Methicillin-resistant Staphylococcus Aureus Growth Research Articles

Analisis Bioautografi Kromatografi Lapis Tipis dan Aktivitas Antibakteri Ekstrak Etanol Bawang Tiwai (Eleutherine bulbosa (Mill.) Urb.) terhadap Methicillin-resistant Staphylococcus aureus (MRSA)

Methicillin-resistant Staphylococcus aureus (MRSA) infections are the major health problem in Indonesia; this is mainly due to their resistance to antibiotics. Based on this, the quest for new sources of natural based antimicrobial drugs is necessary. Bawang tiwai (Eleutherine bulbosa (Mill.) Urb.) is one of the natural materials that have potential as an antibacterial natural-based of Indonesia origin. Bawang tiwai already used empirically by local communities in East Kalimantan to treat various diseases. The aim of this research is to know the antibacterial activity of E. bulbosa ethanol extract on MRSA and to know the type of secondary metabolite with antibacterial activity tested by TLC bioautography method. The experiment was conducted on Research Laboratory, Faculty of Medicine, Mulawarman University, Samarinda. TLC results showed that ethanol extract of E. bulbosa has compounds containing sugar, alkaloids, steroids, and flavonoids. The results of TLC bioautography show that ethanol extract of E. bulbosa can inhibit the growth of MRSA. MIC results show that ethanol extract of E. bulbosa has potent antibacterial activity against MRSA with MIC 1 mg/mL. The conclusion of this research is all the results support the potential of bawang tiwai as the alternative component of natural-based antibacterial agents against MRSA.

Anti-methicillin resistant Staphylococcus aureus (MRSA) activity of an acetone extract from the leaves of Canarium odontophyllum (Miq.)

Methicillin-resistant Staphylococcus aureus (MRSA) is a global health concern that has caused nosocomial and community infections over the past decade. The emergence of multi-drug resistant strains and limitations of present antimicrobial drugs have led to continuous search for natural products as curative agents for MRSA infections. Canarium odontophyllum Miq., locally known as dabai, has been considered an alternative phytotherapeutic treatment for MRSA. The aim of this study was to evaluate the bacteriostatic activity of an acetone extract from C. odontophyllum leaves against MRSA. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the extract against the ATCC 33591 and Mu50 strains were determined using the broth microdilution method, and a time-kill assay was employed to assess the type of bacteriostatic action of the extract against the Mu50 strain only. The MIC and MBC values of the extract against Mu50 were 312.5 µg/ml and 625 µg/ml, respectively, whereas the MIC and MBC values for ATCC 33591 were 625 µg/ml and 1,250 µg/ml, respectively, confirming the bacteriostatic effect against both MRSA strains. A time-kill assay showed that the acetone extract of C. odontophyllum leaves exhibited concentrationdependent bacteriostatic action against the Mu50 strain at 1/2× MIC, 1× MIC and 2× MIC. However, the extract was bactericidal only at the highest concentration (4× MIC) with a reduction in cell viability of more than 3 log10 within 24 hours. These findings confirm that an acetone extract from C. odontophyllum leaves inhibited growth of MRSA at low concentration and could be utilised as an alternative anti-MRSA agent in immune uncompromised hosts.

A Novel Antimicrobial Coating Represses Biofilm and Virulence-Related Genes in Methicillin-Resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) has become an important cause of hospital-acquired infections worldwide. It is one of the most threatening pathogens due to its multi-drug resistance and strong biofilm-forming capacity. Thus, there is an urgent need for novel alternative strategies to combat bacterial infections. Recently, we demonstrated that a novel antimicrobial surface coating, AGXX®, consisting of micro-galvanic elements of the two noble metals, silver and ruthenium, surface-conditioned with ascorbic acid, efficiently inhibits MRSA growth. In this study, we demonstrated that the antimicrobial coating caused a significant reduction in biofilm formation (46%) of the clinical MRSA isolate, S. aureus 04-02981. To understand the molecular mechanism of the antimicrobial coating, we exposed S. aureus 04-02981 for different time-periods to the coating and investigated its molecular response via next-generation RNA-sequencing. A conventional antimicrobial silver coating served as a control. RNA-sequencing demonstrated down-regulation of many biofilm-associated genes and of genes related to virulence of S. aureus. The antimicrobial substance also down-regulated the two-component quorum-sensing system agr suggesting that it might interfere with quorum-sensing while diminishing biofilm formation in S. aureus 04-02981.

