Detection of the tdh and trh genes in Vibrio parahaemolyticus isolates in fish and mussels from Middle Black Sea Coast of Turkey.

AIM: The aim of this study was to demonstrate the occurrence of potential pathogenic Vibrio parahaemolyticus in seafoods using DNA-based techniques in comparison with bacteriological methods. METHODS AND RESULTS: From 120 fresh and processed fish and mussel samples collected from Middle Black Sea, 32 isolates were identified as V. parahaemolyticus by bacteriological methods and confirmed by tl gene-based conventional PCR. Of them, 13 isolates were found positive for only tdh gene, six isolates for only trh gene and 13 isolates for both genes by multiplex PCR. CONCLUSIONS: It is the first report demonstrating the presence of potential pathogenic V. parahaemolyticus isolates from the Black Sea seafoods by PCR detection of tl, trh and tdh genes that was found more rapid than bacteriological methods. SIGNIFICANCE AND IMPACT OF THE STUDY: This study confirmed the previous reports that characterization of potential pathogenic V. parahaemolyticus isolates based on the PCR techniques was reliable and cost-effective. These results suggest that molecular detection methods should be included in Turkish Standards of seafood control in addition to bacteriological methods.

A monoclonal antibody against DNA binding helix of p53 protein.

Three monoclonal antibodies (Mabs) were generated against p53 DNA-binding core domain. When tested by immunoprecipitation, Western blot and immunofluorescence techniques, Mab 9E4, as well as 7D3 and 6B10 reacted with both wild-type and various mutant p53 proteins. The epitopes recognized by Mabs 7D3, 9E4 and 6B10 were located respectively within the amino acid residues 211-220, 281-290 and 291-300 of human p53 protein. The epitope recognized by 9E4 Mab coincides with helix 2, also called p53 DNA binding helix, which allows the direct contact of the protein with its target DNA sequences. This antibody may be useful to study transcription-dependent and transcription-independent activities of wild-type and mutant p53 proteins.

Genomic instability in colorectal cancers in Turkey.

Microsatellite instability in a subset of colorectal cancers from North America, Europe and Japan has been reported. We examined 88 colorectal cancers from Turkish patients. Five different microsatellite loci (1 mono- and 4 dinucleotide repeat regions) were tested. Eight tumors displayed replication errors (RERs) with at least 2 different markers. Right-sided tumors showed significantly higher frequency of microsatellite instability compared with left-sided tumors. The frequency of RER phenotype was slightly higher in tumors occurring in younger (<50 years old) than in older patients (13% vs. 8%), and there was no association between sex and genomic instability. The frequency of genomic instability in our study group was 9%, whereas the reported frequencies in tumors from other countries varied between 12% and 16%.

Protein tyrosine kinase inhibitors block the entries of Listeria monocytogenes and Listeria ivanovii into epithelial cells.

The internalization of Listeria by intestinal epithelial cells is still poorly understood, however it is becoming apparent that microorganisms have developed the ability to interact with host cell receptor molecules to induce their own internalization. In this report we show that inhibition of cell tyrosine phosphorylation by protein tyrosine kinase (PTK) inhibitors blocks L. monocytogenes entry into both finite and immortalized intestinal cell lines. Some differences were observed between the Listeria species. L. monocytogenes entry was inhibited by between 10- to 100-fold by PTK inhibitors competing with the tyrosine residue binding of the kinase as erbstatin or by PTK inhibitors competing with the binding of ATP to the enzyme as genistein and some tyrphostins. On the other hand, L. ivanovii entry was inhibited by erbstatin as observed with L. monocytogenes but poorly by genistein and tyrphostins. The use of these several PTK inhibitors shows that even though both L. monocytogenes and L. ivanovii entered intestinal and other cell lines by stimulating PTK, it seems that L. monocytogenes stimulated a different PTK than L. ivanovii. According to the fact that the number of PTK receptors increases on immortalized cells, the higher L. monocytogenes internalization observed with immortalized cell lines could be related to a higher PTK receptor number on these cells compared to finite cell lines.

Antagonism exerted by an association of a Bacteroides thetaiotaomicron strain and a Fusobacterium necrogenes strain against Clostridium perfringens in gnotobiotic mice and in fecal suspensions incubated in vitro.

Antagonism between an association of Bacteroides thetaiotaomicron and Fusobacterium necrogenes strains and two strains of Clostridium perfringens was evidenced both in vivo in gnotobiotic mice and ex vivo in fecal suspensions incubated for 22 h at 37 degrees C. Several features of this antagonism were similar in and ex vivo. (i) An obligate and continuous synergy between B. thetaiotaomicron and F. necrogenes was required; (ii) the two C. perfringens strains did not respond to the same extent to this antagonism; and (iii) expression of the antagonism was host and diet dependent. Neither diffusible nor soluble inhibitory substances were detectable in feces of gnotobiotic mice, nor could depletion of nutrients be identified as causing antagonism in both in and ex vivo experiments. Our findings support the hypothesis that a reversible bacteriostasis induced by the inhibitory strains acting together continuously, and hindering the target strain from utilizing available nutrients, was responsible for this antagonism.

Translocation of strictly anaerobic bacteria from the intestinal tract to the mesenteric lymph nodes in gnotobiotic rodents.

Viable cells of some strictly anaerobic strains belonging to Bacteroides, Clostridium and Fusobacterium genera were present in mesenteric lymph nodes of gnotobiotic rodents harbouring these strains. Various parameters were found to affect the incidence of translocation, including the caecal population level, the length of association with the host and the nature of the strains and host.

Antagonistic effect exerted by three strictly anaerobic strains against various strains of Clostridium perfringens in gnotobiotic rodent intestines.

Our purpose was to study bacterial antagonism between a limited number of strictly anaerobic strains and Clostridium perfringens in the intestinal tract of gnotobiotic rodents. Gnotobiotic mice harboring a Bacteroides thetaiotaomicron, a Fusobacterium necrogenes, and a Clostridium sp. strain were protected against pathogenic B, C, and D C. perfringens serotypes. A drastic antagonistic effect of this three-strain association was also observed against a nonpathogenic C. perfringens serotype A (CpA). It was less efficient in gnotobiotic rats than in mice and less efficient in gnotobiotic mice fed an autoclaved diet than in mice fed the same diet sterilized by irradiation. No diffusible inhibitory substances against CpA were detected in feces of gnotobiotic mice harboring the three antagonistic strains, and no nutrient depletion was demonstrated in filtrates prepared from 10-fold diluted feces of these mice. In vitro mixed cultures of the three antagonistic strains failed to inhibit growth of CpA, whereas CpA did not multiply in a 10-fold diluted feces from gnotobiotic mice. A reverse correlation between the initial number of antagonistic strains and the division number of CpA was determined using serially diluted fecal suspensions. Thus, large numbers of viable cells of both antagonistic strains were required to inhibit the target strain in fecal suspensions as was also found in gnotobiotic mice intestines. However, no diffusible inhibitory substance was detectable nor could depletion of growth factors be identified as causing antagonism. Whatever factors that may be responsible for antagonism were found to be influenced by the host and its diet.