RESUMO
The use of ß-lactam/ß-lactamase inhibitors constitutes an important strategy to counteract ß-lactamases in multidrug-resistant (MDR) Gram-negative bacteria. Recent reports have described ceftazidime-/avibactam-resistant isolates producing CTX-M variants with different amino acid substitutions (e.g., P167S, L169Q, and S130G). Relebactam (REL) combined with imipenem has proved very effective against Enterobacterales producing ESBLs, serine-carbapenemases, and AmpCs. Herein, we evaluated the inhibitory efficacy of REL against CTX-M-96, a CTX-M-15-type variant. The CTX-M-96 structure was obtained in complex with REL at 1.03 Å resolution (PDB 8EHH). REL was covalently bound to the S70-Oγ atom upon cleavage of the C7-N6 bond. Compared with apo CTX-M-96, binding of REL forces a slight displacement of the deacylating water inwards the active site (0.81 Å), making the E166 and N170 side chains shift to create a proper hydrogen bonding network. Binding of REL also disturbs the hydrophobic patch formed by Y105, P107, and Y129, likely due to the piperidine ring of REL that creates clashes with these residues. Also, a remarkable change in the positioning of the N104 sidechain is also affected by the piperidine ring. Therefore, differences in the kinetic behavior of REL against class A ß-lactamases seem to rely, at least in part, on differences in the residues being involved in the association and stabilization of the inhibitor before hydrolysis. Our data provide the biochemical and structural basis for REL effectiveness against CTX-M-producing Gram-negative pathogens and essential details for further DBO design. Imipenem/REL remains an important choice for dealing with isolates co-producing CTX-M with other ß-lactamases.
Assuntos
Compostos Azabicíclicos , Inibidores de beta-Lactamases , beta-Lactamases , Compostos Azabicíclicos/farmacologia , Compostos Azabicíclicos/química , beta-Lactamases/genética , beta-Lactamases/metabolismo , beta-Lactamases/química , Inibidores de beta-Lactamases/farmacologia , Inibidores de beta-Lactamases/química , Cristalografia por Raios X , Antibacterianos/farmacologia , Imipenem/farmacologia , Imipenem/química , Ceftazidima/farmacologia , Testes de Sensibilidade Microbiana , Domínio CatalíticoRESUMO
BACKGROUND: We demonstrated therapeutic nonequivalence of "bioequivalent" generics for meropenem, but there is no data with generics of other carbapenems. METHODS: One generic product of imipenem-cilastatin was compared with the innovator in terms of in vitro susceptibility testing, pharmaceutical equivalence, pharmacokinetic (PK) and pharmacodynamic (PD) equivalence in the neutropenic mouse thigh, lung and brain infection models. Both pharmaceutical forms were then subjected to analytical chemistry assays (LC/MS). RESULTS AND CONCLUSION: The generic product had 30% lower concentration of cilastatin compared with the innovator of imipenem-cilastatin. Regarding the active pharmaceutical ingredient (imipenem), we found no differences in MIC, MBC, concentration or potency or AUC, confirming equivalence in terms of in vitro activity. However, the generic failed therapeutic equivalence in all three animal models. Its Emax against S. aureus in the thigh model was consistently lower, killing from 0.1 to 7.3 million less microorganisms per gram in 24 hours than the innovator (P = 0.003). Against K. pneumoniae in the lung model, the generic exhibited a conspicuous Eagle effect fitting a Gaussian equation instead of the expected sigmoid curve of the Hill model. In the brain infection model with P. aeruginosa, the generic failed when bacterial growth was >4 log10 CFU/g in 24 hours, but not if it was less than 2.5 log10 CFU/g. These large differences in the PD profile cannot be explained by the lower concentration of cilastatin, and rather suggested a failure attributable to the imipenem constituent of the generic product. Analytical chemistry assays confirmed that, besides having 30% less cilastatin, the generic imipenem was more acidic, less stable, and exhibited four different degradation masses that were absent in the innovator.
