Synthesis of Graphene@C3N4-Cu Beads Nanocomposites and their Antimicrobial Efficacy Against Drug-Resistant Bacteria and Fungi.

BACKGROUND: Increased intake of drugs worldwide and the subsequent advent of resistance to existing antibiotics have globally threatened health organizations. To combat the problem of these drug-resistant infections, as an alternative approach, graphene (GN)-related nanomaterials have attracted significant interest because of their effective anti-microbial potential. The present study shows the synthesis and characterization of nanocomposite of GN with carbon nitride viz. g- C3N4, g-C3N4-Cu, and GN@g-C3N4-Cu. Further, we investigated the anti-microbial potential of these nanocomposites against strains of Gram-negative and Gram-positive bacteria, viz., a multidrug- resistant strain of Pseudomonas aeruginosa (MDRPA), a methicillin-resistant strain of Staphylococcus aureus ATCC33593 (MRSA), and an azole-sensitive fungal strain (Candida albicans ATCC14053). METHODS: The morphological characterization of GN@g-C3N4-Cu nanocomposite was executed by scanning electron microscopy, whereas the elemental analysis and their distribution were studied by energy-dispersive X-ray spectroscopy and elemental mapping methods. Furthermore, the anti-microbial and antibiofilm efficacies of g-C3N4, g-C3N4-Cu, and GN@g-C3N4-Cu nanocomposites were evaluated by disc diffusion, two-fold serial micro broth dilution, and 96 well microtiter plate methods. RESULTS: The ternary g-C3N4-Cu@GN, apart from the structures of g-C3N4-Cu, showed big sheets of GN. The observance of C, N, O, and Cu in the elemental analysis, as well as their uniform distribution in the mapping, indicated the successful fabrication of g-C3N4-Cu@GN. GN@g-C3N4-Cu followed by g-C3N4-Cu and (g-C3N4) exhibited significantly higher antimicrobial activity (zone of inhibition from 14.33 to 49.33 mm) against both the drug-resistant bacterial strains and azole-sensitive C. albicans. MICs of nanocomposites ranged from 32 -256 µg/ml against the tested strains. Whereas all three nanocomposites at sub-MICs (0.25 A- and 0.5 A- MICs) showed concentration- dependent inhibition of biofilm formation in MDRPA, MRSA, and C. albicans by allowing 11.35% to 32.59% biofilm formation. CONCLUSION: Our study highlights the enhanced efficiency of GN@g-C3N4-Cu nanocomposites as potential anti-microbial and antibiofilm agents to overcome the challenges of multi-drug-resistant bacteria and azole-sensitive fungi. Such kind of nanocomposites could be used to prevent nosocomial infections if coated on medical devices and food manufacturing instruments.

Emergence of methicillin-resistant Staphylococcus aureus (MRSA) RdJ clone (CC5-ST105-SCCmecII-t002) in Santa Catarina, Brazil.

The emergence of highly successful genetic lineages of methicillin-resistant Staphylococcus aureus (MRSA) poses a challenge in human healthcare due to increased morbidity and mortality rates. The RdJ clone (CC5-ST105-SCCmecII-t002 lineage), previously identified in Rio de Janeiro, Brazil, was linked to bloodstream infections and features a mutation in the aur gene (encoding aureolysin). Additionally, clinical isolates derived from this clone were more effective at evading monocytic immune responses. This study aimed to detect the RdJ clone among clinical MRSA isolated in Santa Catarina (SC) and examine its antimicrobial resistance and phagocytosis evasion capabilities. Our findings revealed the RdJ clone in 20 % of MRSA isolates, all exhibiting multiresistance. RdJ clone isolates from SC did not demonstrate a decreased rate of phagocytosis compared to CC5 non-RdJ isolates. Structural analysis suggests that the aur mutation is unlikely to significantly impact aureolysin activity. Genomic analysis of one isolate unveiled a genetic variant of the RdJ clone, sharing lineage and gene distribution but lacking the aur mutation. This study enhances the understanding of the clinical and epidemiologic risks associated with the RdJ clone and the biological mechanisms underlying its spreading in SC.

