RESUMEN

Antimicrobial resistance is a global public health threat. Metallo-ß-lactamases (MBLs) inactivate ß-lactam antibiotics, including carbapenems, are disseminating among Gram-negative bacteria, and lack clinically useful inhibitors. The evolving bisthiazolidine (BTZ) scaffold inhibits all three MBL subclasses (B1-B3). We report design, synthesis, and evaluation of BTZ analogues. Structure-activity relationships identified the BTZ thiol as essential, while carboxylate is replaceable, with its removal enhancing potency by facilitating hydrophobic interactions within the MBL active site. While the introduction of a flexible aromatic ring is neutral or detrimental for inhibition, a rigid (fused) ring generated nM benzobisheterocycle (BBH) inhibitors that potentiated carbapenems against MBL-producing strains. Crystallography of BBH:MBL complexes identified hydrophobic interactions as the basis of potency toward B1 MBLs. These data underscore BTZs as versatile, potent broad-spectrum MBL inhibitors (with activity extending to enzymes refractory to other inhibitors) and provide a rational approach to further improve the tricyclic BBH scaffold.

Asunto(s)

Antibacterianos , Inhibidores de beta-Lactamasas , Inhibidores de beta-Lactamasas/farmacología , Inhibidores de beta-Lactamasas/química , Antibacterianos/farmacología , Antibacterianos/química , beta-Lactamasas/química , Carbapenémicos , Bacterias Gramnegativas

RESUMEN

Objectives: Identify molecular mechanisms responsible for the in vitro non-susceptibility to ceftolozane/tazobactam (TOL) in a group of 158 clinical isolates of Pseudomonas aeruginosa from five Latin American countries collected before the introduction of TOL into the clinical practice. Methods: Clinical isolates of P. aeruginosa (n = 504) were collected between January 2016 and October 2017 from 20 hospitals located in Argentina, Brazil, Chile, Colombia, and Mexico. Minimum inhibitory concentrations (MICs) to TOL were determined by standard broth microdilution and interpreted according to CLSI breakpoints. Initially, production of carbapenemases in TOL non-susceptible isolates was assessed by Rapidec® followed by qPCR to detect bla KPC, bla NDM-1, bla VIM, and bla IMP. Illumina® WGS was performed for isolates in which non-susceptibility to TOL was not mediated by carbapenemases. Results: A total of 158 (31.3%) isolates were non-susceptible to TOL. In 74 (46.8%) of these isolates, non-susceptibility to TOL was explained by the production of at least one carbapenemase. WGS revealed that some isolates carried ESBLs, mutated bla PDC and ampD, associated with decreased susceptibility to TOL. Conclusion: Substitutions found in PDC and carbapenemase production were the most common presumed mechanisms of resistance to TOL detected in this study. This study shows that epidemiological surveillance is warranted to monitor the emergence of novel mechanisms of resistance to TOL that might compromise its clinical utility.

RESUMEN

BACKGROUND: Ceftolozane/tazobactam (C/T) is a combination of an antipseudomonal oxyiminoaminothiazolyl cephalosporin with potent in vitro activity against Pseudomonas aeruginosa and tazobactam, a known ß-lactamase inhibitor. The aim of this study was to evaluate the activity of C/T against clinical isolates of P. aeruginosa and Enterobacterales collected from five Latin American countries between 2016 and 2017, before its clinical use in Latin America, and to compare it with the activity of other available broad-spectrum antimicrobial agents. METHODS: a total of 2760 clinical isolates (508 P. aeruginosa and 2252 Enterobacterales) were consecutively collected from 20 hospitals and susceptibility to C/T and comparator agents was tested and interpreted following the current guidelines. RESULTS: according to the CLSI breakpoints, 68.1% (346/508) of P. aeruginosa and 83.9% (1889/2252) of Enterobacterales isolates were susceptible to C/T. Overall, C/T demonstrated higher in vitro activity than currently available cephalosporins, piperacillin/tazobactam and carbapenems when tested against P. aeruginosa, and its performance in vitro was comparable to fosfomycin. When tested against Enterobacterales, it showed higher activity than cephalosporins and piperacillin/tazobactam, and similar activity to ertapenem. CONCLUSIONS: these results show that C/T is an active ß-lactam agent against clinical isolates of P. aeruginosa and Enterobacterales.

