Bacteriemias por Escherichia coli: análisis clínico-epidemiológico, de factores de patogenicidad y mecanismos de resistencia a betalactámicos/inhibidores de betalactamasas

Las infecciones por bacterias multirresistentes son un serio problema a nivel mundial. La aparición constante de mecanismos de resistencia a los antibióticos junto con el limitado desarrollo de nuevos compuestos con actividad antibacteriana en los últimos años plantea la necesidad de abordar este problema de forma urgente. Esta Tesis Doctoral se ha centrado en el estudio de las infecciones por E. coli, en especial la bacteriemia y la infección intraabdominal, tanto desde el punto de vista del paciente como del microorganismo. Por un lado se analizaron las características clínicas y microbiológicas, así como factores de riesgo asociados con la mortalidad de los pacientes con bacteriemia por E. coli en comparación con pacientes con bacteriemia por K. pneumoniae. Este primer análisis mostró una serie de diferencias importantes entre uno y otro microorganismo. En la misma línea, se analizaron las características clínicas y microbiológicas de pacientes con infección intraabdominal por E. coli y su relación con la mortalidad, así como los factores de riesgo asociados al desarrollo de bacteriemia en este tipo de infección. Entre otros, la infección del tracto biliar parece jugar un papel importante, por lo que se decidió analizar la relación filogenética, el resistoma y el viruloma de un conjunto de aislados clínicos de E. coli causantes de infección biliar, con el objetivo de conocer si existen factores bacterianos que promuevan este tipo de infección. Aunque no existió relación filogenética entre los aislados, se encontraron numerosos factores de virulencia que podrían estar implicados en el desarrollo de infecciones del tracto biliar. Por otro lado, el siguiente objetivo fue estudiar la expresión de un factor de virulencia concreto como es la proteína de membrana externa A (OmpA) en E. coli, y su asociación con la mortalidad de los pacientes con bacteriemia por E. coli. Se analizó una amplia cohorte de aislados clínicos procedentes de pacientes con bacteriemia, en los que se determinó la expresión de OmpA y se encontró que la sobreexpresión de esta proteína es un factor de riesgo independiente para la mortalidad de los pacientes con bacteriemia por E. coli. Estos resultados sugieren que OmpA tiene un papel importante en la patogénesis de este microorganismo. Por último, y centrándonos en el tratamiento antibiótico de este tipo de infecciones, se estudió la existencia de un patrón de resistencia a los betalactámicos con inhibidores de betalactamasas (BL/IBL) en E. coli. Este patrón dio lugar a la descripción de un nuevo fenómeno denominado “resistencia de espectro extendido a los BL/IBL” o ESRI, el cual está favorecido por la presencia de concentraciones sub-óptimas de piperacilina/tazobactam, un antibiótico ampliamente utilizado para el tratamiento empírico de las infecciones graves por E. coli. Asimismo, y en relación con este objetivo, se llevó a cabo el diseño, desarrollo y validación de un sistema de detección rápida tanto de resistencia a piperacilina/tazobactam como de ESRI en E. coli. La descripción de este nuevo fenómeno de resistencia antibiótica, junto con la posibilidad de su detección anticipada, suponen una contribución innovadora a la par que prometedora en la lucha contra la resistencia a los antibióticos. En conjunto, los datos derivados de esta Tesis Doctoral dan cuenta de la importancia del abordaje multifocal de este tipo de infecciones, las cuales suponen un problema de gran magnitud, con elevados costes tanto para el paciente como para el sistema sanitario

De Pitágoras, habas y malaria

What does Pythagoras have to do with fava beans? And with malaria? Surely many of you are wondering this after reading the title. I’m going to tell you why and I hope not to disappoint you  ¿Qué tendrá que ver Pitágoras con las habas? ¿Y con la malaria? Seguramente muchos de vosotros os lo estaréis preguntando después de leer el título. Os voy a contar el porqué y espero no defraudaros

In vitro effect of ceftazidime-avibactam pressure on ceftazidime-avibactam resistance in KPC-producing Klebsiella pneumoniae clinical isolates.

