Ureas of 5-aminopyrazole and 2-aminothiazole inhibit growth of gram-positive bacteria

Ureas of 5-aminopyrazole and 2-aminothiazole emerged as lead compounds from a high-throughput screen assaying the growth of Staphylococcus aureus. Structure–activity relationships were developed for each compound series. Several compounds were also tested for activity against drug resistant strains of S. aureus in vivo.     

Genotyping of Staphylococcus aureus isolated from humans, bovine subclinical mastitis and food samples in Argentina

The aim of the present study was to characterize genotypically 45 Staphylococcus aureus strains isolated from humans, bovine subclinical mastitis and food samples in Argentina by rep-PCR and PCR amplification of virulence genes. Resistances to various antibiotics could be observed for the human S. aureus, less pronounced for the bovine strains, but not for the eight S. aureus isolated from food samples. The strains could be classified genotypically by rep-PCR and by amplification of the genes encoding protein A, coagulase, clumping factor, the collagen adhesin domains A and B, capsular polysaccharide 5 and 8, the accessory gene regulator agr classes I to III, and the S. aureus gene regulator sae. rep-PCR analyses and the different gene patterns revealed that the strains could be divided into seven groups mostly matching with the origin of the isolates. The present study describes genotypic variations of S. aureus strains isolated from different origins in Argentina. The study provides a valuable insight into molecular specificities of this important pathogen.     

Rapid detection of Staphylococcus aureus strains having reduced susceptibility to vancomycin using a chemiluminescence-based drug-susceptibility test

Current drug-susceptibility tests used routinely in clinical laboratories sometimes fail to identify strains of Staphylococcus aureus with reduced susceptibility to vancomycin. To solve this problem, we have developed a more sensitive and rapid method that measures bacterial metabolic activity by a chemiluminescence-based technique. This method is able to discriminate such strains from vancomycin-susceptible S. aureus with a sensitivity and specificity of > 95%. This rapid and reliable method appears to be promising for detection of vancomycin-intermediate S. aureus strains in clinical laboratories, and may supersede classical susceptibility testing.     

Multifactorial aspects of antimicrobial activity of propolis

We investigated the antibacterial activity of sub-inhibitory concentrations of ethanolic extract of propolis (EEP), and its effect on the antibacterial activity of some antibiotics. Some clinically isolated Gram-positive strains were used.

Moreover, sub-inhibitory concentrations of EEP were used to value its action on some important virulence factors like lipase and coagulase enzymes, and on biofilm formation in Staphylococcus aureus.

Our results indicated that EEP had a significant antimicrobial activity towards all tested clinical strains.

Adding EEP to antibacterial tested drugs, it drastically increased the antimicrobial effect of ampicillin, gentamycin and streptomycin, moderately the one of chloramphenicol, ceftriaxon and vancomycin, while there was no effect with erithromycin.

Moreover, our results pointed out an inhibitory action of EEP on lipase activity of 18 Staphylococcus spp. strains and an inhibitory effect on coagulase of 11 S. aureus tested strains.

The same EEP concentrations showed a negative interaction with adhesion and consequent biofilm formation in S. aureus ATCC 6538P.     

Synthesis and evaluation of anticancer benzoxazoles and benzimidazoles related to UK-1

