Clinical Methicillin-resistant Staphylococcus Aureus Isolates Research Articles

Valine potentiates cefoperazone-sulbactam to kill methicillin-resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) is possibly the most infamous example of antibiotic resistance and new antibiotics are urgently needed to control it. The present study used metabolic state-reprogramming approach to identify an ideal biomarker as an antibiotic adjuvant for reversing the metabolic state of MRSA. The most repressed valine was identified as the adjuvant. Exogenous valine most effectively potentiated cefoperazone-sulbactam (SCF) to kill MRSA in vitro and in vivo. Viability of 18 clinical MRSA isolates was reduced by the top 276.64-fold in the presence of valine and SCF. In mouse models, lower bacterial load in liver, spleen, kidney, thigh, and higher survival were determined in the SCF + valine than valine or SCF alone. Valine promoted MRSA to increase SCF uptake that overcomes the efflux and enzymatic hydrolysis. It also extended the PAE of SCF. These occur because valine activates the pyruvate cycle to elevate proton motive force by NADH and increases membrane permeability by lauric acid. Therefore, the combination of valine and SCF is a new drug candidate effective against MRSA.

Time-Kill Curve Analysis of Fucoidan Combination with Conventional Antibiotics against Biofilms Formation of Methicillin-Resistant Staphylococcus aureus and Acinetobacter baumannii Clinical Isolates

Introduction: This study investigates the efficacy of fucoidan combination with antibiotics, against single-species biofilms and mixed-species, individual planktonic, and coculture planktonic conditions of Methicillin-resistant Staphylococcus aureus (MRSA) and Acinetobacter baumannii by time-kill curve analysis. Materials and Methods: Fucoidan, a sulfated polysaccharide, was purchased from Sigma-Aldrich, USA. Clinical isolates of MRSA and A. baumannii from diabetic foot ulcers (DFUs) were used, and single-species biofilms and mixed-species biofilms were developed to assess susceptibility to the treatments using MIC, MBC, minimum biofilm inhibitory concentration, minimum biofilm eradication concentration, and time-kill kinetics assays. Cytotoxicity was assessed using MTT assays on human skin fibroblast cells (HSF-PI 16). Results: The study determined the geometric mean MIC and MBC values for gentamicin, imipenem, and fucoidan in MRSA and A. baumannii cultures, both individually and in co-cultures. The MIC and MBC values were significantly lower under co-culture conditions, indicating enhanced antimicrobial efficacy. Synergy between fucoidan, gentamicin, and imipenem was confirmed through time-kill assays, which showed complete inhibition of bacterial growth and effective biofilm eradication, particularly in mixed-species biofilms. Fucoidan demonstrated low cytotoxicity at optimal concentrations, highlighting their potential as a therapeutic strategy against biofilm-associated infections in DFUs. Conclusion: The study concludes that fucoidan, in combination with gentamicin and imipenem, effectively disrupts mixed-species biofilms of MRSA and A. baumannii, suggesting fucoidan-based therapies could improve outcomes for DFU patients, warranting further clinical investigation.

Expanding the therapeutic window of gramicidin S towards a safe and effective systemic treatment of methicillin-resistant S. aureus infections

