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

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

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

Oligodendrocyte metabolism throughout its differentiation: immunocytochemistry study and its impact in remyelination

Introduction: Oligodendrocytes (OL) role in demyelinating pathologies such as multiple sclerosis and other neurodegenerative diseases is only recently being subject of extensive research. While the genetic and molecular aspects have been thoroughly studied, their metabolism was overshadowed. In order to develop new therapies to promote remyelination of already damaged axons, we need to accurately describe how OL metabolism affects axon myelination and trophic support (1). The objective of this study is to obtain cytological evidence of the extent of both glycolytic metabolism and oxidative phosphorylation by immunocytochemistry throughout the development of OL. Methods: Oligodendroglia cells from post-natal mice cortices were obtained and cultured. A wide assortment of differentiation-stage-specific cell surface antigens, a glycolytic and an oxidative phosphorylation marker were combined in several immunofluorescences to study both metabolic pathways in each step of differentiation. Results: After analysing them under confocal microscopy and imaging software, we observed a constant upregulation of glycolytic metabolism throughout differentiation, while oxidative phosphorylation seemed to increase with differentiation to then decrease when oligodendrocytes achieved their final maturation stage. Conclusions: Therefore, oxidative phosphorylation may be crucial in the differentiation of precursors and glycolysis would thus be the preferred metabolic pathway for fully matured OL. [1] Rosko L. et al. Neuroscientist. 2019;25(4):334–43.Supported by UMA and IBIMA and funding from two ongoing projects: - ‘Modulation of oligodendrocyte metabolism via blood vessel remodelling as target to promote remyelination’ (funding by NEURATRIS). - ‘Blood vessel remodelling modulates remyelination by oligodendrocyte metabolic reprogramming’ (funding by Arsep Foundation). Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

BIChromET: A Chromogenic Culture Medium for Detection of Piperacillin/Tazobactam and Cefepime Resistance in Pseudomonas aeruginosa

Objectives: The BIChromET selective medium for detecting piperacillin-tazobactam (TZP) and cefepime (FEP) resistant Pseudomonas aeruginosa was developed. Methods: The performance of this medium was first evaluated using a collection of 100 P. aeruginosa clinical strains (70 TZP-susceptible, 30 TZP-resistant, 58 FEP-susceptible, and 42 FEP-resistant). Then, we performed clinical validation by testing 173 respiratory clinical samples. Results: The BIChromET medium showed excellent sensitivity (TZP (avg. 96.7%); FEP (avg. 92.7%)) and specificity (TZP (avg. 98.9%); FEP (avg. 98%)) in distinguishing the detection limit ranging from 104 to 108 CFU/mL. Then, testing the bronchoalveolar lavage (BAL) and tracheobronchial aspirate (TBA) clinical specimens (N = 173) revealed the excellent performance of the medium with P. aeruginosa, showing 100% and 92.6% of categorical agreements with the results obtained via the broth microdilution methods (BMD) for TZP and FEP, respectively. Conclusion: This medium allows for easy and accurate detection of TZP/FEP-resistant isolates regardless of their resistance mechanisms

Microbiome alterations and Alzheimer's Disease: modeling strategies with transgenic mice.

In the last decade, the role of the microbiota-gut-brain axis has been gaining momentum in the context of many neurodegenerative and metabolic disorders, including Alzheimer's disease (AD) and diabetes, respectively. Notably, a balanced gut microbiota contributes to the epithelial intestinal barrier maintenance, modulates the host immune system, and releases neurotransmitters and/or neuroprotective short-chain fatty acids. However, dysbiosis may provoke immune dysregulation, impacting neuroinflammation through peripheral-central immune communication. Moreover, lipopolysaccharide or detrimental microbial end-products can cross the blood-brain barrier and induce or at least potentiate the neuropathological progression of AD. Thus, after repeated failure to find a cure for this dementia, a necessary paradigmatic shift towards considering AD as a systemic disorder has occurred. Here, we present an overview of the use of germ-free and/or transgenic animal models as valid tools to unravel the connection between dysbiosis, metabolic diseases, and AD, and to investigate novel therapeutical targets. Given the high impact of dietary habits, not only on the microbiota but also on other well-established AD risk factors such as diabetes or obesity, consistent changes of lifestyle along with microbiome-based therapies should be considered as complementary approaches.Partial funding for open access charge: Universidad de Málaga/CBU

