Methicillin-resistant Staphylococcus aureus

ESKAPE in China: epidemiology and characteristics of antibiotic resistance

The escalation of antibiotic resistance and the diminishing antimicrobial pipeline have emerged as significant threats to public health. The ESKAPE pathogens - Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp. - were initially identified as critical multidrug-resistant bacteria, demanding urgently effective therapies. Despite the introduction of various new antibiotics and antibiotic adjuvants, such as innovative β-lactamase inhibitors, these organisms continue to pose substantial therapeutic challenges. People's Republic of China, as a country facing a severe bacterial resistance situation, has undergone a series of changes and findings in recent years in terms of the prevalence, transmission characteristics and resistance mechanisms of antibiotic resistant bacteria. The increasing levels of population mobility have not only shaped the unique characteristics of antibiotic resistance prevalence and transmission within People's Republic of China but have also indirectly reflected global patterns of antibiotic-resistant dissemination. What's more, as a vast nation, People's Republic of China exhibits significant variations in the levels of antibiotic resistance and the prevalence characteristics of antibiotic resistant bacteria across different provinces and regions. In this review, we examine the current epidemiology and characteristics of this important group of bacterial pathogens, delving into relevant mechanisms of resistance to recently introduced antibiotics that impact their clinical utility in China.

The pathogenicity and virulence of the opportunistic pathogen Staphylococcus epidermidis

The pervasive presence of Staphylococcus epidermidis and other coagulase-negative staphylococci on the skin and mucous membranes has long underpinned a casual disregard for the infection risk that these organisms pose to vulnerable patients in healthcare settings. Prior to the recognition of biofilm as an important virulence determinant in S. epidermidis, isolation of this microorganism in diagnostic specimens was often overlooked as clinically insignificant with potential delays in diagnosis and onset of appropriate treatment, contributing to the establishment of chronic infection and increased morbidity or mortality. While impressive progress has been made in our understanding of biofilm mechanisms in this important opportunistic pathogen, research into other virulence determinants has lagged S. aureus. In this review, the broader virulence potential of S. epidermidis including biofilm, toxins, proteases, immune evasion strategies and antibiotic resistance mechanisms is surveyed, together with current and future approaches for improved therapeutic interventions.

Detection of foodborne methicillin-resistant Staphylococcus aureus via fluorescence-encoded microsphere and Argonaute-mediated decoding

Molecular diagnosis of foodborne methicillin-resistant Staphylococcus aureus (MRSA) is crucial for controlling its dissemination and ensuring food safety. However, existing genetic methods are limited by susceptibility to aerosol contamination and restricted to single-gene detection. Herein, a fluorescent biosensor employing fluorescence-encoded microspheres and Argonaute-mediated decoding is developed, enabling ultrasensitive, accurate, and duplex detection of MRSA genes. This assay utilizes a target-triggered polymerization/nicking reaction to cyclically produce specific guide DNA, guiding Argonaute protein to site-specifically cleave the molecular beacon on the microsphere, thereby decoding a fluorescent signal. Notably, the fluorescence-encoded microsphere, designed via on-tetrahedron rolling circle amplification, achieves high fluorescence loadings in a unit area. This biosensor demonstrates simultaneous detection of two unamplified MRSA genes, mecA and femA, at concentrations as low as 0.63 fM and 0.48 fM, respectively. Moreover, the method exhibited excellent recoveries in milk, egg, and pork samples ranging from 73% to 112%, highlighting its practicability in real scenarios.

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

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

Napthalimide-based nuclease inhibitor: A multifunctional therapeutic material to bolster MRSA uptake by macrophage-like cells and mitigate pathogen adhesion on orthopaedic implant

The healthcare burden rendered by methicillin-resistant Staphylococcus aureus (MRSA) warrants the development of therapeutics that offer a distinct benefit in the clinics as compared to conventional antibiotics. The present study describes the potential of napthalimide-based synthetic ligands (C1-C3) as inhibitors of the staphylococcal nuclease known as micrococcal nuclease (MNase), a key virulence factor of the pathogen. Amongst the ligands, the most potent MNase inhibitor C1 rendered non-competitive inhibition, reduced MNase turnover number (Kcat) and catalytic efficiency (Kcat/Km) with an IC50 value of ~950 nM. CD spectroscopy suggested distortion of MNase conformation in presence of C1. Flow cytometry and confocal microscopy indicated that C1 restored the ability of activated THP-1 cells to engulf DNA-entrapped MRSA cells. Interestingly, C1 could inhibit MRSA adhesion onto collagen. For potential application, C1-loaded pluronic F-127 micellar nanocarrier (C1-PMC) was generated, wherein the anti-adhesion activity of the pluronic carrier (PMC) and C1 was harnessed in tandem to deter MRSA cell adhesion onto collagen. MRSA biofilm formation was hindered on C1-PMC-coated titanium (Ti) wire, while eluates from C1-PMC-coated Ti wires were non-toxic to HEK 293, MG-63 and THP-1 cells. The multifunctional C1 provides a blueprint for designing therapeutic materials that hold translational potential for mitigation of MRSA infections.

A bioactive xyloglucan polysaccharide hydrogel mechanically enhanced by Pluronic F127 micelles for promoting chronic wound healing

Chronic wounds represent a formidable global healthcare challenge due to the bacteria infections and uncontrollable inflammation responses, while developing wound healing materials capable of resolving these issues remains a challenge. In this study, we integrated xyloglucan (XG) with Pluronic F127 diacrylate (F127DA)to develop a composite hydrogel for wound healing, where the XG introduced anti-inflammation and anti-bacterial properties to the construct, and F127DA provides the photocurable properties essential for hydrogel formation and robust mechanical characteristics to achieve physical strength that matches tissue regeneration. The material characterizations suggested that XG/F127DA hydrogels had great biostability, blood compatibility and antibacterial effects, which was suitable to be used as a wound healing material. The in vitro analysis by culturing L929 fibroblasts on the hydrogel surface demonstrated that the inclusion of XG could promote the cellular proliferation rate, migration rate, and re-epithelialization-related marker expression, while downregulate the inflammation process. The XG/F127DA hydrogel was further used for the full-thickness skin wound healing test on mice, where the inclusion of XG significantly increased the wound closure rate through reducing the inflammation responses, and promote re-epithelialization and angiogenesis. These results indicated that XG/F127DA hydrogel has great potential to be used for wound healing in future clinical translation.

Conserved moonlighting protein pyruvate dehydrogenase induces robust protection against Staphylococcus aureus infection

Developing an effective Staphylococcus aureus (S. aureus) vaccine has been a challenging endeavor, as demonstrated by numerous failed clinical trials over the years. In this study, we formulated a vaccine containing a highly conserved moonlighting protein, the pyruvate dehydrogenase complex E2 subunit (PDHC), and showed that it induced strong protective immunity against epidemiologically relevant staphylococcal strains in various murine disease models. While antibody responses contributed to bacterial control, they were not essential for protective immunity in the bloodstream infection model. Conversely, vaccine-induced systemic immunity relied on γδ T cells. It has been suggested that prior S. aureus exposure may contribute to the reduction of vaccine efficacy. However, PDHC-induced protective immunity still facilitated bacterial clearance in mice previously exposed to S. aureus. Collectively, our findings indicate that PDHC is a promising serotype-independent vaccine candidate effective against both methicillin-sensitive and methicillin-resistant S. aureus isolates.

Nitrogen Vacancy Modulation of Tungsten Nitride Peroxidase-Mimetic Activity for Bacterial Infection Therapy

Bacterial infections claim millions of lives every year, with the escalating menace of microbial antibiotic resistance compounding this global crisis. Nanozymes, poised as prospective substitutes for antibiotics, present a significant frontier in antibacterial therapy, yet their precise enzymatic origins remain elusive. With the continuous development of nanozymes, the applications of elemental N-modulated nanozymes have spanned multiple fields, including sensing and detection, infection therapy, cancer treatment, and pollutant degradation. The introduction of nitrogen into nanozymes not only broadens their application range but also holds significant importance for the design of catalysts in biomedical research. The synergistic interplay between W and N induces pivotal alterations in electronic configurations, endowing tungsten nitride (WN) with a peroxidase-like functionality. Furthermore, the introduction of N vacancies augments the nanozyme activity, thus amplifying the catalytic potential of WN nanostructures. Rigorous theoretical modeling and empirical validation corroborate the genesis of the enzyme activity. The meticulously engineered WN nanoflower architecture exhibits an exceptional ability in traversing bacterial surfaces, exerting potent bactericidal effects through direct physical interactions. Additionally, the topological intricacies of these nanostructures facilitate precise targeting of generated radicals on bacterial surfaces, culminating in exceptional bactericidal efficacy against both Gram-negative and Gram-positive bacterial strains along with notable inhibition of bacterial biofilm formation. Importantly, assessments using a skin infection model underscore the proficiency of WN nanoflowers in effectively clearing bacterial infections and fostering wound healing. This pioneering research illuminates the realm of pseudoenzyme activity and bacterial capture-killing strategies, promising a fertile ground for the development of innovative, high-performance artificial peroxidases.

