Transferable AmpCs in Klebsiella pneumoniae: interplay with peptidoglycan recycling, mechanisms of hyperproduction, and virulence implications

Chromosomal and transferable AmpC β-lactamases represent top resistance mechanisms in different gram-negatives, but knowledge regarding the latter, mostly concerning regulation and virulence-related implications, is far from being complete. To fill this gap, we used Klebsiella pneumoniae (KP) and two different plasmid-encoded AmpCs [DHA-1 (AmpR regulator linked, inducible) and CMY-2 (constitutive)] as models to perform a study in which we show that blockade of peptidoglycan recycling through AmpG permease inactivation abolished DHA-1 inducibility but did not affect CMY-2 production and neither did it alter KP pathogenic behavior. Moreover, whereas regular production of both AmpC-type enzymes did not attenuate KP virulence, when blaDHA-1 was expressed in an ampG-defective mutant, Galleria mellonella killing was significantly (but not drastically) attenuated. Spontaneous DHA-1 hyperproducer mutants were readily obtained in vitro, showing slight or insignificant virulence attenuations together with high-level resistance to β-lactams only mildly affected by basal production (e.g., ceftazidime, ceftolozane/tazobactam). By analyzing diverse DHA-1-harboring clinical KP strains, we demonstrate that the natural selection of these hyperproducers is not exceptional (>10% of the collection), whereas mutational inactivation of the typical AmpC hyperproduction-related gene mpl was the most frequent underlying mechanism. The potential silent dissemination of this kind of strains, for which an important fitness cost-related contention barrier does not seem to exist, is envisaged as a neglected threat for most β-lactams effectiveness, including recently introduced combinations. Analyzing whether this phenomenon is applicable to other transferable β-lactamases and species as well as determining the levels of conferred resistance poses an essential topic to be addressed.IMPORTANCEAlthough there is solid knowledge about the regulation of transferable and especially chromosomal AmpC β-lactamases in Enterobacterales, there are still gaps to fill, mainly related to regulatory mechanisms and virulence interplays of the former. This work addresses them using Klebsiella pneumoniae as model, delving into a barely explored conception: the acquisition of a plasmid-encoded inducible AmpC-type enzyme whose production can be increased through selection of chromosomal mutations, entailing dramatically increased resistance compared to basal expression but minor associated virulence costs. Accordingly, we demonstrate that clinical K. pneumoniae DHA-1 hyperproducer strains are not exceptional. Through this study, we warn for the first time that this phenomenon may be a neglected new threat for β-lactams effectiveness (including some recently introduced ones) silently spreading in the clinical context, not only in K. pneumoniae but potentially also in other pathogens. These facts must be carefully considered in order to design future resistance-preventive strategies.

In vitro activity of human defensins HNP-1 and hBD-3 against multidrug-resistant ESKAPE Gram-negatives of clinical origin and selected peptidoglycan recycling-defective mutants

The use of immune compounds as antimicrobial adjuvants is a classic idea recovering timeliness in the current antibiotic resistance scenario. However, the activity of certain antimicrobial peptides against ESKAPE Gram-negatives has not been sufficiently investigated. The objective of this study was to determine the activities of human defensins HNP-1 and hBD-3 alone or combined with permeabilizing/peptidoglycan-targeting agents against clinical ESKAPE Gram-negatives [Acinetobacter baumannii (AB), Enterobacter cloacae (EC), Klebsiella pneumoniae (KP), and acute/chronic Pseudomonas aeruginosa (PA)]. Lethal concentrations (LCs) of HNP-1 and hBD-3 were determined in four collections of multidrug resistant EC, AB, KP, and PA clinical strains (10-36 isolates depending on the collection). These defensins act through membrane permeabilization plus peptidoglycan building blockade, enabling that alterations in peptidoglycan recycling may increase their activity, which is why different recycling-defective mutants were also included. Combinations with physiological lysozyme and subinhibitory colistin for bactericidal activities determination, and with meropenem for minimum inhibitory concentrations (MICs), were also assessed. HNP-1 showed undetectable activity (LC > 32 mg/L for all strains). hBD-3 showed appreciable activities: LC ranges 2-16, 8-8, 8->32, and 8->32 mg/L for AB, EC, KP, and PA, being PA strains from cystic fibrosis significantly more resistant than acute origin ones. None of the peptidoglycan recycling-defective mutants showed greater susceptibility to HNP-1/hBD-3. Combination with colistin or lysozyme did not change their bactericidal power, and virtually neither did meropenem + hBD-3 compared to meropenem MICs. This is the first study comparatively analyzing the HNP-1/hBD-3 activities against the ESKAPE Gram-negatives, and demonstrates interesting bactericidal capacities of hBD-3 mostly against AB and EC.

IMPORTANCE

In the current scenario of critical need for new antimicrobials against multidrug-resistant bacteria, all options must be considered, including classic ideas such as the use of purified immune compounds. However, information regarding the activity of certain human defensins against ESKAPE Gram-negatives was incomplete. This is the first study comparatively assessing the in vitro activity of two membrane-permeabilizing/peptidoglycan construction-blocking defensins (HNP-1 and hBD-3) against relevant clinical collections of ESKAPE Gram-negatives, alone or in combination with permeabilizers, additional peptidoglycan-targeting attacks, or the blockade of its recycling. Our data suggest that hBD-3 has a notable bactericidal activity against multidrug-resistant Acinetobacter baumannii and Enterobacter cloacae strains that should be considered as potential adjuvant option. Our results suggest for the first time an increased resistance of Pseudomonas aeruginosa strains from chronic infection compared to acute origin ones, and provide new clues about the predominant mode of action of hBD-3 against Gram-negatives (permeabilization rather than peptidoglycan-targeting).

Filling knowledge gaps related to AmpC-dependent β-lactam resistance in Enterobacter cloacae

Enterobacter cloacae starred different pioneer studies that enabled the development of a widely accepted model for the peptidoglycan metabolism-linked regulation of intrinsic class C cephalosporinases, highly conserved in different Gram-negatives. However, some mechanistic and fitness/virulence-related aspects of E. cloacae choromosomal AmpC-dependent resistance are not completely understood. The present study including knockout mutants, β-lactamase cloning, gene expression analysis, characterization of resistance phenotypes, and the Galleria mellonella infection model fills these gaps demonstrating that: (i) AmpC enzyme does not show any collateral activity impacting fitness/virulence; (ii) AmpC hyperproduction mediated by ampD inactivation does not entail any biological cost; (iii) alteration of peptidoglycan recycling alone or combined with AmpC hyperproduction causes no attenuation of E. cloacae virulence in contrast to other species; (iv) derepression of E. cloacae AmpC does not follow a stepwise dynamics linked to the sequential inactivation of AmpD amidase homologues as happens in Pseudomonas aeruginosa; (v) the enigmatic additional putative AmpC-type β-lactamase generally present in E. cloacae does not contribute to the classical cephalosporinase hyperproduction-based resistance, having a negligible impact on phenotypes even when hyperproduced from multicopy vector. This study reveals interesting particularities in the chromosomal AmpC-related behavior of E. cloacae that complete the knowledge on this top resistance mechanism.

