Methicillin-susceptible S. Aureus Research Articles

Genomic characterization of Staphylococcus aureus isolated from patients admitted to intensive care units of a tertiary care hospital: epidemiological risk of nasal carriage of virulent clone during admission.

We conducted a molecular epidemiological study of Staphylococcus aureus using whole-genome sequence data and clinical data of isolates from nasal swabs of patients admitted to the intensive care unit (ICU) of Hiroshima University hospital. The relationship between isolate genotypes and virulence factors, particularly for isolates that caused infectious diseases during ICU admission was compared with those that did not. The nasal carriage rates of methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) in patients admitted to the ICU were 7.0% and 20.1%, respectively. The carriage rate of community-acquired (CA)-MRSA was 2.3%, accounting for 32.8% of all MRSA isolates. Whole-genome sequencing analysis of the MRSA isolates indicated that most, including CA-MRSA and healthcare-associated (HA)-MRSA, belonged to clonal complex (CC) 8 [sequence type (ST) 8] and SCCmec type IV. Furthermore, results for three disease foci (pneumonia, skin and soft tissue infection, and deep abscess) and the assessment of virulence factor genes associated with disease conditions [bacteremia, acute respiratory distress syndrome (ARDS), disseminated intravascular coagulopathy (DIC), and septic shock] suggested that nasal colonization of S. aureus clones could represent a risk for patients within the ICU. Particularly, MRSA/J and MSSA/J may be more likely to cause deep abscess infection; ST764 may cause ventilation-associated pneumonia, hospital-acquired pneumonia and subsequent bacteremia, and ARDS, and tst-1-positive isolates may cause DIC onset.IMPORTANCENasal colonization of MRSA in patients admitted to the intensive care unit (ICU) may predict the development of MRSA infections. However, no bacteriological data are available to perform risk assessments for Staphylococcus aureus infection onset. In this single-center 2-year genomic surveillance study, we analyzed all S. aureus isolates from nasal swabs of patients admitted to the ICU and those from the blood or lesions of in-patients who developed infectious diseases in the ICU. Furthermore, we identified the virulent clones responsible for causing infectious diseases in the ICU. Herein, we report several virulent clones present in the nares that are predictive of invasive infections. This information may facilitate the design of preemptive strategies to identify and eradicate virulent MRSA strains, reducing nosocomial infections within the ICU.

Unveilling genetic profiles and correlations of biofilm-associated genes, quorum sensing, and antibiotic resistance in Staphylococcus aureus isolated from a Malaysian Teaching Hospital

BackgroundStaphylococcus aureus is a notorious multidrug resistant pathogen prevalent in healthcare facilities worldwide. Unveiling the mechanisms underlying biofilm formation, quorum sensing and antibiotic resistance can help in developing more effective therapy for S. aureus infection. There is a scarcity of literature addressing the genetic profiles and correlations of biofilm-associated genes, quorum sensing, and antibiotic resistance among S. aureus isolates from Malaysia.MethodsBiofilm and slime production of 68 methicillin-susceptible S. aureus (MSSA) and 54 methicillin-resistant (MRSA) isolates were determined using a a plate-based crystal violet assay and Congo Red agar method, respectively. The minimum inhibitory concentration values against 14 antibiotics were determined using VITEK® AST-GP67 cards and interpreted according to CLSI-M100 guidelines. Genetic profiling of 11 S. aureus biofilm-associated genes and agr/sar quorum sensing genes was performed using single or multiplex polymerase chain reaction (PCR) assays.ResultsIn this study, 75.9% (n = 41) of MRSA and 83.8% (n = 57) of MSSA isolates showed strong biofilm-forming capabilities. Intermediate slime production was detected in approximately 70% of the isolates. Compared to MSSA, significantly higher resistance of clindamycin, erythromycin, and fluoroquinolones was noted among the MRSA isolates. The presence of intracellular adhesion A (icaA) gene was detected in all S. aureus isolates. All MSSA isolates harbored the laminin-binding protein (eno) gene, while all MRSA isolates harbored intracellular adhesion D (icaD), clumping factors A and B (clfA and clfB) genes. The presence of agrI and elastin-binding protein (ebpS) genes was significantly associated with biofilm production in MSSA and MRSA isolates, respectively. In addition, agrI gene was also significantly correlated with oxacillin, cefoxitin, and fluoroquinolone resistance.ConclusionsThe high prevalence of biofilm and slime production among MSSA and MRSA isolates correlates well with the detection of a high prevalence of biofilm-associated genes and agr quorum sensing system. A significant association of agrI gene was found with cefoxitin, oxacillin, and fluoroquinolone resistance. A more focused approach targeting biofilm-associated and quorum sensing genes is important in developing new surveillance and treatment strategies against S. aureus biofilm infection.

PDADMAC/Alginate-Coated Gold Nanorod For Eradication of Staphylococcus Aureus Biofilms.