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

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

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

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

A MRSA mystery: how PBP4 and cyclic-di-AMP join forces against β-lactam antibiotics

The high-level resistance to next-generation β-lactams frequently found in Staphylococcus aureus isolates lacking mec, which encodes the transpeptidase PBP2a traditionally associated with methicillin-resistant Staphylococcus aureus (MRSA), has remained incompletely understood for decades. A new study by Lai et al. found that the co-occurrence of mutations in pbp4 and gdpP, which respectively cause increased PBP4-mediated cell wall crosslinking and elevated cyclic-di-AMP levels, produces synergistic β-lactam resistance rivaling that of PBP2a-producing MRSA (L.-Y. Lai, N. Satishkumar, S. Cardozo, V. Hemmadi, et al., mBio 15:e02889-23. 2024, https://doi.org/10.1128/mbio.02889-23). The combined mutations are sufficient to explain the high-level β-lactam resistance of some mec-lacking strains, but the mechanism of synergy remains elusive and an avenue for further research. Importantly, the authors establish that co-occurrence of these mutations leads to antibiotic therapy failure in a Caenorhabditis elegans infection model. These results underscore the need to consider this unique and novel β-lactam resistance mechanism during the clinical diagnosis of MRSA, rather than relying on mec as a diagnostic.

Isolation and identification of antimicrobial multicyclic terpenoids from the medicinal plant Salvia officinalis and development of a formulation against clinical Staphylococcus aureus strains

Staphylococcus aureus, particularly multi-drug resistant strains, presents significant challenges in dairy farming due to its role in causing bovine mastitis, which leads to substantial economic losses and limited treatment options. Seeking alternative therapies, we investigated the potential of a topical formulation derived from the medicinal herb Salvia officinalis to combat S. aureus growth and biofilms associated with bovine mastitis. Through systematic extraction in different solvents and fractionation by column chromatography, we isolated and identified three key multicyclic terpenoids-ferruginol, sugiol, and sclareol-exhibiting significant antimicrobial activity. The formulation effectively inhibited biofilm formation, with minimum inhibitory concentration (MIC) values ranging from 0.09 to 0.74 mg ml-1 against clinical S. aureus strains, comparable to or lower than those of the pure compounds. Moreover, it displayed robust anti-adhesive properties, reducing biofilm formation by 20%-79% at subinhibitory concentrations. Furthermore, the formulation successfully disrupted pre-existing biofilms, achieving reductions ranging from 30% to 82%. Cytotoxicity assays confirmed the safety of the formulation on mammary epithelial cells, with cell viability maintained at 100% at MIC. Our findings underscore the therapeutic potential of Sa. officinalis-derived compounds in managing bovine mastitis caused by S. aureus, emphasizing their antimicrobial efficacy and safety profile.

Integrating research on bacterial pathogens and commensals to fight infections-an ecological perspective

The incidence of antibiotic-resistant bacterial infections is increasing, and development of new antibiotics has been deprioritised by the pharmaceutical industry. Interdisciplinary research approaches, based on the ecological principles of bacterial fitness, competition, and transmission, could open new avenues to combat antibiotic-resistant infections. Many facultative bacterial pathogens use human mucosal surfaces as their major reservoirs and induce infectious diseases to aid their lateral transmission to new host organisms under some pathological states of the microbiome and host. Beneficial bacterial commensals can outcompete specific pathogens, thereby lowering the capacity of the pathogens to spread and cause serious infections. Despite the clinical relevance, however, the understanding of commensal-pathogen interactions in their natural habitats remains poor. In this Personal View, we highlight directions to intensify research on the interactions between bacterial pathogens and commensals in the context of human microbiomes and host biology that can lead to the development of innovative and sustainable ways of preventing and treating infectious diseases.

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.

Synthesis and Antibacterial Evaluation of Novel Psoralen Derivatives against Methicillin-Resistant Staphylococcus aureus (MRSA)

Today, the bacterial infections caused by multidrug-resistant pathogens seriously threaten human health. Thereby, there is an urgent need to discover antibacterial drugs with novel mechanism. Here, novel psoralen derivatives had been designed and synthesized by a scaffold hopping strategy. Among these targeted twenty-five compounds, compound ZM631 showed the best antibacterial activity against methicillin-resistant S. aureus (MRSA) with the low MIC of 1 μg/mL which is 2-fold more active than that of the positive drug gepotidacin. Molecular docking study revealed that compound ZM631 fitted well in the active pockets of bacterial S. aureus DNA gyrase and formed a key hydrogen bond binding with the residue ASP-1083. These findings demonstrated that the psoralen scaffold could serve as an antibacterial lead compound for further drug development against multidrug-resistant bacterial infections.

Outpatient parenteral antimicrobial therapy (OPAT) in Germany: insights and clinical outcomes from the K-APAT cohort study

PURPOSE

Outpatient parenteral antimicrobial therapy (OPAT) offers several key advantages, including enhanced patient quality of life, reduced healthcare costs, and a potential reduction of nosocomial infections. It is acknowledged for its safety and effectiveness. This study provides the first systematic clinical data for Germany, where OPAT has not yet been widely adopted. The aim is to establish a foundational reference point for further research and integration of OPAT into the German healthcare system.

METHODS

This prospective observational study descriptively analyses data obtained from a cohort of patients receiving OPAT. Both in- and outpatients from all medical specialties could be recruited. Patients administered the anti-infective medications themselves at home using elastomeric pumps.

RESULTS

77 patients received OPAT, with a median duration of 15 days and saving 1782 inpatient days. The most frequently treated entities were orthopaedic infections (n = 20, 26%), S. aureus bloodstream infection (n = 16, 21%) and infectious endocarditis (n = 11, 14%). The most frequently applied drugs were flucloxacillin (n = 18, 23%), penicillin G (n = 13, 17%) and ceftriaxone (n = 10; 13%). Only 5% of patients (n = 4) reported to have missed more than one outpatient dose (max. 3 per patient). Only one catheter-related adverse event required medical intervention, and there were no catheter-related infections.

CONCLUSION

The study demonstrates that OPAT can be safely conducted in Germany. In preparation for its broader implementation, crucial next steps include creating medical guidelines, fostering interdisciplinary and inter-sectoral communication, as well as creating financial and structural regulations that facilitate and encourage the adoption of OPAT.

TRIAL REGISTRATION NUMBER

NCT04002453.

Adherence to and clinical utility of "quality indicators" for Staphylococcus aureus bacteremia: a retrospective, multicenter study

BACKGROUND

We aimed to improve the prognosis, treatment, and management of Staphylococcus aureus bacteremia (SAB) by evaluating the association between adherence to quality indicators (QIs) and clinical outcomes in patients with their clinical outcomes.

METHODS

We retrospectively collected clinical and microbiological data on hospitalized patients with SAB from 14 hospitals (three with >  600, two with 401-600, five with 201-400, and four with ≤ 200 beds) in Japan from January to December 2022. The SAB management quality was evaluated using the SAB-QI score (ranging from 0 to 13 points), which consists of 13 QIs (grouped into five categories) based on previous literature.

RESULTS

Of the 4,448 positive blood culture episodes, 289 patients with SAB (6.5%) were enrolled. The SAB-QI scores ranged from 3 to 13, with a median score of 9 points. The SAB-QI score was highest in middle-sized hospitals with 401-600 beds. Adherence to each of the four QI categories (blood culture, echocardiography, source control, and antibiotic treatment) was significantly higher in survived cases than in fatal cases. Kaplan-Meier curves with log-rank tests demonstrated that higher adherence to SAB-QIs indicated a better prognosis. Logistic regression analysis revealed that age, methicillin resistance, multiple comorbidities (≥ 2), and low SAB-QI score were significantly associated with 30-day mortality in patients with SAB.

CONCLUSIONS

Our study highlights that greater adherence to the SAB-QIs correlates with improved patient outcomes. Management of patients with SAB should follow these recommended indicators to maintain the quality of care, especially for patients with poor prognosticators.

