Detection of Bacterial 16S rRNA and Identification of Four Clinically Important Bacteria by Real-Time PCR

Within the paradigm of clinical infectious disease research, Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa represent the four most clinically relevant, and hence most extensively studied bacteria. Current culture-based methods for identifying these organisms are slow and cumbersome, and there is increasing need for more rapid and accurate molecular detection methods. Using bioinformatic tools, 962,279 bacterial 16S rRNA gene sequences were aligned, and regions of homology were selected to generate a set of real-time PCR primers that target 93.6% of all bacterial 16S rRNA sequences published to date. A set of four species-specific real-time PCR primer pairs were also designed, capable of detecting less than 100 genome copies of A. baumannii, E. coli, K. pneumoniae, and P. aeruginosa. All primers were tested for specificity in vitro against 50 species of Gram-positive and –negative bacteria. Additionally, the species-specific primers were tested against a panel of 200 clinical isolates of each species, randomly selected from a large repository of clinical isolates from diverse areas and sources. A comparison of culture and real-time PCR demonstrated 100% concordance. The primers were incorporated into a rapid assay capable of positive identification from plate or broth cultures in less than 90 minutes. Furthermore, our data demonstrate that current targets, such as the uidA gene in E.coli, are not suitable as species-specific genes due to sequence variation. The assay described herein is rapid, cost-effective and accurate, and can be easily incorporated into any research laboratory capable of real-time PCR.     

Bacterial-resistance among outpatients of county hospitals in China: significant geographic distinctions and minor differences between central cities

The purpose of this study was to survey antibacterial resistance in outpatients of Chinese county hospitals. A total of 31 county hospitals were selected and samples continuously collected from August 2010 to August 2011. Drug sensitivity testing was conducted in a central laboratory. A total of 2946 unique isolates were collected, including 634 strains of Escherichia coli, 606 Klebsiella pneumoniae, 476 Staphylococcus aureus, 308 Streptococcus pneumoniae, and 160 Haemophilus influenzae. Extended-spectrum β-lactamases were detected in E. coli (42.3% strains), K. pneumoniae (31.7%), and Proteus mirabilis (39.0%). Ciprofloxacin-resistance was detected in 51.0% of E. coli strains. Salmonella spp. and Shigella spp. were sensitive to most antibacterial agents. Less than 8.0% of Pseudomonas aeruginosa isolates were resistant to carbapenem. For S. aureus strains, 15.3% were resistant to methicillin, and some strains of S. pneumoniae showed resistance to penicillin (1.6%), ceftriaxone (13.0%), and erythromycin (96.4%). β-lactamase was produced by 96.5% of Moraxella catarrhalis strains, and 36.2% of H. influenzae isolates were resistant to ampicillin. Azithromycin-resistant H. influenzae, imipenem-resistant but meropenem-sensitive Proteus, and ceftriaxone- and carbapenem non-sensitive M. catarrhalis were recorded. In conclusion, cephalosporin- and quinolone-resistant strains of E. coli and Klebsiella pneumonia and macrolide-resistant Gram-positive cocci were relatively prominent in county hospitals. The antibacterial resistance profiles of isolates from different geographical locations varied significantly, with proportions in county hospitals lower than those in their tertiary counterparts in the central cities, although the difference is diminishing.     

In vitro trials of some antimicrobial combinations against Staphylococcus aureus and Pseudomonas aeruginosa

Staphylococcus aureus and Pseudomonas aeruginosa are rapidly increasing as multidrug resistant strains worldwide. In nosocomial settings because of heavy exposure of different antimicrobials, resistance in these pathogens turned into a grave issue in both developed and developing countries. The aim of this study was to investigate in vitro antibiotic synergism of combinations of β-lactam–β-lactam and β-lactam–aminoglycoside against clinical isolates of S. aureus and P. aeruginosa. Synergy was determined by checkerboard double dilution method. The combination of amoxicillin and cefadroxil was found to be synergistic against 47 S. aureus isolates, in the FICI range of 0.14–0.50 (81.03%) followed by the combination of streptomycin and cefadroxil synergistic against 44 S. aureus isolates in the FICI range of 0.03–0.50 (75.86%). The combination of streptomycin and cefadroxil was observed to be synergistic against 39 P. aeruginosa isolates in the FICI range of 0.16–0.50 (81.28%). Further actions are needed to characterize the possible interaction mechanism between these antibiotics. Moreover, the combination of streptomycin and cefadroxil may lead to the development of a new and vital antimicrobial against simultaneous infections of S. aureus and P. aeruginosa.     