Assuntos
Bactérias/efeitos dos fármacos , Infecções Bacterianas/sangue , Combinação Imipenem e Cilastatina/farmacocinética , Medicamentos Genéricos/farmacocinética , Imipenem/química , Animais , Infecções Bacterianas/tratamento farmacológico , Infecções Bacterianas/microbiologia , Cilastatina/química , Cilastatina/farmacocinética , Cilastatina/farmacologia , Combinação Imipenem e Cilastatina/química , Combinação Imipenem e Cilastatina/farmacologia , Modelos Animais de Doenças , Estabilidade de Medicamentos , Medicamentos Genéricos/química , Medicamentos Genéricos/farmacologia , Humanos , Imipenem/farmacocinética , Imipenem/farmacologia , Klebsiella pneumoniae/efeitos dos fármacos , Camundongos , Testes de Sensibilidade Microbiana , Pseudomonas aeruginosa/efeitos dos fármacos , Staphylococcus aureus/efeitos dos fármacos , Equivalência TerapêuticaRESUMO
Carbapenems are "last resort" ß-lactam antibiotics used to treat serious and life-threatening health care-associated infections caused by multidrug-resistant Gram-negative bacteria. Unfortunately, the worldwide spread of genes coding for carbapenemases among these bacteria is threatening these life-saving drugs. Metallo-ß-lactamases (MßLs) are the largest family of carbapenemases. These are Zn(II)-dependent hydrolases that are active against almost all ß-lactam antibiotics. Their catalytic mechanism and the features driving substrate specificity have been matter of intense debate. The active sites of MßLs are flanked by two loops, one of which, loop L3, was shown to adopt different conformations upon substrate or inhibitor binding, and thus are expected to play a role in substrate recognition. However, the sequence heterogeneity observed in this loop in different MßLs has limited the generalizations about its role. Here, we report the engineering of different loops within the scaffold of the clinically relevant carbapenemase NDM-1. We found that the loop sequence dictates its conformation in the unbound form of the enzyme, eliciting different degrees of active-site exposure. However, these structural changes have a minor impact on the substrate profile. Instead, we report that the loop conformation determines the protonation rate of key reaction intermediates accumulated during the hydrolysis of different ß-lactams in all MßLs. This study demonstrates the existence of a direct link between the conformation of this loop and the mechanistic features of the enzyme, bringing to light an unexplored function of active-site loops on MßLs.
Assuntos
Antibacterianos/química , Ceftazidima/química , Imipenem/química , Meropeném/química , Zinco/química , beta-Lactamases/química , Sequência de Aminoácidos , Antibacterianos/metabolismo , Domínio Catalítico , Cefepima/química , Cefepima/metabolismo , Cefotaxima/química , Cefotaxima/metabolismo , Ceftazidima/metabolismo , Clonagem Molecular , Cristalografia por Raios X , Escherichia coli/genética , Escherichia coli/metabolismo , Expressão Gênica , Vetores Genéticos/química , Vetores Genéticos/metabolismo , Imipenem/metabolismo , Cinética , Meropeném/metabolismo , Modelos Moleculares , Piperacilina/química , Piperacilina/metabolismo , Ligação Proteica , Conformação Proteica em alfa-Hélice , Conformação Proteica em Folha beta , Engenharia de Proteínas , Domínios e Motivos de Interação entre Proteínas , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Especificidade por Substrato , Zinco/metabolismo , Resistência beta-Lactâmica , beta-Lactamases/genética , beta-Lactamases/metabolismoRESUMO
Carbapenems show recognized instability in aqueous solutions; therefore some care must be taken in their handling and preparation and their use in the hospital environment. The stability and degradation products of imipenem were investigated from conditions that simulate its clinical use. For this, a simple stability-indicating method by HPLC-DAD was validated with a focus on the quantitation of drug concentration remaining from infusion solutions (sodium chloride 0.9% and glucose 5%). The degradation products formed were identified by high-resolution mass spectrometry (ESI-Q-TOF-MS/MS), with detection of the [M + H]+ ions at m/z 318 (DP-1), m/z 599 (DP-2) and m/z 658 (DP-3). The most probable elemental compositions were obtained with a high degree of confidence, where the error between the masses observed and calculated was 1.25 ppm for DP-1, -0.33 ppm for DP-2 and 1.82 ppm for DP-3. The DP-1 degradation product resulted from cleavage of the ß-lactam ring; DP-2 corresponded to the drug dimer; and DP-3 was generated from the interaction between imipenem and cilastatin. The proposed method provides a safe and reliable alternative for the quantitation of imipenem, and the stability data obtained by ESI-Q-TOF help in understanding the drug behavior under the conditions of clinical use.