Role of blaTEM and OmpC in the piperacillin-tazobactam resistance evolution by E. coli in patients with complicated intra-abdominal infection

Piperacillin-tazobactam resistance (P/T-R) is increasingly reported among Escherichia coli isolates. Although in vitro experiments have suggested that bla gene plays a key role in the P/T-R acquisition, no clinical in vivo study has yet confirmed the role of bla or other genes. Therefore, we aimed to identify the mechanisms underlying P/T-R by following up patients with E. coli complicated intra-abdominal infections (cIAI) who experienced P/T treatment failure. Four pairs of strains, clonally related from four patients, were isolated both before and after treatment with P/T dosed at 4 g/0.5 g intravenously. The P/T MIC was tested using broth microdilution, and β-lactamase activity was determined in these isolates. Whole-genome sequencing (WGS) was performed to decipher the role of bla and other genes associated with P/T-R. Changes in the outer membrane protein (OMP) profile were analyzed using SDS-PAGE, and bla and ompC transcription levels were measured by RT-qPCR. In addition, in vitro competition fitness was performed between each pairs of strains (P/T-susceptible vs. P/T-resistant). We found a higher copy number of bla gene in P/T-R isolates, generated by three different genetic events: (1) IS26-mediated duplication of the bla gene, (2) generation of a small multicopy plasmid (ColE-like) carrying bla, and (3) adaptive evolution via reduction of plasmid size, leading to a higher plasmid copy number. Moreover, two P/T-R strains showed reduced expression of OmpC. This study describes the mechanisms involved in the acquisition of P/T-R by E. coli in patients with cIAI. The understanding of P/T-R evolution is crucial for effectively treating infected patients and preventing the spread of resistant microorganisms.This work was funded by the Instituto de Salud Carlos III, Subdirección General de Redes y Centros de Investigación Cooperativa, Ministerio de Economía, Industria y Competitividad (grant PI19/01009), by Plan Nacional de I+D+i 2013–2016, and 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 (grant RD16/0016/0009), cofinanced by the European Development Regional Fund “A way to make Europe”/”Investing in your future”. A.R.V, R.A-M, J.A.L. and J.M.C. were supported (grant CB21/13/00006) by CIBERINFEC - Consorcio Centro de Investigación Biomédica en Red, Instituto de Salud Carlos III, Ministerio de Ciencia e Innovación and Unión Europea – NextGenerationEU. L.G.B. was partly financed by a grant from the Spanish Society of Infectious Diseases and Clinical Microbiology (SEIMC) and is supported by the Subprograma Rio Hortega, Instituto Carlos III, Subdirección General de Redes y Centros de Investigación Cooperativa, Ministerio de Ciencia, Innovación y Universidades, Spain (CM22/00196). J.M.O.R. is supported by the Subprograma Sara Borrell, Instituto de Salud Carlos III, Subdirección General de Redes y Centros de Investigación Cooperativa, Ministerio de Ciencia, Innovación y Universidades, Spain (CD21/00098). A.R.V. is supported by the Subprograma Juan Rodés, Instituto de Salud Carlos III, Subdirección General de Redes y Centros de Investigación Cooperativa, Ministerio de Ciencia, Innovación y Universidades, Spain (JR20/00023), and Y.S. has received a Miguel Servet Tipo II contract from the Instituto de Salud Carlos III, Subdirección General de Redes y Centros de Investigación Cooperativa, Ministerio de Economía y Competitividad, Spain (grant CPII20/00018). Funding for open access publishing: Universidad Pablo de OlavidePeer reviewe