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

We evaluated the in vitro susceptibility of Legionella pneumophila ATCC 33152 (serogroup I) to 13 antibiotics alone and in combination with rifampin (0.1 mg/liter) by three methods. Extracellular susceptibility was determined by MIC determinations and time kill curves in buffered yeast extract broth, while intracellular susceptibility was determined by peripheral human monocytes in RPMI 1640 culture medium. Antibiotic concentrations equal to or greater than the broth dilution MIC inhibited or killed L. pneumophila by the time kill method, except this was not the case for trimethoprim-sulfamethoxazole. Antibiotic concentrations below the broth dilution MIC did not inhibit Legionella growth. The only antibiotic-rifampin combinations which produced improved killing of L. pneumophila by the time kill method were those in which the logarithmic growth of L. pneumophila occurred during the experiment (rosoxacin, amifloxacin, cinoxacin, trimethoprim-sulfamethoxazole, clindamycin, and doxycycline). Neither direct MICs nor time kill curve assays accurately predicted intracellular L. pneumophila susceptibility. Rifampin, erythromycin, ciprofloxacin, rosoxacin, enoxacin, amifloxacin, gentamicin, clindamycin, and doxycycline all inhibited intracellular L. pneumophila growth at readily achievable concentrations in serum. Cefoxitin and thienamycin showed no inhibition of growth, although they were present extracellularly at concentrations that were 20 to 1,000 times their broth dilution MICs. Clindamycin was the only antibiotic that was able to inhibit intracellular L. pneumophila growth at an extracellular concentration below its MIC. The gentamicin (5 mg/liter)-rifampin combination was the only antibiotic-rifampin combination which demonstrated decreased cell-associated Legionella survival in this model of in vitro susceptibility.
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PMID:Effect of quinolones and other antimicrobial agents on cell-associated Legionella pneumophila. 343 1

The activity of serial concentrations of different antimicrobial agents on the multiplication of Legionella pneumophila within human monocyte-derived macrophages was studied. The results led to the definition of a minimal extracellular concentration inhibiting intracellular multiplication (MIEC). According to the MIECs, the antimicrobial agents tested were classified in three groups: very active (MIEC less than or equal to 0.06 microgram/ml), such as erythromycin, rifampin, and pefloxacin; active (1 microgram/ml greater than or equal to MIEC greater than or equal to 0.1 microgram/ml), such as sulfamethoxazole-trimethoprim or doxycycline; and ineffective, such as cefoxitin, which was not active within macrophages at as high as 64 micrograms/ml despite a low MIC (0.2 microgram/ml) on bacterial charcoal-yeast extract agar. The activity of netilmicin was difficult to assess because of its effect on extracellular legionellae. Combinations of erythromycin with rifampin and pefloxacin with erythromycin, rifampin, doxycycline, or netilmicin showed an additive effect and no antagonism. These results obtained in a cellular model are in agreement with the efficacy of antimicrobial agents in experimental infections and in Legionnaires disease. They sustain clinical interest in the new quinolones, such as pefloxacin, and in combinations of antimicrobial agents for the treatment of Legionnaires disease.
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PMID:Inhibition of Legionella pneumophila multiplication within human macrophages by antimicrobial agents. 349 76

The in vitro activity of a new penem antimicrobial agent, CGP 31608, was compared with those of imipenem, SCH 34343, and several other antimicrobial agents against approximately 600 bacterial isolates. CGP 31608 was active against gram-positive organisms, including methicillin-susceptible Staphylococcus aureus (MIC for 90% of the isolates [MIC90], 0.25 microgram/ml) and penicillin-susceptible streptococci (MIC90s, less than or equal to 2 micrograms/ml). Penicillin-resistant streptococci (including enterococci) and methicillin-resistant S. aureus were more resistant to the penem. Activities of CGP 31608 against members of the family Enterobacteriaceae were remarkably uniform, with MIC90s of 8 to 16 micrograms/ml. CGP 31608 was at least as active as imipenem and ceftazidime and more active than piperacillin against Pseudomonas aeruginosa. Drug activity was not influenced by the presence of any of 10 plasmid-mediated beta-lactamases. Against strains of Serratia marcescens, Enterobacter cloacae, and P. aeruginosa with derepressible chromosomally mediated beta-lactamases, the presence of cefoxitin did not induce increased resistance to CGP 31608. The new drug was also active against anaerobes (MIC90s, 0.25 to 8 micrograms/ml), Haemophilus influenzae (MIC90s, 0.5 to 1.0 micrograms/ml), and Legionella spp. (MIC90, 2 micrograms/ml). CGP 31608 showed an antibacterial spectrum similar to those of imipenem and SCH 34343 (except that the latter is not active against P. aeruginosa) but was generally less potent than these drugs. However, CGP 31608 demonstrated more activity (MIC90) than imipenem against P. aeruginosa, Pseudomonas cepacia, and methicillin-resistant Staphylococcus epidermidis and S. aureus.
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PMID:Comparative in vitro activity of CGP 31608, a new penem antibiotic. 349 37