UK-1 is a structurally unique bis(benzoxazole) natural product isolated from a strain of Streptomyces. UK-1 has been reported to possess anticancer activity but no activity against bacteria, yeast, or fungi. Previous work has also demonstrated the ability of UK-1 to bind a variety of di- and tri-valent metal ions, particularly Mg²⁺ ions, and to form complexes with double-stranded DNA in the presence of Mg²⁺ ions. Here we report the activity of UK-1 against a wide range of human cancer cell lines. UK-1 displays a wide spectrum of potent anticancer activity against leukemia, lymphoma, and certain solid tumor-derived cell lines, with IC₅₀ values as low as 20 nM, but is inactive against Staphylococcus aureus, a methicillin-resistant strain of S. aureus, or Pseudomonas aeruginosa. A series of analogues of the bis(benzoxazole) natural product UK-1 in which the carbomethoxy-substituted benzoxazole ring of the natural product was modified were prepared and evaluated for their anticancer and antibacterial properties. An analogue of UK-1 in which the carbomethoxy-substituted benzoxazole ring was replaced with a carbomethoxy-substituted benzimidazole ring was inactive against human cancer cell lines and the two strains of S. aureus. In contrast, a simplified analogue in which the carbomethoxy-substituted benzoxazole ring was replaced with a carbomethoxy group was almost as active as UK-1 against the four cancer cell lines examined but lacked activity against S. aureus. Metal ion binding studies of these analogues demonstrate that they both bind Zn²⁺ and Ca²⁺ ions about as well as UK-1. The non-cytotoxic benzimidazole UK-1 analogue binds Mg²⁺ ions 50-fold weaker than UK-1, whereas the simple benzoxazole analogue binds Mg²⁺ ions nearly as well as UK-1. These results support a role of Mg²⁺ ion binding in the selective cytotoxicity of UK-1 and provide a minimal pharmacophore for the selective cytotoxic activity of the natural product.     

PCR fingerprinting for epidemiological studies of Staphylococcus aureus

Staphylococcus aureus isolates (n = 126), collected during two different periods from patients hospitalised in pediatric wards, were analysed using polymerase chain reaction (PCR) mediated genotyping. These isolates were compared with 29 isolates from individuals attending the out-patient clinic of the same hospital and 13 isolates from pediatric hospital personnel. Within a group of 99 isolates gathered from 48 individuals during surveillance period I, 22 distinct genotypes were identified by application of two PCR assays. Among the 58 isolates collected in surveillance period II from pediatric and out-clinic patients, 25 genotypes were detected by a single PCR assay only. Based on these results it was demonstrated that patients can be colonised with multiple strains that may persist in a certain anatomical location for prolonged periods of time. It is shown that persistence of a S. aureus strain in a pediatric ward can be deduced from the PCR genotyping studies. As such PCR can be used for longitudinal monitoring of bacterial infections in hospital departments, analysis of patient-to-patient and personnel-to-patient transmission and for detection of genetic variation in general in S. aureus. Also, isolate-specific DNA probes can be generated for S. aureus by PCR genotyping. The probes can be used for the recognition of re-emerging S. aureus epidemics.     

The investigation of Staphylococcus aureus and coagulase-negative staphylococci nasal carriage among patients undergoing haemodialysis

The frequency of nasal staphylococcal colonization among haemodialysed patients was investigated. The swabs were collected in 1998 and 2004 from 28 and 43 patients, respectively.

Staphylococcus aureus colonization rates were 57.1% and 27.9% in 1998 and 2004, respectively. Twenty-six coagulase-negative staphylococci (CNS) isolates were cultured: S. epidermidis (21), S. lugdunensis (2), single S. haemolyticus, S. warneri, and S. capitits isolates. One S. aureus and 10 CNS isolates were methicillin resistant. The methicillin-resistant S. aureus (MRSA) was resistant to β-lactams, tetracycline, and harbored the pvl gene encoding the Panton-Valentine leukocidin.

The decrease in S. aureus colonization at 6-year interval was observed. The presence of the pvl gene and a favorable antibiotic susceptibility pattern of the MRSA suggest that the isolate was a member of community-acquired MRSA (CA-MRSA). Concluding, screening of haemodialysed patients for staphylococcal colonization accompanied by characterization of cultured isolates is important to understand its epidemiology and to develop infection prevention measures and treatment strategies.     

Detection of Staphylococci in Mouse Phagocytic Cells by in Situ Hybridization Using Biotinylated Dna Probes

In situ hybridization was used to detect intracellular Staphylococcus aureus and S. epidermidis in mouse phagocytic cells after experimental infection of C3H mice with Staphylococci via abdominal or intravenous injection. Isolated ascites or whole blood were tested by the phagocyte smear technique, using bacteriolytic enzymes to preserve phagocytic cell morphology. The exposed bacterial DNA was visualized as intracellular hybridized signals by use of biotinylated DNA probes and by immunocytochemistry using streptavidin-alkaline phosphatase conjugates as detector molecules. These DNA probes, prepared from randomly cloned genomic DNA fragments of S. aureus and S. epidermidis, were strain-specific and did not cross-hybridize either in situ or on dot-blot hybridization. This technique of in situ hybridization with phagocyte smears is useful for detection and diagnosis of intracellular bacteria regardless of viability.     

