and Anti-Inflammatory Potential of Euphorbia paralias (L.): a bioprospecting study with phytoconstituents analysis

Objectives

The phytochemicals in the aerial parts of Euphorbia paralias (also known as Sea Spurge) and their anti-inflammatory and antimicrobial activities were investigated.

Methods

The methanolic extract was characterized using GC-MS and HPLC techniques. The anti-inflammatory feature was estimated through a Human Red Blood Cell (HRBC) membrane stabilization technique, while the antimicrobial feature was evaluated by the disc diffusion agar technique, minimum bactericidal concentration, and minimum inhibitory concentration (MIC) via micro-broth dilution method.

Results

The GC/MS results demonstrated the existence of various phytochemicals, such as n-hexadecenoic acid, cis-11-eicosenoic acid, and methyl stearate, recognized for their anti-inflammatory and antibacterial features. The similarity of the phytochemical composition with other Euphorbia species emphasizes the genus-wide similarity. The anti-inflammatory activity exhibited a noteworthy inhibitory effect comparable to the reference drug indomethacin. The extract's antimicrobial potential was tested against a range of microorganisms, demonstrating significant action against Gram-positive bacteria and Candida albicans. The quantification of total phenolics and flavonoids further supported the therapeutic potential of the extract.

Conclusion

The methanolic extract from E. paralias emerges as a successful natural source of important active constituents with potential applications as anti-inflammatory and antimicrobial agents. This research provides a first step to valorize Euphorbia paralias insights as a source of worthwhile phytochemicals that have potential applications in the pharmaceutical industry.

Development of a One-Step Multiplex qPCR Assay for Detection of Methicillin and Vancomycin Drug Resistance Genes in Antibiotic-Resistant Bacteria

The most common antibiotic-resistant bacteria in Korea are methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). Pathogen identification in clinical laboratories can be divided into traditional phenotype- and genotype-based methods, both of which are complementary to each other. The genotype-based method using multiplex real-time polymerase chain reaction (PCR) is a rapid and accurate technique that analyzes material at the genetic level by targeting genes simultaneously. Accordingly, we aimed to develop a rapid method for studying the genetic characteristics of antibiotic-resistant bacteria and to provide an experimental guide for the efficient antibiotic resistance gene analysis of mecA detection for MRSA and vanA or vanB detection for VRE using a one-step multiplex qPCR assay at an early stage of infection. As a result, the sensitivity and specificity of the mecA gene for clinical S. aureus isolates, including MRSA and methicillin-susceptible S. aureus, were 97.44% (95% CI, 86.82-99.87%) and 96.15% (95% CI, 87.02-99.32%), respectively. The receiver operating characteristic area under the curve for the diagnosis of MRSA was 0.9798 (*** p < 0.0001). Therefore, the molecular diagnostic method using this newly developed one-step multiplex qPCR assay can provide accurate and rapid results for the treatment of patients with MRSA and VRE infections.

Exploring diflunisal as a synergistic agent against Staphylococcus aureus biofilm formation

Staphylococcus aureus is a bacterial pathogen of considerable significance in public health, capable of inducing a diverse range of infectious diseases. One of the most notorious mechanisms used by S. aureus to survive and colonize the site of infection is its ability to form biofilms. Diflunisal, a non-steroidal anti-inflammatory drug (NSAID), is a known inhibitor of the Agr system in S. aureus, which is key in regulating biofilm formation. This study evaluated the effect of broad-spectrum antibiotics in combination with diflunisal on S. aureus biofilm density. Eight antibiotics were tested independently at different concentrations and in combination with diflunisal to assess their effect on S. aureus biofilm formation. When using the antibiotics alone and with diflunisal, a significant control effect on biofilm formation was observed (p < 0.05), irrespective of diflunisal presence, but did not achieve a complete biofilm growth inhibition. Over time, diflunisal influenced biofilm formation; however, such an effect was correlated with antibiotic concentration and exposure time. With amikacin treatments, biofilm density increased with extended exposure time. In the case of imipenem, doripenem, levofloxacin, and ciprofloxacin, lower doses and absence of diflunisal showed higher control over biofilm growth with longer exposure. However, in all cases, diflunisal did not significantly affect the treatment effect on biofilm formation. In the absence of antibiotics, diflunisal significantly reduced biofilm formation by 53.12% (p < 0.05). This study suggests that diflunisal could be a potential treatment to control S. aureus biofilms, but it does not enhance biofilm inhibition when combined with antibiotics.

Two draft genome assemblies of Staphylococcus aureus strains isolated from a cheek swab of a healthy female participant

Staphylococcus aureus is an opportunistic pathogen often commensal within the nasal and oral cavities. Here we present the genomes of S. aureus O139-S and O139-NS, both isolated from the cheek swab of a healthy female participant. While found in the same sample, the two strains displayed distinct colony morphologies.

Comparative effectiveness and safety of six antibiotics in treating MRSA infections: A network meta-analysis

OBJECTIVES

This study conducted a network meta-analysis comparing linezolid, teicoplanin, daptomycin, tigecycline, and ceftaroline fosamil with vancomycin for treating MRSA-related diseases, addressing the lack of comprehensive evaluations in existing research on antibiotic therapy for MRSA infections.

METHODS

We systematically searched databases including PubMed, Embase, Web of Science, the Cochrane Librar up to August 22, 2023. All eligible randomized controlled trials of the six antibiotics were included in the NMA, and their effectiveness and safety were compared across various MRSA-related diseases. Categorical data were used for the odds ratio (OR), and continuous data were used for mean difference (SMD). The surface under the cumulative ranking (SUCRA) was employed to evaluate the incidence rate.

RESULTS

According to SUCRA results, daptomycin was the most effective treatment (73.0%) in bloodstream infections. In pulmonary infections and skin and soft tissue infections, linezolid out-performed other antibiotics in effectiveness rate (90.6% and 86.3%), microbial killing rate (93.3% and 93.1%). Vancomycin showed lower adverse reactions than teicoplanin, with less hepatotoxicity compared to linezolid and tigecycline. Linezolid had higher thrombocytopenia risk but lower nephrotoxicity risk than others. Vancomycin was less effective in microbial killing rates than linezolid across various infections.

CONCLUSION

The present research suggests that in pulmonary infections and skin and soft tissue infections, linezolid may be a better option for treating MRSA-related diseases. However, caution is warranted due to the association of linezolid with thrombocytopenia.

TRIAL REGISTRATION

Our study protocol was registered with the International Prospective Register of SystematicReviews (PROSPERO); Registration number: CRD42024535142.