Over 75% of clinical microbiological infections are caused by bacterial biofilms that grow on wounds or implantable medical devices. This work describes the development of a new poly(diallyldimethylammonium chloride) (PDADMAC)/alginate-coated gold nanorod (GNR/Alg/PDADMAC) that effectively disintegrates the biofilms of Staphylococcus aureus (S. aureus), a prominent pathogen responsible for hospital-acquired infections. GNR was synthesised via seed-mediated growth method, and the resulting nanoparticles were coated first with Alg and then PDADMAC. FTIR, zeta potential, transmission electron microscopy, and UV-Vis spectrophotometry analysis were performed to characterise the nanoparticles. The efficacy and speed of the non-coated GNR and GNR/Alg/PDADMAC in disintegrating S. aureus-preformed biofilms, as well as their in vitro biocompatibility (L929 murine fibroblast) were then studied. The synthesised GNR/Alg/PDADMAC (mean length: 55.71 ± 1.15 nm, mean width: 23.70 ± 1.13 nm, aspect ratio: 2.35) was biocompatible and potent in eradicating preformed biofilms of methicillin-resistant (MRSA) and methicillin-susceptible S. aureus (MSSA) when compared to triclosan, an antiseptic used for disinfecting S. aureus colonisation on abiotic surfaces in the hospital. The minimum biofilm eradication concentrations of GNR/Alg/PDADMAC (MBEC50 for MRSA biofilm = 0.029 nM; MBEC50 for MSSA biofilm = 0.032 nM) were significantly lower than those of triclosan (MBEC50 for MRSA biofilm = 10,784 nM; MBEC50 for MRSA biofilm 5967 nM). Moreover, GNR/Alg/PDADMAC was effective in eradicating 50% of MRSA and MSSA biofilms within 17 min when used at a low concentration (0.15 nM), similar to triclosan at a much higher concentration (50 µM). Disintegration of MRSA and MSSA biofilms was confirmed by field emission scanning electron microscopy and confocal laser scanning microscopy. These findings support the potential application of GNR/Alg/PDADMAC as an alternative agent to conventional antiseptics and antibiotics for the eradication of medically important MRSA and MSSA biofilms.

Evaluation of the Effect of Lactobacillus acidophilus ATCC 4356 Bacteriocin against Staphylococcus aureus.

Lactobacillus acidophilus is lactic acid bacteria that produce bacteriocins. Bacteriocins are antimicrobial peptides or proteins that exhibit activity against closely related bacteria. The aim of this study was to determine the effect of L. acidophilus ATCC 4356 bacteriocin against Staphylococcus aureus. Material and Methods. We used four different phenotypic methods for antimicrobial activities against two standard strains: methicillin-resistant S. aureus (MRSA) ATCC 33591 and methicillin-susceptible S. aureus (MSSA) ATCC 25923. The methods were (1) agar well diffusion, (2) overlay soft agar, (3) paper disk, and (4) modification of punch hole. The ammonium sulfate method was used to concentrate crude bacteriocin, and ultrafiltration and dialysis tubes were used to remove ammonium sulfate from the bacteriocins. Each method was repeated in triplicate. L. acidophilus ATCC 4356 showed antimicrobial activity against both MRSA and MSSA standard strains only by the overlay soft agar method and not by the agar well diffusion, punch hole modification, and paper disk methods. No antimicrobial effects were observed in crude bacteriocins concentrated. The growth inhibition of S. aureus in overlay soft agar method may be due to the production of bacteriocin-like substances. The overlay soft agar method is a qualitative test, so there is a need for further study to optimize the conditions for the production of bacteriocin-like substances in the culture supernatant and precise comparison between the inhibitory activity and pheromone secretion of different strains.

Sequential Time to Positivity as a Prognostic Indicator in Staphylococcus aureus Bacteremia.

We aimed to determine the factors associated with sequential blood culture time to positivity (STTP) and validate the previously defined time to positivity (TTP) ratio threshold of 1.5 in predicting adverse disease outcomes and mortality of Staphylococcus aureus bacteremia (SAB). We conducted an observational study of adult patients with SAB. The TTP ratio was calculated by dividing the TTP of the second blood culture by that of the first. Of 186 patients, 69 (37%) were female, with a mean age of 63.6 years. Median TTP was 12 hours (interquartile range [IQR], 10-15 hours) from the initial and 21 hours (17-29) from sequential blood cultures. Methicillin-resistant S aureus (MRSA)-infected patients had significantly shorter STTPs (P < .001) and lower TTP ratios (P < .001) compared to patients with methicillin-susceptible S aureus (MSSA). A significant correlation between initial and STTP was observed in patients with MRSA (r = 0.42, P = .002) but not in those with MSSA. A higher rate of native valve endocarditis (NVE) significantly correlated with a TTP ratio of ≤1.5 (odds ratio, 2.65 [95% confidence interval, 1.3-5.6]; P = .01). The subgroup having an initial TTP <12 hours combined with a TTP ratio ≤1.5 showed the highest prevalence of NVE. The STTP varies based on methicillin susceptibility of S aureus isolate. This study suggests a potential clinical utility of the STTP to identify patients at a higher risk of NVE. However, prospective studies are required to validate these findings.

