Molecular Hazard Identification of Non-O157 Shiga Toxin-Producing Escherichia coli (STEC)

The complexity regarding Shiga toxin-producing Escherichia coli (STEC) in food safety enforcement as well as clinical care primarily relates to the current inability of an accurate risk assessment of individual strains due to the large variety in serotype and genetic content associated with (severe) disease. In order to classify the clinical and/or epidemic potential of a STEC isolate at an early stage it is crucial to identify virulence characteristics of putative pathogens from genomic information, which is referred to as ‘predictive hazard identification’. This study aimed at identifying associations between virulence factors, phylogenetic groups, isolation sources and seropathotypes. Most non-O157 STEC in the Netherlands belong to phylogroup B1 and are characterized by the presence of ehxA, iha and stx ₂, but absence of eae. The large variability in the number of virulence factors present among serogroups and seropathotypes demonstrated that this was merely indicative for the virulence potential. While all the virulence gene associations have been worked out, it appeared that there is no specific pattern that would unambiguously enable hazard identification for an STEC strain. However, the strong correlations between virulence factors indicate that these arrays are not a random collection but are rather specific sets. Especially the presence of eae was strongly correlated to the presence of many of the other virulence genes, including all non-LEE encoded effectors. Different stx-subtypes were associated with different virulence profiles. The factors ehxA and ureC were significantly associated with HUS-associated strains (HAS) and not correlated to the presence of eae. This indicates their candidacy as important pathogenicity markers next to eae and stx _2a.     

A developmental study of the phylloclades of Ruscus aculeatus L.

Lateral phylloclades of Ruscus aculeatus are found in the axils of reduced scale leaves on the orthotropic, photosynthetic stem. The terminal phylloclade results from the elongation and flattening of the main shoot apex after the lateral appendages have been initiated. Studies of the development of both lateral and terminal phylloclades point to their cauline nature. The hypothesis that the phylloclade results from the congenital fusion of a reduced short shoot and its prophyll is not supported.     

A QUANTITATIVE METHOD FOR ASSESSING THE EFFECT OF DISINFECTANTS AND CLEANING AGENTS ON BACTERIA DEPOSITED ON SURFACES

SUMMARY: A test has been developed for evaluating disinfectant action on surfaces, which relies on the pH response of Strep. faecalis , since with this organism the pH of a buffered broth at the end of incubation depends on the weight of the inoculum, i.e. the numbers of organisms which survive.
The organisms are deposited as a wet film on the surface of small strips of tinned mild steel, which are dried and treated with the disinfectant. The strips are finally placed in tubes of media and, after incubation, the pH is measured.
The standardization of the different variables of the test are described. The condition of the test organism is particularly important: at the time the films are dried it must be in its stationary phase of growth, when the cells are homogeneous and more resistant to disinfectant action than during the logarithmic phase.
Incubation is terminated when the control tubes containing strips which had no disinfectant treatment have pH values averaging 5.50. Under these conditions, with hypochlorite a linear response over the range of 0–6 p/m available chlorine is generally obtained. Chlorine may therefore be used as a standard for comparison with other disinfectants.
As an example, the testing of a quaternary ammonium compound is described.