The potential role of inhaled protozoa as a niche for intrapulmonary replication of Legionella pneumophila was investigated in vivo with mutant strains of L. pneumophila which have reduced virulence for the amoeba Hartmannella vermiformis. L. pneumophila AA488 and AA502 were derived from wild-type strain AA100 after transposon mutagenesis. These mutants have reduced virulence for H. vermiformis...

The contractile vacuole is an organelle found in most freshwater Protozoa. In ameba, as studied with the light microscope, it is usually described as spherical, with a rather thick limiting membrane and surrounded by a layer of mitochondria (Fig. 1). The contractile vacuole undergoes a continuous series of cyclic changes. I t enlarges gradually (diastole), collecting water until it reaches a cr...

Prepilin peptidases cleave, among other substrates, the leader sequences from prepilin-like proteins that are required for type II protein secretion in Gram-negative bacteria. To begin to assess the importance of type II secretion for the virulence of an intracellular pathogen, we examined the effect of inactivating the prepilin peptidase (pilD) gene of Legionella pneumophila. Although the pilD...

Forty eyewash units were sampled for protozoa, bacteria, and fungi. Total heterotrophic bacterial counts on nutrient agar and R2A agar (Difco Laboratories, Detroit, Mich.) ranged from 0 to 10(5) CFU/ml, with Pseudomonas spp. being the most frequently isolated. Total counts of 10(4) and 10(8) cells per ml were obtained with the acridine orange staining procedure. All samples were examined for Le...

Legionella pneumophila is an intracellular pathogen of protozoa and alveolar macrophages. This bacterium contains a gene (pilD) that is involved in both type IV pilus biogenesis and type II protein secretion. We previously demonstrated that the PilD prepilin peptidase is crucial for intracellular infection by L. pneumophila and that the secreted pilD-dependent proteins include a metalloprotease...

MMICAJmJOURNAL Summary Evidence is presented that a cytopathic agent isolated from human nose, throat, and bronchial swabs, and termed " Ryan virus" is in fact an amoeba of the genus Hartmannella. Detection of a protozoal cell-type by electron microscopy led to the recognition of typical trophozoites and cysts of this free-living soil amoeba in inoculated tissue cultures. Details are given of c...

BACKGROUND The aim of this study was to compare between slow and rapid sand filters for the removal of free-living amoebae during drinking water treatment production. METHODS Overall, 48 water samples were collected from two drinking water treatment plants having two different filtration systems (slow and rapid sand filters) and from inlet and outlet of each plant. Water samples were collecte...