Drugs online research references
Mol Pharmacol. 2001 Jun;59(6):1441-5.
Insights into the mechanism of azithromycin interaction with an Escherichia coli functional ribosomal complex.
Dinos GP, Michelinaki M, Kalpaxis DL.
Laboratory of Biochemistry, School of Medicine, University of Patras, GR-26500 Patras, Greece.
Azithromycin, a derivative of erythromycin with improved activity against Gram-negative bacteria, exhibits a marginal inhibition effect in a model system derived from Escherichia coli, in which a peptide bond is formed between puromycin and AcPhe-tRNA bound at the P-site of poly(U)-programmed ribosomes. This renders the study of azithromycin interaction with Ac[(3)H]Phe-tRNA. poly(U). 70S ribosome complex (complex C) impossible, if we analyze its effect on peptide bond formation. To overcome this problem, we have used an alternative approach to investigate kinetically the azithromycin interaction with complex C and to compare the azithromycin binding properties with those of erythromycin. This approach was based on the ability of azithromycin to compete with tylosin, a macrolide antibiotic strongly inhibiting the puromycin reaction. Detailed kinetic analysis revealed that the encounter complex CA between complex C and azithromycin (A) undergoes a slow isomerization to a tighter complex C*A, which remains active toward puromycin. The determination of inhibition and isomerization rate constants enabled us to classify azithromycin as a slow-binding ligand of ribosomes. Compared with erythromycin, azithromycin is a better inducer and stabilizer of the C*A complex. This finding may explain the superiority of azithromycin as inhibitor of translation in E. coli cells and many other Gram-negative bacteria.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11353804&dopt=Abstract
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Antimicrob Agents Chemother. 1999 May;43(5):1298-300.
In vitro activities of antibiotics alone and in combination against Brucella melitensis at neutral and acidic pHs.
Akova M, Gur D, Livermore DM, Kocagoz T, Akalin HE.
Department of Medicine, Section of Infectious Diseases, Hacettepe University School of Medicine, 06100 Ankara, Turkey.
Brucellae survive acidic pHs in phagolysosomes. Azithromycin, streptomycin, and quinolones were active against Brucella melitensis at pH 7.0 but not at pH 5.0; rifampin and doxycycline retained activity at pH 5.0. Regardless of pH, azithromycin-rifampin and ofloxacin-rifampin showed less synergy than established streptomycin-doxycycline and rifampin-doxycycline combinations.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10223958&dopt=Abstract
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.umn.edu
We compared recommended doses of 2 oral macrolide antibiotics (10 days of clarithromycin, 5 days of azithromycin) for eradicating group A streptococci from the throats of individuals aged > or = 12 years with symptomatic pharyngitis and a positive throat culture. Patients received either clarithromycin (250 mg b.i.d. for 10 days [n=260]) or azythromycin (500 mg on day 1, followed by 250 mg q.d. for 4 days [n=265]). Follow-up throat cultures were obtained both at 13--19 days and at 28--38 days. We evaluated 392 patients (median age, 26 years; clarithromycin, 194 patients; azyithromycin, 198 patients). Ten days of clarithromycin therapy was more effective than 5 days of azithromycin therapy in eradicating the organism (91% [176/194] vs. 82% [162/198]; P=.012). More than 97% of all streptococcal isolates were macrolide-sensitive. Whether these bacteriologic eradication rates were the result of the 2 macrolides compared or were due to differences in duration of therapy could not be determined, but the statistically significant difference in eradication of group A streptococci does raise additional questions about shortened courses of macrolide therapy for this common infection.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11360224&dopt=Abstract
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