Artículos (Microbiología)

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Selection and Characterisation of Elite Mesorhizobium spp. Strains That Mitigate the Impact of Drought Stress on Chickpea
(Multidisciplinary Digital Publishing Institute (MDPI), 2025-08-05) Camacho, María; Vaccano, Francesca; Brun, Pilar; Ollero Márquez, Francisco Javier; Pérez Montaño, Francisco de Asís; Negussu, Miriam; Fagorzi, Camilla; Microbiología; European Union (UE)
The chickpea (Cicer arietinum L.) is a key legume crop in Mediterranean agriculture, valued for its nutritional profile and adaptability. However, its productivity is severely impacted by drought stress. To identify microbial solutions that enhance drought resilience, we isolated seven Mesorhizobium strains from chickpea nodules collected in southern Spain and evaluated their cultivar-specific symbiotic performance. Two commercial cultivars (Pedrosillano and Blanco Lechoso) and twenty chickpea germplasms were tested under growth chamber and greenhouse conditions, both with and without drought stress. Initial screening in a sterile substrate using nodulation assays, shoot/root dry weight measurements, and acetylene reduction assays identified three elite strains (ISC11, ISC15, and ISC25) with superior symbiotic performance and nitrogenase activity. Greenhouse trials under reduced irrigation demonstrated that several strain–cultivar combinations significantly mitigated drought effects on plant biomass, with specific interactions (e.g., ISC25 with RR-98 or BT6-19) preserving over 70% of shoot biomass relative to controls. Wholegenome sequencing of the elite strains revealed diverse taxonomic affiliations—ISC11 as Mesorhizobium ciceri, ISC15 as Mesorhizobium mediterraneum, and ISC25 likely representing a novel species. Genome mining identified plant growth-promoting traits including ACC deaminase genes (in ISC11 and ISC25) and genes coding for auxin biosynthesis-related enzymes. Our findings highlight the potential of targeted rhizobial inoculants tailored to chickpea cultivars to improve crop performance under water-limiting conditions.
Combined inactivation of the SOS response with TCA fumarases and the adaptive response enhances antibiotic susceptibility against Escherichia coli
(Frontiers, 2025-05-09) Murillo Torres, Marina; Peñalver-Fernández, Isabel María; Quero-Delgado, Marta; Diaz-Diaz, Sara; Romero-Muñoz, María; Docobo Pérez, Fernando; Rodríguez Martínez, José Manuel; Microbiología; Instituto de Salud Carlos III
Emergence of KPC-8-producing K. pneumoniae infection without prior exposure to ceftazidime/avibactam: the threat of de novo infections by ceftazidime/avibactam-resistant KPC variants
(American Society for Microbiology (ASM) journals, 2025-04-22) Mateo-Vargas, María Alejandra; Rodríguez-Pallares, Salud; Arca-Suárez, Jorge; López Cerero, Lorena; Rodríguez-Iglesias, Manuel; Galán-Sánchez, Fátima; Microbiología; Instituto de Salud Carlos III; Xunta de Galicia; Centro de Investigación Biotecnológica en Red de Enfermedades Infecciosas (CIBERINFEC)
De novo infections caused by ceftazidime/avibactam-resistant KPC variants are rarely reported. We characterize the evolution of a KPC-8-producing Klebsiella pneumoniae strain involved in a primary infection without previous ceftazidime/avibactam treatment. During a 15-month follow-up, changes in carbapenem susceptibility due to porin alterations were observed, remaining susceptible to meropenem/vaborbactam, imipenem/relebactam, and cefiderocol. High- and low-permeability recombinant Escherichia coli isolates analysis revealed that, unlike the widespread ceftazidime/avibactam-resistant variant KPC-31, KPC-8 confers ceftazidime/avibactam resistance without decreasing carbapenemase activity.
