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L Krizková

Publications and source records attributed to L Krizková.

At least 19 recordsLinked to original sources
PubMed2006

Identification and characterization of enterococci from bryndza cheese.

AIMS: To identify enterococci isolated from sheep milk cheese--bryndza, and to compare differences in the composition of enterococcal microflora affected by the season, and to evaluate the potential presence of vancomycin resistance and virulence determinants. METHODS AND RESULTS: Bacterial strains were isolated during analysis of bryndza cheese and identified on the genus and species level by phenotypic methods and with commercial biochemical sets. The identification of the species, Enterococcus faecium, Ent. durans and Ent. faecalis, was confirmed by PCR using species-specific primers for ddl genes. PCR was also used for assessment of presence of vanA and vanB genes and virulence determinants gelE, agg and cytolysin genes namely: cylL(L), cylL(S), cylM, cylB and cylA. Among 308 Enterococcus sp. strains, 177 isolates were proved to be Ent. faecium, 59 to be Ent. durans and 41 to be Ent. faecalis. Vancomycin resistance genes vanA and vanB were not detected. Agar plate testing confirmed their absence. Gene gelE, however, was found in 20 Ent. faecalis isolates, but only 13 of them showed gelatinase-positive phenotype. Seven isolates had five cytolysin genes, but none of the isolates exhibited a positive haemolytic phenotype. Four isolates possessed the agg gene. The prevalence of Ent. faecium species was highest in samples from the winter season harvest. CONCLUSIONS: Ent. faecium is the dominant enterococcal species in bryndza cheese and the most prevalent in the winter season product. None of the Enterococcus sp. strains was proved to have vanA or vanB genes and the vancomycin resistance. SIGNIFICANCE AND IMPACT OF THE STUDY: To our knowledge, this is the first report of enterococcal microflora in bryndza cheese and its evaluation for the presence of vanA and vanB genes as well as virulence determinants.

Animals↗
PubMed2004

Synergic activity of selenium and probiotic bacterium Enterococcus faecium M-74 against selected mutagens in Salmonella assay.

Concentrated extracts of MRS (De Man-Rogosa-Sharpe) media in which probiotic bacterium Enterococcus faecium strain M-74 was grown exerted different antimutagenic activity against ofloxacin-, N-methyl, N'-nitro-N-nitrosoguanidine- and sodium 5-nitro-2-furylacrylate-induced mutagenicity in Salmonella typhimurium assay depending on the presence (+Se) or absence of disodium selenite pentahydrate (-Se). The antimutagenicity of MRS(+Se) extract was higher than that of MRS(-Se) extract. Selenium enhanced also the antimutagenic effect of both live and killed cells of E. faecium M-74, respectively. The live bacteria decreased the mutagenicity of selected substances more than killed cells. Synergic activity of selenium with the bacterium was also manifested.

Antimutagenic Agents↗
PubMed2004

Triterpenoid cynarasaponins from Cynara cardunculus L. reduce chemically induced mutagenesis in vitro.

Saponins, steroid or triterpene glycosides, are known to have a broad spectrum of biological and pharmacological activities. Three different triterpenoid saponins, marked here as 1s, 2s and 3s, from involucral bracts of Cynara cardunculus L. were isolated and their antimutagenic effect was assessed. Using spectrophotometric method it was shown that all three substances, 1s, 2s and 3s, possess very good absorptive capability. The antimutagenic effect of these substances was estimated against acridine orange (AO)- and ofloxacin-induced damage of chloroplast DNA in Euglena gracilis assay. These cynarasaponins were experimentally confirmed to exhibit different, statistically significant activity in reducing damage of chloroplast DNA of the flagellate E. gracilis induced by AO and ofloxacin (p(t) < 0.05-0.01). Our findings suggest that the antimutagenic effect of 1s, 2s and 3s against AO-induced chloroplast DNA impairment could be a result of their absorptive capacity. As far as ofloxacin is concerned, a possible mechanism of the reduction of the chloroplast DNA lesion was not elucidated so far. To our knowledge, these data demonstrate for the first time the antimutagnic activity of saponins isolated from involucral bracts of C. cardunculus exerted through different mode of action.

