Acta microbiologica Polonica最新文献

Helicobacter pylori resistance to antimicrobial agents is an important factor compromising the efficacy of treatment. Therefore the aims of our study were: to determine the prevalence of H. pylori resistance to clarithromycin, metronidazole, amoxycillin and tetracycline in children prior to eradication therapy, to compare different methods of susceptibility testing and to detect mutations responsible for clarithromycin resistance. During 1996-2000, 259 H. pylori strains were isolated from antral gastric biopsies. Susceptibility to antimicrobials was determined by the agar dilution method and the Etest. Mutations in the 23S rRNA gene associated with clarithromycin resistance were analysed by PCR-RFLP and direct sequencing. Overall, ninety-six strains (37%) were resistant to metronidazole, 50 strains (19.3%) were resistant to clarithromycin, and 20 strains (7.7%) were simultaneously resistant to both drugs. All cultured isolates were sensitive to amoxycillin and only one isolate (0.4%) was resistant to tetracycline. The agar dilution method and the Etest showed a perfect category correlation for clarithromycin and 4% discrepancies for metronidazole. Primary resistance to clarithromycin was mainly associated with an A2143G mutation in the 23S rRNA gene of H. pylori. The study highlights the high prevalence of H. pylori primary resistance to clarithromycin in Polish children, which implies a need for pretreatment susceptibility testing.

Antibacterial and antifungal activity of 2-trifluoromethyl- and 2-pentafluoroethylbenzimidazoles, including a number of newly obtained derivatives, were examined by diffusion method (inhibition area diameter in solid agar medium) and minimum inhibitory concentration (MIC, in liquid and agar medium). Some of the derivatives tested affected fungal colony morphology and exerted genotoxic effects in bacteria. Of the tested compounds, 5,6-dichlorosubstituted derivatives appeared the most active against the majority of microorganisms used.

The fatty acid composition from Fusarium oxysporum B1, a fungal epiphyte from algal crusts, was determined. The most prominent fatty acids found in the mycelium were 18:1 omega9c, 16:0 and 18:0. These compounds amounted 47% of total fatty acids, whereas remaining fatty acids identified, including beta-hydroxylated, iso-branched, diunsaturated and odd-numbered derivatives were present in minor amounts.

Molecular markers such as: lacZ (b-galactosidase), xylE (catechol 2,3-dioxygenase), lux (bacterial luciferase), luc (insect luciferase), phoA (alkaline phosphatase), gusA and gurA (beta-glucuronidase), gfp (green fluorescent protein), bla (beta-lactamase) and other antibiotic resistance markers, heavy metals resistance genes are commonly used in environmental microorganisms research (Errampaii et al., 1998; Kohler et al., 1999). Most of these markers require one or more substrates, complex media and/or expensive equipment for detection. The gfp gene is widely used as a marker because of its very useful properties such as high stability, minimal toxicity, non-invasive detection and the ability to generate the green light without addition of external cofactors and without application of expensive equipment. Various applications of that reporter gene were showed starting from monitoring of microorganism's survival in complex biological systems such as activated sludge to biodegradation of chemical compounds in soil. GFP allowed the detection, determination of spatial location and enumeration of bacterial cells from diverse environmental samples such as biofilm and water. The gfp as a biomarker was very useful in monitoring of gene expression and protein localisation in bacterial cells, too. The techniques with using gfp marker promise to supply a better understanding of environmental processes. It can make possible to use that knowledge in designing more effective and more efficient methods of biodegradation of toxic compounds from different environments.

We report that the intraperitoneal injection of Clostridium perfringens alpha-toxin into mice induces ascites. This phenomenon was monitored by measuring fluid volume and analyzing hematologic data. The mouse toxicity test provides a simple and useful model for examining C. perfringens alpha-toxin-induced vascular permeability.

