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Study Group on Mechanisms of Action and Resistance to Antimicrobials (GEMARA) on behalf of the Spanish Society of Infectious Diseases and Clinical Microbiology (SEIMC)., Klebsiella pneumoniae is an opportunistic Gram-negative pathogen that employs different strategies (resistance and persistence) to counteract antibiotic treatments. This study aimed to search for new means of combatting imipenem-resistant and persister strains of K. pneumoniae by repurposing the anticancer drug mitomycin C as an antimicrobial agent and by combining the drug and the conventional antibiotic imipenem with the lytic phage vB_KpnM-VAC13. Several clinical K. pneumoniae isolates were characterized, and an imipenem-resistant isolate (harboring OXA-245 β-lactamase) and a persister isolate were selected for study. The mitomycin C and imipenem MICs for both isolates were determined by the broth microdilution method. Time-kill curve data were obtained by optical density at 600 nm (OD600) measurement and CFU enumeration in the presence of each drug alone and with the phage. The frequency of occurrence of mutants resistant to each drug and the combinations was also calculated, and the efficacy of the combination treatments was evaluated using an in vivo infection model (Galleria mellonella). The lytic phage vB_KpnM-VAC13 and mitomycin C had synergistic effects on imipenem-resistant and persister isolates, both in vitro and in vivo. The phage-imipenem combination successfully killed the persisters but not the imipenem-resistant isolate harboring OXA-245 β-lactamase. Interestingly, the combinations decreased the emergence of in vitro resistant mutants of both isolates. Combinations of the lytic phage vB_KpnM-VAC13 with mitomycin C and imipenem were effective against the persister K. pneumoniae isolate. The lytic phage-mitomycin C combination was also effective against imipenem-resistant K. pneumoniae strains harboring OXA-245 β-lactamase., This study was funded by grants PI16/01163 and PI19/00878 awarded to M. Tomás within the State Plan for R+D+I 2013–2016 (National Plan for Scientific Research, Technological Development and Innovation 2008–2011) and cofinanced by the ISCIII-Deputy General Directorate for Evaluation and Promotion of Research–European Regional Development Fund and Instituto de Salud Carlos III FEDER, Spanish Network for the Research in Infectious Diseases (REIPI; RD16/0016/0001, RD16/0016/0006, and RD16/CIII/0004/0002) and by the Study Group on Mechanisms of Action and Resistance to Antimicrobials, GEMARA (SEIMC; http://www.seimc.org/). M. Tomás was financially supported by the Miguel Servet Research Program (SERGAS and ISCIII). I. Bleriot was financially supported by pFIS program (ISCIII, FI20/00302). O. Pacios and M. López were financially supported by grants IN606A-2020/035 and IN606B-2018/008, respectively (GAIN, Xunta de Galicia), and P. Domingo-Calap was financially supported by the ESCMID Research Grant 20200063.

Klebsiella pneumoniae is a human pathogen that worsens the prognosis of many immuno compromised patients. Here, we annotated and compared the genomes of two lytic phages that infect clinical strains of K. pneumoniae (vB_KpnM-VAC13 and vB_KpnM-VAC66) and phenotypically char acterized vB_KpnM-VAC66 (time of adsorption of 12 min, burst size of 31.49 ± 0.61 PFU/infected cell, and a host range of 20.8% of the tested strains). Transmission electronic microscopy showed that vB_KpnM-VAC66 belongs to the Myoviridae family. The genomic analysis of the phage vB_KpnM VAC66 revealed that its genome encoded 289 proteins. When compared to the genome of vB_KpnM VAC13, they showed a nucleotide similarity of 97.56%, with a 93% of query cover, and the phylo genetic study performed with other Tevenvirinae phages showed a close common ancestor. How ever, there were 21 coding sequences which differed. Interestingly, the main differences were that vB_KpnM-VAC66 encoded 10 more homing endonucleases than vB_KpnM-VAC13, and that the nu cleotidic and amino-acid sequences of the L-shaped tail fiber protein were highly dissimilar, leading to different three-dimensional protein predictions. Both phages differed significantly in their host range. These viruses may be useful in the development of alternative therapies to antibiotics or as a co-therapy increasing its antimicrobial potential, especially when addressing multidrug resistant (MDR) pathogens. Instituto de Salud Carlos III: PI19/00878

Este trabajo estudia la amplificación del campo electromagnético que se produce sobre sustratos SERS (Surface Enhanced Raman Spectroscopy) basados en microestructuras piramidales recubiertas de metal (Au, Ag y Cu) al incidir en ellas un haz de luz monocromático, proceso conocido como efecto SERS. Este estudio se realizará utilizando el método computacional FDTD (Finite-Difference Time-Domain) y el software comercial Lumerical (Lumerical Solutions Inc. Ansys). Para ello se simulará una micro-pirámide de PMMA (polimetilmetacrilato) recubierta por un metal que se irá variando, al igual que se modificarán sus dimensiones: tamaño de base y grosor de la capa de metal. Finalmente se analizarán los resultados obtenidos para concluir qué material y que dimensiones proporcionan la máxima amplificación del campo electromagnético, y, por tanto, de la señal SERS.

Yeasts are responsible for several traits in fermented beverages, including wine and beer, and their genetic manipulation is often necessary to improve the quality of the fermentation product. Improvement of wild-type strains of Saccharomyces cerevisiae and Saccharomyces pastorianus is difficult due to their homothallic character and variable ploidy level. Homothallism is determined by the HO gene in S. cerevisiae and the Sc-HO gene in S. pastorianus. In this work, we describe the construction of an HO disruption vector (pDHO) containing an HO disruption cassette and discuss its use in generating heterothallic yeast strains from homothallic Saccharomyces species.