Quantitative study of ESBL and carbapenemase producers in wastewater treatment plants in Seville, Spain: a culture-based detection analysis of raw and treated water
(Elsevier, 2025) Monge-Olivares, Laura; Peñalva, Germán; Pulido, Marina R.; Garrudo, Lara; Doval, Miguel Ángel; Ballesta, Sofía; López Cerero, Lorena; Microbiología; Junta de Andalucía; MicroCarbaFlux
Antibiotics can modify populations of multidrug-resistant microorganism (MDRO) in urban wastewater. Our objectives were to quantify the differences in MDR Gram-negative bacteria between influents and effluents of WWTPs of a Spanish city and to evaluate the influence of human antibiotic prescriptions, as well as the persistence of these bacteria after treatment and their genetic relatedness to clinical isolates. The mean count of ESBL producers and carbapenemase producers were 3.77 and 2.74 log 10 CFU/ml, respectively. The reduction achieved by water treatment of ESBL-producing organisms was 1.4-log (96.11 %), whereas a 1.8-log reduction (98.36 %) was obtained regarding carbapenemase producing organisms. Aeromonas spp. predominated among MDROs and blaKPC-2 was the main carbapenemase detected in the influent wastewater samples. Among Escherichia coli and Klebsiella pneumoniae influent isolates, 44 % and 30 %, respectively, belonged to high-risk clones. Regarding Enterobacteriaceae, 10.6 % matched clinical isolates and one strain from an ongoing hospital outbreak was identified among raw samples. New MDROs and persistence of certain strains were detected in effluent samples. Quinolone and third-generation cephalosporin prescriptions, flow rate and population density were associated with higher OXA-48 producer counts. Despite reductions, additional technologies should be implemented in WWTPs receiving hospital discharges. Given the prevalence of environmental species, culture-based and metagenomic approaches should be combined to distinguish between human and sewage sources for antibiotic resistance monitoring. Overall, this study shows that WWTPs with secondary treatment are effective at removing MDRO, and antibiotic stewardship is a potential strategy to reduce the release of MDROs.
Wax synthases from sunflower (Helianthus annuus) seeds
(Elsevier, 2025) Andrés Gil, Cristina de; Villoslada-Balbuena, Mónica; Venegas Calerón, Mónica; Moreno Pérez, Antonio Javier; Beaudoin, Federic; Kurup, Smita; Liñán Salas, Joaquín J.; Microbiología; Ministerio de Ciencia e Innovación (MICIN). España; Consejo Superior de Investigaciones Científicas (CSIC)
Wax esters (WEs) are aliphatic esters of very-long-chain fatty acids and fatty alcohols that contribute to the lipid coatings of many plant organs. In the case of sunflower seeds, these compounds accumulate especially in the seed hull and are synthesized by the action of wax synthase (WS) enzymes through the esterification of acyl-CoA derivatives with very-long-chain fatty alcohols produced by fatty acyl reductases. Here, genes encoding 15 WSs were identified in the sunflower genome, of which 3 are expressed appreciably in the seed during the period of WE accumulation: HaWS6, HaWS8, and HaWS11. The localization and structure of these WSs were studied, and they were expressed in yeast in order to assay the microsome fractions prepared from them. The HaWSs all had very broad specificity profiles for alcohols and they were able to esterify short-chain alcohols (<10 C) with the acyl-CoA supplied. Indeed, simultaneous expression of HaWS8 and HaFAR5 resulted in the production in yeast of some WEs typically present in the sunflower hull.
Characterization of a blaKPC-3-carrying plasmid in a clinical isolate of Klebsiella pneumoniae belonging to the emerging successful clone ST147
(American Society for Microbiology (ASM) journals, 2025-05-23) Recacha, Esther; Delgado Valverde, María Mercedes; Pulido, Marina R.; Pérez-Nadales, Elena; Pérez-Palacios, Patricia; Gracia-Ahufinger, Irene; Pascual Hernández, Álvaro; Microbiología; Junta de Andalucía; European Union (UE); Instituto de Salud Carlos III
Klebsiella pneumoniae ST147 has emerged as a successful clone able to efficiently disseminate a number of carbapenemases, including blaKPC. This study compared a representative blaKPC-3-carrying plasmid of an ST147 clone with plasmids that usually harbor blaKPC-3 belonging to the high-risk clone ST512. Five clinical isolates of KPC-3-producing K. pneumoniae belonging to ST147 isolated in Southern Spain were analyzed. The first ST147 isolate detected was compared with two previous isolates of K. pneumoniae ST512/KPC-3 and KPC-3-encoding plasmid pKpQIL as reference plasmid. Microdilution, disk diffusion, β-CARBA test, and NG-Test CARBA 5 were used for antimicrobial susceptibility analysis and phenotypic characterization of the isolates according to EUCAST guidelines. Molecular characterization was performed using pulsed-field gel electrophoresis (PFGE)-XbaI, sequenced (by Illumina and Oxford Nanopore) and annotated with open-source databases (CGE tools and RAST). Plasmid incompatibility groups were analyzed using PlasmidFinder; BRIG was used to compare the blaKPC-3-harboring plasmids from three of the selected clinical isolates with each other and with pKpQIL. Clinical isolates of ST147/KPC-3 showed resistance to β-lactams, fluoroquinolones, and aminoglycosides. Clinical isolates ST147/KPC-3 and ST512/KPC-3 had identical PFGE patterns in each clone. Plasmid replicon analysis showed a plasmid with the formula IncFII (K2:A-:B-) in the ST512 isolates, identical to pKpQIL; the ST147 isolates harbored IncFII (K1:A-:B-), although the genetic environment of blaKPC-3 was the same as pKpQIL, which is Tn4401_ISKpn7 upstream of blaKPC-3 and ISKpn6 downstream of blaKPC-3. Plasmids harboring blaKPC-3 in ST147 and ST512 are different, although differences are subtle. The genetic environment of blaKPC-3 in the different sequence types is very conservative and identical to pKpQIL.
