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

A model of intracellular growth for Legionella pneumophila in Acanthamoeba castellanii has been developed and provides a quantitative measure of survival and replication after entry. In this model, Acanthamoeba monolayers were incubated with bacteria in tissue culture plates under nutrient-limiting conditions. Gentamicin was used to kill extracellular bacteria following the period of incubation, and the number of intracellular bacteria was determined following lysis of amebae. Intracellular growth of virulent L. pneumophila and other wild-type Legionella species was observed when the assay was performed at 37 degrees C. At room temperature, none of the Legionella strains tested grew intracellularly, while an avirulent L. pneumophila strain was unable to replicate in this assay at either temperature. The effect of nutrient limitation on A. castellanii during the assay prevented multiplication of the amebae and increased the level of infection by Legionella spp. The level of infection of the amebae was directly proportional to the multiplicity of infection with bacteria; at an inoculum of 1.03 x 10(7) bacteria added to wells containing 1.10 x 10(5) amebae (multiplicity of infection of 100), approximately 4.4% of A. castellanii cells became infected. Cytochalasin D reduced the uptake of bacteria by the amebae primarily by causing amebae to lift off the culture dish, reducing the number of target hosts; methylamine also reduced the level of initial infection, yet neither inhibitor was able to prevent intracellular replication of Legionella spp. Consequently, once the bacteria entered the cell, only lowered temperature could restrict replication. This model of intracellular growth provides a one-step growth curve and should be useful to study the molecular basis of the host-parasite interaction.
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PMID:A quantitative model of intracellular growth of Legionella pneumophila in Acanthamoeba castellanii. 172 91

The effect of 14 antimicrobial agents, including new quinolones and a new macrolide, on the intracellular multiplication of Legionella pneumophila in cultured guinea pig peritoneal macrophages was examined. Gentamicin and beta-lactam antibiotics did not inhibit the intracellular growth of L. pneumophila. Minocycline, erythromycin and DR-3355 inhibited multiplication at concentrations of 1, 0.5 and 0.1 mg/l respectively. Rifampicin, the new macrolide roxithromycin, and the new quinolones ofloxacin, ciprofloxacin and AT-4140 all inhibited the intracellular growth of L. pneumophila at concentrations of less than 0.03 mg/l. The minimal extracellular concentration inhibiting intracellular multiplication (MIEC), compared with conventional MIC measurements, provides a better indication of antimicrobial efficacy against bacteria, such as L. pneumophila, which can multiply in phagocytes.
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PMID:Inhibition of Legionella pneumophila in guinea pig peritoneal macrophages by new quinolone, macrolide and other antimicrobial agents. 203 40

The penetration and persistence in the serum and lungs of guinea pigs after parenteral administration of erythromycin, gentamicin, chloramphenicol and rifampicin, and their in-vitro activities against Legionella pneumophila were investigated. The most active agent was rifampicin (MIC 0.0625 mg/l, MBC 0.125 mg/l) and effective levels of this drug were present in serum and lungs up to 10 h after injection. Erythromycin accumulated to very high levels in the lungs and had good bacteriostatic activity in vitro. Gentamicin was highly bactericidal in liquid culture but showed poor lung penetration on injection. Chloramphenicol, the least inhibitory of the four antibiotics, had an MIC of 1.0 mg/l. Active chloramphenicol was not detected in guinea pig serum and lungs following ip or im administration. The differences in the penetration and persistence of these drugs in the lungs of guinea pigs may explain the reported poor correlation between in-vitro and in-vivo activity against L. pneumophila. The results are useful for evaluating regimens for therapy of Legionnaires' disease in the aerosol infected guinea pig model.
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PMID:Persistence in serum and lungs of guinea pigs of erythromycin, gentamicin, chloramphenicol and rifampicin and their in-vitro activities against Legionella pneumophila. 663 Jan 6

The effect of antimicrobial agents on the intracellular multiplication of Legionella pneumophila in cultured guinea-pig peritoneal macrophages was measured. Beta-lactam antibiotics at concentrations 5 to 400 times the MIC in vitro did not inhibit the intracellular growth of the organism. Gentamicin inhibited the growth considerably but failed to eliminate the organism from the phagocytic mixture. Chloramphenicol or tetracycline at 10 micrograms ml-1 (40 or 5 times the MIC in vitro respectively) did not eliminate the organism. At a higher concentration (30 micrograms ml-1), however, these drugs eliminated the bacterium from the mixture. Only erythromycin and rifampin were effective in killing the organism at very low concentration (1 microgram ml-1). Intracellular multiplication of L. pneumophila was observed clearly by light microscopy using Wright-Giemsa staining.
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PMID:Antibiotic susceptibility of Legionella pneumophia Philadelphia-1 in cultured guinea-pig peritoneal macrophages. 673 22