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Antimicrobial resistance and genetic profiling of Escherichia coli from a commercial beef packing plant.

The objective of this study was to investigate the extent of antimicrobial resistance and to genetically characterize resistant Escherichia coli recovered from a commercial beef packing plant. E. coli isolates were recovered by a hydrophobic grid membrane filtration method by direct plating on SD-39 medium. A total of 284 isolates comprising 71, 36, 55, 52, and 70 isolates from animal hides, washed carcasses, conveyers, beef trimmings, and ground beef, respectively, were analyzed. The susceptibility of E. coli isolates to 15 antimicrobial agents was evaluated with an automated broth microdilution system, and the genetic characterization of these isolates was performed by the random amplified polymorphic DNA (RAPD) method. Of the 284 E. coli isolates, 56% were sensitive to all 15 antimicrobial agents. Resistance to tetracycline, ampicillin, and streptomycin was observed in 38, 9, and 6% of the isolates, respectively. Resistance to one or more antimicrobial agents was observed in 51% of the E. coli isolates recovered from the hides but in only 25% of the E. coli from the washed carcasses. Resistance to one or more antimicrobial agents was observed in 49, 50, and 37% of the isolates recovered from conveyers, beef trimmings, and ground beef, respectively. The RAPD pattern data showed that the majority of resistant E. coli isolates were genetically diverse. Only a few RAPD types of resistant strains were shared among various sample sources. The results of this study suggest that antimicrobial-resistant E. coli isolates were prevalent during all stages of commercial beef processing and that considerably higher numbers of resistant E. coli were present on conveyers, beef trimmings, and ground beef than on dressed carcasses. This stresses the need for improving hygienic conditions during all stages of commercial beef processing and meatpacking to avoid the risks of transfer of antimicrobial-resistant bacteria to humans.

Animals↗

Gene expression profiling, genetic networks, and cellular states: an integrating concept for tumorigenesis and drug discovery.

Genome-wide expression monitoring, a novel tool of functional genomics, is currently used mainly to identify groups of coregulated genes and to discover genes expressed differentially in distinct situations that could serve as drug targets. This descriptive approach. however, fails to extract "distributed" information embedded in the genomic regulatory network and manifested in distinct gene activation profiles. A model based on the formalism of boolean genetic networks in which cellular states are represented by attractors in a discrete dynamic system can serve as a conceptual framework for an integrative interpretation of gene expression profiles. Such a global (genome-wide) view of "gene function" in the regulation of the dynamic relationship between proliferation, differentiation, and apoptosis can provide new insights into cellular homeostasis and the origins of neoplasia. Implications for a rational approach to the identification of new drug targets for cancer treatment are discussed.

Biotechnology↗

Genetic profiling defines the xenobiotic gene network controlled by the nuclear receptor pregnane X receptor.

The orphan nuclear receptor pregnane X receptor (PXR) is essential for the transcriptional regulation of hepatic xenobiotic enzymes including the cytochrome 3A isoenzymes. These enzymes are central to the catabolism and clearance of most endogenous sterol metabolites (endobiotics) and a vast diversity of foreign compounds (xenobiotics) including pharmaceuticals, pesticides, and toxins encountered through diet and environmental exposure. To explore a broader role of PXR in the mammalian xenobiotic response, we have conducted a unique microarray gene profiling analysis on liver samples derived from PXR knockout mice and mice expressing a constitutively active variant, VP-hPXR. This genetically guided expression analysis enables targeting and restriction of the PXR response to liver, and is devoid of side effects resulting from drugs and their metabolites. As with pharmacological studies, receptor-dependent genes include both phase I and phase II metabolic enzymes, as well as certain drug and anion transporters as principal PXR targets. Moreover, comparative analysis of data from both genetic and pharmacological arrays reveals a core network that represents a genetic description of the xenobiotic response.

Animals↗

Diagnosis of Alzheimer's disease: defining genetic profiles (genotype vs phenotype).

The early identification of Alzheimer's disease (AD) requires a multifactorial diagnostic approach. Components of a comprehensive assessment include a clinical examination, neuropsychological and psychometric evaluations, biochemical tests, cardiovascular and radiological examinations, neuroimaging, brain bioelectrical activity mapping, an evaluation of brain hemodynamics, and assessment of biological markers. Genetic testing should be incorporated into the diagnostic protocol only for research purposes and risk evaluation. The genetic characterization of familial AD genotypes (FAD-21, FAD-14, FAD-1, FAD-19, APP-21m) can help define the phenotypic profiles of AD clinical subtypes. The correlation of genotypic and phenotypic profiles might have a predictive value in terms of AD diagnosis and therapeutic responses to particular drugs. However, available genetic markers (APP-21m, APO-E) are not yet conclusive for diagnostic purposes. In contrast, AD-related Apo-E genotypes appear to correlate with defined AD phenotypes. The presence of an Apo-E4 allele seems to represent an important risk factor for dementia.

Alzheimer Disease↗

The STR-based genetic profile of the population from Corsica island (France).