The Antibacterial Activity of Dayak Onion (Eleutherine palmifolia (L.) Merr) towards Pathogenic Bacteria.

Antibacterial activity of indigenous Dayak onion (Eleutherine palmifolia (L.) Merr) was investigated. The Dayak onion was solvent extracted with n-hexane, ethyl acetate, and ethanol 96% consecutively. Each extract was tested its antibacterial activity towards methicillin-resistant Staphylococcus aureus (MRSA), Bacillus cereus, Shigella sp., and Pseudomonas aeruginosa using disc diffusion method. The test results showed that the n-hexane, ethyl acetate, and ethanol 96% extracts positively inhibited the growth of MRSA, B. cereus, Shigella sp., and P. aeruginosa. The highest inhibition activity of each extract was obtained with 10 mg/mL of extract concentration; whereas the minimum inhibitory concentration (MIC) of each extract was 2 mg/mL. Extract with the highest inhibition activity was ethyl acetate extract against B. cereus (139.58%). TLC evaluation of ethyl acetate extract showed four spots and bioautography indicated that ethyl acetate extract contained four types of compounds with inhibition activity against B. cereus, in which two compounds have higher antibacterial activity than the other two.

Understanding the antimicrobial activity of selected disinfectants against methicillin-resistant Staphylococcus aureus (MRSA).

Disinfectants and biocidal products have been widely used to combat Methicillin-resistant Staphylococcus aureus (MRSA) infections in homes and healthcare environments. Although disruption of cytoplasmic membrane integrity has been documented as the main bactericidal effect of biocides, little is known about the biochemical alterations induced by these chemical agents. In this study, we used Fourier transform infrared (FT-IR) spectroscopy and chemometric tools as an alternative non-destructive technique to determine the bactericidal effects of commonly used disinfectants against MRSA USA-300. FTIR spectroscopy permits a detailed characterization of bacterial reactivity, allowing an understanding of the fundamental mechanism of action involved in the interaction between bacteria and disinfectants. The disinfectants studied were ethanol 70% (N = 5), isopropanol (N = 5), sodium hypochlorite (N = 5), triclosan (N = 5) and triclocarban (N = 5). Results showed less than 5% colony forming units growth of MRSA treated with triclocarban and no growth in the other groups. Nearly 70,000 mid-infrared spectra from the five treatments and the two control (untreated; N = 4) groups of MRSA (bacteria grown in TSB and incubated at 37°C (Control I) / at ambient temperature (Control II), for 24h) were pre-processed and analyzed using principal component analysis followed by linear discriminant analysis (PCA-LDA). Clustering of strains of MRSA belonging to five treatments and the discrimination between each treatment and two control groups in MRSA (untreated) were investigated. PCA-LDA discriminatory frequencies suggested that ethanol-treated spectra are the most similar to isopropanol-treated spectra biochemically. Also reported here are the biochemical alterations in the structure of proteins, lipid membranes, and phosphate groups of MRSA produced by sodium hypochlorite, triclosan, and triclocarban treatments. These findings provide mechanistic information involved in the interaction between MRSA strains and hygiene products; thereby demonstrating the potential of spectroscopic analysis as an objective, robust, and label-free tool for evaluating the macromolecular changes involved in disinfectant-treated MRSA.

