Summary. Listeria monocytogenes cells are ingested by protozoa such as Acanthamoeba sp. or Tetrahyrnenapyrlformis. However, they are not killed, but survive within the protozoa and may multiply intracellularly. The protozoa are lysed within about 8 days, releasing viable L. monocytogenes. No co-existence was observed between L . monocytogenes and Tetrahymena. A co-culture of L . monocytogenes and Acanthamoeba sp. showed a decay of locomotive forms and release of listeria from vegetative protozoan cells whereas the bacteria were destroyed in cysts. These phenomena provide an insight into the pathogenesis of listeria infection in man and warmblooded animals because intracellular processes occurring in protozoa after ingestion of L. monocytogenes may be similar to those observed in mammalian cells.

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Summary. Consistent major differences were detected by SDS-PAGE, Western blotting and Ouchterlony immunodiffusion in four axenic and microscopically indistinguishable strains of the anaerobic human parasite Blastocystis horninis from different sources. It is concluded that at least two variants with different polypeptide patterns and antigens exist and the biological significance of these findings is discussed.

A total of 2,693 fecal specimens, with 1,422 from healthy persons and 1,271 from patients suffering from enteric diseases, was investigated to isolate species of the Morganella-Proteus-Providencia group and to evaluate the role of these bacteria in intestinal disorders. Most strains were isolated from two media, i.e., blood agar and tryptophan agar. Two of the species were more frequently found in diarrheal cases than in healthy controls. These species were Morganella morganii and Proteus mirabilis. Two new species of Enterobacteriaceae, i.e., Proteus penneri and Providencia rustigianii, were found in 33 and 5 people, respectively. However, these two species were not found more frequently in the diarrheal cases.

~~Fifty-one Rahnella aquatilis and R. aquatilis-like strains from water, snails and human sources were characterized by routine biochemical tests, carbon source utilization tests, DNA relatedness (hydroxyapatite method) and 16s rRNA sequencing. The results of the genetic methods indicated that the strains comprised three closely related species within the genus Rahnella. It was not possible to differentiate R. aquatilis from the two newly recognized species. The new species were therefore given the vernacular names Rahnella genomospecies 2 and Rahnella genomospecies 3.