Artículos (Microbiología)

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A broad molecular phylogeny of ciliates: Identification of major evolutionary trends and radiations within the phylum
(National Academy of Sciences, 1992) Baroin-Tourancheau, Anne; Delgado, Pilar; Perasso, Roland; Adoutte, André; Universidad de Sevilla. Departamento de Microbiología
The cellular architecture of ciliates is one of the most complex known within eukaryotes. Detailed systematic schemes have thus been constructed through extensive comparative morphological and ultrastructural analysis of the ciliature and of its internal cytoskeletal derivatives (the infraciliature), as well as of the architecture of the oral apparatus. In recent years, a consensus was reached in which the phylum was divided in eight classes as defined by Lynn and Corliss [Lynn, D. H. and Corliss, J. O. (1991) in Microscopic Anatomy of Invertebrates: Protozoa (Wiley-Liss, New York), Vol. 1, pp. 333-467]. By comparing partial sequences of the large subunit rRNA molecule, and by using both distance-matrix and maximum- parsimony-tree construction methods (checked by bootstrapping), we examine the phylogenetic relationships of 22 species belonging to seven of these eight classes. At low taxonomic levels, the traditional grouping of the species is generally confirmed. At higher taxonomic levels, the branching pattern of these seven classes is resolved in several deeply separated major branches. Surprisingly, the first emerging one contains the heterotrichs and is strongly associated with a karyorelictid but deeply separated from hypotrichs. The litostomes, the oligohymenophorans, and the hypotrichs separate later in a bush-like topology hindering the resolution of their order of diversification. These results show a much more ancient origin of heterotrichs than was classically assumed, indicating that asymmetric, abundantly ciliated oral apparatuses do not correspond to 'highly evolved' traits as previously thought. They also suggest the occurrence of a major radiative explosion in the evolutionary history of the ciliates, yielding five of the eight classes of the phylum. These classes appear to differ essentially according to the cytoskeletal architecture used to shape and sustain the cellular cortex (a process of essential adaptative and morphogenetic importance in ciliates).
A complex receptor locus confers responsiveness to necrosis and ethylene-inducing like peptides in Brassica napus
(WILEY, 2024) Yalcin, HA.; Jacott, Catherine N.; Ramírez-González, R; Steuernagel, B; Sidhu, GS; Kirby, R.; Verbeek, E.; Schoonbeek, HJ.; Ridout, CJ.; Wells, R.; Universidad de Sevilla. Departamento de Microbiología; UK Research & Innovation (UKRI); Biotechnology and Biological Sciences Research Council (BBSRC)
Brassica crops are susceptible to diseases which can be mitigated by breeding for resistance. MAMPs (microbe-associated molecular patterns) are conserved molecules of pathogens that elicit host defences known as pattern-triggered immunity (PTI). Necrosis and Ethylene-inducing peptide 1-like proteins (NLPs) are MAMPs found in a wide range of phytopathogens. We studied the response to BcNEP2, a representative NLP from Botrytis cinerea, and showed that it contributes to disease resistance in Brassica napus. To map regions conferring NLP response, we used the production of reactive oxygen species (ROS) induced during PTI across a population of diverse B. napus accessions for associative transcriptomics (AT), and bulk segregant analysis (BSA) on DNA pools created from a cross of NLP-responsive and non-responsive lines. In silico mapping with AT identified two peaks for NLP responsiveness on chromosomes A04 and C05 whereas the BSA identified one peak on A04. BSA delimited the region for NLP-responsiveness to 3 Mbp, containing 245 genes on the Darmor-bzh reference genome and four co-segregating KASP markers were identified. The same pipeline with the ZS11 genome confirmed the highest-associated region on chromosome A04. Comparative BLAST analysis revealed unannotated clusters of receptor-like protein (RLP) homologues on ZS11 chromosome A04. However, no specific RLP homologue conferring NLP response could be identified. Our results also suggest that BR-SIGNALLING KINASE1 may be involved with modulating the NLP response. Overall, we demonstrate that responsiveness to NLP contributes to disease resistance in B. napus and define the associated genomic location. These results can have practical application in crop improvement.
