The zebrafish is an excellent genetic system for the study of vertebrate development and disease. In an effort to provide a rapid and robust tool for zebrafish gene mapping, a panel of radiation hybrids (RH) was produced by fusion of irradiated zebrafish AB9 cells with mouse B78 cells. The overall retention of zebrafish sequences in the 93 RH cell lines that constitute the LN54 panel is 22%. Characterization of the LN54 panel with 849 simple sequence length polymorphism markers, 84 cloned genes and 122 expressed sequence tags allowed the production of an RH map whose total size was 11,501 centiRays. From this value, we estimated the average breakpoint frequency of the LN54 RH panel to correspond to 1 centiRay ‫؍‬ 148 kilobase. Placement of a group of 235 unbiased markers on the RH map suggests that the map generated for the LN54 panel, at present, covers 88% of the zebrafish genome. Comparison of marker positions in RH and meiotic maps indicated a 96% concordance. Mapping expressed sequence tags and cloned genes by using the LN54 panel should prove to be a valuable method for the identification of candidate genes for specific mutations in zebrafish.Somatic-cell hybrids and radiation hybrids (RHs) have played a key role in the mapping of human and mouse genes (1-7). Cell hybrids constitute one of the most expedient methods for assigning genes to chromosomes or chromosome segments, because mapping with cell hybrids does not require gene polymorphism. RHs are generated by irradiating cells from a donor species, causing random chromosomal breaks, and fusing these to a cell line from a different species. Donor-cell chromosome fragments are retained to different extents in the ensuing hybrid cells. Typing a panel of RHs with PCR-based sequence-tagged sites creates an RH map in which the frequency of breakpoints between two markers is proportional to the distance between them.The large collection of mutations produced in the zebrafish constitutes a valuable resource for the study of vertebrate developmental mechanisms (8-10). The efficient identification of the genes disrupted by mutation in zebrafish requires dense maps of the genome. Meiotic maps based on rapidamplified polymorphic DNA sequences and microsatellite markers have been produced (11-16). Since localization of cDNAs and expressed sequence tags (ESTs) on meiotic maps requires the identification of polymorphisms, the use of RH mapping is a valuable complementary method suitable for high-throughput cDNA/EST mapping projects to identify candidate genes for available mutants.We have previously shown that stable transfer of zebrafish chromosomes or chromosome segments to a rodent cell line was possible (17). Markers from the simple sequence-length polymorphism (SSLP) meiotic map could be anchored on a panel of zebrafish/mouse somatic-cell hybrids (14). Furthermore, Kwok et al. (18) demonstrated that RH technology could be used for nonmammalian vertebrates. In the present study, we report characterization of LN54, a zebrafish RH panel composed of 93 cell...

Closely related strains of Escherichia coli have been shown to cause extraintestinal infections in unrelated persons. This study tests whether a food reservoir may exist for these E. coli. Isolates from 3 sources over the same time period (2005–2007) and geographic area were compared. The sources comprised prospectively collected E. coli isolates from women with urinary tract infection (UTI) (n = 353); retail meat (n = 417); and restaurant/ready-to-eat foods (n = 74). E. coli were evaluated for antimicrobial drug susceptibility and O:H serotype and compared by using 4 different genotyping methods. We identified 17 clonal groups that contained E. coli isolates (n = 72) from >1 source. E. coli from retail chicken (O25:H4-ST131 and O114:H4-ST117) and honeydew melon (O2:H7-ST95) were indistinguishable from or closely related to E. coli from human UTIs. This study provides strong support for the role of food reservoirs or foodborne transmission in the dissemination of E. coli causing common community-acquired UTIs.

Multiple chromosome 3p tumor suppressor genes (TSG) have been proposed in the pathogenesis of ovarian cancer based on complex patterns of 3p loss. To attain functional evidence in support of TSGs and identify candidate regions, we applied a chromosome transfer method involving cell fusions of the tumorigenic OV90 human ovarian cancer cell line, monoallelic for 3p and an irradiated mouse cell line containing a human chromosome 3 in order to derive OV90 hybrids containing normal 3p fragments. The resulting hybrids showed complete or incomplete suppression of tumorigenicity in nude mouse xenograft assays, and varied in their ability to form colonies in soft agarose and three-dimensional spheroids in a manner consistent with alteration of their in vivo tumorigenic phenotypes. Expression microarray analysis identified a set of common differentially expressed genes, such as SPARC, DAB2 and VEGF, some of which have been shown implicated in ovarian cancer. Genotyping assays revealed that they harbored normal 3p fragments, some of which overlapped candidate TSG regions (3p25-p26, 3p24 and 3p14-pcen) identified previously in loss of heterozygosity analyses of ovarian cancers. However, only the 3p12-pcen region was acquired in common by all hybrids where expression microarray analysis identified differentially expressed genes. The correlation of 3p12-pcen transfer and tumor suppression with a concerted reprogramming of the cellular transcriptome suggest that the putative TSG may have affected key underlying events in ovarian cancer.

Women with urinary tract infections (UTIs) in California, USA (1999USA ( -2001, were infected with closely related or indistinguishable strains of Escherichia coli (clonal groups), which suggests point source dissemination. We compared strains of UTI-causing E. coli in California with strains causing such infections in Montréal, Québec, Canada. Urine specimens from women with community-acquired UTIs in Montréal (2006) were cultured for E. coli. Isolates that caused 256 consecutive episodes of UTI were characterized by antimicrobial drug susceptibility profi le, enterobacterial repetitive intergenic consensus 2 PCR, serotyping, XbaI and NotI pulsed-fi eld gel electrophoresis, multilocus sequence typing, and phylogenetic typing. We confi rmed the presence of drug-resistant, genetically related, and temporally clustered E. coli clonal groups that caused community-acquired UTIs in unrelated women in 2 locations and 2 different times. Two clonal groups were identifi ed in both locations. Epidemic transmission followed by endemic transmission of UTI-causing clonal groups may explain these clusters of UTI cases.

This study investigated the relationship between hospital exposures, intestinal microbiota, and subsequent risk of Clostridium difficile-associated disease (CDAD), with use of a nested case-control design. The study included 599 patients, hospitalized from September 2006 through May 2007 in Montreal, Quebec, from whom fecal samples were obtained within 72 h after admission; 25 developed CDAD, and 50 matched controls were selected for analysis. Nonsteroidal anti-inflammatory drugs and antibiotic use were associated with CDAD. Fecal specimens were evaluated by 16S ribosomal RNA microarray to characterize bacteria in the intestinal microbiota during the at-risk period. Probe intensities were higher for Firmicutes, Proteobacteria, and Actinobacteria in the patients with CDAD, compared with controls, whereas probe intensities for Bacteroidetes were lower. After epidemiologic factors were controlled for, only Bacteroidetes and Firmicutes remained significantly and independently associated with development of CDAD. Hospital exposures were associated with changes in the intestinal microbiota and risk of CDAD, and these changes were not driven exclusively by antimicrobial use.