Antibiotic resistance in bacterial pathogens threatens the future of modern medicine. One such resistant pathogen is methicillin-resistant Staphylococcus aureus (MRSA), which is resistant to nearly ...all β-lactam antibiotics, limiting treatment options. Here, we show that a significant proportion of MRSA isolates from different lineages, including the epidemic USA300 lineage, are susceptible to penicillins when used in combination with β-lactamase inhibitors such as clavulanic acid. Susceptibility is mediated by a combination of two different mutations in the mecA promoter region that lowers mecA-encoded penicillin-binding protein 2a (PBP2a) expression, and in the majority of isolates by either one of two substitutions in PBP2a (E246G or M122I) that increase the affinity of PBP2a for penicillin in the presence of clavulanic acid. Treatment of S. aureus infections in wax moth and mouse models shows that penicillin/β-lactamase inhibitor susceptibility can be exploited as an effective therapeutic choice for 'susceptible' MRSA infection. Finally, we show that isolates with the PBP2a E246G substitution have a growth advantage in the presence of penicillin but the absence of clavulanic acid, which suggests that penicillin/β-lactamase susceptibility is an example of collateral sensitivity (resistance to one antibiotic increases sensitivity to another). Our findings suggest that widely available and currently disregarded antibiotics could be effective in a significant proportion of MRSA infections.
Amoxicillin has been in use since the 1970s; it is the most widely used penicillin both alone and in combination with the β-lactamase clavulanic acid.
In this narrative review, we re-examine the ...properties of oral amoxicillin and clavulanic acid and provide guidance on their use, with emphasis on the preferred use of amoxicillin alone.
Published medical literature (MEDLINE database via Pubmed).
While amoxicillin and clavulanic acid have similar half-lives, clavulanic acid is more protein bound and even less heat stable than amoxicillin, with primarily hepatic metabolism. It is also more strongly associated with gastrointestinal side effects, including Clostridium difficile infection, and, thus, in oral combination formulations, limits the maximum daily dose of amoxicillin that can be given. The first ratio for an amoxicillin–clavulanic acid combination was set at 4:1 due to clavulanic acid's high affinity for β-lactamases; ratios of 2:1, 7:1, 14:1 and 16:1 are currently available in various regions. Comparative effectiveness data for the different ratios are scarce. Amoxicillin–clavulanic acid is often used as empiric therapy for many of the World Health Organization's Priority Infectious Syndromes in adults and children, leading to extensive consumption, when some of these syndromes could be handled with a delayed antibiotic prescription approach or amoxicillin alone.
Using available epidemiological and pharmacokinetic data, we provide guidance on indications for amoxicillin versus amoxicillin–clavulanic acid and on optimal oral administration, including choice of combination ratio. More data are needed, particularly on heat stability, pharmacodynamic effects and emergence of resistance in ‘real-world’ clinical settings.
Background
Betalactam (BL) antibiotics are the most common cause of drug hypersensitivity. Amoxicillin (AX), which is often prescribed alongside clavulanic acid (Clav), is the most common elicitor. ...The aim of this study was to determine whether AX and Clav‐responsive T‐cells are detectable in patients with immediate hypersensitivity to AX‐Clav, to assess whether these T‐cells display the same specificity as that detected in skin and provocation testing, and to explore T‐cell activation pathways.
Methods
Drug‐specific T‐cell clones were generated from immediate hypersensitive patients´ blood by serial dilution and repetitive mitogen stimulation. Antigen specificity was assessed by measurement of proliferation and cytokine release. CD4+/CD8+ phenotype and chemokine receptor expression were analyzed by flow cytometry.
Results
110 AX‐specific and 96 Clav‐specific T‐cell clones were generated from seven patients with positive skin test to either AX or Clav. Proliferation of AX‐ and Clav‐specific clones was dose‐dependent, and no cross‐reactivity was observed. AX‐ and Clav‐specific clones required antigen‐presenting cells to proliferate, and drugs were presented to CD4+ and CD8+ T‐cells by MHC class‐II and I, respectively. A higher secretion of IL‐13 and IL‐5 was detected in presence of the culprit drug compared with the alternative drug. Clones expressed CD69, CCR4, CXCR3, and CCR10.
Conclusions
Our study details the antigen specificity and phenotype of T‐cell clones generated from patients with AX‐Clav‐induced immediate hypersensitivity diagnosed by positive skin test. AX‐ and Clav‐specific clones were generated from patients irrespective of whether AX or Clav was the culprit, although differences in cytokine secretion were observed.
