62 results found
Saromi K, England P, Tang W, et al., 2020, Rapid glycosyl-inositol-phospho-ceramide fingerprint from filamentous fungal pathogens using the MALDI Biotyper Sirius system., Rapid Commun Mass Spectrom, Vol: 34
RATIONALE: Glycosyl-inositol-phospho-ceramides (GIPCs) or glycosylphosphatidylinositol-anchored fungal polysaccharides are known to be major lipids in plant and fungal plasma membranes and to play an important role in stress adaption. However, their analysis remains challenging due to the several steps involved for their extractions and purifications prior to mass spectrometric analysis. To address this challenge, we developed a rapid and sensitive method to identify GIPCs from the four common fungal plant pathogens Botrytis cinerea, Fusarium graminearium, Neurospora crassa and Ustilago maydis. METHODS: Fungal plant pathogens were cultured, harvested, heat-inactivated and washed three times with double-distilled water. Intact fungi were deposited on a matrix-assisted laser desorption ionization (MALDI) target plate, mixed with the matrix consisting of a 9:1 mixture of 2,5-dihydroxybenzoic acid and 2-hydroxy-5-methoxybenzoic acid solubilized at 10 mg/mL in chloroform-methanol (9:1 v/v) and analyzed using a Bruker MALDI Biotyper Sirius system in the linear negative ion mode. Mass spectra were acquired from m/z 700 to 2000. RESULTS: MALDI time-of-flight (TOF) mass spectrometric analysis of cultured fungi showed clear signature of GIPCs in B. cinerea, F. graminearium, N. crassa and U. maydis. CONCLUSIONS: We have demonstrated that routine MALDI-TOF in the linear negative ion mode combined with an apolar solvent system to solubilize the matrix is applicable to the detection of filamentous fungal GIPCs.
Gonzalo X, Broda A, Drobniewski F, et al., 2020, Performance of lipid fingerprint-based MALDI-ToF for the diagnosis of mycobacterial infections, Clinical Microbiology and Infection, ISSN: 1198-743X
ObjectivesBacterial diagnosis of mycobacteria is often challenging because of the variability of the sensitivity and specificity of the assay used, and it can be expensive to perform accurately. Although matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) has become the workhorse of clinical laboratories, the current MALDI methodology (which is based on cytosolic protein profiling) for mycobacteria is still challenging due to the number of steps involved (up to seven) and potential biosafety concerns. Knowing that mycobacteria produce surface-exposed species-specific lipids, we here hypothesized that the detection of those molecules could offer a rapid, reproducible and robust method for mycobacterial identification.MethodsWe evaluated the performance of an alternative methodology based on characterized species-specific lipid profiling of intact bacteria, without any sample preparation, by MALDI MS; it uses MALDI-time-of-flight (ToF) MS combined with a specific matrix (super-2,5-dihydroxybenzoic acid solubilized in an apolar solvent system) to analyse lipids of intact heat-inactivated mycobacteria. Cultured mycobacteria are heat-inactivated and loaded directly onto the MALDI target followed by addition of the matrix. Acquisition of the data is done in both positive and negative ion modes. Blinded studies were performed using 273 mycobacterial strains comprising both the Mycobacterium tuberculosis (Mtb) complex and non-tuberculous mycobacteria (NTMs) subcultured in Middlebrook 7H9 media supplemented with 10% OADC (oleic acid/dextrose/catalase) growth supplement and incubated for up to 2 weeks at 37°C.ResultsThe method we have developed is fast (<10 mins) and highly sensitive (<1000 bacteria required); 96.7% of the Mtb complex strains (204/211) were correctly assigned as MTB complex and 91.7% (22/24) NTM species were correctly assigned based only on intact bacteria species-specific lipid profiling by MALDI-ToF MS.ConclusionsIntact bacter
Yi L, Rebollo-Ramirez S, Larrouy-Maumus G, 2020, Metabolomics reveals that the cAMP receptor protein regulates nitrogen and peptidoglycan synthesis in Mycobacterium tuberculosis, RSC Advances: an international journal to further the chemical sciences, Vol: 10, Pages: 26212-26219, ISSN: 2046-2069
Mycobacterium tuberculosis requires extensive sensing and response to environment for its successful survival and pathogenesis, and signalling by cyclic adenosine 3′,5′-monophosphate (cAMP) is an important mechanism. cAMP regulates expression of target genes via interaction with downstream proteins, one of which is cAMP receptor protein (CRP), a global transcriptional regulator. Previous genomic works had identified regulon of CRP and investigated transcriptional changes in crp deletion mutant, however a link to downstream metabolomic events were lacking, which would help better understand roles of CRP. This work aims at investigating changes at metabolome level in M. tuberculosis crp deletion mutant combining untargeted LC-MS analysis and 13C isotope tracing analysis. The results were compared with previously published RNA sequencing data. We identified increasing abundances of metabolites related to nitrogen metabolism including ornithine, citrulline and glutamate derivatives, while 13C isotope labelling analysis further showed changes in turnover of these metabolites and amino acids, suggesting regulatory roles of CRP in nitrogen metabolism. Upregulation of diaminopimelic acid and its related genes also suggested role of CRP in regulation of peptidoglycan synthesis. This study provides insights on metabolomic aspects of cAMP-CRP regulatory pathway in M. tuberculosis and links to previously published transcriptomic data drawing a more complete map.
