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Clavulanic Acid (clavulanic + acid)
Selected AbstractsORF6 from the clavulanic acid gene cluster of Streptomyces clavuligerus has ornithine acetyltransferase activityFEBS JOURNAL, Issue 8 2002Nadia J. Kershaw The clinically used beta-lactamase inhibitor clavulanic acid is produced by fermentation of Streptomyces clavuligerus. The orf6 gene of the clavulanic acid biosynthetic gene cluster in S. clavuligerus encodes a protein that shows sequence homology to ornithine acetyltransferase (OAT), the fifth enzyme of the arginine biosynthetic pathway. Orf6 was overexpressed in Escherichia coli (at ,,15% of total soluble protein by SDS/PAGE analysis) indicating it was not toxic to the host cells. The recombinant protein was purified (to >,95% purity) by a one-step technique. Like other OATs it was synthesized as a precursor protein which underwent autocatalytic internal cleavage in E. coli to generate , and , subunits. Cleavage was shown to occur between the alanine and threonine residues in a KGXGMXXPX--(M/L)AT (M/L)L motif conserved within all identified OAT sequences. Gel filtration and native electrophoresis analyses implied that the ORF6 protein was an ,2,2 heterotetramer and direct evidence for this came from mass spectrometric analyses. Although anomalous migration of the , subunit was observed by standard SDS/PAGE analysis, which indicated the presence of two bands (as previously observed for other OATs), mass spectrometric analyses did not reveal any evidence for post-translational modification of the , subunit. Extended denaturation with SDS before PAGE resulted in observation of a single major , subunit band. Purified ORF6 was able to catalyse the reversible transfer of an acetyl group from N -acetylornithine to glutamate, but not the formation of N -acetylglutamate from glutamate and acetyl-coenzyme A, nor (detectably) the hydrolysis of N -acetylornithine. Mass spectrometry also revealed the reaction proceeds via acetylation of the , subunit. [source] A novel finding that Streptomyces clavuligerus can produce the antibiotic clavulanic acid using olive oil as a sole carbon sourceJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2008G. Efthimiou Abstract Aims:, This study aims to establish whether commercially available food oils can be used by Streptomyces clavuligerus as sole carbon sources for growth and clavulanic acid production. Methods and results:, Batch cultures in bioreactors showed that Strep. clavuligerus growth and clavulanic acid yields in a P-limited medium containing 0.6% (v/v) olive oil were respectively 2.5- and 2.6-fold higher than in a glycerol-containing medium used as control. Glycerol- and olive oil-grown cells present different macromolecular composition, particularly lipid and protein content. Conclusions:,Streptomyces clavuligerus uses olive oil as the sole carbon and energy source for growth and clavulanic acid production. Yields and production rates in olive oil are comparable to those reported for oil-containing complex media. Differences in yields and in the macromolecular composition indicate that different metabolic pathways convert substrate into product. Significance and impact of the study:, This is the first report of oils being used as the sole carbon source by Strep. clavuligerus. Apart from economic benefits, interesting questions are raised about Strep. clavuligerus physiology. Defined culture media allow physiological studies to be performed in the absence of interference by other compounds. Understanding how Strep. clavuligerus catabolises oils may have an economic impact in clavulanic acid production. [source] Severe toxic hepatitis associated with amoxycillin and clavulanic acidJOURNAL OF CLINICAL PHARMACY & THERAPEUTICS, Issue 3 2001G. Ersoz MD Toxic hepatitis secondary to amoxycillin,clavulanic acid is an infrequent clinical picture. Most of the cases are reported to have a benign course. We report two cases of severe hepatic failure following amoxycillin,clavulanic acid use. One of the cases had cholestatic features primarily, and the other had hepatocellular injury prominently. The first case had also findings of trombotic trombositic purpura and had a fatal course. [source] Determination of clavulanic acid in calf plasma by liquid chromatography tandem mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 11 2006Tim Reyns Abstract A method for the quantification of clavulanic acid in calf plasma using high-performance