AX‐ and Clav‐specific T‐cell clones can be generated from the same patient with immediate hypersensitivity, irrespective of whether AX or Clav is the culprit drug in the combination AX‐Clav. No cross‐reactivity between AX and Clav is detected. Differences in cytokine secretion are observed between T‐cell clones generated against the culprit or the alternative drug in the combination AX‐Clav.Abbreviations: AX, amoxicillin; Clav, clavulanic acid.
Ceftibuten-clavulanate (CTB-CLA) is a novel β-lactam-β-lactamase combination with potential utility for the management of urinary tract infections caused by extended-spectrum-β-lactamase ...(ESBL)-producing organisms. We examined the pharmacodynamics of the combination against 25
expressing β-lactamases (CTX-M, TEM, and SHV wild types and SHV-ESBL) in the murine thigh infection model. MIC values of CTB and CTB-CLA ranged from 1 to >32 mg/liter and 0.125 to 8 mg/liter, respectively. Human-simulated regimens of CTB and CLA equivalent to clinical doses of 400 mg orally (p.o.) every 8 h (q8h) and 187 mg q8h, respectively, were developed. CLA dose fractionation studies were undertaken to characterize the driver of efficacy. CLA dose-ranging studies were undertaken to assess the activity of the CTB human-simulated regimen in combination with escalating CLA exposures. The relationships between the percentage of the dosing interval during which the free CLA plasma concentrations remained above a threshold concentration (%
>
) and the change in log
CFU per thigh at 24 h were examined across different threshold concentrations. Additionally, the efficacy of a human-simulated regimen of CTB-CLA was assessed against isolates with various susceptibilities to the combination. The pharmacokinetic/pharmacodynamic index that best correlated with the efficacy of the combination was %
> threshold CLA plasma concentration of 0.5 mg/liter. The plasma %
>0.5 mg/liter associated with the static endpoint was 20.59%. For isolates with CTB-CLA MICs of ≤4 mg/liter, stasis was achieved with a human-simulated regimen of CTB-CLA against 20/22 isolates (90.9%), while for isolates with MICs of 8 mg/liter, only 1/3 tested isolates (33.3%) displayed stasis. Results suggest a susceptibility breakpoint of 4 mg/liter for CTB-CLA. These data support the consideration of the CTB-CLA combination for the treatment of urinary tract infections due to ESBL-producing
.
In this study, spectrophotometry method was combined with artificial intelligence approaches, including feedforward backpropagation neural network (FFBP-NN) and radial basis function neural network ...(RBF-NN) for the simultaneous estimation of amoxicillin (AMX) and clavulanic acid (CLV) in binary mixtures, pharmaceutical tablet, and blood serum. Levenberg–Marquardt (LM) and Resilient Backpropagation (RP) were applied as training algorithms of FFBP-NN. Among with different layers (2 and 4) and neurons (2, 4, 6, and 8) related to the LM algorithm, layers 4 and 2 with 8 neurons revealed the lowest mean square error (MSE) equal to 4.72 × 10−29 and 4.32 × 10−29 for AMX and CLV, respectively. In the RP algorithm, layers 4 and 2 with 8 neurons indicated minimum MSE of 1.63 and 0.605 for AMX and CLV, respectively. In the RBF-NN, MSE equal to 6.47 × 10−26 and 1.83 × 10−26 was obtained for AMX and CLV, respectively. Analysis of variance (ANOVA) test at the 95% confidence level was used to examine the significant differences between the methods. Also, the determination of the AMX and CLV was simultaneously investigated in blood serum sample as a complex matrix. Simple, fast, and low-cost are the benefits of this spectrophotometry method, which does not require separation step for the simultaneous estimation of components in pharmaceutical formulations.
Clavulanic acid (CA) is a naturally occurring antibiotic produced by
Streptomyces clavuligerus
. Statistical optimization of the fermentation medium for CA production by
Streptomyces clavuligerus
was ...carried out. Multiple carbon sources, glycerol, dextrin, and triolein, were considered simultaneously
.
A two-level fractional factorial design experiment was conducted to identify the significant components of medium on CA production. Statistical analysis of the results showed that soybean meal, dextrin, and triolein were the most significant medium ingredients on CA production. The optimal level of these screened components was obtained by RSM based on the result of a Box-Behnken design, in which the values of dextrin, soybean meal, and triolein in CA fermentation medium were 12.37 g/L, 39.75 g/L, and 26.98 ml/L, respectively. Using the proposed optimized medium, the model predicted 938 mg/L of CA level and via experimental rechecking the model, 946 mg/L of CA level was attained in shake flask fermentation, significantly high than 630 mg/L of original medium. The optimized medium was further verified in 50-L stirred fermenter, and compared with performance of original medium in parallel, CA titer was increased from 889 to 1310 mg/L; a 47% increase was achieved through medium optimization by statistical approaches.