A Three-Year Survey of the Antibacterial Spectra of the More Commonly Used Chemotherapeutic Agents

Eight major bacterial groups (25,000 strains) of gram-positive and gram-negative organisms which were isolated from a variety of clinical specimens were tested by the disc-plate and tube dilution procedure. The in vitro antibacterial spectra of 17 commonly used chemotherapeutic agents were recorded and evaluated statistically during a three-year period. Penicillin G, erythromycin and chloramphenicol were very effective against members of the diplococci and streptococci genera. The synthetic penicillins inhibited 99% of Staph. aureus whereas penicillin G was effective against only 45% of these strains. There was a significant increase in the number of tetracycline-resistant strains of both D. pneumoniae and the Lancefield Group A streptococci. A yearly increase in gram-negative pathogens was noted. These organisms (i.e. Escherichia, Aerobacter, Proteus, Pseudomonas) showed greater resistance to the majority of chemotherapeutic agents than did the gram-positive organisms. The percentage of susceptible strains for each bacterial group appears in the text.     

24-Branched Δ5 sterols from Laurencia papillosa red seaweed with antibacterial activity against human pathogenic bacteria

Methanol extract of thirty-eight seaweeds samples were first screened against Gram-positive (Staphylococcus aureus ATCC 25923 and Bacillus subtilis ATCC 6051) and -negative (Escherichia coli ATCC 8739 and Pseudomonas aerugenosa ATCC 9027) bacteria. Laurencia papillosa (Ceramiales, Rhodomelaceae, Rhodophyta) gave maximum antimicrobial activity against these bacteria. It was finally tested against four clinical Gram-negative isolates (E. coli, P. aerugenosa, Klebsiella pneumoniae and Shigella flexineri) and exhibited antibacterial activity. The extract was fractionated by column chromatography and the active fraction was identified as a cholesterol derivative, 24-propylidene cholest-5-en-3β-ol using gas chromatography mass spectrometry (GC–MS). The electrospray ionization mass spectrometry (ESI-MS) and FT-IR spectroscopic analysis also supported the structure of the compound. The minimum inhibitory concentration ranged from 1.2 to 1.7 μg/mL (IC₅₀) against clinical isolates. This is the first report of antibacterial activity of this cholesterol derivative. This compound could be exploited as potential lead molecule against broad spectrum drug development. The results also affirm the potential of seaweeds as an important natural source of antimicrobial compounds for pharmaceutical industries.     

Biological activity of Cymbopogon schoenanthus essential oil

IntroductionA number of plant species, including Cymbopogon schoenanthus, are traditionally used for the treatment of various diseases. C. schoenanthus is currently, traded in the Saudi markets, and thought to have medicinal value. This study aimed at investigating the biological activities of C. schoenanthus against both Gram-positive and Gram-negative bacteria and to identify its chemical ingredients.Materials and methodsThe inhibitory effects of water extracts of C. schoenanthus essential oils were evaluated against ten isolates of both Gram-positive and Gram-negative bacteria using the agar well diffusion and dilution methods. The minimum inhibitory concentration (MIC) was assayed using the Broth microdilution test on five of the ten isolates. The death rates were determined by the time kill assay, done according to the Clinical Laboratory Standards Institute (CLSI) guidelines. The chemical composition of the essential oils of the plant was performed using GC/MS.ResultsThe C. schoenanthus essential oil was effective against Escherichia coli, Staphylococcus aureus, methicillin-sensitive (MSSA) S. aureus (MRSA) and Klebsiella pneumoniae. The essential oil was not effective against Staphylococcus saprophyticus at the highest concentration applied of >150 μg/ml. The MIC values were as follows: 9.37 μg/ml for E. coli 4.69 μg/ml for S. aureus (MRSA), 2.34 mg/ml for MSSA and 2.34 μg/ml for K. pneumoniae. The time-kill assay indicated that there was a sharp time dependent decline in K. pneumoniae counts in the presence of the oil. This is in contrast to a gradual decline in the case of S. aureus under the same conditions. The eight major components of the essential oil were: piperitone (14.6%), cyclohexanemethanol (11.6%), β-elemene (11.6%), α-eudesmol (11.5%), elemol (10.8%), β-eudesmol (8.5%), 2-naphthalenemethanol (7.1%) and γ-eudesmol (4.2%).ConclusionThe results of the present study provide a scientific validation for the traditional use of C. schoenanthus as an antibacterial agent. Future work is needed to investigate and explore its application in the environmental and medical fields. In addition, to evaluating the efficacy of the individual ingredients separately to better understand the underlying mechanism.     