The rise of multidrug-resistant bacteria, such as Methicillin-resistant Staphylococcus aureus (MRSA), necessitates the development of new antibacterial therapies. Antimicrobial peptides offer a promising alternative to conventional antibiotics due to their unique mechanisms of action. Gramicidin S exhibits potent bactericidal activity against S. aureus, however, high haemolytic toxicity currently limits its application to topical use. A new series of gramicidin S analogues is presented with rational modifications to the β-turn and β-strand regions, to reduce haemolytic and nephrotoxic effects, while preserving antibacterial potency. The minimum inhibitory concentration (MIC) for each analogue was determined against benchmark methicillin-sensitive S. aureus (MSSA) and MRSA clinical isolates, with toxicity characterised in vitro using human red blood cells and human embryonic kidney cells (HEK-293). Peptide 12 demonstrated a significant two-fold increase in antibacterial activity against both MSSA and MRSA (MIC: 2 μg/mL) compared to gramicidin S (MIC: 4 μg/mL), albeit with increased cytotoxicity. Similarly, peptide 15 showed exceptional efficacy (MIC: 3 μg/mL), but with reduced cytotoxicity, culminating in a two-fold improvement to the therapeutic index (TI) of gramicidin S. Peptides 14 (HC50: 50.48 ± 1.15 μg/mL, IC50: 38.09 μg/mL) and 16 (HC50: 84.09 ± 1.02 μg/mL, IC50: 12.60 μg/mL) also significantly reduced haemolytic toxicity and nephrotoxicity, compared to gramicidin S (HC50: 12.34 ± 0.27 μg/mL, IC50: 6.45 μg/mL). Detailed NMR, CD and computational modelling were used to provide critical insights into how molecular conformation influences both antibacterial potency and cytotoxicity. Collectively, these results expand the therapeutic window of gramicidin S by up to 12-fold, with negligible cytotoxicity observed at concentrations well beyond the acceptable safety threshold, which indicates the potential for safe systemic administration in the treatment of infection caused by resistant pathogens.

Synergistic Effects of Antimicrobial Peptide Dendrocin‑ZM1 Combined with Conventional Antibiotics Against Methicillin-Resistant <i>Staphylococcus aureus</i>

Background: Methicillin-resistant Staphylococcus aureus (MRSA) is the most prevalent type of bacterial resistance. Consequently, it is crucial to develop novel treatments to address bacterial resistance. Objectives: Dendrocin-ZM1 (DZM1) and vancomycin are two compounds whose effects on MRSA are examined in this study. Methods: The synergistic bactericidal effect of the peptide-conventional antibiotic combinations was evaluated using the minimal inhibitory concentration (MIC), minimum bactericidal concentration (MBC) assays, and checkerboard method. Additionally, the time-killing kinetics of DZM1 alone and in combination with vancomycin on MRSA ATCC 43300 strain were assessed. Structural alterations and morphological changes of the MRSA ATCC 43300 strain exposed to DZM1 (1/16 MBC) and vancomycin (1/8 MBC), alone or in combination (1/16 MBC DZM1 + 1/8 MBC vancomycin), were analyzed using transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. Results: Dendrocin-ZM1 exhibited antimicrobial activity against MRSA clinical isolates and MRSA ATCC 43300 (MIC and MBC: 16 µg/mL). A synergistic effect was observed when DZM1 was combined with vancomycin (FIC: 0.187) against MRSA ATCC 43300. The combination of DZM1 with vancomycin at sub-MBC concentrations demonstrated sustained bactericidal activity against MRSA ATCC 43300 strain. According to SEM results, DZM1 increased bacterial cell membrane permeability, enhancing the antibacterial activity of vancomycin. Transmission electron microscopy analysis revealed severe membrane damage and subsequent cell lysis in the MRSA ATCC 43300 strain when treated with the combination of DZM1 and vancomycin. Conclusions: This study supports the potential use of these compounds to reduce reliance on conventional antibiotics and highlights their promise as alternatives for combating bacterial resistance.

Novel isolation and optimization of anti-MRSA bacteriophages using plaque-based biokinetic methods

Background: MRSA (methicillin-resistant Staphylococcus aureus) is a global health problem. Many people are looking for new ways to combat MRSA, for example by using bacteriophages (phages). It has been extremely challenging to isolate a sufficient quantity of lytic anti-MRSA phages. Therefore, new techniques for separating, refining, and reworking anti-MRSA phages were sought in this study. Methods: Of 437 S. aureus isolates, nine clinical MRSA isolates were obtained from three hospitals in Baghdad, Iraq and two ATCC MRSA strains were used to separate wild anti-MRSA phages from sewage, filth, and hospital settings. The wild phage was optimized using plaque-based biokinetic methods. The resulting highly lytic and specific anti-MRSA phages were subjected to novel physico-chemical phage redesign protocols using agents to weaken the bacterial cell wall to allow phages to enter into host bacteria and acquire the specificity of the new host. Three protocols were tested using different combinations of benzethonium chloride (BZT-CH), alkaline ethanol, and chlorhexidine gluconate. Results: Five newly redesigned, transiently stable, anti-MRSA phages were produced using the BZT-CH and ethanol–alkali methods, albeit at varying rates. Conclusion: Although the resulting designed anti-MRSA phages are transiently stable, they represent a rare opportunity and an excellent endless source of lytic anti-MRSA phages from which a large number of permanent phage lysins can be separated and purified.

