The Effect of the Intra- and Extracellular Metabolites of Microorganisms Isolated from Various Ecotopes on the Catalase Activity of Staphylococcus aureus ATCC 6538 P

The cell extracts (i.e., intracellular metabolites) and culture liquids (i.e., extracellular metabolites) of microorganisms isolated from various ecotopes were found to inhibit the catalase activity of Staphylococcus aureus ATCC 6538 P, which resulted in a considerable inhibition of the growth of metabolite-treated S. aureus cells by hydrogen peroxide. The inhibitory effect of microbial metabolites on S. aureus catalase can be considered as a mechanism of intercellular interactions responsible for the formation of microbiocenoses.     

The quantitative determination of the DNAse activity in Staphylococcus aureus isolated from monkeys

A new, cheaper and more sensitive method for the quantitative determination of DNAase produced by S. aureus is described. The method permits the determination of DNAase activity in a wider range of titers. The method is based on the detection of the depolymerizing action of staphylococcal nuclease on DNA dyed with ethidium bromide. In this work 22 S. aureus strains isolated from monkeys and 12 strains isolated from humans have been used. The amount of produced by these strains has been determined. The DNAase results of this determination have shown that among S. aureus strains isolated from monkeys and humans the occurrence of strains with both high and low DNAase activity can be observed.     

The effect of salvin on the growth and ultrastructure of Staphylococcus aureus 209P

Antibiotic salvin obtained from Salvia officinalis has been studied for its effect on the growth and ultrastructure of Staphylococcus aureus 209P. The antibiotic in the sub-bacteriostatic concentration considerably elongates the lag-phase (up to 11-12 h) exerting no significant effect on the growth rate of the staphylococcus population as well as it prolongs duration of the exponential phase. The analysis of electronograms of staphylococcus cells subjected to the action of salvin in the concentrations similar to the minimal inhibitory concentration (MIC), has revealed the cell thinning, inhibition and destruction of the division. The introduction of 5MIC antibiotic into the exponentially grown culture made a cell wall considerably thinner, destructing its external layer; the number of lyzed cells sharply increased. The appearance of bodies not described previously with a membrane envelope and ribosomes as well as of mesosomal structures was observed.     

The effect of carbon dioxide on the production of an extracellular nuclease of Staphylococcus aureus

The production of the extracellular nuclease secreted by Staphylococcus aureus (Foggi strain) was studied in a fermentor in an attempt to improve yield and allow large-scale production of the enzyme. In shake flask cultures, 600 units/mL of the enzyme were produced routinely. However, only 450 units/mL of the enzyme at best were obtained in a small-scale fermentor (3 L). The supplementation of the air supply to the fermentor with carbon dioxide [20% (v/v)] increased levels of enzyme in the culture medium to 770 units/mL. Subsequently, this result was reproduced in larger fermentors (10 and 150 L). The possible mechanisms of the effect of carbon dioxide upon the growth of Staphylococcus aureus (Foggi) and the production of the enzyme are discussed.     

Influence of water activity on the production of extracellular enzymes by Staphylococcus aureus

Two enterotoxigenic strains of Staphylococcus aureus were examined for their ability to produce a number of extracellular enzymes at various water activity (alphaw) levels. Supernatant, dialyzed culture media were analyzed for total and relative levels of enzyme activity. With the exception of protease, enzyme activity was greatest in spent media obtained from cultures grown at 0.996 alphaw, the highest level tested. Enzyme activity in spent media from an enterotoxin B-producing strain was generally more sensitive to alphaw reduction than activity from an enterotoxin A-producing strain. Unlike the other enzymes assayed, acid and alkaline protease activities were greatest when the organism was grown at 0.94 alphaw.     

The effect of bacteriolytic preparation lysoamidase on Staphylococcus aureus 209P cells

The effect of the bacteriolytic preparation "Lysoamidase" on Staphylococcus aureus 299 P was studied. The maximum activity of the preparation was observed at pH 8.0 ionic strength 0.01-0.02 M and 50-60 degrees of the incubation medium. The electron microscopic examination revealed that "Lysoamidase" hydrolyzed the cell wall in one or several points with the following osmotic shock and extrusion of the cytoplasm. In an isotonic solution (1 M sucrose) "Lysoamidase" caused protoplast formation.     