Therapeutic drug monitoring of antibiotics for methicillin-resistant Staphylococcus aureus infections: an updated narrative review for clinicians.

BACKGROUND: Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) are associated with high mortality rates. Optimal antibiotic dosage plays a crucial role in reducing MRSA burden; thus, the use of therapeutic drug monitoring (TDM) in the clinical practice, especially of new drugs such as ceftobiprole, ceftaroline, dalbavancin and oritavancin, should be implemented. OBJECTIVES: We aim to examine and summarize the available evidence about TDM of anti-MRSA molecules, with a focus on pneumonia, endocarditis and vascular infections, and bone and joint infections. SOURCES: We applied "therapeutic drug monitoring" and "Staphylococcus aureus" as search terms in PubMed, considering a time frame of 24 years (2001-2024). Articles in English language, non-duplicated, evaluating antibiotic therapeutic target and role of TDM were included in the study. CONTENT: In this review, available data for therapeutic target and TDM were critically analyzed and summarized and suggestions about the use of old and new anti-MRSA antibiotics were provided, focusing on optimal dosages, tissue penetration according to infection types and toxicity. Limitations to the widespread use of TDM in the clinical practice were discussed. IMPLICATIONS: The use of TDM may play an important role for the optimal management of patients with MRSA infections and may impact on patient outcomes by increasing efficacy and reducing the risk of adverse events. TDM may be implemented in clinical practice, however several limitations such as the wide variability in the methodology and the need for skilled personnel need to be considered.

Impact of the First Twenty-Four-Hour Area Under the Concentration-Time Curve/Minimum Inhibitory Concentration of Vancomycin on Treatment Outcomes in Patients With Methicillin-Resistant Staphylococcus aureus Bacteremia.

Background: Vancomycin regimens are designed to achieve an area under the concentration-time curve/minimum inhibitory concentration (AUC/MIC) ratio ranging between 400 and 600 µg·h/mL in the steady state. However, in cases of critical infections such as bacteremia requiring an early treatment approach, the clinical course may be affected by the AUC/MIC before reaching the steady state, that is, the AUC/MIC values 24 h after the first dose (first 24-h AUC/MIC). This study evaluated the relationship between the first 24-h AUC/MIC and the clinical course of methicillin-resistant Staphylococcus aureus (MRSA) infection. Methods: We retrospectively reviewed the records of patients with MRSA bacteremia in a university hospital between 2015 and 2022. The first 24-h AUC/MIC cutoff was set at 300 µg·h/mL based on the results of early response, and eligible patients were divided into groups with a first 24-h AUC/MIC either < 300 µg·h/mL (< 300 group, n = 32) or ≥ 300 µg·h/mL (≥ 300 group, n = 38). The primary endpoint was the rate of treatment efficacy, and the secondary endpoints were time to clinical and bacteriological improvement and 30-day survival rate. Results: Treatment efficacy and 30-day survival rates were not significantly different between the two groups (78.1% vs. 79.0%, P = 0.933 and 83.9% vs. 87.2%, P = 0.674, respectively). Among patients who showed treatment efficacy, the median time to clinical and bacteriological improvement was 11.5 days and 8.0 days in the < 300 and ≥ 300 groups, respectively; compared to the ≥ 300 group, the < 300 group had a significantly longer time to improvement (P = 0.001). Conclusions: The first 24-h AUC/MIC had no effect on the treatment efficacy and 30-day survival rates. However, the time to clinical and bacteriological improvement was significantly prolonged in the < 300 group, indicating that the first 24-h AUC/MIC does not affect the rate of therapeutic efficacy but may affect the treatment period.