A Complex Regulatory Network Governs the Expression of Symbiotic Genes in Sinorhizobium Fredii HH103
(Frontiers Media, 2023) Navarro Gómez, Pilar; Fuentes Romero, Francisco; Pérez Montaño, Francisco de Asís; Jiménez Guerrero, Irene; Alías Villegas, Cynthia; Ayala García, Paula; Almozara, Andrés; Medina Morillas, Carlos; Ollero Márquez, Francisco Javier; Rodríguez Carvajal, Miguel Ángel; Ruiz Sainz, José Enrique; López Baena, Francisco Javier; Vinardell González, José María; Acosta Jurado, Sebastián; Universidad de Sevilla. Departamento de Microbiología; Universidad de Sevilla. Departamento de Química orgánica; Ministerio de Ciencia e Innovación (MICIN). España
Introduction: The establishment of the rhizobium-legume nitrogen-fixing symbiosis relies on the interchange of molecular signals between the two symbionts. We have previously studied by RNA-seq the effect of the symbiotic regulators NodD1, SyrM, and TtsI on the expression of the symbiotic genes (the nod regulon) of Sinorhizobium fredii HH103 upon treatment with the isoflavone genistein. In this work we have further investigated this regulatory network by incorporating new RNA-seq data of HH103 mutants in two other regulatory genes, nodD2 and nolR. Both genes code for global regulators with a predominant repressor effect on the nod regulon, although NodD2 acts as an activator of a small number of HH103 symbiotic genes. Methods: By combining RNA-seq data, qPCR experiments, and b-galactosidase assays of HH103 mutants harbouring a lacZ gene inserted into a regulatory gene, we have analysed the regulatory relations between the nodD1, nodD2, nolR, syrM, and ttsI genes, confirming previous data and discovering previously unknown relations. Results and discussion: Previously we showed that HH103 mutants in the nodD2, nolR, syrM, or ttsI genes gain effective nodulation with Lotus japonicus, a model legume, although with different symbiotic performances. Here we show that the combinations of mutations in these genes led, in most cases, to a decrease in symbiotic effectiveness, although all of them retained the ability to induce the formation of nitrogen-fixing nodules. In fact, the nodD2, nolR, and syrM single and double mutants share a set of Nod factors, either overproduced by them or not generated by the wild-type strain, that might be responsible for gaining effective nodulation with L. japonicus.
A concept for international societally relevant microbiology education and microbiology knowledge promulgation in society
(Wiley Open Access, 2024-05-27) Timmis, Kenneth; Hallsworth, John Edward; McGenity, Terry J.; Armstrong, Rachel; Colom, María Francisca; Karahan, Zeynep Ceren; Chavarría, Max; Bernal Guzmán, Patricia; Boyd, Eric S.; Serna, Jéssica Gil; Universidad de Sevilla. Departamento de Microbiología
The biosphere of planet Earth is a micro-bial world: a vast reactor of countless microbiallydriven chemical transformations and energy trans-fers that push and pull many planetary geochemicalprocesses, including the cycling of the elements oflife, mitigate or amplify climate change (e.g., NatureReviews Microbiology, 2019, 17, 569) and impact thewell-being and activities of all organisms, including hu-mans. Microbes are both our ancestors and creatorsof the planetary chemistry that allowed us to evolve(e.g., Life's engines: How microbes made earth habit-able, 2023). To understand how the biosphere func-tions, how humans can influence its developmentand live more sustainably with the other organismssharing it, we need to understand the microbes. Ina recent editorial (Environmental Microbiology, 2019,21, 1513), we advocated for improved microbiologyliteracy in society. Our concept of microbiology liter-acy is not based on knowledge of the academic sub-ject of microbiology, with its multitude of componenttopics, plus the growing number of additional topicsfrom other disciplines that become vitally importantelements of current microbiology. Rather it is focusedon microbial activities that impact us–individuals/communities/nations/the human world–and the bio-sphere and that are key to reaching informed deci-sions on a multitude of issues that regularly confrontus, ranging from personal issues to crises of globalimportance. In other words, it is knowledge and un-derstanding essential for adulthood and the transi-tion to it, knowledge and understanding that mustbe acquired early in life in school. The 2019 Editorialmarked the launch of the International MicrobiologyLiteracy Initiative, the IMiLI.
