Motility provides specific adhesion patterns and improves Listeria monocytogenes invasion into human HEp-2 cells.

Listeria monocytogenes is motile at 22°C and non-motile at 37°C. In contrast, expression of L. monocytogenes virulence factors is low at 22°C and up-regulated at 37°C. Here, we studied a character of L. monocytogenes near surface swimming (NSS) motility and its effects on adhesion patterns and invasion into epithelial cells. L. monocytogenes and its saprophytic counterpart L. innocua both grown at 22°C showed similar NSS characteristics including individual velocities, trajectory lengths, residence times, and an asymmetric distribution of velocity directions. Similar NSS patterns correlated with similar adhesion patterns. Motile bacteria, including both pathogenic and saprophytic species, showed a preference for adhering to the periphery of epithelial HEp-2 cells. In contrast, non-motile bacteria were evenly distributed across the cell surface, including areas over the nucleus. However, the uneven distribution of motile bacteria did not enhance the invasion into HEp-2 cells unless virulence factor production was up-regulated by the transient shift of the culture to 37°C. Motile L. monocytogenes grown overnight at 22°C and then shifted to 37°C for 2 h expressed invasion factors at the same level and invaded human cells up to five times more efficiently comparatively with non-motile bacteria grown overnight at 37°C. Taken together, obtained results demonstrated that (i) NSS motility and correspondent peripheral location over the cell surface did not depend on L. monocytogenes virulence traits; (ii) motility improved L. monocytogenes invasion into human HEp-2 cells within a few hours after the transition from the ambient temperature to the human body temperature.

Microcolonies: a novel morphological form of pathogenic Mycoplasma spp.

Introduction. The Mollicutes class unites cell wall lacking bacteria many of which are membrane parasites and opportunistic bacteria.Aim. This study describes a novel morphological form found in the five species belonging to the bacterial class Mollicutes, and referred to as microcolonies (MCs).Methodology. MCs were obtained as described below and characterized with bacteriological and immunological methods, and microscopy.Results. In contrast to typical colonies (TCs), MCs are characterized by tiny propeller-shaped colonies formed by rod-like cells tightly packed in parallel rows. These colonies were observed within routinely cultivated cultures of type strains 7-12 days post-plating. Rod-like cells were visualized using a scanning electron microscope within TCs with a 'fried-egg-like' appearance. MCs were not observed to revert to TCs. MCs were resistant to antibiotics and other treatments effective against TCs. Pure MC cultures were generated in vitro by treatment of Mycoplasma cultures with hyperimmune serum, antibiotics or argon non-thermal plasma. MCs of Mycoplasma hominis strain H-34 were characterized in detail to confirm that they belonged to that species. MCs tested positive via PCR with M. hominis-specific primers, direct fluorescence and epifluorescence tests, and Western blotting with the camel-derived nanobody aMh-FcG2a, which is specific to the MH3620 transporter protein. Meanwhile, MCs behaved differently in standard bacteriological tests. Pure MC cultures were also isolated directly from clinical samples of the serum, synovial liquid and urine of patients within flammatory urogenital tract diseases, asthma or arthritis. In total, 79 independent MC cultures were isolated from clinical samples including M. hominis (n=70), Mycoplasma pneumoniae (n=2), Mycoplasma fermentans (n=2) and Mycoplasma spp. (n=5).Conclusion. MCs play an unknown role in infection pathology and display prominent antibiotic resistance, making them a challenge for the future studies on Mollicutes.

Application of Transmission Electron Microscopy for Analysis of Ultrastructural Organization of Circulating Immune Complexes in Patients with Typhoid Fever and Chronic Carriers of Salmonella typhi.

Transmission electron microscopy was used to study the ultrastructural organization of circulating immune complexes (CIC), isolated from patients with typhoid fever in the different periods of acute infectious process (febrile period, period of an early and late reconvalescence), relapse and from acute and chronic carriers of Salmonella typhi in the period of pathogen excreting. It has been shown that preparations of CIC from healthy donors consisted of amorphous mean electron density material, including a cell-like detritus. At acute and chronic infectious process there were bacterial cells in a structure of the CIC. Depending on the period of disease, bacteria had different ultrastructural organization in the CIC. In the febrile period, in the period of an early reconvalescence and in the period of formation of acute carriage of S. typhi, and also in relapse, bacteria had a typical structure, with reference to gram-negative microorganisms. In the period of formation of acute and chronic carriers of S. typhi, in a period of excretion of S. typhi, bacteria in the CIC had ultrastructural organization, relevant to the forms of bacteria with a defective cell wall. Immunocytochemistry research made with the purpose of visualization the O-antigen of S. typhi in bacteria has demonstrated positive immunolabeling on the O-antigen in the bacterial forms and forms with a defective cell wall, and on amorphous mean electron density material. The analysis of ultrastructural organization of the circulating immune complexes and immunolabeling on the O-antigen of S. typhi have allowed to conclude that S. typhi, both typical bacterial form, and the forms with a defective cell wall were the main structural component of circulating immune complexes in acute and chronic forms of infectious process.