Antibacterial efficacy of antimicrobial peptide-functionalized hydrogel particles combined with vancomycin and oxacillin antibiotics.

The rise of antibiotic resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), requires novel approaches to combat infections. Medical devices like implants and wound dressings are frequently used in conjunction with antibiotics, motivating the development of antibacterial biomaterials capable of exhibiting combined antibacterial effects with conventional antibiotics. This study explores the synergistic antibacterial effects of combining antimicrobial peptide (AMP) functionalized hydrogel particles with conventional antibiotics, vancomycin (VCM) and oxacillin (OXA), against Staphylococcus aureus and MRSA. The AMP employed, RRPRPRPRPWWWW-NH2, has previously demonstrated broad-spectrum activity and enhanced stability when attached to hydrogel substrates. Here, checkerboard assays revealed additive and synergistic interactions between the free AMP and both VCM and OXA against Staphylococcus aureus and MRSA. Notably, the AMP-OXA combination displayed a significant synergistic effect against MRSA, with a 512-fold reduction in OXA's minimum inhibitory concentration (MIC) when combined with free AMP. The observed synergism against MRSA was retained upon covalent AMP immobilization onto the hydrogel particles; however, at a lower rate with a 64-fold reduction in OXA MIC. Despite this, the OXA-AMP hydrogel particle combinations retained considerable synergistic potential against MRSA, a strain resistant to OXA, highlighting the potential of AMP-functionalized materials for enhancing antibiotic efficacy. These findings underscore the importance of developing antimicrobial biomaterials for future medical devices to fight biomaterial-associated infections and reverse antimicrobial resistance.

Phenotypic and genomic analysis of the hypervirulent methicillin-resistant Staphylococcus aureus ST630 clone in China.

Methicillin-resistant Staphylococcus aureus (MRSA) sequence type 630 (ST630) is a rarely reported lineage worldwide. This study aimed to trace the dissemination of the emerging MRSA ST630 clones in China and investigate their virulence potential. We collected 22 ST630-MRSA isolates from across China and performed whole-genome sequencing analysis and virulence characterization on these isolates. Epidemiological results showed that MRSA ST630 isolates were primarily isolated from pus/wound secretions, mainly originating from Jiangxi province, and carried diverse virulence and drug resistance genes. Staphylococcal cassette chromosome mec type V (SCCmec V) predominated (11/22, 50.0%) among the MRSA ST630 isolates. Interestingly, nearly half (45.5%) of the 22 ST630-MRSA isolates tested lacked intact SCCmec elements. Phylogenetic analysis demonstrated that ST630-MRSA could be divided into two distinct clades, with widespread dissemination mainly in Chinese regions. Five representative isolates were selected for phenotypic assays, including hemolysin activity, real-time fluorescence quantitative PCR, western blot analysis, hydrogen peroxide killing assay, blood killing assay, cell adhesion and invasion assay, and mouse skin abscess model. The results showed that, compared to the USA300-LAC strain, ST630 isolates exhibited particularly strong invasiveness and virulence in the aforementioned phenotypic assays. This study described the emergence of a highly virulent ST630-MRSA lineage and improved our insight into the molecular epidemiology of ST630 clones in China.IMPORTANCEMethicillin-resistant Staphylococcus aureus (MRSA) sequence type 630 (ST630) is an emerging clone with an increasing isolation rate in China. This study raises awareness of the hypervirulent MRSA ST630 clones in China and alerts people to their widespread dissemination. ST630-staphylococcal cassette chromosome mec V is a noteworthy clone in China, and we present the first comprehensive genetic and phenotypic analysis of this lineage. Our findings provide valuable insights for the prevention and control of infections caused by this emerging MRSA clone.

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.

Multiplex fluorescence loop-mediated isothermal amplification with lateral flow assay for rapid simultaneous detection of mecA and nuc genes in methicillin-resistant Staphylococcus aureus.