A lipopolysaccharide-free outer membrane vesicle vaccine protects against Acinetobacter baumannii infection
(Elsevier, 2020-01) Pulido, Marina R.; García Quintanilla, Meritxell de Jesús; Pachón Díaz, Jerónimo; McConnell, Michael J.; Universidad de Sevilla. Departamento de Microbiología; Universidad de Sevilla. Departamento de Medicina; Universidad de Sevilla. CTS210: Resistencia a Antimicrobianos; Universidad de Sevilla. CTS203: Estudio de las Enfermedades Infecciosas
Outer membrane vesicles (OMVs) were isolated from an Acinetobacter strain deficient in lipopolysaccharide (LPS) due to a mutation in lpxD (IB010). Two immunizations with 10 µg of IB010 OMVs elicited total IgG, IgM, IgG1 and IgG2c titers similar to those observed after immunization with OMVs derived from the parental strain (ATCC 19606), and IB010 OMVs plus purified LPS. Immunization with IB010 OMVs resulted in significantly reduced post-infection spleen bacterial loads and serum IL-1β and IL-6 levels compared to control mice in a disseminated sepsis model. Mice immunized with 10 µg IB010 OMVs demonstrated significant, but partial, protection (75%) against infection, whereas mice immunized with ATCC 19606 OMVs or IB010 OMVs plus purified LPS were completely protected. Immunization of mice with 100 µg of IB010 OMVs completely protected mice from infection. This study demonstrates that LPS deficient A. baumannii produces OMVs, and that immunization with these OMVs elicits protective immunity against infection.
A multinational, preregistered cohort study of β-lactam/β-lactamase inhibitor combinations for treatment of bloodstream infections due to extended-spectrum-β-lactamase-producing enterobacteriaceae
(American Society for Microbiology, 2016-07-01) Pascual Hernández, Álvaro; Rodríguez-Baño, Jesús; Martínez Martínez, Luis; Cueto López, Marina de; Universidad de Sevilla. Departamento de Microbiología; Universidad de Sevilla. Departamento de Medicina; European Union (UE). FP7
The spread of extended-spectrum-β-lactamase (ESBL)-producing Enterobacteriaceae (ESBL-E) is leading to increased carbapenem consumption. Alternatives to carbapenems need to be investigated. We investigated whether β-lactam/β-lactamase inhibitor (BLBLI) combinations are as effective as carbapenems in the treatment of bloodstream infections (BSI) due to ESBL-E. A multinational, retrospective cohort study was performed. Patients with monomicrobial BSI due to ESBL-E were studied; specific criteria were applied for inclusion of patients in the empirical-therapy (ET) cohort (ETC; 365 patients), targeted-therapy (TT) cohort (TTC; 601 patients), and global cohort (GC; 627 patients). The main outcome variables were cure/improvement rate at day 14 and all-cause 30-day mortality. Multivariate analysis, propensity scores (PS), and sensitivity analyses were used to control for confounding. The cure/improvement rates with BLBLIs and carbapenems were 80.0% and 78.9% in the ETC and 90.2% and 85.5% in the TTC, respectively. The 30-day mortality rates were 17.6% and 20% in the ETC and 9.8% and 13.9% in the TTC, respectively. The adjusted odds ratio (OR) (95% confidence interval [CI]) values for cure/improvement rate with ET with BLBLIs were 1.37 (0.69 to 2.76); for TT, they were 1.61 (0.58 to 4.86). Regarding 30-day mortality, the adjusted OR (95% CI) values were 0.55 (0.25 to 1.18) for ET and 0.59 (0.19 to 1.71) for TT. The results were consistent in all subgroups studied, in a stratified analysis according to quartiles of PS, in PS-matched cases, and in the GC. BLBLIs, if active in vitro, appear to be as effective as carbapenems for ET and TT of BSI due to ESLB-E regardless of the source and specific species. These data may help to avoid the overuse of carbapenems.
A novel stabilization mechanism for the type VI secretion system sheath
(National Academy of Sciences, 2021) Bernal Guzmán, Patricia; Furniss, R. Christopher D.; Fecht, Selina; Leung, Rhoda C. Y.; Spiga, Livia; Mavridou, Despoina A. I.; Filloux, Alain; Universidad de Sevilla. Departamento de Microbiología
The type VI secretion system (T6SS) is a phage-derived contractile nanomachine primarily involved in interbacterial competition. Its pivotal component, TssA, is indispensable for the assembly of the T6SS sheath structure, the contraction of which propels a payload of effector proteins into neighboring cells. Despite their key function, TssA proteins exhibit unexpected diversity and exist in two major forms, a short form (TssAS) and a long form (TssAL). While TssAL proteins interact with a partner, called TagA, to anchor the distal end of the extended sheath, the mechanism for the stabilization of TssAS-containing T6SSs remains unknown. Here we discover a class of structural components that interact with short TssA proteins and contribute to T6SS assembly by stabilizing the polymerizing sheath from the baseplate. We demonstrate that the presence of these components is important for full sheath extension and optimal firing. Moreover, we show that the pairing of each form of TssA with a different class of sheath stabilization proteins results in T6SS apparatuses that either reside in the cell for some time or fire immediately after sheath extension. We propose that this diversity in firing dynamics could contribute to the specialization of the T6SS to suit bacterial lifestyles in diverse environmental niches.
