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

Legionella pneumophila, in Buffered Yeast Extract broth, was treated for 5 h at 37 degrees C with rosaramicin, erythromycin, cefotaxime, dibekacin, penicillin, methicillin, cefoxitin, cephalothin, ticarcillin, carbenicillin or polymyxin B at near-MIC levels and above. Electronmicroscopy demonstrated morphological changes to the bacteria in some, but not all, of the antibiotic-treated suspensions. Penicillin, at 1000 micrograms/ml (40 X MIC) but not less, produced smooth bubble-like structures on cell surfaces; methicillin produced rough bubble-like structures at 100 micrograms/ml (MIC) but not at 1000 micrograms/ml. In each case, these structures resembled spheroplasts. Polymyxin B induced small-bleb formation on the bacterial cell surfaces at all concentrations tested (MIC-10 X MIC). The other eight antibiotics did not induce any morphological changes at any concentration tested.
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PMID:The effect of antibiotics on the cell morphology of Legionella pneumophila. 303 3

Macrophages can be activated by lipopolysaccharides (LPS) from gram-negative bacteria to evince a number of biological activities, including increased resistance to intracellular infection by opportunistic bacteria. In the present study, intraperitoneal injection of LPS into A/J mice activated peritoneal macrophages so that they resisted subsequent in vitro infection with Legionella pneumophila. Coculture of these macrophages with those from nontreated A/J mice converted the entire population of cells from permissive to nonpermissive. This effect did not appear to be mediated by soluble factors released from the LPS-treated macrophages, since the levels of interleukins-1 and -6 and tumor necrosis factor alpha produced by the macrophages were not found to be markedly elevated at the time when the macrophages from the LPS-treated mice were most effective in converting normal macrophages to nonpermissiveness. Furthermore, macrophages from mice injected intraperitoneally with either interferon or tumor necrosis factor alpha did not evince nonpermissiveness and also did not have the ability to convert normal spleen cells to nonpermissiveness. Polymyxin B, a known inactivator of LPS activity, did not inhibit the macrophages from the LPS-treated mice from inducing this resistance. It seemed unlikely that free LPS released from the macrophages mediated this effect. The results of this study thus showed that macrophages activated by LPS in vivo can evince nonpermissiveness for Legionella growth in vitro and also can induce macrophages from normal, permissive mice to become nonpermissive for Legionella growth in vitro.
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PMID:Legionella pneumophila growth restriction in permissive macrophages cocultured with nonpermissive lipopolysaccharide-activated macrophages. 822 82