Larrouy-Maumus G, Dortet L, Filloux A, et al., 2020, Detection of colistin resistance in Salmonella enterica using MALDIxin test on the routine MALDI Biotyper Sirius mass spectrometer, Frontiers in Microbiology, Vol: 11, Pages: 1-6, ISSN: 1664-302X
Resistance to polymyxins in most Gram-negative bacteria arises from chemical modifications to the lipid A portion of their lipopolysaccharide (LPS) mediated by chromosomally-encoded mutations or the recently discovered plasmid-encoded mcr genes that have further complicated the landscape of colistin resistance. Currently, minimal inhibitory concentration (MIC) determination by broth microdilution, the gold standard for the detection of polymyxin resistance, is time consuming (24 hours) and challenging to perform in clinical and veterinatryveterinary laboratories. Here we present the use of the MALDIxin to detect colistin resistant Salmonella enterica using the MALDxin test on the routine matrix-assisted laser desorption ionization (MALDI) Biotyper Sirius system.
Giraud-Gatineau A, Coya JM, Maure A, et al., 2020, The antibiotic bedaquiline activates host macrophage innate immune resistance to bacterial infection, eLife, Vol: 9, ISSN: 2050-084X
Antibiotics are widely used in the treatment of bacterial infections. Although known for their microbicidal activity, antibiotics may also interfere with the host's immune system. Here, we analyzed the effects of bedaquiline (BDQ), an inhibitor of the mycobacterial ATP synthase, on human macrophages. Genome-wide gene expression analysis revealed that BDQ reprogramed cells into potent bactericidal phagocytes. We found that 579 and 1,495 genes were respectively differentially expressed in naive- and M. tuberculosis-infected macrophages incubated with the drug, with an over-representation of lysosome-associated genes. BDQ treatment triggered a variety of antimicrobial defense mechanisms, including phagosome-lysosome fusion, and autophagy. These effects were associated with activation of transcription factor EB, involved in the transcription of lysosomal genes, resulting in enhanced intracellular killing of different bacterial species that were naturally insensitive to BDQ. Thus, BDQ could be used as a host-directed therapy against a wide range of bacterial infections.
Furniss RCD, Kostrzewa M, Mavridou DAI, et al., 2020, The clue is in the lipid A: Rapid detection of colistin resistance, PLoS Pathogens, Vol: 16, ISSN: 1553-7366
Larrouy-Maumus G, Shahrezaei V, tang W, et al., 2020, Discrimination of bovine milk from non-dairy milk by lipids fingerprinting using routine matrix-assisted laser desorption ionization mass spectrometry, Scientific Reports, Vol: 10, ISSN: 2045-2322
An important sustainable development goal for any country is to ensure food security by producing a sufficient and safe food supply. This is the case for bovine milk where addition of non-dairy milks such as vegetables (e.g., soya or coconut) has become a common source of adulteration and fraud. Conventionally, gas chromatography techniques are used to detect key lipids (e.g., triacylglycerols) has an effective read-out of assessing milks origins and to detect foreign milks in bovine milks. However, such approach requires several sample preparation steps and a dedicated laboratory environment, precluding a high throughput process. To cope with this need, here, we aimed to develop a novel and simple method without organic solvent extractions for the detection of bovine and non-dairy milks based on lipids fingerprint by routine MALDI-TOF mass spectrometry (MS). The optimized method relies on the simple dilution of milks in water followed by MALDI-TOF MS analyses in the positive linear ion mode and using a matrix consisting of a 9:1 mixture of 2,5-dihydroxybenzoic acid and 2-hydroxy-5-methoxybenzoic acid (super-DHB) solubilized at 10 mg/mL in 70% ethanol. This sensitive, inexpensive, and rapid method has potential for use in food authenticity applications.