Assuntos
Imipenem/análise , Imipenem/química , Espectrometria de Massas/métodos , Cromatografia Líquida de Alta Pressão , Contaminação de Medicamentos , Estabilidade de Medicamentos , Imipenem/normas , Modelos Lineares , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
OBJECTIVES: The aim of this study was to characterise OXA-258 variants and other features that may contribute to carbapenem resistance in Achromobacter ruhlandii. METHODS: Kinetic parameters for purified OXA-258a and OXA-258b were determined measuring the rate of hydrolysis of a representative group of antimicrobial agents. Whole-genome shotgun sequencing was performed on A. ruhlandii 38 (producing OXA-258a) and A. ruhlandii 319 (producing OXA-258b), and in silico analysis of antimicrobial resistance determinants was conducted. Substrates of the AxyABM efflux pump were investigated by inhibition assays using phenylalanine-arginine ß-naphthylamide (PAßN). Outer membrane protein profiles were resolved by 12% sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). RESULTS: Kinetic measurements of purified OXA-258 variants displayed an overall weak catalytic efficiency toward ß-lactams. A detectable hydrolysis of imipenem was observed. In silico genomic analysis confirmed the presence of 32 and 35 putative efflux pump-encoding genes in A. ruhlandii strains 38 and 319, respectively. Complete sequences for AxyABM and AxyXY efflux pumps, previously described in Achromobacter xylosoxidans, were detected. Decreases in the MICs for chloramphenicol, nalidixic acid and trimethoprim/sulfamethoxazole were observed in the presence of the inhibitor PAßN, suggesting that these antibiotics are substrates of AxyABM. AxyXY-encoding genes of A. ruhlandii 38 and A. ruhlandii 319 displayed 99% identity. No differences were observed in the outer membrane protein profiles. CONCLUSIONS: The contribution of OXA-258 enzymes to the final ß-lactam resistance profile may be secondary. Further studies on other putative resistance markers identified in the whole-genome analysis should be conducted to understand the carbapenem resistance observed in A. ruhlandii.
Assuntos
Achromobacter/enzimologia , Antibacterianos/farmacologia , Proteínas da Membrana Bacteriana Externa/genética , Sequenciamento Completo do Genoma/métodos , Resistência beta-Lactâmica , beta-Lactamases/genética , Achromobacter/genética , Antibacterianos/química , Proteínas de Bactérias/genética , Cloranfenicol/química , Cloranfenicol/farmacologia , Simulação por Computador , Variação Genética , Hidrólise , Imipenem/química , Imipenem/farmacologia , Testes de Sensibilidade Microbiana , Ácido Nalidíxico/química , Ácido Nalidíxico/farmacologia , Combinação Trimetoprima e Sulfametoxazol/química , Combinação Trimetoprima e Sulfametoxazol/farmacologiaRESUMO
This paper deals with the photochemical fate of two representative carbapenem antibiotics, namely imipenem and meropenem, in aqueous solutions under solar radiation. The analytical method employed for the determination of the target compounds in various aqueous matrices, such as ultrapure water, municipal wastewater treatment plant effluents, and river water, at environmentally relevant concentrations, was liquid chromatography coupled with hybrid triple quadrupole-linear ion trap-mass spectrometry. The absorption spectra of both compounds were measured in aqueous solutions at pH values from 6 to 8, and both compounds showed a rather strong absorption band centered at about 300 nm, while their molar absorption coefficient was in the order from 9 × 103-104 L mol-1 cm-1. The kinetics of the photochemical degradation of the target compounds was studied in aqueous solutions under natural solar radiation in a solar reactor with compound parabolic collectors. It was found that the photochemical degradation of both compounds at environmentally relevant concentrations follows first order kinetics and the quantum yield was in the order of 10-3 mol einsten-1. Several parameters were studied, such as solution pH, the presence of nitrate ions and humic acids, and the effect of water matrix. In all cases, it was found that the presence of various organic and inorganic constituents in the aqueous matrices do not contribute significantly, either positively or negatively, to the photochemical degradation of both compounds under natural solar radiation. In a final set of photolysis experiments, the effect of the level of irradiance was studied under simulated solar radiation and it was found that the quantum yield for the direct photodegradation of both compounds remained practically constant by changing the incident solar irradiance from 28 to 50 W m-2.
Assuntos
Carbapenêmicos/efeitos da radiação , Imipenem/efeitos da radiação , Tienamicinas/efeitos da radiação , Poluentes Químicos da Água/efeitos da radiação , Carbapenêmicos/análise , Carbapenêmicos/química , Cromatografia Líquida , Substâncias Húmicas/análise , Imipenem/análise , Imipenem/química , Cinética , Meropeném , Fotólise , Rios/química , Luz Solar , Tienamicinas/análise , Tienamicinas/química , Águas Residuárias/química , Água/química , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/químicaRESUMO
Carbapenem-resistant Enterobacteriaceae threaten human health, since carbapenems are last resort drugs for infections by such organisms. Metallo-ß-lactamases (MßLs) are the main mechanism of resistance against carbapenems. Clinically approved inhibitors of MBLs are currently unavailable as design has been limited by the incomplete knowledge of their mechanism. Here, we report a biochemical and biophysical study of carbapenem hydrolysis by the B1 enzymes NDM-1 and BcII in the bi-Zn(II) form, the mono-Zn(II) B2 Sfh-I and the mono-Zn(II) B3 GOB-18. These MßLs hydrolyse carbapenems via a similar mechanism, with accumulation of the same anionic intermediates. We characterize the Michaelis complex formed by mono-Zn(II) enzymes, and we identify all intermediate species, enabling us to propose a chemical mechanism for mono and binuclear MßLs. This common mechanism open avenues for rationally designed inhibitors of all MßLs, notwithstanding the profound differences between these enzymes' active site structure, ß-lactam specificity and metal content.Carbapenem-resistant bacteria pose a major health threat by expressing metallo-ß-lactamases (MßLs), enzymes able to hydrolyse these life-saving drugs. Here the authors use biophysical and computational methods and show that different MßLs share the same reaction mechanism, suggesting new strategies for drug design.