On-Site Inactivation for Disinfection of Antibiotic-Resistant Bacteria in Hospital Effluent by UV and UV-LED

The problem of antimicrobial resistance (AMR) is not limited to the medical field but is also becoming prevalent on a global scale in the environmental field. Environmental water pollution caused by the discharge of wastewater into aquatic environments has caused concern in the context of the sustainable development of modern society. However, there have been few studies focused on the treatment of hospital wastewater, and the potential consequences of this remain unknown. This study evaluated the efficacy of the inactivation of antimicrobial-resistant bacteria (AMRB) and antimicrobial resistance genes (AMRGs) in model wastewater treatment plant (WWTP) wastewater and hospital effluent based on direct ultraviolet (UV) light irradiation provided by a conventional mercury lamp with a peak wavelength of 254 nm and an ultraviolet light-emitting diode (UV-LED) with a peak emission of 280 nm under test conditions in which the irradiance of both was adjusted to the same intensity. The overall results indicated that both UV- and UV-LED-mediated disinfection effectively inactivated the AMRB in both wastewater types (>99.9% after 1-3 min of UV and 3 min of UV-LED treatment). Additionally, AMRGs were also removed (0.2-1.4 log10 for UV 254 nm and 0.1-1.3 log10 for UV 280 nm), and notably, there was no statistically significant decrease (p < 0.05) in the AMRGs between the UV and UV-LED treatments. The results of this study highlight the importance of utilizing a local inactivation treatment directly for wastewater generated by a hospital prior to its flow into a WWTP as sewage. Although additional disinfection treatment at the WWTP is likely necessary to remove the entire quantity of AMRB and AMRGs, the present study contributes to a significant reduction in the loads of WWTP and urgent prevention of the spread of infectious diseases, thus alleviating the potential threat to the environment and human health risks associated with AMR problems.

Aerosol-Mediated Spread of Antibiotic Resistance Genes: Biomonitoring Indoor and Outdoor Environments

Antimicrobial resistance (AMR) has emerged as a conspicuous global public health threat. The World Health Organization (WHO) has launched the "One-Health" approach, which encourages the assessment of antibiotic resistance genes (ARGs) within an environment to constrain and alleviate the development of AMR. The prolonged use and overuse of antibiotics in treating human and veterinary illnesses, and the inability of wastewater treatment plants to remove them have resulted in elevated concentrations of these metabolites in the surroundings. Microbes residing within these settings acquire resistance under selective pressure and circulate between the air-land interface. Initial evidence on the indoor environments of wastewater treatment plants, hospitals, and livestock-rearing facilities as channels of AMR has been documented. Long- and short-range transport in a downwind direction disseminate aerosols within urban communities. Inhalation of such aerosols poses a considerable occupational and public health risk. The horizontal gene transfer (HGT) is another plausible route of AMR spread. The characterization of ARGs in the atmosphere therefore calls for cutting-edge research. In the present review, we provide a succinct summary of the studies that demonstrated aerosols as a media of AMR transport in the atmosphere, strengthening the need to biomonitor these pernicious pollutants. This review will be a useful resource for environmental researchers, healthcare practitioners, and policymakers to issue related health advisories.

The two-component regulatory systems GraRS and SrrAB mediate Staphylococcus aureus susceptibility to Pep5 produced by clinical isolate of Staphylococcus epidermidis

Staphylococcus aureus is a common bacterium on the skin and in the nose that sometimes causes severe illness. Bacteriocins, antimicrobial peptides, or proteins produced by bacteria are candidates for the treatment of S. aureus infection. In this study, we found that a clinical Staphylococcus epidermidis strain, KSE112, produced the lantibiotic Pep5, which showed anti-S. aureus activity. The complete nucleotide sequence of the Pep5-encoding plasmid was determined. Several S. aureus two-component regulatory systems (TCSs) are known to be involved in bacteriocin susceptibility. Therefore, susceptibility tests were performed using TCS-inactivated S. aureus mutants to determine which TCS is responsible for Pep5 susceptibility; the ΔgraRS mutant exhibited increased susceptibility to Pep5, while the ΔsrrAB mutant exhibited decreased susceptibility. GraRS is known to regulate dltABCD and mprF in concert with vraFG, and Pep5 susceptibility was significantly increased in the ΔdltABCD, ΔmprF, and ΔvraFG mutants. Regarding the ΔsrrAB mutant, cross-resistance to aminoglycosides was observed. As aminoglycoside activity is known to be affected by aerobic respiration, we focused on qoxABCD and cydAB, which are quinol oxidase genes that are necessary for aerobic respiration and have downregulated the expression in the ΔsrrAB mutant. We constructed ΔqoxABCD and ΔcydAB mutants and found that qoxABCD inactivation decreased susceptibility to Pep5 and aminoglycosides. These results indicate that reduced aerobic respiration due to the reduced qoxABCD expression in the ΔsrrAB mutant decreased Pep5 activity.IMPORTANCEThe emergence of drug-resistant bacteria, including MRSA, is a severe health problem worldwide. Thus, the development of novel antimicrobial agents, including bacteriocins, is needed. In this report, we found a Pep5-producing strain with anti-S. aureus activity. We determined the complete sequence of the Pep5-encoding plasmid for the first time. However, in S. aureus, GraRS and its effectors conferred decreased susceptibility to Pep5. We also revealed that another TCS, SrrAB, affects susceptibility Pep5 and other lantibiotics by controlling aerobic respiration. In our study, we investigated the efficacy of Pep5 against S. aureus and other Gram-positive bacteria and revealed that respiratory constancy regulated by TCS is required for the antimicrobial activity of nisin, nukacin, and Pep5. These findings provide important information for the clinical application of bacteriocins and suggest that they have different properties among similar pore-forming lantibiotics.

Seizing the Hidden Assassin: Current Detection Strategies for Staphylococcus aureus and Methicillin-Resistant S. aureus

Staphylococcus aureus (S. aureus) is a kind of pathogenic bacteria which can lead to food poisoning, hospital, and community infections. S. aureus and methicillin-resistant S. aureus (MRSA) have become headaches for public health worldwide. Therefore, strengthening the detection of S. aureus and MRSA is a critical step to prevent and control its spread and infection. This review summarized multiple detection methods (electrochemical, optical, and other biosensors) for sensitive and efficient detection of nonresistant and resistant S. aureus. First, we have introduced the principle and methods of detection platform for S. aureus and MRSA. We also contrasted various detection strategies. Finally, the current situation and prospect of S. aureus and MRSA detection in the future are explored in depth, and its development direction of detection methods is also predicted. In this review, we found that although biosensors have shown tremendous brilliance in the field of monitoring, they are currently in the experimental stage. It can be certain that we are very close to entering the commercialization stage. The point-of care testing available to nonprofessionals will become a new direction. We firmly believe that the monitoring system will be more perfect and stable and public life will be healthier and safer.

CRISPR/Cas12a-Based APE1 Enzyme Cleavage Assay for Drug Resistance Analysis of Staphylococcus aureus-Related Pneumonia

Drug resistance analysis of Staphylococcus aureus is responsible for generating significant mortality and morbidity in numerous diseases. However, sensitive and accurate analysis of drug resistance of S. aureus remains a huge challenge. In this study, we present the development of a fluorescence biosensor based on the CRISPR/Cas12a system that enables label-free and ultrasensitive detection of the mecA gene in methicillin-resistant S. aureus (MRSA). The biosensor identified the mecA gene in MRSA using Cas12a/crRNA. This recognition triggered the trans-cleavage activity of Cas12a and the release of RNA1, which subsequently induced Apurinic/apyrimidinic endonuclease 1 (APE1) enzyme-assisted target recycling and G-quadruplexes/Thioflavin T-based signal reaction. Based on this, the biosensor effectively detects the mecA gene with a low limit of detection of 212 aM and a high degree of selectivity, even toward single base mutations. Compared with the traditional CRISPR-Cas12a system-based methods, in which the signal amplification process is prone to generate nucleic acid sequence mismatch, which causes errors, the biosensor used APE1 to improve nucleic acid sequence recognition specificity to ensure that the RNA1 sequence released after Cas12a/crRNA cleavage can specifically guide the signal cycle. In addition to enhancing the CRISPR toolkit, the developed biosensor offers a novel method for the precise and sensitive identification of drug-resistant microbes that cause infections.