Otter J, Brophy K, Palmer J, et al., 2020, Smart surfaces to tackle infection and antimicrobial resistance, Briefing Paper
Bottai D, Frigui W, Sayes F, et al., 2020, TbD1 deletion as a driver of the evolutionary success of modern epidemic Mycobacterium tuberculosis lineages, NATURE COMMUNICATIONS, Vol: 11, ISSN: 2041-1723
Hamilton C, Larrouy-Maumus G, Anand P, 2020, Phosphatidylinositol Acyl Chains Configure TLR-Dependent Priming and Activation of the NLRP3 Inflammasome, Publisher: bioRxiv
Abstract Lipids are important in establishing cellular homeostasis by conducting varied functions including relay of extracellular signals. Imbalance in lipid homeostasis results in metabolic diseases, and is tightly connected to discrepancies in immune signalling. The phosphorylation status of the lipid second messenger phosphatidylinositol phosphates is implicated in key physiological functions and pathologies. By contrast, little is known as to how phosphatidylinositol (PI) lipid acyl chains contribute to cellular processes. Here, by employing a mass-spectrometry-based method, we show a role for PI acyl group chains in regulating NLRP3 inflammasome activation in cells lacking ABC transporter ABCB1. In response to canonical stimuli, Abcb1 -/- cells revealed defective priming and activation of the NLRP3 inflammasome owing to blunted TLR-dependent signalling. Cellular lipidomics demonstrated that ABC transporter deficiency shifted the total PI balance such that Abcb1 -/- cells exhibited reduced ratio of the short-chain to long-chain acyl chain lipids. Changes in PI acyl chain configuration accompanied diminished levels of ganglioside GM1, a marker of cholesterol-rich membrane microdomains, in deficient cells. Strikingly, this was not due to differences in the expression of enzymes that either synthesize PI or are involved in acyl chain remodelling. Our study thus suggests an important role for PI lipid chains in priming and activation of the NLRP3 inflammasome thereby highlighting the metabolic regulation of immune responses.
Dortet L, Broda A, bernabeu S, et al., 2020, Optimization of the MALDIxin test for the rapid identification of colistin resistance in Klebsiella pneumoniae using MALDI-TOF-MS, Journal of Antimicrobial Chemotherapy, Vol: 75, Pages: 110-116, ISSN: 0305-7453
Background. With the dissemination of carbapenemase producers, a revival of colistin was observed for the treatment of infections caused by multidrug-resistant Gram-negatives. Unfortunately, the increasing usage of colistin led to the emergence of resistance. In Klebsiella pneumoniae, colistin resistance arises through addition of L-arabinose-4N (L-Ara4N) or phosphoethanolamine (pEtN) on the native lipid A. The underlying mechanisms involve numerous chromosome-encoded genes or the plasmid-encoded phosphoethanolamine transferase MCR. Currently, detection of colistin resistance is time consuming since it still relies on MIC determination by broth microdilution. Recently, a rapid diagnostic test based on MALDI-TOF detection of modified lipid A was developed (the MALDIxin test) and tested on Escherichia coli and Acinetobacter baumannii.Objectives. Optimize the MALDIxin test for the rapid detection of colistin resistance in Klebsiella pneumoniae.Methods. This optimization consists on an additional mild-acid hydrolysis of 15 min in 1% acetic acid. The optimized method was tested on a collection of 81 clinical K. pneumoniae isolates including 49 colistin resistant strains among which 45 correspond to chromosome-encoded resistance, 3 MCR-related resistance and one isolate harbouring both mechanisms.Results. The optimized method allowed the rapid (< 30 min) identification of L-Ara4N and pEtN modified lipid A of K. pneumoniae which are known to be the real triggers of polymyxin resistance. In the same time, it discriminates between chromosome-encoded and MCR-related polymyxin resistance.Conclusions. The MALDIxin test has the potential to become an accurate tool for the rapid diagnostic of colistin resistance in clinically-relevant Gram negative bacteria.