Acridine Orange↗
PubMed2001

Antioxidative and antimutagenic activity of yeast cell wall mannans in vitro.

Antioxidative and antimutagenic effect of yeast cell wall mannans, in particular, extracellular glucomannan (EC-GM) and glucomannan (GM-C.u.) both from Candida utilis, mannan from Saccharomyces cerevisiae (M-S.c.) and mannan from Candida albicans (M-C.a.) was evaluated. Luminol-dependent photochemical method using trolox as a standard showed that EC-GM, GM-C.u., M-S.c. and M-C.a. have relatively good antioxidative properties. EC-GM exhibited the highest antioxidative activity, followed by GM-C.u. and M-S.c. M-C.a. showed the least antioxidative activity. These mannans were experimentally confirmed to exhibit different, statistically significant antimutagenic activity in reducing damage of chloroplast DNA of the flagellate Euglena gracilis induced by ofloxacin and acridine orange (AO). We suggest that the antimutagenic effect of EC-GM, GM-C.u., M-S.c. and M-C.a. against ofloxacin is based on their ability to scavenge reactive oxygen radicals. With AO, the reduction of the chloroplast DNA lession could be a result of the absorptive capacity of the mannans. The important characteristics of mannans isolated from the yeast cell walls, such as good water solubility, relatively small molecular weight (15-30kDa), and antimutagenic effect exerted through different mode of action, appear to be a promising features for their prospective use as a natural protective (antimutagenic) agents.

Acridine Orange↗
PubMed2001

Phenolic acids reduce the genotoxicity of acridine orange and ofloxacin in Salmonella typhimurium.

Naturally occurring plant phenolics, p-coumaric acid (PA), caffeic acid (CA), ferulic acid (FA) and gentisic acid (GA) (25-100 nmol/L) had protective effects on acridine orange (AO; 216 mumol/L)- and ofloxacin (3 mumol/L)-induced genotoxicity in Salmonella typhimurium. FA, GA and CA exhibited a significant concentration-dependent protective effect against the genotoxicity of AO and ofloxacin, with the exception of PA, which at all concentrations tested abolished the AO and ofloxacin genotoxicity. UV spectrophotometric measurements showed the interaction of PA, FA, GA and CA with AO but not with ofloxacin; this interaction is obviously responsible for the reduction of AO-induced S. typhimurium mutagenicity. In the case of ofloxacin the antimutagenic effect of PA, FA, GA and CA is assumed to be a result of their ability to scavenge reactive oxygen species (ROS) produced by ofloxacin.

Acridine Orange↗
PubMed2000

Phenolic acids inhibit chloroplast mutagenesis in Euglena gracilis.

The mutagenicity (bleaching activity) of ofloxacin (43 microM) and acridine orange (AO) (13.5 microM) in Euglena gracilis is inhibited by plant phenolics. Caffeic acid (CA), p-coumaric acid (PCA), ferulic acid (FA) and gentisic acid (GA) (25, 50, 100 and 250 microM) exhibited a significant concentration-dependent inhibitory effect against ofloxacin-induced mutagenicity, which was very effectively eliminated by the highest concentration of all four of those phenolic acids. The mutagenicity of AO was also significantly reduced in the presence of CA, PCA and FA (25, 50, 100 and 250 microM). However, GA exhibited no significant activity, even at the concentration of 250 microM. Based on the UV spectrophotometric measurements, we suggest that the antimutagenic effect of CA, PCA, FA and GA resulted from the scavenging of reactive oxygen species (ROS) produced by ofloxacin. On the other hand, the reduction of AO-induced mutagenicity correlates with the binding capabilities of CA, PCA and FA, with the exception of GA.

Acridine Orange↗
PubMed1999

Antimutagenicity of a suberin extract from Quercus suber cork.

