Chemical characterization and physical and biological activities of rhamnolipids produced by Pseudomonas aeruginosa BN10

Pseudomonas aeruginosa BN10 isolated from hydrocarbon-polluted soil was found to produce rhamnolipids when cultivated on 2% glycerol, glucose, n-hexadecane, and n-alkanes. The rhamnolipids were partially purified on silica gel columns and their chemical structures elucidated by combination of one- and two-dimensional 1H and 13C NMR techniques and ESI-MS analysis. Eight structural rhamnolipid homologues were identified: Rha-C10-C8, Rha-C10-C10, Rha-C10-C12:1, Rha-C10-C12, Rha2-C10-C8, Rha2-C10-C10, Rha2-C10-C12:1, and Rha2-C10-C12. The chemical composition of the rhamnolipid mixtures produced on different carbon sources did not vary with the type of carbon source used. The rhamnolipid mixture produced by Pseudomonas aeruginosa BN10 on glycerol reduced the surface tension of pure water from 72 to 29 mN m(-1) at a critical micellar concentration of 40 mg 1(-1), and the interfacial tension was 0.9 mN m(-1). The new surfactant product formed stable emulsions with hydrocarbons and showed high antimicrobial activity against Gram-positive bacteria. The present study shows that the new strain Pseudomonas aeruginosa BN10 demonstrates enhanced production of the di-rhamnolipid Rha2-C10-C10 on all carbon sources used. Due to its excellent surface and good antimicrobial activities the rhamnolipid homologue mixture from Pseudomonas aeruginosa BN10 can be exploited for use in bioremediation, petroleum and pharmaceutical industries.     

发酵碳源对铜绿假单胞菌NY3所产鼠李糖脂结构及性能的影响

为研究发酵碳源对铜绿假单胞菌NY3所产鼠李糖脂结构及性能的影响,从鼠李糖脂的结构组分、性能和应用效果等方面展开研究。薄层实验证明两种鼠李糖脂均含有单糖脂和双糖脂。液质分析发现以橄榄油作碳源时,鼠李糖脂中双糖脂(Rha-Rha-C5-C6:1和Rha-Rha-C8-C8:2)比例更大,约为73.09%。而地沟油作碳源时,单糖脂(Rha-C10-C10和Rha-C16-C16:2)的比例更高,约为76.91%。橄榄油和地沟油为碳源的鼠李糖脂的临界胶束浓度(CMC)分别为55 mg/L和80mg/L。相同投加量时,前者乳化性和乳化稳定性均优于后者。NY3菌降解含油污泥时,投加双糖脂含量高的鼠李糖脂会使C16-C30直链烷烃的去除率更高。     

Chemical structures and biological activities of rhamnolipids produced by Pseudomonas aeruginosa B189 isolated from milk factory waste

The aim of this work was to study chemical structures and biological activities of rhamnolipids produced by Pseudomonas aeruginosa B189 isolated from milk factory waste. The culture produced two biosurfactants, a and b, which showed strong activity and were identified as L-rhamnopyranosyl-L-rhamnopyranosyl-beta-hydroxydecanoyl-beta-hydroxydecanoate or Rha-Rha-C10-C10 and L-rhamnopyranosyl-L-rhamnopyranosyl-beta-hydroxydecanoyl-beta-hydroxydodecanoate or Rha-Rha-C10-C12, respectively. Both compounds exhibited higher surfactant activities tested by the drop collapse test than several artificial surfactants such as SDS and Tween 80. Rhamnolipid a showed significant antiproliferative activity against human breast cancer cell line (MCF-7) at minimum inhibitory concentration (MIC) at 6.25 microg/mL while rhamnolipid b showed MIC against insect cell line C6/36 at 50 microg/mL.     

