Ahmed Faris

Hydrophobic adsorptive and hemagglutinating properties ofEscherichia coli possessing colonization factor antigens (CFA/I or CFA/II), type 1 pili, or other pili

Hydrophobic and hemagglutinating activities of piliated enterotoxigenicEscherichia coli possessing colonization factor antigens (CFA)/I and putative CFA/II, strains with type 1 pili, and piliated strains of nonenterotoxigenicE. coli from urinary tract infections were compared. When passed through columns of hydrophobic Phenyl Sepharose in the presence of buffered ammonium sulfate, the strains with CFA adsorbed most strongly. Similarly, the CFA strains showed a tendency to autoagglutinate at a lower (NH4)2SO4 concentration than the other strains studied. The degree of hydrophobicity of the strains tested is in the order CFA/I>CFA/II>type 1 pili>urinary tract strains. Rough variants ofE. coli strains were more hydrophobic than their smooth parents. Electron microscopy showed large numbers of pili on CFA strains, whereas type 1 piliated strains possessed fewer pili. CFA-negative clones possessed few or no, pili and did not adsorb to the gel. A highly piliated mutant strain (PAK/2PfS) ofPseudomonas aeruginosa bound to the Phenyl Sepharose while the poorly piliated wild-type strains did not. Strains, lost their adsorptive capacity after blending, sonication, heating, or trypsin treatment. It is concluded that the hydrophobicity of enteric organisms, as measured by hydrophobic interaction chromatography, is a function of the type and number of pili on the cell surface.

Cytotonic enterotoxins and cytotoxic factors produced by Salmonella enteritidis and Salmonella typhimurium

Strains of Salmonella enteritidis and Salmonella typhimurium isolated from human diarrheal cases produced heat-labile enterotoxin(s) and cytotoxic factor(s) which elongated, lysed or deformed Chinese hamster ovary cells in tissue culture. The toxin(s) caused fluid accumulation in ligated rabbit gut loops and produced increased skin permeability. Salmonella toxin produced by these strains does not cross-react immunologically with high titer Vibrio cholerae toxin antisera or heat-labile Escherichia coli enterotoxin antisera used in this study and does not bind to galactose--Sepharose gel. The activity of the toxin was not inhibited by GM1-ganglioside.

Prevalence and characterization of Aeromonas spp. isolated from foods in Uppsala, Sweden

Different food samples collected from randomly selected retail consumer shops in Uppsala (Central Sweden) were investigated for the presence of Aeromonas species. Forty-two percent (10/24) of the food samples contained organisms belonging to two Aeromonas spp. namely, Aeromonas hydrophila and Aeromonas sobria. The type of foods from which Aeromonas were isolated, were poultry, fish, beef and pork. None of the Aeromonas spp. were isolated from vegetables or raw milk samples. The Aeromonas isolates possessed the capacity to produce different potential virulence determinants such as haemolysin, cytotoxin, cytotonic toxin, enterotoxin and protease. Since A. hydrophila and A. sobria are considered to be potential human pathogens, it is concluded that in case foodborne infections are suspected or encountered, the role of Aeromonas should not be ruled out.

Enterotoxigenicity and drug sensitivity of Aeromonas hydrophila isolated from well water in Sweden: A case study

A large number of Aeromonas spp. have been found in drinking water from a drilled well in Sweden. Isolates identified as A. hydrophila were tested for production of enterotoxin, hemolysin, enzymes and for resistant patterns to different antibiotics. The enterotoxin-producing A. hydrophila could be responsible for the long-term diarrhoeal case of a 1 1/2 year old child who consumed the contaminated water.

Isolation and virulence profiles of Aeromonas spp. from different municipal drinking water supplies in Sweden

Drinking water from three different municipal distribution systems in Sweden was investigated for the occurrence of Aeromonas spp. and identification of virulence factors of these organisms. Twenty-three of the 27 samples (85%) from the three distribution systems were positive for presumptive Aeromonas with a maximum of 860 cfu/100 ml drinking water. Of the 61 randomly selected presumptive Aeromonas isolates, 41 were identified as A. hydrophila and 20 as A. sobria . These Aeromonas isolates produced a variety of potential virulence factors such as haemolysin, cytotonic- and cytotoxic-toxin, enterotoxin and protease. These findings on the presence of Aeromonas in municipal drinking water supplies in Sweden show that the consumer can be exposed to high number of aeromonads. However, more epidemiological information needs to be gathered in this regard to elucidate their public health significance.

