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

Legionella pneumophila, the causative agent of legionellosis, is an intracellular parasite of human monocytic cells and neutrophils. The life cycle of Legionella within phagocytic cells is distinct from that of other bacterial pathogens. Adherence of L pneumophila to phagocytes is mediated by attachment of complement proteins to the Legionella cell surface, followed by binding to complement receptors of phagocytes. Opsonized Legionella also may enter phagocytes after engagement of the Fc receptors. Within the host cell, the parasites reside in a membrane-bound vacuole that does not fuse with lysosomes. Activation of mononuclear phagocytes by the cell-mediated immune system serves to limit intracellular bacterial growth. Polymorphonuclear leukocytes are better at killing L pneumophila than are macrophages. However, Legionella also can invade and parasitize granulocytes. Although significant progress has been made in understanding some aspects of the pathogenesis of legionellosis, we know very little about the mechanisms by which these facultative intracellular parasites avoid killing by host defense mechanisms. This is an important area for future research and should lead to a better understanding of host-parasite interactions.
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PMID:Legionella pneumophila: denizen of defenders. 188 68

A serologic survey of antibodies to Legionella pneumophila serogroups 1 through 6 was performed to assess the prevalence of positive antibody titers among outpatients and to evaluate the association between elevated antibody titers and previously identified risk factors for legionellosis. Subjects were recruited from outpatient clinics at the Minneapolis VA Medical Center. Each participant completed a self-administered questionnaire which asked about their general health and any recent symptoms of illness. Medical records were also audited for all participants to provide additional information on medical history and known risk factors for Legionella infection. Single samples of serum were obtained from each subject, and antibody titers to L pneumophila serogroups 1 through 6 were assayed. Three hundred ninety-six subjects were enrolled in the study. They had a mean age of 67 years, and 98 percent were male subjects. Overall, 36 percent of the subjects had positive antibody titers (greater than or equal to 1:128) to L pneumophila. There were no differences between those with and without elevated titers with respect to recent systemic symptoms or other previously established risk factors for legionellosis. We conclude that positive anti-Legionella antibodies are a frequent occurrence among these outpatients. This has important implications for the interpretation of single or static antibody titers from patients who are acutely ill.
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PMID:High prevalence of positive antibodies to Legionella pneumophila among outpatients. 188 52

The purpose of this study was to evaluate the L-CLONE Legionella pneumophila Serogroup 1 Urine Antigen Latex Test (Access Medical Systems, Inc., Branford, Conn.) for detection of Legionella antigen in urine. A total of 481 frozen urine samples previously tested by an in-house solid-phase radioimmunoassay (RIA) was thawed and retested by using L-CLONE. Included in this sample were 140 RIA-positive samples from culture-positive or serologically confirmed cases of legionellosis and 341 RIA-negative samples from patients with non-Legionella respiratory disease or bacteriuria. The original RIA test result was accepted as the true value. L-CLONE correctly identified 76 of 140 (54%) known positive samples. False-negative results could not be attributed to a low Legionella antigen concentration or to a Legionella antigen subgroup. L-CLONE correctly identified 252 of 341 (74%) known negative samples. False-positive results were experienced in all groups of negative samples, regardless of the patients' underlying diseases. A total of 141 fresh urine samples was tested; all were Legionella antigen negative by RIA. L-CLONE provided 86% specificity. The sensitivity of the L-CLONE in testing fresh urine samples could not be evaluated because of the lack of Legionella antigen RIA-positive samples.
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PMID:Evaluation of the L-CLONE Legionella pneumophila Serogroup 1 Urine Antigen Latex Test. 193 74

In the process of protein kinase reaction carried out in the mixture consisting of tris-HCl buffer, EDTA, MgCl2, gamma-32P-ATP and the cytoplasmic fraction of rabbit pulmonary cells the phosphorylation of proteins with molecular weights of 150 and 55 kD took place. The addition of L. pneumophila culture fluid to the reaction mixture resulted in the splitting of phosphorylated proteins with the formation of the component having a molecular weight of 45 kD. These disturbances in protein kinase reaction were found to occur due to the involvement of Legionella cytoplasm, a previously characterized protein with a molecular weight of 37 kD, into the process. In this connection, the participation of cytolysin in the pathogenesis of Legionella infection may also be considered from the viewpoint of the effect produced by cytolysin on the regulatory processes affecting the metabolism of target cells.
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PMID:[The splitting of the acceptor proteins of the protein kinase system in eukaryotic cells by Legionella cytolysin]. 195 Feb 77

Following a statewide outbreak of legionellosis due to Legionella longbeachae serogroup 1 in South Australia in 1988 and 1989, studies were performed to find a source of the organism. A number of water and soil samples with and without acid decontamination were examined for L. longbeachae by using a selective medium containing vancomycin, aztreonam, and pimafucin. There were no isolations of L. longbeachae from water samples. Organisms resembling L. longbeachae were isolated from a number of samples of potting mixes and from soil surrounding plants in pots collected from the homes of four patients. The organisms were found to persist for 7 months in two potting mixes stored at room temperature. Legionellae were isolated with difficulty from potting mixes which were allowed to dry out. Identification of isolates as L. longbeachae serogroup 1 was confirmed by quantitative DNA hybridization and serological tests. Restriction-fragment-length-polymorphism studies showed minor differences between patient and environmental isolates but differentiated these readily from L. longbeachae serogroup 2 and other antigenically related legionellae. The isolation of L. longbeachae from some potting mixes and the prolonged survival of the organisms in this medium suggest that soil rather than water is the natural habitat of this species and may be the source of human infections.
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PMID:Isolation of Legionella longbeachae serogroup 1 from potting mixes. 196 36

