Screening of antimicrobial activities in red, green and brown macroalgae from Gran Canaria (Canary Islands, Spain)

Extracts from 44 species of seaweed from Gran Canaria (Canary Islands, Spain) were screened for the production of antibacterial and antifungal compounds against a panel of gram-negative and gram-positive bacteria, mycobacteria, yeasts and fungi. A total of 28 species displayed antibacterial activity, of which six also showed antifungal activity. Asparagopsis taxiformis and Cymopolia barbata were the species with the strongest activities against the broadest spectrum of target microorganisms. All the species with antibacterial activity were active against gram-positive bacteria, whereas only two species, A. taxiformis and Osmundea hybrida, were active against mycobacteria. The production of secondary metabolites with antimicrobial activities by the macroalgae was also studied under different conditions, although no common trend for bioactivity was observed.     

Antibacterial activity of aerial parts as well as in vitro raised calli of the medicinal plant Saraca asoca (Roxb.) de Wilde

Leaves, stem, and flowers of Saraca asoca, an endangered medicinal plant in India, and young explants cultivated on Murashige & Skoog's medium containing 6-benzylaminopurine were analyzed for antibacterial potential. Alcoholic and aqueous extracts from parent explants and their in vitro raised calli were tested by an agar well diffusion method. Minimal inhibitory concentrations (MICs) of the extracts were determined by broth microdilution method. Aqueous extracts showed antibacterial activity against limited bacterial species, whereas alcoholic extracts were active against a wider range of bacteria. Although the alcoholic extracts of all the explants and calli showed antibacterial activity, the extracts derived from flowers and their calli showed better results. Extracts derived from calli showed comparable results to the extracts from explants. Overall, the MICs of the extracts ranged from 0.039 to 1.25 mg/mL. MICs against gram-positive bacteria ranged from 0.078 to 1.25 mg/mL, whereas they ranged between 0.039 and 0.625 mg/mL against gram-negative bacteria. A MIC distribution plot showed that gram-negative bacteria were more susceptible to the extracts than gram-positive bacteria. It is concluded that extracts of S. asoca contain antibacterial agent, and as the calli gave good results, in vitro cultivation of the explants may be used to obtain antibacterial compounds. This is the first report on antibacterial activity of S. asoca, especially through in vitro raised calli.     

In vitro antibacterial activity of a new 1-oxa cephalosporin compound

The in vitro activity of a unique new 1-oxa cephalosporin beta-lactam antibiotic (LY 127935) was tested against clinical isolates of gram-positive and gram-negative bacteria and compared with the activities of cefoxitin, cefamandole, cephalothin, clindamycin, amikacin, tobramycin, gentamicin, ticarcillin, and carbenicillin. The new compound was observed to have a broad spectrum of antibacterial activity which far exceeded the activity of older cephalosporins against aerobic gram-negative enteric bacilli. This new compound was the most active drug tested against Klebsiella, Serratia, Enterobacter, indole-negative and positive Proteus species, and E. coli. Against clinical isolates of Pseudomonas species the new compound was more active than cefoxitin, cefamandole, cephalothin, and clindamycin, comparable to ticarcillin and carbenicillin, and less active than gentamicin, tobramycin, and amikacin. Yet, most of the Pseudomonas isolates were inhibited by 16 micrograms/ml of the new compound. Against both beta-lactamase and non beta-lactamase producing Staphylococcus aureus isolates, the new 1-oxa compound was less active than the older cephalosporins of which cephalothin and cefamandole were the most effective. The 1-oxa compound had no appreciable activity against isolates of Streptococcus faecalis. Activity of all four cephalosporins studied was decreased in the presence of an increased inoculum of Enterobacteriaceae in trypticase soy and Mueller-Hinton broth. The activity of the new compound against Pseudomonas species was also decreased by an increased inoculum in Mueller-Hinton but not in trypticase soy broth. These results indicate that this new 1-oxa compound may have great promise as a broad spectrum antibiotic and may warrant controlled clinical trials in man.     

In Vitro Antibacterial Activity of Minocycline and Effect of Agar Medium Utilized in Its Susceptibility Testing

The in vitro activity of minocycline against 1,028 bacterial strains was determined in parallel in Mueller Hinton Agar and Trypticase Soy Agar. The broad antibacterial effect of minocycline against gram-positive cocci and gram-negative bacilli is confirmed. Minimal inhibitory concentrations for gram-positive bacteria in Mueller Hinton Agar were at least twofold less than in Trypticase Soy Agar. Minimal inhibitory concentrations for gram-negative bacilli in Mueller Hinton Agar were usually fourfold less than in Trypticase Soy Agar.     

