Biomedical subjects

M Pommepuy

Publications and source records attributed to M Pommepuy.

27 records · Page 2Linked to original sources

PubMed1994

Visible light damage to Escherichia coli in seawater: oxidative stress hypothesis.

The effect of visible light on Escherichia coli H10407 in seawater microcosms was investigated. Light damage was estimated by loss of colony-forming ability. Illumination of E. coli suspended in oligotrophic seawater with visible light at an intensity of about 40 klux caused a drastic decrease of culturable bacteria which turned to a viable but non-culturable state. In seawater E. coli exhibited weak metabolic activity as estimated by 3H methyl-thymidine incorporation in the cell. Visible light did not significantly alter this metabolic activity and did not involve detectable oxidation of lipid membranes as evaluated by gas chromatography analysis of fatty acids. The involvement of oxygen and reactive oxygen species in phototoxicity was studied. A decrease of the toxic effect was observed when E. coli was exposed to visible light under anaerobic conditions. Scavengers of reactive oxygen species exhibited variable protective effects. beta-Carotene, a singlet oxygen scavenger, and superoxide dismutase were equally ineffective. On the other hand, catalase, which eliminates hydrogen peroxide and thiourea, a hydroxyl radical scavenger, showed a net protection. In addition desferrioxamine B, an iron chelator, was also effective in reducing phototoxicity, probably by preventing hydroxyl radical generation by decomposition of hydrogen peroxide in the presence of iron (Fenton reaction). Therefore, hydrogen peroxide and hydroxyl radical seem to be reactive intermediates of oxygen-dependent (type II) photosensitized reactions.

Bacterial Proteins↗

PubMed1994

Detection of hepatitis A virus, rotavirus, and enterovirus in naturally contaminated shellfish and sediment by reverse transcription-seminested PCR.

A reverse transcription-PCR method was developed to detect enterovirus (EV), hepatitis A virus (HAV), and rotavirus (RV) RNAs in shellfish and sediment. The method was first tested under experimental conditions by using virus-spiked shellfish to evaluate assay sensitivity. The use of CC41 cellulose was found to be efficient for removing inhibitors of RV detection. For sediment samples, a Sephadex column was used to allow the detection of EV and HAV RNAs. The specificity of amplified products was controlled by hybridization with digoxigenin-labeled oligoprobes. The method was then applied to naturally contaminated shellfish and sediments. EV, HAV, and RV RNAs were detected in 22, 14, and 20% of the shellfish samples, respectively. No relationship between viral contamination and bacterial contamination was found. When viral RNAs (HAV or EV) were detected in sediments, they were also detected in shellfish.

Animals↗

PubMed1994

Monitoring of fecal pollution in coastal waters by use of rapid enzymatic techniques.

Enzyme assays for 4-methylumbelliferyl-beta-D-galactopyranosidase and 4-methylumbelliferyl-beta-D-glucuronidase activities were used for rapid detection (25 min) of fecal water pollution and to determine the impact of sewage discharge in coastal waters. Two coastal areas were investigated: (i) an estuary characterized by a high degree of contamination downstream of a discharge from a sewage treatment plant and a low degree of water renewal and (ii) a fjord with a low degree of pollution and a high degree of water renewal. Statistical analysis showed that a global correlation curve could be used to estimate concentrations of culturable fecal coliform bacteria in the two coastal areas, although environmental factors important for cell physiology (e.g., salinity) varied at different sampling locations. The sensitivity limit for detection of 4-methylumbelliferyl-beta-D-glucuronidase activity corresponded to bacterial concentrations on the order of 10 to 100 CFU/100 ml. The 4-methylumbelliferyl-beta-D-galactopyranosidase assay was less sensitive because of a higher rate of substrate autohydrolysis. The detection limit corresponded to bacterial concentrations on the order of 100 to 1,000 fecal coliforms per 100 ml.

Environmental Monitoring↗

PubMed1994

Detection of enterotoxigenic Escherichia coli in water by polymerase chain reaction amplification and hybridization.

Enterotoxigenic Escherichia coli was studied in waste water, river water, and seawater from six locations along the west coast of Normandy by using the polymerase chain reaction (PCR) to amplify the heat labile (LT) gene. Cellular DNA was extracted from centrifugation pellets and amplified using PCR. The PCR products were detected by gel electrophoresis and confirmed by hybridization assay, using an 850 base pair HindIII DNA fragment probe from pEWD299 conjugated to digoxigenin and specific for the LT gene. Results of the PCR amplification were compared with those of GM1 enzyme-linked immunosorbent assay, latex agglutination, and colony hybridization. The PCR method was found to be more precise and less time consuming, especially when compared with methods requiring culture of isolates for enumeration of enterotoxigenic E. coli in water.

