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

Infection is a serious cause of morbidity and mortality in the cardiac transplant patient. Early infections within the first month after transplantation are usually caused by nosocomial pathogens, such as Pseudomonas aeruginosa, Staphylococcus aureus, Enterococci, and members of Enterobacteriaceae and include pneumonia, urinary-tract and would infections, and bacteremia associated with the use of intravascular devices. Late infections, usually occurring after the first month and within the first year of transplantation, are commonly caused by cytomegalovirus, Pneumocystis carinii, Legionella, and fungi. Because cardiac transplantation has become a well-established treatment for patients with end-stage heart disease, more physicians will be treating these patients and will need to be familiar with the types of infectious complications associated with transplantation.
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PMID:Cardiac transplantation and related infections. 801 80

Legionella pneumophila is an intracellular pathogen replicating in human macrophages during the course of infection of the lungs. Infection by legionellae often leads to severe pneumonia, termed Legionnaires' disease. Genetic approaches to identify the factors responsible for L. pneumophila pathogenicity started with the construction of genomic libraries in Escherichia coli. Various L. pneumophila-specific genes were cloned in E. coli K-12 by identification using functional assays, antibody screening and hybridization ('reverse genetics'). By disrupting the genes via allelic exchange, mutants have been created to assess the influence of the factors on pathogenicity. Among the cloned genes, only for the gene product of the mip gene, encoding a 24-kDa surface-associated protein (macrophage infectivity potentiator) unequivocal evidence for its contribution to pathogenicity could be provided. Two hemolytic factors that have been cloned do not seem to play a role in L. pneumophila pathogenicity. Genetic systems for transposon mutagenesis of the L. pneumophila genome (Tn5, Tn903dIIlacZ, MudphoA), including Tn phoA shuttle mutagenesis, have been established and specifically adapted to identify mutants which displayed an impaired capability to multiply inside macrophages and with a reduced in vivo virulence. Furthermore, by complementation of avirulent mutants, genetic loci could be identified which restored the virulence.
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PMID:Genetic approaches to study Legionella pneumophila pathogenicity. 804 98

Infection of macrophages with Legionella pneumophila induces formation of interleukin 1 beta (IL-1 beta), but the molecular basis of this is not understood. Binding of bacteria to macrophage surfaces is the first step in an infection process. Therefore, we examined whether this step was sufficient to increase the cellular level of mRNAs for IL-1 beta and other cytokines. To assess the effect of binding of L. pneumophila on the steady-state levels of cytokine mRNAs, cultures of thioglycolate-elicited macrophages from L. pneumophila-susceptible A/J mice were treated with cytochalasin D and infected with L. pneumophila and the total RNA was extracted for analysis by reverse transcription-PCR with primers for IL-1 alpha, IL-1 beta, IL-6, tumor necrosis factor alpha, granulocyte macrophage colony-stimulating factor, and beta interferon (IFN-beta). L. pneumophila treatment increased the cellular steady-state mRNA levels of all cytokines except IFN-beta. To determine the specificity of this effect, macrophage cultures were treated with cytochalasin D and either bacterial lipopolysaccharide, bovine serum albumin-sensitized latex, Salmonella typhimurium, or Escherichia coli. Lipopolysaccharide treatment increased all mRNAs, bovine serum albumin-sensitized latex had no significant effect, and treatment with S. typhimurium or E. coli increased all mRNAs except that of IFN-beta. These results suggested that the binding of gram-negative bacteria to the macrophage surface was sufficient to induce a unique pattern of cytokine mRNAs. Additional studies that examined the characteristics of the bacterial ligands involved indicated involvement of both heat-labile and heat-stable surface ligands.
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PMID:Binding of Legionella pneumophila to macrophages increases cellular cytokine mRNA. 806 12

Legionella pneumophila may subvert monocyte defenses by several mechanisms including the inhibition of phagosome-lysosome fusion or the impairment of oxidative metabolism. We have investigated the effect of L. pneumophila Knoxville 1, a virulent strain that does not inhibit phagosome-lysosome fusion, on the oxidative responsiveness of human monocytes. Infection of monocytes with L. pneumophila for 48 h resulted in marked inhibition of superoxide generation stimulated by phorbol myristate acetate (PMA) but not by zymosan, a particulate agonist. Evidence is provided that L. pneumophila interfered with the transductional pathway (i.e., protein kinase C, PKC) leading to activation of the NADPH oxidase in monocytes. The phosphorylation of 34-, 48-, 62-, 68-, and 80-kDa proteins stimulated by PMA was markedly inhibited in infected monocytes. In addition, the expression of both alpha and beta PKC isotypes was partially inhibited in infected monocytes. Taken together, our data suggest that the down-modulation of PKC isotypes plays a role in the inhibition of PMA-stimulated superoxide generation.
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PMID:Legionella pneumophila inhibits superoxide generation in human monocytes via the down-modulation of alpha and beta protein kinase C isotypes. 812 Apr 47

Ten patients from a rehabilitation center were admitted to hospital with serious respiratory infections within ten weeks. An outbreak of Legionnaire's disease was suspected based on the epidemic and atypical manifestation of pneumonia and could be proven microbiologically. Pulmonary and extrapulmonary complications included respiratory failure, lung abscess, transitory renal impairment in five patients and acute renal failure requiring dialysis in one, tetraparesis caused by peripheral neuropathy and acute psychosis. Three patients died despite immediate institution of therapy with erythromycin. Legionella pneumophila serogroup 1 subtype Pontiac was isolated from a bronchial lavage sample of one patient and from the water supply of the rehabilitation center. Monoclonal antibody subtyping and restriction endonuclease analysis were performed on both environmental and patient isolates. Potable water was identified as the source of the outbreak based on identical patterns on restriction endonuclease analysis. Despite thermic and chemical disinfection with chlorination (up to 15 ppm) in the rehabilitation clinic, an eleventh case of Legionnaire's disease was detected 11 months later.
Infection
PMID:Nosocomial outbreak of legionellosis in a rehabilitation center. Demonstration of potable water as a source. 822 27