Prevalence and Antibiotic Resistance Patterns of Methicillin-Resistant Staphylococcus aureus (MRSA) in a Hospital Setting: A Retrospective Study from 2018 to 2022

Methicillin-resistant Staphylococcus aureus (MRSA) is a highly infectious pathogen that poses a serious threat to human life and health. This study aimed to provide a scientific basis for the rational clinical use of antimicrobial drugs for treating MRSA infections and inform the development of preventive and control measures by analyzing the clinical distribution and resistance characteristics of MRSA in a hospital in Hebei China. To accomplish this, bacterial identification and drug sensitivity experiments were performed with 1858 Staphylococcus aureus (S. aureus) strains collected from a hospital from January 2018 to December 2022 using a phoenixTM-100 bacterial identification drug sensitivity analyzer. The experimental data were analyzed using WHONET 5.6 software, and the MRSA strains detected were analyzed for their clinical distribution and drug resistance. Of the 1858 S. aureus strains isolated, 429 were MRSA. Sputum samples had the highest MRSA detection rates (52.45%). Critical care medicine had the highest rate of MRSA (12.59%), followed by dermatology (9.79%). MRSA resistance to tetracycline increased by 13.9% over 5 years; resistance to quinupristin/dalfopristin also increased but remained low (1.9%). Resistance decreased to gentamicin, rifampicin, ciprofloxacin, and cotrimoxazole, though most significantly to erythromycin and clindamycin, exceeding 77% and 83%, respectively. No strains were resistant to vancomycin, teicoplanin, or linezolid, and drug resistance was most prevalent in patients ≥ 60 years old. This study will aid in improving the diagnosis and treatment of MRSA infections.

Draft genome sequences for a Staphylococcus aureus and a Staphylococcus haemolyticus isolate from nasal swab samples from healthy females

Staphylococcus aureus and Staphylococcus haemolyticus are common members of the human microbiota, but they are also opportunistic pathogens. To identify antibiotic resistance in healthy individuals, we present the genome sequences of S. aureus 139 N-1 and S. haemolyticus 173 N-3, both isolated from nasal swab samples from asymptomatic female participants.

Phenotypic and genotypic characterization of methicillin resistant Staphylococcus aureus associated with pyogenic infections

Background and Objectives

Staphylococcal infections are one of the major infectious diseases affecting globally in spite of advances in development of antimicrobial agents. Knowledge and awareness about the local pattern and prevalence of MRSA infections plays a key role in treatment. The aim of this study was to identify MRSA strains by phenotypic and genotypic methods and to analyze the antibiotic susceptibility pattern of MRSA strains from patients attending a tertiary care hospital.

Materials and Methods

This study was conducted over a period of 1 year, where 296 isolates of Staphylococcus aureus were isolated from various clinical specimens. The isolated strains were examined for antibiotic susceptibility by the modified Kirby Bauer disc diffusion method. Methicillin resistance was detected by cefoxitin disk diffusion test.

Results

A total of 104 isolates were found to be MRSA and 192 were found to be MSSA. Among the 104 MRSA isolates, 10 strains that were multidrug resistant were subjected to 16S rRNA gene sequencing analysis. All the 10 strains had a 99% match with S. aureus strains that were responsible for causing some serious biofilm mediated clinical manifestations like cystic fibrosis and device mediated infections. The biofilms were quantified using crystal violet staining and their ability to produce biofilms was analyzed using scanning electron microscopy and matched with the Genbank.

Conclusion

Hence these phylogenetic analysis aid in treating the patients and combating resistance to antibiotics.

Trends in infectious spondylitis from 2000 to 2020

PURPOSE

This study aimed to investigate the trends in infectious spondylitis over the past two decades.

METHODS

We included 157 cases, from 2000 to 2020, of infectious spondylitis. The cases were divided into two groups: 00 (cases during 2000-2009; 82 cases:) and 10 (cases during 2010-2020; 75 cases) groups. Patients' age, sex, causative organism, and localization were examined and compared between the two groups.

RESULTS

The proportions of women in the 00 and 10 groups were 30.5% and 38.7%, respectively, with no significant difference (P = 0.28). The average age was significantly higher in the 10 group (72.6 years) than in the 00 group (68.8 years; P < 0.01). A compromised host was the cause of infection in 52.4% and 36.0% of the patients in the 00 and 10 groups, respectively, showing a significant difference. The bacterial identification rates were 70.1% and 77.3% in the 00 and 10 groups, respectively (P < 0.01), and the genus Staphylococcus was the most common bacteria. The proportions of resistant bacteria such as methicillin-resistant Staphylococcus aureus in the 00 and 10 groups were 27.3% and 6.7%, respectively (P < 0.01). Conversely, infectious diseases caused by indigenous bacteria in the oral cavity and intestines were more common in the 10group (37.8%) than in the 00 group (13.0%), showing a significant difference (P < 0.01).

CONCLUSION

Recently, infections caused by indigenous bacteria in the oral cavity and intestines have increased more than those caused by resistant bacteria over the past two decade.

Recent Progress in Multifunctional Stimuli-Responsive Combinational Drug Delivery Systems for the Treatment of Biofilm-Forming Bacterial Infections

Drug-resistant infectious diseases pose a substantial challenge and threat to medical regimens. While adaptive laboratory evolution provides foresight for encountering such situations, it has inherent limitations. Novel drug delivery systems (DDSs) have garnered attention for overcoming these hurdles. Multi-stimuli responsive DDSs are particularly effective due to their reduced background leakage and targeted drug delivery to specific host sites for pathogen elimination. Bacterial infections create an acidic state in the microenvironment (pH: 5.0-5.5), which differs from normal physiological conditions (pH: 7.4). Infected areas are characterized by the overexpression of hyaluronidase, gelatinase, phospholipase, and other virulence factors. Consequently, several effective stimuli-responsive DDSs have been developed to target bacterial pathogens. Additionally, biofilms, structured communities of bacteria encased in a self-produced polymeric matrix, pose a significant challenge by conferring resistance to conventional antimicrobial treatments. Recent advancements in nano-drug delivery systems (nDDSs) show promise in enhancing antimicrobial efficacy by improving drug absorption and targeting within the biofilm matrix. nDDSs can deliver antimicrobials directly to the biofilm, facilitating more effective eradication of these resilient bacterial communities. Herein, this review examines challenges in DDS development, focusing on enhancing antibacterial activity and eradicating biofilms without adverse effects. Furthermore, advances in immune system modulation and photothermal therapy are discussed as future directions for the treatment of bacterial diseases.

The prevalence, risk factors, and outcomes of acute pulmonary embolism complicating sepsis and septic shock: a national inpatient sample analysis

The study aimed to evaluate the prevalence, risk factors, and clinical outcomes of pulmonary embolism in patients diagnosed with sepsis with and without shock. The National Inpatient Sample was used to identify adults with sepsis with and without shock between 2017 and 2019. The prevalence of acute pulmonary embolism and the association of acute pulmonary embolism with in-hospital mortality, hospital length of stay for survivors, and overall costs of hospitalization were evaluated. Multivariable logistic and linear regression analyses, adjusted for various parameters, were used to explore these associations. Of the estimated 5,019,369 sepsis hospitalizations, 1.2% of patients with sepsis without shock and 2.3% of patients with septic shock developed pulmonary embolism. The odds ratio for in-hospital mortality was 1.94 (95% confidence interval (CI) 1.85-2.03, p < 0.001). The coefficient for hospital length of stay was 3.24 (95% CI 3.03-3.45, p < 0.001). The coefficient for total costs was 46,513 (95% CI 43,079-49,947, p < 0.001). The prevalence of pulmonary embolism in patients diagnosed with sepsis with and without shock was 1.2 and 2.3%, respectively. Acute pulmonary embolism was associated with higher in-hospital mortality, longer hospital length of stay for survivors, and higher overall costs of hospitalization.