The morphological response of two strains of Legionella pneumophila to ampicillin 10 micrograms/ml and erythromycin 10 micrograms/ml in vitro was studied by electronmicroscopy, MIC estimations and viable counts. In the presence of ampicillin, discrete lesions appeared in the bacterial cell walls through which cytoplasmic contents extruded and lysis occurred. A few spheroplasts, together with minicells of 0.15-micron diameter, and apparently normal cells were present after exposure to ampicillin for several hours. Conversely, erythromycin initially resulted in inhibition of division and the formation of filamentous organisms. The cell walls of these filaments were eventually disrupted with numerous small membranous vesicles appearing on their surfaces. On further erythromycin treatment, breakage of the cell wall at a restricted number of sites occurred, leading to cell lysis. In the presence of erythromycin, a few morphologically normal cells were present but no spheroplasts or minicells were observed. Viable counts demonstrated that ampicillin killed the bacteria faster than erythromycin. Regrowth did not occur in the continued presence of either antibiotic, but after their removal regrowth was observed.
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PMID:Morphological response and growth characteristics of Legionella pneumophila exposed to ampicillin and erythromycin. 400 91

Ninety patients with serious infections, including 61 with septicaemia, pneumonia, peritonitis or meningitis, were treated with ceftazidime. Of these patients, 85.6% were clinically cured (73.3%) or improved (12.2%) by the antibiotic. In this study, 57.7% had infections due to Escherichia coli (24.7%), Klebsiella sp. (14.5%) and Pseudomonas sp. (18.5%). Two children with cystic fibrosis and Pseudomonas pneumonia and an adult with Legionella pneumonia responded well to ceftazidime treatment. Seventy patients had fever before treatment and most of them became apyrexial in less than 2 to 3 days. Ceftazidime was given either intramuscularly (42 patients) or intravenously (48 patients), in a dose of 1 g tds in 71 patients or 2 g tds in severe infections in 11 patients, or reduced to suit the renal function (7 patients) or in paediatric doses (2 children). Blood ceftazidime levels were measured in eight patients with normal renal function. The average level one hour post dosing was 45.2 mg/l and the average trough level was 8.1 mg/l. Six patients were suffering from variable degrees of renal insufficiency (serum creatinine 149 to 668 mmol/l). Their average blood level 1 h post-dosing was 68.8 mg/l. In a patient with meningitis, the CSF level was 2.4 mg/l 2 h after a 1 g dose. These levels are several times the ceftazidime MIC values for most clinical bacterial isolates. Ceftazidime is a valuable and safe alternative to aminoglycoside therapy.
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PMID:Ceftazidime: a new approach in the treatment of moderate and severe infections. 635 15