Antibacterial activity of isoflavonoids isolated from Erythrina variegata against methicillin-resistant Staphylococcus aureus

AIMS: To screen 16 isoflavonoids isolated from Erythrina variegata (Leguminosae) for their antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). METHODS AND RESULTS: The roots of E. variegata were macerated with acetone. The chloroform-soluble fraction of the residue was subjected to repeated silica gel column chromatography followed by elution with various solvents. Structures of the isolated compounds were determined by extensive spectroscopic studies. Each compound was dissolved in dimethyl sulphoxide and added to agar plates (final concentration 1.56-100 microg ml(-1) and suspensions of MRSA spotted onto the agar plates to determine the minimum inhibitory concentration (MIC). Repeated silica gel chromatography yielded 16 compounds and spectroscopic studies revealed that all were isoflavonoids. Whilst 14 compounds showed antibacterial activity in this concentration range, the MIC values varied significantly among them. Of the active compounds, 3,9-dihydroxy-2,10-di(gamma,gamma-dimethylallyl)-6a,11a-dehydropterocarpan (erycristagallin) and 9-hydroxy-3-methoxy-2-gamma,gamma-dimethylallylpterocarpan (orientanol B) exhibited the highest activity with MIC values of 3.13-6.25 microg ml(-1). CONCLUSIONS: Erycristagallin and orientanol B showed the highest anti-MRSA activity (3.13-6.25 microg ml(-1). SIGNIFICANCE AND IMPACT OF THE STUDY: Erycristagallin and orientanol B could be leading compounds for phytotherapeutic agents against MRSA infections.     

The molecular characteristic of Staphylococcus aureus and Staphylococcus epidermidis strains isolated from clinical sources

The aim of study was the molecular characteristic of S. aureus and S. epidermidis isolates obtained from skin surface, wounds, deep tissues of hospitalized patients and from skin surface of non-hospitalized patients. Genes encoding virulence factors were examined using PCR reaction and specific primers. Genes encoding adhesinsfnbA and cna and gene eta for epidermolytic toxin were mostly present in S. aureus isolates coming from wounds and deep tissues compared to these from skin surface. Gene atlE encoding autolysin of S. epidermidis was detected in all studied isolates, whereas gene icaAB was present in almost all isolates. Comparison of results obtained by PCR and conventional method of the resistance to methicillin estimation showed discrepances suggesting the need for using of both methods in some clinically difficult cases of S. aureus infection.     

The characteristic of Staphylococcus aureus strains isolated from food's samples

The study was carried out of 22 isolates of S. aureus isolated from 7 different incriminated food's samples from foodborne-disease outbreaks. The possibility of these isolates to producing of enterotoxins by commercial test SET-RPLA (Oxoid) was tested. The genotyping of these isolates was done by pulse-filed gel electrophoresis, acc. to Pfaller in own modification. On the basis of the DNA restriction patterns of the 22 isolates--5 strains were singled out, one of these strains--strain V (isolat nr 7) was not relationship to others. It was found that this strain V was one enterotoxin produced. Additionaly, all tested strains, in spite of the strain nr V, were isolated from the 2 or 3 samples of different kinds of foods. In the present study it has been shown too, that several similar colonies should be isolated for farther studies to assess microbiological contamination of the food products properly.     

Influence of water activity on the production of extracellular enzymes by Staphylococcus aureus.

Two enterotoxigenic strains of Staphylococcus aureus were examined for their ability to produce a number of extracellular enzymes at various water activity (alphaw) levels. Supernatant, dialyzed culture media were analyzed for total and relative levels of enzyme activity. With the exception of protease, enzyme activity was greatest in spent media obtained from cultures grown at 0.996 alphaw, the highest level tested. Enzyme activity in spent media from an enterotoxin B-producing strain was generally more sensitive to alphaw reduction than activity from an enterotoxin A-producing strain. Unlike the other enzymes assayed, acid and alkaline protease activities were greatest when the organism was grown at 0.94 alphaw.     

Characterization of hemolytic activity of Staphylococcus aureus strains isolated from bovine mastitic milk

Beta (beta) and delta (delta)-hemolysin of Staphylococcus aureus strains were cultured in vitro in milk lactoserum (whey) prepared from both healthy and mastitis bovine milk. Production of beta- and delta-hemolysins were detected in 12 out of 50 strains studied. The association between N-acetyl-beta-D-glucosaminidase (NAGase) activity, plasmin activity (PL) and trypsin inhibitory capacity (TIC), known as inflammatory indicators for mastitis, and hemolytic activity were also studied. Mastitic milk decreased directly the lytic effect of both beta-and delta-hemolysins of S. aureus on hemolytical blood agar plates. S. aureus in healthy milk samples produced more beta-hemolysin (3 times) and delta-hemolysin (2 times) when compared to S. aureus supernatants in milk from infected quarters. Furthermore, beta- and delta-hemolysis correlated negatively with TIC and NAGase and PL activities. Addition of reduced glutathione (GSH) or beta-mercaptoethanol into the artificial medium enhanced hemolysins activity.     