BACKGROUND: Antibiotic-resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), pose a significant threat to public health. Existing detection methods, like cultivation-based techniques, demand significant time and labor, while molecular diagnostic techniques, such as PCR, necessitate sophisticated instrumentation and skilled personnel. Although previous multiplex loop-mediated isothermal amplification assays based on fluorescent dyes (mfLAMP) offer simplicity and cost-effectiveness, they are prone to false-positive results. Therefore, developing a rapid and efficient multiplex assay for high-sensitivity MRSA is imperative to create a practical diagnostic tool for point-of-care testing. RESULTS: Here, we developed a mfLAMP combined with a lateral flow assay (mfLAMP-LFA) for the visual and simultaneous detection of the mecA (PBP2a-specific marker) and nuc (S. aureus-specific marker) genes in MRSA. We optimized mfLAMP-LFA using graphene oxide (GO)-based purification and specific DNA probes and evaluated its sensitivity, specificity, and stability. Utilizing GO to mitigate false-positive results by acting as a trap for free DNA probes, the mfLAMP-LFA method successfully identified mecAf and nucf-probes, exhibiting distinct red, green, and yellow fluorescence signals. The detection sensitivity of the developed mfLAMP-LFA method (1 CFU mL-1 in phosphate-buffered saline (PBS)) was comparable to other highly sensitive MRSA detection methods (1 CFU mL-1 in PBS). Furthermore, the method demonstrated specificity for MRSA, detecting it in irrigation water samples within the desired range and achieving reliable recovery rates from spiked samples. SIGNIFICANCE: This novel strategy is the first to incorporate GO into mfLAMP-LFA, enabling specific and sensitive MRSA detection and advancing rapid bacterial detection. This assay facilitates MRSA diagnostics, contributing to improved public health and food safety by delivering rapid, cost-effective point-of-care results. It enables the simultaneous detection of multiple bacteria, even in irrigation water samples artificially inoculated with MRSA, which contain aerobic bacteria at 2.7 × 102 CFU mL-1.

Healthcare-associated infections and antimicrobial resistance in Canadian acute care hospitals, 2018-2022.

Background: Healthcare-associated infections (HAIs) and antimicrobial resistance (AMR) continue to contribute to excess morbidity and mortality among Canadians. Objective: This report describes epidemiologic and laboratory characteristics and trends of HAIs and AMR from 2018 to 2022 (Candida auris, 2012-2022) using surveillance and laboratory data submitted by hospitals to the Canadian Nosocomial Infection Surveillance Program (CNISP) and by provincial and territorial laboratories to the National Microbiology Laboratory. Methods: Data collected from 88 Canadian sentinel acute care hospitals between January 1, 2018, and December 31, 2022, for Clostridioides difficile infections (CDIs), carbapenemase-producing Enterobacterales (CPE) infections, methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infections (BSIs) and vancomycin-resistant Enterococcus (VRE) BSIs. Candida auris (C. auris) surveillance was initiated in 2019 by CNISP and in 2017 (retrospectively to 2012) by the National Microbiology Laboratory. Trend analysis for case counts, rates, outcomes, molecular characterization and AMR profiles are presented. Results: From 2018 to 2022, decreased rates per 10,000 patient days were observed for CDIs (7% decrease; 5.42-5.02) and MRSA BSIs (2.9% decrease; 1.04-1.01). Infection rates for VRE BSIs increased by 5.9% (0.34-0.36). Infection rates for CPE remained low but increased by 133% (0.06-0.14). Forty-three C. auris isolates were identified in Canada from 2012 to 2022, with the majority in Western and Central Canada (98%). Conclusion: From 2018 to 2022, the incidence of MRSA BSIs and CDIs decreased and VRE BSI and CPE infections increased in the Canadian acute care hospitals participating in a national sentinel network (CNISP). Few C. auris isolates were identified from 2012 to 2022. Reporting standardized surveillance data to inform the application of infection prevention and control practices in acute care hospitals is critical to help decrease the burden of HAIs and AMR in Canada.