Machine Learning-Based Virtual Screening of Antibacterial Agents against Methicillin-Susceptible and Resistant Staphylococcus aureus.

The application of computer-aided drug discovery (CADD) approaches has enabled the discovery of new antimicrobial therapeutic agents in the past. The high prevalence of methicillin-resistantStaphylococcus aureus(MRSA) strains promoted this pathogen to a high-priority pathogen for drug development. In this sense, modern CADD techniques can be valuable tools for the search for new antimicrobial agents. We employed a combination of a series of machine learning (ML) techniques to select and evaluate potential compounds with antibacterial activity against methicillin-susceptible S. aureus (MSSA) and MRSA strains. In the present study, we describe the antibacterial activity of six compounds against MSSA and MRSA reference (American Type Culture Collection (ATCC)) strains as well as two clinical strains of MRSA. These compounds showed minimal inhibitory concentrations (MIC) in the range from 12.5 to 200 μM against the different bacterial strains evaluated. Our results constitute relevant proven ML-workflow models to distinctively screen for novel MRSA antibiotics.

Prevalence of Panton-Valentine leucocidin (pvl) and exfoliative toxin A (eta) gene within methicillin resistant and susceptible Staphylococcus aureus in an urban tertiary hospital: A molecular epidemiology pilot study

Background Staphylococcus aureus is well known to cause a multitude of clinical manifestations, from mild to severe bloodstream infections that could lead to death. Infections are common, either in community-acquired or hospital-acquired settings, and treatment remains a challenge due to methicillin-resistant Staphylococcus aureus (MRSA). The pathogenesis of S. aureus is mediated by several cell-surface and secreted virulence factors. The virulence factors discussed in this study are Panton-Valentine leucocidin (pvl) and exfoliative toxin A (eta). Identifying both pvl and eta gene may help in studying bacterial pathogenesis and biology thus creating possible therapeutic pathway or intervention. Our pilot study aimed to observe pvl and eta as virulence gene prevalence in a North Sumatera tertiary referral health center. Methods Our study was a descriptive-analytical observational study with a cross-sectional design in which we collected isolates over a single time period. The frequency of genes is reported as a percentage comparison between MRSA and methicillin-susceptible S. aureus (MSSA). Qualitative gene prevalence analysis was carried out using the polymerase chain reaction (PCR). Results Our results showed that from 38 MRSA sample isolates, 32 samples were found to be pvl-positive, or 84,3% of the total samples. From 40 MSSA sample isolates, one sample was found to be pvl-positive MSSA, or 97,5%. Regarding eta, from 38 MRSA sample isolates, 81,6% of the total sample did not have eta, while from 40 MSSA sample isolates, all samples were found to be positive for eta. We found that both pvl and eta were significantly more likely to be expressed in the MSSA strain. Conclusions Our study shows that pvl and eta are more likely expressed in MSSA strains than in MRSA strains in Indonesia.

Cephalotin Versus Dicloxacillin for the Treatment of Methicillin-Susceptible Staphylococcus aureus Bacteraemia: A Retrospective Cohort Study.

First-line treatments for methicillin-susceptible S. aureus (MSSA) bacteraemia are nafcillin, oxacillin, or cefazolin. Regional shortages of these antibiotics force clinicians to use other options like dicloxacillin and cephalotin. This study aims to describe and compare the safety and efficacy of cephalotin and dicloxacillin for the treatment of MSSA bacteraemia. This retrospective study was conducted in a referral centre in Mexico City. We identified MSSA isolates in blood cultures from 1 January 2012 to 31 December 2022. Patients ≥ 18 years of age, with a first episode of MSSA bacteraemia, who received cephalotin or dicloxacillin as the definitive antibiotic treatment, were included. The primary outcome was in-hospital all-cause mortality. We included 202 patients, of which 48% (97/202) received cephalotin as the definitive therapy and 52% (105/202) received dicloxacillin. In-hospital all-cause mortality was 20.7% (42/202). There were no differences in all-cause in-hospital mortality between patients receiving cephalotin or dicloxacillin (20% vs. 21%, p = 0.43), nor in 30-day all-cause mortality (14% vs. 18%, p = 0.57) or 90-day all-cause mortality (24% vs. 22%, p = 0.82). No severe adverse reactions were associated with either antibiotic. Cephalotin and dicloxacillin were equally effective for treating MSSA bacteraemia, and both showed an adequate safety profile.

Synthesis of 1,2,3-triazole-piperazin-benzo[b][1,4]thiazine 1,1-dioxides: antibacterial, hemolytic and in silico TLR4 protein inhibitory activities.

