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

The intracellular pathogens Legionella micdadei and Legionella pneumophila are the two most common Legionella species that cause Legionnaires' disease. Intracellular replication within pulmonary cells is the hallmark of Legionnaires' disease. In the environment, legionellae are parasites of protozoans, and intracellular bacterial replication within protozoans plays a major role in the transmission of Legionnaires' disease. In this study, we characterized the initial host signal transduction mechanisms involved during attachment to and invasion of the protozoan host Hartmannella vermiformis by L. micdadei. Bacterial attachment prior to invasion of H. vermiformis by L. micdadei is associated with tyrosine dephosphorylation of multiple host cell proteins, including a 170-kDa protein. We have previously shown that this 170-kDa protein is the galactose N-acetylgalactosamine (Gal/GalNAc)-inhibitable lectin receptor that mediates attachment to and invasion of H. vermiformis by L. pneumophila. Subsequent bacterial entry targets L. micdadei into a phagosome that is not surrounded by the rough endoplasmic reticulum (RER). In contrast, uptake of L. pneumophila mediated by attachment to the Gal/GalNAc lectin is followed by targeting of the bacterium into an RER-surrounded phagosome. These results indicate that despite similarities in the L. micdadei and L. pneumophila attachment-mediated signal transduction mechanisms in H. vermiformis, the two bacterial species are targeted into morphologically distinct phagosomes in their natural protozoan host.
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PMID:Signal transduction in the protozoan host Hartmannella vermiformis upon attachment and invasion by Legionella micdadei. 972 50

A 42-year-old man was admitted because of fever, productive cough, and progressive dyspnea. Chest x-ray films and computed tomographic scans disclosed dense consolidation in the left and right lung fields. No pathogenic agent was found despite extensive bacteriological examinations. Based on serological findings, the patient was given a diagnosis of acute pneumonia caused by Legionella micdadei. It has been reported that Legionnaire's disease is easily complicated by fatal systemic illnesses such as disseminated intravascular coagulation (DIC) and multiple organ failure. In fact, the patient suffered from severe hypotension and DIC on admission. Treatments against systemic complications were started together with intravenous administration of antibiotics including erythromycin. Continuous intravenous cathecolamin, however, failed to alleviate the patient's shock. We therefore applied endotoxin eliminating therapy using a polymyxin-B-column (PMX) and continuous hemofiltration (CHF). The patient recovered from critical shock immediately after the start of PMX, which together with CHF, alleviated his systemic complications. Although the factors responsible for fatal systemic complications in Legionnare's disease are not well-documented, our findings suggested that some substances removable by PMX and CHF play an important role in pathogenesis.
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PMID:[Severe Legionella micdadei pneumonia effectively treated with hemofiltration therapy]. 989 32

While the majority of Legionnaire's disease has been attributed to Legionella pneumophila, Legionella micdadei can cause a similar infection in immunocompromised people. Consistent with its epidemiological profile, the growth of L. micdadei in cultured macrophages is less robust than that of L. pneumophila. To identify those features of the Legionella spp. which are correlated to efficient growth in macrophages, two approaches were taken. First, a phenotypic analysis compared four clinical isolates of L. micdadei to one well-characterized strain of L. pneumophila. Seven traits previously correlated with the virulence of L. pneumophila were evaluated: infection and replication in cultured macrophages, evasion of phagosome-lysosome fusion, contact-dependent cytotoxicity, sodium sensitivity, osmotic resistance, and conjugal DNA transfer. By nearly every measure, L. micdadei appeared less virulent than L. pneumophila. The surprising exception was L. micdadei 31B, which evaded lysosomes and replicated in macrophages as efficiently as L. pneumophila, despite lacking both contact-dependent cytopathicity and regulated sodium sensitivity. Second, in an attempt to identify virulence factors genetically, an L. pneumophila genomic library was screened for clones which conferred robust intracellular growth on L. micdadei. No such loci were isolated, consistent with the multiple phenotypic differences observed for the two species. Apparently, L. pneumophila and L. micdadei use distinct strategies to colonize alveolar macrophages, causing Legionnaire's disease.
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PMID:Comparative analysis of Legionella pneumophila and Legionella micdadei virulence traits. 1041 84