Molecular and structural characterization of the biosurfactant produced by Pseudomonas aeruginosa DAUPE 614

Pseudomonas aeruginosa DAUPE 614 produced rhamnolipids (3.9gL(-1)) when cultivated on a medium containing glycerol and ammonium nitrate. These rhamnolipids reduced the surface tension of water to 27.3mNm(-1), with a critical micelle concentration of 13.9mgL(-1). The maximum emulsification index against toluene was 86.4%. The structure of the carbohydrate moiety of the glycolipid was determined by gas chromatography-mass spectroscopy (GC-MS) analysis allied to electrospray ionization mass spectrometry and nuclear magnetic resonance (NMR) 1D, 2D (13)C, (1)H spectroscopy. The hydroxyl fatty acids were analyzed by GC-MS as hydroxy-acetylated fatty acid methyl ester derivatives. The positions of the fatty acids in the lipid moiety were variable, with 6 mono-rhamnolipid homologues (Rha-C(10)-C(10); Rha-C(10)-C(8); Rha-C(8)-C(10); Rha-C(10)-C(12:1); Rha-C(12)-C(10); Rha-C(10)-C(12)) and 6 di-rhamnolipid homologues (Rha(2)-C(10)-C(10); Rha(2)-C(10)-C(8); Rha(2)-C(8)-C(10); Rha(2)-C(10)-C(12:1); Rha(2)-C(12)-C(10); Rha(2)-C(10)-C(12)). The ratio of Rha(2)-C(10)-C(10) to Rha-C(10)-C(10) was higher than has been reported in previous studies. Our methodology allowed us to distinguish between the isomeric pairs Rha-C(10)-C(8)/Rha-C(8)-C(10), Rha-C(10)-C(12)/Rha-C(12)-C(10), Rha(2)-C(10)-C(8)/Rha(2)-C(8)-C(10) and Rha(2)-C(12)-C(10)/Rha(2)-C(10)-C(12). For each isomeric pair, the congener with the shorter chain adjacent to the sugar was always more abundant than the congener with longer chain.     

Structural characterization of rhamnolipid produced by Pseudonomas aeruginosa strain FIN2 isolated from oil reservoir water

Biosurfactant-producing microorganisms inhabiting oil reservoirs are of great potential in industrial applications. Yet, till now, the knowledge about the structure and physicochemical property of their metabolites are still limited. The aim of this study was to purify and structurally characterize the biosurfactant from Pseudomonas aeruginosa strain FIN2, a newly isolated strain from an oil reservoir. The purification was conducted by silica gel column chromatography followed by pre-RP HPLC and the structural characterization was carried out by GC–MS combined with MS/MS. The results show that the biosurfactant produced by FIN2 is rhamnolipid in nature and its four main fractions were identified to be Rha-C10-C10(46.1 %), Rha–Rha-C10-C10(20.1 %), Rha-C8-C10 (7.5 %) and Rha-C10-C12:1(5.5 %), respectively. Meanwhile, the rarely reported rhamnolipid congeners containing β-hydroxy fatty acids of C6, C9, C10:1 and C11 were also proved to be present in the rhamnolipid mixture produced. The rhamnolipid mixture exhibited a strong surface activity by lowering the surface tension of distilled water to 28.6 mN/m with a CMC value of 195 mg/l.     

Chemical structure, surface properties and biological activities of the biosurfactant produced by Pseudomonas aeruginosa LBI from soapstock

Pseudomonas aeruginosa LBI isolated from petroleum-contaminated soil produced rhamnolipids (RL(LBI)) when cultivated on soapstock as the sole carbon source. HPLC-MS analysis of the purified culture supernatant identified 6 RL homologues (%): R(2) C(10) C(10) 28.9; R(2) C(10) C(12:1) 23.0; R(1) C(10) C(10) 23.4; R(2) C(10) C(12) 11.3; R(2) C(10) C(12) 7.9; R(2) C(10) C(12) 5.5. To assess the potential antimicrobial activity of the new rhamnolipid product, RL(LBI), its physicochemical properties were studied. RL(LBI) had a surface tension of 24 mN m(-1) and an interfacial tension of 1.31 mN m(-1); the cmc was 120 mg l(-1). RL(LBI) produced stable emulsions with hydrocarbons and vegetable oils. This product showed good antimicrobial behaviour against bacteria: MIC for Bacillus subtilis, Staphylococcus aureus and Proteus vulgaris was 8 mg l(-1), for Streptococcus faecalis 4 mg l(-1), and for Pseudomonas aeruginosa 32 mg l(-1). RL(LBI) was active against phytopathogenic fungal species, MIC values of 32 mg l(-1) being found against Penicillium, Alternaria, Gliocadium virens and Chaetonium globosum. Due to its physicochemical properties and antimicrobial behaviour, RL(LBI) could be used in bioremediation treatment and in the food, cosmetic and pharmaceutical industries.     