The Microbial Diversity and Antimicrobial Susceptibility Profile Underlying Diabetic Foot Osteomyelitis: A Retrospective Study Conducted in North Queensland, Australia

Background

Diabetic foot osteomyelitis (DFO) commonly occurs secondary to ulcerations of the skin. Empirical antibiotic agents are a key element of treatment and their use is dependent on local knowledge of the microbial spectrum of diabetic foot infections. This study aimed to retrospectively analyze the local microbiological profile, including bacterial culture/sensitivity results of DFO, and compare findings with literature. This study also aimed to review the concordance of microbiology results with national guidelines for the future treatment of DFO.

Methods

A retrospective review of clinical records was performed on patients who presented to the high-risk foot clinic, Townsville University Hospital, between 2018 and 2022. All patients older than 18 years and diagnosed with DFO were included. Our exclusion criteria included all other foot presentations, including trauma, vasculitis, and neoplasms.

Results

On the basis of the inclusion and exclusion criteria, 124 patients with DFO were selected. Most patients in the cohort were males (70.2%), non-Indigenous (68.5%), aged 50-69 years (55.6%), and with elevated HbA1c levels (>8.6). Chronic kidney disease (39.5%) and ischemic heart disease (41.9%) were common comorbidities. Of the pertinent microbial results, Staphylococcus aureus (~76%) was the most commonly isolated Gram-positive organism. Gram-positive bacteria were significantly increased in the elderly population with DFO (P < .05). All methicillin-resistant S aureus isolates were vancomycin- and cotrimoxazole-sensitive. Pseudomonas aeruginosa was the predominant Gram-negative organism isolated (39.3%). P aeruginosa exhibited low sensitivity to ciprofloxacin.

Conclusion

This study has enhanced our understanding of the various microbial species underlying DFO at our center and may be generalizable.

Level of Evidence

Level IV, retrospective case series.

Molecular and Phylogenomic Analysis of a Vancomycin Intermediate Resistance USA300LV Strain in Chile

Antimicrobial resistance is a major global health problem, and, among Gram-positive bacteria, methicillin-resistant Staphylococcus aureus (MRSA) represents a serious threat. MRSA causes a wide range of infections, including bacteremia, which, due to the limited use of β-lactams, is difficult to treat. This study aimed to analyze 51 MRSA isolates collected in 2018 from samples of patients with bacteremia from two hospitals of the Metropolitan Health Service of Santiago, Chile, both in their resistance profile and in the identification of virulence factors. In addition, genomic characterization was carried out by the WGS of an isolate that was shown to be the one of greatest concern (N°. 42) due to its intermediate resistance to vancomycin, multiple virulence factors and being classified as ST8 PVL-positive. In our study, most of the isolates turned out to be multidrug-resistant, but there are still therapeutic options, such as tetracycline, rifampicin, chloramphenicol and vancomycin, which are currently used for MRSA infections; however, 18% were PVL positive, which suggests greater virulence of these isolates. It was determined that isolate N°42 is grouped within the USA300-LV strains (ST8, PVL+, COMER+); however, it has been suggested that, in Chile, a complete displacement of the PVL-negative ST5 clone has not occurred.

Synthesis and Photophysical Characterization of Fluorescent Naphtho[2,3-d]thiazole-4,9-Diones and Their Antimicrobial Activity against Staphylococcus Strains

The chemical reaction of 2-(methylsulfinyl)naphtho[2,3-d]thiazole-4,9-dione (3) using different amines, including benzylamine (4a), morpholine (4b), thiomorpholine (4c), piperidine (4d), and 4-methylpiperazine (4e), produced corresponding new tricyclic naphtho[2,3-d]thiazole-4,9-dione compounds (5a-e) in moderate-to-good yields. The photophysical properties and antimicrobial activities of these compounds (5a-e) were then characterized. Owing to the extended π-conjugated system of naphtho[2,3-d]thiazole-4,9-dione skeleton and substituent effect, 5a-e showed fluorescence both in solution and in the solid state. The introduction of nitrogen-containing heterocycles at position 2 of the thiazole ring on naphtho[2,3-d]thiazole-4,9-dione led to large bathochromic shifts in solution, and 5b-e exhibited orange-red fluorescence with emission maxima of over 600 nm in highly polar solvents. Staphylococcus aureus (S. aureus) is a highly pathogenic bacterium, and infection with its antimicrobial-resistant pathogen methicillin-resistant S. aureus (MRSA) results in serious clinical problems. In this study, we also investigated the antimicrobial activities of 5a-e against S. aureus, MRSA, and S. epidermidis. Compounds 5c with thiomorpholine group and 5e with 4-methylpiperazine group showed potent antimicrobial activity against these bacteria. These results will lead to the development of new fluorescent dyes with antimicrobial activity in the future.

Cinnamaldehyde targets SarA to enhance β-lactam antibiotic activity against methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a current global public health problem due to its increasing resistance to the most recent antibiotic therapies. One critical approach is to develop ways to revitalize existing antibiotics. Here, we show that the phytogenic compound cinnamaldehyde (CIN) and β-lactam antibiotic combinations can functionally synergize and resensitize clinical MRSA isolates to β-lactam therapy and inhibit MRSA biofilm formation. Mechanistic studies indicated that the CIN potentiation effect on β-lactams was primarily the result of inhibition of the mecA expression by targeting the staphylococcal accessory regulator sarA. CIN alone or in combination with β-lactams decreased sarA gene expression and increased SarA protein phosphorylation that impaired SarA binding to the mecA promoter element and downregulated virulence genes such as those encoding biofilm, α-hemolysin, and adhesin. Perturbation of SarA-mecA binding thus interfered with PBP2a biosynthesis and this decreased MRSA resistance to β-lactams. Furthermore, CIN fully restored the anti-MRSA activities of β-lactam antibiotics in vivo in murine models of bacteremia and biofilm infections. Together, our results indicated that CIN acts as a β-lactam adjuvant and can be applied as an alternative therapy to combat multidrug-resistant MRSA infections.