The Pseudomonas putida type VI secretion systems shape the tomato rhizosphere microbiota
(Oxford University Press, 2025) Vázquez-Arias, David; Civantos Jiménez, Cristina; Durán-Wendt, David; Ruiz Camas, Adrián; Rivilla, Rafael; Martín, Marta; Bernal Guzmán, Patricia; Microbiología; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; Ministerio de Ciencia e Innovación (MICIN). España; European Union (UE)
Bacterial competition mechanisms drive microbial community dynamics across diverse ecological niches. The type VI secretion system (T6SS) represents a sophisticated nanomachine used by Gram-negative bacteria for contact-dependent elimination of competitors through the delivery of toxic effectors. While the T6SS has been well-documented in mammalian gut microbiota development, its role in shaping plant rhizosphere communities remains poorly understood despite the ecological importance of rhizosphere microbiota. This study investigates how the three Pseudomonas putida KT2440 T6SS clusters influence the tomato rhizosphere microbiota in agricultural soil. Through comprehensive in vitro and in vivo analyses, we demonstrate that while the K2/K3-T6SSs remain inactive under standard laboratory conditions, they become specifically functional in the presence of plant pathogens, suggesting an adaptive response to competitive pressure. Our experiments with T6SS-deficient mutants reveal that the P. putida T6SSs are important for effective rhizosphere colonization, with mutant strains showing significantly reduced colonization capabilities compared to wildtype strain in competitive soil environments. Most importantly, our data establish that the P. putida T6SSs directly shape the taxonomic diversity and community structure of the rhizosphere microbiota of tomato plants. These results place the T6SS as a critical factor driving the evolution of complex polymicrobial communities within the plant rhizosphere, paralleling its established role in the gut microbiota. This research advances our understanding of the ecological functions of the different T6SSs in P. putida and the molecular mechanisms underlying microbial community assembly in the rhizosphere. Thus, it offers valuable insights for agricultural applications involving beneficial microbes and plant health management strategies.
Establishment of an induced memory response in Pseudomonas aeruginosa during infection of a eukaryotic host
(Oxford University Press, 2019-04-05) Kordes, A.; Grahl, N.; Koska, M.; Preusse, M.; Arce Rodríguez, Alejandro; Abraham, W. R.; Häussler, S.; European Union (UE)
In a given habitat, bacterial cells often experience recurrent exposures to the same environmental stimulus. The ability to memorize the past event and to adjust current behaviors can lead to efficient adaptation to the recurring stimulus. Here we demonstrate that the versatile bacterium Pseudomonas aeruginosa adopts a virulence phenotype after serial passage in the invertebrate model host Galleria mellonella. The virulence phenotype was not linked to the acquisition of genetic variations and was sustained for several generations, despite cultivation of the ex vivo virulence-adapted P. aeruginosa cells under rich medium conditions in vitro. Transcriptional reprogramming seemed to be induced by a host-specific food source, as reprogramming was also observed upon cultivation of P. aeruginosa in rich medium supplemented with polyunsaturated long-chain fatty acids. The establishment of induced memory responses adds a time dimension and seems to fill the gap between long-term evolutionary genotypic adaptation and short-term induced individual responses. Efforts to unravel the fundamental mechanisms that underlie the carry-over effect to induce such memory responses will continue to be of importance as hysteretic behavior can serve survival of bacterial populations in changing and challenging habitats.