Antibacterial activity from Penicillium corylophilum Dierckx

A strain of Penicillium corylophilum isolated from Brazilian soil sample was submitted to different culture conditions to investigate the production of secondary metabolites with antimicrobial activity. The largest number of conidia was obtained after 5 days of incubation in oat medium and the highest level of antimicrobial activity was produced when the fungus culture was developed in the Czapek medium. The activity against Staphylococcus aureus was found only in the chloroform extract from Czapek culture broth, which also showed activity against Micrococcus luteus. Fumiquinozoline F was isolated from the active chloroform extract by using chromatographic methods. The minimal inhibitory concentration (MIC) values for M. luteus and S. aureus were 99 μg/mL and 137 μg/mL, respectively.     

家蚕幼虫BmToll9基因对肽聚糖和金黄色葡萄球菌的响应表达

【目的】Toll信号通路是昆虫中重要的免疫信号通路,其中Toll受体在保持Toll通路的正常免疫应答、抵抗外源病原体中起到关键的作用。本研究旨在探究肽聚糖和金黄色葡萄球菌Staphylococcus aureus对家蚕Bombyx mori Toll受体基因BmToll9-1和BmToll9-2表达的影响。【方法】将革兰氏阳性菌细胞壁主要成分肽聚糖和革兰氏阳性菌金黄色葡萄球菌分别注射感染家蚕5龄第1天幼虫,诱导其发生免疫反应;采用实时荧光定量PCR分析注射后不同感染时间点BmToll9-2和BmToll9-1基因在家蚕幼虫中肠、表皮、脂肪体和丝腺中的相对表达水平。【结果】往家蚕5龄幼虫中注射肽聚糖或金黄色葡萄球菌后,BmToll9-2基因出现了时间和组织的差异性表达。注射肽聚糖和金黄色葡萄球菌均能诱导5龄幼虫中肠BmToll9-2基因的表达上调,注射肽聚糖和金黄色葡萄球菌分别在3和6 h时对基因表达的诱导效果最好,且注射金黄色葡萄球菌比注射肽聚糖对基因表达的诱导效果更好。注射金黄色葡萄球菌能引起5龄幼虫表皮、脂肪体和丝腺中BmToll9-2基因的表达上调,分别于注射后24, 6和24 h时诱导效果最好。注射金黄色葡萄球菌亦能诱导同源的BmToll9-1基因的上调表达。【结论】家蚕幼虫BmToll9基因在肽聚糖或金黄色葡萄球菌注射处理后均能在不同组织中发生上调表达,推测BmToll9基因参与了家蚕对肽聚糖和金黄色葡萄球菌的免疫反应。     

A remote-query sensor for predictive indication of milk spoilage

Described is application of the remote-query (wireless, passive) magnetoelastic sensor platform for direct detection and monitoring of bacterium contamination of milk within hermetically sealed containers. Specific application is made to the quantification of Staphylococcus aureus ssp. anaerobius (S. aureus) concentrations in milk. S. aureus growth changes milk viscosity, in turn changing the resonance frequency of the liquid immersed sensor allowing S. aureus concentrations of 10³ to 10⁷ cells ml⁻¹ to be directly quantified.     

Study on antimicrobial activity of chitosan with different molecular weights

E. coli and Staphylococcus aureus are used to study the antimicrobial activity of chitosan of different molecular weights (MW). The effect of the concentration and MW of chitosan were investigated, respectively, and the antimicrobial mechanism was discussed. For chitosan with MW below 300 kDa, the antimicrobial effect on S. aureus was strengthened as the MW increased. In contrast, the effect on E. coli was weakened.     