A peripheral protein associated with the cis-Golgi network redistributes in the intermediate compartment upon brefeldin A treatment
(Rockefeller University Press, 1994) Ríos Sánchez, Rosa María; Tassin, Anne-Marie; Celati, Claude; Antony, Claude; Boissier, Marie-Christophe; Homberg, Jean-Claude; Bornens, Michel; Universidad de Sevilla. Departamento de Microbiología; Ministerio de Sanidad y Consumo. España
Human autoantibodies offer unique tools for the study of cellular constituents since they usually recognize highly conserved components, the most difficult to detect due to their low immunogenicity. The serum from a patient with Sjogren's syndrome (RM serum) showing a very high reactivity to the Golgi complex has been shown to immunoprecipitate and to immunodetect by Western blotting experiments a protein of mol wt 210,000 (p210) that was shown to be peripheral and cytoplasmically disposed. A close examination of the p210 labeling revealed some differences with Golgi markers: RM serum staining was slightly more extensive than several Golgi markers and showed a discontinuous or granular appearance. Nocodazole induced a specific and early segregation of many p210-associated vesicles or tubules from Golgi apparatus. Upon brefeldin A treatment, p210 did not redistribute in the ER as did other Golgi proteins. In contrast, it exhibited a vesicular pattern reminiscent to that displayed by proteins residing in the intermediate compartment. Double staining immunofluorescence using the RM serum and the marker of the intermediate compartment, p58, revealed segregation of both proteins in control conditions but colocalization in BFA-treated cells. We have further demonstrated by combining different drug treatments that p210-containing elements in brefeldin A-treated cells belong indeed to the intermediate compartment. Experiments on brefeldin A recovery suggested that these p210 elements might play a role in reformation and repositioning of the Golgi apparatus. Ultrastructural localization performed by immunoperoxidase staining allowed us to establish that p210 interacted with the external side of an abundant tubulo-vesicular system on the cis side of the Golgi complex which extended to connecting structures and vesicles between saccules or stacks of cisternae. p210 appears to be a novel protein residing in the cis- Golgi network that may cycle between the Golgi apparatus and the intermediate compartment.
A Point Mutation in the Transcriptional Repressor PerR Results in a Constitutive Oxidative Stress Response in Clostridioides difficile 630(delta)Derm
(American Society for Microbiology, 2021-03-03) Troitzsch, D; Zhang, H; Dittmann, S; Dusterhoft, D; Moller, TA; Borrero de Acuña, José Manuel; Sievers, S; Universidad de Sevilla. Departamento de Microbiología
The human pathogen Clostridioides difficile has evolved into the leading cause of nosocomial diarrhea. The bacterium is capable of spore formation, which even allows survival of antibiotic treatment. Although C. difficile features an anaerobic lifestyle, we determined a remarkably high oxygen tolerance of the laboratory reference strain 630Δerm. A mutation of a single nucleotide (single nucleotide polymorphism [SNP]) in the DNA sequence (A to G) of the gene encoding the regulatory protein PerR results in an amino acid substitution (Thr to Ala) in one of the helices of the helix-turn-helix DNA binding domain of this transcriptional repressor in C. difficile 630Δerm. PerR is a sensor protein for hydrogen peroxide and controls the expression of genes involved in the oxidative stress response. We show that PerR of C. difficile 630Δerm has lost its ability to bind the promoter region of PerR-controlled genes. This results in a constitutive derepression of genes encoding oxidative stress proteins such as a rubrerythrin (rbr1) whose mRNA abundance under anaerobic conditions was increased by a factor of about 7 compared to its parental strain C. difficile 630. Rubrerythrin repression in strain 630Δerm could be restored by the introduction of PerR from strain 630. The permanent oxidative stress response of C. difficile 630Δerm observed here should be considered in physiological and pathophysiological investigations based on this widely used model strain.