Disk diffusion antimicrobial susceptibility testing of members of the family Legionellaceae was accomplished on buffered charcoal yeast extract agar by allowing the bacteria to grow for 6 h before placement of the disks, followed by an additional 42-h incubation period before the inhibitory zones were measured. This system was standardized by comparing the zone sizes with the MICs for 20 antimicrobial agents of nine bacterial strains in five Legionella species and of 19 laboratory-derived, erythromycin-resistant variants of Legionella micdadei. A high, linear correlation between zone size and MIC was found for erythromycin, trimethoprim, penicillin, ampicillin, carbenicillin, cephalothin, cefamandole, cefoxitin, moxalactam, chloramphenicol, vancomycin, and clindamycin. Disk susceptibility testing could be employed to screen Legionella isolates for resistance to any of these antimicrobial agents, of which only erythromycin is known to be efficacious in the treatment of legionellosis. With selected antibiotics, disk susceptibility patterns also appeared to accurately identify to the species level the legionellae. The range of the MICs of the legionellae for rifampin and the aminoglycosides was too small to determine whether the correlation of zone size with MIC was linear. However, laboratory-derived, high-level rifampin-resistant variants of L. micdadei demonstrated no inhibition zone around the rifampin disk, indicating that disk susceptibility testing would likely identify a rifampin-resistant clinical isolate. Of the antimicrobial agents tested, the only agents for which disk susceptibility testing was definitely not possible on buffered charcoal yeast extract agar were oxacillin, the tetracyclines, and the sulfonamides.
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PMID:Disk diffusion antimicrobial susceptibility testing of members of the family Legionellaceae including erythromycin-resistant variants of Legionella micdadei. 656 6

With 28 beta-lactam antibiotics the susceptibilities of 60 strains of Legionella spp. (49 Legionella pneumophila and 11 ATCC type strains of other Legionella species) were determined. Agar dilution testing was used on buffered charcoal-yeast extract agar to which 0.1% alpha-ketoglutarate was added. The most active of the penicillins tested were ampicillin (MIC = 0.06-8 mg/l) and temocilin (MIC = 0.125 - 16 mg/l); the most active cephalosporins were ceftazidime (MIC = 0.03 - 0.5 mg/l), HR 810 (MIC = 0.06 - 1 mg/l) and cefoxitin (MIC = 0.125 - 2 mg/l). Of all the drugs tested imipenem had the most pronounced activity (MIC = .0075 - 0.06 mg/l).
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PMID:Susceptibility of Legionella spp. to imipenem and 27 other beta-lactam antibiotics. 659 34

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

The susceptibilities of 56 Legionella pneumophila isolates (43 clinical and 15 environmental isolates) to levofloxacin, ofloxacin, erythromycin, and rifampin were studied with buffered charcoal yeast extract (BCYE) agar (inoculum, 10(4) CFU per spot), and the susceptibilities of five isolates were studied with buffered yeast extract (BYE) broth (inoculum, 10(5) CFU/ml). The MICs inhibiting 90% of strains tested on BCYE agar were 0.125, 0.25, 1.0, and < or = 0.004 micrograms/ml for levofloxacin, ofloxacin, erythromycin, and rifampin, respectively. The MICs by the BYE broth dilution method were 1 to 3, 2, 1 to 2, and 1 tube lower than those by the agar dilution method for levofloxacin, ofloxacin, erythromycin, and rifampin, respectively. The MBCs were 1 to 2 tubes higher than the broth dilution MICs for levofloxacin, 1 to 3 tubes higher than the broth dilution MICs for ofloxacin, 1 to 3 tubes higher than the broth dilution MICs for erythromycin, and the same as the broth dilution MICs for rifampin. In kinetic time-kill curve studies, at drug concentrations of 1.0 and 2.0 times the MIC, the most active drugs were levofloxacin and rifampin. At 72 h, concentrations of levofloxacin and rifampin of 2.0 times the MIC demonstrated a bactericidal effect against L. pneumophila. In contrast, at concentrations of 1.0 and 2.0 times the MICs regrowth was observed with ofloxacin and only a gradual decrease in the numbers of CFU per milliliter was observed with erythromycin. Only a minor inhibitory effect was observed with 0.25 or 0.5 time the MICs of all drugs at 24 to 48 h, with regrowth occurring at 72 h. In contrast to erythromycin or ofloxacin plus rifampin at 0.25 time the MICs, only levofloxacin plus rifampin demonstrated synergy. Thus, levofloxacin demonstrated the best inhibitory and bactericidal effects against L. pneumophila when it was studied alone or in a combination with rifampin.
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PMID:Inhibitory and bactericidal activities of levofloxacin, ofloxacin, erythromycin, and rifampin used singly and in combination against Legionella pneumophila. 883 16


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