In this study, we designed and synthesized a number of novel 1,2,3-triazole-piperazin-benzo[b][1,4]thiazine 1,1-dioxide derivatives and investigated their in vitro antibacterial and hemolytic activity. When compared to the lead chemical, dicloxacillin, the majority of the compounds demonstrated acceptable activity. Among them, the most promising compounds 6e, 6g, 6i, 8d, and 8e exhibited excellent antibacterial activity against the methicillin-susceptible S. aureus (MSSA), methicillin-resistant S. aureus (MRSA), and vancomycin-resistant S. aureus (VRSA) with MIC values of 1.56 ± 0.22 to 12.5 ± 1.75 μg mL-1, respectively, The percentage of hemolysis ranged from 21.3 μg mL-1 to 33.8 μg mL-1. Out of the six compounds (6i, 6e, 6f, 6g, 8e, 8d) tested compound 8e and 8d displayed minimal or negligible hemolytic activity across all the tested concentrations 29.6% and 30.2% recorded at 100 μg mL-1 concentration respectively. In silico docking studies were performed to evaluate the molecular interactions of 6e, 6f, 6g, 6i, 8d, and 8e compounds with Human, Mouse and Bovine TLR4 proteins (PDB: 3FXI, 3VQ1, 3RG1) and observed that three of the compounds (6i, 8d, and 8i) had appreciable binding energies ranging from -8.5 to -9.0 Kcal mol-1. Finally, the in silico pharmacokinetic profile was predicted for potent compounds 8d, 8e and 6i using SWISS/ADME, All compounds investigated in this study adhered to Lipinski's rule of five with slight deviation in molecular weight (8d and 8e).

Genetic characterization of methicillin-resistant / susceptible Staphylococcus aureus (MRSA/MSSA) and Staphylococcus argenteus clinical isolates in Bangladesh: Dominance of ST6-MRSA-IV/t304 and detection of cfr/fexA in ST8-MSSA/t008

ObjectivesCoagulase-positive staphylococcus (CoPS), represented by Staphylococcus aureus, is a major cause of infections in humans. This study aimed to investigate molecular epidemiological characteristics, antimicrobial resistance, and their trends of CoPS in Bangladesh. MethodsClinical isolates of CoPS were collected from two medical institutions in Bangladesh for a 2-year period and analyzed for their species, genotypes, virulence factors, antimicrobial susceptibility, and resistance determinants. Results172 CoPS isolates collected were identified as S. aureus or S. argenteus (170 and two, respectively). Methicillin-resistant S. aureus (MRSA) accounted for 36% (n = 61), having Staphylococcal cassette chromosome mec (SCCmec)-IV (82%) or V (18%). Panton-Valentine leukocidin (PVL) genes were detected at higher rate in methicillin-susceptible S. aureus (MSSA) (62%) than MRSA (26%). MRSA comprised 11 STs, including a dominant type ST6 (46%) associated with mostly SCCmec-IVa/spa-t304, and one isolate had genetic features of the USA300 clone (ST8/SCCmec-IVa/coa-IIIa/spa-t008/ACME-I/ΦSa2USA). STs of CC1, CC88, and CC398 were common in MSSA, with CC88 showing the highest PVL-positive rate. One MSSA isolate (ST8/spa-t008) harbored fexA and cfr showing susceptibility to linezolid. S. argenteus was methicillin-susceptible and belonged to ST2250/coa-XId. ConclusionsGenetic characteristics of current MRSA/MSSA in Bangladesh were revealed, with first identification of S. argenteus at low prevalence.

Investigation of Antimicrobial, Antioxidant, and Cytotoxic Activities of Boesenbergia rotunda rhizome extract

In recent years, antimicrobial resistance (AMR) has become a global threat to public health. In Hawai’i, there is an increasing rate of staph infections of methicillin-resistant Staphylococcus aureus (MRSA), and, hence, a need for new agents to combat the increase of AMR bacteria. This study evaluates the antimicrobial, antioxidant, and cytotoxic activities of Hawaiian-grown Boesenbergia rotunda. Test bacteria included clinical isolates of Gram-positive MRSA and methicillin-susceptible S. aureus (MSSA) as well as Gram-negative Serratia marcescens and Escherichia coli. Five compounds–cardamonin, pinostrobin, pinocembrin, pinostrobin chalcone, and isopanduratin A–were isolated from the ethyl acetate extract of B. rotunda rhizome, and their structures were identified by NMR spectroscopy. These samples exhibited antimicrobial activity against MRSA and MSSA strains, with minimum inhibitory concentration (MIC) values between 128 and 2 µg/mL, with isopanduratin A giving MIC values as low as 2 µg/mL. The antioxidant potential of samples was examined using ferric-reducing antioxidant power (FRAP) assay. At 1 mg/mL of tested samples, FRAP values ranged between 8.74 to 17.76 µM/µg, with pinostrobin chalcone exhibiting the highest FRAP value (17.76 ± 0.65 μM/μg). Moreover, cytotoxicity was measured via sulforhodamine B (SRB) assay. Cardamonin (IC50 of 19.43 ± 0.33 μM) and isopanduratin A (IC50 of 26.84 ± 1.06 μM) exhibited effectiveness against the lung cancer cell line A549. Compounds from B. rotunda showed potent antimicrobial effect against MRSA and MSSA strains as well as antioxidant and cytotoxic activities, and may have the potential for further evaluation and development for pharmaceutical applications.