A pyrF auxotrophic mutant of Sinorhizobium fredii HH103 impaired in its symbiotic interaction with soybean and other legumes
(Sociedad Española de Microbiología. Viguera Editores, 2007) Crespo Rivas, Juan Carlos; Margaret Oliver, Isabel María; Pérez Montaño, Francisco de Asís; López Baena, Francisco Javier; Vinardell González, José María; Ollero Márquez, Francisco Javier; Moreno Onorato, Francisco Javier; Ruiz Sainz, José Enrique; Buendía Clavería, Ana María; Universidad de Sevilla. Departamento de Microbiología; Universidad de Sevilla. Departamento de Biología Celular
Transposon Tn5-Mob mutagenesis allowed the selection of a Sinorhizobium fredii HH103 mutant derivative (SVQ 292) that requires the presence of uracil to grow in minimal media. The mutated gene, pyrF, codes for an orotidine-5 ́- monophosphate decarboxylase (EC 4.1.1.23). Mutant SVQ 292 and its parental prototrophic mutant HH103 showed similar Nod-factor and lipopolysaccharide profiles. The symbiotic properties of mutant SVQ 292 were severely impaired with all legumes tested. Mutant SVQ 292 formed small ineffective nodules on Cajanus cajan and abnormal nodules (pseudonodules) unable to fix nitrogen on Glycine max (soybean), Macroptitlium atropurpureum, Indigofera tinctoria, and Desmodium cana-dense. It also did not induce any macroscopic response in Macrotyloma axillare roots. The symbiotic capacity of SVQ 292 with soybean was not enhanced by the addition of uracil to the plant nutritive solution.
A Set of Lotus japonicus Gifu × Lotus burttii Recombinant Inbred Lines Facilitates Map-based Cloning and QTL Mapping
(Oxford University Press, 2012) Sandal, Niels; Jin, Haojie; Rodríguez Navarro, Dulce Nombre; Ruiz Sainz, José Enrique; Universidad de Sevilla. Departamento de Microbiología
Model legumes such as Lotus japonicus have contributed significantly to the understanding of symbiotic nitrogen fixation. This insight is mainly a result of forward genetic screens followed by map-based cloning to identify causal alleles. The L. japonicus ecotype ‘Gifu’ was used as a common parent for inter-accession crosses to produce F2 mapping populations either with other L. japonicus ecotypes, MG-20 and Funakura, or with the related species L. filicaulis. These populations have all been used for genetic studies but segregation distortion, suppression of recombination, low polymorphism levels, and poor viability have also been observed. More recently, the diploid species L. burttii has been identified as a fertile crossing partner of L. japonicus. To assess its qualities in genetic linkage analysis and to enable quantitative trait locus (QTL) mapping for a wider range of traits in Lotus species, we have generated and genotyped a set of 163 Gifu × L. burttii recombinant inbred lines (RILs). By direct comparisons of RIL and F2 population data, we show that L. burttii is a valid alternative to MG-20 as a Gifu mapping partner. In addition, we demonstrate the utility of the Gifu × L. burttii RILs in QTL mapping by identifying an Nfr1-linked QTL for Sinorhizobium fredii nodulation.
A single mutation in Securin induces chromosomal instability and enhances cell invasion
(Elsevier, 2013) Mora Santos, María del Mar; Castilla, Carolina; Herrero Ruiz, Joaquín; Giráldez Macías, Servando; Limón Mortés, María Cristina; Sáez, Carmen; Japón Rodríguez, Miguel Ángel; Tortolero García, María Dolores; Romero Portillo, Francisco; Universidad de Sevilla. Departamento de Microbiología; Ministerio de Ciencia e Innovación; Ministerio de Sanidad. España; Junta de Andalucía
Pituitary tumour transforming gene (pttg1) encodes Securin, a protein involved in the inhibition of sister chromatid separation binding to Separase until the onset of anaphase. Separase is a cysteine-protease that degrades cohesin to segregate the sister chromatids to opposite poles of the cell. The amount of Securin is strongly regulated because it should allow Separase activation when it is degraded by the anaphase promoting complex/cyclosome, should arrest the cell cycle after DNA damage, when it is degraded through SKP1-CUL1-βTrCP ubiquitin ligase, and its overexpression induces tumour formation and correlates with metastasis in multiple tumours. Securin is a phosphoprotein that contains 32 potentially phosphorylatable residues. We mutated and analysed most of them, and found a single mutant, hSecT60A, that showed enhanced oncogenic properties. Our fluorescence activated cell sorting analysis, fluorescence in situ hybridisation assays, tumour cell migration and invasion experiments and gene expression by microarrays analysis clearly involved hSecT60A in chromosomal instability and cell invasion. These results show, for the first time, that a single mutation in pttg1 is sufficient to trigger the oncogenic properties of Securin. The finding of this point mutation in patients might be used as an effective strategy for early detection of cancer.