Methicillin-Resistant Staphylococcus aureus Bacteremia Treated With Vancomycin Calculated by Area-Under-the-Curve in Patients With Elevated Vancomycin Minimum Inhibitory Concentrations

Purpose: Vancomycin is recommended as first-line treatment of methicillin-resistant Staphylococcus aureus (MRSA) bacteremia, dosed by area-under-the-curve (AUC) with an assumed minimum inhibitory concentration (MIC) of 1 mcg/mL via broth microdilution. The purpose of this study was to compare effectiveness of AUC-based and trough-based dosing in MRSA bacteremia with an MIC > 1 mcg/mL via Etest. Methods: This was a retrospective, observational cohort that compared vancomycin dosed by AUC or trough between January 1, 2017 and September 1, 2022. The primary outcome was a composite of treatment failure defined as peristent bacteremia ≥ 7 days, inpatient mortality within 90 days, or microbiologic relapse or readmission within 30 days. Secondary outcomes compared nephrotoxicity, hospital and ICU length of stay, MIC differences, and difference in exposure measured by AUC. Results: Twenty-four patients in each group met inclusion criteria. For the primary outcome, there was no statistical difference in treatment failure between trough and AUC groups, respectively [10 (41.7%) vs 10 (41.7%), P = 1.000]. There was no statistical difference in secondary outcomes, with incidence of nephrotoxicity [3 (12.5%) trough vs 2 (8.33%) AUC, P = 1.000] and median AUC exposure over treatment course [502.9 mcg.h/mL (454.1-599.9) vs 474 mcg.h/mL (435.3-533), P = .312] similar between groups. Conclusion: There was no statistically significant difference in treatment failure for vancomycin by AUC or trough with an Etest MIC > 1 mcg/mL. Overall exposure to vancomycin and incidence of nephrotoxicty were numerically higher in the trough group, suggesting that dosing by AUC may limit exposure without impact on treatment failure.

Structure and dynamics of the staphylococcal pyridoxal 5-phosphate synthase complex reveal transient interactions at the enzyme interface

Infectious diseases are a significant cause of death, and recent studies estimate that common bacterial infectious diseases were responsible for 13.6% of all global deaths in 2019. Among the most significant bacterial pathogens is Staphylococcus aureus, accounting for more than 1.1 million deaths worldwide in 2019. Vitamin biosynthesis has been proposed as a promising target for antibacterial therapy. Here, we investigated the biochemical, structural, and dynamic properties of the enzyme complex responsible for vitamin B6 (pyridoxal 5-phosphate, PLP) biosynthesis in S. aureus, which comprises enzymes SaPdx1 and SaPdx2. The crystal structure of the 24-mer complex of SaPdx1-SaPdx2 enzymes indicated that the S. aureus PLP synthase complex forms a highly dynamic assembly with transient interaction between the enzymes. Solution scattering data indicated that SaPdx2 typically binds to SaPdx1 at a substoichiometric ratio. We propose a structure-based view of the PLP synthesis mechanism initiated with the assembly of SaPLP synthase complex that proceeds in a highly dynamic interaction between Pdx1 and Pdx2. This interface interaction can be further explored as a potentially druggable site for the design of new antibiotics.

Multifaceted manifestations: A case report of MRSA pneumonia with sepsis, pyelonephritis, and ileus muscle abscess

Methicillin-resistant staph aureus (MRSA) infections are challenging to treat, and with the emergence of community-associated MRSA (CA-MRSA) strains, early consideration of this pathogen in populations without typical risk factors is critical. Here we present a case of CA-MRSA pneumonia that resulted in Community-acquired pneumonia (CAP) with septic shock, pyelonephritis, and muscle abscess.

Antimicrobial activity and mechanism of anti-MRSA of phloroglucinol derivatives

BACKGROUND

In previous studies, authors have completed the total synthesis of several phloroglucinol natural products and synthesized a series of their derivatives, which were tested with good biological activities.

OBJECTIVES

To discover anti-MRSA lead compound and study their mechanism of action.

METHODS

Phloroglucinol derivatives were tested to investigate their activities against several gram-positive strains including Methicillin-resistant Staphylococcus aureus (MRSA). The mechanism study was conducted by determining extracellular potassium ion concentration, intracellular NADPH oxidase content, SOD activity, ROS amount in MRSA and MRSA survival rate under A5 treatment. The in vitro cytotoxicity test of A5 was conducted.

RESULTS

The activity of monocyclic compounds was stronger than that of bicyclic compounds, and compound A5 showed the best MIC value of 0.98 μg/mL and MBC value of 1.95 μg/mL, which were 4-8 times lower than that of vancomycin. The mechanism study of A5 showed that it achieved anti-MRSA effect through membrane damage, which is proved by increased concentration of extracellular potassium ion after A5 treatment. Another possible mechanism is the over ROS production induced cell death, which is suggested by observed alternation of several reactive oxygen species (ROS) related indicators including NADPH concentration, superoxide dismutase (SOD) activity, ROS content and bacterial survival rate after A5 treatment. The cytotoxicity results in vitro showed that A5 was basically non-toxic to cells.

CONCLUSION

Acylphloroglucinol derivative A5 showed good anti-MRSA activity, possibly via membrane damage and ROS-mediated oxidative stress mechanism. It deserves further exploration to be a potential lead for the development of new anti-MRSA agent.

Short versus long duration of ceftaroline combination therapy and outcomes in persistent or high-grade MRSA bacteremia: A retrospective single-center study

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is associated with high mortality rates. Despite antibiotic therapy, persistent bacteremia is challenging to treat. Combination therapy with ceftaroline has emerged as a potential treatment option; however, the optimal duration and clinical implications after bacteremia clearance are unknown.

METHODS

This retrospective cohort study examined patients with high-grade or persistent MRSA bacteremia who were treated with ceftaroline combination therapy at the University of New Mexico Hospital between January 2014 and June 2021. Patients were categorized into short- (<7 days) or long-duration (≥7 days) groups based on the duration of combination therapy after bacteremia clearance. Outcomes included 30-day all-cause mortality, bacteremia recurrence, post-bacteremia clearance length of stay, and adverse events.

RESULTS

A total of 32 patients were included in this study. The most common sources of bacteremia were bone/joint and endovascular (28.1%, 9/32 each). The median duration of combination therapy after clearance was seven days (IQR 2.8, 11). Patients in the long-duration group had a lower Charlson comorbidity index (1.0 vs 5.5, p = 0.017) than those in the short-duration group. After adjusting for confounders, there was no significant difference in the 30-day all-cause mortality between the groups (AOR 0.17, 95% CI 0.007-1.85, p = 0.18). No association was found between combination therapy duration and recurrence (OR 2.53, 95% CI 0.19-inf, p = 0.24) or adverse drug events (OR 3.46, 95% CI 0.39-74.86, p = 0.31). After controlling for total hospital length of stay, there was no significant difference in the post-bacteremia clearance length of stay between the two groups (p = 0.37).

CONCLUSIONS

Prolonging ceftaroline combination therapy after bacteremia clearance did not significantly improve outcomes in patients with persistent or high-grade MRSA bacteremia. The limitations of this study warrant cautious interpretation of its results. Larger studies are needed to determine the optimal duration and role of combination therapy for this difficult-to-treat infection.