liquid chromatography combined with electrospray ionization (ESI) mass spectrometry, operating in the negative ionization mode (LC-MS/MS), is presented. Sample preparation includes a simple and fast deproteinization with acetonitrile and a back-extraction of the acetonitrile with dichloromethane. Chromatography is performed on a reversed-phase PLRP-S polymeric column using 0.05% formic acid in water and acetonitrile. The limit of quantification is 25 ng/ml, which is lower than other published methods using ultraviolet (UV), fluorimetric or mass spectrometric detection. The limit of detection is calculated to be 3.5 ng/ml. The stability of clavulanic acid was demonstrated according to The Guidelines of Bioanalytical Method Validation of The Food and Drug Administration (FDA): freeze and thaw stability, short-term stability, long-term stability, stock solution stability and postpreparative stability. The method is used in a pharmacokinetic and bioequivalence study of amoxycillin/clavulanic acid formulations in calves. Copyright © 2006 John Wiley & Sons, Ltd. [source] Variable absorption of clavulanic acid after an oral dose of 25 mg/kg of Clavubactin® and Synulox® in healthy dogsJOURNAL OF VETERINARY PHARMACOLOGY & THERAPEUTICS, Issue 3 2003T. B. Vree The aims of this investigation were to calculate the pharmacokinetic parameters and to identify parameters, based on individual plasma concentration,time curves of amoxicillin and clavulanic acid in dogs, that may govern the observed differences in absorption of both drugs. The evaluation was based on the data from plasma concentration,time curves obtained following a single dose in an open, randomized, two-way crossover study involving 24 male Beagle dogs treated with two Amoxi,Clav formulations (A Clavubactin® and B Synulox®, each with 200/50 mg). Plasma amoxicillin and clavulanic acid concentrations were determined using validated bioassay methods. The half-life of elimination of amoxicillin was 1.5 h (t1/2 = 1.52 ± 0.19 h, Cmax = 11.4 ± 2.74 ,g/mL), and that of clavulanic acid 0.76 h (t1/2 = 0.71 ± 0.23 h, Cmax = 2.06 ± 1.05 ,g/mL). There was a fivefold variation in the AUCt of clavulanic acid for both formulations, while the AUCt of amoxicillin varied by a factor of 2. The mean ratio of the AUCt amoxicillin : clavulanic acid was 12.7 ± 3.65 for formulation A and 11.8 ± 5.22 for formulation B (P = 0.51). [source] Improvement for the production of clavulanic acid by mutant Streptomyces clavuligerusLETTERS IN APPLIED MICROBIOLOGY, Issue 5 2002S.D. Lee Aims:,To improve the production of clavulanic acid through the development of strains, the selection of a production medium and a pH shift strategy in a bioreactor. Methods and Results:,Streptomyces clavuligerus mutant 15 was selected by antibacterial activities. As a result of pH control in a 2·5 l bioreactor, the highest productivity (3·37 ,g ml,1 h,1) was obtained at a controlled pH of 7·0. Conclusions:,The highest level of production obtained was an increase of about 36% compared with a non-controlled pH. When the production of clavulanic acid reached the maximum level, the pH was shifted from 7·0 to 6·0 for reduction in decomposition rate. The maximum concentration of clavulanic acid was maintained for 24 h as a result of the pH shift control, and a significant reduction in the decomposition of clavulanic acid was obtained. Significance and Impact of the Study:,Clavulanic acid decomposition was considerably reduced as a result of the pH shift control. The results of this study can be applied for the efficient production of ,-lactamase inhibitory antibiotics. [source] Failure of dietary oligofructose to prevent antibiotic-associated diarrhoeaALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 4 2005S. Lewis Summary Background :,Oligofructose is metabolized by bifidobacteria, increasing their numbers in the colon. High bifidobacteria concentrations are important in providing ,colonization resistance' against pathogenic bacteria. Aim :,To reduce the incidence of antibiotic-associated diarrhoea in elderly patients. Methods :,Patients over the age of 65 taking broad-spectrum antibiotics received either oligofructose or placebo. A baseline stool sample was cultured for Clostridium difficile and tested for C. difficile toxin. A further stool sample was analysed for C. difficile if diarrhoea developed. Results :,No difference was seen in the baseline characteristics, incidence of diarrhoea, C. difficile infection or hospital stay