Shiga-toxigenic Escherichia coli from animal food sources in Mauritius: Prevalence, serogroup diversity and virulence profiles.

Shiga-toxigenic Escherichia coli (STEC) are important human pathogens associated with diarrhea and in some cases haemorrhagic colitis. Contaminated food derived from cattle and wildlife species are often associated with disease outbreaks. In this study, we report the prevalence, serogroup diversity and virulence profiles of STEC strains derived from cattle, rusa deer and pig. Of the 422 samples analyzed, STEC were detected in 40% (80/200) of cattle, 27.0% (33/122) of deer and 13.0% (13/100) of pigs. STEC isolates belonged to 38 O-serogroups whereby 5.2% (24/462) of the isolates belonged to clinically important EHEC-7 serogroups: O26 (n = 2), O103 (n = 1), O145 (n = 3) and O157 (n = 18). Fourteen serogroups (O26, O51, O84, O91, O100, O104, O110, O117, O145, O146, O156, O157, O177 and ONT) displayed multiple virulence profiles. We also identified two serovars (O117 and O119) in deer which are not well-documented in epidemiological surveys. 73.7% (28/38) of recovered O-serogroups are known to be associated with serious human illnesses including haemolytic uremic syndrome (HUS) and bloody diarrhea. STEC isolates harboring single genotypes stx1, stx2, eae and hlyA accounted for 3.0% (14/462), 9.1% (42/462), 47.6% (220/462) and 1.7% (8/462) of all STEC isolates screened, respectively. Virulence combinations stx1 and stx2 were harboured by 1.3% of isolates while strains with genetic profiles eae/hlyA were the second most prevalent amongst STEC isolates. The full known virulent genotypes (stx2/eae, stx1/stx2/eae, stx1/stx2/hlyA and stx2/eae/hlyA) were present in 22 of the 462 STEC strains. A total of 10 different virulence patterns were recovered amongst animal species. Phylogeny of the gnd gene showed that amongst STEC strains, serovar O100 outlined the main cluster. Fourteen (n = 14) different sequence types (STs) were identified from a panel of twenty (n = 20) STEC isolates. One of the isolate (PG007B) possessed a unique ST (adk 10, fumC 693, gyrB 4, icd 1, mdh 8, purA 8, recA 2) that could not be assigned using MLST databases. None of the ST's recovered in deer were observed in domestic species. Our findings shows that food associated animals found on the tropical island of Mauritius carry a diversity of STEC strains with many serovars known to be associated with human disease. This report indicates that increased awareness, surveillance and hygienic attention at critical stages of the human food chain are warranted.

Long-term ecosystem monitoring and assessment of the Detroit River and Western Lake Erie.

Over 35 years of US and Canadian pollution prevention and control efforts have led to substantial improvements in environmental quality of the Detroit River and western Lake Erie. However, the available information also shows that much remains to be done. Improvements in environmental quality have resulted in significant ecological recovery, including increasing populations of bald eagles (Haliaeetus leucocephalus), peregrine falcons (Falco columbarius), lake sturgeon (Acipenser fulvescens), lake whitefish (Coregonus clupeaformis), walleye (Sander vitreus), and burrowing mayflies (Hexagenia spp.). Although this recovery is remarkable, many challenges remain, including population growth, transportation expansion, and land use changes; nonpoint source pollution; toxic substances contamination; habitat loss and degradation; introduction of exotic species; and greenhouse gases and global warming. Research/monitoring must be sustained for effective management. Priority research and monitoring needs include: demonstrating and quantifying cause-effect relationships; establishing quantitative endpoints and desired future states; determining cumulative impacts and how indicators relate; improving modeling and prediction; prioritizing geographic areas for protection and restoration; and fostering long-term monitoring for adaptive management. Key management agencies, universities, and environmental and conservation organizations should pool resources and undertake comprehensive and integrative assessments of the health of the Detroit River and western Lake Erie at least every 5 years to practice adaptive management for long-term sustainability.

Structure and seasonal dynamics of hyporheic zone microbial communities in free-stone rivers of the western United States.