Statistically designed experimental strategy has been performed in order to evaluate and optimize nutritional and environmental parameters that affect ferrous ion oxidation rate in Acidithiobacillus ferrooxidans ATCC 23270. Plackett-Burman design was carried out to evaluate efficiently the biological significance of 10 culture conditions influencing ferrous-ion oxidation rate of A. ferrooxidans grown for 5 days in shake-flask batch mode on the newly modified 9-K media. Among ten fermentation factors examined, the most significant variables influencing ferrous-ion oxidation rate were statistically elucidated to be pH and calcium nitrate as positive contributors, whereas trace metals solution and potassium chloride were the most significant negative contributors. The optimal levels of the most significant three nutritional factors were further predicted from a polynomial model created from the data obtained from three level factorial design, a Box-Behnken design. Predicted optimal ferrous-ion oxidation rate Q(Fe2+) was recorded to be 0.148 (g Fe2+/l/hr). On verifying the predicted value, an experiment was performed under optimal predicted conditions and showed an actual experimental Q(Fe2+) of 0.152 g/l/hr, which was 2.7% over the predicted value. Our optimized medium formula gave overall five folds increase in ferrous-ion oxidation rates over the previously published data of standard 9-K medium on batch culture of A. ferrooxidans ATCC 23270 with higher mu(max) (hr(-1)) of 0.177 which was achieved within 75 h incubation in shake-flask culture.

Mutants resistant to phenylalanine analogs (L-tyrosine, p-fluoro-D, L-phenylalanine (PFP) and trans-cinnamic acid) were isolated from a wild type strain of Rhodotorula glutinis A-97 by mutagenic treatment with gamma radiation and screened for phenylalanine ammonia lyase (PAL) production. One such mutant, gammaT11 (resistant to L-tyrosine), exhibited four times the PAL activity of the parent wild strain A-97. Mutant isolate gammaTFP5.6 which was selected as L-tyrosine and PFP resistant isolate, produced inducible PAL activity at levels 5.94-fold higher than the wild-type A-97 and 2.66-fold higher than its parent mutant isolate gammaT5 which was resistant to L-tyrosine. The mutant isolate gammaTC5d which was resistant to L-tyrosine and trans-cinnamic acid, exhibited 3.48 and 1.56-fold increase in PAL activity compared to the parent wild strain A-97 and its parent mutant isolate gammaT5, respectively. Different media have been examined for the induction of PAL.

Different crude extracts of Nigella sativa were tested for antimicrobial effectiveness against different bacterial isolates. These isolates comprised 16 gramnegative and 6 grampositive representatives. They showed multiple resistance against antibiotics, specially the gramnegative ones. Crude extracts of Nigella saliva showed a promising effect against some of the test organisms. The most effective extracts were the crude alkaloid and water extracts. Gramnegative isolates were affected more than the grampositive ones.

Immunogenic activity of herpes simplex type 1 temperature sensitive mutant's (ts HSV-1 mutant) proteins was tested in two systems: monovalent and polyvalent with other attenuated virus strains (measles and mumps). The guinea pigs were used as animal model. In monovalent system the humoral response in animals infected with ts HSV-1 mutant (1 or 2 doses) was studied and compared to results received for HSV-1 native strain. In polyvalent system the immunological response induced by ts HSV-1 mutant in the presence of RNA virus strains was tested.

Laboratory experiments were used to determine the effects of antibiotics, organic C and CaCO3 amendments of sterile reinoculated soil on S0 oxidation by bacteria and fungi. The rate of S0 oxidation in soil with nystatin added was higher than in soil amended with penicillin + streptomycin. This tells us that bacteria were more efficient than fungi in the S0 oxidation process. It was demonstrated that neutrophilic chemolithotrophs were more efficient in this process than heterotrophs. Glucose introduced to the soil had a negative effect and CaCO3 had a positive effect on S0 oxidation. In soil enriched with glucose the number of chemolithotrophs was very low in comparison with extremely numerous heterotrophic bacteria and fungi. It suggests that the role of heterotrophs in S0 oxidation could be important in habitats rich in organic C, e.g. rhizosphere. In soil containing S0, qualitative changes of fungal communities to genera with higher S0 oxidation ability was also noted. In the presented paper, after comparison of the own results with the data of others concerning the natural soils, the role of various microbial groups in S0 oxidation process in soils is discussed.