A unique indolizinium alkaloid streptopertusacin A and bioactive bafilomycins from marine-derived Streptomyces sp. HZP-2216E

Streptopertusacin A, a unique indolizinium alkaloid existing as a zwitterion, and six bafilomycins including two previously undescribed ones of 21,22-en-bafilomycin D and 21,22-en-9-hydroxybafilomycin D were isolated from a culture of the seaweed-derived Streptomyces sp. HZP-2216E. Structures of these isolated compounds were determined based on extensive NMR spectroscopic analyses, HRESIMS and MS-MS data. The stereochemical assignments were achieved by NOE information, chemical degradation, Marfey's method, and electronic circular dichroism (ECD) calculation. Streptopertusacin A is the first example of this type of indolizinium alkaloid from microorganisms and showed moderate activity against the growth of methicillin-resistant Staphylococcus aureus (MRSA). 21,22-en-bafilomycin D and 21,22-en-9-hydroxybafilomycin D had potent activities in inhibiting the proliferation of glioma cells and the growth of MRSA.

First-In-Class Inhibitor of Ribosomal RNA Synthesis with Antimicrobial Activity against Staphylococcus aureus

We report the discovery of the first bacterial ribosomal RNA (rRNA) synthesis inhibitor that has specific antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA). A pharmacophore model was constructed on the basis of the protein-protein interaction between essential bacterial rRNA transcription factors NusB and NusE and employed for an in silico screen to identify potential leads. One compound, (E)-2-{[(3-ethynylphenyl)imino]methyl}-4-nitrophenol (MC4), demonstrated antimicrobial activity against a panel of S. aureus strains, including MRSA, without significant toxicity to mammalian cells. MC4 resulted in a decrease in the rRNA level in bacteria, and the target specificity of MC4 was confirmed at the molecular level. Results obtained from this work validated the bacterial rRNA transcription machinery as a novel antimicrobial target. This approach may be extended to other factors in rRNA transcription, and MC4 could be applied as a chemical probe to dissect the relationship among MRSA infection, MRSA growth rate, and rRNA synthesis, in addition to its therapeutic potential.

A novel STK1-targeted small-molecule as an \u201cantibiotic resistance breaker\u201d against multidrug-resistant Staphylococcus aureus

Ser/Thr protein kinase (STK1) plays a critical role in cell wall biosynthesis of and drug resistance in methicillin-resistant Staphylococcus aureus (MRSA). MRSA strains lacking STK1 become susceptible to failing cephalosporins, such as Ceftriaxone and Cefotaxime. STK1, despite being nonessential protein for MRSA survival, it can serve as an important therapeutic agent for combination therapy. Here, we report a novel small molecule quinazoline compound, Inh2-B1, which specifically inhibits STK1 activity by directly binding to its ATP-binding catalytic domain. Functional analyses encompassing in vitro growth inhibition of MRSA, and in vivo protection studies in mice against the lethal MRSA challenge indicated that at high concentration neither Inh2-B1 nor Ceftriaxone or Cefotaxime alone was able to inhibit the growth of bacteria or protect the challenged mice. However, the growth of MRSA was inhibited, and a significant protection in mice against the bacterial challenge was observed at a micromolar concentration of Ceftriaxone or Cefotaxime in the presence of Inh2-B1. Cell-dependent minimal to no toxicity of Inh2-B1, and its abilities to down-regulate cell wall hydrolase genes and disrupt the biofilm formation of MRSA clearly indicated that Inh2-B1 serves as a therapeutically important “antibiotic-resistance-breaker,” which enhances the bactericidal activity of Ceftriaxone/Cefotaxime against highly pathogenic MRSA infection.