Isolation, optimization, and redesigning of phages of methicillin-resistant Staphylococcus aureus from clinical hospital isolates in Baghdad

Background: A global health concern is methicillin-resistant Staphylococcus aureus (MRSA). The use of bacteriophages is one of the many novel control strategies against MRSA that are frequently sought. However, it is quite challenging to isolate enough lytic anti-MRSA phages. In order to extract, optimize, and remodel anti-MRSA phages, this study sought novel approaches. Methods: Two ATCC MRSA strains and nine clinical MRSA isolates were used to isolate wild anti-MRSA phages from hospital settings, dirt, and sewage. The wild phages were optimized using plaque-based biokinetic techniques. Using chemicals that weakened bacterial cell walls, the resulting highly lytic and specific anti-MRSA phages were subjected to unique physicochemical phage redesign processes. This allowed the phages to enter host bacteria and acquire the specificity of the new host. Three different protocols were tested using combinations of Tween 20, lysozyme, and nisin A. Results: Nisin A and lysozyme protocols at different rates were found to be successful in producing newly redesigned, transiently stable, anti-MRSA phages. Conclusion: Unlike self-depleting antibiotic-based applications, phage redesign is self-fortifying. In order to address the increasing number of epidemic MRSA strains, this model could prove to be a perfect platform for developing trustworthy control and treatment strategies. Additionally, it is believed to be an infinite supply of anti-MRSA lytic phages from which several permanent phage lysins can be isolated and refined.

Characterization and complete genome sequence of highly lytic phage active against methicillin-resistant Staphylococcus aureus (MRSA) isolated from Egypt

BackgroundMethicillin-Resistant Staphylococcus aureus (MRSA) is one of the most resistant bacteria to antibiotics. S. aureus is an important, widespread pathogen that can cause a variety of infectious diseases in humans and animals. Phages have been recognized as natural, safe, highly specific and effective alternatives agents to antibiotics for preventing and treating bacterial infections caused by MRSA. Therefore, this study aims at the characterization of a novel isolated lytic phage, vB_SauP_ASUmrsa123.MethodsIsolates of Staphylococcus aureus MRSA were obtained on Mannitol Salt Agar and Baird Parker Agar plates and confirmed using VITEK 2. Sewage and clinical samples were used to isolate specific phages for S. aureus MRSA, and plaque assays were used for host range determination on Luria-Bertani (LB) media. The phage morphology of the isolated phage was determined by transmission electron microscopy. The phage’s whole genome sequencing was identified.ResultsA total of 25 isolates of Staphylococci were obtained from different clinical sources and showed typical colonies on Baird-Parker and Mannitol Salt Agar plates. The VITEK 2 automated system revealed that all 25 isolates were confirmed as S. aureus (MRSA). Two of the most antibiotics-resistant isolates were further confirmed using 16S ribosomal RNA sequencing. A lytic phage was detected against the MRSA isolates tested In Vitro, namely vB_SauP_ASUmrsa123. The phage belonged to Rountreeviridae family based on morphological properties observed by TEM and the host range of the isolated phage was tested on the 25 clinical MRSA isolates in Vitro. The one-step growth curve of the isolated phage showed that the latent period was about 55 min, and the burst size was estimated at 167 PFU. The whole genome sequencing and annotation of genes revealed that phage vB_SauP_ASUmrsa123 contained a linear dsDNA with a size of about 17,155 bp with predicted 24 ORFs. Analysis of its genome provides valuable information approximately the variety of phages belonging to the staphylococcal phages class I.ConclusionA lytic Podo Phage vB_SauP_ASUmrsa123 was identified against S. aureus MRSA isolates and its genome was sequenced. The phage was found to be eligible for potential application in biocontrol.