Design,synthesis and molecular modeling studies of new series of s-triazine derivatives as antimicrobial agents against multi-drug resistant clinical isolates

Three novel series of s-triazine derivatives, including thirty-five new compounds 2a-d, 3a-3p, 4b-d, 5b-d, 6d-6d, and 7a-7f were synthesized comprising a diversity of substituents based on the structure of Astrazeneca arylaminotriazine DNA gyrase B inhibitor. The antimicrobial activity was determined for all compounds against Staphylococcus aureus, Escherichia coli and Candida albicans using the two-fold serial dilution technique and against reference standards Ampicillin for the antibacterial screening and Clotrimazole regarding the antifungal evaluation. The tested compounds showed strong to moderate antibacterial inhibitory action and weak antifungal activity. Compounds 3j and 6b were the most potent antibacterial agents against the tested strains and multi-drug resistant (MDR) clinical isolates of Klebsiella pneumoniae and methicillin resistant Staphylococcus aureus (MRSA1) with minimal toxicity in comparison to the reference drugs. In silico molecular properties calculations and molecular docking study for 3j and 6b revealed that both compounds could be considered as promising antibacterial DNA gyrase B inhibitors.     

Isolation of antimicrobial producing Actinobacteria from soil samples

Emergence of multidrug resistant bacteria has made the search for novel bioactive compounds from natural and unexplored habitats a necessity. Actinobacteria have important bioactive substances. The present study investigated antimicrobial activity of Actinobacteria isolated from soil samples of Egypt. One hundred samples were collected from agricultural farming soil of different governorates. Twelve isolates have produced activity against the tested microorganisms (S. aureus, Bacillus cereus, E. coli, K. pneumoniae, P. aeruginosa, S. Typhi, C. albicans, A. niger and A. flavus). By VITEK 2 system version: 07.01 the 12 isolates were identified as Kocuria kristinae, Kocuria rosea, Streptomyces griseus, Streptomyces flaveolus and Actinobacteria. Using ethyl acetate extraction method the isolates culture’s supernatants were tested by diffusion method against indicator microorganisms. These results indicate that Actinobacteria isolated from Egypt farms could be sources of antimicrobial bioactive substances.     

Antimicrobial Activity of Novel Synthetic Peptides Derived from Indolicidin and Ranalexin against Streptococcus pneumoniae

Antimicrobial peptides (AMPs) represent promising alternatives to conventional antibiotics in order to defeat multidrug-resistant bacteria such as Streptococcus pneumoniae. In this study, thirteen antimicrobial peptides were designed based on two natural peptides indolicidin and ranalexin. Our results revealed that four hybrid peptides RN7-IN10, RN7-IN9, RN7-IN8, and RN7-IN6 possess potent antibacterial activity against 30 pneumococcal clinical isolates (MIC 7.81-15.62µg/ml). These four hybrid peptides also showed broad spectrum antibacterial activity (7.81µg/ml) against S. aureus, methicillin resistant S. aureus (MRSA), and E. coli. Furthermore, the time killing assay results showed that the hybrid peptides were able to eliminate S. pneumoniae within less than one hour which is faster than the standard drugs erythromycin and ceftriaxone. The cytotoxic effects of peptides were tested against human erythrocytes, WRL-68 normal liver cell line, and NL-20 normal lung cell line. The results revealed that none of the thirteen peptides have cytotoxic or hemolytic effects at their MIC values. The in silico molecular docking study was carried out to investigate the binding properties of peptides with three pneumococcal virulent targets by Autodock Vina. RN7IN6 showed a strong affinity to target proteins; autolysin, pneumolysin, and pneumococcal surface protein A (PspA) based on rigid docking studies. Our results suggest that the hybrid peptides could be suitable candidates for antibacterial drug development.     