Antimicrobial effects of lysophosphatidylcholine on methicillin-resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) is an important health care-associated and community-associated pathogen and causes a large number of infections worldwide. For the purpose of application to topical treatment of MRSA infection, we examined the antimicrobial effects of lysophosphatidylcholine (LPC) on MRSA strains. We also investigated the combination effect of LPC and gentamicin on MRSA growth. The LPC minimum inhibitory concentrations (MIC) for Gram-positive (S. aureus, Staphylococcus epidermidis, and Streptococcus pneumoniae) and Gram-negative (Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae, and Pseudomonas aeruginosa) bacteria were measured by the broth microdilution method. The mechanism of LPC-mediated MRSA killing was investigated by membrane permeability analysis with DiSC3(5) fluorescence and growth curve analysis. Lastly, the effects of LPC on gentamicin-induced bactericidal activity were determined in combination treatment studies with 15 gentamicin-resistant MRSA isolates from the skin, nose, or ears. The LPC MIC for Gram-positive bacteria varied between 32 µg/ml and >2048 µg/ml, whereas that for all Gram-negative bacteria was >2048 µg/ml. Consistently, membrane permeability analysis showed that LPC was substantially more effective in inducing membrane permeability in Gram-positive bacteria than in Gram-negative counterparts. Growth curve analysis in cotreatment studies demonstrated that LPC has intrinsic bactericidal effects and can also potentiate gentamicin sensitivity in resistant MRSA strains. Our study demonstrates that LPC exhibits intrinsic antimicrobial effects and can enhance the antimicrobial effects of gentamicin for resistant MRSA strains, suggesting that LPC may be a beneficial additive in topical antibiotics for superficial skin infections.

Effect of Rocket (Eruca sativa) Extract on MRSA Growth and Proteome: Metabolic Adjustments in Plant-Based Media.

The emergence of methicillin-resistant Staphylococcus aureus (MRSA) in food has provoked a great concern about the presence of MRSA in associated foodstuff. Although MRSA is often detected in various retailed meat products, it seems that food handlers are more strongly associated with this type of food contamination. Thus, it can be easily postulated that any food could be contaminated with this pathogen in an industrial environment or in household and cause food poisoning. To this direction, the effect of rocket (Eruca sativa) extract on MRSA growth and proteome was examined in the present study. This goal was achieved with the comparative study of the MRSA strain COL proteome, cultivated in rocket extract versus the standard Luria-Bertani growth medium. The obtained results showed that MRSA was able to grow in rocket extract. In addition, proteome analysis using 2-DE method showed that MRSA strain COL is taking advantage of the sugar-, lipid-, and vitamin-rich substrate in the liquid rocket extract, although its growth was delayed in rocket extract compared to Luria–Bertani medium. This work could initiate further research about bacterial metabolism in plant-based media and defense mechanisms against plant-derived antibacterials.

Dual-Targeting Small-Molecule Inhibitors of the Staphylococcus aureus FMN Riboswitch Disrupt Riboflavin Homeostasis in an Infectious Setting

Riboswitches are bacterial-specific, broadly conserved, non-coding RNA structural elements that control gene expression of numerous metabolic pathways and transport functions essential for cell growth. As such, riboswitch inhibitors represent a new class of potential antibacterial agents. Recently, we identified ribocil-C, a highly selective inhibitor of the flavin mononucleotide (FMN) riboswitch that controls expression of de novo riboflavin (RF, vitamin B2) biosynthesis in Escherichia coli. Here, we provide amechanistic characterization of the antibacterial effects of ribocil-C as well as of roseoflavin (RoF), an antimetabolite analog of RF, among medically significant Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) and Enterococcus faecalis. We provide genetic, biophysical, computational, biochemical, and pharmacological evidence that ribocil-C and RoF specifically inhibit dual FMN riboswitches, separately controlling RF biosynthesis and uptake processes essential for MRSA growth and pathogenesis. Such a dual-targeting mechanism is specifically required to develop broad-spectrum Gram-positive antibacterial agents targeting RF metabolism.

Atomic Layer Deposition of a Silver Nanolayer on Advanced Titanium Orthopedic Implants Inhibits Bacterial Colonization and Supports Vascularized de Novo Bone Ingrowth.