In Vitro Antimicrobial Potential of Portuguese Propolis Extracts from Gerês against Pathogenic Microorganisms

Antimicrobial resistance (AMR) is one of humanity's main health problems today. Despite all the breakthroughs and research over the past few years, the number of microbial illnesses that are resistant to the available antibiotics is increasing at an alarming rate. In this article, we estimated the biomedical potential of Portuguese propolis harvested from the Gerês apiary over five years, evaluating the in vitro antimicrobial effect of five hydroalcoholic extracts prepared from five single propolis samples and of a hydroalcoholic extract obtained from the mixture of all samples. The antimicrobial potential was firstly assessed by determining the minimum inhibitory concentration (MIC) of these extracts against a panel of three Gram-positive (Bacillus subtilis, methicillin-sensitive Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus) and one Gram-negative bacteria (Escherichia coli), as well as two yeasts (Candida albicans and Saccharomyces cerevisiae). As MIC values against each bacterium were consistent across all the evaluated propolis extracts, we decided to further conduct a disk diffusion assay, which included three commercial antibiotics-erythromycin, vancomycin, and amoxicillin/clavulanic acid-for comparison purposes. In addition to displaying a concentration-dependent antibacterial effect, the hydroalcoholic extracts prepared with 70% ethanol exhibited stronger antimicrobial capacity than vancomycin against B. subtilis (% of increase ranged between 26 and 59%) and methicillin-sensitive S. aureus (% of increase ranged between 63 and 77%). Moreover, methicillin-resistant S. aureus (MRSA) showed susceptibility to the activity of the same extracts and resistance to all tested antibiotics. These findings support that propolis from Gerês is a promising natural product with promising antimicrobial activity, representing a very stimulating result considering the actual problem with AMR.

The zebrafish embryo model: unveiling its potential for investigating phage therapy against methicillin-resistant Staphylococcus aureus infection

Staphylococcus aureus is a pathogenic bacterium responsible for a broad spectrum of infections, including cutaneous, respiratory, osteoarticular, and systemic infections. It poses a significant clinical challenge due to its ability to develop antibiotic resistance. This resistance limits therapeutic options, increases the risk of severe complications, and underscores the urgent need for new strategies to address this threat, including the investigation of treatments complementary to antibiotics. The evaluation of novel antimicrobial agents often employs animal models, with the zebrafish embryo model being particularly interesting for studying host-pathogen interactions, establishing itself as a crucial tool in this field. For the first time, this study presents a zebrafish embryo model for the in vivo assessment of bacteriophage efficacy against S. aureus infection. A localized infection was induced by microinjecting either methicillin-resistant S. aureus (MRSA) or methicillin-susceptible S. aureus (MSSA). Subsequent treatments involved administering either bacteriophage, vancomycin (the reference antibiotic for MRSA), or a combination of both via the same route to explore potential synergistic effects. Our findings indicate that the bacteriophage was as effective as vancomycin in enhancing survival rates, whether used alone or in combination. Moreover, bacteriophage treatment appears to be even more effective in reducing the bacterial load in S. aureus-infected embryos post-treatment than the antibiotic. Our study validates the use of the zebrafish embryo model and highlights its potential as a valuable tool in assessing bacteriophage efficacy treatments in vivo.

Flotillin-mediated stabilization of unfolded proteins in bacterial membrane microdomains

The function of many bacterial processes depends on the formation of functional membrane microdomains (FMMs), which resemble the lipid rafts of eukaryotic cells. However, the mechanism and the biological function of these membrane microdomains remain unclear. Here, we show that FMMs in the pathogen methicillin-resistant Staphylococcus aureus (MRSA) are dedicated to confining and stabilizing proteins unfolded due to cellular stress. The FMM scaffold protein flotillin forms a clamp-shaped oligomer that holds unfolded proteins, stabilizing them and favoring their correct folding. This process does not impose a direct energy cost on the cell and is crucial to survival of ATP-depleted bacteria, and thus to pathogenesis. Consequently, FMM disassembling causes the accumulation of unfolded proteins, which compromise MRSA viability during infection and cause penicillin re-sensitization due to PBP2a unfolding. Thus, our results indicate that FMMs mediate ATP-independent stabilization of unfolded proteins, which is essential for bacterial viability during infection.

Reducing Peptidoglycan Crosslinking by Chemical Modulator Reverts β-lactam Resistance in Methicillin-Resistant Staphylococcus aureus

Small molecule can be utilized to restore the effectiveness of existing major classes of antibiotics against antibiotic-resistant bacteria. In this study, it is demonstrated that celastrol, a natural compound, can modify the bacterial cell wall and subsequently render bacteria more suceptible to β-lactam antibiotics. It is shown that celastrol leads to incomplete cell wall crosslinking by modulating levels of c-di-AMP, a secondary messenger, in methicillin-resistant Staphylococcus aureus (MRSA). This mechanism enables celastrol to act as a potentiator, effectively rendering MRSA susceptible to a range of penicillins and cephalosporins. Restoration of in vivo susceptibility of MRSA to methicillin is also demonstrated using a sepsis animal model by co-administering methicillin along with celastrol at a much lower amount than that of methicillin. The results suggest a novel approach for developing potentiators for major classes of antibiotics by exploring molecules that re-program metabolic pathways to reverse β-lactam-resistant strains to susceptible strains.

Genomic insights of S. aureus associated with bovine mastitis in a high livestock activity region of Mexico

IMPORTANCE

Bovine mastitis, predominantly associated with gram-positive Staphylococcus aureus, poses a significant threat to dairy cows, leading to a decline in milk quality and volume with substantial economic implications.

OBJECTIVE

This study investigated the incidence, virulence, and antibiotic resistance of S. aureus associated with mastitis in dairy cows.

METHODS

Fifty milk-productive cows underwent a subclinical mastitis diagnosis, and the S. aureus strains were isolated. Genomic DNA extraction, sequencing, and bioinformatic analysis were performed, supplemented by including 124 S. aureus genomes from cows with subclinical mastitis to enhance the overall analysis.

RESULTS

The results revealed a 42% prevalence of subclinical mastitis among the cows tested. Genomic analysis identified 26 sequence types (STs) for all isolates, with Mexican STs belonging primarily to CC1 and CC97. The analyzed genomes exhibited multidrug resistance to phenicol, fluoroquinolone, tetracycline, and cephalosporine, which are commonly used as the first line of treatment. Furthermore, a similar genomic virulence repertoire was observed across the genomes, encompassing the genes related to invasion, survival, pathogenesis, and iron uptake. In particular, the toxic shock syndrome toxin (tss-1) was found predominantly in the genomes isolated in this study, posing potential health risks, particularly in children.

CONCLUSION AND RELEVANCE

These findings underscore the broad capacity for antibiotic resistance and pathogenicity by S. aureus, compromising the integrity of milk and dairy products. The study emphasizes the need to evaluate the effectiveness of antibiotics in combating S. aureus infections.

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.

Mobile genetic element-driven genomic changes in a community-associated methicillin-resistant Staphylococcus aureus clone during its transmission in a regional community outbreak in Japan

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections are now a public health concern in both community and healthcare settings worldwide. We previously identified a suspected case of a maternity clinic-centred outbreak of CA-MRSA skin infection in a regional community in Japan by PFGE-based analysis. In this study, we performed genome sequence-based analyses of 151 CA-MRSA isolates, which included not only outbreak-related isolates that we previously defined based on identical or similar PFGE patterns but also other isolates obtained during the same period in the same region. Our analysis accurately defined 133 isolates as outbreak-related isolates, collectively called the TDC clone. They belonged to a CA-MRSA lineage in clonal complex (CC) 30, known as the South West Pacific (SWP) clone. A high-resolution phylogenetic analysis of these isolates combined with their epidemiological data revealed that the TDC clone was already present and circulating in the region before the outbreak was recognized, and only the isolates belonging to two sublineages (named SL4 and SL5) were directly involved in the outbreak. Long persistence in patients/carriers and frequent intrahousehold transmission of the TDC clone were also revealed by this analysis. Moreover, by systematic analyses of the genome changes that occurred in this CA-MRSA clone during transmission in the community, we revealed that most variations were associated with mobile genetic elements (MGEs). Variant PFGE types were generated by alterations of prophages and genomic islands or insertion sequence (IS)-mediated insertion of a plasmid or a sequence of unknown origin. Dynamic changes in plasmid content, which were linked to changes in antimicrobial resistance profiles in specific isolates, were generated by frequent gain and loss of plasmids, most of which were self-transmissible or mobilizable. The introduction of IS256 by a plasmid (named pTDC02) into sublineage SL5 led to SL5-specific amplification of IS256, and amplified IS256 copies were involved in some of the structural changes of chromosomes and plasmids and generated variations in the repertoire of virulence-related genes in limited isolates. These data revealed how CA-MRSA genomes change during transmission in the community and how MGEs are involved in this process.