A transcriptomic analysis of the effect of genistein on Sinorhizobium fredii HH103 reveals novel rhizobial genes putatively involved in symbiosis
(Nature Publishing Group, 2016) Pérez Montaño, Francisco de Asís; Jiménez Guerrero, Irene; Acosta Jurado, Sebastián; Navarro Gómez, Pilar; Ollero Márquez, Francisco Javier; Ruiz Sainz, José Enrique; López Baena, Francisco Javier; Vinardell González, José María; Universidad de Sevilla. Departamento de Microbiología
Sinorhizobium fredii HH103 is a rhizobial soybean symbiont that exhibits an extremely broad host-range. Flavonoids exuded by legume roots induce the expression of rhizobial symbiotic genes and activate the bacterial protein NodD, which binds to regulatory DNA sequences called nod boxes (NB). NB drive the expression of genes involved in the production of molecular signals (Nod factors) as well as the transcription of ttsI, whose encoded product binds to tts boxes (TB), inducing the secretion of proteins (effectors) through the type 3 secretion system (T3SS). In this work, a S. fredii HH103 global gene expression analysis in the presence of the flavonoid genistein was carried out, revealing a complex regulatory network. Three groups of genes differentially expressed were identified: i) genes controlled by NB, ii) genes regulated by TB, and iii) genes not preceded by a NB or a TB. Interestingly, we have found differentially expressed genes not previously studied in rhizobia, being some of them not related to Nod factors or the T3SS. Future characterization of these putative symbiotic-related genes could shed light on the understanding of the complex molecular dialogue established between rhizobia and legumes.
Accumulation of Poly(beta-Hydroxybutyrate) by Halobacteria
(American Society for Microbiology, 1986) Fernández Castillo, Rosario; Rodríguez Valera, Francisco; González Ramos, J.; Ruiz Berraquero, Francisco; Universidad de Sevilla. Departamento de Microbiología; Comisión Asesora de Investigación Científica y Técnica (CAICYT). España
Some species of extremely halophilic archaebacteria, Halobacteriaceae, have been shown to accumulate large amounts of poly(P-hydroxybutyrate) under conditions of nitrogen limitation and abundant carbon source. The production of poly(P3-hydroxybutyrate), at least in large quantities, was restricted to two carbohydrate-utilizing species, Halobacterium mediterranei and H. volcanii. In addition to the nutrients in the media, the salt concentration also influenced poly(P-hydroxybutyrate) accumulation, which was greater at lower salt concentrations. The possible application of these microorganisms for the production of biodegradable plastics is discussed.
Active Biopolymeric Films Inoculated with Bdellovibrio bacteriovorus, a Predatory Bacterium
(Multidisciplinary Digital Publishing Institute (MDPI), 2021) Sáenz-Santos, Christian Mariel; Opemipo Oyedara, Omotayo; García-Tejeda, Yunia Verónica; Romero-Bastida, Claudia A.; García-Oropesa, Esperanza Milagros; Villalobo Polo, Eduardo; Rodríguez-Pérez, Mario A.; Universidad de Sevilla. Departamento de Microbiología
The objective of the present work was to evaluate novel active films made with biopolymeric matrices as carriers of a living Bdellovibrio bacteriovorus HD100 strain, a predatory bacterium with antimicrobial potentials against pathogens. Biopolymer films were prepared by a casting method using the following mixtures: collagen/sodium alginate/sorbitol (CA-S), collagen/sodium alginate/glycerol (CA-G), and tapioca starch/sodium alginate/glycerol (StA-G). The effects of the film formulations on the viability of the B. bacteriovorus was investigated by using Fourier Transform Infrared (FTIR) spectroscopy, Differential Scanning Calorimetry (DSC), and Scanning Electron Microscopy (SEM). SEM showed that Bdellovibrio bacteriovorus morphology was not altered in the polymeric films. FTIR spectroscopy provided information about the structural composition of the films. CA-S showed less reduction in the viability of B. bacteriovorus after its entrapment; thus, CA-S proved to be a better agent for the immobilization and preservation of B. bacteriovorus to enhance its predatory activities during application against Escherichia coli.