Importance of Toxin Genes and Polymerase Chain Reaction-Based Open Reading Frame Type Analyses for Severe Staphylococcus aureus Infection in Children.

This study analyzed 26 Staphylococcus aureus strains, including 16 methicillin-resistant S. aureus (MRSA) and 10 methicillin-susceptible S. aureus (MSSA), collected from eight medical institutions in the Chiba Prefecture that requested a toxin gene analysis between 2015 and 2021. A total of 14 Panton-Valentine leukocidin (PVL) positive strains were identified, including MSSA. PVL-positive strains were classified into seven types according to polymerase chain reaction-based open reading frame typing (POT); of these types, three POT MRSA strains have not been previously reported, and one has been previously reported as PVL-negative. Some strains tested positive for both PVL and toxic shock syndrome toxin 1. One POT type was identified in both PVL-positive and PVL-negative strains. To the best of our knowledge, this is the first report on the regional spread of highly pathogenic S. aureus strains based on the POT method in children from multiple medical institutions. This method is useful for estimating the spread of toxin gene-carrying strains in the community owing to its association with toxin genes. As the number of PVL-positive strains in Japan increases, it is important to analyze the isolates of severe S. aureus infections in children by combining toxin gene analyses with the POT method.

860. Molecular Characterization of Isolated Staphylococcus aureus Specimens Using Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS)

Abstract Background Staphylococcus aureus (S. aureus) is a common cause of skin and soft tissue infections (SSTIs). Both the β-lactam resistant form, methicillin resistant S. aureus (MRSA), and non-resistant form, methicillin susceptible S. aureus (MSSA) are associated with disparate infections across age and race; community-associated infections are often due to S. aureus US300. Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) is a used in clinical microbiology laboratories to identify bacterial species, but limited data is available on if this tool can identify different strains of S. aureus. We hypothesize that MALDI-TOF MS can be used to identify strain-specific peaks of S. aureus USA300. Methods Children were enrolled from emergency departments and swabbed for S. aureus (anterior nares, axilla, perirectal, oropharyngeal, and wounds) during two time periods (2006-2008 and 2015-2016). MALDI-TOF MS was performed on S. aureus cultured from study participants. Default parameters used for variance stability, smoothing, baseline subtraction, and normalization in R 4.4.3. and MALDIquant v1.22 were applied to raw data. Peak detection and alignment were performed with a signal-to-noise ratio of three and tolerance of 300 ppm. Binning and machine learning algorithms were used to identify intensity differences of each peak identified; significance of peaks was determined using Chi Square statistical analyses, comparing MRSA and MSSA, and then between all S. aureus isolates compared to USA300. Statistical significance was considered with p-value &amp;lt; 0.05 using R and SAS 9.4. Results From 57 MRSA and 53 MSSA isolates, 320 peaks were identified. 31 significant peaks were identified, with 14 unique peaks for MRSA and 17 for MSSA. With S. aureus USA300, eight of the 31 peaks remained statistically significant. Conclusion MALDI-TOF MS can identify unique peak differences between MRSA and MSSA. This tool can be potentially used to distinguish S. aureus at the strain level in a clinical setting. MALDI-TOF MS can be an impactful and rapid diagnostic tool to detect antibiotic resistance in S. aureus in a clinical setting. Disclosures Lilly Immergluck, MD,MS, Melinta: Grant/Research Support|Melinta: Grant/Research Support

Assessing the Potential of Gallic Acid and Methyl Gallate to Enhance the Efficacy of β-Lactam Antibiotics against Methicillin-Resistant Staphylococcus aureus by Targeting β-Lactamase: In Silico and In Vitro Studies.

Methicillin-resistant Staphylococcus aureus (MRSA), a global health concern, has prompted research into antibiotic adjuvants as a potential solution. Although our group previously reported the enhancing effects of gallic acid (GA) and methyl gallate (MG) on penicillin G activity against MRSA, the synergistic potential with other β-lactam antibiotics and the underlying mechanism have not been fully explored. Therefore, this study primarily aimed to investigate the antibacterial synergism with β-lactam antibiotics through disc diffusion, checkerboard, and time-kill assays. The β-lactamase inhibition was also examined through both molecular modeling and in vitro experiments. Additionally, bacterial morphology changes were studied using a scanning electron microscopy (SEM). The results revealed that both GA and MG exhibited anti-MRSA activity and showed indifferent effects when combined with β-lactam antibiotics against methicillin susceptible S. aureus (MSSA). Interestingly, MG demonstrated synergism with only the β-lactamase-unstable antibiotics against MRSA with the lowest fractional inhibitory concentration (FIC) indexes of ≤3.75. However, GA and MG exhibited weak β-lactamase inhibition. Furthermore, GA, MG, and the combination with ampicillin induced the morphological changes in MRSA, suggesting a possible mechanism affecting the cell membrane. These findings suggest that MG could potentially serve as an adjunct to β-lactam antibiotics to combat MRSA infections.