Lippia multiflora Leaves Extracts Enhance Cefotaxime Bactericidal Effects and Quench the Biofilm Formation in Methicillin-Resistant Staphylococcus aureus ATCC 43300.

Background: The emergence of the multidrug-resistant bacteria strain has become a global world crisis. This study was designed to evaluate the antibiofilm and synergistic effects of Lippia multiflora leaf extracts on the activity of cefotaxime against the methicillin-resistant Staphylococcus aureus (S. aureus). Methods: The synergistic effect of methanol and dichloromethane extracts on the bactericidal activity of cefotaxime was determined by using the antibiotic susceptibility test on agar medium. The antibiofilm activity of the extracts was measured by using the crystal violet method. The antioxidant potential of the extracts was assessed by using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and Ferric Reduction Activity Potential (FRAP) methods. The main secondary metabolites groups were analyzed by using different standard analytical tests. The total phenolics and total flavonoids were quantified spectrophotometrically. Results: The methanol extract (final concentration of 100 µg/ml) inhibited the formation of bacterial biofilm more than salicylic acid (p<0.05). All extracts combined with cefotaxime (20 µg and 200 µg) showed good synergistic bactericidal effect on S. aureus with inhibitory diameters of up to 40 mm. The methanol extract showed higher total phenolics (462.20±10.90 mg EAG/g) and total flavonoids (26.20±0.20 mg EQ/g) contents than the dichloromethane extract (96.70±1.70 mg EAG/g and 8.00±1.20 mg EQ/g). Moreover, the methanol extract showed a higher FRAP reducing power (353.6±4.17 mmol EQ/g) than the dichloromethane extract (385.3±7.01 mmol EQ/g). Qualitative phytochemical analysis showed the presence of tannins, flavonoids, terpenes and sterols in both extracts. Conclusion: These data showed that L. multiflora leaves contain effective antibacterial phytomolecules for combating bacterial resistance.

Unveiling the Potential of Bergenia Phenolics: Vitexin's Role in Allosteric Modulation of PBP2a as a Strategy against MRSA Resistance.

BACKGROUND: For cell wall biosynthesis, drug-resistant S. aureus uses a special protein called PBP2a, even when antibiotics are present and stop its natural processes from working. To combat this, novel therapies are required to specifically target PBP2a with greater efficacy. METHODS: Using computational approaches, we screened nine phenolic compounds from other Bergenia species, including Bergenia ciliata, Begenia ligulata, Bergenia purpurascens, and Ber-genia stracheyi, against the PBP2a allosteric site to explore the potential interaction between phe-nolic compounds and a specific region of PBP2a known as the allosteric site. RESULTS: Based on interaction patterns and estimated affinity, vitexin has been found to be the most prominent phenolic compound. We performed MD simulations on vitexin and ceftazidime as control molecules based on the docking results. The binding free energy estimates of vitexin (-94.48 +/- 17.92 kJ/mol) using MM/PBSA were lower than those of the control (-67.61 +/- 12.29 kJ/mol), which suggests that vitexin may be able to inhibit PBP2a activity in MRSA. CONCLUSION: It has been intriguing to observe a correlation between the affinity of the lead com-pounds at the allosteric site and the modification of Tyr446, the active site gatekeeper residue in PBP2a. Our findings have implied that lead compounds can either directly or indirectly decrease PBP2a activity by inducing allosteric site change in conventional medicine.

Chemical optimization and derivatization of micrococcin p2 to target multiple bacterial infections: new antibiotics from thiopeptides.