Optimization of Dendritic Polypeptide Delivery System for Antisense Antibacterial Agents Targeting ftsZ

There is an urgent requirement for a novel treatment strategy for drug-resistant Staphylococcus aureus (S. aureus) infection. Antisense antimicrobials are promising antimicrobials, and efficient drug delivery systems are necessary for the further development of antisense antimicrobials. To develop new antisense drugs and further improve delivery efficiency and safety, we designed and screened new antisense sequences and optimized dendritic polypeptide nanoparticles (DP-AD) discovered in previous studies. The N/P ratio is optimized from 8:1 to 6:1, and the positive charge number of the optimized DP-AD is studied comprehensively. The results show that the N/P ratio and positive charge number have no significant effect on the particle size distribution and transport efficiency of DP-AD. Reducing the N/P ratio can significantly reduce the cytotoxicity of DP-AD, but it does not affect its delivery efficiency and antibacterial activity. However, in drug-resistant strains, the antibacterial activity of DP-AD76:1 with 10 positive charges is higher than that of DP-AD86:1 with 8 positive charges. Our research discovered a novel ASOs targeting ftsZ and concluded that DP-AD76:1 with 10 positive charges was the optimal choice at the current stage, which provided a promising strategy for the treatment of drug-resistant S. aureus.

Silver Nanoparticles Encapped by Dihydromyricetin: Optimization of Green Synthesis, Characterization, Toxicity, and Anti-MRSA Infection Activities for Zebrafish (Danio rerio)

To achieve the environmentally friendly and rapid green synthesis of efficient and stable AgNPs for drug-resistant bacterial infection, this study optimized the green synthesis process of silver nanoparticles (AgNPs) using Dihydromyricetin (DMY). Then, we assessed the impact of AgNPs on zebrafish embryo development, as well as their therapeutic efficacy on zebrafish infected with Methicillin-resistant Staphylococcus aureus (MRSA). Transmission electron microscopy (TEM) and dynamic light-scattering (DLS) analyses revealed that AgNPs possessed an average size of 23.6 nm, a polymer dispersity index (PDI) of 0.197 ± 0.0196, and a zeta potential of -18.1 ± 1.18 mV. Compared to other published green synthesis products, the optimized DMY-AgNPs exhibited smaller sizes, narrower size distributions, and enhanced stability. Furthermore, the minimum concentration of DMY-AgNPs required to affect zebrafish hatching and survival was determined to be 25.0 μg/mL, indicating the low toxicity of DMY-AgNPs. Following a 5-day feeding regimen with DMY-AgNP-containing food, significant improvements were observed in the recovery of the gills, intestines, and livers in MRSA-infected zebrafish. These results suggested that optimized DMY-AgNPs hold promise for application in aquacultures and offer potential for further clinical use against drug-resistant bacteria.

Acquired Immunodeficiency Syndrome (AIDS)-Related Kaposi's Sarcoma in Conjunction With Methicillin-Resistant Staphylococcus aureus (MRSA) and May-Thurner Syndrome

A 34-year-old male with a history of peripheral vascular disease and multifactorial anemia presented with red blotches on his face, trunk, and extremities, multiple large bumps prominent on the lower extremities that burst at times with yellow pus and blood, swelling in the ankles, extremely dry feet, a chronic ulcer on the foot, and a dry, flaky, and irritated left middle finger. The patient was human immunodeficiency virus (HIV) positive, viral load undetectable. Endovenous laser ablation therapy was performed to correct venous insufficiency. A balloon was placed in the common iliac vein to treat May-Thurner syndrome. The bumps on the lower extremities were biopsied and found to be Kaposi's sarcoma (KS) and were removed by both wide excisions and shave removals, and further treatment with doxorubicin was performed successfully. The foot ulcer was found to be positive for methicillin-resistant Staphylococcus aureus (MRSA) and was treated with sulfamethoxazole-trimethoprim, metronidazole, and a chlorhexidine topical liquid. The patient noted that the treatments on his leg were working very well, and he was clearing up.

Discovery of a novel class of rosmarinic acid derivatives as antibacterial agents: Synthesis, structure-activity relationship and mechanism of action

Twenty-seven rosmarinic acid derivatives were synthesized, among which compound RA-N8 exhibited the most potent antibacterial ability. The minimum inhibition concentration of RA-N8 against both S. aureus (ATCC 29213) and MRSA (ATCC BAA41 and ATCC 43300) was found to be 6 μg/mL, and RA-N8 killed E. coli (ATCC 25922) at 3 μg/mL in the presence of polymyxin B nonapeptide (PMBN) which increased the permeability of E. coli. RA-N8 exhibited a weak hemolytic effect at the minimum inhibitory concentration. SYTOX Green assay, SEM, and LIVE/DEAD fluorescence staining assay proved that the mode of action of RA-N8 is targeting bacterial cell membranes. Furthermore, no resistance in wildtype S. aureus developed after incubation with RA-N8 for 20 passages. Cytotoxicity studies further demonstrated that RA-N8 is non-toxic to the human normal cell line (HFF1). RA-N8 also exerted potent inhibitory ability against biofilm formation of S. aureus and even collapsed the shaped biofilm.

Prevalence, antimicrobial resistance, and genetic lineages of nasal Staphylococcus aureus among medical students at a Spanish University: detection of the MSSA-CC398-IEC-type-C subclade

Medical students could be a potential source of Staphylococcus aureus transmission to patients. This cross-sectional study involved samples collected from both nasal nostrils. Samples were processed for S. aureus recovery; the antimicrobial resistance (AMR) phenotype was determined by disc diffusion assays and the spa types and AMR genotypes by PCR/sequencing. A structured questionnaire was administered to students to collate data related to potential risk factors of nasal colonization. Ninety-eight students were included, 50 % were colonized by S. aureus and 12.2 % by MRSA. The mecA gene was detected in all MRSA isolates. The MSSA-CC398-IEC-type C lineage was found among 16.3 % of nasal carriers, of which t571 was the predominant spa-type. MRSA isolates were ascribed to spa types t2226 (CC5, 12 isolates) and t3444 (new spa type, 1 isolate). All MRSA were multi-drug resistant and MSSA were predominantly resistant to erythromycin-clindamycin (inducible-type, mediated by ermT gene). High rates of S. aureus and MRSA nasal carriages were observed in this study. The predominance of the CC398 lineage among MSSA (emergent invasive lineage) represent a relevant finding of public health concern. The role of medical students as potential source of MRSA and MSSA-CC398 transmissions in hospital and community needs to be elucidated in detail.

Epidemiology and Management of Infections in Liver Transplant Recipients

Background: Improvements in liver transplant (LT) outcomes are attributed to advances in surgical techniques, use of potent immunosuppressants, and rigorous pre-LT testing. Despite these improvements, post-LT infections remain the most common complication in this population. Bacteria constitute the most common infectious agents, while fungal and viral infections are also frequently encountered. Multi-drug-resistant bacterial infections develop because of polymicrobial overuse and prolonged hospital stays. Immediate post-LT infections are commonly caused by viruses. Conclusions: Appropriate vaccination, screening of both donor and recipients before LT and antiviral prophylaxis in high-risk individuals are recommended. Antimicrobial drug resistance is common in high-risk LT and associated with poor outcomes; epidemiology and management of these cases is discussed. Additionally, we also discuss the effect of coronavirus disease 2019 (COVID-19) infection and monkeypox in the LT population.