The balance between antibiotic resistance and fitness/virulence in Pseudomonas aeruginosa: an update on basic knowledge and fundamental research

The interplay between antibiotic resistance and bacterial fitness/virulence has attracted the interest of researchers for decades because of its therapeutic implications, since it is classically assumed that resistance usually entails certain biological costs. Reviews on this topic revise the published data from a general point of view, including studies based on clinical strains or in vitro-evolved mutants in which the resistance phenotype is seen as a final outcome, i.e., a combination of mechanisms. However, a review analyzing the resistance/fitness balance from the basic research perspective, compiling studies in which the different resistance pathways and respective biological costs are individually approached, was missing. Here we cover this gap, specifically focusing on Pseudomonas aeruginosa, a pathogen that stands out because of its extraordinary capacity for resistance development and for which a considerable number of recent and particular data on the interplay with fitness/virulence have been released. The revised information, split into horizontally-acquired vs. mutation-driven resistance, suggests a great complexity and even controversy in the resistance-fitness/virulence balance in the acute infection context, with results ranging from high costs linked to certain pathways to others that are seemingly cost-free or even cases of resistance mechanisms contributing to increased pathogenic capacities. The elusive mechanistic basis for some enigmatic data, knowledge gaps, and possibilities for therapeutic exploitation are discussed. The information gathered suggests that resistance-fitness/virulence interplay may be a source of potential antipseudomonal targets and thus, this review poses the elementary first step for the future development of these strategies harnessing certain resistance-associated biological burdens.

Bacterial virulence regulation through soluble peptidoglycan fragments sensing and response: knowledge gaps and therapeutic potential

Given the growing clinical-epidemiological threat posed by the phenomenon of antibiotic resistance, new therapeutic options are urgently needed, especially against top nosocomial pathogens such as those within the ESKAPE group. In this scenario, research is pushed to explore therapeutic alternatives and, among these, those oriented toward reducing bacterial pathogenic power could pose encouraging options. However, the first step in developing these antivirulence weapons is to find weak points in the bacterial biology to be attacked with the goal of dampening pathogenesis. In this regard, during the last decades some studies have directly/indirectly suggested that certain soluble peptidoglycan-derived fragments display virulence-regulatory capacities, likely through similar mechanisms to those followed to regulate the production of several β-lactamases: binding to specific transcriptional regulators and/or sensing/activation of two-component systems. These data suggest the existence of intra- and also intercellular peptidoglycan-derived signaling capable of impacting bacterial behavior, and hence likely exploitable from the therapeutic perspective. Using the well-known phenomenon of peptidoglycan metabolism-linked β-lactamase regulation as a starting point, we gather and integrate the studies connecting soluble peptidoglycan sensing with fitness/virulence regulation in Gram-negatives, dissecting the gaps in current knowledge that need filling to enable potential therapeutic strategy development, a topic which is also finally discussed.

Role of Enzymatic Activity in the Biological Cost Associated with the Production of AmpC β-Lactamases in Pseudomonas aeruginosa

In the current scenario of growing antibiotic resistance, understanding the interplay between resistance mechanisms and biological costs is crucial for designing therapeutic strategies. In this regard, intrinsic AmpC β-lactamase hyperproduction is probably the most important resistance mechanism of Pseudomonas aeruginosa, proven to entail important biological burdens that attenuate virulence mostly under peptidoglycan recycling alterations. P. aeruginosa can acquire resistance to new β-lactam-β-lactamase inhibitor combinations (ceftazidime-avibactam and ceftolozane-tazobactam) through mutations affecting ampC and its regulatory genes, but the impact of these mutations on the associated biological cost and the role that β-lactamase activity plays per se in contributing to the above-mentioned virulence attenuation are unknown. The same questions remain unsolved for plasmid-encoded AmpC-type β-lactamases such as FOX enzymes, some of which also provide resistance to new β-lactam-β-lactamase inhibitor combinations. Here, we assessed from different perspectives the effects of changes in the active center and, thus, in the hydrolytic spectrum resistance to inhibitors of AmpC-type β-lactamases on the fitness and virulence of P. aeruginosa, using site-directed mutagenesis; the previously described AmpC variants T96I, G183D, and ΔG229-E247; and, finally, blaFOX-4 versus blaFOX-8. Our results indicate the essential role of AmpC activity per se in causing the reported full virulence attenuation (in terms of growth, motility, cytotoxicity, and Galleria mellonella larvae killing), although the biological cost of the above-mentioned AmpC-type variants was similar to that of the wild-type enzymes. This suggests that there is not an important biological burden that may limit the selection/spread of these variants, which could progressively compromise the future effectiveness of the above-mentioned drug combinations. IMPORTANCE The growing antibiotic resistance of the top nosocomial pathogen Pseudomonas aeruginosa pushes research to explore new therapeutic strategies, for which the resistance-versus-virulence balance is a promising source of targets. While resistance often entails significant biological costs, little is known about the bases of the virulence attenuations associated with a resistance mechanism as extraordinarily relevant as β-lactamase production. We demonstrate that besides potential energy and cell wall alterations, the enzymatic activity of the P. aeruginosa cephalosporinase AmpC is essential for causing the full attenuation associated with its hyperproduction by affecting different features related to pathogenesis, a fact exploitable from the antivirulence perspective. Less encouraging, we also show that the production of different chromosomal/plasmid-encoded AmpC derivatives conferring resistance to some of the newest antibiotic combinations causes no significantly increased biological burdens, which suggests a free way for the selection/spread of these types of variants, potentially compromising the future effectiveness of these antipseudomonal therapies.

Effects of Inhaled Corticosteroids on the Innate Immunological Response to Pseudomonas aeruginosa Infection in Patients with COPD

Inhaled corticosteroids (ICS) use is associated with an increased risk of Pseudomonas aeruginosa (PA) infection in patients with COPD. We aimed to evaluate the effects of ICS on alveolar macrophages in response to PA in COPD patients with and without baseline ICS treatment (COPD and COPD + ICS, respectively) as well as smoker and nonsmoker controls. To do so, cells were infected with PA and cotreated with budesonide (BUD) or fluticasone propionate (FLU). The analysis of NF-κB and c-jun activity revealed a significant increase in both factors in response to PA cotreated with BUD/FLU in smokers but not in COPD or COPD + ICS patients when compared with PA infection alone. The expression of Toll-like receptor 2 (TLR2) and the transcription factor c-jun were induced upon PA infection in nonsmokers only. Moreover, in the smoker and COPD groups, there was a significant increase in TLR2 and a decrease in c-jun expression when treated with BUD/FLU after PA infection, which were not observed in COPD + ICS patients. Therefore, the chronic use of ICS seemingly makes the macrophages tolerant to BUD/FLU stimulation compared with those from patients not treated with ICS, promoting an impaired recognition of PA and activity of alveolar macrophages in terms of altered expression of TLR2 and cytokine production, which could explain the increased risk of PA infection in COPD patients under ICS treatment.

Retrospective analysis of risk factors for bone metastasis in newly diagnosed prostate cancer patients

OBJECTIVE

The aim of the study was to analyze the clinical data of newly diagnosed prostate cancer (PCa) patients with bone metastasis and to explore the relevant risk factors.

PATIENTS AND METHODS

The clinical data of 251 patients with PCa, who were initially diagnosed in our hospital from February 2015 to October 2021, were retrospectively analyzed. According to the whole-body bone scan results, patients were divided into the bone metastasis group (n = 66) and the non-bone metastasis group (n = 185). The patient's age, total prostate-specific antigen (TPSA), free PSA (fPSA), prostate volume, alkaline phosphatase (ALP), Gleason score, erythrocyte sedimentation rate (ESR), and pelvic lymph node metastasis were collected. Univariate correlation and multivariate regression analyses, together with receiver operating characteristic curve, were used to analyze PCa bone metastasis-related factors.

