Inhibition of Streptococcus mutans adhesion to buccal epithelial cells by an aqueous extract of Thymus vulgaris.

OBJECTIVES: The aim of this study was to investigate the effect of an extract of Thymus vulgaris (thyme) on the growth of Streptococcus mutans (S. mutans) and the adhesion of this bacterium to human buccal epithelial cells. METHODS: Different concentrations of an aqueous extract of thyme were prepared and the effects investigated on growth of S. mutans. Furthermore, the effect of these extracts on adhesion of S. mutans to buccal epithelial cells was also investigated and compared with the effects of chlorhexidine digluconate. RESULTS: The data revealed that exposure of S. mutans to thyme extract showed a time and concentration-dependent decrease in bacterial viability. The greatest effect was observed when S. mutans had been exposed to 20% thyme extract for a period of 48 h which resulted in 96% inhibition of bacterial growth. Furthermore, the adhesion of S. mutans to buccal epithelial cells was also reduced when either buccal epithelial cells or S. mutans had been pre-incubated with different concentrations of aqueous thyme extracts (83-98% and 75-89% inhibition respectively). There was also greater reduction in the adherence of bacterial cells to buccal epithelial cells after mouth rinsing with 20% aqueous thyme extract compared to rinsing with chlorhexidine digluconate (45% and 89% inhibition of bacterial adhesion respectively). CONCLUSION: The diminished adherence of S. mutans to buccal epithelial cells after exposure to various concentrations of aqueous thyme extract as well as the antimicrobial properties of this plant may have clinical relevance.

A promising peptide antibiotic from Terfezia claveryi aqueous extract against Staphylococcus aureus in vitro.

The antimicrobial activity of aqueous and methanolic extracts, as well as partially purified proteins extracted from Terfezia claveryi aqueous extract were investigated against Staphylococcus aureus in vitro. A 5% aqueous extract inhibited the growth of S. aureus by 66.4%, while a methanolic extract was ineffective. Partial protein purification of the aqueous extract using ammonium sulphate precipitation revealed that antimicrobial activity was within the third fraction. This fraction was then subjected to gel filtration using Sephadex G-100. Two peaks were obtained. Peak one possessed higher antimicrobial activity. This peak was then subjected to ion exchange chromatography using DEAE Sephadex. Only peak 4 from the six peaks obtained showed a slight antimicrobial activity. Antimicrobial activities of the aqueous extract and the fractions that showed antimicrobial activity were compared with reference antibiotics.

Effect of date extract on growth and hemolytic activity of Streptococcus pyogenes.

The effect of date extract on growth and hemolytic activity of S. pyogenes was examined. It was found that 5% DE caused 78 % growth inhibition. However, 20% DE inhibited the growth by 86%. 5% DE inhibited hemolysin and streptolysin O activities by 43% and 24% respectively,while 20% caused 95 and 91 %inhibition.

Ultrastructural effects of date extract on Candida albicans.

The effect of Berhi date extract on the ultrastructure of Candida albicans was studied by scanning and transmission electron microscopy. Exposure of yeast to 5% (w/v) date extract showed evidence of weakening in the cell wall with indications of cell distortion and partial collapse in some cases as seen by scanning electron microscopy. Increasing the concentration of date extract (20%, w/v) led to more drastic damage to the yeast with cell lysis and concurrent leakage of cytoplasmic material with eventual cell death. Ultrastructural investigation showed irregular shapes of cells treated with date extract, with prominent effects on cell wall layers. Cell membranes lost their integrity, aggregation of the cytoplasmic contents and large detachment of plasmalemma from cell wall was observed in the treated cells. These results suggest that date extract may have multiple effects on Candida with an increasing potential of using it for prophylaxis purposes.

Isolation of Candida species from domestic sewage in Jordan.

Saccharomyces cerevisiae and various species of Candida were isolated and identified from the Al-Baqa'a sewage treatment station. Potentially pathogenic yeasts were detected in sewage samples and Candida krusei was found in the treated effluent. There was a 90-100% reduction in the number of yeast found in treated sewage effluent compared with raw sewage. Seasonal variations of total yeast counts are also reported.

Growth and photosynthetic activities of acclimated cyanobacteria in sewage effluents.

Various types of cyanobacteria were isolated from sewage of Kuwait. The growth and photosynthesis of these acclimated cyanobacteria on sterilized sewage effluents were studied. Primary treated effluent was found to support the growth of the cyanobacteria more than treated effluent. This indicated the possible tolerance of such cyanobacteria to more organic pollution in comparison with unacclimated cyanobacteria. The results explain in part the possible hazards of dumping sewage effluents into the sea or the possible uses of such cyanobacteria in mass culture as an animal food.