Enzyme-triggered on-demand release of a H2O2-self-supplying CuO2@Fe3O4 nanoagent for enhanced chemodyamic antimicrobial therapy and wound healing

Nanoagents for chemodynamic therapy (CDT) hold a promising future in the field of antimicrobials, especially copper peroxide (CuO2) (CP) nanomaterials which have garnered significant attention due to their ability to self-supply H2O2. Nevertheless, the poor stability of CuO2 remains a critical challenge which restricts its practical application in the antibacterial field. In this study, an advanced nano-antimicrobial system HA-CP@Fe3O4 with enzyme-responsive properties is developed by coating hyaluronic acid (HA) on CuO2-loaded iron tetraoxide nanoparticles. The coating of HA not only stabilizes the CuO2 nanomaterials but also provides responsiveness towards the enzyme hyaluronidase, which is typically secreted by some bacteria. The outer layer of HA in HA-CP@Fe3O4 undergoes decomposition in the presence of hyaluronidase-secreting bacteria, resulting in the release of CuO2@Fe3O4. The released CuO2@Fe3O4 then self-supplies H2O2 and generates reactive oxygen species (ROS) within the infected microenvironment through Fenton and Russell effects, to ultimately achieve effective and precise antimicrobial activity. Simultaneously, the magnetic property provided by Fe3O4 allows the substance to be directed towards the infection site. Both in vitro and in vivo tests demonstrated that HA-CP@Fe3O4 exhibited excellent antimicrobial capabilities at low concentration (30 μg mL-1), exceptional biocompatibility and the ability to accelerate wound healing. The findings of this work offer a new and promising approach for targeted and precise CDT.

Community-acquired multidrug-resistant pneumonia, bacteraemia, and infective endocarditis: A case report

BACKGROUND

The prevalence of multidrug-resistant (MDR) bacteria has increased globally, with extensive drug-resistant (XDR) bacteria posing a threat to patients.

CASE SUMMARY

This case report describes a young man admitted for suspected tropical fever infections who experienced rapid deterioration in health. Despite negative results for tropical fever infections, he had neutrophilic leucocytosis, acute kidney injury, and chest imaging findings suggestive of bilateral consolidations. On day two, he was diagnosed with infective endocarditis with possible rheumatic heart disease and MDR methicillin-resistant Staphylococcus aureus bacteraemia, and community-acquired pneumonia. Despite treatment with broad-spectrum antibiotics, he did not respond and succumbed to death on day five.

CONCLUSION

This case highlights that clinicians/public should be aware of MDR community-acquired pneumonia, bacteraemia, and endocarditis which ultimately culminate in high rates of morbidity and mortality. Early identification of pathogenic strain and prompt antibiotic treatment are a mainstay for the management and prevention of early fatalities. Simultaneously, route cause analysis of community-acquired MDR/XDR pathogens is a global need.

The Synthetic Peptide LyeTx I mn∆K, Derived from Lycosa erythrognatha Spider Toxin, Is Active against Methicillin-Resistant Staphylococcus aureus (MRSA) In Vitro and In Vivo

The urgent global health challenge posed by methicillin-resistant Staphylococcus aureus (MRSA) infections demands effective solutions. Antimicrobial peptides (AMPs) represent promising tools of research of new antibacterial agents and LyeTx I mn∆K, a short synthetic peptide based on the Lycosa erythrognatha spider venom, is a good representative. This study focused on analyzing the antimicrobial activities of LyeTx I mn∆K, including minimum inhibitory and bactericidal concentrations, synergy and resensitization assays, lysis activity, the effect on biofilm, and the bacterial death curve in MRSA. Additionally, its characterization was conducted through isothermal titration calorimetry, dynamic light scattering, calcein release, and finally, efficacy in a mice wound model. The peptide demonstrates remarkable efficacy against planktonic cells (MIC 8-16 µM) and biofilms (>30% of inhibition) of MRSA, and outperforms vancomycin in terms of rapid bactericidal action and anti-biofilm effects. The mechanism involves significant membrane damage. Interactions with bacterial model membranes, including those with lysylphosphatidylglycerol (LysylPOPG) modifications, highlight the versatility and selectivity of this compound. Also, the peptide has the ability to sensitize resistant bacteria to conventional antibiotics, showing potential for combinatory therapy. Furthermore, using an in vivo model, this study showed that a formulated gel containing the peptide proved superior to vancomycin in treating MRSA-induced wounds in mice. Together, the results highlight LyeTx I mnΔK as a promising prototype for the development of effective therapeutic strategies against superficial MRSA infections.

Epidemiologic analysis of antimicrobial resistance in hospital departments in China from 2022 to 2023

Bacterial drug resistance monitoring in hospitals is a crucial aspect of healthcare management and a growing concern worldwide. In this study, we analysed the bacterial drug resistance surveillance in our hospital from 2022 Q1 to 2023 Q2. The main sampling sources were respiratory, blood, and urine-based, and the main clinical infections were respiratory and genitourinary in nature. Specimens were inoculated and cultured; bacterial strains were isolated using a VITEK® 2 Compact 60-card automatic microorganism identifier (bioMerieux, Paris, France) and their matching identification cards were identified, and manual tests were supplemented for strain identification. The most common Gram-positive bacteria detected were Staphylococcus aureus, followed by Enterococcus faecalis (E. faecalis), Staphylococcus epidermidis (S. epidermidis), and Staphylococcus haemolyticus (S. haemolyticus). The most common Gram-negative bacteria detected were Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa. The most prevalent multidrug-resistant bacteria were those producing extended-spectrum beta-lactamases, followed by methicillin-resistant Staphylococcus aureus, followed by carbapenem-resistant Enterobacterales. This study suggests that the prevention and control of infections in the respiratory and genitourinary systems should be the focus of anti-infective work and that the use of antimicrobials should be reduced and regulated to prevent the emergence and spread of resistant bacteria.

The Changing Epidemiology and Antimicrobial Susceptibility of Staphylococcus aureus Isolated from Blood Cultures in a University Hospital from Argentina

Staphylococcus aureus bacteremia (SAB) is one of the most common serious bacterial infections worldwide. In this study, we demonstrated changes in SAB epidemiology in an Argentinean University Hospital during an 8-year period (2009-2016). A total of 326 S. aureus clinical isolates were recovered in three periods: P1: 2009-2010, P2: 2012-2014, and P3: 2015-2016. Among these, 127 were methicillin-resistant S. aureus (MRSA) and were characterized by phenotypic and molecular methods. We hereby report a significant decline in multiple drug resistance among MRSA isolates associated with an increase in SCCmec IV between the three periods. A diversity of MRSA-IV clones (mainly ST30-MRSA-IV, ST5-MRSA-IV, and ST8-MRSA-IV) replaced between 2009 and 2016 the previous prevalent MRSA clone causing bloodstream infections at this hospital (ST5-MRSA-I). MRSA population structure continued to diversify between P2 and P3. Notably, ST8-MRSA-IV-t008 related to USA300 was first detected during P2, and ST8-MRSA-IV together with ST30-MRSA-IV related to the Southwest Pacific clone were the more prevalent MRSA genotypes circulating during P3.

