Towards New Scaffolds for Antimicrobial Activity-In Silico/In Vitro Workflow Introducing New Lead Compounds.

Trends in Methicillin resistant staphylococcus aureus (MRSA) minimal inhibitory concentration (MIC) to Vancomycin over a 2 year period in a community based hospital

Introduction: Staphylococcus aureus infections in current times have become challenging to treat because of advent of Methicillin Resistant Staphylococcus aureus (MRSA) strains which are concurrently resistant to a wide panel of drugs and posing a threat to clinicians and microbiologists globally. The optimal drug for treatment of such MRSA infections is vancomycin but strains with augmented Minimum Inhibitory concentration (MIC) for this drug also have surfaced.Objectives: To know the frequency of MRSA isolates in various clinical samples with their antimicrobial sensitivity patterns and to equate agar dilution and E-test methods for MIC determination of vancomycin to MRSA strains.Materials and Methods: A total of 50 non repeat clinical isolates of staphylococcus aureus isolates were collected from various clinical specimens and were tested for methicillin resistance using the cefoxitin disc diffusion test (30mg). All MRSA isolates were tested for specific MIC by agar dilution and E-test methods. Results: 29 (58%) isolates were resistant to cefoxitin (MRSA). 13.8% isolates had MIC of 4mg/ml for vancomycin (VISA) by both agar dilution and E-test methods. However by agar dilution method 25 (86.2%) isolates exhibited vancomycin MIC of ? 2 mg/ml and by E-test 68.9% of the isolates showed MIC ? 2 mg/ml.Conclusion: Multidrug resistant MRSA strains are on the rise and alternate drug of choice for these infections; vancomycin also is showing increased MIC so prudent use of this drug is advocated. E-test can detect MRSA strains with intermediate MIC values useful for detection of MIC creep so that vancomycin can be used rationally.

BackgroundWound healing and antibiotic resistance of pathogenic microbes have become global issues with serious consequences for the treatment of infectious diseases.ObjectivesThe present study aimed to evaluate the antibacterial, anti-inflammatory, angiogenic, and wound healing properties of copper nanoparticles (CuNPs) synthesized using Lupinus arcticus extract.MethodsThe green synthesis was conducted using the precipitation method. The antibacterial activity of CuNPs against both methicillin-sensitive and methicillin-resistant Staphylococcus aureus (MRSA) strains was evaluated. The effects of CuNPs on protein leakage, the expression levels of biofilm-related genes [e.g., intracellular adhesion A (icaA), intracellular adhesion D (icaD), and elastin-binding protein (EbpS) genes] in MRSA, as well as its impact on wound healing, angiogenesis, and anti-inflammatory effects, were assessed.ResultsThe CuNPs exhibited a spherical shape with dimensions ranging from 10 to 85 nm. Both CuNPs alone and in combination with gentamicin (GNT) inhibited biofilm formation in MRSA, with minimum biofilm inhibitory concentration (MBIC50) values of 6.6 µg/mL and 0.50 µg/mL for MRSA, respectively. The CuNPs significantly (P < 0.05) downregulated the expression levels of icaA, icaD, and EbpS in MRSA, particularly at half the minimum inhibitory concentration (1/2 MIC) and the minimum inhibitory concentration (MIC). Additionally, CuNPs markedly (P < 0.001) increased protein leakage in MRSA. The CuNPs demonstrated potent in vitro wound healing effects, promoting fibroblast cell proliferation and wound closure in a dose-dependent manner. Our results indicated a significant (P < 0.05) increase in the expression of HLA-G5 and VEGF-A genes in cells exposed to CuNPs. Furthermore, CuNPs reduced the expression levels of inflammatory genes in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells (P < 0.05).ConclusionsThe findings of this experimental test indicate that CuNPs, particularly in conjunction with GNT, exhibits promising antibacterial effects against MRSA without causing cytotoxicity to normal cells. This study also demonstrated that green-synthesized CuNPs possesses significant wound-healing properties through its antibacterial activity, inhibition of biofilm formation, induction of angiogenesis, and reduction of inflammation. However, further experiments are necessary to elucidate the precise mechanisms of action and potential toxicity of CuNPs.