CNGC15 and DMI1 ion channel gating in nuclear calcium signaling: opening new questions and closing controversies
(Oxford university Press, 2024-12-04) Jacott, Catherine N.; Cerro Sánchez, Pablo del; Microbiología; Ramón y Cajal; Juan de la Cierva
Nuclear calcium (Ca2+) signaling is crucial for symbiotic interactions between legumes and beneficial microbes, such as rhizobia and arbuscular mycorrhizal fungi. The ion channels DMI1 and CNGC15 are key to generating repetitive nuclear Ca2+ oscillations. Despite more than 20 years of research on symbiotic nuclear Ca2+ spiking, important questions remain, including the exact function of the DMI1 channel. This review highlights recent developments that have filled knowledge gaps regarding the regulation of CNGC15 and its interplay with DMI1. We also explore new insights into the evolutionary conservation of DMI1-induced symbiotic nuclear Ca2+ oscillations and the roles of CNGC15 and DMI1 beyond symbiosis, such as in nitrate signaling, and discuss new questions this raises. As we delve deeper into the regulatory mechanisms and evolutionary history of these ion channels, we move closer to fully understanding the roles of nuclear Ca2+ signaling in plant life.
Clinical presentation, microbiology, and prognostic factors of prosthetic valve endocarditis. Lessons learned from a large prospective registry
(Public Library of Science, 2023-09-08) Ramos Martínez, Antonio; Domínguez, Fernando; Muñoz, Patricia; Marín, Mercedes; Pedraz, Álvaro; Fariñas, Mª Carmen; GAMES investigators; Cueto López, Marina de; Lepe Jiménez, José Antonio; Araji Tiliani, Omar; Cirugía; Microbiología; CTS204: Biotecnología Aplicada al Estudio de Enfermedades Infecciosas
Background: Prosthetic valve endocarditis (PVE) is a serious infection associated with high mortality that often requires surgical treatment. Methods: Study on clinical characteristics and prognosis of a large contemporary prospective cohort of prosthetic valve endocarditis (PVE) that included patients diagnosed between January 2008 and December 2020. Univariate and multivariate analysis of factors associated with in-hospital mortality was performed. Results: The study included 1354 cases of PVE. The median age was 71 years with an interquartile range of 62–77 years and 66.9% of the cases were male. Patients diagnosed during the first year after valve implantation (early onset) were characterized by a higher proportion of cases due to coagulase-negative staphylococci and Candida and more perivalvular complications than patients detected after the first year (late onset). In-hospital mortality of PVE in this series was 32.6%; specifically, it was 35.4% in the period 2008–2013 and 29.9% in 2014–2020 (p = 0.031). Variables associated with in-hospital mortality were: Age-adjusted Charlson comorbidity index (OR: 1.15, 95% CI: 1.08–1.23), intracardiac abscess (OR:1.78, 95% CI:1.30–2.44), acute heart failure related to PVE (OR: 3. 11, 95% CI: 2.31–4.19), acute renal failure (OR: 3.11, 95% CI:1.14–2.09), septic shock (OR: 5.56, 95% CI:3.55–8.71), persistent bacteremia (OR: 1.85, 95% CI: 1.21–2.83) and surgery indicated but not performed (OR: 2.08, 95% CI: 1.49–2.89). In-hospital mortality in patients with surgical indication according to guidelines was 31.3% in operated patients and 51.3% in non-operated patients (p<0.001). In the latter group, there were more cases of advanced age, comorbidity, hospital acquired PVE, PVE due to Staphylococcus aureus, septic shock, and stroke. Conclusions: Not performing cardiac surgery in patients with PVE and surgical indication, according to guidelines, has a significant negative effect on in-hospital mortality. Strategies to better discriminate patients who can benefit most from surgery would be desirable.
