Conventional diagnostic tests for legionellosis were negative for a 61-year-old immunocompromised man with pneumonia. However, coculture of a sputum sample with Acanthamoeba polyphaga amoebae led to the recovery of Legionella anisa. This procedure may be a sensitive and convenient diagnostic method, especially for non-Legionella pneumophila species infections that can be diagnosed only by culture.

Free-living amoebae represent a potential reservoir and predator of Salmonella enterica. Through the use of type III secretion system (T3SS) mutants and analysis of transcription of selected T3SS genes, we demonstrated that the Salmonella pathogenicity island 2 is highly induced during S. enterica serovar Typhimurium infection of Acanthamoeba polyphaga and is essential for survival within amoebae.

Here we present the first attempt to quantify Legionella pneumophila cell numbers within individual amoeba hosts that may be released into engineered water systems. The maximum numbers of culturable L. pneumophila cells grown within Acanthamoeba polyphaga and Naegleria fowleri were 1,348 (mean, 329) and 385 (mean, 44) CFU trophozoite(-1), respectively.

Free-living amoebae in water are hosts to many bacterial species living in such an environment. Such an association enables bacteria to select virulence factors and survive in adverse conditions. Waterborne mycobacteria (WBM) are important sources of community- and hospital-acquired outbreaks of nontuberculosis mycobacterial infections. However, the interactions between WBM and free-living amoe...

The recently discovered Acanthamoeba polyphaga Mimivirus is the largest known DNA virus. Its particle size (750 nm), genome length (1.2 million bp) and large gene repertoire (911 protein coding genes) blur the established boundaries between viruses and parasitic cellular organisms. In addition, the analysis of its genome sequence identified many types of genes never before encountered in a viru...

Acanthamoeba is a genus of free-living amoebas distributed worldwide. Few studies have explored the interactions between these protozoa and their infecting giant virus, Acanthamoeba polyphaga mimivirus (APMV). Here we show that, once the amoebal encystment is triggered, trophozoites become significantly resistant to APMV. Otherwise, upon infection, APMV is able to interfere with the expression ...

Acanthamoeba polyphaga Mimivirus is a giant double-stranded DNA virus defining a new genus, the Mimiviridae, among the Nucleo-Cytoplasmic Large DNA Viruses (NCLDV). We used utrastructural studies to shed light on the different steps of the Mimivirus replication cycle: entry via phagocytosis, release of viral DNA into the cell cytoplasm through fusion of viral and vacuolar membranes, and finally...

Most viruses are known for the ability to cause symptomatic diseases in humans and other animals. The discovery of Acanthamoeba polyphaga mimivirus and other giant amoebal viruses revealed a considerable and previously unknown area of uncharacterized viral particles. Giant viruses have been isolated from various environmental samples collected from very distant geographic places, revealing a ub...

When amoebae are simultaneously infected with Acanthamoeba polyphaga Mimivirus (APM) and the strictly intracellular BABL1 bacterium, the latter is always lost after serial subculturing. We showed that the virophage Sputnik 1, by reducing APM fitness, preserved BABL1 growth in acute and chronic models. This capability of a virophage to modulate the virulence of mimiviruses highlights the competi...

A new species of Acanthamoeba was isolated from a freshwater fish in Korea and tentatively named Acanthamoeba sp. YM-4 (Korean isolate YM-4). The trophozoites were 11.0-23.0 micrometer in length and had hyaline filamentous projections. Cysts were similar to those of A. culbertsoni and A. royreba, which were previously designated as Acanthamoeba group III. Acanthamoeba YM-4 can survive at 40 deg...