Synthesis and microbial inhibition study of novel 5-imidazolyl substituted isoxazolidines

Cycloaddition of C-imidazolyl-N-phenylnitrones with monosubstituted alkenes afforded 5-imidazolyl substituted isoxazolidines with high regioselectivity. Novel isoxazolidines were screened for their antibacterial activities against S. aureus, E. coli and B. subtilis by using streptomycin as a positive control. They were also tested for their antifungal activities against F. moniliforme, A. niger and C. acremonium by using nystatin as a positive control. Isoxazolidines, 4a and 4f exhibited more potent inhibition towards antifungal activity than the other isoxazolidines prepared.     

Preparation and characterization of konjac glucomannan/poly(diallydimethylammonium chloride) antibacterial blend films

A novel antibacterial film was prepared by blending konjac glucomannan (KGM) and poly(diallydimethylammonium chloride) (PDADMAC) in an aqueous system. The antibacterial activity of the films against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Saccharomyces were measured by the halo zone test and the double plate method. The films exhibited an excellent antibacterial activity against B. subtilis and S. aureus but not against E. coli, P. aeruginosa or Saccharomyces. The miscibility, morphology, thermal stability, water vapour permeability and mechanical properties of the blend films were investigated by density determination, SEM, ATR-IR, XRD, DSC, TGA, WVA and tensile tests. The results of density determination predicted that the blends of KGM and PDADMAC were miscible when the PDADMAC content was less than 70 wt%. Moreover, SEM and XRD confirmed the result. ATR-IR showed that strong intermolecular hydrogen bonds and electrostatic interactions occurred between KGM and PDADMAC in the blends. The tensile strength and the break elongation of the blends were improved largely to 106.5 MPa and 32.04% and the water vapour permeability decreased when the PDADMAC content was 20 wt%. The thermal stability of the blends was higher than pure KGM. The blends should be good antibacterial materials.     

掺银二氧化钛空心球的制备及其抗菌性能研究

以硫酸钛、尿素为原料,碳球为模板,采用水热沉淀法制备了二氧化钛空心球,以聚乙烯吡咯烷酮(PVP)为分散剂、硼氢化钾还原硝酸银的方法得到银掺杂的二氧化钛空心球。采用X射线粉末衍射仪(XRD)、扫描电镜(SEM)、透射电镜(TEM)、能谱仪(EDS)和傅里叶变换红外光谱仪(FT-IR)等测试手段对所得的样品进行了表征。采用抑菌圈法对其抗菌性能进行了检测,实验结果表明,在自然光条件下,商品二氧化钛P25和二氧化钛空心球对大肠杆菌、金黄色葡萄球菌、白色念珠菌没有任何抗菌效果,而载银量9.4 mol%的二氧化钛在常温范围内对三个菌种都具有优良的抗菌性能,可用于抗菌塑料、抗菌食品包装和抗菌纺织制品等领域。     

What determines nasal carriage of Staphylococcus aureus?

Nasal carriage of Staphylococcus aureus is an important risk factor for infection by this organism in both community and hospital settings; this article reviews the role of host and bacterial factors in carriage. A host genetic influence appears likely but the phenotypic determinants are unknown. Possibilities include variability in host adhesins, immune response or secretion of antimicrobial molecules. Colonization resistance by S. aureus, together with the observation that persistent carriers often carry a single strain whereas intermittent carriers can be colonized with unrelated strains over time, suggests that bacterial factors could also be involved.     

Mutants of Staphylococcus aureus deficient in recombinational repair : Improved isolation by selecting for mutants exhibiting concurrent sensitivity to ultraviolet radiation and N-methyl-N′-nitro-N-Nutrosoguanidine

Recombination-deficient (rec) mutants of Staphylococcus aureus strains 152 and Ps29 were sought by initially screening mutagenized cultures for mutants exhibiting increased sensitivity to both ultraviolet (UV) radiation and N-methyl-N′-nitro-N-nitrosoguanidine (NG). Mutants thus isolated were analyzed for recombinational ability by transduction, and further characterized in terms of sensitivity to UV, NG, ability to repair UV-irradiated bacteriophage, and spontaneous and UV-induced DNA degradation. Mutagenesis of strain 152 yielded three isolates, one of which was rec, the second potentially lex, and the third possessing an undetermined repair deficiency. Mutagenesis of strain Ps29 resulted in the isolation of one mutant, which exhibited a rec genotype. In searching for rec mutants of S. aureus, the value of initially screening mutagenized cultures for mutants exhibiting concurrent sensitivity to UV and NG, as opposed to screening for UV sensitivity alone, is discussed.     

