Rev Esp Quimioter. 2000 Sep;13(3):306-13.
[Pharmacodynamic basis for the use of amoxicillin-clavulanic acid in respiratory infections due to Streptococcus pneumoniae: In vitro studies in an experimental model]

[Article in Spanish]

Gomez-Lus ML, Garcia Y, Valero E, Amores R, Fuentes F.

Departamento de Microbiologia, Facultad de Medicina, Universidad Complutense de Madrid,Avda. de la Complutense s/n, 28040 Madrid.

Amoxicillin-clavulanic acid is a first choice treatment for respiratory tract infections caused by Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis. In a previous study we observed its high efficacy against penicillin-susceptible and intermediate-resistant strains of S. pneumoniae. We aimed to study the efficacy of this antibiotic against three strains of S. pneumoniae (susceptible, intermediate and resistant to penicillin) in a mouse model of pneumonia, and to determine the influence of the time of starting treatment and the in vitro postantibiotic effect. We also determined the serum levels of the antimicrobial agent in the mice, and correlated the pharmacodynamic parameters (Cmax/MIC, AUC/MIC and T>MIC) with the survival rate to establish the best predictor of efficacy. MICs with amoxicillin-clavulanic acid were 0. 03 mg/l, 0.25 mg/l and 2 mg/l for the penicillin-susceptible, -intermediate and -resistant strains, respectively. The ED90 were approximately 5 mg/kg for susceptible strains, 25 mg/kg for the intermediate and 50 mg/kg for the resistant strains. We observed a lower survival rate (approximately 55%) when the treatment began 31 h after infection than when it began 5 h (100%) and 19 h (approximately 90-100%) afterwards. Serum levels were dose dependent and the correlation with the pharmacodynamic parameters showed a significant association between survival and the T>MIC (r = 0.946). In vitro postantibiotic effects with 1, 4 and 10 times the MIC were 0.96 to 1.69 h for susceptible strains, 0.38 to 1.23 h for intermediate, and 1.52 to 2. 20 h for resistant strains. These results show the high efficacy of this antibiotic combination against strains with variable susceptibility to penicillin, with this activity being related mainly to the T>MIC of the microorganism. The postantibiotic effect would prolong the effect of the antibiotic in the dosing interval. These parameters and antimicrobial effects are important in terms of the clinical application of this antimicrobial agent.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11086282&dopt=Abstract antibiotic amoxicillin




Drugs. 2000 Sep;60(3):597-605.
Treatment of Chlamydia trachomatis infections in pregnant women.

Miller JM, Martin DH.

Department of Obstetrics and Gynecology, Louisiana State University Medical Center, New Orleans 70112, USA.

The intent of this article is to provide an overview of the epidemiology and pharmacotherapy, including cost analyses, of Chlamydia trachomatis infections in pregnant women. Chlamydia is a common sexually transmitted infection. For pregnant women, there are concerns both for the mother (post-partum endometritis, horizontal transmission) and the newborn (conjunctivitis, delayed pneumonia). Therapeutic options are restricted because of the fetus and include multi-day treatment with erythromycin, amoxicillin, clindamycin or single dose azithromycin. Clinical cure rates with these options are 86, 92, 93 and 95%, respectively. Pharmacoeconomic analyses have been conducted to determine if the initial increase in acquisition cost of azithromycin (approximately 3-fold higher than erythromycin or amoxicillin) is offset by improvement in compliance and drug efficacy. Clindamycin has received little attention because of its expense (4-fold more than azithromycin). Analyses have been retrospective. As models incorporate more complications of failure to cure, azithromycin increasingly becomes more cost effective and is our recommended treatment.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11030469&dopt=Abstract antibiotic amoxicillin

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BACKGROUND: Triple therapies with proton pump inhibitor/ranitidine bismuth citrate (RBC), clarithromycin (C) and either amoxicillin (A) or a nitroimidazole (I) are widely accepted as treatment for Helicobacter pylori infection. However, it is not clear which of these antibiotic combinations should be preferred. AIM: To evaluate whether there is a difference in efficacy between triple therapies with proton pump inhibitor/RBC, clarithromycin and either amoxicillin or a nitroimidazole. METHODS: The literature was examined for randomized trials comparing proton pump inhibitor/RBC-C-A and proton pump inhibitor/RBC-C-I. Studies were grouped according to the type of acid inhibitor used (proton pump inhibitor or RBC) and differences between pooled cure rates were calculated. RESULTS: Forty-seven studies were identified: seven using RBC, 39 using proton pump inhibitor, one using both. RBC-C-I was somewhat superior to RBC-C-A, although this difference only reached statistical significance in intention-to-treat analysis. Overall, proton pump inhibitor-C-I and proton pump inhibitor-C-A were equally effective, but in nitroimidazole-susceptible strains, proton pump inhibitor-C-I performed better, in nitroimidazole-resistant strains, proton pump inhibitor-C-A performed better. No serious side-effects were reported and pooled drop-out rates were equal. CONCLUSIONS: In general, proton pump inhibitor-C-I and proton pump inhibitor-C-A are equally effective and therefore other factors such as local prevalence of resistant strains, cost of therapy and options for second-line treatment should determine which regimen should be preferred. When using RBC, the RBC-C-I combination is somewhat superior to RBC-C-A.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11328254&dopt=Abstract antibiotic amoxicillin




Antimicrob Agents Chemother. 2000 Dec;44(12):3368-73.
Characterization of an In vitro-selected amoxicillin-resistant strain of Helicobacter pylori.

DeLoney CR, Schiller NL.

Division of Biomedical Sciences, University of California, Riverside, Riverside, California 92521, USA.

An amoxicillin-resistant (Amox(r)) strain of Helicobacter pylori was selected for by culturing an amoxicillin-sensitive (Amox(s)) strain in increasingly higher concentrations of amoxicillin, resulting in a 133-fold increase in MIC, from 0.03 to 0.06 microg/ml to 4 to 8 microg/ml. This resistance was stable upon freezing for at least 6 months and conferred cross-resistance to seven other beta-lactam antibiotics. beta-Lactamase activity was not detected in this Amox(r) strain; however, analysis of the penicillin-binding protein (PBP) profiles generated from isolated bacterial membranes of the Amox(s) parental strain and the Amox(r) strain revealed a significant decrease in labeling of PBP 1 by biotinylated amoxicillin (bio-Amox) in the Amox(r) strain. Comparative binding studies of PBP 1 for several beta-lactams demonstrated that PBP 1 in the Amox(r) strain had decreased affinity for mezlocillin but not significantly decreased affinity for penicillin G. In addition, PBP profiles prepared from whole bacterial cells showed decreased labeling of PBP 1 and PBP 2 in the Amox(r) strain at all bio-Amox concentrations tested, suggesting a diffusional barrier to bio-Amox or a possible antibiotic efflux mechanism. Uptake analysis of (14)C-labeled penicillin G showed a significant decrease in uptake of the labeled antibiotic by the Amox(r) strain compared to the Amox(s) strain, which was not affected by pretreatment with carbonyl cyanide m-chlorophenylhydrazone, eliminating the possibility of an efflux mechanism in the resistant strain. These results demonstrate that alterations in PBP 1 and in the uptake of beta-lactam antibiotics in H. pylori can be selected for by prolonged exposure to amoxicillin, resulting in increased resistance to this antibiotic.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11083642&dopt=Abstract antibiotic amoxicillin