Chemical structures and biological activities of rhamnolipids produced by Pseudomonas aeruginosa B189 isolated from milk factory waste

The aim of this work was to study chemical structures and biological activities of rhamnolipids produced by Pseudomonas aeruginosa B189 isolated from milk factory waste. The culture produced two biosurfactants, a and b, which showed strong activity and were identified as L-rhamnopyranosyl-L-rhamnopyranosyl-beta-hydroxydecanoyl-beta-hydroxydecanoate or Rha-Rha C10-C10 and L-rhamnopyranosyl-L-rhamnopyranosyl-beta-hydroxydecanoyl-beta-hydroxydodecanoate or Rha-Rha C(10)-C(12), respectively. Both compounds exhibited higher surfactant activities tested by the drop collapse test than several artificial surfactants such as SDS and Tween 80. Rhamnolipid a showed significant antiproliferative activity against human breast cancer cell line (MCF-7) at minimum inhibitory concentration (MIC) at 6.25 microg/mL while rhamnolipid b showed MIC against insect cell line C6/36 at 50 microg/mL.     

Rhamnolipid biosurfactant production by strains of Pseudomonas aeruginosa using low-cost raw materials

This study was aimed at the development of economical methods for higher yields of biosurfactant by suggesting the use of low-cost raw materials. Two oil-degrading strains, Pseudomonas aeruginosa GS9-119 and DS10-129, were used to optimize a substrate for maximum rhamnolipid production. Among the two strains, the latter produced maxima of 4.31, 2.98, and 1.77 g/L rhamnolipid biosurfactant using soybean oil, safflower oil, and glycerol, respectively. The yield of biosurfactant steadily increased even after the bacterial cultures reached the stationary phase of growth. Characterization of rhamnolipids using mass spectrometry revealed the presence of dirhamnolipids (Rha-Rha-C(10)-C(10)). Emulsification activity of the rhamnolipid biosurfactant produced by P. aeruginosa DS10-129 was greater than 70% using all the hydrocarbons tested, including xylene, benzene, hexane, crude oil, kerosene, gasoline, and diesel. P. aeruginosa GS9-119 emulsified only hexane and kerosene to that level.     

Screening and production of rhamnolipids by Pseudomonas aeruginosa 47T2 NCIB 40044 from waste frying oils

World production of oils and fats is about 2.5 million tonnes, 75% of which are derived from plants. Most of them are used in the food industry for the manufacture of different products, or directly as salad oil. Great quantities of waste are generated by the oil and fat industries: residual oils, tallow, marine oils, soap stock, frying oils. It is well known that the disposal of wastes is a growing problem and new alternatives for the use of fatty wastes should be studied. Used frying oils, due to their composition, have great potential for microbial growth and transformation. The use of economic substrates such as hydrophobic wastes meets one of the requirements for a competitive process for biosurfactant production. In the Mediterranean countries, the most used vegetable oils are sunflower and olive oil. Here we present a screening process is described for the selection of micro-organism strains with the capacity to grow on these frying oils and accumulate surface-active compounds in the culture media. From the 36 strains screened, nine Pseudomonas strains decreased the surface tension of the medium to 34-36 mN/M; the emulsions with kerosene remained stable for three months. Two Bacillus strains accumulated lipopeptide and decreased the surface tension to 32-34 mN/m. Strain Ps. aeruginosa 47T2 was selected for further studies. The effect of nitrogen and a C/N of 8. 0 gave a final production of rhamnolipid of 2.7 g l-1 as rhamnose, and a production yield of 0.34 g g-1.     