Growth of and toxin production by Aeromonas hydrophila and Aeromonas sobria at low temperatures

The effects of different temperatures on the growth and toxin production of Aeromonas hydrophila and Aeromonas sobria were studied. The results showed that these Aeromonas species are not only able to grow at low temperatures (e.g. at 4 and 10 degrees C) but may also produce cytotoxin, hemolysin and enterotoxin under suitable growth conditions.

High surface hydrophobicity of hemagglutinatingVibrio cholerae and other vibrios

Surface hydrophobicity of hemagglutinatingVibrio cholerae, Vibrio parahaemolyticus, and NAG vibrios has been investigated. Most strains caused mannose-sensitive hemagglutination of monkey, guinea pig, chicken, and mannose-resistant hemagglutination of human erythrocytes with different degrees of hemagglutinating activity. Hemagglutinating strains adsorbed to a hydrophobic gel (Octyl Sepharose), whereas nonhemagglutinating strains failed to adsorb.Vibrio cholerae and other vibrios investigated seem to have pronounced surface hydrophobicity as estimated by Octyl Sepharose and they correspondingly autoaggregated into visible cell clumps in ammonium sulfate solution at low molarity (0.2–0.4 M). Nonhemagglutinating strains did not aggregate even at high (2 M) ammonium sulfate concentration. The presence of surface hemagglutinins of vibrios is growth-media-dependent. Strains, grown in four different liquid media, produced hemagglutinins and expressed pronounced surface hydrophobicity. Studies with electron microscopy revealed the presence of fimbriae on the vibrio cells. The number of fimbriae on the cells varied from strain to strain. Some strains possessed more than 300 fimbriae/cell whereas others had less than 10 fimbriae/cell. Vibrio hemagglutinins are easily detached from the cell surface by heating or sonication, and their cell surface hydrophobicity decreased simultaneously.

Cell-Surface Properties of Enterotoxigenic and Cytotoxic Salmonella enteritidis and Salmonella typhimurium: Studies on Hemagglutination, Cell-Surface Hydrophobicity, Attachment to Human Intestinal Cells and Fibronectin-Binding

Thirteen Salmonella enteritidis and S. typhimurium strains with smooth or rough colony morphology were investigated for their surface properties based on hemagglutination (HA), hydrophobicity, and fibronectin‐binding profiles. The strains showed 5 different patterns of HA which was mannose‐sensitive. The rough strains possessed comparatively greater number of fimbriae than the corresponding smooth strains and also attached to human intestinal cells in greater numbers. The Salmonella strains used in this study interacted with fibronectin and its 29‐kDa N‐terminal fragment to varied extents. These properties may be helpful in broadening the prospective interaction capabilities of Salmonella organisms with the host surfaces.

Enterotoxigenic Escherichia coli (ETEC) and Klebsiella pneumoniae isolated from dogs with diarrhoea

Faecal samples from 148 dogs with diarrhoea and from 15 healthy dogs were cultured for bacterial pathogens with enterotoxigenic properties. The aim of the study was to define the toxin profile (production of heat-labile [LT] and heat-stable [ST] toxins) and possible surface fimbrial antigens. Enterotoxigenic bacteria were isolated from 6 (4.1%) dogs with diarrhoea, four of these were Escherichia coli and two were Klebsiella pneumoniae. The E. coli strains and K. pneumoniae strains were producing both LT and ST toxins. The LT toxin from these strains was not neutralized by human anti-LT serum or anti-choleragen and did not cause coagglutination with Staphylococcus aureus coated with anti-human-LT. This suggests that the LT toxin produced by these canine isolates is non-identical to LT toxin from human strains. Three of the ETEC strains were haemagglutinating and showed surface hydrophobic properties. Electron microscopy showed that canine ETEC isolates possessed fimbriae of two different types: thick (5-5.5 nm) and thin (2-3 nm).

Cytotoxic and skin permeability factors produced by Vibrio anguillarum

Abstract Extracellular products (ECP) of Vibrio anguillarum isolated from infected rainbow trout (Salmo gairdneri) have been shown to possess vascular permeability factors which affect rabbit skin. These products showed cytotoxic properties which caused elongation of R1 rainbow trout liver cells in tissue culture.In contrast, the same material caused rounding of Chinese Hamster Ovary (CHO) cells. These factors are inactivated when heated at 80°C.