Drugs online research references
Antimicrob Agents Chemother. 1992 Jan;36(1):10-6.
Potentiation of antibacterial activity of azithromycin and other macrolides by normal human serum.
Pruul H, McDonald PJ.
Department of Microbiology and Infectious Diseases, Flinders Medical Centre, Bedford Park, Australia.
The interaction of azithromycin with normal human serum was examined in relation to serum protein binding, MIC, and kinetics of killing of bacteria. While the binding of azithromycin to serum proteins is low (8.5% at a concentration of 0.01 mM in 95% serum), the presence of 40% serum during the MIC test decreased MICs by 26-fold for serum-resistant Escherichia coli and 15-fold for Staphylococcus aureus. Erythromycin had a similar but lesser effect, while roxithromycin was less active against S. aureus in the presence of serum. The rate of killing of E. coli and S. aureus by azithromycin was increased in the presence of serum. The enhancement of antibiotic activity by serum was pH independent, and heat inactivation and preabsorption with homologous bacteria failed to inhibit enhancement by serum. The macromolecular incorporation of [3H]thymidine by E. coli continuously exposed to 2 micrograms of azithromycin per ml (0.25x the MIC) and 40% serum was decreased by 80% at pH 7.8 and by 48% at pH 7.2, while azithromycin alone failed to inhibit incorporation. Inhibition of nucleic acid biosynthesis at pH 7.2 in the presence of serum was also detected with sub-MICs of erythromycin, norfloxacin, and gentamicin but not roxithromycin. A diffusible serum factor was shown to interact with azithromycin to inhibit the growth of E. coli in an agar diffusion assay to detect antibiotic-serum synergy.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1317141&dopt=Abstract
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Antimicrob Agents Chemother. 1992 Jan;36(1):180-4.
Activities of four macrolides, including clarithromycin, against Mycobacterium fortuitum, Mycobacterium chelonae, and M. chelonae-like organisms.
Brown BA, Wallace RJ Jr, Onyi GO, De Rosas V, Wallace RJ 3rd.
Department of Microbiology, University of Texas Health Center, Tyler 75710.
Susceptibilities to erythromycin by broth microdilution were compared with those to the newer macrolide clarithromycin for 223 isolates of rapidly growing mycobacteria belonging to seven taxonomic groups. Seventy-nine random isolates were also tested against azithromycin and roxithromycin. The MIC of clarithromycin for 90% of strains tested (MIC90) was 0.25 microgram/ml for isolates of Mycobacterium chelonae subsp. chelonae and 0.5 microgram/ml for M. chelonae subsp. abscessus, with 100% of strains inhibited by less than or equal to 1 microgram/ml. Clarithromycin was 10 to 50 times more active than erythromycin and four- to eightfold more active than the other newer macrolides against M. chelonae. MICs of clarithromycin frequently increased with prolonged incubation with isolates of M. chelonae subsp. abscessus but not M. chelonae subsp. chelonae. MICs of clarithromycin were much higher for M. fortuitum bv. fortuitum (MIC50, 2.0 microgram/ml; MIC90, greater than 8.0 microgram/ml). The three newer macrolides had comparable activity against M. fortuitum bv. peregrinum (MIC90s of 0.5 to 2.0 microgram/ml compared with erythromycin MIC90s of greater than 8.0 microgram/ml). Overall, clarithromycin was the most active agent, inhibiting all isolates of M. chelonae subsp. chelonae, M. chelonae subsp. abscessus, M. fortuitum bv. peregrinum, and the M. chelonae-like organisms and 35% of M. fortuitum bv. fortuitum at less than or equal to 1 microgram/ml. Clinical trials of the newer macrolides, especially clarithromycin, against these environmental mycobacterial species appear to be warranted.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1317144&dopt=Abstract
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J Antibiot (Tokyo). 1992 Apr;45(4):527-34.
Synthesis and antibacterial activity of O-methylazithromycin derivatives.
Kobrehel G, Lazarevski G, Dokic S, Kolacny-Babic L, Kucisec-Iepes N, Cvrlje M.
PLIVA, Research and Development, Zagreb, Yugoslavia.
A series of O-methylazithromycin derivatives have been synthesized and their antibacterial activities were compared with those of azithromycin (1). O-Methylation of 1 proceeded stepwise by the two main pathways beginning at the C-6 and C-11 hydroxyl groups, individually. Among O-methyl derivatives, 6-O-methylazithromycin A (11) was slightly less active than 1. The methylation of the secondary hydroxyl group at the C-11 position resulted surprisingly in an increase of their in vitro activity. The antibacterial activities of novel azalides decreased with increasing the number of the methyl groups introduced.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1317368&dopt=Abstract
word match zithromax online literature
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