Structural characterization and surface activities of biogenic rhamnolipid surfactants from Pseudomonas aeruginosa isolate MN1 and synergistic effects against methicillin-resistant Staphylococcus aureus

The aim of present work was to study chemical structures and biological activities of rhamnolipid biosurfactants produced by Pseudomonas aeruginosa MN1 isolated from oil-contaminated soil. The results of liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis revealed that total rhamnolipids (RLs) contained 16 rhamnolipid homologues. Di-lipid RLs containing C₁₀-C₁₀ moieties were by far the most predominant congeners among mono-rhamnose (53.29?%) and di-rhamnose (23.52?%) homologues. Mono-rhamnolipids form 68.35?% of the total congeners in the RLs. Two major fractions were revealed in the thin layer chromatogram of produced RLs which were then purified by column chromatography. The retardation factors (R _f) of the two rhamnolipid purple spots were 0.71 for RL1 and 0.46 for RL2. LC-MS/MS analysis proved that RL1 was composed of mono-RLs and RL2 consisted of di-RLs. RL1 was more surface-active with the critical micelle concentration (CMC) value of 15?mg/L and the surface tension of 25 mN/m at CMC. The results of biological assay showed that RL1 is a more potent antibacterial agent than RL2. All methicillin-resistant Staphylococcus aureus (MRSA) strains were inhibited by RLs that were independent of their antibiotic susceptibility patterns. RLs remarkably enhanced the activity of oxacillin against MRSA strains and lowered the minimum inhibitory concentrations of oxacillin to the range of 3.12?C6.25???g/mL.     

Engineering bacteria for production of rhamnolipid as an agent for enhanced oil recovery

Rhamnolipid as a potent natural biosurfactant has a wide range of potential applications, including enhanced oil recovery (EOR), biodegradation, and bioremediation. Rhamnolipid is composed of rhamnose sugar molecule and beta-hydroxyalkanoic acid. The rhamnosyltransferase 1 complex (RhlAB) is the key enzyme responsible for transferring the rhamnose moiety to the beta-hydroxyalkanoic acid moiety to biosynthesize rhamnolipid. Through transposome-mediated chromosome integration, the RhlAB gene was inserted into the chromosome of the Pseudomonas aeruginosa PAO1-rhlA(-) and Escherichia coli BL21 (DE3), neither of which could produce rhamnolipid. After chromosome integration of the RhlAB gene, the constitute strains P. aeruginosa PEER02 and E. coli TnERAB did produce rhamnolipid. The HPLC/MS spectrum showed that the structure of purified rhamnolipid from P. aeruginosa PEER02 was similar to that from other P. aeruginosa strains, but with different percentage for each of the several congeners. The main congener (near 60%) of purified rhamnolipid from E. coli TnERAB was 3-(3-hydroxydecanoyloxy) decanoate (C(10)-C(10)) with mono-rhamnose. The surfactant performance of rhamnolipid was evaluated by measurement of interfacial tension (IFT) and oil recovery via sand-pack flooding tests. As expected, pH and salt concentration of the rhamnolipid solution significantly affected the IFT properties. With just 250 mg/L rhamnolipid (from P. aeruginosa PEER02 with soybean oil as substrate) in citrate-Na(2)HPO(4), pH 5, 2% NaCl, 42% of oil otherwise trapped was recovered from a sand pack. This result suggests rhamnolipid might be considered for EOR applications.     

Ultrafiltrative separation of rhamnolipid from culture medium

Classic methods of biosurfactant separation are difficult and require large amounts of organic solvents, thus generate high amounts of waste. This work presents and discusses in detail an original procedure to separate rhamnolipid from fermentation broth using high performance membrane techniques. Due to the unique properties of surface active agents, such as capability of forming aggregates above the critical micelle concentration, it is possible to easily purify the biosurfactant with high efficacy using inexpensive and commonly used membranes. In this article, two-stage ultrafiltration is proposed as a method for separating and purifying rhamnolipid from the culture medium. The obtained purified rhamnolipid solution was capable of reducing surface tension of water down to 28.6 mN/m at critical micelle concentration of 40 mg/l. Separation of rhamnolipid was confirmed by HPLC; three types of rhamnolipids were identified (RL1, RL2, RL4), with considerable predominance of RL2.     