RESUMEN

Due to their superior tolerability and efficacy, ß-lactams are the most potent and prescribed class of antibiotics in the clinic. The emergence of resistance to those antibiotics, mainly due to the production of bacterial enzymes called ß-lactamases, has been partially solved by the introduction of ß-lactamase inhibitors, which restore the activity of otherwise obsolete molecules. This solution is limited because currently available ß-lactamase inhibitors only work against serine ß-lactamases, whereas metallo-ß-lactamases continue to spread, evolve, and confer resistance to all ß-lactams, including carbapenems. Furthermore, the increased use of antibiotics to treat secondary bacterial pneumonia in severely sick patients with COVID-19 might exacerbate the problem of antimicrobial resistance. In this Personal View, we summarise the main advances accomplished in this area of research, emphasise the main challenges that need to be solved, and the importance of research on inhibitors for metallo-B-lactamases amidst the current pandemic.

Asunto(s)

Antibacterianos/farmacología , Bacterias/efectos de los fármacos , Farmacorresistencia Bacteriana , Salud Global , Inhibidores de beta-Lactamasas/uso terapéutico , beta-Lactamas/farmacología , Bacterias/enzimología , Bacterias/patogenicidad , COVID-19/complicaciones , COVID-19/microbiología , Coinfección/tratamiento farmacológico , Coinfección/microbiología , Humanos

RESUMEN

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.

Asunto(s)

Antibacterianos/química , Ceftazidima/química , Imipenem/química , Meropenem/química , Zinc/química , beta-Lactamasas/química , Secuencia de Aminoácidos , Antibacterianos/metabolismo , Dominio Catalítico , Cefepima/química , Cefepima/metabolismo , Cefotaxima/química , Cefotaxima/metabolismo , Ceftazidima/metabolismo , Clonación Molecular , Cristalografía por Rayos X , Escherichia coli/genética , Escherichia coli/metabolismo , Expresión Génica , Vectores Genéticos/química , Vectores Genéticos/metabolismo , Imipenem/metabolismo , Cinética , Meropenem/metabolismo , Modelos Moleculares , Piperacilina/química , Piperacilina/metabolismo , Unión Proteica , Conformación Proteica en Hélice alfa , Conformación Proteica en Lámina beta , Ingeniería de Proteínas , Dominios y Motivos de Interacción de Proteínas , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Alineación de Secuencia , Homología de Secuencia de Aminoácido , Especificidad por Sustrato , Zinc/metabolismo , Resistencia betalactámica , beta-Lactamasas/genética , beta-Lactamasas/metabolismo

RESUMEN

PER ß-lactamases are an emerging family of extended-spectrum ß-lactamases (ESBL) found in Gram-negative bacteria. PER ß-lactamases are unique among class A enzymes as they possess an inverted omega (Ω) loop and extended B3 ß-strand. These singular structural features are hypothesized to contribute to their hydrolytic profile against oxyimino-cephalosporins (e.g., cefotaxime and ceftazidime). Here, we tested the ability of avibactam (AVI), a novel non-ß-lactam ß-lactamase inhibitor to inactivate PER-2. Interestingly, the PER-2 inhibition constants (i.e., k2/K = 2 × 103 ± 0.1 × 103 M-1 s-1, where k2 is the rate constant for acylation (carbamylation) and K is the equilibrium constant) that were obtained when AVI was tested were reminiscent of values observed testing the inhibition by AVI of class C and D ß-lactamases (i.e., k2/K range of ≈103 M-1 s-1) and not class A ß-lactamases (i.e., k2/K range, 104 to 105 M-1 s-1). Once AVI was bound, a stable complex with PER-2 was observed via mass spectrometry (e.g., 31,389 ± 3 atomic mass units [amu] → 31,604 ± 3 amu for 24 h). Molecular modeling of PER-2 with AVI showed that the carbonyl of AVI was located in the oxyanion hole of the ß-lactamase and that the sulfate of AVI formed interactions with the ß-lactam carboxylate binding site of the PER-2 ß-lactamase (R220 and T237). However, hydrophobic patches near the PER-2 active site (by Ser70 and B3-B4 ß-strands) were observed and may affect the binding of necessary catalytic water molecules, thus slowing acylation (k2/K) of AVI onto PER-2. Similar electrostatics and hydrophobicity of the active site were also observed between OXA-48 and PER-2, while CTX-M-15 was more hydrophilic. To demonstrate the ability of AVI to overcome the enhanced cephalosporinase activity of PER-2 ß-lactamase, we tested different ß-lactam-AVI combinations. By lowering MICs to ≤2 mg/liter, the ceftaroline-AVI combination could represent a favorable therapeutic option against Enterobacteriaceae expressing blaPER-2 Our studies define the inactivation of the PER-2 ESBL by AVI and suggest that the biophysical properties of the active site contribute to determining the efficiency of inactivation.