RESULTS

The incidence of bone metastasis in newly diagnosed PCa was about 26.29% (66/251). Among them, the incidence of pelvic metastasis was the highest, at 78.78% (52/251), and multiple bone metastases were significantly higher than single bone metastasis (80.31% vs. 19.69%). Univariate correlation analysis indicated that age, Gleason score, ESR, TPSA, ALP, fPSA/PSA, capsular infiltration, and pelvic lymph node metastasis (p < 0.05) were highly correlated with PCa bone metastasis. Multivariate Logistic regression analysis showed that TPSA (95% CI: 0.977-1.284, p = 0.007), ALP (95% CI: 1.008-1.080, p = 0.016), Gleasons core (95% CI: 2.110-82.349, p = 0.006), ESR (95% CI: 1.062-1.104, p = 0.003), and pelvic lymph node metastasis (95% CI: 1.537--33.239, p = 0.012) were independent risk factors for bone metastasis of PCa. The cut-off values for TPSA, ALP, Gleason score, and ESR were 33.78 ng/ml, 73.65 U/L, 7.5, and 23.5 mm/h, respectively. Additionally, the respective sensitivities for TPSA, ALP, Gleason score, and ESR were 81.8%, 75.8%, 68.2% and 77.3%, and the respective specificities was 90.3%, 98.9%, 98.4%, and 74.6%.

CONCLUSIONS

TPSA, ALP, Gleason score, ESR and pelvic lymph node metastasis are independent risk factors for bone metastasis of PCa.

Impact of Peptidoglycan Recycling Blockade and Expression of Horizontally Acquired β-Lactamases on Pseudomonas aeruginosa Virulence

In the current scenario of antibiotic resistance magnification, new weapons against top nosocomial pathogens like Pseudomonas aeruginosa are urgently needed. The interplay between β-lactam resistance and virulence is considered a promising source of targets to be attacked by antivirulence therapies, and in this regard, we previously showed that a peptidoglycan recycling blockade dramatically attenuated the pathogenic power of P. aeruginosa strains hyperproducing the chromosomal β-lactamase AmpC. Here, we sought to ascertain whether this observation could be applicable to other β-lactamases. To do so, P. aeruginosa wild-type or peptidoglycan recycling-defective strains (ΔampG and ΔnagZ) harboring different cloned β-lactamases (transferable GES, VIM, and OXA types) were used to assess their virulence in Galleria mellonella larvae by determining 50% lethal doses (LD50s). A mild yet significant LD50 increase was observed after peptidoglycan recycling disruption per se, whereas the expression of class A and B enzymes did not impact virulence. While the production of the narrow-spectrum class D OXA-2 entailed a slight attenuation, its extended-spectrum derivatives OXA-226 (W159R [bearing a change of W to R at position 159]), OXA-161 (N148D), and principally, OXA-539 (D149 duplication) were associated with outstanding virulence impairments, especially in recycling-defective backgrounds (with some LD50s being >1,000-fold that of the wild type). Although their exact molecular bases remain to be deciphered, these results suggest that mutations affecting the catalytic center and, therefore, the hydrolytic spectrum of OXA-2-derived enzymes also drastically impact the pathogenic power of P. aeruginosa. This work provides new and relevant knowledge to the complex topic of the interplay between the production of β-lactamases and virulence that could be useful to build future therapeutic strategies against P. aeruginosa. IMPORTANCE Pseudomonas aeruginosa is one of the leading nosocomial pathogens whose growing resistance makes the development of therapeutic options extremely urgent. The resistance-virulence interplay has classically aroused researchers' interest as a source of therapeutic targets. In this regard, we describe a wide array of virulence attenuations associated with different transferable β-lactamases, among which the production of OXA-2-derived extended-spectrum β-lactamases stood out as a dramatic handicap for pathogenesis, likely as a side effect of mutations causing the expansion of their hydrolytic spectrums. Moreover, our results confirm the validity of disturbing peptidoglycan recycling as a weapon to attenuate P. aeruginosa virulence in class C and D β-lactamase production backgrounds. In the current scenario of dissemination of horizontally acquired β-lactamases, this work brings out new data on the complex interplay between the production of specific enzymes and virulence attenuation that, if complemented with the characterization of the underlying mechanisms, will likely be exploitable to develop future virulence-targeting antipseudomonal strategies.

Mammals' humoral immune proteins and peptides targeting the bacterial envelope: from natural protection to therapeutic applications against multidrug‐resistant Gram ‐negatives

Mammalian innate immunity employs several humoral ‘weapons’ that target the bacterial envelope. The threats posed by the multidrug‐resistant ‘ESKAPE’ Gram‐negative pathogens (Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) are forcing researchers to explore new therapeutic options, including the use of these immune elements. Here we review bacterial envelope‐targeting (peptidoglycan and/or membrane‐targeting) proteins/peptides of the mammalian immune system that are most likely to have therapeutic applications. Firstly we discuss their general features and protective activity against ESKAPE Gram‐negatives in the host. We then gather, integrate, and discuss recent research on experimental therapeutics harnessing their bactericidal power, based on their exogenous administration and also on the discovery of bacterial and/or host targets that improve the performance of this endogenous immunity, as a novel therapeutic concept. We identify weak points and knowledge gaps in current research in this field and suggest areas for future work to obtain successful envelope‐targeting therapeutic options to tackle the challenge of antimicrobial resistance.

Inhaled corticosteroid dose is associated with Pseudomonas aeruginosa infection in severe COPD

INTRODUCTION

Patients with chronic obstructive pulmonary disease (COPD) with frequent exacerbations (ExCOPD) are commonly treated with inhaled corticosteroids (ICS) and are at risk of infections caused by potential pathogenic bacteria (PPB) including Pseudomonas aeruginosa (PsA).

OBJECTIVES

To investigate the association between the use of ICS and PsA infection among ExCOPD.

METHODS

Case-control study with longitudinal follow-up that recruited ExCOPD after a hospitalisation due to exacerbation between 2012 and 2020. Patients with isolation of PsA (COPD-PsA) in sputum either during admission or follow-up were compared with those with other or no PPB. Clinical, functional characteristics, DDD, use of ICS and survival were evaluated. Cox regression analysis was performed to evaluate the risk factors associated to PsA infection and mortality.

RESULTS

358 patients (78% male, mean age 73±9 years) were enrolled and followed up for a median of 4 years (IQR=3-8). 173 patients (48.3%) had at least a positive culture for PsA. COPD-PsA had more frequent exacerbations, more severe airflow limitation and higher mortality (69.4% vs 46.5%, p<0.001). There were no differences in the use of ICS between groups but the dose of ICS was significantly higher among COPD-PsA (median of 500 µg fluticasone propionate equivalents (IQR=250-1000) vs 400 µg (IQR=200-1000), p=0.007). Blood eosinophil count (BEC) was not different between ICS users and non-users. In multivariate analysis, the dose of ICS was an independent risk factor for PsA infection and mortality but not ICS use.

CONCLUSIONS

ICS dose, but not its use, could be a risk factor for PsA infection in patients with severe COPD regardless of BEC.