Furniss C, Dortet L, Bolland W, et al., 2019, Detection of colistin resistance in Escherichia coli using the MALDI Biotyper Sirius mass spectrometry system, Journal of Clinical Microbiology, Vol: 57, Pages: 1-7, ISSN: 0095-1137
Polymyxin antibiotics are a last-line treatment for multidrug-resistant Gram-negative bacteria. However, the emergence of colistin resistance, including the spread of mobile mcr genes, necessitates the development of improved diagnostics for the detection of colistin-resistant organisms in hospital settings. The recently developed MALDIxin test enables detection of colistin resistance by MALDI-TOF mass spectrometry in less than 15 minutes, but is not optimized for the mass spectrometers commonly found in clinical microbiology laboratories. In this study, we adapted the MALDIxin test for the MALDI Biotyper Sirius MALDI-TOF mass spectrometry system (Bruker Daltonics). We optimized the sample preparation protocol using a set of 6 MCR-expressing Escherichia coli clones and validated the assay with a collection of 40 E. coli clinical isolates, including 19 confirmed MCR producers, 12 colistin-resistant isolates which tested negative for commonly encountered mcr genes (i.e. likely chromosomally-resistant isolates) and 9 polymyxin-susceptible isolates. We calculated Polymyxin resistance ratio (PRR) values from the acquired spectra; a PRR value of zero, indicating polymyxin susceptibility, was obtained for all colistin-susceptible E. coli isolates, whereas positive PRR values, indicating resistance to polymyxins, were obtained for all resistant strains independent of the genetic basis of resistance. Thus, we report a preliminary feasibility study showing that an optimized version of the MALDIxin test, adapted for the routine MALDI Biotyper Sirius, provides an unbiased, fast, reliable, cost-effective and high-throughput way of detecting colistin resistance in clinical E. coli isolates.
Potron A, Vuillemenot J-B, Puja H, et al., 2019, ISAba1-dependent overexpression of eptA in clinical strains of Acinetobacter baumannii resistant to colistin, JOURNAL OF ANTIMICROBIAL CHEMOTHERAPY, Vol: 74, Pages: 2544-2550, ISSN: 0305-7453
Tang W, Ranganathan N, Shahrezaei V, et al., 2019, MALDI-TOF mass spectrometry on intact bacteria combined with a refined analysis framework allows accurate classification of MSSA and MRSA., PLoS ONE, Vol: 14, Pages: 1-16, ISSN: 1932-6203
Fast and reliable detection coupled with accurate data-processing and analysis of antibiotic-resistant bacteria is essential in clinical settings. In this study, we use MALDI-TOF on intact cells combined with a refined analysis framework to demonstrate discrimination between methicillin-susceptible (MSSA) and methicillin-resistant (MRSA) Staphylococcus aureus. By combining supervised and unsupervised machine learning methods, we firstly show that the mass spectroscopy data contains strong signal for the clustering of MSSA and MRSA. Then we concentrate on applying supervised learning to extract and verify the important features. A new workflow is proposed that allows for extracting a fixed set of reference peaks so that any new data can be aligned to it and hence consistent feature matrices can be obtained. Also note that by doing so we are able to examine the robustness of the important features that have been found. We also show that appropriate size of the benchmark data, appropriate alignment of the testing data and use of an optimal set of features via feature selection results in prediction accuracy over 90%. In summary, as proof-of-principle, our integrated experimental and bioinformatics study suggests a novel intact cell MALDI-TOF to be of great promise for fast and reliable detection of MRSA strains.