Lysine grafted poly(lactic acid): An intrinsically antimicrobial polymer

Nosocomial infections or healthcare-associated infections, normally develops after the healthcare treatment in the hospital. Most of them are caused by infected medical devices. Plastics are the most common materials for manufacturing these devices because of their good processability, sterilization efficacy, ease of handling and harmlessness, however, it usually do not display antimicrobial properties. Here, in order to infer antimicrobial activity to poly(lactic acid), it was modified by maleation, followed by l-lysine grafting to its structure. The chemical modifications were confirmed by FTIR and 1H NMR analysis, indicating the success of the reactions. The antimicrobial activity was tested using Escherichia coli and Staphylococcus aureus and the results showed that the sample was capable of inhibiting about 99 % of the S. aureus growth by contact. The samples cytotoxicity was also tested using the L929 mouse cells and the results indicated no cytotoxic effect. These results indicated the sample antimicrobial potential, without affect the normal eukaryotic cells. In addition, the processability of the modified PLA (PLA-g-Lys) was improved without compromising its mechanical properties, as shown by thermal analysis and tensile tests. Thus, this novel PLA derivative can be seen as a promising material for future applications in the manufacturing of biomedical devices.

Synergistic bactericidal activity of a novel dual β-lactam combination against methicillin-resistant Staphylococcus aureus

OBJECTIVES

MRSA is a major cause of hospital-acquired and community-acquired infections. Treatment options for MRSA are limited because of the rapid development of β-lactam resistance. Combining antibiotics offers an affordable, time-saving, viable and efficient approach for developing novel antimicrobial therapies. Both amoxicillin and cefdinir are oral β-lactams with indications for a wide range of bacterial infections and mild side effects. This study aimed to investigate the in vitro and in vivo efficacy of combining these two β-lactams against MRSA strains.

METHODS

Fourteen representative prevalent MRSA strains with diverse sequence types (STs) were tested with a combination of amoxicillin and cefdinir, using chequerboard and time-kill assays. The Galleria mellonella larvae infection model was used to evaluate the in vivo efficacy of this dual combination against the community-acquired MRSA (CA-MRSA) strain USA300 and the hospital-acquired MRSA (HA-MRSA) strain COL.

RESULTS

The chequerboard assay revealed a synergistic activity of the dual amoxicillin/cefdinir combination against all tested MRSA strains, with fractional inhibitory concentration index (FICI) values below 0.5 and at least a 4-fold reduction in the MICs of both antibiotics. Time-kill assays demonstrated synergistic bactericidal activity of this dual combination against the MRSA strain USA300 and strain COL. Moreover, in vivo studies showed that the administration of amoxicillin/cefdinir combination to G. mellonella larvae infected with MRSA strains significantly improved the survival rate up to 82%, which was comparable to the efficacy of vancomycin.

CONCLUSIONS

In vitro and in vivo studies indicate that the dual combination of amoxicillin/cefdinir demonstrates a synergistic bactericidal efficacy against MRSA strains of various STs. Further research is needed to explore its potential as a treatment option for MRSA infections.

Target Recognition Triggered Split DNAzyme based Colorimetric Assay for Direct and Sensitive Methicillin-Resistance Analysis of Staphylococcus aureus

The accurate and rapid detection of methicillin-resistant Staphylococcus aureus (MRSA) holds significant clinical importance. This work presents a new method for detecting methicillin-resistant Staphylococcus aureus (S. aureus) in clinical samples. The method uses an aptamer-based colorimetric assay that combines a recognizing probe to identify the target and split DNAzyme to amplify the signal, resulting in a highly sensitive and direct analysis of methicillin-resistance. The identification of the PBP2a protein on the membrane of S. aureus in clinical samples leads to the allosterism of the recognizing probe, and thus provides a template for the proximity ligation of split DNAzyme. The proximity ligation of split DNAzyme forms an intact DNAzyme to identify the loop section in the L probe and generates a nicking site to release the loop sequence ("3" and "4" fragments). The "3" and "4" fragments forms an intact sequence to induce the catalytic hairpin assembly, exposing the G-rich section. The released the G-rich sequence of LR probe induces the formation of G-quadruplex-hemin DNAzyme as a colorimetric signal readout. The absorption intensity demonstrated a strong linear association with the logarithm of the S. aureus concentration across a wide range of 5 orders of magnitude dynamic range under the optimized experimental parameters. The limit of detection was calculated to be 23 CFU/ml and the method showed high selectivity for MRSA.

Phenotypic and genotypic characterization of commensal staphylococci isolated from young volunteers in Alexandria, Egypt

Nasally colonized staphylococci carry antibiotic resistance genes and may lead to serious opportunistic infections. We are investigating nasal carriage of Staphylococcus aureus and Staphylococci other than S. aureus (SOSA) among young volunteers in Egypt to determine their risk potential. Nasal swabs collected over 1 week in June 2019 from 196 volunteers were cultured for staphylococcus isolation. The participants were interviewed to assess sex, age, general health, hospitalization and personal hygiene habits. Identification was carried out using biochemical tests and VITEK 2 automated system. Disc diffusion and minimum inhibitory concentration tests were performed to determine antibiotic susceptibility. Screening for macrolide resistance genes (ermA, ermB, ermC, ermT and msrA) was performed using polymerase chain reaction. Thirty four S. aureus and 69 SOSA were obtained. Multi-drug resistance (MDR) was detected among most staphylococcal species, ranging from 30.77% among S. hominis to 50% among S. epidermidis. Phenotypic resistance to all tested antibiotics, except for linezolid, was observed. Susceptibility to rifampicin, vancomycin and teicoplanin was highest. ermB showed the highest prevalence among all species (79.41% and 94.2% among S. aureus and SOSA, respectively), and constitutive macrolide-lincosamide-streptogramin B (MLSB) resistance was equally observed in S. aureus and SOSA (11.11% and 16.22%, respectively), whereas inducible MLSB resistance was more often found in S. aureus (77.78% and 43.24%, respectively). The species or resistance level of the carried isolates were not significantly associated with previous hospitalization or underlying diseases. Although over all colonization and carriage of resistance genes are within normal ranges, the increased carriage of MDR S. aureus is alarming. Also, the fact that many macrolide resitance genes were detected should be a warning sign, particularly in case of MLSB inducible phenotype. More in depth analysis using whole genome sequencing would give a better insight into the MDR staphylococci in the community in Egypt.

Antibacterial activity and mechanisms of D-3263 against Staphylococcus aureus

Multi-drug-resistant Staphylococcus aureus infections necessitate novel antibiotic development. D-3263, a transient receptor potential melastatin member 8 (TRPM8) agonist, has potential antineoplastic properties. Here, we reported the antibacterial and antibiofilm activities of D-3263. Minimum inhibitory concentrations (MICs) against S. aureus, Enterococcus faecalis and E. faecium were ≤ 50 µM. D-3263 exhibited bactericidal effects against clinical methicillin-resistant S. aureus (MRSA) and E. faecalis strains at 4× MIC. Subinhibitory D-3263 concentrations effectively inhibited S. aureus and E. faecalis biofilms, with higher concentrations also clearing mature biofilms. Proteomic analysis revealed differential expression of 29 proteins under 1/2 × MIC D-3263, influencing amino acid biosynthesis and carbohydrate metabolism. Additionally, D-3263 enhanced membrane permeability of S. aureus and E. faecalis. Bacterial membrane phospholipids phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and cardiolipin (CL) dose-dependently increased D-3263 MICs. Overall, our data suggested that D-3263 exhibited potent antibacterial and antibiofilm activities against S. aureus by targeting the cell membrane.

Antibacterial polylysine-containing hydrogels for hemostatic and wound healing applications: preparation methods, current advances and future perspectives

The treatment of various types of wounds such as dermal wounds, multidrug resistant bacteria-infected wounds, and chronic diabetic wounds is one of the critical challenges facing healthcare systems. Delayed wound healing can impose a remarkable burden on patients and health care professionals. In this case, given their unique three-dimensional porous structure, biocompatibility, high hydrophilicity, capability to provide a moist environment while absorbing wound exudate, permeability to both gas and oxygen, and tunable mechanical properties, hydrogels with antibacterial function are one of the most promising candidates for wound healing applications. Polylysine is a cationic polymer with the advantages of inherent antibacterial properties, biodegradability, and biocompatibility. Therefore, its utilization to engineer antibacterial hydrogels for accelerating wound healing is of great interest. In this review, we initially discuss polylysine properties, and then focus on the most recent advances in polylysine-containing hydrogels (since 2016) prepared using various chemical and physical crosslinking methods for hemostasis and wound healing applications. Finally, the challenges and future directions in the engineering of these antibacterial hydrogels for wound healing are discussed.