Motivation: Infections caused by KPC-producing Klebsiella pneumoniae represent a challenge due to the limited available treatement choices. In this context, ceftazidime-avibactam (CAZ-AVI) is postulated as an alternative treatment effective against class A beta-lactamases such as KPC [1]. But, recent data reported the failure of CAZ-AVI treatment of infections by KPC-producing K. pneumoniae due to the development of CAZ-AVI resistance [2]. However, little is known concernig the CAZ-AVI resistance developement by CAZ-AVI selective pressure. Here, we aimed to determinate in vitro whether the exposure of KPC-producing K. pneumoniae clinical isolates to CAZ-AVI subinhibitory concentrations could lead the selection of CAZ-AVI resistant isolates. Methods: Seventeen KPC-producing K. pneumoniae clinical isolates (7 KPC-2, 9 KPC-3 and 1 KPC-11) were analyzed. Minimum inhibitory concentrations (MICs) of CAZ-AVI were determined by broth microdilution using a fixed AVI cocentration of 4 mg/L [3]. Moreover, these isolates were further exposed to increasing concentrations of CAZ and fixed 4 mg/L of AVI, from a sub-MIC up to 256/4 mg/L of CAZ-AVI (or the concentration able to kill the bacterial isolate) at 37ºC with shaking during 24h. New MICs to CAZ-AVI were determined in each condition and after 15 days without CAZ-AVI pressure. Therefore, in order to demonstrated that blaKPC gene is responsible for acquisition of CAZ-AVI resistance in KPC-producing K. pneumoniae, blaKPC-2 and blaKPC-3 were cloned into a reference K. pneumoniae CECT 997 strain. Resistance or susceptibility were determined according to EUCAST criteria [3]. Results: All (17/17, 100%) KPC-producing K. pneumoniae isolates were able to grow at high concentrations of CAZ-AVI (≥64/4 mg/L), increasing their resistance to CAZ-AVI ≥8-fold. Likewise, fifteen of the 17 (88.2%) resistant isolates maintained the acquired CAZ-AVI resistance 15 days after without CAZ-AVI pressure. In addition, the CECT 997 mutants with blaKPC-2 or blaKPC-3 were able to grow up to 256/4 mg/L of CAZ-AVI, displaying and maintaining CAZ-AVI MIC shift from <0.01/4 mg/L (susceptible) to 512/4 mg/L (resistant). Conclusions: These data suggest that exposure of KPC-producing K. pneumoniae to subinhibitory CAZ-AVI concentrations could lead to the selection of CAZ-AVI resistance and this resistance is stable over the time

Phylogeny, Resistome, and Virulome of Escherichia coli Causing Biliary Tract Infections

Escherichia coli is the most frequent Gram-negative bacilli involved in intra-abdominal infections. However, despite high mortality rates associated with biliary tract infections due to E. coli, there is no study focusing on this pathogen. In this study, we have characterized a group of 15 E. coli isolates obtained from 12 patients with biliary tract infections. Demographic and clinical data of the patients were recovered. Phylogeny, resistome, and virulome analysis through whole genome sequencing and biofilm formation were investigated. Among the 15 E. coli isolates, no predominant sequence type (ST) was identified, although 3 of them belonged to unknown STs (20%). Resistance to ampicillin, amoxicillin/clavulanic acid, cotrimoxazole, and quinolones was more present in these isolates; whereas, third and fourth generation cephalosporins, carbapenems, amikacin, tigecycline, and colistin were highly active. Moreover, high diversity of virulence factors has been found, with sfa, fimH, and gad the most frequently detected genes. Interestingly, 26.6% of the E. coli isolates were high biofilm-producers. Altogether, our data characterized for the first time E. coli isolates associated with biliary tract infections in terms of genomic relationship, resistome, and virulome.España, Instituto de Salud Carlos III, Subdirección General de Redes y Centros de Investigación Cooperativa, Ministerio de Ciencia, Innovación y Universidades (CP15/00132)España, Plan Nacional de I+D+i 2013-2016 and Instituto de Salud Carlos III, Subdirección General de Redes y Centros de Investigación Cooperativa, Ministerio de Ciencia, Innovación y Universidades, Spanish Network for Research in Infectious Diseases (RD16/0016/0009

Antibacterial activity of colloidal silver against Gram-negative and Gram-positive bacteria.