Rhamnolipid production with indigenous Pseudomonas aeruginosa EM1 isolated from oil-contaminated site

Rhamnolipid is one of the most effective and commonly used biosurfactant with wide industrial applications. Systematic strategies were applied to improve rhamnolipid (RL) production with a newly isolated indigenous strain Pseudomonas aeruginosa EM1 originating from an oil-contaminated site located in southern Taiwan. Seven carbon substrates and four nitrogen sources were examined for their effects on RL production. In addition, the effect of carbon to nitrogen (C/N) ratio on RL production was also studied. Single-factor experiments show that the most favorable carbon sources for RL production were glucose and glycerol (both at 40 g/L), giving a RL yield of 7.5 and 4.9 g/L, respectively. Meanwhile, sodium nitrate appeared to be the preferable nitrogen source, resulting in a RL production of 8.6g/L. Using NaNO(3) as the nitrogen source, an optimal C/N ratio of 26 and 52 was obtained for glucose- and glycerol-based culture, respectively. To further optimize the composition of fermentation medium, twenty experiments were designed by response surface methodology (RSM) to explore the favorable concentration of three critical components in the medium (i.e., glucose, glycerol, and NaNO(3)). The RSM analysis gave an optimal concentration of 30.5, 18.1, and 4.9 g/L for glucose, glycerol, and NaNO(3), respectively, predicting a maximum RL yield of 12.6 g/L, which is 47% higher than the best yield (8.6 g/L) obtained from preliminary selection tests and single factor experiments (glucose and NaNO(3) as the carbon and nitrogen source). The NMR and mass spectrometry analysis show that the purified RL product contained L-rhamnosyl-beta-hydroxydecanoyl-beta-hydroxydecanoate (RL1) and L-rhamnosyl L-rhamnosyl-beta-hydroxydecanoyl-beta-hydroxydecanoate (RL2). Meanwhile, HPLC analysis indicates that the molar ratio of RL1 and RL2 in the purified rhamnolipid product was ca. 1:1.     

Production Kinetics and Tensioactive Characteristics of Biosurfactant from a Pseudomonas aeruginosa Mutant Grown on Waste Frying Oils

Various waste frying oils (WFOs) were evaluated as substrates for rhamnolipid production by Pseudomonas aeruginosa mutant EBN-8 in the presence or absence of rhamnolipid precursor, under single-/batch-fed conditions. Soybean WFO was the best substrate, producing 9.3 g rhamnolipid l⁻¹ with the specific product yield of 2.7 g g⁻¹ h, under batch-fed cultivation with the addition of rhamnolipid precursor. The surface tension of the cell-free culture broth (CFCB) was 29.1 mN m⁻¹ and the interfacial tension against n-hexadecane was <1 mN m⁻¹. The hydrocarbon/ CFCB systems showed the relative emulsion stability to be in the range of 89.7–92.3.     

Highly effective, water-soluble, hemocompatible 1,3-propylene oxide-based antimicrobials: poly[(3,3-quaternary/PEG)-copolyoxetanes

This study focuses on the solution antimicrobial effectiveness of a novel class of copolyoxetanes with quaternary ammonium and PEG-like side chains. A precursor P[(BBOx-m)(ME2Ox)] copolyoxetane was prepared by cationic ring-opening copolymerization of 3-((4-bromobutoxy)methyl)-3-methyloxetane (BBOx) and 3-((2-(2-methoxyethoxy)ethoxy)methyl)-3-methyloxetane (ME2Ox) to give random copolymers with 14-100 (m) mol % BBOx. Reaction of P[(BBOx-m)(ME2Ox)] with dodecyl dimethylamine gave the corresponding quaternary P[(C12-m)(ME2Ox)] polycation salts, designated C12-m, as viscous liquids in 100% yield. BBOx/ME2Ox and C12/ME2Ox ratios were obtained by (1)H NMR spectroscopy. C12-m molecular weights (M(n), 3.5-21.9 kDa) were obtained from (1)H NMR end group analysis. DSC studies up to 150 °C showed only thermal transitions between -69 and -34 °C assigned to T(g) values. Antibacterial activity for the C12-m copolyoxetanes was tested by determining minimum inhibitory concentrations (MICs) against Gram(+) Staphylococcus aureus and Gram(-) Escherichia coli and Pseudomonas aeruginosa . MIC decreased with increasing C12 mol percent, reaching a minimum in the range C12-43 to C12-60. Overall, the antimicrobial with consistently low MICs for the three tested pathogenic bacteria was C12-43: (bacteria, MIC, μg/mL) E. coli (6), S. aureus (5), and P. aeruginosa (33). For C12-43, minimum biocidal concentration (MBC) to reach 99.99% kill in 24 h required 1.5× MIC for S. aureus and 2× MIC for E. coli and P. aeruginosa . At 5× MIC against a challenge of 10(8) cfu/mL, C12-43 kills ≥99% S. aureus , E. coli , and P. aeruginosa within 1 h. C12-m copolyoxetane cytotoxicity toward human red blood cells was low, indicating good prospects for biocompatibility. The tunability of C12-m copolyoxetane compositions, effective antimicrobial behavior against Gram(+) and Gram(-) bacteria, and promising biocompatibility offer opportunities for further modification and potential applications as therapeutic agents.     