Temporal trends of skin and soft tissue infections caused by methicillin-resistant Staphylococcus aureus in Gabon

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the leading causes of mortality due to bacterial antimicrobial resistance. While S. aureus is common in skin and soft tissue infections (SSTI) in Africa, data on MRSA rates are scarce and reports vary widely across the continent (5%-80%). In this study, we describe the proportion of MRSA causing SSTI in Lambaréné, Gabon, over an 11-year period.

METHODS

We retrospectively analyzed data from 953 bacterial specimens collected from inpatients and outpatients with SSTI at the Albert Schweitzer Hospital, Lambaréné, Gabon, between 2009 and 2019. We determined temporal changes in the prevalence of MRSA and identified risk factors for SSTI with MRSA.

RESULTS

68% of all specimens with bacterial growth yielded S. aureus (n = 499/731), of which 7% (36/497) with antimicrobial susceptibility testing were identified as MRSA. Age above 18 years, admission to the surgical ward, and deep-seated infections were significantly associated with MRSA as the causative agent. After an initial decline from 7% in 2009, there was a marked increase in the proportion of MRSA among all S. aureus from SSTI from 3 to 20% between 2012 and 2019. The resistance rate to erythromycin was significantly higher in MRSA than in methicillin-susceptible S. aureus (73% vs. 10%), and clindamycin resistance was detected exclusively in MRSA isolates (8%).

CONCLUSION

The increasing proportion of MRSA causing SSTI over the 11-year period contrasts with many European countries where MRSA is on decline. Continuous surveillance of MRSA lineages in the hospital and community along with antibiotic stewardship programs could address the increasing trend of MRSA.

Prevalence of methicillin sensitive and resistant Staphylococcus aureus carriage among German emergency medical providers

Background

Health care workers (HCW) in Emergency Medical Services (EMS) frequently come into contact with carriers of methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) strains and may acquire and transmit them to patients. However, there is little data on MSSA and MRSA colonization of medical personnel in the emergency services. Additionally, few studies have analyzed the association between personal hygiene of staff and colonization. Therefore, we examined the prevalence of MSSA and MRSA in EMS staff of two German regions and evaluated their personal hygiene behavior.

Method

Throat and nasal swabs from 300 EMS workers were analyzed. Both direct and pre-enriched cultures of the swabs were cultivated on culture media to identify MSSA and MRSA. Results were analyzed together with questionnaires about sociodemographic data and a self-assessment of hygiene behavior. Statistical analysis was done using the R statistical software.

Results

Of the total 300 swabs, 55% were from paramedics, 39% were from emergency medical technicians (EMT) and 5% were from emergency physicians. With 1%, the MRSA prevalence was comparable to that of the German population, while the MSSA rate - 43.7% - was higher than expected. Colonization with MSSA was significantly associated with poor hand hygiene and male sex, and was inversely correlated to time on the job in EMS.

Conclusion

The sample size of 300 and a MRSA prevalence of 1% made a meaningful analysis of potential influencing factors on the prevalence of MRSA infeasible. The comparatively high prevalence of MSSA and the association with decreasing frequency of hand antisepsis suggests an influence of personal hygiene on MSSA colonization. HCW in EMS should be encouraged to make use of their personal protective equipment and practice frequent hand hygiene. The implementation of diagnostic tools such as the Hand Hygiene Self-Assessment Framework of the WHO could be utilized to reveal problems in organizations, followed by an individual program to promote hand hygiene.

Utilization of the Shensheng-Piwen changed medicinal powder extracts combines metal-organic frameworks as an antibacterial agent

Introduction

Widespread opportunistic pathogens pose a serious threat to global health, particularly in susceptible hospital populations. The escalating crisis of antibiotic resistance highlights the urgent need for novel antibacterial agents and alternative treatment approaches. Traditional Chinese Medicine (TCM) and its compounds have deep roots in the treatment of infectious diseases. It has a variety of active ingredients and multi-target properties, opening up new avenues for the discovery and development of antimicrobial drugs.

Methods

This study focuses on assessing the efficacy of the Shensheng-Piwen changed medicinal powder (SPC) extracts against opportunistic pathogen infections by broth microdilution and agar disc diffusion methods. Additionally, biofilm inhibition and eradication assays were performed to evaluate the antibiofilm effects of SPC extracts.

Results

Metabolite profiles were analyzed by LC-MS. Furthermore, the potential synergistic effect between SPC and Metal-Organic Framework (MOF) was investigated by bacterial growth curve analysis. The results indicated that the SPC extracts exhibited antibacterial activity against S. aureus, with a minimum inhibitory concentration (MIC) of 7.8 mg/mL (crude drug concentration). Notably, at 1/2 MIC, the SPC extracts significantly inhibited biofilm formation, with over 80% inhibition, which was critical in tackling chronic and hospital-acquired infections. Metabolomic analysis of S. aureus revealed that SPC extracts induced a notable reduction in the levels of various metabolites, including L-proline, L-asparagine. This suggested that the SPC extracts could interfere with the metabolism of S. aureus. Meanwhile, the growth curve experiment proved that SPC extracts and MOFs had a synergistic antibacterial effect.

Discussion

In conclusion, the present study highlights the potential of SPC extracts as a novel antibacterial agent against S. aureus infections, with promising biofilm inhibition properties. The observed synergistic effect between SPC extracts and MOFs further supports the exploration of this combination as an alternative treatment approach.

A Novel Dimeric Short Peptide Derived from α-Defensin-Related Rattusin with Improved Antimicrobial and DNA-Binding Activities

Rattusin, an α-defensin-related antimicrobial peptide isolated from the small intestine of rats, has been previously characterized through NMR spectroscopy to elucidate its three-dimensional structure, revealing a C2 homodimeric scaffold stabilized by five disulfide bonds. This study aimed to identify the functional region of rattusin by designing and synthesizing various short analogs, subsequently leading to the development of novel peptide-based antibiotics. The analogs, designated as F1, F2, F3, and F4, were constructed based on the three-dimensional configuration of rattusin, among which F2 is the shortest peptide and exhibited superior antimicrobial efficacy compared to the wild-type peptide. The central cysteine residue of F2 prompted an investigation into its potential to form a dimer at neutral pH, which is critical for its antimicrobial function. This activity was abolished upon the substitution of the cysteine residue with serine, indicating the necessity of dimerization for antimicrobial action. Further, we synthesized β-hairpin-like analogs, both parallel and antiparallel, based on the dimeric structure of F2, which maintained comparable antimicrobial potency. In contrast to rattusin, which acts by disrupting bacterial membranes, the F2 dimer binds directly to DNA, as evidenced by fluorescence assays and DNA retardation experiments. Importantly, F2 exhibited negligible cytotoxicity up to 515 μg/mL, assessed via hemolysis and MTT assays, underscoring its potential as a lead compound for novel peptide-based antibiotic development.

Triterpenoid saponin from Panax ginseng increases the sensitivity of methicillin-resistant Staphylococcus aureus to β-lactam and aminoglycoside antibiotics

The triterpenoid saponins, ginsenosides, are the major bioactive compound of red ginseng and can exert various physiological activities. In the present study, we examined whether red ginseng extract (RGE) exerts antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). RGE had no bactericidal activity, at least in the range of dissolvable concentration. However, RGE reduced 0.03-0.25-fold the minimum inhibitory concentration (MIC) values of β-lactam antibiotics (oxacillin, ampicillin, carbenicillin, and cefazolin) and aminoglycoside antibiotics (kanamycin and gentamicin) against the two laboratory strains of MRSA. Moreover, the fractional inhibitory concentration index indicated the synergistic activity of RGE with each of the antibiotics. RGE also increased the kanamycin sensitivity of 15 MRSA strains isolated from human volunteers and increased the ampicillin sensitivity of five MRSA strains isolated from dairy cows diagnosed with bovine mastitis. In contrast, RGE did not alter the MIC values of fosfomycin, tetracycline, and erythromycin, suggesting that RGE acts selectively. In contrast, Triton X-100, which was reported to reduce the MIC value of β-lactam antibiotics to MRSA by increasing membrane permeability, reduced the MIC values of fosfomycin and tetracycline. These results indicate that RGE increases the bactericidal effect of antibiotics via a mechanism different from that used by Triton X-100. We found that ginsenoside Rg3 (Rg3), a component of RGE, was an essential compound that exhibits synergy activity with antibiotics. Furthermore, the non-natural compound K, which contains a common protopanaxadiol aglycon moiety with Rg3, also showed synergistic activity with antibiotics. Thus, Rg3 and compound K are potentially new antibiotic adjuvants against MRSA.IMPORTANCEMethicillin-resistant Staphylococcus aureus (MRSA) is a multidrug-resistant organism that is prevalent worldwide. Therefore, the research and development of new agents against MRSA are required. We first found that ginsenoside Rg3 (Rg3) in red ginseng, made from the roots of Panax ginseng C. A. Meyer, increased the sensitivity of β-lactam antibiotics and aminoglycoside antibiotics to MRSA. Furthermore, we identified that compound K, an unnatural ginsenoside analog, also increased the sensitivity of antibiotics to MRSA, similar to Rg3. By contrast, neither Rg3 nor compound K increased the sensitivity of fosfomycin, tetracycline, and erythromycin to MRSA, suggesting that these act selectively. In the present study, the natural compound Rg3 and its structural isomer, compound K, are potentially new antibiotic adjuvants against MRSA. Currently, multiple antibiotics are used to treat MRSA, but the use of these adjuvants is expected to enable the treatment of MRSA with a single antibiotic and low concentrations of antibiotics.