Methicillin-resistant Staphylococcus aureus (MRSA) is a priority pathogen due to its multidrug-resistant characteristics. This study compared the antibacterial, antibiofilm, bacteriolytic, and efflux pump inhibitory effects of Curcuma domestica and Curcuma xanthorrhiza rhizome extracts, both individually and in combination with tetracycline, against MRSA. Antibacterial activity and the combinatory effect with tetracycline were assessed using the microdilution method. Additionally, antibiofilm, bacteriolytic, and efflux pump inhibitory were investigated. Extracts from C. domestica and C. xanthorrhiza exhibited antibacterial effects against MRSA, with Minimum Inhibitory Concentration (MIC) values of 125 and 250 µg/mL, respectively. The combination of C. domestica and tetracycline demonstrated a synergistic interaction, with a Fractional Inhibitory Concentration Index (FICI) of 0.5. In contrast, the combination C. xanthorrhiza and tetracycline showed only an additive effect, with an FICI of 0.6. Computer simulations indicated that bisdemethoxycurcumin exhibited the strongest binding affinity to the protein inhibiting topoisomerase ATPase. Furthermore, when combined with tetracycline, each extract was effective in inhibiting biofilm formation and efflux pump activity in MRSA. This combination also induced cell death by altering membrane permeability. The combination of Curcuma extracts with tetracycline demonstrated enhanced antibacterial activity against MRSA compared to the extracts used alone. HIGHLIGHTS Bisdemethoxycurcumin has the strongest binding affinity to the protein that inhibits topoisomerase ATPase with computer simulations The ethanolic extract of Curcuma xanthorrhiza has additive interaction with tetracycline against MRSA and revealed higher antibacterial activity, antibiofilm, bacteriolytic activity, and inhibit the efflux pump as compared to the extract alone. The combination of domestica extract and tetracycline produced a synergistic effect and reduced the MIC value of tetracycline against MRSA up to 1/32 MIC. GRAPHICAL ABSTRACT

BackgroundDetermination of vancomycin minimum inhibitory concentration (MIC) can influence the agent used to treat methicillin-resistant Staphylococcus aureus (MRSA) infection. We studied diagnostic accuracy using E-test and VITEK® 2 against a gold standard broth microdilution (BMD) methodology, the correlation between methods, and associations between vancomycin MIC and MRSA phenotype from clinical isolates.MethodsMRSA isolates were obtained from April 2012 to December 2013. Vancomycin MIC values were determined prospectively on all isolates by gradient diffusion E-test and automated VITEK® 2. The Clinical and Laboratory Standards Institute reference BMD method was performed retrospectively on thawed frozen isolates. Diagnostic accuracy for detecting less susceptible strains was calculated at each MIC cutoff point for E-Test and VITEK® 2 using BMD ≥1 µg/mL as a standard. The correlation between methods was assessed using Spearman’s rho (ρ). The association between MRSA phenotype and MIC for the three methods was assessed using Fisher’s exact test.ResultsOf 148 MRSA isolates, all except one (E-test =3 µg/mL) were susceptible to vancomycin (MIC of ≤2 µg/mL) irrespective of methodology. MICs were ≥1.0 µg/mL for 9.5% of BMD, 50.0% for VITEK® 2, and 27.7% for E-test. Spearman’s ρ showed weak correlations between methods: 0.29 E-test vs VITEK® 2 (P=0.003), 0.27 E-test vs BMD (P=0.001), and 0.31 VITEK® 2 vs BMD (P=0.002). The optimal cutoff points for detecting BMD-defined less susceptible strains were ≥1.0 µg/mL for E-test and VITEK® 2. E-test sensitivity at this cutoff point was 0.85 and specificity 0.29, while VITEK® 2 sensitivity and specificity were 0.62 and 0.51, respectively. Multiresistant MRSA strains tended to have higher MIC values compared to nonmultiresistant MRSA or epidemic MRSA 15 phenotypes by E-test (Fisher’s exact P<0.001) and VITEK® 2 (Fisher’s exact P<0.001).ConclusionOverall diagnostic accuracy and correlations between MIC methods used in routine diagnostic laboratories and the gold standard BMD showed limited overall agreement. This study helps optimize guidance on the effective use of vancomycin.