Antimicrobial activity of polycationic peptides

The in vitro activity of six polycationic peptides, buforin II, cecropin P1, indolicidin, magainin II, nisin, and ranalexin, were evaluated against several clinical isolates of gram-positive and gram-negative aerobic bacteria, yeasts, Pneumocystis carinii and Cryptosporidium parvum, by using microbroth dilution methods. The peptides exhibited different antibacterial activities and rapid time-dependent killing. The gram-negative organisms were more susceptible to buforin II and cecropin P1, whereas buforin II and ranalexin were the most active compounds against the gram-positive strains. Similarly, ranalexin showed the highest activity against Candida spp., whereas magainin II exerted the highest anticryptococcal activity. Finally, the peptides showed high anti-Pneumocystis activity, whereas no compound had strong inhibitory effect on C. parvum.     

Antibacterial Action of Spermine: Effect on Urinary Tract Pathogens

The basic polyamine spermine was tested for antibacterial activity at two pH levels by the modified cup method against a variety of gram-positive and gram-negative organisms isolated from urine. At pH 6.4, with concentrations ranging from 39 to 2,500 mug per 0.1 ml, there were no clear zones of inhibition seen with any of the gram-negative test organisms, although some adverse effect on growth within the area of the cylinder was noted in 36%. Three of 17 gram-positive strains were inhibited at this pH. Spermine was more active at pH 7.4, but even at the highest concentrations only 16% of the gram-negative and 47% of the gram-positive bacteria tested showed definite zones of inhibition. It is concluded that spermine probably plays little, if any, role in natural resistance to urinary tract infections in vivo.     

Phenyl thiazolyl urea and carbamate derivatives as new inhibitors of bacterial cell-wall biosynthesis

Over 50 phenyl thiazolyl urea and carbamate derivatives were synthesized for evaluation as new inhibitors of bacterial cell-wall biosynthesis. Many of them demonstrated good activity against MurA and MurB and gram-positive bacteria including MRSA, VRE and PRSP. 3,4-Difluorophenyl 5-cyanothiazolylurea (3p) with clog P of 2.64 demonstrated antibacterial activity against both gram-positive and gram-negative bacteria.     

Antibacterial activity of some unsymmetrical diorganyltellurium(IV) dichlorides

Six unsymmetrical diorganyltellurium(IV) dichlorides RR'TeCl2 (where R= phenacyl-, 1-naphthacyl-, and styrylacyl- and R' = p-methoxyphenyl, p-hydroxyphenyl-, and 3-methyl-4-hydoxyphenyl-) were tested for their antibacterial activity against gram-positive (Bacillus subtilis ATCC 6633 and Staphylococcus aureus ATCC 25923) and gram-negative (Escherichia coli ATCC 25922. Pseudomonas aeruginosa ATCC 27853 and Salmonella sp.) bacteria. Antibacterial activity was measured by disk diffusion method. Inhibition zones demonstrated that all the compounds showed good activity against gram-negative strains. Phenacyl (3-methyl-4-hydroxyphenyl) tellurium(IV) dichloride and naphthacyl (3-methyl-4-hydroxyphenyl) tellurium(IV) dichloride showed significant activity against both gram-positive and gram-negative strains. Among the tested compounds, the former exhibited maximum activity against gram-positive bacteria, while the latter against all the bacteria under study and styrylacyl (p-methoxyphenyl) tellurium(IV) dichloride against all the three gram-negative bacteria.     

产抑菌物质乳杆菌的筛选及性质的研究

从健康成年人的口腔中筛选出一株产抑菌物质的菌株HO-69,经API系统鉴定为植物乳杆菌。排除酸性末端产物与过氧化氢的影响后,HO-69的发酵上清液对变形链球菌等革兰氏阳性菌、大肠杆菌等革兰氏阴性菌具有抑制作用。抑菌物质经初步提取,推测其分子量在10kDa以下,胰蛋白酶处理后抑菌活性部分损失,100℃水浴加热20min依然保持较高的抑菌活力,显示活性的pH范围是3.0~7.0,活力随pH的降低而增强。     

QSAR study on antibacterial activity of sulphonamides and derived Mannich bases

The paper describes synthesis and comparative study on antibacterial activities of sulphonamides and Mannich bases derived from them. The compounds were screened for their antibacterial activity against various gram-positive and gram-negative bacteria and were analyzed statistically. The results have shown that the compounds are quiet active against pathogens under study and were nontoxic.     

Antimicrobial activities of some Bacillus spp. strains isolated from the soil

In this study a total of 29 Bacillus species isolated from the soil was analyzed using the agar diffusion method in terms of their general inhibition effects to some test bacteria. It has been found that isolates are effective against gram-positive and gram-negative bacteria whereas their extensive inhibition effect is particularly against gram-positive bacteria. On the other hand, B. cereus M15 strain has an inhibitory effect against both gram-positive and gram-negative bacteria. Furthermore some isolates are more effective against test bacteria when compared to some antibiotics.     