The possible protective effect of a suberin extract from Quercus suber cork on acridine orange (AO)-, ofloxacin- and UV radiation-induced mutagenicity (bleaching activity) in Euglena gracilis was examined. To our knowledge, the present results are the first attempt to analyse suberin in relation to mutagenicity of some chemicals. Suberin exhibits a significant dose-dependent protective effect against AO-induced mutagenicity and the concentration of 500 micrograms/ml completely eliminates the Euglena-bleaching activity of AO. The mutagenicity of ofloxacin is also significantly reduced in the presence of suberin (125, 250 and 500 micrograms/ml). However, the moderate protective effect of suberin on UV radiation-induced mutagenicity was observed only at concentrations 500 and 1000 micrograms/ml. Our data shows that suberin extract from Q. suber cork possess antimutagenic properties and can be included in the group of natural antimutagens acting in a desmutagenic manner.

Acridine Orange↗
PubMed1998

The effect of flavonoids on ofloxacin-induced mutagenicity in Euglena gracilis.

The antimutagenicity of 14 naturally occurring flavonoids (20 mumol/l) on ofloxacin (43 mumol/l and 86 mumol/l)-induced bleaching (mutagenicity) was studied in Euglena gracilis. The flavonoids chrysin, techtochrysin, chrysin-5-methylether galangin, galangin-5-methylether, pinocembrin and pinobanksin possess considerable antimutagenic properties against ofloxacin-induced bleaching of E. gracilis. Apigenin and isalpinin had only weak antimutagenic potency. Pinobanksin-5-methylether and pinobanksin-3-acetate showed very weak or no antimutagenic effect. However, kempferol, quercetin-3-methylether and quercetin-3,3'-dimethylether showed co-mutagenic or no antimutagenic effect depending on the concentration of ofloxacin. Two possible modes of action of the flavonoids on ofloxacin-induced bleaching of E. gracilis are discussed.

Animals↗
PubMed1996

Antimutagens reduce ofloxacin-induced bleaching in Euglena gracilis.

The genotoxic effect of ofloxacin was significantly decreased by standard antimutagens (sodium selenite, ascorbic acid, butylated hydroxyanisole and butylated hydroxytoluene) in the unicellular flagellate Euglena gracilis. The antiofloxacin activity of sodium selenite was also documented by a bacterial test in which the repair-proficient strain Salmonella typhimurium TA102 was used.

Animals↗
PubMed1992

Expression of Japanese quail ovalbumin in Saccharomyces cerevisiae.

A cDNA sequence coding for Japanese quail ovalbumin was used for the construction of expression plasmid under the ADH1 promoter of the yeast shuttle vector pVT101-U. The resulting recombinant expression vector pJK2 was used for the transformation of Saccharomyces cerevisiae. Expression of quail ovalbumin in yeast cells was demonstrated by Western blotting followed by immunochemical detection.

Animals↗
PubMed1991

A rapid and simple method for DNA preparation from Candida utilis.

A method for the extraction of genomic DNA from the industrial yeast Candida utilis is described. The method is rapid, simple and produces DNA that is sufficiently pure for restriction analysis and should be suitable for Southern blotting and the construction of gene libraries.

Candida↗
PubMed1979

Nematocide effect of entomophilic and entomophagous fungi.

Study of nematocide effect of 48 species of entomophilic and entomophagous fungi from the class Fungi imperfecti against Panagrellus redivivus and Rhabditis oxycerca nematodes revealed a high frequency of fungi with nematocide effect. A close correlation between these two effects was disclosed by measuring the intensity of the nematocide and insecticide effect of fungal extracts.

Animals↗
PubMed1976

Incidence of antiprotozoal and antivermal antibiotics in fungi, V Class Fungi Imperfecti Collected in the Vietnamese Democratic Republic.

From soil samples collected in the jungles of Ninh Binh Province of the Vietnamese Democratic Republic, 97 isolates belonging to 54 species of Fungi imperfecti were obtained and screened for the production of antibiotics. The isolates were identified as belonging to the orders Melanconiales, Moniliales, Sphaeropsidales and Mycelia sterilia. In the species studied a very high incidence of antiprotozoal activities were observed.

Animals↗