A 24 year old Saudi housewife was admitted thrice with life threatening community acquired pneumonia. Even though she responded to an initial cocktail of cefriaxone, erythromcin, rifampicin and flucloxacillin during the second admission, she relapsed within four days of discharge when she was on erythromycin only. During the third admission she was put on ceftriaxone and aztreonam and recovered fully without any relapse. Serology results received later showed Legionella IgM titres of more than 1:256 for Legionella micdadei and Legionella bozemanii, and IgG titres of Legionella hackeliae. This case demonstrates relapsing pneumonia due to Legionella micdadei and bozemanii infection, and previous exposure to Legionella hackeliae. Both species, that is, Legionella micdadei and bozemanii, are resistant to erythromycin, but responded very well to a combination of ceftriaxone and aztreonam have not been used previously for the treatment of Legionnaires diseases.
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PMID:Relapsing life threatening community acquired pneumonia due to rare Legionella species responsive to ceftriaxone and aztreonam. 1049 50

In this report, we investigate the intracellular fate of selected members of the genus Legionella within the monocytic cell line Mono Mac 6 cells. By means of electron microscopy and immunocytochemistry, we could show that Legionella pneumophila as well as Legionella longbeachae are able to induce ribosome-studded phagosomes which associate with the rough endoplasmic reticulum (RER), whereas Legionella micdadei remains to be located within smooth phagosomes but also shows signs of RER association. In addition, we could demonstrate a remarkable correlation between the phagosome type and the morphological phenotype of intracellular bacteria: within ribosome-studded phagosomes, bacteria generally lacked the outer coat of low electron density whereas bacteria within the smooth phagosomes still possessed this outer coat. The virulence factors responsible for inhibition of phagosome maturation and their distribution within the genus Legionella as well as the biological significance of the morphological difference of bacteria within smooth and ER-associated phagosomes remain to be investigated.
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PMID:Localization of Legionella bacteria within ribosome-studded phagosomes is not restricted to Legionella pneumophila. 1104 Apr 43

In April 1999, an outbreak of Pontiac fever occurred at a hotel in Northern Sweden. A retrospective cohort study to find the source and define the extent of the outbreak was carried out among 530 Swedish and Norwegian guests. Twenty-nine epidemiological cases (8% of 378 responders) aged 21-57 years were identified. Antibodies against Legionella micdadei were detected in 17 of 27 tested cases and 3 other symptomatic persons. Visiting the whirlpool area was identified as the sole risk factor (RR 86; 95% CI 21-352) and infected cases were confined to visitors to this area over three successive days. The attack rate was 71% (27/38) and 24 cases (83%) used the whirlpool. Environmental sampling was negative for Legionella sp. But epidemiological investigation strongly suggests that the whirlpool was the source of the outbreak. The possibility of serious legionella infections underlines the importance of strict maintenance practices to maintain hygiene of whirlpools.
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PMID:A whirlpool associated outbreak of Pontiac fever at a hotel in Northern Sweden. 1134 75

OBJECTIVE: To compare serologic methods and detection of urinary antigen in the diagnosis of community-acquired pneumonia. METHODS: Paired sera from 84 patients with community-acquired pneumonia were tested for Legionella pneumophila serogroup (LP SG) 1-7 and Legionella micdadei by use of the indirect immunofluorescence antibody test (IIF), enzyme-linked immunosorbent assay (ELISA) for LP SG 1-7 and complement-fixation (CF) test for LP SG 1. All patients were evaluated by ELISA urinary antigen detection for LP SG 1. RESULTS: Seven patients met the CDC criteria for acute Legionella infection, while in the rest of them we failed to detect urinary Legionella antigen. Thirty-three patients had non-diagnostic IIF antibody titers. Serum ELISA (IgG and/or IgM) was positive in 40 patients. Nine patients showed at least one CF titer of >/=1:32. The sensitivities of ELISA IgM for the first and the second serum samples compared with IIF were 42.8% and 46.6%, respectively, while the specificities were higher, i.e. 87% and 88.4%, respectively. The sensitivities of ELISA IgG for the first and the second samples were 42.8% and 53.3%, and the specificities were 77.9% and 76.8%, respectively. CONCLUSIONS: Although ELISA is simple to perform and easy to automate, we think that its advantages over indirect immunofluorescence and urinary antigen detection remain questionable.
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PMID:Comparison of serologic tests with urinary antigen detection for diagnosis of legionnaires' disease in patients with community-acquired pneumonia. 1185 50