Synthesis, absolute stereochemistry and molecular design of the new antifungal and antibacterial antibiotic produced by Streptomyces sp.201

The absolute stereochemistry of the new antifungal and antibacterial antibiotic produced by Streptomyces sp.201 has been established by achieving the total synthesis of the product. A series of analogues have also been synthesized by changing the side chain and their bioactivity assessed against different microbial strains. Among them, 1e (R = C8H17) was found to be the most potent with MIC of 8 microg/mL against Mycobacterium tuberculosis, 12 microg/mL against Escherichia coli and 16 microg/mL against Bacillus subtilis 6 microg/mL against Proteus vulgaris. This was followed by 1b (R = C5H11) with MIC of 10-20 microg/mL range and 1d (R = C7H15) with MIC of 14-24 g/mL, whereas 1a (R = C4H9) and 1f (R = C18H35) were found to be completely inactive. Besides, 1c (R = C6H13) showed certain extent of antibacterial activity in the range of 24-50 microg/mL. Mycobacterium tuberculosis was very sensitive to 1e (R = C8H17) with MIC of 8 microg/mL. Antifungal activity of analogues 1d (R = C7H15) and 1e, (R = C8H17) against Fusarium oxysporum and Rhizoctonia solani were found promising with MFCs in the 15-18 microg/mL range.     

Optically active antifungal azoles: synthesis and antifungal activity of (2R,3S)-2-(2,4-difluorophenyl)-3-(5-[2-[4-aryl-piperazin-1-yl]-ethyl]-tetrazol-2-yl/1-yl)-1-[1,2,4]-triazol-1-yl-butan-2-ol

A series of (2R,3S)-2-(2,4-difluorophenyl)-3-(5-[2-[4-aryl-piperazin-1-yl]-ethyl]-tetrazol-2-yl)-1-[1,2,4]-triazol-1-yl-butan-2-ol (11a-n) and (2R,3S)-2-(2,4-difluorophenyl)-3-(5-[2-[4-aryl-piperazin-1-yl]-ethyl]-tetrazole-1-yl)-1-[1,2,4]-triazol-1-yl-butan-2-ol (12a-n) has been synthesized. The antifungal activity of compounds was evaluated by in vitro agar diffusion and broth dilution assay. Compounds 11d and its positional isomer 12d having 3-trifluoromethyl substitution on the phenyl ring of piperazine demonstrated significant antifungal activity against variety of fungal cultures (Candida spp. C. neoformans and Aspergillus spp.). The compound 12d showed MIC value of 0.12 microg/mL for C. albicans, C. albicans V-01-191A-261 (resistant strain); 0.25 microg/mL for C. tropicalis, C. parapsilosis ATCC 22019 and C. krusei and MIC value of 0.5 microg/mL for C. glabrata, C. krusei ATCC 6258, which is comparable to itraconazole and better than fluconazole. Further, compound 11d showed significant activity (MIC; 0.25-0.5 microg/mL) against Candida spp. and strong anticryptococcal activity (MIC; 0.25 microg/mL) against C. neoformans.     

