Drugs online research references
Microbios. 1978;21(83):7-21.
Transport of tetracyclines through the bacterial cell membrane assayed by fluorescence: a study with susceptible and resistant strains of Staphylococcus aureus and Escherichia coli.
Samra Z, Krausz-Steinmetz J, Sompolinsky D.
The fluorescence of 12 tetracyclines in buffered solutions was measured by excitation at 400 nm and emission at 520 nm. The fluorescence varied markedly for different tetracyclines at equivalent concentrations. Demethylchlortetracycline exhibited more fluorescence than both chlortetracycline and demthyltetracycline; minocycline was virtually non-fluorescent at the conditions of the study. Fluorescence was highly dependent on the polarity of the solvent; when the buffer solution in water was replaced by a solvent containing 50% methanol, fluorescence increased significantly, but to various degrees for different tetracyclines. The most striking influence of the addition of methanol was observed for doxycycline (5-oxy 6-deoxy-tetracycline), whereas the influence on anhydrotetracycline was negligible. When suspensions of a susceptible strain of Staphylococcus aureus were added to solutions of tetracyclines, membrane permeation of the drugs could be monitored by an increase in fluorescence. This increase varied strikingly with the different drugs and could not be correlated with the concentrations for 50% growth inhibition (Ki). This might be due to the quantitative variations in the intracellular level corresponding to a certain external concentration of the respective drug. When tetracycline-resistant strains of S. aureus and Escherichia coli were exposed to tetracycline, the intensity of fluorescence observed was less than for the corresponding susceptible strains; in spite of this, the quantitative differences of fluorescence exhibited by the susceptible and resistant strains seemed slight in relation to the differences in susceptibility. It was demonstrated that minocycline inhibits the membrane transport of tetracycline in S. aureus and E. coli. This inhibition seems to be competitive for S. aureus, but not for E. coli.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=375035&dopt=Abstract
J Invest Dermatol. 1986 Apr;86(4):449-53.
Effect of antibiotics on the generation of reactive oxygen species.
Miyachi Y, Yoshioka A, Imamura S, Niwa Y.
The relative antioxidant efficacy, in vitro, of several antibiotics was examined by studying their effects on the generation of reactive oxygen species (ROS) using zymosan-stimulated polymorphonuclear leukocytes (PMNL) and the cell-free, xanthine-xanthine oxidase system. The species investigated are superoxide radical anion (O2-.), hydrogen peroxide (H2O2), and hydroxyl radical (OH.). Three tetracyclines (tetracycline HCl, oxytetracycline HCl, and minocycline HCl), erythromycin, cephalexin, penicillin G, chloramphenicol, and streptomycin were used as test drugs. At concentrations comparable to therapeutic blood levels, tetracycline HCl, oxytetracycline HCl, minocycline HCl, and erythromycin inhibited some of the ROS production by PMNL. In the xanthine-xanthine oxidase system, only minocycline HCl suppressed the H2O2 level. Cephalexin, penicillin G, chloramphenicol, and streptomycin did not affect any of the ROS examined at the concentrations tested. The capacity of some of these agents to inhibit ROS generation by PMNL may account, in part, for their efficacy in inflammatory skin diseases such as acne vulgaris. The antioxidant effect of these antibiotics does not stem from their capability to scavenge ROS, but originates rather from their effect on PMNL cell function directly with resultant anti-inflammatory effects on the inflammatory processes.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3755739&dopt=Abstract
Pediatr Pulmonol. 2000 Mar;29(3):210-2.
In vitro activity of minocycline against respiratory pathogens from patients with cystic fibrosis.
Kurlandsky LE, Fader RC.
Pediatric Pulmonology, DeVos Children's Hospital, and Department of Pediatrics and Human Development, Michigan State University College of Human Medicine and Development, Grand Rapids, Michigan, USA.
Our objective was to determine the in vitro activity of minocycline against isolates of Burkholderia cepacia (BC), Stenotrophomonas maltophilia (SM), and Pseudomonas aeruginosa (PA) cultured from the respiratory tract of patients with cystic fibrosis (CF). Cultures of BC, SM, and PA were isolated in a hospital bacteriology laboratory from the sputum or oropharyngeal cultures obtained from patients attending a Cystic Fibrosis Center, and were prospectively tested for in vitro sensitivity to minocycline by Kirby-Bauer disk diffusion. From January 1994 to July 1995, 116 cultures from 61 patients had at least one of the three pathogens; 9/61 (15%) patients had an isolate of BC, and 7/9 (78%) had an initial isolate sensitive to minocycline, of which 3 were sensitive only to minocycline; 2 cultures were resistant to all antibiotics. Four of 7 patients with BC were treated with minocycline; 3 patients developed resistant isolates 3-13 months after therapy. Five of 61 patients (8%) had an isolate of SM: 4/5 (80%) of these isolates were sensitive to minocycline, of which 1 was sensitive only to minocycline. Fifty-five of 61 patients (90%) had at least one PA isolate, with 112 morphotypes recovered from 90 cultures: 40/112 morphotypes (36%) were sensitive to minocycline, 65 (58%) were resistant, and 7 (6%) were intermediate in sensitivity. We conclude that the marked in vitro activity of minocycline against BC and SM isolated from patients with CF suggests that minocycline may have an adjunct role in the antimicrobial therapy of multidrug resistant, respiratory pathogens in CF. Copyright 2000 Wiley-Liss, Inc.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10686042&dopt=Abstract
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