PBP4 is required for serum-induced cell wall thickening and antibiotic tolerance in Staphylococcus aureus.

The bacterial pathogen Staphylococcus aureus responds to the host environment by synthesizing a thick peptidoglycan cell wall, which protects the bacterium from membrane-targeting antimicrobials and the immune response. However, the proteins required for this response were previously unknown. Here, we demonstrate by three independent approaches that the penicillin-binding protein PBP4 is crucial for serum-induced cell wall thickening. First, mutants lacking various non-essential cell wall synthesis enzymes were tested, revealing that a mutant lacking pbp4 was unable to generate a thick cell wall in serum. This resulted in reduced serum-induced tolerance of the pbp4 mutant toward the last resort antibiotic daptomycin relative to wild-type cells. Second, we found that serum-induced cell wall thickening occurred in each of a panel of 134 clinical bacteremia isolates, except for one strain with a naturally occurring mutation that results in an S140R substitution in the active site of PBP4. Finally, inhibition of PBP4 with cefoxitin prevented serum-induced cell wall thickening and the resulting antibiotic tolerance in the USA300 strain and clinical MRSA isolates. Together, this provides a rationale for combining daptomycin with cefoxitin, a PBP4 inhibitor, to potentially improve treatment outcomes for patients with invasive MRSA infections.

Biofilm Eradication and Inhibition of Methicillin-Resistant Staphylococcus Clinical Isolates by Curcumin-Chitosan Magnetic Nanoparticles.

Biofilm-producing methicillin-resistant Staphylococcus aureus (MRSA) and coagulase-negative staphylococci (MR-CoNS) pose clinical challenges in treating healthcare-associated infections. As alternative antimicrobial options are needed, in this study, we aimed to determine the effect of curcumin-chitosan magnetic nanoparticles (Cur-Chi-MNP) on the biofilms of staphylococcal clinical isolates. MRSA and CoNS clinical isolates were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Antimicrobial susceptibility testing was performed using the broth microdilutions. Nanoparticles were synthesized by the co-precipitation of magnetic nanoparticles (MNP) and encapsulated by the ionotropic gelation of curcumin (Cur) and chitosan (Chi). Biofilm inhibition and eradication by nanoparticles, with and without the addition of oxacillin (OXA), were assessed in Staphylococcus strains. Cur-Chi-MNP showed antimicrobial activity against planktonic cells of MRSA and MR-CoNS strains and inhibited MRSA biofilm. The addition of OXA to Cur-Chi-MNP increased the biofilm inhibition and eradication activity against all staphylococcal strains (P = 0.0007), and higher biofilm activity was observed in the early biofilm stages. Cur-Chi-MNP showed antimicrobial and biofilm inhibitory activities against S. aureus. Addition of OXA increased biofilm inhibition and eradication activity against all staphylococcal strains. A combination treatment of Cur-Chi-MNP and OXA could potentially be used to treat staphylococcal biofilm-associated infections in the early stages before the establishment of biofilm bacterial cells.

Identification of Iles Gene Encoding Low-Level Mupirocin Resistance in Clinical Isolates of MRSA And MSSA

Identification of Iles Gene Encoding Low-Level Mupirocin Resistance in Clinical Isolates of MRSA And MSSA

Synthetic lincosamides iboxamycin and cresomycin are active against ocular multidrug-resistant methicillin-resistant Staphylococcus aureus carrying erm genes