Antibacterial activity of soil bacteria isolated from Kochi,India and their molecular identification

The present study, deal about the antibiosis activity of soil bacteria, isolated from 10 different locations of rhizosphere and diverse cultivation at Kochi, Kerala, India. The bacteria were isolated by standard serial dilution plate techniques. Morphological characterization of the isolate was done by Gram’s staining and found that all of them gram positive. Isolated bacteria were tested against 6 human pathogens viz., Escherichia coli, Enterococcus sp., Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus aureus and Acinetobacter sp. Primary screening was carried out by perpendicular streaking and seed overlay method. Based on the result of primary screening most potential isolates of S1A1 and S7A3 were selected for secondary screening. Both the isolates showed positive results against Enterococcus sp. and S.aureus. The maximum antagonistic activity of 20.98 and 27.08?mm zone of inhibition was recorded at S1A1 against Enterococcus sp. and S. aureus respectively, at 180?µl concentration. Molecular identification was carried out by 16S rRNA sequence. The 16S rRNA was amplified from the DNA samples by using PCR. The amplified 16S rRNA PCR products were purified and sequenced. The sequences were subjected to NCBI BLAST. The isolates S1A1 and S7A3 BLAST results showed 99% and 95% respectively, similarity with the available database sequence of Bacillus amyloliquefaciens. The sequences were deposited in GenBank and the accession numbers KY864390 (S1A1) and KY880975 (S7A3) were obtained.     

Rational Design of Berberine-Based FtsZ Inhibitors with Broad-Spectrum Antibacterial Activity

Inhibition of the functional activity of Filamenting temperature-sensitive mutant Z (FtsZ) protein, an essential and highly conserved bacterial cytokinesis protein, is a promising approach for the development of a new class of antibacterial agents. Berberine, a benzylisoquinoline alkaloid widely used in traditional Chinese and native American medicines for its antimicrobial properties, has been recently reported to inhibit FtsZ. Using a combination of in silico structure-based design and in vitro biological assays, 9-phenoxyalkyl berberine derivatives were identified as potent FtsZ inhibitors. Compared to the parent compound berberine, the derivatives showed a significant enhancement of antibacterial activity against clinically relevant bacteria, and an improved potency against the GTPase activity and polymerization of FtsZ. The most potent compound 2 strongly inhibited the proliferation of Gram-positive bacteria, including methicillin-resistant S. aureus and vancomycin-resistant E. faecium, with MIC values between 2 and 4 µg/mL, and was active against the Gram-negative E. coli and K. pneumoniae, with MIC values of 32 and 64 µg/mL respectively. The compound perturbed the formation of cytokinetic Z-ring in E. coli. Also, the compound interfered with in vitro polymerization of S. aureus FtsZ. Taken together, the chemical modification of berberine with 9-phenoxyalkyl substituent groups greatly improved the antibacterial activity via targeting FtsZ.     

Bacterial Spectrum and Antimicrobial Susceptibility Pattern of Bloodstream Infections in Children with Febrile Neutropenia: Experience of Single Center in Southeast of Turkey

Empirical antimicrobial therapy is usually started in febrile neutropenic patients without having culture results. The aim of this study was to help determine the policies of empirical antibiotic usage in febrile neutropenic children by detecting the antimicrobial susceptibility profile in this group of patients. In this study 811 blood cultures taken from neutropenic children hospitalized at the Department of Oncology of Gaziantep Children Hospital November 2007 and February 2010 were retrospectively evaluated. Blood cultures were routinely collected in aerobic and anaerobic media and incubated using the BACTEC system. Identification and antimicrobial susceptibility testing of the isolates to antimicrobial agents was performed using the Vitek2^® system according to the recommendations of the Clinical and Laboratory Standards Institute. Of 811 isolates analyzed, 128 (56.4%) were gram positive cocci, 43 (18.9%) were gram negative bacilli and fungi accounted for 56 (24.7%). The main isolated Gram-positive bacteria from blood were coagulase-negative staphylococcus (56.7%), followed by methicillin-resistant Staphylococcus aureus (14.1%). S. aureus and Streptococcus spp. were all susceptible to linezolid, vancomycin and teicoplanin. S aureus was still susceptible to few other antimicrobial agents such as tetracycline (82.4%), chloramphenicol (55.6%). Seven E. faecium, 7 E. fecalis and 1 E. hirae was isolated from blood cultures. Vancomycin resistance was detected in 6 out of 15 (40%) Enterococcus spp. isolates. Among gram-negative bacteria E. coli (30.2%) was followed by Klebsiella pneumoniae (20.9%) and Proteus spp. (18.6%). Imipenem (89.2%), meropenem (86.6%), chloramphenicol (88.9%), amicasin (82.4%) and fosfomycin (81.3%) showed highest susceptibility in vitro activity against all Gram-negative isolates. To know the antimicrobial susceptibility profile of the pathogens frequently isolated from febrile neutropenic children and to consider this profile before starting an empirical antibiotic therapy would help the clinics which have any role in the treatment of these patients to determine the empirical antibiotic usage policies.     