Nanotopology-Enabled On-Site Pathogen Detection for Managing Atopic Dermatitis

Atopic dermatitis (AD), a prevalent skin condition often complicated by microbial infection, poses a significant challenge in identifying the responsible pathogen for its effective management. However, a reliable, safe tool for pinpointing the source of these infections remains elusive. In this study, a novel on-site pathogen detection that combines chemically functionalized nanotopology with genetic analysis is proposed to capture and analyze pathogens closely associated with severe atopic dermatitis. The chemically functionalized nanotopology features a 3D hierarchical nanopillar array (HNA) with a functional polymer coating, tailored to isolate target pathogens from infected skin. This innovative nanotopology demonstrates superior pathogenic capture efficiency, favorable entrapment patterns, and non-cytotoxicity. An HNA-assembled stick is utilized to directly retrieve bacteria from infected skin samples, followed by extraction-free quantitative loop-mediated isothermal amplification (direct qLAMP) for validation. To mimic human skin conditions, porcine skin is employed to successfully capture Staphylococcus aureus, a common bacterium exacerbating AD cases. The on-site detection method exhibits an impressive detection limit of 103 cells mL-1. The HNA-assembled stick represents a promising tool for on-site detection of bacteria associated with atopic dermatitis. This innovative approach enables to deepen the understanding of AD pathogenesis and open avenues for more effective management strategies for chronic skin conditions.

Structural and kinetic analysis of the monofunctional Staphylococcus aureus PBP1

Staphylococcus aureus, an ESKAPE pathogen, is a major clinical concern due to its pathogenicity and manifold antimicrobial resistance mechanisms. The commonly used β-lactam antibiotics target bacterial penicillin-binding proteins (PBPs) and inhibit crosslinking of peptidoglycan strands that comprise the bacterial cell wall mesh, initiating a cascade of effects leading to bacterial cell death. S. aureus PBP1 is involved in synthesis of the bacterial cell wall during division and its presence is essential for survival of both antibiotic susceptible and resistant S. aureus strains. Here, we present X-ray crystallographic data for S. aureus PBP1 in its apo form as well as acyl-enzyme structures with distinct classes of β-lactam antibiotics representing the penicillins, carbapenems, and cephalosporins, respectively: oxacillin, ertapenem and cephalexin. Our structural data suggest that the PBP1 active site is readily accessible for substrate, with little conformational change in key structural elements required for its covalent acylation of β-lactam inhibitors. Stopped-flow kinetic analysis and gel-based competition assays support the structural observations, with even the weakest performing β-lactams still having comparatively high acylation rates and affinities for PBP1. Our structural and kinetic analysis sheds insight into the ligand-PBP interactions that drive antibiotic efficacy against these historically useful antimicrobial targets and expands on current knowledge for future drug design and treatment of S. aureus infections.

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.

ROS-Responsive Poly(α-l-lysine)-Based Nanoparticles Loaded with Doxycycline Combat Oxidative Stress and Bacterial Infection

Bacterial pneumonia is one of the major threats in clinical practice, and the reactive oxygen species (ROS) generated at the infection site can exacerbate the damage. Currently, conventional antibiotic therapies have low utilization, and their excessive use can result in substantial toxicity. Nanocarrier systems provide an ideal approach for treating bacterial infection by facilitating more efficient utilization of antibiotics. In this study, the ROS-responsive amphiphilic nanoparticles (NPs) are developed and used to encapsulate the antibiotic doxycycline (DOXY) to achieve antibacterial and antioxidant functionalities. The NPs are prepared from poly(α-l-lysine) (α-PLL) and phenylboronic acid pinacol ester simultaneously conjugated carbonyldiimidazole (abbreviated as CDIPB). The phenylboronic acid ester groups on CDIPB could react with excessive ROS to suppress oxidative damage at the infection site. The ROS-responsive degradation of CDIPB also facilitates the rapid release of internal DOXY, effectively killing the accumulated bacteria. Additionally, in vitro cell experiments demonstrate the good biocompatibility of the NPs. These results suggest that the ROS-responsive amphiphilic nanoparticles can serve as a novel nanoplatform for the treatment of bacterial pneumonia.

Immunoinformatic prediction to identify Staphylococcus aureus peptides that bind to CD8+ T-cells as potential vaccine candidates

Background and Aim

Staphylococcus aureus, with its diverse virulence factors and immune response evasion mechanisms, presents a formidable challenge as an opportunistic pathogen. Developing an effective vaccine against S. aureus has proven elusive despite extensive efforts. Autologous Staphylococcus lysate (ASL) treatment has proven effective in triggering an immune response against bovine mastitis. Peptides that stimulate the immune response can be the subject of further research. The study aimed to use immunoinformatics tools to identify epitopes on S. aureus surface and secretory proteins that can bind to major histocompatibility complex class I (MHC I) and CD8+ T-cells. This method aids in discovering prospective vaccine candidates and elucidating the rationale behind ASL therapy's efficacy.

Materials and Methods

Proteins were identified using both literature search and the National Center for Biotechnology Information search engine Entrez. Self and non-self peptides, allergenicity predictions, epitope locations, and physicochemical characteristics were determined using sequence alignment, AllerTOP, SVMTriP, and Protein-Sol tools. Hex was employed for simulating the docking interactions between S. aureus proteins and the MHC I + CD8+ T-cells complex. The binding sites of S. aureus proteins were assessed using Computer Atlas of Surface Topography of Proteins (CASTp) while docked with MHC I and CD8+ T-cells.

Results

Nine potential S. aureus peptides and their corresponding epitopes were identified in this study, stimulating cytotoxic T-cell mediated immunity. The peptides were analyzed for similarity with self-antigens and allergenicity. 1d20, 2noj, 1n67, 1nu7, 1amx, and 2b71, non-self and stable, are potential elicitors of the cytotoxic T-cell response. The energy values from docking simulations of peptide-MHC I complexes with the CD8+ and T-cell receptor (TCR) indicate the stability and strength of the formed complexes. These peptides - 2noj, 1d20, 1n67, 2b71, 1nu7, 1yn3, 1amx, 2gi9, and 1edk - demonstrated robust MHC I binding, as evidenced by their low binding energies. Peptide 2gi9 exhibited the lowest energy value, followed by 2noj, 1nu7, 1n67, and 1d20, when docked with MHC I and CD8 + TCR, suggesting a highly stable complex. CASTp analysis indicated substantial binding pockets in the docked complexes, with peptide 1d20 showing the highest values for area and volume, suggesting its potential as an effective elicitor of immunological responses. These peptides - 2noj, 2gi9, 1d20, and 1n67 - stand out for vaccine development and T-cell activation against S. aureus.

Conclusion

This study sheds light on the design and development of S. aureus vaccines, highlighting the significance of employing computational methods in conjunction with experimental verification. The significance of T-cell responses in combating S. aureus infections is emphasized by this study. More experiments are needed to confirm the effectiveness of these vaccine candidates and discover their possible medical uses.

Evolutionary dynamics of the novel ST22-PT methicillin-resistant Staphylococcus aureus clone co-harbouring Panton-Valentine leucocidin and duplicated toxic shock syndrome toxin 1 genes

OBJECTIVES

Globally, the isolation of community-associated methicillin-resistant Staphylococcus aureus (MRSA) harbouring both the Panton-Valentine leucocidin (PVL) and toxic shock syndrome toxin 1 (TSST-1) genes is rare. However, we encountered an outbreak of the ST22-PT clone exhibiting this phenotype in Japan. Notably, the TSST-1 gene was duplicated in most of the strains. This study aimed to elucidate the mechanisms underlying this gene duplication.