Motivation: Treatment of multidrug-resistant (MDR) bacteria represent a challenge for clinicians and public health authorities. Due to the emergence of resistance to a wide variety of antibiotics new alternative therapies are needed. Silver has been used to treat bacterial infections since antiquity due to its known antimicrobial properties [1]. The objective of this project was to study in vitro the activity of colloidal silver against Gram-negative and Gram-positive bacteria.Methods: Gram-negative bacteria [Acinetobacter baumannii (n=44), Pseudomonas aeruginosa (n=25) and Escherichia coli (n=79)] and Gram-positive bacteria [Staphylococcus aureus (n=34), Syaphylococcus epidermidis (n=14) and Enterococcus spp. (n=15)] were used. All strains were grown in a Mueller-Hinton Broth (MHB) at 37°C for 20-24 h. Minimal Inhibitory Concentration (MIC) was determined for all strains by using microdilution assay. To monitore the antibacterial activity, time-kill curve assays were performed on MHB at colloidal silver concentrations of 0.5x, 1x and 2x MIC with starting inoculum of 1x10^6 colony-forming units (cfu)/mL. Reactive Oxygen Species (ROS) production was measured at 6, 20 and 24 hours at colloidal silver concentrations of 0.25x, 0.5x and 1x MIC.Results:  Colloidal silver MIC range was from 4-8 mg/L for both Gram-negative and Gram-positive bacteria. Colloidal silver showed bactericidal activity against Gram-negative bacteria. However, it showed bacteriostatic activity against Gram-positive bacteria. For A. baumannii (Ab11 and ATCC 17978 strains), P. aeruginosa (Pa238 and Pa01 strains), and E. coli (mcr-1 positive strain) colloidal silver was bactericidal at 1x, and 2x MIC at 24h. However, at 24h, E. coli (ATCC 25922 strain) showed a regrowth at 0.5x, 1x and 2x MIC. Incubation of bacterial strains with colloidal silver led to a significant increase in ROS production at 24h in Gram-negative bacteria.Conclusions: Colloidal silver showed in vitro activity against these kind of pathogens, especially against Gram-negative bacteria. These results suggest that colloidal silver could be a new alternative for treatment of infections caused by MDR pathogens

Prevalence and Risk Factors for Multidrug-Resistant Organisms Colonization in Long-Term Care Facilities Around the World: A Review