Synthesis of variously oxidized abietane diterpenes and their antibacterial activities against MRSA and VRE

Variously oxidized 12 natural abietanes, 6,7-dehydroferruginol methyl ether (3), ferruginol (5), 11-hydroxy-12-oxo-7,9(11),13-abietatriene (7), royleanone (9), demethyl cryptojaponol (12), salvinolone (14), sugiol methyl ether (16), sugiol (17), 5,6-dehydrosugiol methyl ether (19), 5,6-dehydrosugiol (20), 6beta-hydroxyferruginol (23), and taxodione (25) were synthesized. Antimicrobial activities of synthesized phenolic diterpenes and their related compounds against MRSA and VRE were evaluated. Phenols (12-hydroxyabieta-8,11,13-trien-6-one 22 and 23), catechols (12 and 14) and taxodione 25 showed potent activity with 4-10 microg/mL of MIC against MRSA and 4-16 microg/mL of MIC against VRE. (-)-Ferruginol showed more potent activity than natural type (+)-ferruginol. Quinone methide 7 showed the most potent activity with 0.5-1 microg/mL of MIC against both MRSA and VRE.     

Antimicrobial susceptibilities of Bacteroides fragilis and Bacteroides thetaiotaomicron strains isolated from clinical specimens and human intestinal microbiota

Species of Bacteroides fragilis group bacteria are the most prevalent pathogens and have the highest resistance rates to antimicrobial agents among anaerobic bacteria. Infections due to these micro-organisms often originate from patient's own intestinal microbiota. The objective of the study was to determine and compare the susceptibility profiles of clinical and intestinal B. fragilis and B. thetaiotaomicron strains against certain antimicrobials. Isolates were identified by conventional methods and API-20 A. Susceptibility tests were performed according to recommendations of NCCLS (M 11-A4) agar dilution methods. Beta-lactamase production was determined with nitrocefin discs. Forty-five clinical isolates (33 B. fragilis and 12 B. thetaiotaomicron) were from following sites: blood (n:8), intra-abdominal abscess (n:7), soft tissue (n:26), and miscellaneous foci of infection (n:4). Fifty B. fragilis and 60 B. thetaiotaomicron isolates from intestinal microbiota of individuals with no history of antimicrobial treatment within last 30 days were also examined. Beta-lactamase production was detected in 93% of clinical and 99% of intestinal isolates. The organisms including intestinal isolates were uniformly susceptible to metronidazole. The MIC90s of other antibiotics and resistance rates of all clinical isolates to those antibiotics were as follows: 256 microg/mL (93%) for ampicillin, 128 microg/mL (13%) for piperacillin, 64 microg/mL (11%) for cefoxitin, 1 microg/mL (2%) for amoxicillin-clavulanate, 0.5 microg/mL (2%) for imipenem, >256 microg/mL (36%) for clindamycin, 8 microg/mL (2%) for chloramphenicol. Intestinal isolates demonstrated similar resistance rates and MIC90s. Metronidazole, imipenem, amoxicillin-clavulanate seem to be effective drugs against these bacteria in Turkey.     

High rates of macrolide resistance among clinical isolates of Streptococcus agalactiae in Tunisia

One hundred sixty non duplicate erythromycin resistant Streptococcus agalactiae isolates were collected in Tunisia from January 2005 to December 2007 They were investigated to determine their resistance level to different macrolides and the mechanisms involved. Most erythromycin resistant S. agalactiae isolates were isolated from urinary specimens (38.75%, 62/160). The constitutive MLSB phenotype (cMLS) showed in 84.3% (135/160) with high MICs of macrolides and lincosamides (MIC90>256 microg/mL) and 8.2% (13/160) inducible MLSB phenotype (iMLS) with high MICs of macrolides (MIC90>256 microg/mL) and moderately increased MICs of lincosamides (MIC90=8 microg/mL). The M phenotype showed in 7.5% (12/160) with moderately increased MICs of macrolides (MIC90=32 microg/mL) and low MICs of lincosamides (MIC90=0.75 microg/mL). All strains were susceptible to quinupristun-dalfopristin association and linezolid (MIC90: 05 and 0.38 microg/mL respectively). Strains with MLSB phenotype harboured erm(B) gene with 825% (n=132), erm(TR) gene with 8.12% (n=13) and erm(B) plus mef (A) with 1.88% (n=3). All strains categorized as M phenotype carried the mef(A) gene (75%, n=12). cMLSB phenotype conferring cross resistance to macrolides, lincosamides and streptogramins B with high level of resistance was the most prevalent.