Efficacy of the CHRONOlight biodynamic lighting system for control of nosocomial Gram-negative pathogens
(Elsevier, 2025) Pérez Palacios, Patricia; Bustamante, Pedro; Domínguez Amarillo, Samuel; Caro Ayora, María José; Acosta García, Ignacio Javier; Rodríguez Martínez, José Manuel; Construcciones Arquitectónicas I; Microbiología
Objectives Health care–associated infections are a growing public health concern, with hospitals acting as reservoirs for pathogens. The rise in antimicrobial resistance worsens the issue. This study tested the effectiveness of the biodynamic lighting system (CHRONOlight) at varying ultraviolet (UV) light times and energy levels to reduce nosocomial gram-negative pathogens. Methods Eight clinical isolates, representing different gram-negative pathogens, were selected from the Andalusian reference laboratory. Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter baumannii ATCC were used as control strains. Different inoculums were exposed to type C UV light (UV-C) doses 2.0, 1.5, and 1.0 W/m2 (corresponding to an irradiation flux of 100%, 75%, and 50%, respectively, with spectral peaks at 270 nm) during 15, 30, 45, 60, and 300 seconds and type A UV light (UV-A) (380 nm) during 30 minutes. The bactericidal effect was considered when cellular viability decreased by ≥3-log10 colony forming unit/ml. UV-C light-surviving isolates were sequenced (Illumina MiSeq) and analyzed to identify mutations associated with UV-C light survival. The development of antibiotic resistance after UV-C exposure were also studied for the same surviving isolates. Results The efficacy of the CHRONOlight biodynamic lighting system varied by exposure time, UV dose, and bacterial species. E. coli isolates showed bactericidal effects within 15-30 seconds at 100% UV-C intensity, whereas Klebsiella pneumoniae required 30-45 seconds. P. aeruginosa and A. baumannii showed activity in 15-30 seconds, but clinical A. baumannii needed longer exposure, especially at lower UV-C intensities. No reduction in cell viability was seen with UV-A exposure. Gene mutations related to metabolism, stress response, motility, and virulence were found in survivors, and no cross-antibiotic resistance developed in surviving isolates. Conclusions CHRONOlight biodynamic lighting system is a novel broad-spectrum lighting prototype designed to effectively reduce the viability of gram-negative bacteria within short exposure times (30-300 seconds) through UV-C emission. This makes it a promising strategy for minimizing nosocomial infections in health care settings.
Updated Sequence and Annotation of the Broad Host Range Rhizobial Symbiont Sinorhizobium fredii HH103 Genome
(Multidisciplinary Digital Publishing Institute (MDPI), 2025-09-16) Fuentes Romero, Francisco; López Baena, Francisco Javier; Vinardell González, José María; Acosta Jurado, Sebastián; Microbiología; Universidad de Sevilla; Ministerio de Ciencia e Innovación (MICIN). España
Background: Sinorhizobium fredii HH103 is a fast-growing rhizobial strain capable of infecting a broad range of legumes, including plants forming determinate and indeterminate nodules, such as Glycine max (its natural host) and Glycyrrhiza uralensis, respectively. Previous studies reported the sequence and annotation of the genome of this strain (7.25 Mb), showing the most complex S. fredii genome sequenced to date. It comprises seven replicons: one chromosome and six plasmids. Among these plasmids, pSfHH103d, also known as the symbiotic plasmid pSymA, harbors most of the genes involved in symbiosis. Due to limitations of the sequencing technology used at the time and the presence of high number of clusters of transposable elements, this plasmid could only be partially assembled as four separated contigs. Methods: In this work, we have used a combination of PacBio and Illumina sequencing technologies to resolve these complex regions, obtaining an updated genome sequence (7.27 Mb). Results: This updated version includes an increase in size of the largest replicons (chromosome, pSfHH103d, and pSfHH103e) and a complete and closed symbiotic plasmid (pSfHH103d or pSymA). Additionally, we carried out a re-annotation of the updated genome, merging the previous annotation and the new one found in the remaining gaps. Notably, we found a high number of transposable elements in the HH103 genome, especially in three plasmids (pSfHH103b, pSfHH103c, and pSymA), a feature that is common among S. fredii strains. Conclusions: The combination of PacBio and Illumina sequencing technologies has allowed us to obtain a complete version of the HH103 pSymA. The presence of a high number of mobile elements seems to be a general characteristic among S. fredii strains, a fact that might be related to a high genome plasticity.
βTrCP facilitates MRN complex localization on chromatin to enhance DNA repair
(Nature Research, 2025-07-11) Belmonte Fernández, Alejandro; Herrero Ruíz, Joaquín Andrés; Sáez, Carmen; Japón, Miguel Á.; Mora Santos, María del Mar; Romero Portillo, Francisco; Microbiología; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; Agencia Estatal de Investigación. España
Genomic instability underlies various diseases, including cancer. This instability arises from defects in critical cellular processes, particularly those involved in DNA damage repair. Therefore, a detailed understanding of these repair mechanisms is essential for developing strategies to prevent or diagnose such diseases. The MRN complex, composed of MRE11, NBS1, and RAD50, is among the earliest elements involved in detecting DNA damage. Upon detecting DNA breaks, this complex triggers a cascade of signaling events that regulate both cell cycle arrest and DNA repair. These signaling pathways are tightly controlled by various post-translational modifications, notably ubiquitination. Although several ubiquitin ligases have been implicated in different stages of the DNA damage response, our knowledge remains limited. In this study, we reveal that βTrCP, a substrate-recognizing subunit of the SCF (SKP1/CUL1/F-box protein) ubiquitin ligase, interacts in vivo with the proteins of the MRN complex. These interactions occur in normally proliferating cells and are dependent on the GSK3 kinase. Moreover, we show that βTrCP enhances the recruitment of the MRN complex to chromatin through MRE11, thereby promoting the efficient DNA damage repair. Hence, alterations in βTrCP function affecting MRN dynamics could have severe consequences for the cell homeostasis.