ObjectiveAntimicrobial resistance is a global pandemic that poses a major threat to vision health as ocular bacteria, especially methicillin-resistant Staphylococcus aureus (MRSA), are becoming increasingly resistant to first-line therapies. Here we evaluated the antimicrobial activity of new synthetic lincosamides in comparison to currently used antibiotics against clinical ocular MRSA isolates. MethodsAntimicrobial susceptibility testing was performed by broth microdilution for two novel synthetic lincosamides (iboxamycin and cresomycin) and eight comparator antibiotics against a collection of 50 genomically characterised ocular MRSA isolates, including isolates harbouring erm genes (n = 25). ResultsBoth drugs were active against widespread MRSA clonal complexes CC8 and CC5. The MIC50 and MIC90 of iboxamycin were 0.06 and 2 mg/L, respectively. Cresomycin (MIC50 = 0.06 mg/L) also displayed good activity with an in vitro potency four-fold higher (MIC90 = 0.5 mg/L) than iboxamycin. In isolates harbouring erm genes, MIC90 were >16, 2, and 0.5 mg/L for clindamycin, iboxamycin, and cresomycin, respectively. The in vitro potencies of iboxamycin and cresomycin were similar or higher than that of comparator agents and were not impacted by multidrug-resistance phenotypes or by the presence of erm genes when compared with clindamycin. ConclusionsOur results demonstrate that iboxamycin and cresomycin display potent in vitro activity against ocular MRSA isolates, including multidrug-resistant isolates harbouring erm genes.

Discovery of membrane-targeting amphiphilic honokiol derivatives containing an oxazolethione moiety to combat methicillin-resistant Staphylococcus aureus (MRSA) infections

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a major pathogen causing infections in hospitals and the community, and there is an urgent need for the development of novel antibacterials to combat MRSA infections. Herein, a series of amphiphilic honokiol derivatives containing an oxazolethione moiety were prepared and evaluated for their in vitro antibacterial and hemolytic activities. The screened optimal derivative, I3, exhibited potent in vitro antibacterial activity against S. aureus and clinical MRSA isolates with MIC values of 2–4 μg/mL, which was superior to vancomycin in terms of its rapid bactericidal properties and was less susceptible to the development of resistance. The SARs analysis indicated that amphiphilic honokiol derivatives with fluorine substituents had better antibacterial activity than those with chlorine and bromine substituents. In vitro and in vivo toxicity studies revealed that I3 has relatively low toxicity. In a MRSA-infected mouse skin abscess model, I3 (5 mg/kg) effectively killed MRSA at the infected site and attenuated the inflammation effects, comparable to vancomycin. In a MRSA-infected mouse sepsis model, I3 (12 mg/kg) was found to significantly reduce the bacterial load in infected mice and increase survival of infected mice. Mechanistic studies indicated that I3 has membrane targeting properties and can interact with phosphatidylglycerol (PG) and cardiolipin (CL) of MRSA cell membranes, thereby disrupting MRSA cell membranes, further inducing the increase of reactive oxygen species (ROS), protein and DNA leakage to achieve rapid bactericidal effects. Finally, we hope that I3 is a potential candidate molecule for the development of antibiotics to conquer superbacteria-related infections.

Effective biofilm eradication in MRSA isolates with aminoglycoside-modifying enzyme genes using high-concentration and prolonged gentamicin treatment.

Our analysis of 101 MRSA clinical isolates has provided valuable insights that could enhance treatment selection for biofilm infections in orthopedics. We found that high concentrations of gentamicin were effective against MRSA biofilms, and even prolonged exposure to concentrations lower than the minimum biofilm eradication concentration (MBEC) value could eliminate biofilms. The presence of the aac(6')-aph(2″) gene, an aminoglycoside resistance gene, was found to correlate with the minimum inhibitory concentration (MIC) and MBEC values of gentamicin, providing a potential predictive tool for treatment susceptibility. These results suggest that extended high concentrations of local gentamicin treatment could effectively eliminate MRSA biofilms in orthopedic infections. Furthermore, testing for gentamicin MIC or the possession of the aac(6')-aph(2″) gene could help select treatment, including topical gentamicin administration and surgical debridement.

