Despite increasing interest in the bacterium, the methodology for Clostridium difficile recovery has not yet been standardized. Cycloserine–cefoxitin fructose taurocholate (CCFT) has historically been the most used medium for C. difficile isolation from human, animal, environmental, and food samples, and presumptive identification is usually based on colony morphologies. However, CCFT is not totally selective. This study describes the recovery of 24 bacteria species belonging to 10 different genera other than C. difficile, present in the environment and foods of a retirement establishment that were not inhibited in the C. difficile selective medium. These findings provide insight for further environmental and food studies as well as for the isolation of C. difficile on supplemented CCFT.
The aim of this study was to develop simple, rapid and reliable methods for the selective determination of
from ACTIVIA (Danone) yogurts. The methods are based on a modified MRS medium (B-broth), which does not contain inhibitory additives. The sugar source of the medium is maltose, which is metabolized by the bifidobacteria applied in the probiotic products, and not by the normal microflora of yogurt (
). The redox potential of the medium was reduced with cysteine-HCl. Due to its reduced redox potential, the new bouillon is suitable for aerobic cultivation of bifidobacteria, while in agar form it needs anaerobic incubation. In bouillon form (MPN method) the incubation time is only 2 days compared to the 5-day requirement of the classical anaerobic plate counting methods. The B-broth in diluted form was successfully used in a RABIT (Don Whitley) equipment for selective impedimetric determination of bifidobacteria in Danone yogurts. The exact detection time of the
counts in a good quality probiotic yogurt, containing bifidobacteria at a concentration of 10
is not more than 10 to 12 h (in contrast to the 5 days of classical anaerobic plate counting methods).
The resistance of
maize inbred lines and their hybrids to Western Corn Rootworm was investigated
in a 4 × 4 full diallel system. The most tolerant line against WCR
larvae was the inbred line P26. Four maize inbred lines and their 12 normal and
reciprocal crosses were investigated for resistance to Fusarium ssp. and
European Corn Borer under natural conditions in four replications in 1998-2000.
The highest GCA values were found for the inbred lines P26 and P50. Studies
were also made to determine the optimum concentration of imidazolinone in the
selective medium for the detection of resistant cell lines originating from
homozygous genotypes produced by irradiation.
Chickpea (Cicer arietinum) seeds treated with powdered preparation of Gliocladium virens (Gv) alone @ 3 g/kg seed or in combination with vitavax (0.1%) showed colonization of G. virens on seed coat, collar region, plumule and radicle. Microscopic examination revealed that colonization of seed with mycelia and spores of antagonist started 24 h after incubation. Major portion of the seedling was covered with in 48 hrs. Population dynamics of G. virens monitored at different time intervals in spermosphere, rhizosphere and non-rhizosphere region in pathogen infested and non-infested soil using Trichoderma Selective Medium showed that population of G. virens increased initially up to 30 days and then gradually declined. The highest population was observed in spermosphere (7 x 105/g) followed by rhizosphere (6.3 x 104/g), when seeds treated with Gv + vitavax were sown in pathogen infested soil.
Airborne propagules of Fusarium spp. were collected on Fusarium selective medium with Andersen sampler in maize field. Fusarium isolates were identified based on morphological characters and using speciesspecific primersVERT 1/2, PRO 1/2 and SUB 1/2. The PCR analysis confirmed morphological identification of F. verticillioides, F. proliferatum and F. subglutinans. The VERTF 1/2 set of primers were used to discriminate potential fumonisin-producing strains of F. verticillioides, and all F. verticillioides strains scored positive for VERTF 1/2 pair of primers. This is the first study where specific primers were used for the confirmation of morhological determination of the above-mentioned Fusarium species, and selection of fumonisin-producing airborne isolates of F. verticillioides in Hungary.
Cytolethal distending toxins (CDT) represent an emerging toxin family, widely distributed among pathogenic bacteria. The cdtABC genes in E. coli are either part of the genome of prophages, plasmid or pathogenicity island. In order to investigate the stability and the transfer potential of cdt-IV genes cdtB gene was replaced by chloramphenicol (Cm) resistance encoding cat gene in the avian pathogenic E. coli (APEC) strain E250. After consecutive passages in non-selective medium at 37 °C 7.6% (219/2900) of the investigated colonies of E250::cat strain became Cm-sensitive (CmS). To reveal deletion mechanism 177 CmS colonies were investigated for presence of cdtA, cdtC and cdtC associated gene by PCR. One hundred and sixteen colonies of the CmS colonies (65.5%) showed partial or complete deletion in the cdt-IV region. Progressive loss of the upstream genes of the cdt cluster in E250 compared to other CDT-IV producing APEC strains and the fact that all the potential deletion patterns were identified, suggests the presence of an unstable hitherto unknown genomic region. The failure of in vitro transfer of cdt genes into a porcine EPEC E. coli strain suggests that the deletion of cdt-IV flanking genes alone do not promote the spread of cdt-IV.