Rebollo-Ramirez S, Larrouy-Maumus G, 2019, NaCl triggers the CRP-dependent increase of cAMP in Mycobacterium tuberculosis, Tuberculosis, Vol: 116, Pages: 8-16, ISSN: 1472-9792
The second messenger 3′,5′-cyclic adenosine monophosphate (3′,5′-cAMP) has been shown to be involved in the regulation of many biological processes ranging from carbon catabolite repression in bacteria to cell signalling in eukaryotes. In mycobacteria, the role of cAMP and the mechanisms utilized by the bacterium to adapt to and resist immune and pharmacological sterilization remain poorly understood. Among the stresses encountered by bacteria, ionic and non-ionic osmotic stresses are among the best studied. However, in mycobacteria, the link between ionic osmotic stress, particularly sodium chloride, and cAMP has been relatively unexplored. Using a targeted metabolic analysis combined with stable isotope tracing, we show that the pathogenic Mycobacterium tuberculosis but not the opportunistic pathogen Mycobacterium marinum nor the non-pathogenic Mycobacterium smegmatis responds to NaCl stress via an increase in intracellular cAMP levels. We further showed that this increase in cAMP is dependent on the cAMP receptor protein and in part on the threonine/serine kinase PnkD, which has previously been associated with the NaCl stress response in mycobacteria.
Larrouy-Maumus GJ, 2019, Lipids as biomarkers of cancer and bacterial infections, Current Medicinal Chemistry, Vol: 26, Pages: 1924-1932, ISSN: 0929-8673
Lipids are ubiquitous molecules, known to play important roles in various cellular processes. Alterations to the lipidome can therefore be used as a read-out of the signs of disease, highlighting the importance to consider lipids as biomarkers in addition of nucleic acid and proteins. This mini-review exposes the current knowledge and limitations of the use of lipids as biomarkers of the top global killers which are cancer and bacterial infections.
Krokowski S, Lobato-Marquez D, Chastanet A, et al., 2018, Septins recognize and entrap dividing bacterial cells for delivery to lysosomes, Cell Host and Microbe, Vol: 24, Pages: 866-874, ISSN: 1931-3128
The cytoskeleton occupies a central role in cellular immunity by promoting bacterial sensing and antibacterial functions. Septins are cytoskeletal proteins implicated in various cellular processes, including cell division. Septins also assemble into cage-like structures that entrap cytosolic Shigella, yet how septins recognize bacteria is poorly understood. Here, we discover that septins are recruited to regions of micron-scale membrane curvature upon invasion and division by a variety of bacterial species. Cardiolipin, a curvature-specific phospholipid, promotes septin recruitment to highly curved membranes of Shigella, and bacterial mutants lacking cardiolipin exhibit less septin cage entrapment. Chemically inhibiting cell separation to prolong membrane curvature or reducing Shigella cell growth respectively increases and decreases septin cage formation. Once formed, septin cages inhibit Shigella cell division upon recruitment of autophagic and lysosomal machinery. Thus, recognition of dividing bacterial cells by the septin cytoskeleton is a powerful mechanism to restrict the proliferation of intracellular bacterial pathogens.
Dortet L, Bonnin RA, Pennisi I, et al., 2018, Rapid detection and discrimination of chromosome-and MCR-plasmid-mediated resistance to polymyxins by MALDI-TOF MS in Escherichia coli: the MALDIxin test, Journal of Antimicrobial Chemotherapy, Vol: 73, Pages: 3359-3367, ISSN: 0305-7453
BackgroundPolymyxins are currently considered a last-resort treatment for infections caused by MDR Gram-negative bacteria. Recently, the emergence of carbapenemase-producing Enterobacteriaceae has accelerated the use of polymyxins in the clinic, resulting in an increase in polymyxin-resistant bacteria. Polymyxin resistance arises through modification of lipid A, such as the addition of phosphoethanolamine (pETN). The underlying mechanisms involve numerous chromosome-encoded genes or, more worryingly, a plasmid-encoded pETN transferase named MCR. Currently, detection of polymyxin resistance is difficult and time consuming.ObjectivesTo develop a rapid diagnostic test that can identify polymyxin resistance and at the same time differentiate between chromosome- and plasmid-encoded resistances.MethodsWe developed a MALDI-TOF MS-based method, named the MALDIxin test, which allows the detection of polymyxin resistance-related modifications to lipid A (i.e. pETN addition), on intact bacteria, in <15 min.ResultsUsing a characterized collection of polymyxin-susceptible and -resistant Escherichia coli, we demonstrated that our method is able to identify polymyxin-resistant isolates in 15 min whilst simultaneously discriminating between chromosome- and plasmid-encoded resistance. We validated the MALDIxin test on different media, using fresh and aged colonies and show that it successfully detects all MCR-1 producers in a blindly analysed set of carbapenemase-producing E. coli strains.ConclusionsThe MALDIxin test is an accurate, rapid, cost-effective and scalable method that represents a major advance in the diagnosis of polymyxin resistance by directly assessing lipid A modifications in intact bacteria.