Toward Repurposing Ciclopirox as an Antibiotic against Drug-Resistant Acinetobacter baumannii,Escherichia coli,and Klebsiella pneumoniae

Antibiotic-resistant infections caused by gram-negative bacteria are a major healthcare concern. Repurposing drugs circumvents the time and money limitations associated with developing new antimicrobial agents needed to combat these antibiotic-resistant infections. Here we identified the off-patent antifungal agent, ciclopirox, as a candidate to repurpose for antibiotic use. To test the efficacy of ciclopirox against antibiotic-resistant pathogens, we used a curated collection of Acinetobacter baumannii, Escherichia coli, and Klebsiella pneumoniae clinical isolates that are representative of known antibiotic resistance phenotypes. We found that ciclopirox, at 5–15 µg/ml concentrations, inhibited bacterial growth regardless of the antibiotic resistance status. At these same concentrations, ciclopirox reduced growth of Pseudomonas aeruginosa clinical isolates, but some of these pathogens required higher ciclopirox concentrations to completely block growth. To determine how ciclopirox inhibits bacterial growth, we performed an overexpression screen in E. coli. This screen revealed that galE, which encodes UDP-glucose 4-epimerase, rescued bacterial growth at otherwise restrictive ciclopirox concentrations. We found that ciclopirox does not inhibit epimerization of UDP-galactose by purified E. coli GalE; however, ΔgalU, ΔgalE, ΔrfaI, or ΔrfaB mutant strains all have lower ciclopirox minimum inhibitory concentrations than the parent strain. The galU, galE, rfaI, and rfaB genes all encode enzymes that use UDP-galactose or UDP-glucose for galactose metabolism and lipopolysaccharide (LPS) biosynthesis. Indeed, we found that ciclopirox altered LPS composition of an E. coli clinical isolate. Taken together, our data demonstrate that ciclopirox affects galactose metabolism and LPS biosynthesis, two pathways important for bacterial growth and virulence. The lack of any reported fungal resistance to ciclopirox in over twenty years of use in the clinic, its excellent safety profiles, novel target(s), and efficacy, make ciclopirox a promising potential antimicrobial agent to use against multidrug-resistant problematic gram-negative pathogens.     

Differences in Toll-like receptor expression and cytokine production after stimulation with heat-killed gram-positive and gram-negative bacteria

Innate immune surveillance in the blood is executed mostly by circulating monocytes, which recognize conserved bacterial molecules such as peptidoglycan and lipopolysaccharide. Toll-like receptors (TLR) play a central role in microbe-associated molecular pattern detection. The aim of this study was to compare the differences in TLR expression and cytokine production after stimulation of peripheral blood cells with heat-killed gram-negative and gram-positive human pathogens: Neisseria meningitidis, Escherichia coli, Staphylococcus aureus, and Streptococcus pneumoniae. We found that TLR2 expression is up-regulated on monocytes after stimulation with S. aureus, S. pneumoniae, E. coli, and N. meningitidis. Moreover, TLR2 up-regulation was positively associated with increasing concentrations of gram-positive bacteria, whereas higher concentrations of gram-negative bacteria, especially E. coli, caused a milder TLR2 expression increase when compared to low doses. Cytokines were produced in similar dose-dependent profiles regardless of the stimulatory pathogen; however, gram-negative pathogens induced higher cytokine levels when compared to gram-positive bacteria at the same density. These results indicate that gram-positive and gram-negative bacteria differ in their dose-dependent patterns of induction of TLR2 and TLR4, but not cytokine expression.     