Asunto(s)

Compuestos de Azabiciclo/farmacología , beta-Lactamasas/farmacología , Antibacterianos/farmacología , Pruebas de Sensibilidad Microbiana , beta-Lactamasas/metabolismo

RESUMEN

Pathogenic Gram-negative bacteria resistant to almost all ß-lactam antibiotics are a major public health threat. Zn(II)-dependent or metallo-ß-lactamases (MBLs) produced by these bacteria inactivate most ß-lactam antibiotics, including the carbapenems, which are "last line therapies" for life-threatening Gram-negative infections. NDM-1 is a carbapenemase belonging to the MBL family that is rapidly spreading worldwide. Regrettably, inhibitors of MBLs are not yet developed. Here we present the bisthiazolidine (BTZ) scaffold as a structure with some features of ß-lactam substrates, which can be modified with metal-binding groups to target the MBL active site. Inspired by known interactions of MBLs with ß-lactams, we designed four BTZs that behave as in vitro NDM-1 inhibitors with Ki values in the low micromolar range (from 7 ± 1 to 19 ± 3 µM). NMR spectroscopy demonstrated that they inhibit hydrolysis of imipenem in NDM-1-producing Escherichia coli. In vitro time kill cell-based assays against a variety of bacterial strains harboring blaNDM-1 including Acinetobacter baumannii show that the compounds restore the antibacterial activity of imipenem. A crystal structure of the most potent heterocycle (L-CS319) in complex with NDM-1 at 1.9 Å resolution identified both structural determinants for inhibitor binding and opportunities for further improvements in potency.

Asunto(s)

Infecciones por Enterobacteriaceae/epidemiología , Infecciones por Enterobacteriaceae/microbiología , Enterobacteriaceae/clasificación , Enterobacteriaceae/enzimología , beta-Lactamasas/metabolismo , Antibacterianos/farmacología , Colombia/epidemiología , Electroforesis en Gel de Campo Pulsado , Enterobacteriaceae/genética , Enterobacteriaceae/aislamiento & purificación , Genotipo , Humanos , Pruebas de Sensibilidad Microbiana , Epidemiología Molecular , Tipificación Molecular

RESUMEN

OXA-72 has been reported in few countries around the world. We report the first case in Colombia in an Acinetobacter pittii clinical isolate. The arrival of a new OXA, into a country with high endemic resistance, poses a significant threat, especially because the potential for widespread dissemination is considerable.

Asunto(s)

Acinetobacter/enzimología , Proteínas Bacterianas/metabolismo , beta-Lactamasas/metabolismo , Acinetobacter/efectos de los fármacos , Antibacterianos/farmacología , Proteínas Bacterianas/genética , Colombia , Pruebas de Sensibilidad Microbiana , beta-Lactamasas/genética

RESUMEN

We report the emergence of a novel VIM variant (VIM-24) in a Klebsiella pneumoniae isolate in Colombia. The isolate displays MICs for carbapenems below the resistance breakpoints, posing a real challenge for its detection. The blaVIM-24 gene was located within a class 1 integron carried on a large plasmid. Further studies are needed to clarify its epidemiological and clinical impact.

Asunto(s)

Klebsiella pneumoniae/efectos de los fármacos , Klebsiella pneumoniae/enzimología , beta-Lactamasas/metabolismo , Antibacterianos/farmacología , Colombia , Farmacorresistencia Bacteriana Múltiple/genética , Integrones/genética , Klebsiella pneumoniae/genética , Pruebas de Sensibilidad Microbiana , Plásmidos/química , beta-Lactamasas/genética