Sabnis A, Klöckner A, Becce M, et al., 2018, Colistin kills bacteria by targeting lipopolysaccharide in the cytoplasmic membrane, Publisher: Cold Spring Harbor Laboratory
<jats:title>Summary</jats:title><jats:p>Colistin is an antibiotic of last resort for infections caused by drug-resistant Gram-negative pathogens such as <jats:italic>Pseudomonas aeruginosa</jats:italic> and <jats:italic>Escherichia coli</jats:italic>. For this reason, high rates of treatment failure and increasing resistance to this antibiotic are very concerning and attempts to resolve these issues are hampered by a poor understanding of colistin’s mode of action. Whilst it is well established that colistin binds to lipopolysaccharide in the bacterial outer membrane, it was unclear how this led to bacterial killing. Here, we show that colistin also targets lipopolysaccharide in the cytoplasmic membrane and that this interaction is essential for cytoplasmic membrane permeabilisation, cell lysis and the bactericidal activity of the antibiotic. We also found that MCR-1-mediated colistin resistance confers protection against the antibiotic via the presence of modified lipopolysaccharide within the cytoplasmic membrane, rather than the outer membrane. These findings reveal key details about the mechanism by which colistin kills bacteria, providing the foundations for the development of new approaches to enhance therapeutic outcomes.</jats:p>
Decout A, Silva-Gomes S, Drocourt D, et al., 2018, Deciphering the molecular basis of mycobacteria and lipoglycan recognition by the C-type lectin Dectin-2, Scientific Reports, Vol: 8, ISSN: 2045-2322
Dectin-2 is a C-type lectin involved in the recognition of several pathogens such as Aspergillus fumigatus, Candida albicans, Schistosoma mansonii, and Mycobacterium tuberculosis that triggers Th17 immune responses. Identifying pathogen ligands and understanding the molecular basis of their recognition is one of the current challenges. Purified M. tuberculosis mannose-capped lipoarabinomannan (ManLAM) was shown to induce signaling via Dectin-2, an activity that requires the (α1 → 2)-linked mannosides forming the caps. Here, using isogenic M. tuberculosis mutant strains, we demonstrate that ManLAM is a bona fide and actually the sole ligand mediating bacilli recognition by Dectin-2, although M. tuberculosis produces a variety of cell envelope mannoconjugates, such as phosphatidyl-myo-inositol hexamannosides, lipomannan or manno(lipo)proteins, that bear (α1 → 2)-linked mannosides. In addition, we found that Dectin-2 can recognize lipoglycans from other bacterial species, such as Saccharotrix aerocolonigenes or the human opportunistic pathogen Tsukamurella paurometabola, suggesting that lipoglycans are prototypical Dectin-2 ligands. Finally, from a structure/function relationship perspective, we show, using lipoglycan variants and synthetic mannodendrimers, that dimannoside caps and multivalent interaction are required for ligand binding to and signaling via Dectin-2. Better understanding of the molecular basis of ligand recognition by Dectin-2 will pave the way for the rational design of potent adjuvants targeting this receptor.
Dortet L, Potron A, Bonnin RA, et al., 2018, Rapid detection of colistin resistance in Acinetobacter baumannii using MALDI-TOF-based lipidomics on intact bacteria, Scientific Reports, Vol: 8, ISSN: 2045-2322
With the dissemination of extremely drug resistant bacteria, colistin is now considered as the last-resort therapy for the treatment of infection caused by Gram-negative bacilli (including carbapenemase producers). Unfortunately, the increase use of colistin has resulted in the emergence of resistance as well. In A. baumannii, colistin resistance is mostly caused by the addition of phosphoethanolamine to the lipid A through the action of a phosphoethanolamine transferase chromosomally-encoded by the pmrC gene, which is regulated by the two-component system PmrA/PmrB. In A. baumannii clinical isolate the main resistance mechanism to colistin involves mutations in pmrA, pmrB or pmrC genes leading to the overexpression of pmrC. Although, rapid detection of resistance is one of the key issues to improve the treatment of infected patient, detection of colistin resistance in A. baumannii still relies on MIC determination through microdilution, which is time-consuming (16–24 h). Here, we evaluated the performance of a recently described MALDI-TOF-based assay, the MALDIxin test, which allows the rapid detection of colistin resistance-related modifications to lipid A (i.e phosphoethanolamine addition). This test accurately detected all colistin-resistant A. baumannii isolates in less than 15 minutes, directly on intact bacteria with a very limited sample preparation prior MALDI-TOF analysis.