Joint replacement surgery is associated with significant morbidity and mortality following infection with either methicillin-resistant Staphylococcus aureus (MRSA) or Staphylococcus epidermidis. These organisms have strong biofilm-forming capability in deep wounds and on prosthetic surfaces, with 103 -104 microbes resulting in clinically significant infections. To inhibit biofilm formation, we developed 3D titanium structures using selective laser melting and then coated them with a silver nanolayer using atomic layer deposition. On bare titanium scaffolds, S. epidermidis growth was slow but on silver-coated implants there were significant further reductions in both bacterial recovery (p < 0.0001) and biofilm formation (p < 0.001). MRSA growth was similarly slow on bare titanium scaffolds and not further affected by silver coating. Ultrastructural examination and viability assays using either human bone or endothelial cells, demonstrated strong adherence and growth on titanium-only or silver-coated implants. Histological, X-ray computed microtomographic, and ultrastructural analyses revealed that silver-coated titanium scaffolds implanted into 2.5 mm defects in rat tibia promoted robust vascularization and conspicuous bone ingrowth. We conclude that nanolayer silver of titanium implants significantly reduces pathogenic biofilm formation in vitro, facilitates vascularization and osseointegration in vivo making this a promising technique for clinical orthopedic applications.

Titanium surface functionalization with coatings of chitosan and polyphenol-rich plant extracts

Coating biomedical implant surfaces with biopolymers is an easy and inexpensive way to impart functionalities. Numerous biocompatible biopolymers, including cationic crustacean-derived chitosans, have been used. Here, substrates of Titanium (Ti), commonly used for bone contact applications, were coated with chitosan and one of three polyphenol-rich plant extracts (PPrPE) and characterized physicochemically. Hela cell adhesion and growth of methicillin-resistant Staphylococcus aureus (MRSA) were studied. Chitosan and PPrPE on surfaces were detected by FTIR and XPS. Chitosan coatings, both with and without PPrPE functionalization, did not inhibit MRSA growth and promoted Hela cell adhesion. The effect of PPrPE functionalization remained unclear.

Eradication and Sensitization of Methicillin Resistant Staphylococcus aureus to Methicillin with Bioactive Extracts of Berry Pomace.

The therapeutic roles of phenolic blueberry (Vaccinium corymbosum) and blackberry (Rubus fruticosus) pomace (commercial byproduct) extracts (BPE) and their mechanism of actions were evaluated against methicillin resistant Staphylococcus aureus (MRSA). Five major phenolic acids of BPE, e.g., protocatechuic, p. coumaric, vanillic, caffeic, and gallic acids, as well as crude BPE completely inhibited the growth of vegetative MRSA in vitro while BPE+methicillin significantly reduced MRSA biofilm formation on plastic surface. In addition, BPE restored the effectiveness of methicillin against MRSA by down-regulating the expression of methicillin resistance (mecA) and efflux pump (norA, norB, norC, mdeA, sdrM, and sepA) genes. Antibiogram with broth microdilution method showed that MIC of methicillin reduced from 512 μg/mL to 4 μg/mL when combined with only 200 μg Gallic Acid Equivalent (GAE)/mL of BPE. Significant reduction in MRSA adherence to and invasion into human skin keratinocyte Hek001 cells were also noticed in the presence of BPE. BPE induced anti-apoptosis and anti-autophagy pathways through overexpression of Bcl-2 gene and down-regulation of TRADD and Bax genes (inducers of apoptosis pathway) in Hek001 cells. In summary, novel and sustainable prophylactic therapy can be developed with BPE in combination with currently available antibiotics, especially methicillin, against skin and soft tissue infections with MRSA.