The hyporheic zone of a river is characterized by being nonphotic, exhibiting chemical/redox gradients, and having a heterotrophic food web based on the consumption of organic carbon entrained from surface waters. Hyporheic microbial communities constitute the base of food webs in these environments and are important for maintaining a functioning lotic ecosystem. While microbial communities of rivers dominated by fine-grained sediments are relatively well studied, little is known about the structure and seasonal dynamics of microbial communities inhabiting the predominantly gravel and cobble hyporheic zones of rivers of the western United States. Here, we present the first molecular analysis of hyporheic microbial communities of three different stream types (based on mean base discharge, substratum type, and drainage area), in Montana. Utilizing 16S rDNA phylogeny, DGGE pattern analysis, and qPCR, we have analyzed the prokaryotic communities living on the 1.7 to 2.36 mm grain-size fraction of hyporheic sediments from three separate riffles in each stream. DGGE analysis showed clear seasonal community patterns, indicated similar community composition between different riffles within a stream (95.6-96.6% similarity), and allowed differentiation between communities in different streams. Each river supported a unique complement of species; however, several phylogenetic groups were conserved between all three streams including Pseudomonads and members of the genera Aquabacterium, Rhodoferax, Hyphomicrobium, and Pirellula. Each group showed pronounced seasonal trends in abundance, with peaks during the Fall. The Hyphomicrobium group was numerically dominant throughout the year in all three streams. This work provides a framework for investigating the effects of various environmental factors and anthropogenic effects on microbial communities inhabiting the hyporheic zone.

Effects of in vitro electrical stimulation on enhancement and suppression of malignant lymphoma cell proliferation.

The suppression and enhancement of proliferation of mouse EL4 lymphoma cells varied significantly when the cells were electrically stimulated within a narrow range of low-level direct current. With the use of platinum electrodes, the suppression characteristics were observed over a narrow range, or window, of direct currents centered at approximately 17 microA. Enhancement characteristics were observed over a broad range of low-level direct currents (approximately 0.1 to 10 microA). These results indicate that the proliferation of certain eukaryotic cells may be directly controlled by stimulation with low-level direct current.

Identification, location and analysis of contamination problems associated with cell/tissue preparation, stimulation and measurement techniques.

Any time a cell suspension or tissue sample is handled, chemically treated and prepared or measured with electrical or electrochemical probes, some level of contamination will occur. Often, the level and type of contamination can lead to serious misinterpretation of experimental results. A number of specific contamination problems have been consistently observed with certain preparation, stimulation and measurement techniques utilized in cell biology, histology, microbiology and pharmacology. Four of the more serious problems that can occur are as follows: 1) contamination from media constituents; 2) contamination of cell suspensions and tissue from constituents and impurities in glassware; 3) fungal contamination of cell and tissue samples from glutaraldehyde fixatives and 4) contamination of cell suspensions and tissues from metal ions that have dissociated from electrodes and probes. A scanning electron microscope/energy dispersive x-ray (SEM/EDX) system can provide the resolution, sensitivity and analytical capability to detect these contaminants in a variety of locations, identify them and determine their origin. Thus, erroneous conclusions from data that have been affected by various contaminants can be minimized or prevented if the problems are identified and located.

Microbial degradation of diethanolamine and related compounds.

Thirteen diethanolamine compounds were tested for their biodegradability employing (1) a bacterium selectively isolated from an industral cutting fluid, and (2) an acclimatized sewage population obtained from a domestic waste treatment plant. Pure culture growth and biochemical oxygen demand studies with the isolate showed that only diethanolamine, methyl-diethanolamine, triethanolamine, and laurylsulphate-diethanolamine were degradable. Biochemical oxygen demand techniques using the acclimatized sewage micro-organisms as seed yielded similar results with only diethanolamine, methyl-diethanolamine, triethanolamine, and laurylsulphate-diethanolamine being oxidized to any meaningful extent. Cyclohexyldiethanolamine, phenyl-diethanolamine, and m-tolyl-diethanolamine had oxygen demands of less than 1% of their theoretically calculated values, while ethyl-diethanolamine and benzyl-diethanolamine accounted for 3.6 and 2.3% of their theoretical values respectively. In both systems employed substitution of the tertiary hydrogen of the amine group with isopropyl, 3-aminopropyl, n-butyl, or t-butyl resulted in biologically recalcitrant compounds.