Short tandem repeats (STR) at loci HumFES/FPS, HumVWA, HumCSF1PO, HumTH01, HumFXIIIA01, HumTPOX, HumCD4, D3S1358 are markers of choice for population genetics and validated systems for forensic use. In this report, we analysed their allele frequency distribution in a sample of native blood donors from the two departments of Corsica island (France). Deviations from the Hardy-Weinberg rule and heterozygosity values consistently suggested a spatial differentiation of allele and genotype frequencies across the island. Pairwise comparisons showed that Corsican gene pool presents a high level of heterogeneity between departments and substantially differs from that of neighbouring and historically-related populations. The results suggest the use of local databases to calculate a priori statistics in human identity testing.

Alleles↗

Unique genetic profile of hereditary hemochromatosis in Russians: high frequency of C282Y mutation in population, but not in patients.

Hereditary hemochromatosis (HH) is a common cause of primary iron overload induced by genetic impairment of iron metabolism. More than 80% of HH patients in populations of European origin are homozygotes for a single mutation C282Y, or compound heterozygotes for C282Y and H63D mutations in the HFE gene. However, in the majority of Asian, African, Australasian, and Amerindian populations, frequencies of C282Y are close to zero. Data on the prevalence of HFE mutations in Russian population and in Russian patients with HH are very limited. In this work, we determined frequencies of C282Y and H63D in ethnical Russians living in the Central European region of Russia. Furthermore, we tested whether homozygocity for C282Y is the major cause of HH in Russians. We found that, in the Russian population, the frequency of C282Y mutation in the HFE gene is relatively high and corresponds to mean European levels. However, in contrast to the majority of European populations, homozygocity for C282Y is found only in a small proportion (5%) of patients with biochemical and clinical signs of HH. These data suggest that either the penetrance of C282Y in Russia is lower than in Western countries, or that a more frequent non-HFE dependent mechanism of primary iron overload dominates in Russian population.

Gene Frequency↗

Genetic profile, PTEN mutation and therapeutic role of PTEN in glioblastomas.

New therapeutic strategies are needed to improve survival in glioblastoma (GBM) the most malignant astrocytic tumor. We evaluated: a) the genetic status of 22 GBMs by comparative genomic hybridization (CGH); b) the specific role of mutation and/or homozygous deletion of PTEN in the genesis of GBM; and c) the possible therapeutic role of PTEN against GBM, in vitro. CGH demonstrated that the most frequent region of gain was at chromosome 7p, whereas the most frequent losses occurred at chromosomes 10q and 13q. Losses at chromosome 10 were found in 36% of patients, and PTEN was mutated in 27% of the 22 GBMs, including 4 point mutations and 2 homozygous deletions. The possible therapeutic role of PTEN in GBM was also studied in a system based on retroviral infection of the GBM cell line A172, homozygously deleted at the PTEN locus. A172 growth and proliferation rate were reduced by 50% after PTEN transduction. Moreover, we showed that inhibition of cell growth occurred through the PI3K/Akt/p27 pathway. Our findings suggest that PTEN participates in the genesis of GBM, and might be further studied as a candidate therapeutic agent in other testing systems.

Cell Division↗

Genetic profiling of granular cell myoblastoma.

Granular cell tumor (GCT), or granular cell myoblastoma, is a relatively uncommon lesion of the soft tissues. It can occur in any organ, and the tongue is more often affected. GCT has unknown etiology, uncertain histogenesis, and a not always benign nature. Benign myoblastomas are the great majority, but rare malignant lesions have been reported. To have more information regarding the genetic events involved in GCT, the authors decided to perform an expression profile. A sample was derived from a surgically resected GCT of the tongue. RNA extracted from normal tongue (mucosa plus muscle) was used as control. By using DNA microarrays containing 19,200 genes, the authors identified several genes for which expression was significantly up- or down-regulated. The differentially expressed genes cover a broad range of functional activities: (1) signal transduction, (2) cell cycle regulation, and (3) cytoskeleton organization. It was also possible to detect some genes whose function is unknown. The data reported are, to the authors' knowledge, the first genetic portrait of GCT. Mutations in some of the described genes are related to neural alterations and mental diseases, and this fact supports the idea of a neural origin of myoblastoma. Several markers have been identified that will help in identifying the biological behavior (when malignant lesions will be described), as well as the gene whose products could be potentially disease-specific targets for therapy.

Cell Cycle Proteins↗

Impact of genetic profiles on experimental studies: outbred versus wild rats.