A detection system for Legionella DNA in blood samples based on the PCR was developed and evaluated in A/J mice with experimentally induced Legionella pneumonia. Primers were designed to amplify a 106 bp DNA fragment of the 16S rRNA gene specific to Legionella species. The PCR system could detect clinically relevant Legionella species including Legionella pneumophila, Legionella micdadei, Legionella bozemanae, Legionella dumoffii, Legionella longbeachae, Legionella gormanii and Legionella jordanis. The sensitivity of the PCR system was 20 fg extracted DNA. In the mouse model, the blood PCR was compared with results obtained by PCR on bronchoalveolar lavage fluid (BALF) samples, cultures of blood and BALF and detection of Legionella urinary antigen. Blood PCR was positive until 8 days after infection, while BALF PCR became negative on day 4. These results indicate that PCR using blood samples may be a useful, convenient and non-invasive method for the diagnosis of Legionella pneumonia.
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PMID:Detection of Legionella DNA by PCR of whole-blood samples in a mouse model. 1267 71

Legionella is a common cause of community-acquired respiratory tract infections and occasionally causes nosocomial pneumonia. Rapid and accurate detection of legionellae is important for diagnosis and treatment of patients. In order to detect legionellae, a new DNA amplification method was designed and evaluated. Loop-mediated isothermal amplification (LAMP) method amplifies DNA with high specificity, sensitivity, and rapidity under isothermal conditions at 65 degrees C. This method employs a DNA polymerase with strand displacement activity and a set of four specially designed primers that recognize a total of six distinct sequences on the target DNA. The primers targeting 16S rRNA gene were designed in order to detect a wide range of Legionella species. We could specifically detect Legionella species including Legionella pneumophila, Legionella anisa, Legionella bozemanii, Legionella dumoffii, Legionella erythra, Legionella feeleii, Legionella gormanii, Legionella longbeachae, Legionella micdadei, Legionella oakridgensis, and Legionella sainthelensi. The detection limit of the assay was 6 cfu per test of L. pneumophila strain. Furthermore, all of the positive LAMP results could be obtained within 50 minutes. The LAMP method was able to detect a wide range of Legionella species with high specificity, sensitivity, rapidity, and a simple procedure.
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PMID:[Rapid and simple detection of Legionella species by LAMP, a mew DNA amplification method]. 1498 4

Pontiac fever is a non-pneumonic, epidemic form of legionellosis. The symptoms are similar to flu: fever, tiredness, myalgia, arthralgia, headache, cough, sore throat and nausea. The incubation period is from 30 to 90 hours, approx. 36 h., the attack rate is high: 70-90%. There are no differences in sex and age of ill people, the same number of women and men or children were affected. Unfortunately, ill children symptoms might be differ: higher fever (40 C), lack of leukocytosis with left shift, shorten incubation period. The etiological agents are usually bacteria: Legionella pneumophila sg 1, sg 6 and Legionella micdadei. Diagnosis of Pontiac fever is after finding seroconversion or high titre of antibody to Legionella in serum samples or L. pneumophila antigen in urine sample. Pontiac fever cases are frequently found during epidemiological investigation of legionnaires' disease case. Detection of Pontiae fever might be a marker of contaminated with Legionella environment and a risk of live-threatened pneumonia.
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PMID:[Pontiac fever--non-pneumonic legionellosis]. 1502 35


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