PCR typing of Corynebacterium diphtheriae by random amplification of polymorphic DNA.

The usefulness of random amplification of polymorphic DNA (RAPD) analysis with Ready-To-Go RAPD beads was investigated for the rapid differentiation of Corynebacterium diphtheriae isolates from Eastern Europe and neighbouring countries. A selection of 45 C. diphtheriae isolates of known origin, biotype, toxigenicity status and ribotype were examined by RAPD. Twenty RAPD profiles (designated Rp1-Rp20) were revealed among the 45 isolates. There was 100% correlation between RAPD profiles and ribotypes. Preliminary studies showed that the use of crude DNA preparations resulted in poor amplification and the patterns were not reproducible. Different thermal cycler models produced different RAPD profiles from the same DNA sample. Reproducibility of the technique was good when the same thermal cycler was used throughout. RAPD proved to be a simple and a rapid method for analysing C. diphtheriae and it is a method which can be used as a potential alternative to ribotyping or as a screening technique during outbreak investigations.

Molecular typing of Legionella pneumophila serogroup 1 by pulsed-field gel electrophoresis with SfiI and comparison of this method with restriction fragment-length polymorphism analysis.

A panel of 131 well-characterised Legionella pneumophila serogroup 1 strains, previously used to evaluate a restriction fragment-length polymorphisms (RFLP) typing scheme, was examined by pulsed-field gel electrophoresis (PFGE) with the restriction endonuclease SfiI. The data obtained show that PFGE with SfiI is a highly discriminatory method yielding an index of discrimination (IOD) of 0.992 and 0.975, with 100% and 90% similarity thresholds respectively, compared with an IOD of 0.909 for the RFLP typing method. Reproducibility of PFGE profiles within gels was excellent and it was possible to compare the profiles visually. However, the reproducibility of the technique between gels was poor and visual comparison of the patterns was extremely difficult. Computer-aided analysis assisted the assessment of inter-gel reproducibility. Of 11 duplicates examined only four pairs showed 100% similarity, although 9 of 11 showed > or =90% similarity. In an attempt to determine if the PFGE banding patterns were sufficiently unambiguous to allow the method to be used as a definitive typing method, 20 coded strains were examined. At a 90% similarity level, 16 of these were placed in the correct PFGE type and four were not allocated to a type. Partial digestion of DNA by SfiI was noted despite careful control of DNA and enzyme concentrations, suggesting that an alternative enzyme might give more reproducible results.

The place of the specialist home for the elderly mentally infirm in the care of mentally disturbed old people.

In a city where specialist homes for the elderly mentally infirm (EMI) have been extensively developed, a study was carried out to determine if residents in such homes were mentally impaired to a degree intermediate between that of residents in ordinary homes, and those in psychogeriatric beds. The study, using valid measures of cognitive impairment and functional disability, showed that while the proportion of cases of senile dementia was similar in all three settings, the severity of disability was graded in the expected direction. Furthermore, cases of mental illness other than senile dementia were almost exclusively found in the EMI homes and psychogeriatric hospitals. However, one in ten of ordinary home residents suffered from senile dementia of a severity which presented problems to the care attendants and the implication of this finding for the level of provision of psychogeriatric beds is discussed.