We studied, in a prospective way, the characteristics of definitively diagnosed nosocomially acquired pneumonias in our hospital over 36 months. Out of 55 cases, 27 were due to Legionella pneumophila and 28 to other, non-Legionella bacteria. The cases of legionellosis concentrated in July, August, and December. The only risk factors that showed significant differences (p less than 0.05) were general anesthesia and surgery and immunosuppressive disease, which were more frequent in the non-Legionella group, as were chronic liver disease and lowering of consciousness level. The absence of severe underlying disease, chronic or not, was uncommon in both groups, but more frequent in the Legionella group. We observed no differences in the clinical features of the two groups. Mean values of gamma-glutamyltranspeptidase and total bilirubin were higher (p less than 0.05) in the non-Legionella group. The only x-ray data that showed significant difference were pleural effusion, more frequent in the non-Legionella group (p less than 0.02). The mortality rate of legionellosis was 14.6 percent compared to 35.7 percent for the non-Legionella group (p less than 0.05). We conclude that a sure differential diagnosis based on clinical, roentgenographic and analytical features of both groups is not possible. The relatively low mortality rate of the Legionella group, when compared to other series of nosocomial legionellosis, could be due to the standard use of erythromycin in the therapeutic approach to nosocomial-acquired pneumonia in our hospital.
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PMID:Comparative study of Legionella pneumophila and other nosocomial-acquired pneumonias. 198 93

During 1985 in the Hadassah University Hospital we studied all hospitalized patients whose serum had been submitted for Legionella antibodies. Of 133 patients, 12 (9%) had legionellosis as diagnosed by serology, direct fluorescence, or culture. All Legionella cases appeared to be sporadic, nonseasonal, community-acquired pneumonia. There were no specific environmental co-factors or clustering. A significant predilection of the disease for immunosuppressed individuals was observed; the in-hospital mortality was high (5/12), especially if erythromycin therapy was delayed. L. pneumophila and L. bozemanii were the dominant etiological species. In Jerusalem, Legionella is not infrequently the etiological agent in community-acquired pneumonia in immunosuppressed patients.
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PMID:Legionellosis at Hadassah University Hospital: a 1-year survey. 201 54

Seventeen suspension of Legionella pneumophila and ten of Legionella bozemanii in saline or bronchoalveolar lavage (BAL) fluid were tested using the Gen Probe technique. The detection threshold was found to be 10(3)-10(4) CFU/ml. Specificity and sensitivity were evaluated by using the probe on 8 suspensions of bacteria other than Legionella and by performing a comparative study of the probe test, direct immunofluorescence and culture with 103 specimens (BAL fluid in most instances) from 92 patients with possible legionellosis. Sensitivity was found to be acceptable (3 of the 4 culture-positive specimens were positive by the probe test) and specificity was 100% despite the fact that most (80/99) BAL specimens were not sterile and regardless of the cutoff level used to define positivity. The advantages of the DNA probe test, including rapidity, simplicity and objectivity, should be weighed against its disadvantage, i.e., only acceptable sensitivity and use of radioactivity.
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PMID:[Evaluation of a DNA probe test for the detection of Legionella SPP]. 201 40

The authors report a nonradioactive adaptation of DNA hybridization technology for the direct detection of Legionella organisms in situ in routinely processed histologic specimens. The probe used consisted of synthetic oligodeoxynucleotides, complementary to the ribosomal RNA of all clinically relevant Legionella species, labeled with biotinylated dUTP at their 3' ends. By in situ DNA hybridization and detection with an avidin-alkaline phosphatase complex. Legionella was visualized by light microscopy within the alveoli of lung specimens in 9 of 13 direct fluorescent antibody- or culture-positive cases of Legionnaires' disease. No cross-hybridization was observed in lung specimens infected with Pseudomonas aeruginosa, Klebsiella pneumoniae, Streptococcus pneumoniae, or other pathogens. The authors' results illustrate a novel adaptation of in situ DNA hybridization techniques, usually used for viruses, to the detection of a bacterial organism. The method enables direct visualization of bacterial nucleic acid in infected tissues and may facilitate early diagnosis and treatment of legionellosis.
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PMID:Rapid diagnosis of Legionella infection by a nonisotopic in situ hybridization method. 202 27

The detection of antigens is the most important tool for rapid diagnosis of Legionellosis. 34 Legionella (L.) spp. with 51 serogroups have been identified from several sources. According to the antigenic diversity, it is necessary to select monoclonal antibodies (mab) adequate to diagnostic purposes. Mab with specificity to genus, species and serogroups were discussed. L. pneumophila accounts for 70 to 80% of all cases of Legionelloses. In this study self-made mab to L. pneumophila are presented that demonstrate these bacteria in clinical materials from respiratory tract using immunofluorescent tests and by detection of soluble antigens in pleura fluids and urine specimens using enzyme immunoassay.
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PMID:[Determination of Legionella antigens using monoclonal antibodies]. 203 89


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