In vitro dynamics and mechanisms of resistance development to imipenem and imipenem/relebactam in Pseudomonas aeruginosa

OBJECTIVES

We analysed the dynamics and mechanisms of resistance development to imipenem alone or combined with relebactam in Pseudomonas aeruginosa WT (PAO1) and mutator (PAOMS; ΔmutS) strains.

METHODS

PAO1 or PAOMS strains were incubated for 24 h in Mueller-Hinton Broth with 0.125-64 mg/L of imipenem ± relebactam 4 mg/L. Tubes from the highest antibiotic concentration showing growth were reinoculated in fresh medium containing concentrations up to 64 mg/L of imipenem ± relebactam for 7 days. Two colonies per strain, replicate experiment and antibiotic from early (Day 1) and late (Day 7) cultures were characterized by determining the susceptibility profiles, WGS and determination of the expression of ampC and efflux-pump-coding genes. Virulence was studied in a Caenorhabditis elegans infection model.

RESULTS

Relebactam reduced imipenem resistance development for both strains, although resistance emerged much faster for PAOMS. WGS indicated that imipenem resistance was associated with mutations in the porin OprD and regulators of ampC, while the mutations in imipenem/relebactam-resistant mutants were located in oprD and regulatoras of MexAB-OprM. High-level imipenem/relebactam resistance was only documented in the PAOMS strain and was associated with an additional specific (T680A) mutation located in the catalytic pocket of ponA (PBP1a) and with reduced virulence in the C. elegans model.

CONCLUSIONS

Imipenem/relebactam could be a useful alternative for the treatment of MDR P. aeruginosa infections, potentially reducing resistance development during treatment. Moreover, this work deciphers the potential resistance mechanisms that may emerge upon the introduction of this novel combination into clinical practice.

The Hyalella species flock of Lake Titicaca (Crustacea: Amphipoda): perspectives and drawbacks of dna-based identification

Lake Titicaca, in the High Andes of Perú and Bolivia, harbours the world’s third most speciose ancient-lake amphipod radiation on record. A minimum of nineteen species of Hyalella derived from at least five independent colonization episodes concentrate in this high altitude water body, although the actual species number present has not yet been established and could be much higher. Herein, we take advantage of the description of three new species (H. krolli, H. gonzalezi, and H. hirsuta) and the re-description of other two (H. solida and H. nefrens) to assess the feasibility of adopting a dna-based identification approach to resolve the magnitude of this highly speciose amphipod assemblage. A Bayesian phylogenetic analysis of the evolutionary relationships among South American Hyalella cox1 haplotypes, including those of four out of the five species dealt with herein, shows a great disagreement between taxonomic units delimited under morphological and genetic data, hampering species identification exclusively based on cox1 dna barcode sequences.

6-Halopyridylmethylidene Penicillin-Based Sulfones Efficiently Inactivate the Natural Resistance of Pseudomonas aeruginosa to β-Lactam Antibiotics

Pseudomonas aeruginosa, a major cause of nosocomial infections, is considered a paradigm of antimicrobial resistance, largely due to hyperproduction of chromosomal cephalosporinase AmpC. Here, we explore the ability of 6-pyridylmethylidene penicillin-based sulfones 1-3 to inactivate the AmpC β-lactamase and thus rescue the activity of the antipseudomonal ceftazidime. These compounds increased the susceptibility to ceftazidime in a collection of clinical isolates and PAO1 mutant strains with different ampC expression levels and also improved the inhibition kinetics relative to avibactam, displaying a slow deacylation rate and involving the formation of an indolizine adduct. Bromide 2 was the inhibitor with the lowest K_I (15.6 nM) and the highest inhibitory efficiency (k_inact/K_I). Computational studies using diverse AmpC enzymes revealed that the aromatic moiety in 1-3 targets a tunnel-like site adjacent to the catalytic serine and induces the folding of the H10 helix, indicating the potential value of this not-always-evident pocket in drug design.

Proteomics evaluation of enniatins acute toxicity in rat liver

Enniatins (ENs) are emerging mycotoxins produced by Fusarium fungi which are cytotoxic also at low concentrations due to its ionophoric properties. The aim of this study was to evaluate the hepatic toxicity of ENs exposure at different concentrations in Wistar rats through a proteomic approach. Animals were intoxicated by oral gavage with medium (EN A 256, ENA1 353, ENB 540, ENB1 296 μg/mL) and high concentrations (ENA 513, ENA1 706, ENB 1021, ENB1 593 μg/mL) of an ENs mixture and sacrificed after 8 h. Protein extraction was performed using powdered liver. Peptides were analyzed using a liquid chromatography coupled with a quadrupole time-of-flight mass spectrometer. Proteins were filtered by abundance using Mass Professional Profiler software (Agilent Technologies) and 57 were differentially expressed when compared to the control. In terms of abundance, the liver biomarker Carboamoyl-phosphate synthase showed the highest levels in all conditions employed while actin-1 had the lowest. Bioinformatic analysis using DAVID platform reported acetylation, nucleotide phosphate-binding region:NAD and catalytic activity as the most represented terms. Furthermore, metabolism was the most significant and enriched pathway in Reactome overrepresentation. In conclusion, ENs acute exposure caused protein expression changes related to major cellular processes in rats, hinting its involvement in liver disturbance.

Comparative Mitogenomics in Hyalella (Amphipoda: Crustacea)

We present the sequencing and comparative analysis of 17 mitochondrial genomes of Nearctic and Neotropical amphipods of the genus Hyalella, most from the Andean Altiplano. The mitogenomes obtained comprised the usual 37 gene-set of the metazoan mitochondrial genome showing a gene rearrangement (a reverse transposition and a reversal) between the North and South American Hyalella mitogenomes. Hyalella mitochondrial genomes show the typical AT-richness and strong nucleotide bias among codon sites and strands of pancrustaceans. Protein-coding sequences are biased towards AT-rich codons, with a preference for leucine and serine amino acids. Numerous base changes (539) were found in tRNA stems, with 103 classified as fully compensatory, 253 hemi-compensatory and the remaining base mismatches and indels. Most compensatory Watson–Crick switches were AU -> GC linked in the same haplotype, whereas most hemi-compensatory changes resulted in wobble GU and a few AC pairs. These results suggest a pairing fitness increase in tRNAs after crossing low fitness valleys. Branch-site level models detected positive selection for several amino acid positions in up to eight mitochondrial genes, with atp6 and nad5 as the genes displaying more sites under selection.

Phylogenomics of the Hyalella amphipod species-flock of the Andean Altiplano

Species diversification in ancient lakes has enabled essential insights into evolutionary theory as they embody an evolutionary microcosm compared to continental terrestrial habitats. We have studied the high-altitude amphipods of the Andes Altiplano using mitogenomic, nuclear ribosomal and single-copy nuclear gene sequences obtained from 36 Hyalella genomic libraries, focusing on species of the Lake Titicaca and other water bodies of the Altiplano northern plateau. Results show that early Miocene South American lineages have recently (late Pliocene or early Pleistocene) diversified in the Andes with a striking morphological convergence among lineages. This pattern is consistent with the ecological opportunities (access to unoccupied resources, initial relaxed selection on ecologically-significant traits and low competition) offered by the lacustrine habitats established after the Andean uplift.