Elderly people confined to chronic care facilities face an increased risk of acquiring infections by multidrug-resistant organisms (MDROs). This review presents the current knowledge of the prevalence and risk factors for colonization by MDROs in long-term care facilities (LTCF), thereby providing a useful reference to establish objectives for implementing successful antimicrobial stewardship programs (ASPs). We searched in PubMed and Scopus for studies examining the prevalence of MDROs and/or risk factors for the acquisition of MDROs in LTCF. One hundred and thirty-four studies published from 1987 to 2020 were included. The prevalence of MDROs in LTCF varies between the different continents, where Asia reported the highest prevalence of extended-spectrum ß-lactamase (ESBL) Enterobacterales (71.6%), carbapenem resistant (CR) Enterobacterales (6.9%) and methicillin-resistant Staphylococcus aureus (MRSA) (25.6%) and North America the highest prevalence to MDR Pseudomonas aeruginosa (5.4%), MDR Acinetobacter baumannii (15.0%), vancomycin-resistant Enterococcus spp. (VRE) (4.0%), and Clostridioides difficile (26.1%). Furthermore, MDRO prevalence has experienced changes over time, with increases in MDR P. aeruginosa and extended spectrum ß-lactamase producing Enterobacterales observed starting in 2015 and decreases of CR Enterobacterales, MDR A. baumannii, VRE, MRSA and C. difficile. Several risk factors have been found, such as male sex, chronic wounds, the use of medical devices, and previous antibiotic use. The last of these aspects represents one of the most important modifiable factors for reducing colonization with MDROs through implementing ASPs in LTCF.The study was funded by the Instituto de Salud Carlos III, the Spanish Ministry of Economy, Industry, and Competitiveness (grant number: PI17-02195) and was partially funded by the European Development Regional Fund “A way to achieve Europe”. A.R.V. and A.B.G.G. are supported by the Subprograma Río Hortega, Instituto de Salud Carlos III, Subdirección General de Redes y Centros de Investigación Cooperativa, Ministerio de Ciencia, Innovación y Universidades, Spain. A.R.V. grant number: CM18/00122. A.B.G.G. grant number: CM19/00029. C.M.G. and J.C.C.R. are supported by the Instituto de Salud Carlos III (grant number: PI17-02195) and co-financed by European Development Regional Fund ‘A way to achieve Europe’ ERDF, Spanish Network for the Research in Infectious Diseases (REIPI RD16/0016/0009).G.P. is supported by the Instituto de Salud Carlos III, Subdirección General de Redes y Centros de Investigación Cooperativa, Ministerio de Economía, Industria y Competitividad, Spanish Network for Research in Infectious Diseases (REIPI RD16/0016/0001)- co-financed by European Development Regional Fund “A way to achieve Europe”, Operative program Intelligent Growth 2014–2020. M.E.P.I. is a postdoctoral researcher belonging to the program “Nicolás Monardes” (C1-0038-2019), Servicio Andaluz de Salud, Junta de Andalucía, Spain. J.M.C. received funding for research from Plan Nacional de I+D+i 2013–2016 and Instituto de Salud Carlos III, Subdireccion General de Redes y Centros de InvestigacionCooperativa, Ministry of Economy, Industry and Competitiveness, Spanish Network for Research in Infectious Diseases (REIPI RD16/0016/0001, RD16/0016/0009), co-financed by the European Development Regional Fund “A way to achieve Europe”.Ye

Dendritic cell deficiencies persist seven months after SARS-CoV-2 infection

Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV)-2 infection induces an exacerbated inflammation driven by innate immunity components. Dendritic cells (DCs) play a key role in the defense against viral infections, for instance plasmacytoid DCs (pDCs), have the capacity to produce vast amounts of interferon-alpha (IFN-α). In COVID-19 there is a deficit in DC numbers and IFN-α production, which has been associated with disease severity. In this work, we described that in addition to the DC deficiency, several DC activation and homing markers were altered in acute COVID-19 patients, which were associated with multiple inflammatory markers. Remarkably, previously hospitalized and nonhospitalized patients remained with decreased numbers of CD1c+ myeloid DCs and pDCs seven months after SARS-CoV-2 infection. Moreover, the expression of DC markers such as CD86 and CD4 were only restored in previously nonhospitalized patients, while no restoration of integrin β7 and indoleamine 2,3-dyoxigenase (IDO) levels were observed. These findings contribute to a better understanding of the immunological sequelae of COVID-19

Clinical and Ecological Impact of an Educational Program to Optimize Antibiotic Treatments in Nursing Homes (PROA-SENIOR): A Cluster, Randomized, Controlled Trial and Interrupted Time-Series Analysis

[Background] Antimicrobial stewardship programs (ASPs) are recommended in nursing homes (NHs), although data are limited. We aimed to determine the clinical and ecological impact of an ASP for NHs.[Methods] We performed a cluster, randomized, controlled trial and a before–after study with interrupted time-series analyses in 14 NHs for 30 consecutive months from July 2018 to December 2020 in Andalusia, Spain. Seven facilities implemented an ASP with a bundle of 5 educational measures (general ASP) and 7 added 1-to-1 educational interviews (experimental ASP). The primary outcome was the overall use of antimicrobials, calculated monthly as defined daily doses (DDD) per 1000 resident days (DRD).[Results] The total mean antimicrobial consumption decreased by 31.2% (−16.72 DRD; P = .045) with respect to the preintervention period; the overall use of quinolones and amoxicillin–clavulanic acid dropped by 52.2% (P = .001) and 42.5% (P = .006), respectively; and the overall prevalence of multidrug-resistant organisms (MDROs) decreased from 24.7% to 17.4% (P = .012). During the intervention period, 12.5 educational interviews per doctor were performed in the experimental ASP group; no differences were found in the total mean antimicrobial use between groups (−14.62 DRD; P = .25). Two unexpected coronavirus disease 2019 waves affected the centers increasing the overall mean use of antimicrobials by 40% (51.56 DRD; P < .0001).[Conclusions] This study suggests that an ASP for NHs appears to be associated with a decrease in total consumption of antimicrobials and prevalence of MDROs. This trial did not find benefits associated with educational interviews, probably due to the coronavirus disease 2019 pandemic.[Clinical Trials Registration] NCT03543605.Peer reviewe