Anthelmintic and antimicrobial activity of Indigofera oblongifolia leaf extracts

Due to the endless emergence of drug resistant pathogens, there is a constant need for new therapeutic agents for clinical use. The identification of active components in natural products and determining the efficacy of these active components has become the current focus of pharmacological research. The present study aimed to evaluate the anthelmintic and antimicrobial activities of Indigofera oblongifolia leaf extract (ILE) against the earthworm Allolobophora caliginosa, the gram-positive bacteria (Bacillus cereus, Streptococcus pneumoniae, and Staphylococcus aureus), the gram-negative bacteria (Klebsiella pneumoniae, Pseudomonas aeruginosa and Escherichia coli) and the yeast Candida albicans. Methanolic extract of I. oblongifolia leaf was obtained and the total phenolics and flavonoids in ILE were determined. The anthelmintic study was carried out to determine the time to paralysis and time to death of worms using three doses (100, 200, and 300 mg/mL) of ILE. Also, Kirby-Bauer disk diffusion susceptibility method was used to determine the antimicrobial activity of ILE. The results showed that ILE induces paralysis and death of A. caliginosa at all concentration tested faster than the reference drug, Albendazole. Additionally, ILE exhibited prominent antimicrobial activity against all gram-positive bacteria tested but almost no significant activity against the gram-negative bacteria, except K. pneumoniae. ILE showed close similarity to the spectrum of chloramphenicol and cefoxitin activities. Furthermore, C. albicans was highly susceptible to the leaf extracts. Our results showed that ILE is an effective anthelmintic and antimicrobial agent.     

In Vitro Studies of a New Semisynthetic Penicillin, 6-(D-α-Sulfoaminophenylacetamido)-Penicillanic Acid

The activity of 6-(D-α-sulfoaminophenylacetamido)-penicillanic acid was determined against 357 clinical isolates of gram-negative bacilli by use of the tube-dilution technique. The majority of the isolates of Pseudomonas species were inhibited by 200 μg/ml or less of this antibiotic. Most of the isolates of Escherichia coli had a minimal inhibitory concentration of 50 μg/ml or less. Seventy-three per cent of the isolates of P. mirabilis, 40% of the isolates of P. morganii, and 45% of the isolates of Enterobacter species were inhibited by 12.5 μg/ml or less, whereas most of the isolates of Klebsiella species and Serratia species were resistant. The activity of this semisynthetic penicillin was affected by the size of the inoculum. The drug was bactericidal against all isolates of E. coli and Proteus species that were sensitive to it, but it was bactericidal against only 32% of the sensitive isolates of Pseudomonas species.     

Repurposing Salicylanilide Anthelmintic Drugs to Combat Drug Resistant Staphylococcus aureus

Staphylococcus aureus is a Gram-positive bacterium that has become the leading cause of hospital acquired infections in the US. Repurposing Food and Drug Administration (FDA) approved drugs for antimicrobial therapy involves lower risks and costs compared to de novo development of novel antimicrobial agents. In this study, we examined the antimicrobial properties of two commercially available anthelmintic drugs. The FDA approved drug niclosamide and the veterinary drug oxyclozanide displayed strong in vivo and in vitro activity against methicillin resistant S. aureus (minimum inhibitory concentration (MIC): 0.125 and 0.5 μg/ml respectively; minimum effective concentration: ≤ 0.78 μg/ml for both drugs). The two drugs were also effective against another Gram-positive bacteria Enterococcus faecium (MIC 0.25 and 2 μg/ml respectively), but not against the Gram-negative species Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter aerogenes. The in vitro antimicrobial activity of niclosamide and oxyclozanide were determined against methicillin, vancomycin, linezolid or daptomycin resistant S. aureus clinical isolates, with MICs at 0.0625-0.5 and 0.125-2 μg/ml for niclosamide and oxyclozanide respectively. A time-kill study demonstrated that niclosamide is bacteriostatic, whereas oxyclozanide is bactericidal. Interestingly, oxyclozanide permeabilized the bacterial membrane but neither of the anthelmintic drugs exhibited demonstrable toxicity to sheep erythrocytes. Oxyclozanide was non-toxic to HepG2 human liver carcinoma cells within the range of its in vitro MICs but niclosamide displayed toxicity even at low concentrations. These data show that the salicylanilide anthelmintic drugs niclosamide and oxyclozanide are suitable candidates for mechanism of action studies and further clinical evaluation for treatment of staphylococcal infections.     