Integrative proteomic and metabonomic profiling elucidates amino acid and lipid metabolism disorder in CA-MRSA-infected breast abscesses.

Bacterial culture and drug sensitivity testing have been the gold standard for confirming community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infection in breast abscess with a long history. However, these tests may delay treatment and increase the risk of nosocomial infections. To handle and improve this critical situation, this study aimed to explore biomarkers that could facilitate the rapid diagnosis of CA-MRSA infection. This study for the first time applied label-free quantitative proteomics and non-targeted metabonomics to identify potential differentially expressed proteins (DEPs) and differentially expressed metabolites (DEMs) in breast abscess infected with CA-MRSA compared to methicillin-susceptible S. aureus (MSSA). The two omics data were integrated and analyzed using bioinformatics, and the results were validated using Parallel Reaction Monitoring (PRM). Receiver operating characteristic (ROC) curves were generated to evaluate the predictive efficiency of the identified biomarkers for diagnosing CA-MRSA infection. After using the above-mentioned strategies, 109 DEPs were identified, out of which 86 were upregulated and 23 were downregulated. Additionally, a total of 61 and 26 DEMs were initially screened in the positive and negative ion modes, respectively. A conjoint analysis indicated that the amino acid metabolism, glycosphingolipid biosynthesis, and glycerophospholipid metabolism pathways were co-enriched by the upstream DEPs and downstream DEMs, which may be involved in structuring the related network of CA-MRSA infection. Furthermore, three significant DEMs, namely, indole-3-acetic acid, L-(-)-methionine, and D-sedoheptulose 7-phosphate, displayed good discriminative abilities in early identification of CA-MRSA infection in ROC analysis. As there is limited high-quality evidence and multiple omics research in this field, the explored candidate biomarkers and pathways may provide new insights into the early diagnosis and drug resistance mechanisms of CA-MRSA infection in Chinese women.

Differences in Biofilm Formation by Methicillin-Resistant and Methicillin-Susceptible Staphylococcus aureus Strains.

Staphylococcus aureus (S. aureus) is a common pathogen involved in community- and hospital-acquired infections. Its biofilm formation ability predisposes it to device-related infections. Methicillin-resistant S. aureus (MRSA) strains are associated with more serious infections and higher mortality rates and are more complex in terms of antibiotic resistance. It is still controversial whether MRSA are indeed more virulent than methicillin-susceptible S. aureus (MSSA) strains. A difference in biofilm formation by both types of bacteria has been suggested, but how only the presence of the SCCmec cassette or mecA influences this phenotype remains unclear. In this review, we have searched for literature studying the difference in biofilm formation by MRSA and MSSA. We highlighted the relevance of the icaADBC operon in the PIA-dependent biofilms generated by MSSA under osmotic stress conditions, and the role of extracellular DNA and surface proteins in the PIA-independent biofilms generated by MRSA. We described the prominent role of surface proteins with the LPXTG motif and hydrolases for the release of extracellular DNA in the MRSA biofilm formation. Finally, we explained the main regulatory systems in S. aureus involved in virulence and biofilm formation, such as the SarA and Agr systems. As most of the studies were in vitro using inert surfaces, it will be necessary in the future to focus on biofilm formation on extracellular matrix components and its relevance in the pathogenesis of infection by both types of strains using in vivo animal models.

Prevalence of methicillin and clindamycin resistant Staphylococcus species at a tertiary hospital in Tanzania: Implications for antibiotic stewardship and infection management

Methicillin and clindamycin resistance (constitutive and inducible) pose a common clinical challenge in treating Staphylococcal infections. This cross-sectional study, conducted at Muhimbili National Hospital (MNH) in Tanzania from April to June 2023, to assess the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) and clindamycin-resistant Staphylococcus (S.) species by using a cefoxitin disk (30 μg) and the D-test method as per CLSI 2022 guidelines. Of the 361 clinical samples, 125 (34.6%) were culture-positive. Among Staphylococcus spp., S. aureus was 6% (12/125), while 33.6% (42/125) were coagulase-negative staphylococci (CoNS). Among the isolated S. aureus, 75% were resistant to methicillin, while 66.7% of the CoNS were resistant to methicillin. Further, 92% (11/12) of the S. aureus isolates were resistant to erythromycin, and 50% (6/12) were resistant to clindamycin. Among the CoNS, 83% (35/42) were resistant to erythromycin, and 52% (22/42) were resistant to clindamycin. The proportion of inducible macrolides lincosamide streptogramin B resistance (iMLSB), constitutive macrolides lincosamide streptogramin B resistance (cMLSB), and macrolides lincosamide streptgramin B methicillin susceptible (MS) phenotypes among S. aureus isolates was 16.7%, 41.7%, and 33.3%, respectively, and among CoNS was 19%, 35.7%, and 28.6%, respectively. The overall prevalence of iMLSB and cMLSB phenotypes was 18.5% (10/54) and 37% (20/54), respectively. Comparatively, MRSA had more resistance to ciprofloxacin than methicillin-susceptible S. aureus (MSSA) (88.9% vs. 33.3% p = 0.027), while methicillin-resistant coagulase-negative staphylococci (MR-CoNS) had significantly higher resistance to gentamicin (35.7% vs. 7.1% p= 0.005), and trimethoprim-sulfamethoxazole (78.6% vs. 50% p=0.007) than methicillin-susceptible coagulase-negative staphylococci (MS-CoNS). The high prevalence of methicillin and inducible clindamycin resistance in this study points out a potential rise in treatment failures, prolonged hospitalization, and limited treatment options. Thus, emphasizes the importance of antibiotic stewardship and laboratory-guided antibiotic decisions. To address the growing challenge of antibiotic resistance in Tanzania, it is advisable to implement stringent public health measures, including monitoring antibiotic usage, conducting educational initiatives, and raising awareness among patients and healthcare professionals.