The effect of the antibiotic AL-87 on the amino acid yield from Staphylococcus aureus 209P cells]

Antibiotic AL-87 has been studied for its effect on the composition of intracellular free amino acids and of amino acids in culture fluid of Staphylococcus aureus 209 P. It is established that the content of amino acids in the culture fluid of S. aureus 209 P is doubled due to antibiotics, while the content of intracellular free amino acids considerably decreases. Spectrum of free amino acids of S. aureus 209 P is presented by 17 basic amino acids. When there is a sub-bacteriostatic concentration of the antibiotic in the medium all free amino acids tend to leave the cells, the content of aspartic acid, serine, threonine and leucine in the medium being increased. Data obtained when studying the effect of antibiotic AL-87 on the composition of free amino acids of Staphylococcus agree well with the previously obtained results from the study of the fatty acid composition of cells. In the light of these data it may be supposed that an increase of the membrane permeability and as a result of it an outlet of amino acids into the medium is one of constituents of the mechanism of antibiotic AL-87 action on Staphylococcus cells.     

The effect of glucose on the expression of extracellular protein genes by Staphylococcus aureus strain V8

The bacteria from overnight cultures (20 h) of S. aureus V8 and exp negative mutant K6812-1, grown, aerobically, in 3% (w/v) Tryptone Soya Broth, at 37 degrees C, were resuspended in fresh medium, in the case of the parent strain +/- 1% (w/v) glucose, without change in bacterial density. During a 6 h incubation period there was an approximate doubling of bacterial density, to the same level, in each case. However, exoprotein production by the mutant was only 20% that of the parent whilst the addition of glucose to the V8 strain resulted in a tenfold reduction in the exoprotein formed. SDS-polyacrylamide gel electrophoresis showed that the exoprotein patterns of both organisms after 6 h incubation were the same as those observed in the overnight cultures whilst the presence of 1% (w/v) extra glucose changed the pattern produced by the parent to one similar to that of the mutant. The results showed that conditions which lead to the rapid formation of glucose catabolites produced an effect consistent with the inhibition of the activity of the exp gene product.     

Bactericidal activity of ethanolic extracts of propolis against Staphylococcus aureus isolated from mastitic cows

Staphylococcus aureus is an important pathogen for both humans and animals, and it has been an ubiquitous etiological agent of bovine mastitis in dairy farms worldwide. Elimination of S. aureus with classic antibiotics is difficult, and the current study aimed to evaluate the efficacy of ethanolic extracts of propolis (EEP) against S. aureus cultivated in complex media or milk. EEP (0–0.5 mg ml⁻¹) decreased growth of S. aureus in BHI media and 1 mg ml⁻¹ was bactericidal against washed cell suspensions (10⁷ CFU ml⁻¹). Propolis extracts also killed S. aureus cells resuspended in milk, but the bactericidal dose was at least 20-fold greater. Cultures that were transferred for at least 60 generations with sub-lethal doses of propolis did not change much their sensibility to EEP. Atomic force microscopy images revealed changes in morphology and cell size of S. aureus cells exposed to EEP (0.5 mg ml⁻¹). Our results indicate that propolis extracts might be effective against mastitis-causing S. aureus strains in vivo, but milk constituents affect the inhibitory activity of propolis. Considering that propolis-resistance appears to be a phenotype not easily selected, the use of EEP combined or not with other antimicrobial agents might be useful for mastitis control in vivo.     

The antibacterial activity of plaunotol against Staphylococcus aureus isolated from the skin of patients with atopic dermatitis.

Plaunotol was tested for possible antibacterial activity against twenty strains of methicillin-resistant Staphylococcus aureus (MRSA) and fourteen strains of methicillin-sensitive S. aureus (MSSA) which had been isolated from the skin of patients with atopic dermatitis under growth-promoting conditions. Plaunotol was effective against all strains tested. The dose of plaunotol for 50% inhibition of growth (ID50) ranged from 2.5 to 16 micrograms/ml for strains of MRSA and from 2.5 to 7.0 micrograms/ml for those of MSSA. These results suggest that plaunotol may be useful in the prevention of infection by MRSA and in skin care for patients with atopic dermatitis.