METHODS

A total of 90 MRSA isolates were collected from the skin of outpatients in Fukuoka City, Japan, between 2017 and 2019. Whole-genome sequencing was performed on MRSA strains that were PVL and TSST-1 positive.

RESULTS

A total of 43 (47.8%) strains produced TSST-1, 20 (22.2%) produced PVL, and 16 (17.8%) produced both. Fifteen isolates were classified as ST22/SCCmec type IVa (ST22-PT clone) and one as ST1/SCCmec type V (ST1-PT clone). Three distinct ST22-PT clones were identified: Fukuoka clone I (one PVL gene and one TSST-1 gene), Fukuoka clone II (addition of a TSST-1 gene to Fukuoka clone I), and Fukuoka clone III (marked by a chromosomal inversion in a large region from Fukuoka clone II).

DISCUSSION

Fukuoka clone I may have integrated a novel pathogenicity island bearing the TSST-1 gene, leading to the emergence of Fukuoka clone II with a duplicated TSST-1 gene. This duplication subsequently instigated a chromosomal inversion in a large region owing to the homologous sequence surrounding TSST-1, giving rise to Fukuoka clone III. These findings provide crucial insights into the genetic evolution of MRSA.

Recent advances in cell membrane camouflaged nanotherapeutics for the treatment of bacterial infection

Infectious diseases caused by bacterial infections are common in clinical practice. Cell membrane coating nanotechnology represents a pioneering approach for the delivery of therapeutic agents without being cleared by the immune system in the meantime. And the mechanism of infection treatment should be divided into two parts: suppression of pathogenic bacteria and suppression of excessive immune response. The membrane-coated nanoparticles exert anti-bacterial function by neutralizing exotoxins and endotoxins, and some other bacterial proteins. Inflammation, the second procedure of bacterial infection, can also be suppressed through targeting the inflamed site, neutralization of toxins, and the suppression of pro-inflammatory cytokines. And platelet membrane can affect the complement process to suppress inflammation. Membrane-coated nanoparticles treat bacterial infections through the combined action of membranes and nanoparticles, and diagnose by imaging, forming a theranostic system. Several strategies have been discovered to enhance the anti-bacterial/anti-inflammatory capability, such as synthesizing the material through electroporation, pretreating with the corresponding pathogen, membrane hybridization, or incorporating with genetic modification, lipid insertion, and click chemistry. Here we aim to provide a comprehensive overview of the current knowledge regarding the application of membrane-coated nanoparticles in preventing bacterial infections as well as addressing existing uncertainties and misconceptions.

Type VII secretion system extracellular protein B targets STING to evade host anti-Staphylococcus aureus immunity

Staphylococcus aureus (S. aureus) can evade antibiotics and host immune defenses by persisting within infected cells. Here, we demonstrate that in infected host cells, S. aureus type VII secretion system (T7SS) extracellular protein B (EsxB) interacts with the stimulator of interferon genes (STING) protein and suppresses the inflammatory defense mechanism of macrophages during early infection. The binding of EsxB with STING disrupts the K48-linked ubiquitination of EsxB at lysine 33, thereby preventing EsxB degradation. Furthermore, EsxB-STING binding appears to interrupt the interaction of 2 vital regulatory proteins with STING: aspartate-histidine-histidine-cysteine domain-containing protein 3 (DHHC3) and TNF receptor-associated factor 6. This persistent dual suppression of STING interactions deregulates intracellular proinflammatory pathways in macrophages, inhibiting STING's palmitoylation at cysteine 91 and its K63-linked ubiquitination at lysine 83. These findings uncover an immune-evasion mechanism by S. aureus T7SS during intracellular macrophage infection, which has implications for developing effective immunomodulators to combat S. aureus infections.

Nasal carriage rate, associated factors, and antimicrobial susceptibility patterns of methicillin resistance Staphylococcus aureus among pre-clinical undergraduate students at the College of Health and Medical Sciences, Haramaya University, Ethiopia

Background

Staphylococcus aureus nasal carriage has been linked to higher rates of infection and morbidity. People with Methicillin-resistant Staphylococcus aureus can be a potential source of infection for others. University students living together in crowded conditions increase their risk of acquiring infections. The prevalence of S. aureus, particularly Methicillin-resistant Staphylococcus aureus nasal carriage, in Ethiopian university students is sparse.

Objective

This study aimed to determine the nasal carriage rate, associated factors, and antimicrobial susceptibility patterns of methicillin-resistant Staphylococcus aureus among pre-clinical students at the College of Health and Medical Sciences, Haramaya University, Ethiopia, from 1 July to 30 August 2022.

Methods

An institutional-based cross-sectional study was conducted among 270 randomly selected pre-clinical Health and Medical Sciences students. Data on associated factors were collected using pre-tested, structured questionnaires. A nasal swab was taken from each participant and sent to the microbiology laboratory via Amies transport media in a cold chain. There, it was cultivated using conventional techniques. The isolated colonies were found to be S. aureus, and its antimicrobial susceptibility was performed using the Kirby-Bauer disk diffusion method on Muller-Hinton agar. Methicillin-resistant Staphylococcus aureus expressing using cefoxitin based on CLSI breakpoint. Data were entered into Epi-Data version 4.4.2.1 and exported to the Statistical Package for Social Sciences (SPSS) software version 25 for analysis. Pearson's chi-square test was performed to predict the associations between variables. A p-value less than 0.05 was regarded as statistically significant.

Result

Methicillin-resistant Staphylococcus aureus nasal carriage was 5.9% (95% CI: 3.09-8.7) of cases of S. aureus nasal colonization, which was found to be 12.96% (95% CI: 8.85-16.96). Methicillin-resistant Staphylococcus aureus nasal colonization was significantly associated with the history of cigarette smoking (p = 0.000), intake of khat (p = 0.042), nose-picking habit (p = 0.003), history of sharing personal goods (p = 0.021), and history of hospitalizations (p = 0.00). All of the Methicillin-resistant Staphylococcus aureus isolates were resistant to ampicillin and cefoxitin.

Conclusion

Based on the findings, a considerable proportion of healthy students harbored Methicillin-resistant Staphylococcus aureus strains associated with behavioral factors. Furthermore, these isolates showed high resistance to cefoxitin and ampicillin. Hence, it is crucial to regularly test pre-clinical students to prevent endogenous infections and the spread of Methicillin-resistant Staphylococcus aureus.

Resistance phenotypes and molecular characteristics of Staphylococcus aureus associated with pleuritis in patients at "Hôpital du Mali" teaching hospital

Background

Staphylococcus aureus (S. aureus) is one of the pathogens strongly implicated in hospital infections. Data on the resistance and molecular characteristics of this bacterium are rare in Mali.

Objective

This study aimed to evaluate the antibiotic resistance patterns, virulence factors of S. aureus isolates from pleural fluid infections in hospitalized patients.

Methods

Pleural effusion samples were obtained by thoracentesis for bacteriological examination from October 2021 to December 2022 at the "Hôpital du Mali" teaching hospital. Comorbidities such as HIV/AIDS and diabetes were assessed. Standard microbiological procedures were used for bacterial identification. The disk diffusion method was used to identify methicillin-resistant S. aureus. The PCR amplification method was used to detect the following genes: lukE/D, sek, bsa, sel, and sep.

Results

This study analyzed 6096 samples from inpatients and found a pooled frequency of bacterial pleuritis of 526 (8.6%) in thoracic surgery and pediatric wards. S. aureus was isolated in 52 (9.88%) cases, of which 39 (75%) isolates were MRSA. There was no significant difference between the sexes (p = 1.00). The median age of the patients was 30 years. All S. aureus isolates showed resistance to penicillin-G. The leucocidin lukE/D toxin was detected in 7.7% of thoracic surgery patients, but sek, bsa, sel, and sep toxins were not found.

Conclusion

In this study, we found a high frequency of S. aureus (and MRSA) in pleurisy patients at the "Hôpital du Mali". Only the leukocidin lukE/D was found. The empirical treatment protocol for pleurisy may need revision. Clindamycin, linezolid, teicoplanin, daptomycin, fosfomycin, vancomycin, moxifloxacin and fusidic acid were the most active antibiotics on our isolates in this study. Infection prevention measures, active surveillance, and effective therapeutic options are recommended.