tRNA hydroxylation is an epitranscriptomic modulator of metabolic states affecting Pseudomonas aeruginosa pathogenicity
(Oxford University Press, 2025-07-24) Frommeyer, Yannick N.; Gómez, Nicolás O.; Preusse, Matthias; Arce Rodríguez, Alejandro; Neubauer, Kerstin; Kennepohl, Benedikt; Häussler, Susanne; Microbiología; Deutsche Forschungsgemeinschaft / German Research Foundation (DFG); Ministry of Science and Culture of Lower Saxony
Post-transcriptional modification of transfer RNAs (tRNAs) represents an essential layer of translational regulation critical for bacterial adaptation to environmental changes. Increasing evidence links the tRNA epitranscriptome to pivotal roles in the regulation of gene expression and various cellular processes, including stress responses and establishment of virulence. In this study, we used mass spectrometry and nanopore sequencing to quantify and identify the sites of TrhPO-dependent tRNA hydroxylation in total and purified Pseudomonas aeruginosa tRNAs. Furthermore, transcriptome, ribosome profiling, and proteome data were integrated to demonstrate the post-transcriptional consequences of the absence of xo5U34 modifications at the wobble position of selected tRNAs. We suggest that the impaired ability to infect host cells and attenuated virulence in Galleria mellonella are driven by changes in metabolic fluxes. In the absence of TrhPO-mediated tRNA modification, chorismate, the precursor for the biosynthesis of xo5U modifications, is funneled into alternative pathways, including the production of aromatic amino acids and phenazines. Our findings that metabolic rerouting, rather than changes in proteome profiles, attenuates P. aeruginosa virulence highlight the multifunctional roles of tRNA-modifying enzymes and suggest an underexplored role for these enzymes in monitoring and modulating metabolic fitness. These insights open new avenues for combatting the pathogenicity of this challenging opportunistic pathogen.
Reporting antimicrobial susceptibility and detection of carbapenemase production in single and double carbapenemase-producing Gram-negative clinical isolates: a nationwide proficiency study
(Frontiers Media, 2025-06-10) Fernández-Cuenca, Felipe; Delgado Valverde, María Mercedes; Guridi-Fernández, Pablo; Gimeno-Cardona, Concepción; Hidalgo-Díaz, Carmen; Pascual Hernández, Álvaro; Microbiología; CTS210: Resistencia a Antimicrobianos
Purpose The objective was to assess the ability of Spanish clinical microbiology laboratories to report reliable carbapenem susceptibility test results and to detect carbapenemase production (CP) and/or carbapenemase genes in double (DCP) and single carbapenemase-producing (SCP) isolates.Methods Twelve isolates (8 SCP and 4 DCP) selected from the Andalusian Reference Laboratory were sent to 83 laboratories with requests for MICs and phenotypic and genotypic tests used for CP.Results Overall, there was lower essential agreement and a higher number of clinical errors in DCP than in SCP isolates. Phenotypic tests showed higher sensitivity for DCP isolates than for SCP isolates: lateral flow immunoassay (99.0% vs. 95.1%), carbapenem inactivation method (100% vs. 93%) and chromogenic media (100% vs. 83.3%); conversely, sensitivities for DCP versus SCP isolates was lower using disk diffusion with inhibitors (83.3% vs. 90.4%) and hydrolysis-based assays (81.3% vs. 86.1%). Molecular methods showed higher sensitivity for DCP isolates than phenotypic methods, and higher sensitivity for DCP isolates than for SCP isolates. In addition, concordance between genes detected and the reference was higher in DCP than in SCP isolates (98.9% vs. 83%). However, blaVIM-1 and blaIMP-8 were not detected in 77.5% and 42.2% of the determinations, respectively, for DCP isolates.Conclusion The main differences between DCP versus SCP isolates were the lower reliability of gradient strips, higher overall sensitivity of phenotypic methods for DCP isolates, but lower sensitivity with disk diffusion inhibitors and hydrolysis-based assays. Molecular assays were generally more sensitive for carbapenemase gene detection in DCP than in SCP isolates, although concordance was lower.