Preparation and performance evaluation of glucomannan–chitosan–nisin ternary antimicrobial blend film

The material behaviour and antimicrobial effect of konjac glucomannan edible film incorporating chitosan and nisin at various ratio or concentrations is discussed. This activity was tested against food pathogenic bacteria namely Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, and Bacillus cereus. Mechanical and physical properties were determined and the results indicated that the blend film KC2 (mixing ratio konjac glucomannan 80/chitosan 20) showed the maximum tensile strength (102.8 ± 3.8 MPa) and a good transparency, water solubility, water vapor transmission ratio. The differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), etc. were used to characterize the structural change of the blend films. The results showed that the strong intermolecular hydrogen bonds took place between chitosan and konjac glucomannan. Incorporation of nisin at 42,000 IU/g of film for the selected blend film KC2 was found to have antimicrobial activity against S. aureus, L. monocytogenes, and B. cereus. The antimicrobial effect of chitosan or KC2 incorporating nisin was much better than that of konjac glucomannan incorporating nisin at each corresponding concentration and existed significant difference (p < 0.05), however, there was no significant difference on the antimicrobial effect between chitosan and KC2 both incorporating nisin. At all these levels, the ternary blend film KC2-nisin had a satisfactory mechanical, physical properties and antimicrobial activity, and could be applied as a potential ‘active’ packaging material.     

Hydrazones of 2-aryl-quinoline-4-carboxylic acid hydrazides: synthesis and preliminary evaluation as antimicrobial agents

A new series of 2-arylquinoline-4-carboxylic acid hydrazide–hydrazones was synthesized using an appropriate synthetic route. All the target compounds were evaluated for their in vitro antimicrobial activity against Staphylococcus aureus as an example for Gram-positive bacteria, Escherichia coli as an example for Gram-negative bacteria, and Candida albicans as a representative of fungi. The minimum inhibitory concentration (MIC) was determined for test compounds as well as for reference standards. Among the compounds tested, compounds having nitro substituents at the arylidene moiety showed the most potent antifungal as well as antibacterial activities against E. coli. Compound 23 displayed an antifungal activity comparable to that of nystatin. However, none of the compounds demonstrated any antibacterial activity against S. aureus. Hydrophobicity of the target compounds correlated weakly with their antibacterial and antifungal activities. The most potent compounds namely, 7, 18, 19, 22, and 23 were assessed for hemolytic toxicity and found to be non-hemolytic up to a concentration of 100 μg/mL. In addition, the most potent compound (23) was evaluated for in vitro cytotoxic activity against various cancer cell lines. This compound was found to display no cytotoxic activity but rather it induces the proliferation rate of Hep-G2 cells.     

Evaluation of electron spin resonance for studies of superoxide anion production by human neutrophils interacting with Staphylococcus aureus and Staphylococcus epidermidis

The present study evaluates electron spin resonance (ESR) and the spin trapper 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide (DEPMPO) for analysis of superoxide radical production by human neutrophils interacting with viable Staphylococcus aureus and Staphylococcus epidermidis bacteria. To avoid auto-activation due to interaction with glass surfaces, neutrophils were preincubated in plastic tubes until the peak response was reached, and then transferred to a quartz flat cell to record the ESR spectra. The time point for peak response was identified by parallel analysis of the bacteria–neutrophil interaction using luminol amplified chemiluminescence. We found detectable ESR spectra from neutrophils interacting with as few as five bacteria of the weak activating S. epidermidis per neutrophil. Addition of the NADPH oxidase inhibitor diphenylene iodonium totally abolished spectra. Catalase, DMSO or an iron chelator had no impact on the produced spectra and ionomycin, a selective activator of intracellular NADPH oxidase, gave significant ESR spectra. Taken together, our results indicate that DEPMPO is cell permeable and detects NADPH oxidase derived superoxide anions formed in phagosomes or released by human neutrophils phagocytosing viable S. aureus and S. epidermidis. The technique may be used as a sensitive tool to evaluate superoxide anion production in human neutrophils.