Hla protein expression and artesunate prevented mice from further damage caused by Staphylococcus aureus pneumonia

The laboratory standard MRSA strain WHO-2 and clinical isolate S1 were used to establish a pneumonia infection model. The results showed that methicillin increased the expression of Hla and PVL protein at subminimum inhibitory concentration, while artesunate decreased the secretion of Hla and PVL protein. Artesunate alone reduced hemolysin expression and reversed methicillin-induced increases in Hla and PVL proteins. In addition, the study found that the combination of artesunate and methicillin had the best therapeutic effect, with survival rates of 70 % and 40 % at seven days, respectively (corresponding to the WHO-2 and S1 strains). The combination treatment was able to reduce cell mortality, showing a 65 % and 46 % reduction in cell mortality, respectively. The study also found that the combination therapy decreased the expression of alpha-hemolysin and pantone valentin leukin in the culture medium and significantly reduced the activation of NF-kB. This is caused by a significant decrease in the expression of inflammatory factors.

Antibacterial and antibiofilm potentials of vancomycin-loaded niosomal drug delivery system against methicillin-resistant Staphylococcus aureus (MRSA) infections

The threat of methicillin-resistant Staphylococcus aureus (MRSA) is increasing worldwide, making it significantly necessary to discover a novel way of dealing with related infections. The quick spread of MRSA isolates among infected individuals has heightened public health concerns and significantly limited treatment options. Vancomycin (VAN) can be applied to treat severe MRSA infections, and the indiscriminate administration of this antimicrobial agent has caused several concerns in medical settings. Owing to several advantageous characteristics, a niosomal drug delivery system may increase the potential of loaded antimicrobial agents. This work aims to examine the antibacterial and anti-biofilm properties of VAN-niosome against MRSA clinical isolates with emphasis on cytotoxicity and stability studies. Furthermore, we aim to suggest an effective approach against MRSA infections by investigating the inhibitory effect of formulated niosome on the expression of the biofilm-associated gene (icaR). The thin-film hydration approach was used to prepare the niosome (Tween 60, Span 60, and cholesterol), and field emission scanning electron microscopy (FE-SEM), an in vitro drug release, dynamic light scattering (DLS), and entrapment efficiency (EE%) were used to investigate the physicochemical properties. The physical stability of VAN-niosome, including hydrodynamic size, polydispersity index (PDI), and EE%, was analyzed for a 30-day storage time at 4 °C and 25 °C. In addition, the human foreskin fibroblast (HFF) cell line was used to evaluate the cytotoxic effect of synthesized niosome. Moreover, minimum inhibitory and bactericidal concentrations (MICs/MBCs) were applied to assess the antibacterial properties of niosomal VAN formulation. Also, the antibiofilm potential of VAN-niosome was investigated by microtiter plate (MTP) and real-time PCR methods. The FE-SEM result revealed that synthesized VAN-niosome had a spherical morphology. The hydrodynamic size and PDI of VAN-niosome reported by the DLS method were 201.2 nm and 0.301, respectively. Also, the surface zeta charge of the prepared niosome was − 35.4 mV, and the EE% ranged between 58.9 and 62.5%. Moreover, in vitro release study revealed a sustained-release profile for synthesized niosomal formulation. Our study showed that VAN-niosome had acceptable stability during a 30-day storage time. Additionally, the VAN-niosome had stronger antibacterial and anti-biofilm properties against MRSA clinical isolates compared with free VAN. In conclusion, the result of our study demonstrated that niosomal VAN could be promising as a successful drug delivery system due to sustained drug release, negligible toxicity, and high encapsulation capacity. Also, the antibacterial and anti-biofilm studies showed the high capacity of VAN-niosome against MRSA clinical isolates. Furthermore, the results of real-time PCR exhibited that VAN-niosome could be proposed as a powerful strategy against MRSA biofilm via down-regulation of icaR gene expression.