Activities of ABT-773 against Listeria monocytogenes and coryneform bacteria of clinical interest
(American Society for Microbiology, 2003-04-01) Conejo Gonzalo, Mª Carmen; Martínez Martínez, Luis; Pascual Hernández, Álvaro; Suárez, Ana Isabel; Perea Pérez, Evelio José; Universidad de Sevilla. Departamento de Microbiología
The in vitro activities of ABT-773 were evaluated against 15 Listeria monocytogenes strains and 196 coryneform bacteria isolated from clinical samples. One hundred percent of the L. monocytogenes strains were inhibited by ≤0.015 μg of ABT-773/ml. MICs of ABT-773 (μg/ml) at which 50% of the isolates tested were inhibited (MIC50s) and MIC90s for other organisms were 0.125 and 0.5 (Corynebacterium amycolatum), 1 and >32 (Corynebacterium jeikeium), 0.03 and >32 (Corynebacterium minutissimum), >32 and >32 (Corynebacterium pseudodiphtheriticum and Corynebacterium urealyticum), 0.125 and >32 (Corynebacterium striatum), and 0.03 and 0.5 (Rhodococcus equi), respectively.
Activities of gemifloxacin and five other antimicrobial agents against Listeria monocytogenes and coryneform bacteria isolated from clinical samples
(American Society for Microbiology, 2001-07-31) Martínez Martínez, Luis; Joyanes, Providencia; Moreno-Suárez, Ana Isabel; Perea Pérez, Evelio José; Universidad de Sevilla. Departamento de Microbiología
The in vitro activities of gemifloxacin, ciprofloxacin, ampicillin, doxycycline, gentamicin, and vancomycin were evaluated against 15 Listeria monocytogenes strains and 205 coryneform bacteria isolated from clinical samples. The percentages of strains inhibited by gemifloxacin at 0.5 μg/ml were 100% (L. monocytogenes), 93.3% (Brevibacterium spp.), 90% (Corynebacterium minutissimum), 42.5% (Corynebacterium amycolatum), 20% (Corynebacterium striatum), 12.5% (Corynebacterium jeikeium), and 10% (Corynebacterium urealyticum). One hundred percent of the L. monocytogenes strains were inhibited by 0.25 μg of gemifloxacin per ml, whereas 0% of the strains were inhibited by 0.25 μg of ciprofloxacin per ml. Vancomycin at 2 μg/ml inhibited all strains. Doxycycline and gentamicin at 4 μg/ml inhibited 94 and 49% of the strains, respectively, while ampicillin at 0.5, 2, and 8 μg/ml inhibited 24, 61, and 66% of the strains, respectively. It is concluded that gemifloxacin shows good in vitro activity against L. monocytogenes and coryneform bacteria except C. jeikeium and C. urealyticum.
Activities of imipenem and cephalosporins against clonally related strains of Escherichia coli hyperproducing chromosomal β-lactamase and showing altered porin profiles
(American Society for Microbiology, 2000-09-06) Martínez Martínez, Luis; Conejo Gonzalo, Mª Carmen; Pascual Hernández, Álvaro; Hernández Allés, Santiago; Ramírez de Arellano Ramos, E.; Benedí, Vicente J.; Perea Pérez, Evelio José; Universidad de Sevilla. Departamento de Microbiología
Forty clonally related clinical isolates of Escherichia coli from hospitalized patients were resistant to cefoxitin (MICs, >256 μg/ml) and ceftazidime (MICs, 32 to 256 μg/ml) and were intermediate or resistant to cefotaxime (MICs, 16 to 128 μg/ml) but susceptible to both cefepime (MICs, 0.5 to 2 μg/ml) and imipenem (MICs, 0.125 to 0.25 μg/ml). Resistance to β-lactams was related to high-level production of AmpC β-lactamase and loss of OmpF porin.