Antimicrobial resistance poses a significant threat to humanity, and the development of new antibiotics is urgently needed. Our research has focused on thiopeptide antibiotics such as micrococcin P2 (MP2) and derivatives thereof as new anti-infective agents. Thiopeptides are sulfur-rich, structurally complex substances that exhibit potent activity against Gram-positive pathogens and Mycobacteria species, including clinically resistant strains. The clinical development of thiopeptides has been hampered by the lack of efficient synthetic platforms to conduct detailed structure-activity relationship studies of these natural products. The present contribution touches upon efficient synthetic routes to MP2 that laid the groundwork for clinical translation. The medicinal chemistry campaign on MP2 has been guided by computational molecular dynamic simulations and parallel investigations to improve drug-like properties, such as enhancing the aqueous solubility and optimizing antibacterial activity. Such endeavors have enabled identification of promising lead compounds, AJ-037 and AJ-206, against Mycobacterium avium complex (MAC). Extensive in vitro studies revealed that these compounds exert potent activity against MAC species, a subspecies of non-tuberculous mycobacteria (NTM) that proliferate inside macrophages. Two additional pre-clinical candidates have been identified: AJ-024, for the treatment of Clostridioides difficile infections, and AJ-147, for methicillin-resistant Staphylococcus aureus impetigo. Both compounds compare quite favorably with current first-line treatments. In particular, the ability of AJ-147 to downregulate pro-inflammatory cytokines adds a valuable dimension to its clinical use. In light of above, these new thiopeptide derivatives are well-poised for further clinical development.

A novel chlorin derivative Shengtaibufen (STBF) mediated photodynamic therapy combined with iodophor for the treatment of chronic superficial leg wounds infected with methicillin-resistant Staphylococcus aureus: A retrospective clinical study.

OBJECTIVE: Chronic wounds are costly and difficult to treat, resulting in morbidity and even mortality in some cases due to a high methicillin-resistant Staphylococcus aureus (MRSA) burden contributing to chronicity. We aimed to observe the antimicrobial activity and healing-promoting effect of a novel photosensitizer Shengtaibufen (STBF)-mediated antibacterial photodynamic therapy (PDT) on MRSA-infected chronic leg ulcers. PATIENTS AND METHODS: This was a retrospective, comparative, single-center clinical study. A total of 32 patients with chronic lower limb wounds infected with MRSA from January 2022 to December 2023 were finally included in this study by searching the electronic medical records of the dermatology department of Huadong Hospital, including a group of red light combined with iodophor (control+iodophor, n=16, receiving red light once a week for 8 weeks and routine dressing change with iodophor once a day) and a group of STBF-mediated PDT (STBF-PDT) combined with iodophor (STBF-PDT+iodophor, n=16, receiving STBF-PDT and routine dressing change with iodophor once a day). STBF-PDT was performed once a week (1 mg/ml STBF, 1 h incubation, 630 nm red light, 80 J/cm2) for 8 weeks. The primary endpoints included wound clinical signs, wound size, wound-related pain, re-epithelialization score, MRSA load and wound-related quality of life (wound-QoL). Any adverse events were also recorded. RESULTS: We found that STBF-PDT+iodophor could effectively alleviate clinical infection symptoms, accelerate wound closure, reduce average biological burden and improve wound-QoL without severe adverse events in comparison to the control+iodophor group. The STBF-PDT+iodophor group obtained a mean percentage reduction of 65.22% in wound size (from 18.96±11.18 cm2 to 6.59±7.94 cm2) and excellent re-epithelialization scores, as compared with a decrease of 30.17% (from 19.23±9.80 cm2 to 13.43±9.32 cm2) for the control+iodophor group. Significant differences in wound area were observed at week 6 (p=0.028*) and week 8 (p=0.002**). The bacterial load decreased by 99.86% (from 6.45 × 107±2.69 × 107 to 8.94 × 104±1.92 × 105 CFU/cm2, p<0.0001) in the STBF-PDT+iodophor group and 1.82% (from 6.61 × 107±2.13 × 107 to 6.49 × 107±2.01 × 107 CFU/cm2, p=0.029) in the control+iodophor group. The wound-QoL in STBF-PDT+iodophor group had a 51.62% decrease in overall score (from 29.65±9.33 at the initial to 14.34±5.17 at week 8, p<0.0001) compared to those receiving red light and routine wound care (from 30.73±17.16 to 29.32±15.89 at week 8, p=0.003). Moreover, patients undergoing STBF-PDT+iodophor exhibited great improvements in all domains of wound-QoL (physical, psychological and everyday-life), whereas the control+iodophor group ameliorated in only one field (everyday-life). CONCLUSION: Our data confirmed that a novel photosensitizer, STBF-mediated PDT, when combined with iodophor, served as a potential modality for MRSA infection and a possible therapy for other drug-resistant microorganisms, and as a promising alternative for chronic cutaneous infectious diseases.