Amoxicillin (AX) combined or not with clavulanic acid (CLV) is frequently involved in IgE-mediated reactions. Drug provocation test (DPT) is considered as the gold standard for diagnosis, although ...contraindicated in high-risk patients. Basophil activation test (BAT) can help diagnose immediate reactions to beta-lactams, although controversy exists regarding the best activation marker. We have performed a real-life study in a prospective cohort to analyze the real value of BAT as diagnostic tool and the best activation marker, CD63 and CD203c, for the evaluation of immediate reactions to these drugs.
We prospectively evaluated patients with a clinical suspicion of immediate reactions after AX or AX-CLV administration during a 6-year period. The allergological work-up was done following the EAACI recommendations. BAT was performed in all patients using CD63 and CD203c as activation markers.
In AX-allergic patients, both activation markers, CD63 and CD203c, showed similar SE values (48.6% and 46.7%, respectively); however, specificity was of 81.1% and 94.6%, respectively, with CD203c showing good positive predictive value and like-hood ratio. In CLV-allergic patients, CD203c showed higher SE (50%) than CD63 (42.9%), maintaining the same value of SP (80%). Combining the results of both markers can slightly increase the sensitivity (51.4% for AX and 54.8% for CLV), although decreasing the specificity (79.7% and 73%, respectively). Interestingly, all patients with an anaphylactic shock showed a positive BAT to CLV using CD203c.
BAT using CD203c showed a good confirmatory power, especially for AX allergy. Placing BAT as a first step in the diagnostic procedure can help reduce the need of performing a complete allergological work-up in 46.6% of patients, diminishing the risk of reinducing allergic reactions.
Rapid, accurate and sensitive ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) methods were developed and validated for the simultaneous quantitation of amoxicillin and ...clavulanic acid in human plasma and urine samples. Amoxicillin and clavulanic acid in both plasma and urine were extracted using a solid-phase extraction method. The compounds were separated on an Acquity UPLC HSS T3 column (2.1 × 100 mm, 1.8 μm). Ampicillin was used as the internal standard (IS) in plasma, while amoxicillin-d4 and sulbactam were used as ISs in urine. The lower limit of quantitation was 0.0500 and 0.0250 μg/mL for amoxicillin and clavulanic acid in plasma, and 0.0500 μg/mL for both analytes in urine. The established methods were validated in terms of selectivity, precision, accuracy, linearity, matrix effect, recovery, carryover, interaction, dilution integrity and stability, and successfully applied to a pharmacokinetic study of amoxicillin sodium and clavulanate potassium (10:1) injection in healthy volunteers.
Biosynthesis of clavam metabolites Jensen, Susan E
Journal of industrial microbiology & biotechnology,
10/2012, Letnik:
39, Številka:
10
Journal Article
Recenzirano
Odprti dostop
Naturally occurring clavam metabolites include the valuable β-lactamase inhibitor, clavulanic acid, as well as stereochemical variants with side-chain modifications, called the 5S clavams. Because of ...the clinical importance of clavulanic acid, most studies of clavam biosynthesis are based on the industrial producer species Streptomyces clavuligerus. Well-characterized early steps in clavam biosynthesis are outlined, and less well understood late steps in 5S clavam biosynthesis are proposed. The complex genetic organization of the clavam biosynthetic genes in S. clavuligerus is described and, where possible, comparisons with other producer species are presented.
Mycobacterium tuberculosis (Mtb), the main causative agent of tuberculosis (TB), is naturally resistant to β-lactam antibiotics due to the production of the extended spectrum β-lactamase BlaC. ...β-Lactam/β-lactamase inhibitor combination therapies can circumvent the BlaC-mediated resistance of Mtb and are promising treatment options against TB. However, still little is known of the exact mechanism of BlaC inhibition by the β-lactamase inhibitors currently approved for clinical use, clavulanic acid, sulbactam, tazobactam, and avibactam. Here, we present the X-ray diffraction crystal structures of the acyl-enzyme adducts of wild-type BlaC with the four inhibitors. The +70 Da adduct derived from clavulanate and the trans-enamine acylation adducts of sulbactam and tazobactam are reported. BlaC in complex with avibactam revealed two inhibitor conformations. Preacylation binding could not be observed because inhibitor binding was not detected in BlaC variants carrying a substitution of the active site serine 70 to either alanine or cysteine, by crystallography, ITC or NMR. These results suggest that the catalytic serine 70 is necessary not only for enzyme acylation but also for increasing BlaC affinity for inhibitors in the preacylation state. The structure of BlaC with the serine to cysteine mutation showed a covalent linkage of the cysteine 70 Sγ atom to the nearby amino group of lysine 73. The differences of adduct conformations between BlaC and other β-lactamases are discussed.
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