between the two groups (n = 435). Oligofructose increased bifidobacterial concentrations (P < 0.001, 95% CI: 0.69,1.72). A total of 116 (27%) patients developed diarrhoea of which 49 (11%) were C. difficile -positive and were more likely to be taking a cephalosporin (P = 0.006), be female (P < 0.001), to have lost more weight (P < 0.001, 95% CI: 0.99,2.00) and stayed longer in hospital (P < 0.001, 95% CI: 0.10,1.40). Amoxicillin (amoxycillin) and clavulanic acid increased diarrhoea not caused by C. difficile (P = 0.006). Conclusion :,Oligofructose does not protect elderly patients receiving broad-spectrum antibiotics from antibiotic-associated diarrhoea whether caused by C. difficile or not. Oligofructose was well-tolerated and increased faecal bifidobacterial concentrations. [source] Sinus Tissue Pharmacokinetics After Oral Administration of Amoxicillin/Clavulanic AcidTHE LARYNGOSCOPE, Issue 6 2000Paulo Borges Dinis MD Abstract Objectives The in vitro synergy of the amoxicillin/clavulanic acid combination has not always translated in vivo into clinical superiority compared with amoxicillin alone. Specifically, conflicting reports have disputed the superiority of the combination in the treatment of both acute otitis media and acute sinusitis. One possible reason for this may have to do with inadequate target tissue pharmacokinetics. To explore this possibility in the sinuses, we undertook the present investigation. Study Design A randomized, open, single-dose, sinus tissue pharmacokinetic study with oral amoxicillin/clavulanic acid. Methods Twenty-three adult patients with chronic rhinosinusitis who had been selected for surgery were randomly allocated to receive a tablet of 875/125 mg amo-icillin/clavulanate 2 to 4 hours before surgery began. During the operation tissue samples were collected at specific sinonasal sites for determination of both amo-icillin and clavulanic acid concentration levels. Results Amoxicillin displayed adequate tissue levels throughout the sinuses, high enough to cover common susceptible pathogens. However, the presence of clavulanate was detected in only half of the sinonasal tissue samples. Conclusions The kinetics of oral clavulanic acid apparently fails to provide a widespread anti,,-lactamase activity capable of enhancing the activity of amoxicillin in all parts of the sinuses. Despite this, amoxicillin/clavulanic acid maintains a central role in the treatment of acute rhinosinusitis, because amoxicillin is still the most effective oral ,-lactam against Streptococcus pneumoniae, a particularly virulent and increasingly resistant upper respiratory tract pathogen. Also, as our data show, a concomitant anti,,-lactamase activity can be expected to occur, although in an unpredictable fashion. [source] Prevalence of AmpC over-expression in bloodstream isolates of Pseudomonas aeruginosaCLINICAL MICROBIOLOGY AND INFECTION, Issue 4 2007V. H. Tam Abstract This study examined the contribution of AmpC over-expression to ,-lactam resistance in clinical isolates of Pseudomonas aeruginosa obtained from a hospital in Houston, TX, USA. Seventy-six non-repeat bloodstream isolates obtained during 2003 were screened for ceftazidime resistance in the presence and absence of clavulanic acid 4 mg/L. AmpC was identified by isoelectric focusing (with and without cloxacillin inhibition); stable derepression was ascertained phenotypically by a spectrophotometric assay (with and without preceding induction by imipenem) using nitrocefin as the substrate, and was confirmed subsequently by quantitative RT-PCR of the ampC gene. The clonal relatedness of the AmpC-over-expressing isolates was assessed by pulsed-field gel electrophoresis. In addition, the ampC and ampR gene sequences were determined by PCR and sequencing. For comparison, two standard wild-type strains (PAO1 and ATCC 27853) and three multidrug-susceptible isolates were used as controls. AmpC over-expression was confirmed in 14 ceftazidime-resistant isolates (overall prevalence rate, 18.4%), belonging to seven distinct clones. The most prevalent point mutations in ampC were G27D, V205L and G391A. Point mutations in ampR were also detected in eight ceftazidime-resistant isolates. AmpC over-expression appears to be a significant mechanism of ,-lactam resistance in P. aeruginosa. Understanding the prevalence and mechanisms of ,-lactam resistance in P. aeruginosa may guide the choice of empirical therapy for nosocomial infections in hospitals. [source] | ||||||||||||||||