Morphological and molecular species boundaries in the Hyalella species flock of Lake Titicaca (Crustacea: Amphipoda)

The Hyalella species diversity in the high-altitude water bodies of the Andean Altiplano is addressed using mitochondrial cox1 sequences and implementing different molecular species delimitation criteria. We have recorded the presence of five major genetic lineages in the Altiplano, of which one seems to be exclusive to Lake Titicaca and nearby areas, whereas the rest occur also in other regions of South America. Eleven out of 36 South American entities diagnosed by molecular delimitation criteria in our study are likely endemic to the Titicaca and neighbouring water bodies. We have detected a remarkable disagreement between morphology and genetic data in the Titicacan Hyalella, with occurrence of several cases of the same morpho-species corresponding to several Molecular Operational Taxonomic Units (MOTUs), some even distantly related, and other instances where a particular MOTU is shared by a morphologically heterogeneous array of species, including species with body smooth and others with body heavily armoured. Species diversification and incongruence between morphological and molecular boundaries within this species assemblage may be associated to the sharp changes in hydrological conditions experienced by the water bodies of the Altiplano in the past, which included dramatic fluctuations in water level and salinity of Lake Titicaca. Such environmental shifts could have triggered rapid morphological changes and ecological differentiation within the Hyalella assemblage, followed by phenotypic convergence among the diverse lineages. Factors such as phenotypic plasticity, incomplete lineage sorting or admixture between divergent lineages might lie also at the root of the morphological-genetic incongruence described herein.

Activity of mammalian peptidoglycan-targeting immunity against Pseudomonas aeruginosa

Pseudomonas aeruginosa is one of the most important opportunistic pathogens, whose clinical relevance is not only due to the high morbidity/mortality of the infections caused, but also to its striking capacity for antibiotic resistance development. In the current scenario of a shortage of effective antipseudomonal drugs, it is essential to have thorough knowledge of the pathogen's biology from all sides, so as to find weak points for drug development. Obviously, one of these points could be the peptidoglycan, given its essential role for cell viability. Meanwhile, immune weapons targeting this structure could constitute an excellent model to be taken advantage of in order to design new therapeutic strategies. In this context, this review gathers all the information regarding the activity of mammalian peptidoglycan-targeting innate immunity (namely lysozyme and peptidoglycan recognition proteins), specifically against P. aeruginosa. All the published studies were considered, from both in vitro and in vivo fields, including works that envisage these weapons as options not only to potentiate their innate effects within the host or for use as exogenously administered treatments, but also harnessing their inflammatory and immune regulatory capacity to finally reduce damage in the patient. Altogether, this review has the objective of anticipating and discussing whether these innate immune resources, in combination or not with other drugs attacking certain P. aeruginosa targets leading to its increased sensitization, could be valid therapeutic antipseudomonal allies.

In Vivo Validation of Peptidoglycan Recycling as a Target to Disable AmpC-Mediated Resistance and Reduce Virulence Enhancing the Cell-Wall-Targeting Immunity

BACKGROUND

Searching for new strategies to defeat Pseudomonas aeruginosa is of paramount importance. Previous works in vitro showed that peptidoglycan recycling blockade disables AmpC-dependent resistance and enhances susceptibility against cell-wall-targeting immunity. Our objective was to validate these findings in murine models.This study shows for the first time in different murine models of infection that blocking the peptidoglycan recycling in Pseudomonas aeruginosa causes an important virulence impairment and disables AmpC-mediated resistance, being hence validated as a promising therapeutic target.

METHODS

Wildtype PAO1, recycling-defective AmpG and NagZ mutants, an AmpC hyperproducer dacB mutant, and their combinations were used to cause systemic/respiratory infections in mice. Their survival, bacterial burden, inflammation level, and effectiveness of ceftazidime or subtherapeutic colistin to treat the infections were assessed.

RESULTS

Inactivation of AmpG or NagZ significantly attenuated the virulence in terms of mice mortality, bacterial load, and inflammation. When inactivating these genes in the dacB-defective background, the β-lactam resistance phenotype was abolished, disabling the emergence of ceftazidime-resistant mutants, and restoring ceftazidime for treatment. Subtherapeutic colistin was shown to efficiently clear the infection caused by the recycling-defective strains, likely due to the combined effect with the mice cell-wall- targeting immunity.

CONCLUSIONS

This study brings us one step closer to new therapies intended to disable P. aeruginosa AmpC-mediated resistance and dampen its virulence, and strongly support the interest in developing efficient AmpG and/or NagZ inhibitors.

Comparative Analysis of Peptidoglycans From Pseudomonas aeruginosa Isolates Recovered From Chronic and Acute Infections

Pseudomonas aeruginosa is one of the first causes of acute nosocomial and chronic infections in patients with underlying respiratory pathologies such as cystic fibrosis (CF). It has been proposed that P. aeruginosa accumulates mutations driving to peptidoglycan modifications throughout the development of the CF-associated infection, as a strategy to lower the immune detection hence ameliorating the chronic persistence. As well, some studies dealing with peptidoglycan modifications driving to a better survival within the host have been published in other gram-negatives. According to these facts, the gram-negative peptidoglycan could be considered as a pathogen-associated molecular pattern with very important implications regarding the host’s detection-response, worthy to dissect in detail. For this reason, in this work we characterized for the first time the peptidoglycans of three large collections [early CF, late CF and acute infection (bloodstream) P. aeruginosa strains] from qualitative (HPLC), quantitative and inflammatory capacity-related perspectives. The final goal was to identify composition trends potentially supporting the cited strategy of evasion/resistance to the immune system and providing information regarding the differential intrinsic adaptation depending on the type of infection. Although we found several punctual strain-specific particularities, our results indicated a high degree of inter-collection uniformity in the peptidoglycan-related features and the absence of trends amongst the strains studied here. These results suggest that the peptidoglycan of P. aeruginosa is a notably conserved structure in natural isolates regardless of transitory changes that some external conditions could force. Finally, the inverse correlation between the relative amount of stem pentapeptides within the murein sacculus and the resistance to immune lytic attacks against the peptidoglycan was also suggested by our results. Altogether, this work is a major step ahead to understand the biology of peptidoglycan from P. aeruginosa natural strains, hopefully useful in future for therapeutic alternatives design.

miRNA-489 as a biomarker in diagnosis and treatment of cervical cancer

miRNA-489 was shown to be a suppressor factor in many cancers, however, evidence on the effects and mechanism of miRNA-489 in progression of cervical cancer is limited. So we aimed to determine the function of miRNA-489 in cervical cancer proliferation and apoptosis in our present study. Interestingly, we found that miRNA-489 was significantly down-regulated in cervical cancer tissues. miRNA-489 overexpression inhibited the cell proliferation and improved the cell apoptosis of cervical cancer cells. Further, miRNA-489 over-expression suppressed the activation of PI3K and AKT, and stimulated P53 proteins expression. In conclusion, our results suggested that miRNA-489 may be considered as a biomarker in cervical cancer and had suppressed the cell proliferation and stimulated cell apoptosis via PI3K/AKT/P53 signaling pathway (Fig. 5, Ref. 26). Text in PDF www.elis.sk.

Mechanisms leading to in vivo ceftolozane/tazobactam resistance development during the treatment of infections caused by MDR Pseudomonas aeruginosa

Objectives

Characterization of the mechanisms driving ceftolozane/tazobactam resistance development in 5 of 47 (10.6%) patients treated for MDR Pseudomonas aeruginosa infections in a Spanish hospital.