"Unmasking a Looming Crisis: Escalating MIC of Last Resort Drugs against MRSA Isolates from a Tertiary Hospital in Central India."

PURPOSE: The Centers for Disease Control and Prevention has classified methicillin-resistant S aureus (MRSA) as a serious public health threat. The escalating minimum inhibitory concentration (MIC) of standard anti-methicillin-resistant S aureus (MRSA) drugs within the susceptible range, known as "MIC creep," jeopardizes their effectiveness against MRSA infections, posing additional challenges in managing MRSA infections. This cross-sectional study was conducted in a tertiary care hospital in Central India to assess the susceptibility trends of clinical MRSA isolates against commonly used anti-MRSA drugs and to observe MIC creep, if any, over three years (2020-2022). METHODS: The study included 158 non-repetitive clinical MRSA isolates. The MICs of vancomycin, teicoplanin, and linezolid were determined in MRSA strains using agar dilution, while the MIC of daptomycin was performed by broth microdilution. MIC creep was assessed by calculating MIC50, MIC90, Modal MIC, G-mean MIC, and susceptible and resistant percentages for the fiscal years 2020, 2021, and 2022. RESULTS: Of the 158 MRSA isolates, none were resistant to vancomycin, teicoplanin, and daptomycin, but two showed resistance to linezolid (LRSA). However, fifteen isolates showed intermediate resistance to vancomycin (VISA), and five showed intermediate resistance to teicoplanin (TISA). MIC of these anti-MRSA drugs increased in 2021 and 2022 compared to 2020. G-mean MIC for vancomycin, teicoplanin, and linezolid in MRSA strains increased significantly over the study period, while daptomycin MIC remained relatively stable, with a slight increase in 2021 and 2022. There was a high resistance rate for clindamycin, doxycycline, and chloramphenicol among VISA, TISA, and LRSA isolates compared to MRSA. CONCLUSIONS: During the three years of the study, "MIC creep" was observed in vancomycin, teicoplanin, and linezolid and, to some extent, for daptomycin in MRSA strains. The recovery of VISA, TISA, and linezolid-resistant MRSAs is worrisome, suggesting possible MRSA treatment failure and being a forerunner of resistant strains.

Infected Emphysematous Bullae of the Lung: A Diagnostic Challenge.

Infected emphysematous bullae of the lung present a diagnostic challenge due to their rarity and diverse clinical manifestations. We report the case of a 52-year-old female with chronic respiratory symptoms, including breathlessness and dry cough, persisting for six months. Imaging studies revealed characteristic features of infected emphysematous bullae, including large thick-walled cavities with air-fluid levels and associated parenchymal compression. Biomass exposure history and microbiological analysis, which isolated methicillin-resistant coagulase-negative Staphylococcus (MRCoNS), further supported the diagnosis. The patient responded well to antimicrobial therapy with doxycycline and linezolid. This case underscores the importance of considering environmental factors and multidisciplinary collaboration in managing complex respiratory conditions. Further research is warranted to elucidate optimal management strategies for infected emphysematous bullae of the lung.

Retention of methicillin susceptibility in Staphylococcus aureus using natural adjuvant as an allosteric modifier of penicillin-binding protein 2a.