Diversity of antagonistic bacteria isolated from medicinal plant Peganum harmala L.

The antimicrobial activity of plant extract of Peganum harmala, a medicinal plant has been studied already. However, knowledge about bacterial diversity associated with different parts of host plant antagonistic to different human pathogenic bacteria is limited. In this study, bacteria were isolated from root, leaf and fruit of plant. Among 188 bacterial isolates isolated from different parts of the plant only 24 were found to be active against different pathogenic bacteria i.e. Escherichia coli, Methicillin-resistant Staphylococcus aureus (MRSA), Enterococcus faecium, Enterococcus faecalis and Pseudomonas aeruginosa. These active bacterial isolates were identified on the basis of 16S rRNA gene analysis. Total population of bacteria isolated from plant was high in root, following leaf and fruit. Antagonistic bacteria were also more abundant in root as compared to leaf and fruit. Two isolates (EA5 and EA18) exhibited antagonistic activity against most of the targeted pathogenic bacteria mentioned above. Some isolates showed strong inhibition for one targeted pathogenic bacterium while weak or no inhibition for others. Most of the antagonistic isolates were active against MRSA, following E. faecium, P. aeruginosa, E. coli and E. faecalis. Taken together, our results show that medicinal plants are good source of antagonistic bacteria having inhibitory effect against clinical bacterial pathogens.     

Characterization of rhizospheric soil streptomycetes from Moroccan habitats and their antimicrobial activities

During an investigation on actinomycetes from rhizospheric soils from Moroccan habitats, 131 streptomycetes were recovered, morphologically characterized and assessed for their antimicrobial activity. Eleven isolates were characterized by the absence of an aerial mycelium. According to the colour of aerial mycelium, the rest were grouped into seven main classes, namely, grey, yellow, cream, white, green, red and polymorphic colours (pink, orange or violet). The grey colour class dominated (40%) and the red one was found only in rhizospheric soil of the Moroccan endemic plant Argania spinosa. About one third of the isolates (34%) produced soluble pigments of various colours and 14% produced melanoid pigments. Most of the isolates (83%) were active against one or more of the organisms tested (one gram-negative bacterium, three gram-positive bacteria, three yeasts and two filamentous fungi). Most antibiotic-producing isolates possess red and white colour. Strong antibiosis was exhibited against Streptomyces scabies, Staphylococcus aureus and Bacillus subtilis (75, 68 and 60% respectively), while only 14 and 8% of isolates displayed an activity against Escherichia coli and Verticillium dahliae respectively.     

Synthesis and comparative study on the antimicrobial activity of hybrid materials based on silver nanoparticles (AgNps) stabilized by polyvinylpyrrolidone (PVP)

Hybrid materials based on polyvinylpyrrolidone (PVP) with silver nanoparticles (AgNps) were synthesized applying two different strategies based on thermal or chemical reduction of silver ions to silver nanoparticles using PVP as a stabilizer. The formation of spherical silver nanoparticles with diameter ranging from 9 to 16 nm was confirmed by TEM analysis. UV-vis and FTIR spectroscopy were also applied to confirm the successful formation of AgNps. The antibacterial activity of the synthesized AgNPs/PVP against etalon strains of three different groups of bacteria—Staphylococcus aureus (S. aureus; gram-positive bacteria), Escherichia coli (E. coli; gram-negative bacteria), Pseudomonas aeruginosa (P. aeruginosa; non-ferment gram-negative bacteria), as well as against spores of Bacillus subtilis (B. subtilis) was studied. AgNps/PVP were tested for the presence of fungicidal activity against different yeasts and mold such as Candida albicans, Candida krusei, Candida tropicalis, Candida glabrata, and Aspergillus brasiliensis. The hybrid materials showed a strong antimicrobial effect against the tested bacterial and fungal strains and therefore have potential applications in biotechnology and biomedical science.