Methods

Five pairs of ceftolozane/tazobactam-susceptible/resistant P. aeruginosa isolates were studied. MICs were determined by broth microdilution, clonal relatedness was assessed by MLST and resistance mechanisms were investigated by phenotypic and genotypic methods, including WGS. ampC variants were cloned to assess their impact on resistance.

Results

In all five cases, the same clone was detected for the susceptible/resistant pairs; the widespread ST175 high-risk clone in four of the cases and ST179 in the remaining case. Genomic analysis of the four initial ST175 isolates revealed the characteristic OprD mutation (Q142X) responsible for carbapenem resistance and the AmpR mutation (G154R) responsible for AmpC overexpression and β-lactam resistance. The final isolates had developed ceftolozane/tazobactam and ceftazidime/avibactam resistance, and each additionally showed a mutation in AmpC: E247K in one of the isolates, T96I in two isolates and a deletion of 19 amino acids (G229-E247) in the remaining isolate. The cloned AmpC variants showed greatly increased ceftolozane/tazobactam and ceftazidime/avibactam MICs compared with WT AmpC, but, in contrast, yielded lower MICs of imipenem, cefepime and particularly piperacillin/tazobactam. On the other hand, ceftolozane/tazobactam resistance development in ST179 was shown to be driven by the emergence of the extended-spectrum OXA β-lactamase OXA-14, through the selection of an N146S mutation from OXA-10.

Conclusions

Modification of intrinsic (AmpC) and horizontally acquired β-lactamases appears to be the main mechanism leading to ceftolozane/tazobactam resistance in MDR P. aeruginosa.

Profiling the susceptibility of Pseudomonas aeruginosa strains from acute and chronic infections to cell-wall-targeting immune proteins

In the current scenario of high antibiotic resistance, the search for therapeutic options against Pseudomonas aeruginosa must be approached from different perspectives: cell-wall biology as source of bacterial weak points and our immune system as source of weapons. Our recent study suggests that once the permeability barrier has been overcome, the activity of our cell-wall-targeting immune proteins is notably enhanced, more in mutants with impaired peptidoglycan recycling. The present work aims at analyzing the activity of these proteins [lysozyme and Peptidoglycan-Recognition-Proteins (PGLYRPs)], alone or with a permeabilizer (subinhibitory colistin) in clinical strains, along with other features related to the cell-wall. We compared the most relevant and complementary scenarios: acute (bacteremia) and chronic infections [early/late isolates from lungs of cystic fibrosis (CF) patients]. Although a low activity of lysozyme/PGLYRPs per se (except punctual highly susceptible strains) was found, the colistin addition significantly increased their activity regardless of the strains’ colistin resistance levels. Our results show increased susceptibility in late CF isolates, suggesting that CF adaptation renders P. aeruginosa more vulnerable to proteins targeting the cell-wall. Thus, our work suggests that attacking some P. aeruginosa cell-wall biology-related elements to increase the activity of our innate weapons could be a promising therapeutic strategy.

Do cave orb spiders show unique behavioural adaptations to subterranean life? A review of the evidence

Interest for subterranean biology has risen sharply in recent years due to the simplicity of the cave environment. However, most studies have focussed on morphology with few studies looking at behaviour. The cave orb spiders show some unique behavioural adaptations compared to other orb spiders, including rudimentary orb webs, off-web foraging and a complex life cycle with a surface phase. Here, we compare these behavioural adaptations in the European Meta menardi and Meta bourneti to similar behaviours in surface-dwelling orb spiders. We find that current data suggest (1) an extreme reduction in the number of frame threads, (2) evidence of capturing non-flying prey, but not necessarily evidence for off-web foraging and (3) dispersal through a surface-dwelling life stage, but with data lacking on the role of ballooning and their return to caves. We conclude that Meta spiders have potential as model organisms for studies on behavioural adaptations and flexibility.

Interplay between Peptidoglycan Biology and Virulence in Gram-Negative Pathogens

The clinical and epidemiological threat of the growing antimicrobial resistance in Gram-negative pathogens, particularly for β-lactams, the most frequently used and relevant antibiotics, urges research to find new therapeutic weapons to combat the infections caused by these microorganisms. An essential previous step in the development of these therapeutic solutions is to identify their potential targets in the biology of the pathogen. This is precisely what we sought to do in this review specifically regarding the barely exploited field analyzing the interplay among the biology of the peptidoglycan and related processes, such as β-lactamase regulation and virulence. Hence, here we gather, analyze, and integrate the knowledge derived from published works that provide information on the topic, starting with those dealing with the historically neglected essential role of the Gram-negative peptidoglycan in virulence, including structural, biogenesis, remodeling, and recycling aspects, in addition to proinflammatory and other interactions with the host. We also review the complex link between intrinsic β-lactamase production and peptidoglycan metabolism, as well as the biological costs potentially associated with the expression of horizontally acquired β-lactamases. Finally, we analyze the existing evidence from multiple perspectives to provide useful clues for identifying targets enabling the future development of therapeutic options attacking the peptidoglycan-virulence interconnection as a key weak point of the Gram-negative pathogens to be used, if not to kill the bacteria, to mitigate their capacity to produce severe infections.

Species delimitation and mitogenome phylogenetics in the subterranean genus Pseudoniphargus (Crustacea: Amphipoda)

The amphi-Atlantic distributions exhibited by many thalassoid stygobiont (obligate subterranean) crustaceans have been explained by fragmentation by plate tectonics of ancestral shallow water marine populations. The amphipod stygobiont genus Pseudoniphargus is distributed across the Mediterranean region but also in the North Atlantic archipelagos of Bermuda, Azores, Madeira and the Canaries. We used species delimitation methods and mitogenome phylogenetic analyses to clarify the species diversity and evolutionary relationships within the genus and timing their diversification. Analyses included samples from the Iberian Peninsula, northern Morocco, the Balearic, Canarian, Azores and Madeira archipelagoes plus Bermuda. In most instances, morphological and molecular-based species delimitation analyses yielded consistent results. Notwithstanding, in a few cases either incipient speciation with no involvement of detectable morphological divergence or species crypticism were the most plausible explanations for the disagreement found between morphological and molecular species delimitations. Phylogenetic analyses based on a robust calibrated mitochondrial tree suggested that Pseudoniphargus lineages have a younger age than for other thalassoid amphipods displaying a disjunct distribution embracing both sides of the Atlantic Ocean. A major split within the family was estimated to occur at the Paleocene, when a lineage from Northern Iberian Peninsula diverged from the rest of pseudoniphargids. Species diversification in the peri-Mediterranean area was deduced to occur in early Miocene to Tortonian times, while in the Atlantic islands it started in the Pliocene. Our results show that the current distribution pattern of Pseudoniphargus resulted from a complex admix of relatively ancient vicariance events and several episodes of long- distance dispersal.