Efficacy and clinical potential of phage therapy in treating methicillin-resistant Staphylococcus aureus (MRSA) infections: A review

Staphylococcus aureus infections have already presented a substantial public health challenge, encompassing different clinical manifestations, ranging from bacteremia to sepsis and multi-organ failures. Among these infections, methicillin-resistant S. aureus (MRSA) is particularly alarming due to its well-documented resistance to multiple classes of antibiotics, contributing significantly to global mortality rates. Consequently, the urgent need for effective treatment options has prompted a growing interest in exploring phage therapy as a potential non-antibiotic treatment against MRSA infections. Phages represent a class of highly specific bacterial viruses known for their ability to infect certain bacterial strains. This review paper explores the clinical potential of phages as a treatment for MRSA infections due to their low toxicity and auto-dosing capabilities. The paper also discusses the synergistic effect of phage-antibiotic combination (PAC) and the promising results from in vitro and animal model studies, which could lead to extensive human clinical trials. However, clinicians need to establish and adhere to standard protocols governing phage administration and implementation. Prominent clinical trials are needed to develop and advance phage therapy as a non-antibiotic therapy intervention, meeting regulatory guidelines, logistical requirements, and ethical considerations, potentially revolutionizing the treatment of MRSA infections.

In Vitro and Ex Vivo Investigation of the Antibacterial Effects of Methylene Blue against Methicillin-Resistant Staphylococcus aureus

Methylene blue (MB) is a water-soluble dye that has a number of medical applications. Methicillin-resistant Staphylococcus aureus (MRSA) was selected as a subject for research due to the numerous serious clinical diseases it might cause and because there is a significant global resistance challenge. Our main goal was to determine and analyze the antibacterial effects of MB against S. aureus both in vitro and ex vivo to enhance treatment options. A total of 104 MRSA isolates recovered from various clinical specimens were included in this study. Minimum inhibitory concentration (MIC) values of MB against MRSA isolates were determined by the agar dilution method. One randomly selected MRSA isolate and a methicillin-susceptible S. aureus strain (S. aureus ATCC 25923) were employed for further evaluation of the antibacterial effects of MB in in vitro and ex vivo time-kill assays. A disc diffusion method-based MB + antibiotic synergy assay was performed to analyze the subinhibitory effects of MB on ten isolates. MICs of MB against 104 MRSA isolates, detected by the agar dilution method, ranged between 16 and 64 µg/mL. MB concentrations of 4 and 16 µg/mL showed a bactericidal effect at 24 h in the ex vivo time-kill assays and in vitro time-kill assays, respectively. We observed a significant synergy between cefoxitin and methylene blue at a concentration of 1-2 μg/mL in two (20%) test isolates. Employing MB, which has well-defined pharmacokinetics, bioavailability, and safety profiles, for the treatment of MRSA infections and nasal decolonization could be a good strategy.

Efficacy and Safety of Oral and IV Levonadifloxacin Therapy in Management of Bacterial Infections: Findings of a Prospective, Observational, Multi-center, Post-marketing Surveillance Study

Background Antimicrobial resistance by bacteria poses a substantial threat to morbidity and mortality worldwide, and treatment of resistant infections is a challenge for the treating clinician. Levonadifloxacin is a novel broad-spectrum agent belonging to the benzoquinolizine subclass of quinolone, which can be used by both oral and intravenous administration for the treatment of infections caused by gram-positive organisms, including methicillin-resistant Staphylococcus aureus (MRSA). Patients and methods This prescription event monitoring study captured data from 1266 patients receiving levonadifloxacin (oral and/or IV) in a real-world setting to assess the safety and efficacy in the treatment of various bacterial infections. The duration of the study was 18 months. Study outcomes were clinical success and microbial success at the end of therapy. Global assessments were done for safety and efficacy at the end of therapy using a 5-point Likert scale (excellent, very good, good, satisfactory, and poor). Results The mean (median) duration of therapy was 7.2 (7.0) days, with a median time to clinical improvement of four days. Oral therapy was administered to 224 patients; 940 received IV, and 102 received IV followed by oral therapy. Patients were prescribed levonadifloxacin for gram-positive infections, skin and soft tissue infections, diabetic foot infections, septicemia, catheter-related blood-stream infections, bone and joint infections, febrile neutropenia, and respiratory infections, including COVID-19 pneumonia. The clinical cure on the eighth day was 95.7%, whereas the microbial success on the eighth day was 93.3% (n=60). For different types of infections, the clinical success rates ranged from 85.2% to 100%. There were only 30 treatment-emergent adverse events reported in 29 patients. Overall, about 95.6% of patients rated the efficacy as good to excellent, whereas only 3.8% of patients rated it satisfactory; for safety, 95.7% of patients rated it as good to excellent, with only 3.9% of patients rated it as satisfactory. Conclusions The excellent safety and efficacy profile of levonadifloxacin, when administered as an oral or intravenous therapy, makes it a desirable treatment modality for the management of various bacterial infections, including those caused by resistant pathogens such as MRSA and quinolone-resistant Staphylococcus aureus (QRSA). Features of levonadifloxacin, such as availability in both IV and oral form, minimal drug-drug interactions, lack of the need to adjust dosages in renal and hepatically impaired patients along with a broad spectrum of coverage, make it a suitable agent that meets several unmet clinical needs of physicians.

Neutrophil-targeted combinatorial nanosystems for suppressing bacteremia-associated hyperinflammation and MRSA infection to improve survival rates

There is currently no specific and effective treatment for bacteremia-mediated sepsis. Hence, this study engineered a combinatorial nanosystem containing neutrophil-targeted roflumilast-loaded nanocarriers and non-targeted fusidic acid-loaded nanoparticles to enable the dual mitigation of bacteremia-associated inflammation and methicillin-resistant Staphylococcus aureus (MRSA) infection. The targeted nanoparticles were developed by conjugating anti-lymphocyte antigen 6 complex locus G6D (Ly6G) antibody fragment on the nanoparticulate surface. The particle size and zeta potential of the as-prepared nanosystem were about 200 nm and -25 mV, respectively. The antibody-conjugated nanoparticles showed a three-fold increase in neutrophil internalization compared to the unfunctionalized nanoparticles. As a selective phosphodiesterase (PDE) 4 inhibitor, the roflumilast in the nanocarriers largely inhibited cytokine/chemokine release from the activated neutrophils. The fusidic acid-loaded nanocarriers were vital to eliminate biofilm MRSA colony by 3 log units. The nanoparticles drastically decreased the intracellular bacterial count compared to the free antibiotic. The in vivo mouse bioimaging demonstrated prolonged retention of the nanosystem in the circulation with limited organ distribution and liver metabolism. In the mouse bacteremia model, the multifunctional nanosystem produced a 1‒2 log reduction of MRSA burden in peripheral organs and blood. The functionalized nanosystem arrested the cytokine/chemokine overexpression greater than the unfunctionalized nanocarriers and free drugs. The combinatory nanosystem also extended the median survival time from 50 to 103 h. No toxicity from the nanoformulation was found based on histology and serum biochemistry. Furthermore, our data proved that the active neutrophil targeting by the versatile nanosystem efficiently alleviated MRSA infection and organ dysfunction caused by bacteremia. STATEMENT OF SIGNIFICANCE: Bacteremia-mediated sepsis poses a significant challenge in clinical practice, as there is currently no specific and effective treatment available. In our study, we have developed a novel combinatorial nanosystem to address this issue. Our nanosystem consists of neutrophil-targeted roflumilast-loaded nanocarriers and non-targeted fusidic acid-loaded nanoparticles, enabling the simultaneous mitigation of bacteremia-associated inflammation and MRSA infection. Our nanosystem demonstrated the decreased neutrophil activation, effective inhibition of cytokine release, elimination of MRSA biofilm colonies, and reduced intracellular bacterial counts. In vivo experiments showed prolonged circulation, limited organ distribution, and increased survival rates in a mouse bacteremia model. Importantly, our nanosystem exhibited no toxicity based on comprehensive assessments.