The emergence of methicillin-resistant Staphylococcus aureus (MRSA) poses a significant global public health challenge due to its resistance to conventional antibiotics, primarily mediated by the mutated penicillin-binding protein, PBP2a. This study aims to investigate the potential of phytochemicals derived from medicinal plants in the Indian subcontinent to serve as adjuvants, enhancing the efficacy of methicillin against MRSA through allosteric modification of PBP2a using molecular docking and molecular dynamics (MD) simulation. After comprehensive Absorption, Distribution, Metabolism, and Excretion (ADME) profiling, along with AMES and hepatotoxicity tests, 9 compounds were shortlisted as suitable adjuvant candidates. Among them, nimbolide, quercetin, emodin, daidzein, eriodictyol, luteolin, and apigenin exhibited strong binding affinity to the allosteric site of PBP2a, with docking scores ranging from -8.7 to -7.3 kcal/mol. These phytochemicals facilitated enhanced methicillin binding, as evidenced by improved docking scores ranging from -6.1 to -6.8 kcal/mol, compared to -5.6 kcal/mol for methicillin alone. Molecular dynamics simulations confirmed the stability and favorable conformations of phytochemical-PBP2a complexes. Quercetin and daidzein were identified as the most promising adjuvant candidates, forming stable and energetically favorable complexes with PBP2a. Experimental validation showed that quercetin, at 30 mg/mL, effectively retained methicillin's antibacterial efficacy against MRSA. This study underscores the potential of natural compounds in overcoming antibiotic resistance and suggests that phytochemical-antibiotic synergism could be a viable strategy to combat multidrug-resistant bacterial infections.

Antibacterial activity of a silver-incorporated vancomycin-modified mesoporous silica against methicillin-resistant Staphylococcus aureus.

Since conventional antibiotics are almost ineffective on methicillin-resistant Staphylococcus aureus (MRSA) strains, designing their antibacterial alternatives is necessary. Besides, the use of vancomycin is applied for specific detection of the bacteria. Silver-incorporated vancomycin-modified mesoporous silica nanoparticles (MSNs@Van@Ag NPs) were designed for detection and treatment of MRSA bacteria. Mesoporous silica nanoparticles (MSNs) were synthesized through the template method, modified with vancomycin, and finally incorporated with silver nanoparticles (Ag NPs). The MSNs@Van@Ag NPs with a homogenously spherical shape, average size of 50-100 nm, surface area of 955.8 m2/g, and thermal stability up to 200°C were successfully characterized. The amount of Ag incorporated into the MSNs@Van@Ag was calculated at 3.9 ppm and the release amount of Ag was received at 2.92 ppm (75%) after 100 h. The in vitro antibacterial susceptibility test showed the MIC of 100 µg mL-1 for MSNs@Van and 50 µg mL-1 for MSNs@Van@Ag, showing in vitro enhanced effect of Ag and vancomycin in the bactericidal process. An in vivo acute pneumonia model was performed and biochemical assays and pathological studies confirmed the nanomedicine's short-term safety for in vivo application. Cytokine assay using ELISA showed that MSN@Van@Ag causes a reduction of pro-inflammatory cytokines and bacterial proliferation leading to alleviation of inflammatory response.

A Rare Neonatal Infection: Methicillin-Resistant Staphylococcus aureus (MRSA) Orbital Cellulitis.

We present a case of orbital cellulitis as a rare cause of late-onset neonatal sepsis in a 4-week-old infant. Although ample literature describes orbital cellulitis in pediatric age groups, community-acquired orbital cellulitis as a cause of late-onset neonatal sepsis has not been well-described. We report one case of late neonatal sepsis in which orbital cellulitis and subsequent methicillin-resistant Staphylococcus aureus (MRSA) bacteremia were found. This case emphasizes the importance of early recognition of orbital cellulitis in neonates and awareness of this unique cause of sepsis.