Diversity and regulation of intrinsic β-lactamases from non-fermenting and other Gram-negative opportunistic pathogens

This review deeply addresses for the first time the diversity, regulation and mechanisms leading to mutational overexpression of intrinsic β-lactamases from non-fermenting and other non-Enterobacteriaceae Gram-negative opportunistic pathogens. After a general overview of the intrinsic β-lactamases described so far in these microorganisms, including circa. 60 species and 100 different enzymes, we review the wide array of regulatory pathways of these β-lactamases. They include diverse LysR-type regulators, which control the expression of β-lactamases from relevant nosocomial pathogens such as Pseudomonas aeruginosa or Stenothrophomonas maltophilia or two-component regulators, with special relevance in Aeromonas spp., along with other pathways. Likewise, the multiple mutational mechanisms leading to β-lactamase overexpression and β-lactam resistance development, including AmpD (N-acetyl-muramyl-L-alanine amidase), DacB (PBP4), MrcA (PPBP1A) and other PBPs, BlrAB (two-component regulator) or several lytic transglycosylases among others, are also described. Moreover, we address the growing evidence of a major interplay between β-lactamase regulation, peptidoglycan metabolism and virulence. Finally, we analyse recent works showing that blocking of peptidoglycan recycling (such as inhibition of NagZ or AmpG) might be useful to prevent and revert β-lactam resistance. Altogether, the provided information and the identified gaps should be valuable for guiding future strategies for combating multidrug-resistant Gram-negative pathogens.

Molecular systematics of Haploginglymus, a genus of subterranean amphipods endemic to the Iberian Peninsula (Amphipoda: Niphargidae)

The molecular systematics of the subterranean amphipod genus Haploginglymus is addressed through the phylogenetic analysis of three DNA gene fragments (nuclear ribosomal 28S and protein- coding Histone 3, plus mitochondrial Cytochrome c Oxidase subunit I). We take advantage of the description of a new species from southern Spain (Haploginglymus geos sp. nov.) to assess the singularity of this genus endemic to the Iberian Peninsula and the inclusion of the morphologically aberrant H. morenoi within Haploginglymus. Our results corroborate the monophyly of the family Niphargidae but shows Niphargus to be paraphyletic as it currently stands, with Haploginglymus appearing nested within it. A strongly supported sister-group relationship between niphargids and the (thalassoid) pseudoniphargids is recovered as well, but we propose the Niphargidae should continue to be considered as a primary limnic group for biogeographic purposes despite its presumed marine derivation. Our findings are in agreement with previous studies that suggest the family Niphargidae originated in the late Cretaceous in the NE Atlantic, from where it eventually expanded across continental Europe.

Sensing Mg2+ contributes to the resistance of Pseudomonas aeruginosa to complement-mediated opsonophagocytosis

Pseudomonas aeruginosa adaptation to survive in the host hinges on its ability to probe the environment and respond appropriately. Rapid adaptation is often mediated by two-component regulatory systems, such as the PhoP/PhoQ system that responds to Mg²⁺ ion concentration. However, there is limited information about the role of PhoQ in P. aeruginosa bloodstream infections. We used a murine model of systemic infection to test the virulence of a PhoQ-deficient mutant. Mutation of PhoQ impaired the virulence and the ability to cause bacteremia of P. aeruginosa. In the presence of blood concentrations of Mg²⁺ , a PhoQ mutant bound more C3 and was more susceptible to complement-mediated opsonophagocytosis than the parent strain, suggesting a direct effect of the Mg²⁺ on the modulation of expression of a bacterial component controlled by the PhoP/PhoQ system. Ligand blot analysis, C3 binding experiments and opsonophagocytosis assays identified this component as the outer membrane protein OprH, expression of which impaired the virulence of P. aeruginosa in a murine model of systemic infection. We demonstrate that expression of PhoQ is essential to detect Mg²⁺ and reduce the expression of OprH, a previously unrecognized C3 binding molecule that promotes the opsonophagocytosis of P. aeruginosa.

Phylogenetic evidence that both ancient vicariance and dispersal have contributed to the biogeographic patterns of anchialine cave shrimps

Cave shrimps from the genera Typhlatya, Stygiocaris and Typhlopatsa (Atyidae) are restricted to specialised coastal subterranean habitats or nearby freshwaters and have a highly disconnected distribution (Eastern Pacific, Caribbean, Atlantic, Mediterranean, Madagascar, Australia). The combination of a wide distribution and a limited dispersal potential suggests a large-scale process has generated this geographic pattern. Tectonic plates that fragment ancestral ranges (vicariance) has often been assumed to cause this process, with the biota as passive passengers on continental blocks. The ancestors of these cave shrimps are believed to have inhabited the ancient Tethys Sea, with three particular geological events hypothesised to have led to their isolation and divergence; (1) the opening of the Atlantic Ocean, (2) the breakup of Gondwana, and (3) the closure of the Tethys Seaway. We test the relative contribution of vicariance and dispersal in the evolutionary history of this group using mitochondrial genomes to reconstruct phylogenetic and biogeographic scenarios with fossil-based calibrations. Given that the Australia/Madagascar shrimp divergence postdates the Gondwanan breakup, our results suggest both vicariance (the Atlantic opening) and dispersal. The Tethys closure appears not to have been influential, however we hypothesise that changing marine currents had an important early influence on their biogeography.

Host and Pathogen Biomarkers for Severe Pseudomonas aeruginosa Infections

Pseudomonas aeruginosa is among the leading causes of severe nosocomial infections, particularly affecting critically ill and immunocompromised patients. Here we review the current knowledge on the factors underlying the outcome of P. aeruginosa nosocomial infections, including aspects related to the pathogen, the host, and treatment. Intestinal colonization and previous use of antibiotics are key risk factors for P. aeruginosa infections, whereas underlying disease, source of infection, and severity of acute presentation are key host factors modulating outcome; delayed adequate antimicrobial therapy is also independently associated with increased mortality. Among pathogen-related factors influencing the outcome of P. aeruginosa infections, antibiotic resistance, and particularly multidrug-resistant profiles, is certainly of paramount relevance, given its obvious effect on the chances of appropriate empirical therapy. However, the direct impact of antibiotic resistance in the severity and outcomes of P. aeruginosa infections is not yet well established. The interplay between antibiotic resistance, virulence, and the concerning international high-risk clones (such as ST111, ST175, and ST235) still needs to be further analyzed. On the other hand, differential presence or expression of virulence factors has been shown to significantly impact disease severity and mortality. The likely more deeply studied P. aeruginosa virulence determinant is the type III secretion system (T3SS); the production of T3SS cytotoxins, and particularly ExoU, has been well established to determine a worse outcome both in respiratory and bloodstream infections. Other relevant pathogen-related biomarkers of severe infections include the involvement of specific clones or O-antigen serotypes, the presence of certain horizontally acquired genomic islands, or the expression of other virulence traits, such as the elastase. Finally, recent data suggest that host genetic factors may also modulate the severity of P. aeruginosa infections.

Multi-mycotoxin determination in barley and derived products from Tunisia and estimation of their dietary intake

A study on raw barley and derived products (barley soup and beers) was carried out to determine the natural presence of twenty-four mycotoxins by both liquid chromatography and gas chromatography coupled to tandem mass spectrometry (MS/MS). The developed multi-mycotoxin procedure was based on both SLE and QuEChERS extraction steps. 66% of analyzed samples presented mycotoxin contamination and only one sample, which was soup of barley (6 ng/g), exceeded the maximum level (ML) established by EU for OTA (5 ng/g). Raw barley was the most contaminated matrix (62%), which concentrations ranged from 1.70 to 287.13 ng/g) and type of detected mycotoxins (DON, 15AcDON, NEO, NIV, HT2, FB1, OTA, ENA, ENA1, ENB and ENB1). DON was the most detected mycotoxin with an incidence of 56%, 29% and 23% in beer, soup of barley and barley, respectively. However, the highest levels detected were for ENA, in raw barley with 287 ng/g. In beer and soup of barley samples, the mycotoxins with highest level were 15AcDON (15.6 ng/g) and ENB1 (55.1 ng/g), respectively. Furthermore, 80% of positive soup of barley samples showed co-occurrence. No toxicological concern was associated to mycotoxins exposure for consumers.