The first wave of the COVID-19 epidemic in Spain was associated with early introductions and fast spread of a dominating genetic variant

SeqCOVID-Spain consortium: Álvaro Chiner-Oms, Irving Cancino-Muñoz, Mariana G. López, Manuela Torres-Puente, Inmaculada Gómez-Navarro, Santiago Jiménez-Serrano, Jordi Pérez-Tur, Darío García de Viedma, Laura Pérez-Lago, Marta Herranz, Jon Sicilia, Pilar Catalán-Alonso, Julia Suárez González, Patricia Muñoz, Mireia Coscolla, Paula Ruiz-Rodríguez, Fernando González-Candelas, Iñaki Comas, Lidia Ruiz-Roldán, María Alma Bracho, Neris García-González, Llúcia Martínez Priego, Inmaculada Galán-Vendrell, Paula Ruiz-Hueso, Griselda De Marco, María Loreto Ferrús-Abad, Sandra Carbó-Ramírez, Giuseppe D’Auria, Galo Adrian Goig, Juan Alberola, Jose Miguel Nogueira, Juan José Camarena, David Navarro, Eliseo Albert, Ignacio Torres, Maitane Aranzamendi Zaldumbide, Óscar Martínez Expósito, Nerea Antona Urieta, María de Toro, María Pilar Bea-Escudero, Jose Antonio Boga, Cristian Castelló-Abietar, Susana Rojo-Alba, Marta Elena Álvarez-Argüelles, Santiago Melón, Elisa Martró, Antoni E. Bordoy, Anna Not, Adrián Antuori, Anabel Fernández-Navarro, Andrés Canut-Blasco, Silvia Hernáez Crespo, Maria Luz Cordón Rodríguez, Maria Concepción Lecaroz Agara, Carmen Gómez-González, Amaia Aguirre-Quiñonero, José Israel López-Mirones, Marina Fernández-Torres, Maria Rosario Almela-Ferrer, Ana Carvajal, Juan Miguel Fregeneda-Grandes, Héctor Argüello, Gustavo Cilla Eguiluz, Milagrosa Montes Ros, Luis Piñeiro Vázquez, Ane Sorarrain, José María Marimón, José J. Costa-Alcalde, Rocío Trastoy, Gema Barbeito Castiñeiras, Amparo Coira, María Luisa Pérez del Molino, Antonio Aguilera, Begoña Palop-Borrás, Inmaculada de Toro Peinado, Maria Concepción Mediavilla Gradolph, Mercedes Pérez-Ruiz, Mirian Fernández-Alonso, Jose Luis del Pozo, Oscar González-Recio, Mónica Gutiérrez-Rivas, Jovita Fernández-Pinero, Miguel Ángel Jiménez Clavero, Begoña Fuster Escrivá, Concepción Gimeno Cardona, María Dolores Ocete Mochón, Rafael Medina-Gonzalez, José Antonio Lepe, Verónica González Galán, Ángel Rodríguez-Villodres, Nieves Gonzalo Jiménez, Jordi Reina, Carla López-Causapé, Maria Dolores Gómez-Ruiz, Eva M. Gonzalez-Barbera, José Luis López-Hontangas, Vicente Martín, Antonio J. Molina, Tania Fernandez-Villa, Ana Milagro Beamonte, Nieves Felisa Martínez-Cameo, Yolanda Gracia-Grataloup, Rosario Moreno-Muñoz, Maria Dolores Tirado Balaguer, José María Navarro-Marí, Irene Pedrosa-Corral, Sara Sanbonmatsu-Gámez, Antonio Oliver, Mónica Parra Grande, Bárbara Gómez Alonso, Francisco José Arjona Zaragozí, Maria Carmen Pérez González, Francisco Javier Chamizo López, Ana Bordes-Benítez, Núria Rabella, Ferran Navarro, Elisenda Miró, Antonio Rezusta, Alexander Tristancho, Encarnación Simarro Córdoba, Julia Lozano-Serra, Lorena Robles Fonseca, Álex Soriano, Francisco Javier Roig Sena, Hermelinda Vanaclocha Luna, Isabel Sanmartín, Daniel García-Souto, Ana Pequeño-Valtierra, Jose M. C. Tubio, Javier Temes, Jorge Rodríguez-Castro, Martín Santamarina García, Manuel Rodríguez-Iglesias, Fátima Galán-Sanchez, Salud