Assuntos
Carbapenêmicos/metabolismo , Zinco/metabolismo , beta-Lactamases/química , beta-Lactamases/metabolismo , Carbapenêmicos/química , Hidrólise , Imipenem/química , Imipenem/metabolismo , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Simulação de Dinâmica Molecular , Espectroscopia por Absorção de Raios XRESUMO
The single crystal X-ray structure of the extracellular portion of the L,D-transpeptidase (ex-LdtMt2 - residues 120-408) enzyme was recently reported. It was observed that imipenem and meropenem inhibit activity of this enzyme, responsible for generating L,D-transpeptide linkages in the peptidoglycan layer of Mycobacterium tuberculosis. Imipenem is more active and isothermal titration calorimetry experiments revealed that meropenem is subjected to an entropy penalty upon binding to the enzyme. Herein, we report a molecular modeling approach to obtain a molecular view of the inhibitor/enzyme interactions. The average binding free energies for nine commercially available inhibitors were calculated using MM/GBSA and Solvation Interaction Energy (SIE) approaches and the calculated energies corresponded well with the available experimentally observed results. The method reproduces the same order of binding energies as experimentally observed for imipenem and meropenem. We have also demonstrated that SIE is a reasonably accurate and cost-effective free energy method, which can be used to predict carbapenem affinities for this enzyme. A theoretical explanation was offered for the experimental entropy penalty observed for meropenem, creating optimism that this computational model can serve as a potential computational model for other researchers in the field.
Assuntos
Parede Celular/metabolismo , Imipenem/farmacologia , Modelos Moleculares , Mycobacterium tuberculosis/efeitos dos fármacos , Mycobacterium tuberculosis/enzimologia , Peptidil Transferases/metabolismo , Tienamicinas/farmacologia , Parede Celular/efeitos dos fármacos , Imipenem/química , Meropeném , Simulação de Acoplamento Molecular , Simulação de Dinâmica Molecular , Mycobacterium tuberculosis/citologia , Peptidil Transferases/química , Ligação Proteica/efeitos dos fármacos , Termodinâmica , Tienamicinas/químicaRESUMO
Meropenem es un compuesto del grupo carbapenem, con un amplio espectro antibacteriano y rápida actividad bactericida. Esta actividad es superior sobre bacilos gram negativos fermentadores como klebsiella sp y E. coli, e inferior sobre pseudomonas sp. Y A. baumannii. En cuanto a estas dos últimas bacterias, hay que hacer notar que la actividad de meropenem sobre pseudomonas sp pareciera ser bastante más rápida que la que ocurre sobre acinetobacter sp, aún cuando las CIM aparecen similares. La muerte bacteriana es más rápida sobre P. aeruginosa
Assuntos
Humanos , Infecções Bacterianas/tratamento farmacológico , Carbapenêmicos/química , Resistência beta-Lactâmica , Carbapenêmicos/farmacologia , Bactérias Gram-Negativas/efeitos dos fármacos , Imipenem/química , Porinas/efeitos dos fármacos , Resistência a Múltiplos Medicamentos , Tienamicinas/químicaRESUMO
Meropenem is more stable than imipenem to renal dehydropeptidase I and can be used as a monodrug. It is bactericidal against most grampositive and gramnegative, aerobic and anaerobic species. Compared to imipenem, meropenem is more active against pseudomonas aeuginosa, burkholderia cepacia and some multiresistant nosocomial gramnegative strains because it is less inductor of extended spectrum B lactamases but may favor resistance against other antibiotic groups by an efflux pump induction. Its systemicdistribution in the extracellular space includes the central nervous system and is most excreted by glomerular filtration. As meropenem is more soluble than imipenem, it can be administered in bolus. Security profile: it rarely causes seizures, a frecuent effect observed with imipenem during tratment of bacterial meningitis in children. Other adverse reactions (local pain, pruritus and diarrhea) are as frecuent as described with imipenem