Biofilm-producing ability of methicillin-resistant Staphylococcus aureus clinically isolated in China

BackgroundStaphylococcus aureus, a commensal bacterium, colonizes the skin and mucous membranes of approximately 30% of the human population. Apart from conventional resistance mechanisms, one of the pathogenic features of S. aureus is its ability to survive in a biofilm state on both biotic and abiotic surfaces. Due to this characteristic, S. aureus is a major cause of human infections, with Methicillin-Resistant Staphylococcus aureus (MRSA) being a significant contributor to both community-acquired and hospital-acquired infections.ResultsAnalyzing non-repetitive clinical isolates of MRSA collected from seven provinces and cities in China between 2014 and 2020, it was observed that 53.2% of the MRSA isolates exhibited varying degrees of ability to produce biofilm. The biofilm positivity rate was notably high in MRSA isolates from Guangdong, Jiangxi, and Hubei. The predominant MRSA strains collected in this study were of sequence types ST59, ST5, and ST239, with the biofilm-producing capability mainly distributed among moderate and weak biofilm producers within these ST types. Notably, certain sequence types, such as ST88, exhibited a high prevalence of strong biofilm-producing strains. The study found that SCCmec IV was the predominant type among biofilm-positive MRSA, followed by SCCmec II. Comparing strains with weak and strong biofilm production capabilities, the positive rates of the sdrD and sdrE were higher in strong biofilm producers. The genetic determinants ebp, icaA, icaB, icaC, icaD, icaR, and sdrE were associated with strong biofilm production in MRSA. Additionally, biofilm-negative MRSA isolates showed higher sensitivity rates to cefalotin (94.8%), daptomycin (94.5%), mupirocin (86.5%), teicoplanin (94.5%), fusidic acid (81.0%), and dalbavancin (94.5%) compared to biofilm-positive MRSA isolates. The biofilm positivity rate was consistently above 50% in all collected specimen types.ConclusionsMRSA strains with biofilm production capability warrant increased vigilance.

Evaluation of the Anti-MRSA Activity of Supercritical Carbon Dioxide and Macerated Crude Extracts of Padina spp. Collected from the Coastal Waters of Tacloban City, the Philippines

The World Health Organization classifies methicillin-resistant Staphylococcus aureus (MRSA) as a high priority in the pathogens list for research and development of new antibiotics. Natural compounds from brown algae are being studied for their potential as alternative sources of antibiotics, including Padina spp. This study aims to evaluate the anti-MRSA activity of the crude extracts obtained through supercritical carbon dioxide extraction (SCCO2) and maceration (MAC) of Padina spp. seaweeds from the coastal waters of Tacloban City, the Philippines. The evaluation of extracts for their anti-MRSA and anti-MSSA (methicillin-susceptible Staphylococcus aureus) activities was done via the resazurin microplate assay, and the Mann-Whitney U test was used to compare these activities. Results show that MAC exhibited minimum inhibitory concentrations (MIC) of 2,048–4,096 μg/mL and 512–4,096 μg/mL for SCCO2 for the MRSA and MSSA control and clinical isolates, respectively. While the MICs for the SCCO2 extracts were lower than those for the MAC extracts, no significant difference was found between the MICs of the extracts from the two extraction methods. No significant difference was observed between the MICs of the extracts against the MRSA (43300) and MSSA (25923) ATCC strains and clinical isolates. Finally, significant differences were observed between the MICs of the control antibiotics and both extraction methods.

Molecular Detection of the mecA and some Virulence Determinants in Methicillin-Resistant Staphylococcus aureus

Background: Methicillin Resistant Staphylococcus aureus (MRSA) is globally acknowledged as a prominent contributor to both hospital-acquired and community infections. Understanding key virulence factors including coagulase production, hemolysis ability and biofilm formation, is crucial. Objective: The study aimed to establish a molecular characterization of mecA gene and virulence factors genes (hla, icaA, and coa) in clinical isolates of MRSA obtained from two hospitals in Baghdad. Materials and Methods: A hundred and five isolates were obtained from clinical sources from November 2022 to March 2023 and their antibiotic sensitivity was assessed using the agar diffusion test against seven different antibiotics (Azithromycin, Ciprofloxacin, Nitrofurantoin, Rifampin, Trimethoprim, Ofloxacin and Oxacillin), through Conventional Polymerase Chain Reaction, the presence of virulence factor genes including mecA, hla, icaA, and coa, was determined in MRSA isolates. Results: All MRSA isolates (100%) harbored the mecA, hla, and icaA genes while the coa gene was recognized in 50% of the isolates. Regarding antibiotic susceptibility, all MRSA isolates (100%) demonstrated sensitivity to Nitrofurantoin. Additionally, 96.8% of the isolates were sensitive to Oxacillin. Conclusion: Molecular detection of methicillin resistance genes and virulence genes can be used to diagnose MRSA isolates in hospitals. The presence of these genes may affect their pattern of sensitivity to antibiotics.