Filloux A, Larrouy-Maumus G, Dortet L, 2018, Method of detection: Use of Lipid A and its modifications as a direct detection of antimicrobials resistance, WO2018158573
The present invention is directed to a method for detecting the presence or absence of a bacterium resistant to a cyclic cationic polypeptide antibiotic, comprising: (a) subjecting a test sample to mass spectrometry analysis and generating a mass spectrum output; wherein said test sample comprises a bacterial membrane or a fragment thereof, wherein the fragment comprises a non- Lipid A component; (b) identifying in said mass spectrum output a first defined peak indicative of the presence of Lipid A modified by phosphoethanolamine, wherein said first defined peak is a peak present in a mass spectrum output for Lipid A modified by phosphoethanolamine and wherein said first defined peak is absent from a corresponding mass spectrum output for native Lipid A; and (c) wherein the presence of said first defined peak indicates the presence of a bacterium resistant to a cyclic cationic polypeptide antibiotic, and wherein the absence of said first defined peak indicates the absence of a bacterium resistant to a cyclic cationic polypeptide antibiotic. This method is also used in a screening method to identify an inhibitor of cyclic cationic polypeptide antibiotic resistance in a bacterium. The matrix solution can contain 2,5-dihydroxybenzoic acid and aids in the selective extraction, co-crystallisation and ionisation of native Lipid A and/or modified Lipid A as an integral part of a bacterial membrane.
Larrouy-Maumus GJ, Mostowy S, Lobato-Márquez D, et al., 2018, Intact cell lipidomics reveal changes to the ratio of cardiolipins to phosphatidylinositols in response to kanamycin in HeLa and primary cells, Chemical Research in Toxicology, Vol: 31, Pages: 688-696, ISSN: 0893-228X
Antimicrobial resistance is a major threat the world is currently facing. Development of new antibiotics and the assessment of their toxicity represent important challenges. Current methods for addressing antibiotic toxicity rely on measuring mitochondrial damage using ATP and/or membrane potential as a readout. In this study, we propose an alternative readout looking at changes in the lipidome on intact and unprocessed cells by matrix-assisted laser desorption ionization mass spectrometry. As a proof of principle, we evaluated the impact of known antibiotics (levofloxacin, ethambutol, and kanamycin) on the lipidome of HeLa cells and mouse bone marrow-derived macrophages. Our methodology revealed that clinically relevant concentrations of kanamycin alter the ratio of cardiolipins to phosphatidylinositols. Unexpectedly, only kanamycin had this effect even though all antibiotics used in this study led to a decrease in the maximal mitochondrial respiratory capacity. Altogether, we report that intact cell-targeted lipidomics can be used as a qualitative method to rapidly assess the toxicity of aminoglycosides in HeLa and primary cells. Moreover, these results demonstrate there is no direct correlation between the ratio of cardiolipins to phosphatidylinositols and the maximal mitochondrial respiratory capacity.