Clinical characteristics of vancomycin minimum inhibitory concentration of 2 μg/ml methicillin-resistant Staphylococcus aureus strains isolated from patients with bacteremia

Linezolid is an antimicrobial agent belonging to a new class of antibiotics: the oxazolidinones. It has been approved for the treatment of infections due to grampositive organisms including methicillin-resistant Staphylococcus aureus (MRSA). We report a case of Staphylococcus aureus endocarditis that occurred in a burn patient during treatment with this new antibiotic, despite full in vitro sensitivity. A previously healthy 38-year-old man was referred to our six-bed burn unit 2 h after self immolation with petrol. At entry, physical examination revealed burns estimated to involve 85% of the total body surface. On day 25, his skin became colonized by MRSA and Pseudomonas aeruginosa. MRSA was also isolated from a central venous catheter 5 days later, and two blood cultures taken on day 34 grew MRSA. At this time, no deterioration of the patient’s clinical status was observed, except for a body temperature of 38 C. Cardiac signs were not noted. As investigational therapy, linezolid was started on day 37, first intravenously, then orally at a dose of 600 mg b.i.d. for 16 days. The minimal inhibitory concentration (MIC) of linezolid was 0.75 g/ml at the beginning of treatment and 1.5 g/ml at the end. On day 3 of treatment, one more blood culture resulted positive for MRSA, while MRSA had disappeared from burn wound samples. The patient showed an initial clinical improvement until the last day of linezolid therapy. While still on therapy, fever recurred. Since a blood culture taken on the last day of linezolid treatment again grew MRSA, intravenous vancomycin was administered. At this time, a cardiac murmur was noted and aortic endocarditis was diagnosed by transesophageal echocardiography. The hemodynamic status of the patient then deteriorated; he had to be intubated and mechanically ventilated, and vasoppressor agents were administered. On day 62 following admission, a surgical valve replacement was performed. During surgery, large vegetations were found on the aortic valve extending as an abscess into the ventricular septum. Culture of the native valve grew linezolidsensitive MRSA. Following surgery, the patient completed 4 weeks of vancomycin therapy. He was discharged from hospital on day 120. Linezolid has inhibitory activity against a broad range of gram-positive bacteria, including MRSA. After oral administration, its bioavailability reaches 100% [1]. Its efficacy for treating gram-positive communityor nosocomial-acquired pneumonia as well as soft tissue infections is established [2]. However, data concerning its role in the treatment of severe infections, like endocarditis, are scarce. There is concern about the bacteriostatic property of linzeolid, especially against Staphylococcus spp. However, a Staphylococcus aureus endocarditis model in rabbits showed good results when linezolid trough levels in plasma remained above the MIC for this organism [3]. In humans, successful treatment of vancomycin-resistant Enterococcus endocarditis was reported with oral linezolid given at a dose of 600 mg b.i.d. [4]. Although resistance of a clinical Staphylococcus aureus isolate to linezolid has been reported previously, this did not occur in the case reported here. The strain of Staphylococcus aureus we isolated remained sensitive to linezolid with an MIC value lower than the accepted breakpoint of 4 g/ml [1]. It must be recognized, however, that burn patients are difficult to treat because the pharmacokinetics of many therapeutic agents become altered. In particular, the dose of many antimicrobial E. H. Ben Mansour · E. Jacob · M. Monchi · D. Ledoux · J.-L. Canivet · P. Damas ()) Department of General Intensive Care, University Hospital, Domaine universitaire du Sart-Tilman, 4000 Liege, Belgium e-mail: pdamas@chu.ulg.ac.be Tel.: +32-4-3667495 Fax: +32-4-3668898