Activity of Cefepime, Carbapenems and New β-lactam/β-lactamase Inhibitor Combinations on Enterobacter Cloacae Complex and Klebsiella Aerogenes in Spain (SMART 2016–2022)
(Oxford University Press, 2024) Rodríguez Villodres, Ángel; Lepe Balsalobre, Esperanza; Ortiz de la Rosa, José Manuel; Giner Almaraz, Salvador; González De Herrero, Elisa; Cercenado, Emilia; García Fernández, Sergio; Benito, Rafael; Ponz Mir, Ricardo; Cantón, Rafael; Lepe Jiménez, José Antonio; Universidad de Sevilla. Departamento de Microbiología; Ministerio de Ciencia, Innovación y Universidades (MICINN). España
Objectives: To analyse the susceptibility profile to cefepime, carbapenems and new β-lactam/β-lactamase inhibitor combinations in Enterobacter cloacae complex and Klebsiella aerogenes isolated from intra-abdominal, urinary, respiratory and bloodstream infections in the SMART (Study for Monitoring Antimicrobial Resistance Trends) surveillance study in Spain. Methods: The susceptibilities of 759 isolates (473 E. cloacae complex and 286 K. aerogenes) collected in 11 Spanish hospitals from 2016 to 2022 were analysed following the EUCAST 2023 criteria. Molecular characterization looking for β-lactamase genes was performed through PCR and DNA sequencing analysis. Results: E. cloacae complex showed resistance to third-generation cephalosporins in 25% of the cases, whereas K. aerogenes was resistant in 35%. Regarding cefepime, resistance in E. cloacae was higher (10%) than in K. aerogenes (2%). Carbapenems showed >85% activity in both microorganisms. Ceftazidime/avibactam, imipenem/relebactam and meropenem/vaborbactam had good activity against these microorganisms (>95%). In contrast, the activity of ceftolozane/tazobactam was lower (80%). A high proportion of the isolates resistant to new β-lactam/β-lactamase inhibitor combinations carried a carbapenemase, mainly OXA-48-like and VIM-1. Conclusions: Ceftazidime/avibactam, imipenem/relebactam and meropenem/vaborbactam show high activity against both E. cloacae complex and K. aerogenes isolates recovered in the SMART-Spain study. In contrast, differences have been found in the case of cefepime, showing more activity against K. aerogenes than E. cloacae complex. These results are useful for antimicrobial stewardship programmes and for the implementation of local and national guidelines.
Activity of cefiderocol against high-risk clones of multidrug-resistant Enterobacterales, Acinetobacter baumannii, Pseudomonas aeruginosa and Stenotrophomonas maltophilia
(Oxford, 2020) Delgado Valverde, María Mercedes; Conejo, Mª del Carmen; Serrano, Lara; Fernández Cuenca, Felipe Manuel; Pascual Hernández, Álvaro; Universidad de Sevilla. Departamento de Microbiología
BACKGROUND: Cefiderocol is a novel siderophore cephalosporin, developed for activity against MDR Gram-negative bacilli (MDR-GNB). OBJECTIVES: To assess the in vitro antibacterial activity of cefiderocol against a collection of MDR-GNB clinical isolates from hospitals in southern Spain. METHODS: Two hundred and thirty-one isolates of successful clones were tested: 125 Enterobacterales (121 ESBL- and/or carbapenemase-producing Klebsiella pneumoniae and 4 carbapenemase-producing Enterobacter cloacae), 80 Acinetobacter baumannii, 6 Pseudomonas aeruginosa and 20 Stenotrophomonas maltophilia. Ceftolozane/tazobactam, ceftazidime, ceftazidime/avibactam, cefepime, aztreonam, meropenem, amikacin, ciprofloxacin, colistin and tigecycline were used as comparators against Enterobacterales, P. aeruginosa and A. baumannii. Minocycline, levofloxacin and trimethoprim/sulfamethoxazole were studied against S. maltophilia instead of aztreonam, ciprofloxacin and cefepime. MICs were determined by broth microdilution according to CLSI guidelines. MIC determination was performed in CAMHB for all antimicrobials except cefiderocol, where iron-depleted CAMHB was used. RESULTS: Cefiderocol showed potent in vitro activity against the isolates analysed. MIC50 and MIC90 values were in the ranges 0.125-8 mg/L and 0.5-8 mg/L, respectively, and 98% of isolates were inhibited at ≤4 mg/L. Only five isolates showed cefiderocol MICs of >4 mg/L: three ST2/OXA-24/40-producing A. baumannii, one ST114/VIM-1-producing E. cloacae and one ST114/VIM-1 + OXA-48-producing E. cloacae. All KPC-3-producing K. pneumoniae were susceptible to cefiderocol, even those resistant to ceftazidime/avibactam. P. aeruginosa isolates showed cefiderocol MICs of <4 mg/L, including those resistant to ceftolozane/tazobactam. S. maltophilia isolates displayed cefiderocol MICs of <4 mg/L, including those resistant to levofloxacin and/or trimethoprim/sulfamethoxazole. CONCLUSIONS: Cefiderocol showed excellent activity against MDR-GNB, including carbapenem-resistant isolates, and was the most active antimicrobial tested against this collection.

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