Base Sequence↗

PubMed1993

Two-dimensional electrophoresis method used for determination of plasmid profiles of Escherichia coli isolated from a sewage treatment plant.

The plasmid contents of 306 strains of Escherichia coli isolated from raw and treated sewage from a treatment plant as well as from the water 1 km downstream were determined. The number and molecular weight of plasmids isolated from a representative sample of these strains were also measured. It was observed that biological treatment did not significantly alter these parameters. In contrast, statistically significant differences in plasmid number and size were observed when strains from sewage (raw and treated) were compared with strains isolated from brackish water. In raw and treated sewage, more than 96% of the strains contained plasmids, compared with 85% in brackish water. Nine to 13% of the strains from sewage contained plasmids with more than 56 kilobases, while only 5% of the strains from brackish water reached this size.

Electrophoresis, Gel, Two-Dimensional↗

PubMed1991

Influence of sewage discharge on the pollution of an estuary (Morlaix, France).

The purpose of this paper is to evaluate the pollution introduced into the Morlaix estuary by the city discharge of sewage and to determine its consequences on the microbiological quality of estuarine water and sediment. It has been shown that between 10(13) and 10(14) fecal coliforms and streptococci and between 10(6) and 10(7) enteroviruses are thus conveyed per day. The study of the downstream contamination indicates that the bacterial and viral density is much more significant in the sediment and that the bacterial concentration decreases gradually from upstream to downstream whereas the viral density only varies slightly in the water and shows very irregular fluctuation in the sediment.

Bacteria↗

PubMed1991

[Implantation of Escherichia coli in pilot experiments and the influence of competition on the flora].

Implantation in seawater and (or) sediment of bacterial flora and the influence of such flora upon the survival and growth of an Escherichia coli of human origin have been the object of experimental pilot studies. The selected pilot plant permitted work on large volumes of seawater and sediment, and maintenance of the structure of the latter. Diverse experiments were carried out in the presence or absence of seawater and (or) sediment bacterial flora during 13 days. Escherichia coli bacteria were introduced in the seawater experimental system at concentrations of 1 to 3 X 10(5) colony-forming units (cfu) per 100 mL. In sterile sediment, E. coli bacteria first went through a proliferative phase and then implanted themselves (3 X 10(4) cfu/100 g at 0 days and 4 X 10(5) cfu/100 g at 13 days). Diffusion in the supernatant sterile seawater of organic matter released from sediment allowed the strain to proliferate (8 X 10(6) cfu/100 mL at 1 day) and survive for a few days (1 X 10(4) cfu/100 mL at 6 days), prior to an ultimate decreasing phase (1 cfu/100 mL at 13 days). In the presence of the seawater indigenous flora, an immediate decrease (2 X 10(3) cfu/100 mL at 6 days), without a growth or even a survival phase, evidenced a selection pressure. In a nonsterile sediment, in the presence or absence of seawater indigenous flora, E. coli bacteria implanted themselves quickly (5 X 10(4) cfu/100 g at 1 day) and survived (1 X 10(4) cfu/100 g at 13 days). In the supernatant seawater, a decrease was observed from the 1st day.(ABSTRACT TRUNCATED AT 250 WORDS)

Escherichia coli↗

PubMed1989

Effect of carbonyl cyanide m-chlorophenylhydrazone on Escherichia coli halotolerance.

The growth-inhibitory effect of carbonyl cyanide m-chlorophenylhydrazone (CCCP) was less on members of the family Enterobacteriaceae (halotolerant organisms) than it was on species of Vibrio (moderately halophilic organisms). When sodium chloride concentration increased from 0.5 to 0.85 M, this effect was more pronounced for Escherichia coli; it remained relatively stable for Vibrio spp. The effect of carbonyl cyanide m-chlorophenylhydrazone was antagonized by the addition of glycine betaine or proline or by growth in a rich medium.

Carbonyl Cyanide m-Chlorophenyl Hydrazone↗

PubMed1989

Production of 4-methylumbelliferyl heptanoate hydrolase by Escherichia coli exposed to seawater.

The production of an enzyme, 4-methylumbelliferyl heptanoate hydrolase, in Escherichia coli exposed to enriched and nonenriched seawater was studied. In all media, except for seawater with no or very small amounts of organic material and seawater enriched with peptone, 4-methylumbelliferyl heptanoate hydrolase activity increased by 2 to 3 orders of magnitude within 2 days. Increased enzyme activity was assumed to be related to cells not undergoing lysis but adapting to conditions of nutrient limitation.

Colony Count, Microbial↗