Rodríguez-Pallares, José Manuel Azcona-Gutiérrez, Miriam Blasco-Alberdi, Alfredo Mayor, Alberto L. García-Basteiro, Gemma Moncunill, Carlota Dobaño, Pau Cisteró, Oriol Mitjà, Camila González-Beiras, Martí Vall-Mayans, Marc Corbacho-Monné, Andrea Alemany, Cristina Muñoz-Cuevas, Guadalupe Rodríguez-Rodríguez, Rafael Benito, Sonia Algarate, Jessica Bueno, Andrea Vergara-Gómez, Miguel J. Martínez, Jordi Vila, Elisa Rubio, Aida Peiró-Mestres, Jessica Navero-Castillejos, David Posada, Diana Valverde, Nuria Estévez, Iria Fernández-Silva, Loretta de Chiara, Pilar Gallego-García, Nair Varela, Ulises Gómez-Pinedo, Mónica Gozalo-Margüello, Maria Eliecer Cano García, José Manuel Méndez-Legaza, Jesus Rodríguez-Lozano, María Siller, Daniel Pablo-Marcos, Maria Montserrat Ruiz-García, Antonio Galiana, Judith Sánchez-Almendro, Maria Isabel Gascón Ros, Cristina Juana Torregrosa-Hetland, Eva María Pastor Boix, Paloma Cascales Ramos, Pedro Luis Garcinuño Enríquez, Salvador Raga Borja, Julia González Cantó, Olalla Martínez Macias, Adolfo de Salazar, Laura Viñuela González, Natalia Chueca, Federico García, Cristina Gómez-Camarasa, Amparo Farga Martí, Rocío Falcón, Victoria Domínguez-Márquez, Anna M. Planas, Israel Fernández-Cádenas, Maria Ángeles Marcos, Carmen Ezpeleta, Ana Navascués, Ana Miqueleiz Zapatero, Manuel Segovia, Antonio Moreno-Docón, Esther Viedma, Raúl Recio Martínez, Irene Muñoz-Gallego, Sara Gonzalez-Bodi, Maria Dolores Folgueira, Jesús Mingorance, Elias Dahdouh, Fernando Lázaro-Perona, María Rodríguez-Tejedor, María Pilar Romero-Gómez, Julio García-Rodríguez, Juan Carlos Galán, Mario Rodríguez-Dominguez, Laura Martínez-García, Melanie Abreu Di Berardino, Manuel Ponce-Alonso, Jose Maria González-Alba, Ivan Sanz-Muñoz, Diana Pérez San José, Maria Gil Fortuño, Juan B. Bellido-Blasco, Alberto Yagüe Muñoz, Noelia Hernández Pérez, Helena Buj Jordá, Óscar Pérez Olaso, Alejandro González Praetorius, Nora Mariela Martínez Ramírez, Aida Ramírez Marinero, Eduardo Padilla León, Alba Vilas Basil, Mireia Canal Aranda, Albert Bernet Sánchez, Alba Bellés Bellés, Eric López González, Iván Prats Sánchez, Mercè García-González, Miguel José Martínez-Lirola, Manuel Ángel Rodríguez Maresca, Maria Teresa Cabezas Fernández, María Eugenia Carrillo Gil, Maria Paz Ventero Martín, Carmen Molina Pardines, Nieves Orta Mira, María Navarro Cots, Inmaculada Vidal Catalá, Isabel García Nava, Soledad Illescas Fernández-Bermejo, José Martínez-Alarcón, Marta Torres-Narbona, Cristina Colmenarejo, Lidia García-Agudo, Jorge A. Pérez García, Martín Yago López, María Ángeles Goberna Bravo, Victoria Simón García, Gonzalo Llop Furquet, Agustín Iranzo Tatay, Sandra Moreno-Marro, Noelia Lozano Rodríguez, Amparo Broseta Tamarit, Juan José Badiola Díez, Amparo Martínez-Ramírez, Ana Dopazo, Sergio Callejas, Alberto Benguría, Begoña Aguado, Antonio Alcamí, Marta Bermejo Bermejo, Ricardo Ramos-Ruíz, Víctor Manuel Fernández Soria, Fernando Simón Soria & Mercedes Roig CardellsThe coronavirus disease 2019 (COVID-19) pandemic has affected the world radically since 2020. Spain was one of the European countries with