Effect of gibberellic acid on photosynthesis and glycollate dehydrogenase in Anacystis nidulans.

Gibberellic acid at 10(-4) MXXX was optimal for enhancement of growth, O2 evolution, photosystem II and I and the activity of glycollate dehydrogenase of Anacystis nidulans. A stimulatory effect was observed on photosystem II. Other concentrations of gibberellic acid were inhibitory to O2 evolution and photosystem I. Syntheses of phycocyanin, phycoerythrin and ß-carotene were significantly enhanced after 48 h incubation with gibberellic acid at 10(-3) MXXX but the chlorophyll content began to increase 3 h after adding 10(-4) MXXX gibberellic acid.

Lysis of cyanobacteria with Flexibacter spp isolated from domestic sewage.

Five species of filamentous cyanobacteria and two species of Flexibacter were isolated from domestic sewage. Cells and filtrates of F. flexilis and F. sancti lysed the cyanobacterium Oscillatoria williamsii. Inhibition of the photosynthetic electron transport reactions, and glycolate dehydrogenase and nitrogenase activity of O. williamsii due to its incubation with F. flexilis, were observed. Scanning electron micrographs revealed the attachment of F. flexilis to the sheaths of O. williamsii which resulted in the excretion of lysozyme and lysis of the cyanobacterium. Seasonal variations of Flexibacter spp showed that they were more abundant in the aeration tanks during June compared with sewage effluents.

Effect of Honey on Bacterial Growth and Spore Germination.

The effect of honey on the growth of Bacillus cereus , Staphylococcus aureus , Salmonella dublin and Shigella dysenteriae was examined in this study. Gram-positive bacteria were found to be less sensitive to the inhibitory action of honey compared to gram-negative bacteria. Significant growth inhibition (p<0.05) of S. dublin and S. dysenteriae was obtained by using 2% (vol/vol) honey. Spore germination of B. cereus was also significantly inhibited (P<0.05) by 2% (vol/vol) honey. The inhibitory factor(s) is under investigation.

Ethanolic dehydration and its effect on membrane-bound enzymes of Chlorogloeopsis fritschii and Chlorella pyrenoidosa.

Ethanolic dehydration (20% to 70%) of the thylakoid membranes of Chlorogloeopsis fritschii resulted in an 8% to 58% loss of glutamine synthetase activity. In Chlorella pyrenoidosa, hydroxypyruvate reductase and fumarase, marker enzymes of the peroxisomes and mitochondria, respectively, diffused from the organelles on dehydration.

Intracellular localization of glutamine synthetase in Chlorogloeopsis fritschii.

After differential centrifugation of cell-free extracts of Chlorogloeopsis fritschii, 71% of the original glutamine synthetase (GS) activity was associated with the thylakoids, while little activity was detected in the cytoplasmic membranes. Monospecific antiserum to a purified GS inhibited 88% of the enzyme activity in solubilized thylakoid membranes. An antiserum raised against thylakoids gave 81% inhibition. However, using intact thylakoid membranes, only 7% inhibition was obtained with the GS antiserum, indicating that GS is located inside the thylakoid membranes.

The presence of glycollate oxidase and dehydrogenase in Dunaliella primolecta.

Homogenates of Dunaliella primolecta, D. salina and D. tertiolecta were assayed for glycollate oxidase and glycollate dehydrogenase. Both D. primolecta and D. salina but not D. tertiolecta showed substantial glycollate-dependent O2-uptake which is characteristic of glycollate oxidase. L-Lactate was an alternative substrate and both glycollate- and L-lactate-dependent O2 uptake were insensitive to 2 mM cyanide. Glycollate dehydrogenase, measured by following the glycollate-dependent reduction of 2,6-dichlorophenolindophenol under aerobic conditions, was present in D. primolecta, D. salina and D. tertiolecta. In the presence of glycollate and D-lactate, rates were additive so both glycollate and D-lactate dehydrogenases are present in the homogenates. Glycollate and D-lactate oxidation were both inhibited by 2 mM cyanide. Organelles released from phototrophically grown cells of D. primolecta were separated by isopycnic centrifugation on sucrose gradients. Glycollate oxidase was present in the peroxisome fraction at an equilibrium density of 1.25 g/cm(3), while the major peak of glycollate dehydrogenase activity was in the mitochondrial fraction at an equilibirium density of 1.22 g/cm(3).

The intracellular localization of glycolate oxidoreductase in Escherichia coli.

