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Query: UMLS:C0023241 (Legionella)
 6,990 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The authors report a case of pneumonitis in a young healthy man caused by coinfection with human herpesvirus 6 (HHV-6) and Legionella pneumophila. The patient's course was complicated by severe respiratory, renal, hepatic, and central nervous system dysfunctions, which were believed to be primarily the results of his Legionella infection. Aggressive antibiotic treatment produced no response, and Legionella remained isolatable from lung tissue throughout several weeks of antimicrobial therapy. Human herpesvirus 6 was isolated from a sample of peripheral blood during the acute stage of the patient's illness, and numerous HHV-6--infected macrophages and lymphocytes were detected by immunohistochemical staining of biopsy-derived lung tissue. Paradoxically treatment of the patient with high-dose corticosteroids resulted in dramatic improvement of his condition, including clearance of the Legionella infection. The demonstration that corticosteroids efficiently inhibit HHV-6 replication in vitro suggests that the virus may have contributed to the patient's pneumonitis by enhancing tissue inflammation, by compromising the function of pulmonary macrophages, and, perhaps, by destroying the patient's CD4+ T lymphocytes. Human herpesvirus 6 may be able to function as a synergistic cofactor in lung infections by Legionella and other pathogens.
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PMID:Pneumonitis associated with coinfection by human herpesvirus 6 and Legionella in an immunocompetent adult. 164 38

Legionella pneumophila is the intracellular bacterial pathogen that causes severe Legionnaires' disease and flu-like Pontiac fever. To accomplish successful aggression against hosts, L. pneumophila secrets more than 150 kinds of substrate effector proteins into host cells via its Type IVB secretion system. With the multiple functions of effectors, L. pneumophila evades effectively the defense systems of hosts, converts or adjusts intracellular vesicular transport of hosts, modifies or disguises its Legionella containing vacuole (LCV), modulates the cell cycle program and inhibits the apoptosis of host cells, and finally gains the comfortable intracellular replicative niche. Effectors can also help L. pneumophila escape from hosts cells after completing the proliferation.. L. pneumophila has became the distinct model for pathogen-host interaction research, and its secretion systems as well as the substrate effectors are attracting more and more attentions. Researching on T4BSS and effectors could not only help investigate the pathogenesis of intracellular bacterial pathogens, but also promote the comprehension about innate immune responses of hosts. This article reviews the progresses of L. pneumophila T4BSS and effectors, trying to demonstrate to the readers the cunning survival strategy and the delicate virulent machine of L. pneumophila.
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PMID:[The lethiferous journey of a bacterium--the research progress of secretion systems and effectors in Legionella pneumophila]. 2199 84