Assessing chlorhexidine resistance in MRSA isolates from hospitals in Cleveland, OH and Detroit, MI

Background: Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most common causes of procedure-related, skin, and soft-tissue infections. Hospitalized patients who are colonized with MRSA are at a higher risk of developing invasive infections after discharge. Chlorhexidine, an antiseptic/disinfectant, has been used to reduce carriage and prevent infections in these patients. Studies have shown chlorhexidine resistance among MRSA strains. Chlorhexidine resistance is associated with qac genes, which encode multidrug efflux pumps that increase bacterial tolerance to disinfectant agents. The global distribution and prevalence of qacA and qacB genes are highly variable. One study reported that qacA and qacB genes could be found in 0.9% - 83.3% of clinical MRSA isolates worldwide. The goal of this study was to determine the prevalence of chlorhexidine resistance and identify the resistance-associated genes from our MRSA samples using whole genome sequencing (WGS). Methods: 474 MRSA samples were obtained from hospitals in Detroit, MI (287) and Cleveland, OH (187). Whole genome sequencing was performed using the NextSeq (Illumina Inc., CA) platform. The sequencing data was analyzed using ResFinder 4.1, a publicly available database that can be used to identify acquired genes and chromosomal mutations mediating antimicrobial resistance. The output was organized into a data sheet to visualize the presence of the genes of interest. Results: The qacA gene was present in only one MRSA sample from the Cleveland area hospital. In the samples from Detroit, 14 out of 287 showed disinfectant resistance genes. The qacA, qacB, and qacD were present in 1, 6, and 7 samples, respectively. The prevalence of any qac gene in the Cleveland area samples was 0.5%. Meanwhile, the prevalence of any qac gene in Detroit area samples was 4.9%. Among the 7 samples that have qacD gene, 6 samples have more than one copy of qacD. Conclusions: The prevalence of the “qac” gene varied widely based on the origin of the samples. Detroit area samples had more qac genes prevalence than Cleveland area samples. Chlorhexidine is a widely used antiseptic/disinfectant, and it plays a vital role in reducing carriage and preventing infection among hospitalized patients colonized with MRSA. Monitoring and addressing MRSA-reduced susceptibility to chlorhexidine is imperative for maintaining the effectiveness of infection control practices such as decolonization.

SCC mec typing among the clinical isolates of Methicillin Resistant Staphylococcus aureus (MRSA) from a Tertiary Care Hospital, Puducherry

Introduction: Methicillin resistance is exhibiteddue to presence of mecA gene and is commonly referred as SCCmec types in MRSA. SCCmec typing helps and acts a way to characterize MRSA infections and gain knowledge in its epidemiology. Our study aims to characterize mecA gene responsible in methicillin resistance by SCCmec typing and emphasize the use of SCCmec typing in routine diagnosis for the classification of MRSA. Methods: A total of 191 clinical isolates were included for the study.Documentation like clinical details and associated risk factors for MRSA acquisition were done. SCCmec typing (type I-V) was done by using M-PCR as per Boyeet al., 2007 protocol. Results: In our study, five different SCCmec types namely SCCmec type I, type II, type III, type IV and type V were detected among the clinical isolates of MRSA. Sccmec type V (53%) was found to be the most predominant type followed by SCCmec type III (47%) and SCCmec type IV (37.6%). Among the 191 MRSA isolates, 7 clinical isolates were SCCmec non-typeable isolates. Conclusion: Our study reports existence of multiple SCCmec types among the MRSA clinical isolates. SCCmec typing is helpful in determining the contribution of the isolates in understanding their association being CA-MRSA or HA-MRSA which in turn helps in designing effective surveillance and control strategies in the management of MRSA infections.