Understanding the acute inflammatory response to Pseudomonas aeruginosa infection: differences between susceptible and multidrug-resistant strains in a mouse peritonitis model

The increasing emergence of multidrug-resistant (MDR) Pseudomonas aeruginosa strains is associated with the spread of a few international epidemic clones called high-risk clones. The existence of a fitness cost associated with multidrug resistance remains unclear, and little is known about the host inflammatory response in acute P. aeruginosa infections. This study aimed to investigate how the inflammatory response occurs in the most relevant high-risk clones and to compare the process with that recorded in clinical susceptible isolates. Nine P. aeruginosa strains were studied, including the most relevant MDR high-risk clones (ST111, ST175 and ST235) circulating worldwide. The inflammatory response in terms of the release of interleukins in serum was investigated in a mouse peritonitis-sepsis model at three time points (4, 8 and 12 h). TNFα and interleukin-10 (IL-10) levels were significantly higher at all time points in mice inoculated with clinical susceptible strains compared with those inoculated with MDR strains. IL-6 levels were significantly higher in the clinical susceptible strain group at 8 h and 12 h (P = 0.036 and P = 0.007, respectively). Bacterial counts (log CFU/mL) in peritoneal fluid were higher in the clinical susceptible strain group compared with the MDR strain group at 8 h [6.00 (4.30-6.90) vs. 4.46 (3.30-5.34); P = 0.005] and 12 h [7.75 (4.00-7.97) vs. 4.04 (2.58-4.94); P = 0.003]. MDR P. aeruginosa strains elicited a weaker inflammatory response than susceptible strains in an experimental mouse model, suggesting the existence of a fitness cost associated with multidrug resistance.

The mitogenome of the amphipod Hyalella lucifugax (Crustacea) and its phylogenetic placement

The mitogenome of Hyalella lucifugax from Lake Titicaca, obtained using Illumina NGS technology, is described. The mitogenome attains 14,994 bp (although the control region could not be completed) and comprises the standard set of 2 rRNAs, 13 protein-coding genes, and 22 tRNA genes, plus two non-coding regions. A phylogenetic analysis based on the protein-coding mitochondrial genes from representatives from all amphipod genera with available sequences in GenBank recovers the monophyly of H. lucifugax with the superfamily Talitroidea.

The complete mitochondrial genome of the cave shrimp Typhlatya miravetensis (Decapoda, Atyidae) and its systematic position

The complete mitochondrial genome of Typhlatya miravetensis from one of its only three known localities (Ullal de la Rabla de Miravet, Castellón, Spain) is presented here. The mitogenome is 15,865 bp in length and includes the standard set of two rRNAs, two non-coding regions plus 13 protein-coding genes. The later have been used to perform a phylogenetic analysis together with other Caridea representatives with mitogenome data in GenBank, inferring a close relationship with the Hawaiian volcano shirmp (Halocaridina rubra) within the family Atyidae.

Impact of multidrug resistance on the pathogenicity of Pseudomonas aeruginosa: in vitro and in vivo studies

The biological cost of multidrug resistance in Pseudomonas aeruginosa (PA) remains unclear. This study aimed to evaluate the relationship between pathogenicity and the resistance profile of different PA strains, including the most common epidemic high-risk clones. Nine PA strains were studied, including two reference strains, PAO1 and PA14 [both susceptible to all antipseudomonals (multiS)], and seven clinical strains comprising three clinical multiS strains, a non-clonal multidrug-resistant (MDR) strain and the high-risk MDR clones ST111, ST235 and ST175. In vitro studies were performed to investigate growth rate, type III secretion system (TTSS) genotype, cytotoxicity and invasiveness. Additionally, a peritonitis/sepsis model was used in C57BL/6 mice. The in vitro bacterial duplication time was shorter in clinical multiS strains than in MDR-PA (0.42±0.08h vs. 0.55±0.14h; P=0.023). Among the clinical strains, exoU(+) genotype was observed only in the epidemic clone ST235. In the animal model, the probability of mortality at 48h was 70% for clinical multiS strains vs. 7.5% for clinical MDR-PA (P<0.001, log-rank). The high-risk clone ST235 was the only MDR strain that was able to cause mortality. Bacterial concentrations in peritoneal fluid were higher in mice inoculated with multiS strains compared with MDR-PA [log CFU/mL, 8.95 (IQR 3.42-9.32) vs. 1.98 (IQR 1.08-2.80); P<0.001]. These data indicate that MDR profiles are associated with a reduction in virulence of PA in a murine model. Further studies are needed to elucidate the clinical implications of these results.

Mitochondrial genome rearrangements at low taxonomic levels: three distinct mitogenome gene orders in the genus Pseudoniphargus (Crustacea: Amphipoda)

A comparison of mitochondrial genomes of three species of the amphipod Pseudoniphargus revealed the occurrence of a surprisingly high level of gene rearrangement involving protein-coding genes that is a rare phenomenon at low taxonomic levels. The three Pseudoniphargus mitogenomes also display a unique gene arrangement with respect to either the presumed Pancrustacean order or those known for other amphipods. Relative long non-coding sequences appear adjacent to the putative breakage points involved in gene rearrangements of protein coding genes. Other details of the newly obtained mitochondrial genomes - e.g., gene content, nucleotide composition and codon usage - are similar to those found in the mitogenomes of other amphipod species studied. They all contain the typical mitochondrial genome set consisting of 13 protein-coding genes, 22 tRNAs, and two rRNAS, as well as a large control region. The secondary structures and characteristics of tRNA and ribosomal mitochondrial genes of these three species are also discussed.

The increasing threat of Pseudomonas aeruginosa high-risk clones

The increasing prevalence of chronic and hospital-acquired infections produced by multidrug-resistant (MDR) or extensively drug-resistant (XDR) Pseudomonas aeruginosa strains is associated with significant morbidity and mortality. This growing threat results from the extraordinary capacity of this pathogen for developing resistance through chromosomal mutations and from the increasing prevalence of transferable resistance determinants, particularly those encoding carbapenemases or extended-spectrum β-lactamases (ESBLs). P. aeruginosa has a nonclonal epidemic population structure, composed of a limited number of widespread clones which are selected from a background of a large quantity of rare and unrelated genotypes that are recombining at high frequency. Indeed, recent concerning reports have provided evidence of the existence of MDR/XDR global clones, denominated high-risk clones, disseminated in hospitals worldwide; ST235, ST111, and ST175 are likely those more widespread. Noteworthy, the vast majority of infections by MDR, and specially XDR, strains are produced by these and few other clones worldwide. Moreover, the association of high-risk clones, particularly ST235, with transferable resistance is overwhelming; nearly 100 different horizontally-acquired resistance elements and up to 39 different acquired β-lactamases have been reported so far among ST235 isolates. Likewise, MDR internationally-disseminated epidemic strains, such as the Liverpool Epidemic Strain (LES, ST146), have been noted as well among cystic fibrosis patients. Here we review the population structure, epidemiology, antimicrobial resistance mechanisms and virulence of the P. aeruginosa high-risk clones. The phenotypic and genetic factors potentially driving the success of high-risk clones, the aspects related to their detection in the clinical microbiology laboratory and the implications for infection control and public health are also discussed.