Loratadine Combats Methicillin-Resistant Staphylococcus aureus by Modulating Virulence, Antibiotic Resistance, and Biofilm Genes

Methicillin-resistant Staphylococcus aureus (MRSA) has evolved to become resistant to multiple classes of antibiotics. New antibiotics are costly to develop and deploy, and they have a limited effective lifespan. Antibiotic adjuvants are molecules that potentiate existing antibiotics through nontoxic mechanisms. We previously reported that loratadine, the active ingredient in Claritin, potentiates multiple cell-wall active antibiotics in vitro and disrupts biofilm formation through a hypothesized inhibition of the master regulatory kinase Stk1. Loratadine and oxacillin combined repressed the expression of key antibiotic resistance genes in the bla and mec operons. We hypothesized that additional genes involved in antibiotic resistance, biofilm formation, and other cellular pathways would be modulated when looking transcriptome-wide. To test this, we used RNA-seq to quantify transcript levels and found significant effects in gene expression, including genes controlling virulence, antibiotic resistance, metabolism, transcription (core RNA polymerase subunits and sigma factors), and translation (a plethora of genes encoding ribosomal proteins and elongation factor Tu). We further demonstrated the impacts of these transcriptional effects by investigating loratadine treatment on intracellular ATP levels, persister formation, and biofilm formation and morphology. Loratadine minimized biofilm formation in vitro and enhanced the survival of infected Caenorhabditis elegans. These pleiotropic effects and their demonstrated outcomes on MRSA virulence and survival phenotypes position loratadine as an attractive anti-infective against MRSA.

The Prevalence, Epidemiological, and Molecular Characterization of Methicillin-Resistant Staphylococcus aureus (MRSA) in Macau (2017-2022)

Macau, recognized as a global tourism hub and the world's most densely populated region, provides a unique environment conducive to methicillin-resistant Staphylococcus aureus (MRSA) transmission in healthcare and community settings, posing a significant public health concern both locally and globally. The epidemiology and molecular characteristics of MRSA in the distinct city of Macau remain largely unelucidated. This five-year longitudinal study (2017-2022) examined the local prevalence and molecular typing of MRSA in Macau, with future MRSA type distribution predicted through ARIMA modeling. We subsequently analyzed the epidemiological characteristics of MRSA, including specimen source, clinical department, collection year, season, patient age, sex, and the annual number of tourists. Comprehensive antibiotic resistance profiles of the strains were also assessed. Of 504 clinically isolated S. aureus strains, 183 (36.3%) were identified as MRSA by the cefoxitin disk diffusion method and validated through multi-locus sequence typing (MLST). The MRSA detection rate showed an upward trend, increasing from 30.1% in 2017 to 45.7% in 2022. SCCmec type IV was predominant (28.9%), followed by types II (25.4%), III (22.1%), and V (22.1%). The primary sources of MRSA isolates were sputum (39.2%) and secretions (25.6%). Older age emerged as a risk factor for MRSA infection, whereas no significant associations were found with seasonal variations, gender, or the annual number of tourists. Despite displaying universal resistance to cefoxitin, oxacillin, and benzylpenicillin, MRSA isolates in Macau remained fully sensitive to vancomycin, tigecycline, quinupristin, nitrofurantoin, and linezolid. Continuous surveillance and analysis of MRSA distribution in Macau could provide invaluable insights for the effective management of MRSA prevention and control measures within healthcare settings.

Novel phenylthiazoles with a tert-butyl moiety: promising antimicrobial activity against multidrug-resistant pathogens with enhanced ADME properties

The structure-activity relationship of a new tert-butylphenylthiazole series, with a pyrimidine linker, was investigated. We wished to expand knowledge of this novel class of antibiotics by generating 21 new derivatives bearing ≥2 heteroatoms in their side chains. Their activity was examined against isolates of methicillin-resistant Staphylococcus aureus (MRSA), Clostridium difficile, Escherichia coli, Neisseria gonorrhoeae, and Candida albicans. Two compounds with 1,2-diaminocyclohexane as a nitrogenous side chain showed promising activity against the highly infectious MRSA USA300 strain, with a minimum inhibitory concentration (MIC) of 4 μg mL-1. One of these two compounds demonstrated potent activity against C. difficile, with a MIC of 4 μg mL-1. Moderate activities against a C. difficile strain with a MIC of 8 μg mL-1 were noted. Some new compounds possessed antifungal activity against a wild fluconazole-resistant C. albicans strain, with MIC values of 4-16 μg mL-1. ADME and metabolism-simulation studies were performed for the most promising compound and compared with lead compounds. Our results revealed that one compound possessed greater penetration of bacterial membranes and metabolic resistance, which aided a longer duration of action against MRSA.

A Hybrid Antimicrobial Peptide Targeting Staphylococcus aureus with a Dual Function of Inhibiting Quorum Sensing Signaling and an Antibacterial Effect

Community-associated methicillin-resistant Staphylococcus aureus (MRSA) is now a major cause of bacterial infection. Antivirulence therapy does not stimulate evolution of a pathogen toward a resistant phenotype, providing a novel method to treat infectious diseases. Here, we used a cyclic peptide of CP7, an AIP-III variant that specifically inhibited the virulence and biofilm formation of Staphylococcus aureus (S. aureus) in a nonbiocidal manner, to conjugate with a broad-spectrum antimicrobial peptide (AMP) via two N-termini to obtain a hybrid AMP called CP7-FP13-2. This peptide not only specifically inhibited the production of virulence of S. aureus at low micromolar concentrations but also killed S. aureus, including MRSA, by disrupting the integrity of the bacterial cell membrane. In addition, CP7-FP13-2 inhibited the formation of the S. aureus biofilm and showed good antimicrobial efficacy against the S. aureus-infected Kunming mice model. Therefore, this study provides a promising strategy against the resistance and virulence of S. aureus.

Repurposing of the antimalarial agent tafenoquine to combat MRSA

IMPORTANCE

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