Transient increases in colony counts observed in declining populations of Campylobacter jejuni held at low temperature.
Ekweozor CC. Nwoguh CE. Barer MR.
Department of Microbiology, Medical School, Newcastle upon Tyne, UK.
Colony forming unit counts of Campylobacter jejuni were serially determined in a variety of microcosms in which growth was not expected. Unremitting decline in colony counts occurred in nutrient-free systems, however, transient increases were observed in human faecal emulsions and nutrient media on storage at between 1 and 25 degrees C. The phenomenon, which was more pronounced at lower temperatures, could not be attributed to sampling errors, cell clumping or the influence of minor fluctuations in experimental conditions. C. jejuni is capable of either growth at low temperatures or transition between temporarily nonculturable and culturable states.
Genomic DNA fingerprinting of clinical isolates of Helicobacter pylori by REP-PCR and restriction fragment end-labelling.
van Doorn NE. Namavar F. Kusters JG. van Rees EP. Kuipers EJ. de Graaff J.
Department of Medical Microbiology, Vrije Universiteit Amsterdam, The Netherlands. NEM.van_Doorn.MM@med.vu.nl
Genetic diversity of 32 Helicobacter pylori strains isolated from patients with gastritis, gastric or duodenal ulcer, carcinoma, or lymphoma was determined by repetitive sequence element polymerase chain reaction (REP-PCR), and by the new typing method restriction fragment end-labelling (RFEL). Furthermore, these two methods were used to investigate a possible correlation between clinical symptoms and the genetic background of Helicobacter pylori. Both REP-PCR and RFEL revealed 31 different patterns for the 32 strains tested, but the pair of isolates with identical REP-PCR patterns was not the same as the pair of isolates with identical RFEL patterns. Computer-assisted analysis of the DNA fingerprints was used to determine similarity coefficients. This analysis revealed no clustering of disease-specific strains by any of the two methods.
Characterization of a 20-kDa pilus protein expressed by a diarrheogenic strain of non-O1/non-O139 Vibrio cholerae.
Sengupta TK. Nandy RK. Mukhopadhyay S. Hall RH. Sathyamoorthy V. Ghose AC.
Department of Microbiology, Bose Institute, Calcutta, India.
A diarrheogenic strain of non-O1/non-O139 Vibrio cholerae (10,325) belonging to serogroup O34 was earlier shown to express a new type of pilus composed of a 20-kDa subunit protein. Amino-terminal sequence data (determined up to 20 amino acid residues) of this protein showed it to be different from the subunit proteins of other known types of pili of V. cholerae. On the other hand, it showed complete homology with the corresponding sequence of a 22-kDa outer membrane protein (OmpW) of V. cholerae. Expression of 10,325 pili was favored in AKI rather than in NB medium and at 30 degrees C rather than at 37 degrees C. Further, cultural conditions favoring pilus expression also enhanced autoagglutination and adherence properties of strain 10,325. An antiserum to the 20-kDa protein induced passive protection against challenge with the parent organism 10,325, but not against V. cholerae O1 strains. Such protection was shown to be mediated by inhibition of intestinal colonization in vivo.