Novel approach to quorum quenching: rational design of antibacterials in combination with hexahistidine-tagged organophosphorus hydrolase.

N-acyl homoserine lactones (AHLs) are quorum sensing (QS) signal molecules used by most Gram-negative pathogenic bacteria. In this article the lactonase activity of the preparations based on hexahistidine-tagged organophosphorus hydrolase (His6-OPH) towards AHLs was studied. Initially, three of the most interesting ß-lactam antibiotics were selected from seven that were trialed during molecular docking to His6-OPH. Combinations of antibiotics (meropenem, imipenem, ceftriaxone) and His6-OPH taken in the native form or in the form of non-covalent enzyme-polyelectrolyte complexes (EPCs) with poly(glutamic acid) or poly(aspartic acid) were obtained and investigated. The lactonase activity of the preparations was investigated under different physical-chemical conditions in the hydrolysis of AHLs [N-butyryl-D,L-homoserine lactone, N-(3-oxooctanoyl)-D,L-homoserine lactone, N-(3-oxododecanoyl)-L-homoserine lactone]. An increased efficiency of catalytic action and stability of the lactonase activity of His6-OPH was shown for its complexes with antibiotics and was confirmed in trials with bacterial strains. The broadening of the catalytic action of the enzyme against AHLs was revealed in the presence of the meropenem. Results of molecular docking of AHLs to the surface of the His6-OPH dimer in the presence of antibiotics allowed proposing the mechanism of such interference based on a steric repulsion of the carbon chain of hydrolyzed AHLs by the antibiotics bounded to the enzyme surface.

Synthesis and biological evaluation of the progenitor of a new class of cephalosporin analogues, with a particular focus on structure-based computational analysis.

We present the synthesis and biological evaluation of the prototype of a new class of cephalosporins, containing an additional isolated beta lactam ring with two phenyl substituents. This new compound is effective against Gram positive microorganisms, with a potency similar to that of ceftriaxone, a cephalosporin widely used in clinics and taken as a reference, and with no cytotoxicity against two different human cell lines, even at a concentration much higher than the minimal inhibitory concentration tested. Additionally, a deep computational analysis has been conducted with the aim of understanding the contribution of its moieties to the binding energy towards several penicillin-binding proteins from both Gram positive and Gram negative bacteria. All these results will help us developing derivatives of this compound with improved chemical and biological properties, such as a broader spectrum of action and/or an increased affinity towards their molecular targets.

Labelling of ceftriaxone with (99m) Tc and its bio-evaluation as an infection imaging agent.

Differentiation of bacterial and sterile inflammation will have a significant impact on the current clinical practice. Ceftriaxone (CTRX) was labelled with (99m) Tc and assessed for its ability to depict infection on scintigraphy. Stoichiometry was performed to optimize labelling parameters. Stability and bacterial binding was verified and biodistribution pattern was seen in normal, infected/inflamed animal models. (99m) Tc-CTRX prepared at pH 7 with stannous chloride of 50 µg, ligand of 30 mg, and boiling for 10 min gave labelling yield of 96.2 ± 0.2% with good stability. In vitro binding was higher for Escherichia coli than Staphylococcus aureus. Biodistribution in normal rats showed high uptake in hepatobiliary system, gut and urinary system. In animal models induced with infection or inflammation, lesion to normal ratios at 4 h were 2.36 ± 0.21, 12.66 ± 1.44 and 1.40 ± 0.01 with S. aureus infection, E. coli infection and turpentine oil inflammation, respectively. Infection specificity especially for E. coli was also confirmed on scintigraphic findings. Ceftriaxone can be labelled with (99m) Tc with high labelling yield at pH compatible with that of blood. Our preparation has shown stability in vitro and in human serum, and binds preferentially with bacteria. (99m) Tc-CTRX scintigraphy can be used to delineate sites of active infection and to differentiate infection and inflammation.

Synthesis, spectral, thermal and antimicrobial studies of some new tri metallic biologically active ceftriaxone complexes.

Iron, cobalt, nickel and copper complexes of ceftriaxone were prepared in 1:3 ligand:metal ratio to examine the ligating properties of the different moieties of the drug. The complexes were found to have high percentages of coordinated water molecules. The modes of bonding were discussed depending on the infrared spectral absorption peaks of the different allowed vibrations. The Nujol mull electronic absorption spectra and the magnetic moment values indicated the Oh geometry of the metal ions in the complexes. The ESR spectra of the iron, cobalt, and copper complexes were determined and discussed. The thermal behaviors of the complexes were studied by TG and DTA techniques. The antimicrobial activities of the complexes were examined and compared to that of the ceftriaxone itself.

Obtención de ceftriaxona sódica cristalina / Obtainment of crystaline sodium ceftriaxone

La ceftriaxona sódica es uno de los antibióticos Beta lactámicos pertenecientes a las cefalosporinas aminotiazólicas parenterales de tercera generación, siendo uno de los productos principales de nuestra planta de inyectables.En el marco del proyecto de investigación “Obtención de antibióticos cefalosporánicos estériles” se han desarrollado procedimientos de síntesis de este producto y se contempla la tarea de obtención de ceftriaxona sódica cristalina ya que entre los parámetros establecidos por las monografías oficiales para el control de calidad se encuentra la “cristalinidad”.Nuestro trabajo establece que mediante una cristalización controlada en medio etanol-agua y secando por liofilización se obtiene ceftriaxona sódica cuyo espectro de difracción de rayos X coincide con el del Rocephin, producto líder en el mercado internacional(AU)

Correlation between structure and biological properties of cephalosporins: the discovery of ceftriaxone.

A research programme on cephalosporins was conducted in the author's laboratory with the aim of creating compounds with improved antibacterial and pharmacokinetic properties. In the first phase of this programme, great attention was paid to the study of how the structure of a 3-heterocyclic-thiomethyl side chain is capable of influencing antibiotic activity within a large series of model compounds possessing the same acyl side chain (2-thienylacetyl) as cephalothin. Several structural and physico-chemical features of the heterocyclic thiols used and the corresponding cephalosporins were correlated with in vitro and in vivo activity. As a result of these studies, the enolic 2-methyl-6-hydroxy-5-oxo-as-triazine-3-thiol was identified as the most interesting substituent, since the corresponding cephalosporin showed a valuable resistance breakthrough against several cephalothin-resistant Proteus strains. Consequently, further studies involving the use of different acyl side chains were performed. The introduction of the basic 2-(2-amino-4-thiazolyl)-2-(Z)-methoxyimino-acetyl side chain finally led to ceftriaxone, which has a very long elimination half-life of 8 hours, high beta-lactamase stability and extremely high chemotherapeutic efficacy against a broad spectrum of Gram-positive and Gram-negative pathogens. Owing to these properties, ceftriaxone is the first beta-lactam antibiotic suitable for once-daily administration.