Phosphate solubilization capacity by bacteria in soybean crops
(International Institute of Ecology, 2025-07-04) Vey, R.T.; Jacques, R.J.S.; Pavinato, P.S.; López Baena, Francisco Javier; Spanevello, J.F.; Bronzatto, E.S.; Martín, T.N.; Microbiología; Conselho Nacional de Desenvolvimento Científico e Tecnológico. Brasil; Coordenação de Aperfeiçoamento de Pessoal de Nivel Superior. Brasil; BIO169: Biotecnología de la Interacción de Microorganismos con Leguminosas y Otras Plantas de Interés Agrícola
The availability of phosphorus (P) to plants is reduced by its binding to solid mineral and soil organic particles. However, phosphate-solubilizing microorganisms can increase nutrient availability by secreting extracellular enzymes such as fosfatases. The objective was to evaluate the phosphate solubilization capacity of bacteria coinoculated in soybean crops. Soybean plants were grown in nutrient solution in a combination of treatments of bacteria inoculated into the seeds [Bradyrhizobium japonicum (Brady); Brady + Pseudomonas fluorescens (Pf); Brady + Bacillus megaterium (Bm) + Bacillus subtilis (Bs); and Brady + Bs] with doses of P. In the laboratory, another experiment was conducted to evaluate the phosphate solubilization capacity in the NBRIP solid culture medium by the bacteria Bs, Bs+Bm, Pf and the isolate of Pseudomonas spp. The root dry mass increased by 201.26% with Brady+Bs coinoculation. Considering the phosphorus content in the aerial part of plant content for a dose of 40 kg ha-1 of NH4H2PO4, with B. japonicum + P. fluorescens resulted in an increase of 26.7% in relation to the control. The use of B. japonicum + B. megaterium/B. subtilis increased the phosphorus concentration in the shoot plant by 22.5%. In the laboratory solubilization test, the bacteria B. subtilis showed a medium phosphate solubilization index, making this bacterium an alternative for better use of this nutrient in the soil.
Implications of gene expression heterogeneity in the interplay between acquired resistance and bacterial metabolism
(Nature Research, 2025-07-22) Romero Muñoz, María; Pulido, Marina R.; Recacha, Esther; Díaz Díaz, Sara; Murillo Torres, Marina; Docobo Pérez, Fernando; Rodríguez Martínez, José Manuel; Microbiología; CTS210: Resistencia a Antimicrobianos
Gene expression heterogeneity has an impact on human bacterial pathogens responses, including antimicrobial resistance genes expression. Promoter region variability in resistance genes may include different regulatory boxes involved in metabolic processes essential for bacterial survival. In this study, a molecular tool was developed to characterize promoter region variability and resistance gene expression. For these, 46 bacterial clinical isolates were used. Sequence analysis of resistance genes promoter region showed the existence of different variants for each promoter and identified gene-specific regulatory boxes. Using a fluorescent transcriptional reporter, we analysed the most common promoter variants of the most prevalent acquired resistance genes in clinical isolates (qnrA, qnrB, blaOXA-48, blaKPC-3 and blaVIM-1, aac(6’)-Ib-cr, and fosA). Gene expression fluctuations were found to be dependent on culture medium used. Specific gene promoter variants showed lower expression levels in poor (M9) medium (p < 0.0001) and an induction of expression under antimicrobials presence (tetracycline, quinolones and beta-lactams). qnrB1 genes were regulated by phoB and lexA boxes; blaOXA-48 was regulated by the argR box or fnr and arcA boxes. Differences in regulation of resistance gene promoter variants observed in this study suggest heterogeneity in expression under different bacterial culture conditions and a new link between metabolism and acquired resistance.
Case report: Analysis of phage therapy failure in a patient with a Pseudomonas aeruginosa prosthetic vascular graft infection
(Frontiers Media SA, 2023-05-19) Blasco, Lucía; López-Hernández, Inmaculada; Rodríguez-Fernández, Miguel; Pérez-Florido, Javier; Casimiro-Soriguer, Carlos S.; Djebara, Sarah; Merabishvili, Maya; Pirnay, Jean Paul; Rodríguez-Baño, Jesús; Tomás, María; López-Cortés, Luis E.; Medicina; Microbiología
Clinical case of a patient with a Pseudomonas aeruginosa multidrug-resistant prosthetic vascular graft infection which was treated with a cocktail of phages (PT07, 14/01, and PNM) in combination with ceftazidime-avibactam (CZA). After the application of the phage treatment and in absence of antimicrobial therapy, a new P. aeruginosa bloodstream infection (BSI) with a septic residual limb metastasis occurred, now involving a wild-type strain being susceptible to ß-lactams and quinolones. Clinical strains were analyzed by microbiology and whole genome sequencing techniques. In relation with phage administration, the clinical isolates of P. aeruginosa before phage therapy (HE2011471) and post phage therapy (HE2105886) showed a clonal relationship but with important genomic changes which could be involved in the resistance to this therapy. Finally, phenotypic studies showed a decrease in Minimum Inhibitory Concentration (MIC) to ß-lactams and quinolones as well as an increase of the biofilm production and phage resistant mutants in the clinical isolate of P. aeruginosa post phage therapy.