Most rats used in toxicological or pharmacological research are obtained from outbred stocks. It is assumed that they are characterized by a high degree of genetic heterogeneity, reflecting that of the human population. However, most outbred stocks available have been kept as restricted colonies over a long period of time, decreasing their genetic variability. Since it is unclear to what extent genetic variability can be expected from an outbred stock, we analyzed 20 rats from each of two outbred stocks, Crl:WIST and Rj:SD, and compared them with 17 unrelated wild rats, using 90 randomly selected microsatellite markers, located on 20 autosomes and chromosome X. Up to 8 alleles per locus were found in wild rats compared with the maximum of 4 alleles in Crl:WIST and 3 alleles in Rj:SD rats. Therefore, significant differences were observed in the mean of number of alleles between Crl:WIST (2.3 +/- 0.6) and Rj:SD (1.7 +/- 0.6), as well as between both outbred stocks and wild rats (4.6 +/- 1.5). The lowest heterozygosity was in Rj:SD (0.27 +/- 0.19), which was significantly different from Crl: WIST (0.41 +/- 0.19) and wild rats (0.35 +/- 0.21). Our findings clearly show loss of alleles in both outbred stocks compared with wild rats and demonstrate that the designation "outbred stock" is no guarantee for genetic and phenotypic variability. This fact will have a significant impact on generation of new outbred stocks as well as performing multistrain experiments and thereby it may reduce false-positive and false-negative results in toxicological and pharmacological research in the future.

Animals↗

Prognostic stratification of patients with anaplastic gliomas according to genetic profile.

BACKGROUND: There is a need to improve the current, controversial, and poorly reproducible classification of anaplastic gliomas, which represent a highly heterogeneous entity in terms of survival. METHODS: The impact of the most common genetic alterations on survival was investigated based on 156 anaplastic gliomas: Among the patients who were included, the gender ratio was 1.32, the median age was 45.5 years (range, 20-83 years), and the median Karnofsky performance status was 70 (range, 40-100). Genetic analysis included a search for loss of heterozygosity (LOH) on chromosomes 1p and 19q; amplification of chromosomes 9p and 10q and of the epidermal growth factor receptor (EGFR), cyclin-dependent kinase 4 (CDK4) and mouse double-minute (MDM2) genes; and p53 expression. RESULTS: The median survival was 33.5 months, and the median progression-free survival was 15.8 months. In a univariate analysis, LOH on 1p and 19q was correlated with longer survival, whereas p53 expression, LOH on 9p, LOH on 10q, amplified EGFR, and deleted CDKN2A were correlated with shorter survival. LOH on 1p and 19q were associated with oligodendrogliomas, LOH on 10q was related to EGFR amplification, and LOH on 1p and 19q was mutually exclusive with EGFR amplification and LOH on 10q. In a multivariate analysis, the significant prognostic factors were age, histology, LOH on 1p and 19q, and P16/CDKN2A deletion. Recursive partitioning analysis (RPA) divided the whole group hierarchically into 3 distinct prognostic subgroups: Group A with 1p19q codeletion (median survival, 98 months), Group B with EGFR amplification (median survival, 17 months), and Group CC (median survival, 31 months), providing a basis for a genetically based prognostic subclassification for patients with Grade III gliomas. CONCLUSIONS: The search for 1p19q codeletion and EGFR receptor amplification provides a simple, clinically relevant prognostic subclassification of grade III gliomas.

Adult↗

Automatic detection and genetic profiling of disseminated neuroblastoma cells.

BACKGROUND: Rare tumor cells circulating in the hematopoietic system can escape identification. On the other hand, the nature of these cells, positive for an immunologiCal tumor marker, cannot be determined without any genetic information. PROCEDURE: To overcome these problems a novel computer assisted scanning system for automatic cell search, analysis, and sequential repositioning was developed. This system allows an exact quantitative analysis of rare tumor cells in the bone marrow and peripheral blood by sequential immunological and molecular cytogenetic characterization. RESULTS AND CONCLUSIONS: In that virtually all tumor cells in a mixing experiment could be recovered unambiguously, we can conclude that the sensitivity of this approach is set by the number of cells available for analysis. Sequential FISH analyses of immunologically positive cells improve both the specificity and the sensitivity of the microscopic minimal residual disease detection.

Biomarkers, Tumor↗

Streptococcus iniae virulence is associated with a distinct genetic profile.

Streptococcus iniae causes meningoencephalitis and death in commercial fish species and has recently been identified as an emerging human pathogen producing fulminant soft tissue infection. As identified by pulsed-field gel electrophoresis (PFGE), strains causing disease in either fish or humans belong to a single clone, whereas isolates from nondiseased fish are genetically diverse. In this study, we used in vivo and in vitro models to examine the pathogenicity of disease-associated isolates. Strains with the clonal (disease-associated) PFGE profile were found to cause significant weight loss and bacteremia in a mouse model of subcutaneous infection. As little as 10(2) CFU of a disease-associated strain was sufficient to establish bacteremia, with higher inocula (10(7)) resulting in increased mortality. In contrast, non-disease-associated (commensal) strains failed to cause bacteremia and weight loss, even at inocula of 10(8) CFU. In addition, disease-associated strains were more resistant to phagocytic clearance in a human whole blood killing assay compared to commensal strains, which were almost entirely eradicated. Disease-associated strains were also cytotoxic to human endothelial cells as measured by lactate dehydrogenase release from host cells. However, both disease-associated and commensal strains adhered to and invaded cultured human epithelial and endothelial cells equally well. While cellular invasion may still contribute to the pathogenesis of invasive S. iniae disease, resistance to phagocytic clearance and direct cytotoxicity appear to be discriminating virulence attributes of the disease-associated clone.

Animals↗