Bioguided Isolation of Antibiofilm and Antibacterial Pregnane Glycosides from Caralluma quadrangula: Disarming Multidrug-Resistant Pathogens.

Methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant Acinetobacter baumannii (MDRAB) present a serious challenge because of their capability to cause biofilm resistance to commonly used antibiotics producing chronic infections and hindering the process of wound healing. In the current study, we investigated the antibacterial activity of Caralluma quadrangula extracts (MeOH, and its fractions CH2Cl2 and n-butanol) against multidrug-resistant MRSA USA300 and A. baumannii AB5057. In vitro, the MeOH extract and both fractions of C. quadrangula significantly inhibited biofilm formation and disrupted previously established biofilm by MRSA and MDRAB at all the tested concentrations (0.625, 0.313, and 0.156 mg/mL). In vivo, C. quadrangula extracts successfully decreased bacterial loads in MRSA-infected skin lesions in mice. Four pregnane glycosides and one flavone glycoside were isolated from the bioactive n-butanol fraction. The isolated compounds (Rus A-E) were tested for their biofilm inhibition and biofilm detachment activities. The results revealed that Rus C was the most active compound (IC50 = 0.139 mmole), while Rus E was the least active (IC50 = 0.818 mmole). These results support the potential use of C. quadrangula extracts or their isolated compounds for hindering the biofilm attachment and the virulence of MRSA and MDRAB and their application as a topical antimicrobial preparation for MRSA skin infections.

In vivo Antibacterial Activity of Star Anise (Illicium verum Hook.) Extract Using Murine MRSA Skin Infection Model in Relation to Its Metabolite Profile.

INTRODUCTION: Star anise fruits (Illicium verum Hook.) have been used as an important treatment in traditional Chinese medicine. The previous studies reported the activity of the non-polar fractions as potential sources of antibacterial metabolites, and little was done concerning the polar fractions of star anise. METHODS: The antibacterial activity of the star anise aqueous methanolic (50%) extract against multidrug-resistant Acinetobacter baumannii AB5057 and methicillin-resistant Staphylococcus aureus (MRSA USA300) was investigated in vitro (disc diffusion assay, minimum bactericidal concentration determination, anti-biofilm activity and biofilm detachment activity). The antibacterial activity was further tested in vivo using a murine model of MRSA skin infection. Ultra-performance liquid chromatography coupled to high-resolution mass spectrometry (UPLC/HRMS) approach was applied for the identification of the metabolites responsible for the antibacterial activity. The antioxidant potential was evaluated using five in vitro assays: TAC (total antioxidant capacity), DPPH, ABTS, FRAP (ferric reducing antioxidant power) and iron-reducing power. RESULTS: In vitro, star anise aqueous methanolic extract showed significant inhibition and detachment activity against biofilm formation by the multidrug-resistant and highly virulent Acinetobacter baumannii AB5057 and MRSA USA300. The topical application of the extract in vivo significantly reduced the bacterial load in MRSA-infected skin lesions. The extract showed strong antioxidant activity using five different complementary methods. More than seventy metabolites from different classes were identified: phenolic acids, phenylpropanoids, sesquiterpenes, tannins, lignans and flavonoids. CONCLUSION: This study proposes the potential use of star anise polar fraction in anti-virulence strategies against persistent infections and for the treatment of staphylococcal skin infections as a topical antimicrobial agent. To our knowledge, our research is the first to provide the complete polar metabolome list of star anise in an approach to understand the relationship between the chemistry of these metabolites and the proposed antibacterial activity.

Optimization and enhancement of textile reactive Remazol black B decolorization and detoxification by environmentally isolated pH tolerant Pseudomonas aeruginosa KY284155.

Azo dyes are complex derivatives of diazene used in food and textile manufacture. They are highly recalcitrant compounds, and account for severe environmental and health problems. Different strains of Pseudomonas species were isolated from textile wastewater effluents. The bioconversion of Remazol black B (a commonly used water soluble dye) by Pseudomonas aeruginosa was observed in static conditions. The bio-decolorization process was optimized by a multi factorial Plackett-Burman experimental design. Decolorization of 200 mg L-1 reached 100% in 32 h. Interestingly, the presence of yeast extract, magnesium and iron in the culture media, highly accelerated the rate of decolorization. Moreover, one of our isolates, P. aeruginosa KY284155, was kept high degradation rates at high pH (pH = 9), which represents the pH of most textile wastewater effluents, and was able to tolerate high concentration of dye up to 500 mg L-1. In bacteria, azo-dye degradation is often initiated by reductive azo compound cleavage catalyzed by azo-reductases. Three genes encoding azo-reductases, paazoR1, paazoR2 and paazoR3, could be identified in the genome of the isolated P. aeruginosa stain (B1). Bioinformatics analyses of the paazoR1, paazoR2 and paazoR3 genes reveal their prevalence and conservation in other P. aeruginosa strains. Chemical oxygen demand dramatically decreased and phyto-detoxification of the azo dye was accomplished by photocatalytic post treatment of the biodegradation products. We suggest applying combined biological photocatalytic post treatment for azo dyes on large scale, for effective, cheap decolorization and detoxification of azo-dyes, rendering them safe enough to be discharged in the environment.

Fluoroquinolone resistant mechanisms in methicillin-resistant Staphylococcus aureus clinical isolates in Cairo, Egypt.

INTRODUCTION: Methicillin-resistant Staphylococcus aureus (MRSA) is a persistent problem in community and health care settings. Fluoroquinolones are among the drugs of choice used to treat MRSA infections. This study aims to identify different mechanisms of fluoroquinolne resistance in local MRSA random sampling isolates in Cairo, Egypt. METHODOLOGY: A total of 94 clinical isolates of S. aureus were collected from two major University hospitals in Cairo. Identification was confirmed by appropriate morphological, cultural, and biochemical tests. The antibiotic susceptibility pattern was determined for all isolates. The possible involvement of efflux pumps in mediating fluoroquinolone resistance as well as changes in the quinolone resistance determining region (QRDR) of gyrA and gyrB genes were investigated RESULTS: A total of 45 isolates were found to be MRSA, among which 26 isolates were found to be fluoroquinolone-resistant. The MIC values of the tested fluoroquinolones in the presence of the efflux pump inhibitors omeprazole and piperine were reduced. Measuring the uptake of ciprofloxacin upon the addition of the efflux pump inhibitor omeprazole, an increased level of accumulation was observed. Non-synonymous and silent mutations were detected in the QRDR of gyrA and gyrB genes. CONCLUSIONS: These results shed light on some of the resistance patterns of MRSA strains isolated from local health care settings in Cairo, Egypt. The resistance of these MRSA towards fluoroquinolones does not depend only on mutation in target genes; other mechanisms of resistance such as the permeability effect, efflux pumps and decreased availability of quinolones at the target site can also be involved.