Distribution of glycolate oxidoreductase in cell-free extracts of E. coli grown in mineral medium containing sodium glycolate has been studied. The enzyme was found to be largely associated with the cytoplasmic membranes. Homologous antiserum to the membranes inhibited the enzyme activity completely after the solubilization of the intact membranes with Triton X-100. Results on the effect of pronase on glycolate oxidoreductase activity confirmed that part of the enzyme is exposed to the surface of the membrane.

Enumeration of Pseudomonas species and Pseudomonas aeruginosa bacteriophages in domestic sewage.

Domestic sewage in Kuwait is mainly treated by an activated sludge process. Pseudomonas species were enumerated at all steps of sewage treatment. About 98-99% reduction in the number of these bacterial species were found in the treated effluent compared with raw sewage, which indicates a rather efficient removal of Pseudomonas from sewage. Spherical tail-less phages of Pseudomonas aeruginosa were found in all sewage samples. About 25-85% of the total phages encountered with the raw sewage were retained in the treated effluents. Seasonal variations of Pseudomonas spp and P. aeruginosa phages in two treatment stations are reported.

Effect of date extract on growth and spore germination of Bacillus subtilis.

Berhi date extract was studied for its effect on the growth of Bacillus subtilis, Staphylococcus aureus, Salmonella typhi and Pseudomonas aeruginosa. From 80 to 99% inhibition was observed in nutrient broth cultures containing 20% (w/v) date extract. Spore germination of B. subtilis was inhibited completely using various concentrations of date extract. Cell elongation and depression in the cell wall of B. subtilis were seen by scanning electron microscopy as a result of incubation in a growth medium containing dates.

Enumeration of pathogenic bacteria from sewage sludge in Kuwait.

Domestic sewage in Kuwait is mainly treated by an activated sludge process. Sewage sludges at different treatment stages and the digested sludge were studied for their content of pathogenic bacteria. Two Gram-positive cocci and eight Gram-negative bacilli were isolated and enumerated in the sewage sludges and in raw sewage. During March, Aeromonas hydrophila was the dominant bacterium isolated. Serratia liquefaciens in raw sewage and sludge-2, and Salmonella species in digested sludge were dominant during April. Enterobacter aerogenes was dominant in sewage samples in May. Various types of bacteria isolated were tested for their sensitivity to a wide range of antibiotics.

Isolation ofNostoc muscorum cyanophages from a domestic sewage.

TwoNostoc muscorum cyanophages were isolated from a domestic sewage in Kuwait. N-1L cyanophage had a hexagonal head with a long tail, while N-2S cyanophage was a short-tailed virus. N-1L cyanophage was active at 50°C and at acidic pH, compared with N-2S, which was more heat stable and active at pH 7.0. Seasonal variations in the total number of plaque-forming units ofN. muscorum cyanophages were determined for sewage samples collected at each treatment step.

Localization of glycollate dehydrogenase in Dunaliella salina.

Glycollate dehydrogenase of the halotolerant green alga Dunaliella salina, isolated from a brine pond, was found associated with the membrane fraction which exhibited complete photosynthetic activity. Highest enzyme activity was found in cells grown in the presence of 5% NaCl. Any increase in NaCl concentration led to a decrease in specific enzyme activity.

Nitrate-reducing bacteria in Kuwait domestic sewage.

Domestic sewage in Kuwait is mainly treated by an activated-sludge process, where different effluents and sludges are separated. Nitrate reduction in the raw sewage, effluent-1 and effluent-2 were studied. Various enrichments of these sewage samples were effected using 0.2 mg/ml of nitrogen as potassium nitrate and/or 0.5% carbon as glucose. Addition of 0.2 mg/ml nitrate-nitrogen enhanced more ammonia production (117.6 micrograms/ml) in comparison with other enrichments to sewage samples. Nitrate-reducing bacteria were also at a maximum with nitrate enriched sewage samples, especially with effluent-1 (109 X 10(6)/ml). Escherichia coli and Klebsiella pneumoniae were the only two nitrate-reducing bacteria found in all sewage samples tested. Nitrite was unstable during the 7 days incubation period under anaerobic conditions which suggests that nitrates are reduced to ammonia.

Enumeration and identification of pathogenic bacteria from sewage in Kuwait.

Mycobacterium spp. was isolated and enumerated in all sewage samples at different stages of the sewage treatment. Aeromonas hydrophila, Salmonella spp., Shigella dysenteriae and others were isolated from both treated and untreated sewage. Moreover, the serological identification of Salmonella spp. was also done, using antisera specific to their antigenic structures. Counts of bacteria in various sewage sludges and effluents tested showed the efficiency of the activated sludge process in reducing the bacterial number. Seasonal variation in either the number or kind of pathogenic bacteria revealed inconsiderable changes. Almost all species of bacteria tested were found to be resistant to ampicillin.