Novel long-chain compounds with both immunomodulatory and MenA inhibitory activities against Staphylococcus aureus and its biofilm

Menaquinone (MK) biosynthesis pathway is a potential target for evaluating antimicrobials in gram-positive bacteria. Here, 1,4-dihydroxy-2-naphthoate prenyltransferase (MenA) was targeted to reduce methicillin-resistant Staphylococcus aureus (MRSA) growth. MenA inhibiting, long chain-based compounds were designed, synthesized and evaluated against MRSA and menaquinone utilizing bacteria in aerobic conditions. The results showed that these bacteria were susceptible to most of the compounds. Menaquinone (MK-4) supplementation rescued MRSA growth, suggesting these compounds inhibit MK biosynthesis. 3a and 7c exhibited promising inhibitory activities with MICs ranging 1–8 μg/mL against MRSA strains. The compounds did not facilitate small colony variant formation. These compounds also inhibited the biofilm growth by MRSA at high concentration. Compounds 3a, 6b and 7c displayed a promising extracellular bactericidal activity against MRSA at concentrations equal to and four-fold less than their respective MICs. We also observed cytokines released from THP-1 macrophages treated with compounds 3a, 6b and 7c and found decreases in TNF-α and IL-6 release and increase in IL-1β. These data provide evidence that MenA inhibitors act as TNF-α and IL-6 inhibitors, raising the potential for development and application of these compounds as potential immunomodulatory agents.

Action of antibiotic oxacillin on invitro growth of methicillin-resistant Staphylococcus aureus (MRSA) previously treated with homeopathic medicines.

Resistance to antibiotics is a major public health concern worldwide. New treatment options are needed and homeopathy is one such option. We sought to assess the effect of the homeopathic medicine Belladonna (Bell) and a nosode (biotherapy) prepared from a multi-drug resistant bacterial species, methicillin-resistant Staphylococcus aureus (MRSA), on the same bacterium. Bell and MRSA nosode were prepared in 6cH and 30cH potencies in 30% alcohol and sterile water, according to the Brazilian Homeopathic Pharmacopeia and tested on MRSA National Collection of Type Cultures (NCTC) 10442. We assessed invitro bacterial growth, deoxyribonuclease (DNAase) and hemolysin activity, and invitro bacterial growth in combination with oxacillin (minimum inhibitory concentration - MIC). All values were compared to control: 30% alcohol and water. Invitro growth of MRSA was statistically significantly inhibited in the presence of Bell and nosode 6cH and 30cH compared to controls (p<0.0001); and with combination of Bell or nosode 6cH and 30cH and oxacillin (p<0.001). Bell 30cH and nosode 6cH and 30cH significantly decreased bacterial DNAse production (p<0.001) and reduced red blood cell lysis. Cultures of MRSA treated with Belladonna or MRSA nosode exhibited reduced growth invitro, reduced enzymatic activity and became more vulnerable to the action of the antibiotic oxacillin. Further studies are needed on the biomolecular basis of these effects.

Significant antibacterial activity and synergistic effects of camel lactoferrin with antibiotics against methicillin-resistant Staphylococcus aureus (MRSA)

Methicillin-resistant Staphylococcus aureus (MRSA) causes major healthcare problems in many countries, as it is present as several hospital- and community-associated strains. Hospital-associated MRSA is one of the most prevalent nosocomial pathogens throughout the world and infections caused by community-acquired MRSA are rising. This emphasizes the need for new and efficient anti-MRSA agents. We evaluated the antibacterial effects of camel lactoferrin (cLf) and human lactoferrin (hLf) alone and in combination with several antibiotics against MRSA. Antimicrobials were tested against MRSA and an S. aureus control strain by the agar disc diffusion method. The minimum inhibitory concentration (MIC) was determined for antimicrobials by the broth microdilution method. Synergy between cLf or hLf and antibiotics was examined by checkerboard and time-kill assays. The agar disc diffusion assay showed that MRSA growth was inhibited by cLf at 0.25–3 mg/ml and hLf at 1–3 mg/ml. cLf demonstrated 3 times higher inhibitory activity against MRSA than hLf in terms of MIC values (250 vs. 750 μg/ml, respectively). Biotinylated cLf was recognized by two membrane proteins of MRSA, 66–67 KDa. Combinations of cLf or hLf and oxacillin or vancomycin at sub-MIC levels enhanced in vitro antibacterial activity against MRSA compared with each agent alone.

Fingernail Carriage of Methicillin-Resistant Staphylococcus aureus and Possible Correlation with Soft Tissue Infections in Children.

