The consequence of excessive use of macrolides is a high occurrence of mechanisms responsible for resistance to these drugs. Of 97 erythromycinresistant bacterial strains gathered in the Wrocław area in Poland, 60% exhibited very high resistance, and those with the inducible MLS B (macrolidelincosamide-streptogramin B) resistance phenotype predominated. Direct genetic investigation revealed that the erm genes coding for ribosomal methylases are the most frequently occurring erythromycin resistance-determining genes. No genetic resistance determinant was detected in 13% of the erythromycin-resistant strains. The efflux mechanism occurs in strains isolated from the nasopharyngeal cavity twice as often as in those isolated from other material, where the mechanism connected with target site modification predominates. Measurements of radiolabelled antibiotic accumulation inside bacterial cells revealed that in highly resistant strains (MIC > 1024 g/ml), an important factor responsible for the resistance is the permeability barrier at the cell wall level. This would be a hitherto unknown mechanism of resistance to erythromycin in Staphylococcus aureus.
The dinuclear micro-okso vanadium (III) complex compound H(4)V(2)OCl(4)(Ad)(2) synthesized in our laboratory was investigated as a potential cytotoxic agent against yeast cells. The results of these studies could be helpful in the explanation of the mechanism governing the V (III) compound action on yeast as a simple model of eukaryotic cells. The important factors influencing the toxicity of this complex compound are: the stage of the yeast life cycle, the rate of growth and the pH of reaction mixture. The lethal effect was distinctly stronger when the reaction mixture was slightly acidic (pH = 4). In such solutions V(III) mononuclear species with adenine was relatively stable, and during the time of experiment possibly only a slow oxidation process to V(IV) occurred. In the solutions with pH = 7, several hydrolytic, perhaps mixed-valence, polynuclear species were present and their action on the yeast cells was rather weak. The increased lethal activity of this compound in acidic solutions may be useful in specific treatment against cancer cells whose cytoplasm and/or closest surrounding has lower pH value. The next important result was an observation that the killing activity of this compound was enhanced for yeast cells being in log phase. Also these which had a slower rate of growth (possessing some auxotrophic mutations) were more resistant than those growing faster. The extent of yeast mutagenesis caused by the complex compound is negligible, as the number of mutants found in experiments was within the limit of experimental error. These results are promising and the investigated complex can be considered as a potential anti cancer agent.
The objective of the study was to examine, how some physical factors and inoculation techniques affect the growth and sporulation of three insecticidal fungal strains, <em>Hirsutella tompsonii, Paecilomyces</em> sp., and <em>Pandora</em> sp. Although the methods of inoculation, as well as such physical parameters as temperature, the osmotic value of the habitat and UV radiation, exerted an influence on the above-mentioned features of the fungi, their contribution varied from one strain to another. Some of the effects, however (e.g., the production of filamentous structures by <em>Pandora</em>, or the lethal action of glycerol on <em>Pandora</em>), require a close examination.
In Poland, where possibilities for complete microclimate regulation in glasshouses are limited and there is a relatively low degree of automation and computerization, satisfactory biological control of Trialeurodes vaporariorum with Encarsia formosa depends on precise and uniform release of the parasite in the glasshouse, as well as on rapid reaction to increasing pest numbers. This can be achieved by a method, developed in Poland and presented here, of using adults of E. formosa in specially prepared capsules. This paper reports on the principles for using E. formosa in capsules, and on the numbers and frequency of release of the parasite which are appropriate for different crops.
Thrips are among the most dangerous pests of glasshouse cucumbers in Poland. The most frequent species, causing the greatest damage, are Frankliniella occidentalis and Thrips tabaci. The integrated programme of glasshouse cucumber protection against thrips consists of prophylactic treaments, use of the predators Amblyseius barkeri and Neoseiulus cucumeris, and agrotechnical measures.
Amphipatic compounds exhibit an antimicrobial action both on bacteria and fungi. It is caused by a penetrative property of hydrophobic carbon chain of the compuound into a plasma membrane as well as by additional interaction of membrane elements and a hydrophilic amphipathic compound head. Bactericidal and fungicidal activity of this compound strongly depends on chemical environmental factors. In general, microorganisms are not as sensitive in a full medium as in a minimal one and the level of sensitivity rises when the amphipatic compounds are presend in destilled water. Similarly, the sensitivity is stronger in fluid than on solid medium. Our researches revealed however that some aminoacids, although they are complex organic compounds, increase the microbial sensitivity to some tested compound. This efect depends on a microorganism and on a kind of compound. The highest hipersensitivity has been observed against yeast-like fungi when arginine was a cooperating aminoacid. The effect concerns <em><em>Trichosporon</em> but not <em>E.coli</em>, not occurs in relation to SDS, quaternary ammonium salt IA, and bisammonium salts. Certainly the effect exhibit QAS, which have simple composition of hydrophilic „head” consisting only of methyl group, attaching to alkilic chain possessing keton group, build of 14 or 16 carbon atoms.
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