Atypical Enteropathogenic Escherichia coli That Contains Functional Locus of Enterocyte Effacement Genes Can Be Attaching-and-Effacing Negative in Cultured Epithelial Cells

Enteropathogenic Escherichia coli (EPEC) induces a characteristic histopathology on enterocytes known as the attaching-and-effacing (A/E) lesion, which is triggered by proteins encoded by the locus of enterocyte effacement (LEE). EPEC is currently classified as typical EPEC (tEPEC) and atypical EPEC (aEPEC), based on the presence or absence of the EPEC adherence factor plasmid, respectively. Here we analyzed the LEE regions of three aEPEC strains displaying the localized adherence-like (LAL), aggregative adherence (AA), and diffuse adherence (DA) patterns on HEp-2 cells as well as one nonadherent (NA) strain. The adherence characteristics and the ability to induce A/E lesions were investigated with HeLa, Caco-2, T84, and HT29 cells. The adherence patterns and fluorescent actin staining (FAS) assay results were reproducible with all cell lines. The LEE region was structurally intact and functional in all strains regardless of their inability to cause A/E lesions. An EspFU-expressing plasmid (pKC471) was introduced into all strains, demonstrating no influence of this protein on either the adherence patterns or the capacity to cause A/E of the adherent strains. However, the NA strain harboring pKC471 expressed the LAL pattern and was able to induce A/E lesions on HeLa cells. Our data indicate that FAS-negative aEPEC strains are potentially able to induce A/E in vivo, emphasizing the concern about this test for the determination of aEPEC virulence. Also, the presence of EspFU was sufficient to provide an adherent phenotype for a nonadherent aEPEC strain via the direct or indirect activation of the LEE4 and LEE5 operons.

A function of polar flagellum and anisotropic growth in Vibrio alginolyticus early-phase colonies.

We continuously observed growth of Vibrio alginolyticus early-phase colonies on agar plates by phase-contrast microscopy. Two mutants defective in motility on solid surfaces were used in this study: one (YM4) can swim in liquid environments using its polar flagellum, and the other (NMB198) cannot swim because it lacks any flagella. We found that isolated colonies of YM4 were generally more circular than those of NMB198. This observation suggests that YM4 cells moved slightly within a colony by the function of their polar flagella. For clustered colonies, where the distance between the colonies was short (<50 microm), the colonies of YM4 grew rapidly along the line between them, but they grew slowly in the lateral directions. Some colonies of NMB198 grew toward neighboring colonies. These observations indicate colony-to-colony interaction.

[Influence of aeration and phosphorus concentration in the medium on growth of S-, R- and M-forms of Mycobacterium lacticolum in mixed cultures]. / Vliianie aeratsii i kontsentratsii fosfora v srede na rost S-, R- i M-form Mycobacterium lacticolum v smeshannykh kul'turakh.

S, R and M forms of Mycobacterium lacticolum were compared. The cells of the R form had the highest requirement in aeration and phosphorus, whereas the cells of the M form, the lowest requirement. The content of oxygen in the medium and the concentration of phosphorus almost did not affect the viriability of these forms. On a medium containing n-hexadecane, the cells of the R form possessed selective advantages under favourable growth conditions, i.e. when the content of oxygen and phosphorus in the medium was high, whereas the cells of the M form had selective advantages under unfavourable conditions of growth when it decelerated as a result of a low concentration of oxygen and phosphorus in the medium. These correlations changed on a medium containing carbohydrates.

Aberrant bacterial forms from various ocular sites.

Patients may harbor cell-wall-deficient organisms or other aberrant bacterial forms (ABFs) in their eyes. In this survey of 400 cultures, we found the incidence of ABFs isolated from various ocular sites to be 13.2%. The rate of isolation of these forms from the eyes of patients with suspected bacterial infection differed greatly from that for noninfected eyes. We will describe the microbiological techniques employed and will present our analysis of the data obtained.