Community-associated methicillin-resistant Staphylococcus aureus (MRSA) is a growing problem in the pediatric population, causing many soft tissue infections. This study was designed to examine fingernail carriage of MRSA in children and their caregivers as a possible link to community-associated MRSA soft tissue infections in children. We documented the prevalence of MRSA under the fingernails of children and the caregivers of pediatric patients with soft tissue infections and compared the prevalence with MRSA under the fingernails of children and the caregivers of children with no history of soft tissue infections. Children with soft tissue infections and their caregivers (50 subjects) had three fingernails of each hand swabbed and plated and these were compared with a control group of children and their caregivers (150 subjects) who had no history of MRSA or soft tissue infection. Caregivers and children in the study group were more likely than caregivers and the children in the control group to have MRSA under their fingernails (P < 0.05). Soft tissue infections in the study group were found most commonly in the diapering area (66%). MRSA carriage was evident under the fingernails of children and caregivers. Caregivers and their children who have soft tissue infections are more likely to have MRSA growth under fingernails than caregivers or their children who have no history of MRSA or soft tissue infections. Our study suggests that caregivers could be contributing to soft tissue infections in their children.

Nano-thick calcium oxide armed titanium: boosts bone cells against methicillin-resistant Staphylococcus aureus.

Since the use of systemic antibiotics for preventing acute biomaterial-associated infections (BAIs) may build up bacterial resistance and result in huge medical costs and unpredictable mortality, new precaution strategies are required. Here, it demonstrated that titanium armed with a nano-thick calcium oxide layer was effective on averting methicillin-resistant Staphylococcus aureus (MRSA) infections in rabbits. The calcium oxide layer was constructed by, firstly, injecting of metallic calcium into titanium via a plasma immersion ion implantation process, and then transforming the outer most surface into oxide by exposing to the atmosphere. Although the calcium oxide armed titanium had a relative low reduction rate (~74%) in growth of MRSA in vitro, it could markedly promote the osteogenic differentiation of bone marrow stem cells (BMSCs), restore local bone integration against the challenge of MRSA, and decrease the incidence of MRSA infection with a rate of 100% (compared to the titanium control). This study demonstrated for the first time that calcium, as one of the major elements in a human body, could be engineered to avert MRSA infections, which is promising as a safe precaution of disinfection for implantable biomedical devices.

Anti-methicillin Resistant Staphylococcus aureus Compound Isolation from Halophilic Bacillus amyloliquefaciens MHB1 and Determination of Its Mode of Action Using Electron Microscope and Flow Cytometry Analysis.

The aim of this study was to purify, characterize and evaluate the antibacterial activity of bioactive compound against methicillin-resistant Staphylococcus aureus (MRSA). The anti-MRSA compound was produced by a halophilic bacterial strain designated as MHB1. The MHB1 strain exhibited 99% similarity to Bacillus amyloliquefaciens based on 16S rRNA gene analysis. The culture conditions of Bacillus amyloliquefaciens MHB1 were optimized using nutritional and environmental parameters for enhanced anti-MRSA compound production. The pure bioactive compound was isolated using silica gel column chromatography and Semi-preparative High-performance liquid chromatography (Semi-preparative HPLC). The Thin layer chromatography, Fourier transform infrared spectroscopy and proton NMR ((1)H NMR) analysis indicated the phenolic nature of the compound. The molecular mass of the purified compound was 507Da as revealed by Liquid chromatography-mass spectrometry (LC-MS) analysis. The compound inhibited the growth of MRSA with minimum inhibitory concentration (MIC) of 62.5µgmL(-1). MRSA bacteria exposed to 4× MIC of the compound and the cell viability was determined using flow cytometric analysis. Scanning electron microscope and Transmission electron microscope analysis was used to determine the ultrastructural changes in bacteria. This is the first report on isolation of anti-MRSA compound from halophilic B. amyloliquefaciens MHB1 and could act as a promising biocontrol agent.