the highest incidence during the first wave. As a part of a consortium to monitor and study the evolution of the epidemic, we sequenced 2,170 samples, diagnosed mostly before lockdown measures. Here, we identified at least 500 introductions from multiple international sources and documented the early rise of two dominant Spanish epidemic clades (SECs), probably amplified by superspreading events. Both SECs were related closely to the initial Asian variants of SARS-CoV-2 and spread widely across Spain. We inferred a substantial reduction in the effective reproductive number of both SECs due to public-health interventions (Re < 1), also reflected in the replacement of SECs by a new variant over the summer of 2020. In summary, we reveal a notable difference in the initial genetic makeup of SARS-CoV-2 in Spain compared with other European countries and show evidence to support the effectiveness of lockdown measures in controlling virus spread, even for the most successful genetic variants.This work was mainly funded by the Instituto de Salud Carlos III project COV20/00140, with additional funding by Spanish National Research Council project CSIC-COV19-021, Ministerio de Ciencia project PID2019-104477RB-100, ERC StG 638553 and ERC CoG 101001038 to I.C., and BFU2017-89594R to F.G.C. M.C. is supported by Ramón y Cajal program from Ministerio de Ciencia and grants RTI2018-094399-A-I00 and Generalitat Valenciana (Regional Government) project SEJI/2019/011. We gratefully acknowledge Hospital Universitari Vall d’Hebron, Instituto de Salud Carlos III, IrsiCaixa AIDS Research Lab and all the international researchers and institutions that submitted sequenced SARS-CoV-2 genomes to the GISAID’s EpiCov Database (Supplementary Table 1), as an important part of our analyses has been made possible by the sharing of their work. We also thank Unidad de Bioinformática y Estadística, Centro de Investigación Príncipe Felipe, for allowing us to use the Computer Cluster to perform some of the bioinformatic analysis.Peer reviewe

A selective culture medium for screening linezolid-resistant gram-positive bacteria

The SuperLinezolid medium was developed for screening resistance to linezolid (LZD) in Gram-positive bacteria (Staphylococcus spp., Enterococcus spp.). It was evaluated using LZD-susceptible (n = 20) and LZD-resistant (n = 17) Gram-positive isolates. The sensitivity was found to be 82% at 24 h (3 out of 17 isolates being missed), and reached 100% at 48 h. At 48 h, a single LZD-susceptible isolate grew (specificity 95%). By testing stools spiked with LZD-resistant Gram-positive strains, an excellent performance of the medium was observed, with a lowest detection limit ranging from 101 to 102 CFU/ml. Overall, this medium is accurate for detection of LZD-resistant Gram-positive isolates after 24 h of culture.This work was financed by the University of Fribourg, Switzerland. It has also been funded by the Swiss National Science Foundation (project FNS-407240_177382). A.R.-V. was partly financed by a grant from the Spanish Society of Infectious Diseases and Clinical Microbiology (SEIMC)