Antimicrobial Resistance in the Intensive Care Unit: Mechanisms, Epidemiology, and Management of Specific Resistant Pathogens

Vancomycin is the treatment of choice for serious methicillin-resistant Staphylococcus aureus (MRSA) infections. The area under the concentration-time curve from 0 to 24 hr (AUC24 )/minimum inhibitory concentration (MIC) ratio was recently introduced as a parameter for assessing clinical outcome by S. aureus. This study was purposed to apply the vancomycin AUC24 /MIC in patients with MRSA pneumonia. Forty-seven patients with confirmed lower respiratory infection caused by MRSA during 2011 were enrolled. All patients were treated with vancomycin. Clinical characteristics and laboratory data were collected. AUC24 /MIC values were calculated as previously reported and patients were divided into two groups based on the bacteriologic response, which was eradicated or not, and an AUC24 /MIC value (above or below 400). MRSA infections were eradicated in 39 patients but 8 patients had persistent MSRA infection in the following cultures. The mean AUC24 /MIC values and vancomycin concentrations were not statistically different between patients with and without MRSA eradication. All 13 patients with a vancomycin MIC of 2 mg/L had an AUC24 /MIC below 400. AUC24 /MIC might not be a reliable indicator for assessing treatment response of vancomycin in MRSA pneumonia. Relationship between vancomycin AUC24 /MIC and therapeutic outcome needs to undergo further studies, including sufficiently large sample size.

Synergistic interaction between Chlorella vulgaris extract and Origanum elongatum essential oil against methicillin-resistant Staphylococcus aureus.

Comparison of the antioxidant capacity and the antimicrobial activity of black and green tea

The antibacterial activity of epigallocatechin gallate (EGCg), a catechin, against 53 clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) was evaluated and expressed as minimal inhibitory concentration (MIC). The MIC50 and MIC90 of the strains were found be 64 and 126 micrograms/ml, respectively by the microdilution method. A time-kill study using an isolate showed that EGCg appeared to be bacteriostatic at 1-2 x MIC and bactericidal at 6 x MIC against MRSA. In addition, the activity of EGCg was stable to various physical conditions including boiling or freezing. These findings suggest that EGCg could be a useful agent for treating MRSA infection.

Temu kunci (Kaempferia pandurata (Roxb.)) has a number of benefits and one of these is antibacterial. The rhizome is said to have antibacterial activity against Streptococcus mutans, Lactocillus sp. and Candida albicans. The aim of the study is to test the antibacterial activity of Kaempferia pandurata (Roxb.) rhizome ethanol extract on methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant coagulase negative Staphylococci (MRCNS), methicillin-sensitive Staphylococcus aureus (MSSA), Bacillus subtilis and Salmonella typhi. Antimicrobial activity of the extract was assayed by the microdilution method using Mueller Hinton Broth with sterilized 96 round-bottomed microwells to determine the Minimum Inhibitory Concentration (MIC) as well as to determine the time-kill activity. The MIC of the extract was 16 ppm for both Bacillus subtilis and MRSA; 8 ppm for both MSSA and Salmonella typhi and 4 ppm for MRCNS. Ethanol extract of Kaempferia pandurata (Roxb.) showed antibacterial activity against all the tested bacteria and was the most potent against MRCNS, with MIC 4 ppm. The killing profile test of the extract displayed bactericidal activity at 8-16 ppm against MRSA, MSSA, Bacillus subtilis and Salmonella typhi and bacteriostatic activity at 4 ppm towards MRCNS.

In Vitro Susceptibility of Ciprofloxacin-Resistant Methicillin-Resistant Staphylococcus aureus to Ototopical Therapy.

Determining vancomycin Etest MICs in patients with MRSA bloodstream infection does not support switching antimicrobials