Treatment of Methicillin-Resistant Staphylococcus aureus (MRSA) Infection with Rubus multibreatus Le’Vl Leaf Extract

Background: Rubus multibreatus Le’vl is a wild-type shrub of the Rosacea family, commonly used in traditional Chinese medicine. It is claimed to invigorate the kidney and liver and reduce inflammation. From other literature, the Rubus genus has been defined by the presence of diterpene glycosides, with or without the presence of triterpene glycosides, and classifying its phyto-chemical activity owing to a number of oleanane ursane glucosides.&#x0D; Research objectives: To determine whether or not the plant had medicinal properties; To determine the structure of the metabolite(s) responsible for its medicinal properties; To determine the in-vivo activity of the active plant extract and medicinal significance.&#x0D; Study design: Solvent extraction using different solvents with different polarities was used to test for antibacterial activity. The choice solvent extract was tested for metabolites via chemical tests and HPLC. The pure compound(s) identified from HPLC results were tested for antibacterial activity to determine the compound(s) responsible for antibacterial activity. The extent of bacterial inhibition was determined by MBC (minimum bacterial concentration), bacterial growth curve, SDS-PAGE (sodium dodecyl-sulfate polyacrylamide gel electrophoresis), and qPCR (quantitative polymer chain reaction) amplification of viral RNA. The histopathological changes of the liver and kidney, inflammatory cytokines, and IgG were used to explain relief from, or lack thereof, upon treatment with choice plant extract(s).&#x0D; Methodology: Antibacterial activity was determined using both gram-positive and gram-negative bacteria; MSSA S. aureus ATCC25923, E. coli serotype 078, and S. typhi ATCC14028. Different solvent extracts were used to test for its antibacterial activity in vitro. The powdered leaf sample was first macerated in ethanol (90%) and concentrated using different organic solvents with different polarities; ethyl acetate, dichloromethane, and n-butanol. The ethyl acetate leaf extract of the plant, which was rich in flavonoids, phenolic acids, tannins, resins, and saponins, was preferred as the crude extraction method, to the other organic solvents; dichloromethane and n-butanol, whose extracts showed no antibacterial activity towards the gram-positive MSSA S. aureus ATCC25923, E. coli serotype 078 and S. typhi ATCC14028. Only the ethyl acetate extract showed antibacterial activity towards methicillin-susceptible S. aureus (MSSA). Further experiments were done using the methicillin-resistant S. aureus TCH1516 (ATCCBAA-1717) (USA300), which poses a greater threat to the modern-day treatment of bacterial infections. A murine model approach using specific pathogen-free (SPF) mice was used to investigate whether the extract could inhibit S. aureus in-vivo, as it did in-vitro, to determine the bacterial concentration that could cause infection and mortality, and the significance of the plant extract as treatment, during the infection period, both at the beginning of infection and post-infection.&#x0D; Results: The histopathological analyses of the liver and kidney, expression of inflammatory cytokines; IFN-?, TNF-R1, IL-1?, 1L 6, and IgG, showed the significance of the leaf extract in the treatment of methicillin-resistant S. aureus infection. HPLC analyses of the ethyl acetate extract confirmed the presence of 6 compounds; kaempferol, quercetin, gallic acid, ellagic acid, caffeic acid, and ferulic acid, and the absence of rutin. The most active compound of the 6, against S. aureus, was identified to be gallic acid, at a minimum bacterial concentration value (MBC) of 0.1111µg/µL while ellagic acid and ferulic acid followed next at 0.6666µg/µL and 1.7776µg/µL respectively. This, however, is not to say that another compound was not present, that could have inhibited the bacteria. Mass spectroscopic analysis may identify other unknown compounds that could significantly have useful medicinal properties.&#x0D; Conclusion: Rubus multibreatus Le’vl certainly has antibiotic properties against Staphylococcus aureus and gallic, ellagic, and ferulic acids can be attributed to the anti-staphylococcal activity, however, only three bacterial species were used; S. aureus, E. coli and S. typhi, and it was not determined whether the plant or the pure compound metabolites; kaempferol, quercetin, gallic acid, ellagic acid, caffeic acid, and ferulic acid, had other antimicrobial activities; anti-anthelmintic, anti-fungal or anti-viral properties. The histopathological analyses of the liver and kidney, expression of inflammatory cytokines; IFN-?, TNF-R1, IL-1?, 1L 6, and IgG, showed the significance of the leaf extract in the treatment of methicillin-resistant S. aureus infection. Rubus multibreatus Le’vl plant extract improved survival, reduced inflammation in the anal glands, and cleared kidney abscesses. Both IL-6 and IFN-? expression was reduced upon administration of the plant extract, however, IL-6 expression was not reduced when treatment was administered post-infection. IFN-? was significantly reduced in the post-infection group, compared to the positive control group, which expressed 3-4 times as much. R. multibreatus Le’vl was also effective in reducing neutrophilia and necrosis, and overall preventing the formation of bacterial-like cells as seen in the liver of the positive control group.