Antimicrobial Properties of Oleuropein and Products of Its Hydrolysis from Green Olives

Oleuropein, the bitter glucoside in green olives, and products of its hydrolysis were tested for antibacterial action against certain species of lactic acid bacteria involved in the brine fermentation of olives. Oleuropein was not inhibitory, but two of its hydrolysis products, the aglycone and elenolic acid, inhibited growth of the four species of lactic acid bacteria tested. Another hydrolysis product, beta-3,4-dihydroxyphenylethyl alcohol, was not inhibitory. The aglycone of oleuropein and elenolic acid were much more inhibitory when the broth medium contained 5% NaCl; 150 mug of either compound per ml prevented growth of Lactobacillus plantarum. A crude extract of oleuropein, tested by paper disk bioassay, was inhibitory to 3 of 17 species of bacteria screened, none of which were lactic acid bacteria. The acid hydrolysate of the extract was inhibitory to 11 of the bacteria, which included four species of lactic acid bacteria and other gram-positive and gram-negative species. Neither crude preparation was inhibitory to growth of the seven species of yeasts tested. A possible explanation is given for the previously reported observation that heating (3 min, 74 C) olives prior to brining renders them more fermentable by lactic acid bacteria. Results of a brining experiment indicated that oleuropein is degraded to antibacterial compounds when unheated olives are brined.     

The anti-platelet drug ticlopidine inhibits FapC fibrillation and biofilm production: Highlighting its antibiotic activity

Multidrug resistance of bacteria and persistent infections related to biofilms, as well as the low availability of new antibacterial drugs, make it urgent to develop new antibiotics. Here, we evaluate the antibacterial and anti-biofilm properties of ticlopidine (TP), an anti-platelet aggregation drug, TP showed antibacterial activity against both gram-positive (MRSA) and gram-negative (E. coli, and P. aeruginosa) bacteria over a long treatment period. TP significantly reduced the survival of gram-negative bacteria in human blood though impact on gram-positives was more limited. TP may cause death in MRSA by inhibiting staphyloxanthin pigment synthesis, leading to oxidative stress, while scanning electron microscopy imaging indicate a loss of membrane integrity, damage, and consequent death due to lysis in gram-negative bacteria. TP showed good anti-biofilm activity against P. aeruginosa and MRSA, and a stronger biofilm degradation activity on P. aeruginosa compared to MRSA. Measuring fluorescence of the amyloid-reporter Thioflavin T (ThT) in biofilm implicated inhibition of amyloid formation as part of TP activity. This was confirmed by assays on the purified protein in P. aeruginosa, FapC, whose fibrillation kinetics was inhibited by TP. TP prolonged the lag phase of aggregation and reduced the subsequent growth rate and prolonging the lag phase to very long times provides ample opportunity to exert TP's antibacterial effect. We conclude that TP shows activity as an antibiotic against both gram-positive and gram-negative bacteria thanks to a broad range of activities, targeting bacterial metabolic processes, cellular structures and the biofilm matrix.     

Antibiotic activity of marine gram-negative bacteria]

An antimicrobial substance was isolated from the culture fluid of Vibrio fischeri belonging to ++gram-negative sea bacteria. The substance was shown to be highly active against ++gram-positive cocci and less active against some other ++gram-positive bacteria and fungi. The active substance was defined as a low molecular weight compound which appeared to be thermostable and had positive ninhydrin reaction. The antibiotic formed when the culture was grown in the media containing sea water and protein hydrolysates or yeast extract during the exponential phase. The maximum antibiotic activity was observed during the stationary phase of culture development.     

Antibacterial activity of extracts and neolignans from Piper regnellii (Miq.) C. DC. var. pallescens (C. DC.) Yunck

The evaluation of the activity of the aqueous and ethyl acetate extracts of the leaves of Piper regnellii was tested against gram-positive and gram-negative bacteria. The aqueous extract displayed a weak activity against Staphylococcus aureus and Bacillus subtilis with minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of 1000 micrograms/ml. The ethyl acetate extract presented a good activity against S. aureus and B. subtilis with MIC and MBC at 15.62 micrograms/ml. In contrast to the relative low MICs for gram-positive bacteria, gram-negative bacteria were not inhibited by the extracts at concentrations < or = 1000 mg/ml. The ethyl acetate extract was fractionated on silica gel into nine fractions. The hexane and chloroform fractions were active against S. aureus (MIC at 3.9 micrograms/ml) and B. subtilis (MIC at 3.9 and 7.8 micrograms/ml, respectively). Using bioactivity-directed fractionation, the hexane fraction was rechromatographed to yield the antimicrobial compounds 1, 2, 5, and 6 identified as eupomatenoid-6, eupomatenoid-5, eupomatenoid-3, and conocarpan, respectively. The pure compounds 1 and 2 showed a good activity against S. aureus with MIC of 1.56 micrograms/ml and 3.12 micrograms/ml, respectively. Both compounds presented MIC of 3.12 micrograms/ml against B. subtilis. The pure compound 6 named as conocarpan was quite active against S. aureus and B. subtilis with MIC of 6.25 micrograms/ml. The antibacterial properties of P. regnellii justify its use in traditional medicine for the treatment of wounds, contaminated through bacteria infections.     