Fosfomycin in bacteraemic urinary tract infection due to multidrug-resistant Escherichia coli: insights of post hoc DOOR analysis of the FOREST trial
(Taylor & Francis Ltd, 2024-12-09) Sojo-Dorado, Jesús; López-Hernández, Inmaculada; Gutiérrez Gutiérrez, Belén; Rosa-Riestra, Sandra; Docobo Pérez, Fernando; Hernánez-Torres, Alicia; Pascual Hernández, Álvaro; Rodríguez-Baño, Jesús; Medicina; Microbiología; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Instituto de Salud Carlos III; Gobierno de España; BIO210: Microorganismos Eucariotas
Purpose: A post hoc analysis of data from a previously published clinical trial was conducted using the desirability of outcome ranking (DOOR) methodology with the aim provide additional information on the use of fosfomycin for the treatment of bacteraemic urinary tract infection (BUTI) caused by multi-drug-resistant (MDR) E. coli. Methods: Three DOOR systems with five, six and seven categories, respectively were developed. Safety and efficacy were prioritised in all rankings, but step down to oral therapy and exposure to antibiotics with lower ecological impact were also considered in DOOR-6 and DOOR-7. The probability that a patients assigned to fosfomycin was classified into a more desirable outcome category was calculated for the three DOOR definitions. Subgroups analyses and an ordinal logistic regression model were also performed. Results: Data from 143 participants were analysed. The probability of having a more desirable outcome after treatment with fosfomycin versus the comparators was 0.44 (95% CI 0.36 - 0.52) for DOOR-5; 0.50 (95% IC 0.42 - 0.58) using DOOR-6 and 0.61 (95% CI 0.53-0.69) with DOOR-7. In subgroups, the highest probability of having a better DOOR with fosfomycin was seen in the clinically evaluable population and among patients without chronic heart disease or renal insufficiency for the DOOR-7 definition. Conclusions: DOOR analysis could be applied to the FOREST trial data; the results were somehow different for the different DOOR systems used. Overall, fosfomycin was favoured when oral step-down treatment and use of antibiotics with lower ecological impact were included.
Treatment of Infections Caused by Extended-Spectrum-Beta-Lactamase-, AmpC-, and Carbapenemase-Producing Enterobacteriaceae
(American Society Microbiology, 2018-02-14) Rodríguez-Baño, Jesús; Gutiérrez Gutiérrez, Belén; Machuca, Isabel; Pascual Hernández, Álvaro; Medicina; Microbiología; Gobierno de España; Instituto de Salud Carlos III; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); CTS210: Resistencia a Antimicrobianos
Therapy of invasive infections due to multidrug-resistant Enterobacteriaceae (MDR-E) is challenging, and some of the few active drugs are not available in many countries. For extended-spectrum β-lactamase and AmpC producers, carbapenems are the drugs of choice, but alternatives are needed because the rate of carbapenem resistance is rising. Potential active drugs include classic and newer β-lactam–β-lactamase inhibitor combinations, cephamycins, temocillin, aminoglycosides, tigecycline, fosfomycin, and, rarely, fluoroquinolones or trimethoprim-sulfamethoxazole. These drugs might be considered in some specific situations. AmpC producers are resistant to cephamycins, but cefepime is an option. In the case of carbapenemase-producing Enterobacteriaceae (CPE), only some “second-line” drugs, such as polymyxins, tigecycline, aminoglycosides, and fosfomycin, may be active; double carbapenems can also be considered in specific situations. Combination therapy is associated with better outcomes for high-risk patients, such as those in septic shock or with pneumonia. Ceftazidime-avibactam was recently approved and is active against KPC and OXA-48 producers; the available experience is scarce but promising, although development of resistance is a concern. New drugs active against some CPE isolates are in different stages of development, including meropenem-vaborbactam, imipenem-relebactam, plazomicin, cefiderocol, eravacycline, and aztreonam-avibactam. Overall, therapy of MDR-E infection must be individualized according to the susceptibility profile, type, and severity of infection and the features of the patient.

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