Macrolide-Lincosamide Resistance and Virulence Genes in Staphylococcus aureus Isolated from Clinical Specimens in Ardabil, Iran.

Staphylococcus aureus causes various hospital- and community-acquired infections. This study aimed to investigate the phenotypic and genotypic characteristics of erythromycin and inducible clindamycin resistance, virulence gene profiles, and spa types of S. aureus isolates collected from patients in Ardabil Province, Iran. A total of 118 clinical S. aureus isolates, including 50 (42.4%) methicillin-resistant S. aureus (MRSA) and 68 (57.6%) methicillin-susceptible S. aureus (MSSA) strains, were investigated. Resistance patterns were determined by the disk diffusion method and minimum inhibitory concentration (MIC) test. Inducible macrolide-lincosamide-streptogramin B (iMLSB) resistance was detected using D-test method. The polymerase chain reaction (PCR) was used to identify the virulence and resistance-encoding genes. Additionally, the spa types of the isolates were determined using the PCR, followed by sequencing. In total, 49.1% (58/118) and 44% (52/118) of the isolates were resistant to erythromycin and clindamycin, respectively. Overall, 13.5% (16/118) of the isolates showed the iMLSB resistance phenotype. The ermC gene (72.4% [42]) was the most frequent erythromycin resistance-encoding gene, followed by ermA (60.3% [35]), ermB (60.3% [35]), ermTR (51.7% [30]), and msrA (15.5% [9]) genes among erythromycin-resistant isolates. The virulence genes hla, hld, sea, LukS PV, tst, seb, sed, eta, sec, and etb were detected in 93.2%, 74.5%, 70.3%, 32.2%, 29.6%, 17%, 8.5%, 8.5%, 5.9%, and 4.2% of the isolates, respectively. Ten different spa types were identified for 58 erythromycin-resistant S. aureus strains, of which t030 and t078 types were the most common types. A high frequency of macrolide- and lincosamide-resistant S. aureus isolates with different genetic backgrounds of resistance and virulence may be found in patients in Ardabil Province, Iran.

Accessory gene regulators and virulence genes associated with the pathogenicity of Staphylococcus aureus from clinical and community settings in Lagos, Nigeria

Staphylococcus aureus is a prominent pathogen that causes serious community and hospital-acquired infections globally. Its pathogenicity is attributed to a variety of secreted and cell surface associated proteins that are modulated by the quorum-sensing accessory gene regulator (agr) system. In this study, we investigated the presence of toxin genes and agr involved with S. aureus from clinical samples and apparently healthy individuals. Unequivocal identification of the isolates was obtained with the Vitek 2 system. We screened 70 clinical (CL) and 22 community (C) S. aureus strains for the methicillin resistance (mecA) gene, agr and superantigens (SAg) (enterotoxins and toxic shock syndrome toxin-1) using PCR techniques. A total of 12 clinical isolates were classified as methicillin-resistant S. aureus (MRSA); 89 isolates belonged to one of the four agr groups (agr1-4), and 3 isolates were non-typeable. Of the agr groups, agr1 was the most prominent and mostly consisted of isolates from pus/wounds. The methicillin-susceptible S. aureus (MSSA) isolates were distributed within the four agr groups while MRSA strains were restricted to agr1 and agr3. The most common enterotoxin gene, sei, was likewise more prevalent in MSSA strains than in MRSA strains, where sea predominated. The co-existence of two or more enterotoxins was confirmed in 40% of the isolates. sea occurred through all the agr groups except agr3 and sei was not found in agr1 and agr4. The toxic shock toxin (tst) gene was detected in six MSSA. These findings suggest that MSSA may cause more lethal infections than MRSA because of the increased frequency of toxic genotypes seen in MSSA strains. Significance: Isolates in the agr1,3 groups had more SAg toxin genes, whereas isolates in the agr4 groups possessed more tst genes. The MSSA isolates contained higher proportions of virulence genes than MRSA. The clinical implications of this discovery include that MSSA may cause more lethal infections than MRSA due to the greater number of toxigenic genotypes discovered.