Allylsulfide constituents of garlic volatile oil as antimicrobial agents.

Six different mixtures of garlic distilled oils containing diallyl disulfide (DDS) and diallyl trisulfide (DTS), ranging from 1 to 51% and 88 to 38% respectively, have been assayed against a number of yeasts (C. albicans, C. tropicalis and B. capitatus), gram-positive bacteria (S. aureus and B. subtilis) and gram-negative bacteria (P. aeruginosa and E. coli). Results obtained support a specific antifungal more than an antibacterial activity and implicate DDS as the active constituent. Incubation of garlic extracts made up of 1% DDS and 88% DTS resulted, in fact, in the absence of growth inhibition against all the tested microorganisms, whereas garlic oils with higher quantities of DDS showed significant inhibitory activity, increasing with the increase of DDS amount.     

Antibacterial activity of a sulfated galactan extracted from the marine alga <Emphasis Type="Italic">Chaetomorpha aerea</Emphasis> against <Emphasis Type="Italic">Staphylococcus aureus</Emphasis>

The in vitro antimicrobial activity of the marine green algae Chaetomorpha aerea was investigated against gram-positive bacteria, gram-negative bacteria, and a fungus. The water-soluble extract of algae was composed of a sulfated (6.3%) galactan with a molecular weight of 1.160 × 10⁶ Da and a global composition close to commercial polysaccharides, such as dextran sulfate or fucoidan. The polysaccharide was composed of 18% arabinose, 24% glucose, and 58% galactose. The re-suspended extracts (methanol, water) exhibited selective antibacterial activities against 3 gram-positive bacteria including Staphylococcus aureus (ATCC 25923). Minimum inhibitory concentration and minimum bactericidal concentration tests showed that the sulfated galactan could be a bactericidal agent for this strain (40 mg/mL). The results of this study confirmed the potential use of the green algae Chaetomorpha aerea as a source of antibacterial compounds.     

4-Alkyl and 4,4'-dialkyl 1,2-bis(4-chlorophenyl)pyrazolidine-3,5-dione derivatives as new inhibitors of bacterial cell wall biosynthesis

Over 195 4-alkyl and 4,4-dialkyl 1,2-bis(4-chlorophenyl)pyrazolidine-3,5-dione derivatives were synthesized, utilizing microwave accelerated synthesis, for evaluation as new inhibitors of bacterial cell wall biosynthesis. Many of them demonstrated good activity against MurB in vitro and low MIC values against gram-positive bacteria, particularly penicillin-resistant Streptococcus pneumoniae (PRSP). Derivative 7l demonstrated antibacterial activity against both gram-positive and gram-negative bacteria. Derivatives 7f and 10a also demonstrated potent nanomolar Kd values in their binding to MurB.     

Antibacterial activity of soluble pyridinium-type polymers

Cross-linked poly(N-benzyl-4-vinylpyridinium halide) (designated insoluble BVP) was previously reported to capture bacterial cells alive by contact with them. The corresponding linear polymer poly(N-benzyl-4-vinylpyridinium salt) (designated soluble BVP) was found to exhibit antibacterial activity. This soluble pyridinium-type polymer showed strong antibacterial activity against gram-positive bacteria, whereas it was less active against gram-negative bacteria. The antibacterial activity of this cationic, polymeric disinfectant was considerably greater than that of the corresponding monomeric compound and was approximately equal to that of conventional disinfectants such as benzalkonium chloride and chlorohexidine.     

Antibacterial activity of soluble pyridinium-type polymers.

Cross-linked poly(N-benzyl-4-vinylpyridinium halide) (designated insoluble BVP) was previously reported to capture bacterial cells alive by contact with them. The corresponding linear polymer poly(N-benzyl-4-vinylpyridinium salt) (designated soluble BVP) was found to exhibit antibacterial activity. This soluble pyridinium-type polymer showed strong antibacterial activity against gram-positive bacteria, whereas it was less active against gram-negative bacteria. The antibacterial activity of this cationic, polymeric disinfectant was considerably greater than that of the corresponding monomeric compound and was approximately equal to that of conventional disinfectants such as benzalkonium chloride and chlorohexidine.