In most cases of respiratory tract infection, antibiotic therapy has to be initiated before the results of microbiological examination are available. The four most common pathogens of acute exacerbations of chronic bronchitis are pneumococci, Haemophilus influenzae, Moraxella catarrhalis and Staphylococcus aureus. Pneumococci are the predominant pathogens of community-acquired pneumonia, followed by H. influenzae and staphylococci. Legionella, mycoplasma and chlamydia vary in frequency according to the population studied. Staphylococci, Pseudomonas, Enterobacter and Klebsiella spp. as well as H. influenzae are the major pathogens of secondary pneumonia. For reasons of cost and environmental problems, oral antibiotics ought to be used whenever possible considering the severity of the infection and patient circumstance. Parenteral antibiotics are indicated in severe infections in order to provide high therapeutic drug levels. Second generation cephalosporins are appropriate for initial therapy of lower respiratory tract infections. In case of severe infection, cephalosporins should be combined with an aminoglycoside, ureidopenicillin or quinolone. Cefuroxime has shown good clinical efficacy and tolerance in lower respiratory tract infections.
Infection 1993
PMID:[Parenteral cephalosporins for the treatment of lower respiratory tract infections]. 831 90

The ability of an opportunistic intracellular bacterial pathogen, Legionella pneumophila, to induce tumor necrosis factor (TNF) in macrophages from susceptible A/J or resistant BDF1 and BALB/c mice was determined. Cultures of peritoneal elicited macrophages from these mouse strains produced TNF in response to the Legionella. The TNF levels produced by the macrophages stimulated with either heat-killed Legionella vaccine or lipopolysaccharide were similar and dose dependent, although the amount of TNF produced by macrophages from permissive A/J mice was 2- to 4-fold higher than that produced by macrophages from the nonpermissive mice. Similar differences in TNF levels occurred when macrophages from either permissive or non-permissive mice were infected with viable Legionella. The TNF levels produced by the A/J mouse macrophages increased as a function of time after infection, with a peak of activity on Day 1 or 2, depending upon the initial concentration of the bacteria. Infection of the A/J mouse macrophages with avirulent Legionella resulted in induced levels comparable to those induced by a virulent strain. Although it is widely believed that TNF production by mouse macrophages is related to resistance to infections, the results of this study did not show a relationship between TNF production by macrophages in vitro and resistance versus susceptibility of the macrophage donor mouse strain to Legionella infection.
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PMID:Legionella pneumophila induced tumor necrosis factor production in permissive versus nonpermissive macrophages. 847 35

Respiratory infections, especially community-acquired forms of pneumonia (CAP), are challenging for clinicians because (1) a causative microorganism can only be found in about 50% of cases; (2) initial therapy, therefore, must be based on a probable or most likely etiology in the context of the patient's overall medical condition; and (3) new microbes or those considered previously as normal flora or less virulent forms seem responsible for some cases. It is important to be acquainted with new causes of infection which include Legionella species, Chlamydia pneumoniae, diphtheroids in certain instances (Corynebacterium pseudodiphtheriticum), and viruses such as the Hanta strains. Infections with Bordetella pertussis are increasing. However, the ever present and most common cause of CAP, Streptococcus pneumoniae, continues to present problems because of increasing antibiotic resistance, the high case fatality rate when bacteremia accompanies pneumonia, and the inability to give prophylactic immunization to all people with risk factors for this infection.
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PMID:Respiratory infections: community-acquired pneumonia and newer microbes. 879 Dec 58

We prospectively studied the etiology of community-acquired pneumonia among all patients who were admitted to our hospital from July 1994 to June 1995. Tests for microbial pathogens including Chlamydia spp. and Legionella spp. were performed and diagnoses were made with strict criteria. A total 110 patients with 111 episodes of pneumonia were evaluated, and a pathogen was identified in 61 episodes (55%). The most common pathogen was Streptococcus pneumoniae (18%), followed by Haemophilus influenzae, Klebsiella pneumoniae, Pseudomonas aeruginosa, Mycoplasma pneumoniae, and Chlamydia spp. Infection with Legionella pneumophila was not found. Dual pathogens were identified in five episodes. Few prospective studies of the etiology of community-acquired pneumonia have been done in Japan. To prepare guidelines for the management of community-acquired pneumonia in Japan, a national study of the etiology of pneumonia is necessary.
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PMID:[Prospective study of the etiology of community-acquired pneumonia among patients in a general hospital]. 881 Jul 56

We reviewed 10 cases of culture proven legionellosis that occurred at a marrow transplant center (Fred Hutchinson Cancer Research Center, Seattle, WA, USA) over a 6-year period ending in 1993. Infections were caused by four species of Legionella with no apparent clustering of cases. Detection of Legionella using direct fluorescent antibody assays proved unreliable due to the high proportion of rare Legionella species isolated. The clinical presentation, course and outcome of patients varied and did not correlate with underlying disease, type of transplant, transplant day or engraftment status. However, five of the seven patients infected with non-pneumophila species recovered from their pneumonia compared to none of the three patients infected with L. pneumophila. Persistent or relapsed infection after 3 weeks of appropriate therapy was documented in one case suggesting that prolonged antibiotic treatment is indicated in these patients.
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PMID:Legionellosis in a bone marrow transplant center. 886 47


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