Rebollo-Ramirez S, Thomson M, Larrouy-Maumus G, 2018, The cyclic AMP receptor protein (CRP) orchestrates the increase in intracellular levels of cAMP in response to osmotic stress in pathogenic mycobacteria, Publisher: WILEY, Pages: 96-96, ISSN: 2211-5463
Rycroft J, Gollan B, Grabe G, et al., 2018, Activity of acetyltransferase toxins involved in persister formation of Salmonella during macrophage infection, Nature Communications, Vol: 9, ISSN: 2041-1723
Non-typhoidal Salmonella strains are responsible for invasive infections associated withhigh mortality and recurrence in sub-Saharan Africa and there is strong evidence for clonalrelapse following antibiotic treatment. Persisters are non-growing bacteria that are thought tobe responsible for the recalcitrance of many infections to antibiotics. Toxin-antitoxin systemsare stress-responsive elements that are important for Salmonella persister formation,specifically during infection. Here we report analysis of persister formation of clinical invasive strains of S. Typhimurium and Enteritidis in human primary macrophages. We show that allthe invasive clinical isolates of both serovars that we tested produce high levels of persisters following internalization by human macrophages. Our genome comparison reveals that S.Enteritidis and S. Typhimurium strains contain three acetyltransferase toxins that we characterize structurally and functionally. We show that all induce the persister state byinhibiting translation through acetylation of aminoacyl-tRNAs. However, they differ in theirpotency and target partially different subsets of aminoacyl-tRNAs, potentially accounting fortheir non-redundant effect.
Grabe GJ, Rycroft JA, Gollan B, et al., 2018, Crystal structure of TacT3 (tRNA acetylating toxin) from Salmonella
Lobato-Marquez D, Krokowski S, Sirianni A, et al., 2018, A requirement for septins and the autophagy receptor p62 in the proliferation of intracellular Shigella, Cytoskeleton, Vol: 76, Pages: 163-172, ISSN: 1949-3584
Shigella flexneri, a Gram‐negative enteroinvasive pathogen, causes inflammatory destruction of the human intestinal epithelium. During infection of epithelial cells, Shigella escape from the phagosome to the cytosol, where they reroute host cell glycolysis to obtain nutrients for proliferation. Septins, a poorly understood component of the cytoskeleton, can entrap cytosolic Shigella targeted to autophagy in cage‐like structures to restrict bacterial proliferation. Although bacterial entrapment by septin caging has been the subject of intense investigation, the role of septins and the autophagy machinery in the proliferation of non‐caged Shigella is mostly unknown. Here, we found that intracellular Shigella fail to efficiently proliferate in SEPT2‐, SEPT7‐ or p62/SQSTM1‐depleted cells. Consistent with a failure to proliferate, single cell analysis of bacteria not entrapped in septin cages showed that the number of metabolically active Shigella in septin‐ or p62‐depleted cells is reduced. Targeted metabolomic analysis revealed that host cell glycolysis is dysregulated in septin‐depleted cells, suggesting a key role for septins in modulation of glycolysis. Together, these results suggest that septins and the autophagy machinery may regulate metabolic pathways that promote the proliferation intracellular Shigella not entrapped in septin cages.
Berger C, Crepin V, Roumeliotis TI, et al., 2017, Citrobacter rodentium subverts ATP flux 1 and cholesterol homeostasis in 2 intestinal epithelial cell in vivo, Cell Metabolism, Vol: 26, Pages: 738-752.e6, ISSN: 1550-4131
The intestinal epithelial cells (IECs) that line the gut form a robust line of defense against ingested pathogens. We investigated the impact of infection with the enteric pathogen Citrobacter rodentium on mouse IEC metabolism using global proteomic and targeted metabolomics and lipidomics. The major signatures of the infection were upregulation of the sugar transporter Sglt4, aerobic glycolysis, and production of phosphocreatine, which mobilizes cytosolic energy. In contrast, biogenesis of mitochondrial cardiolipins, essential for ATP production, was inhibited, which coincided with increased levels of mucosal O2 and a reduction in colon-associated anaerobic commensals. In addition, IECs responded to infection by activating Srebp2 and the cholesterol biosynthetic pathway. Unexpectedly, infected IECs also upregulated the cholesterol efflux proteins AbcA1, AbcG8, and ApoA1, resulting in higher levels of fecal cholesterol and a bloom of Proteobacteria. These results suggest that C. rodentium manipulates host metabolism to evade innate immune responses and establish a favorable gut ecosystem.
Robert CB, Thomson M, Vercellone A, et al., 2017, Mass spectrometry analysis of intact Francisella bacteria identifies lipid A structure remodeling in response to acidic pH stress, BIOCHIMIE, Vol: 141, Pages: 16-20, ISSN: 0300-9084
Buchieri MV, Cimino M, Rebollo-Ramirez S, et al., 2017, Nitazoxanide Analogs Require Nitroreduction for Antimicrobial Activity in Mycobacterium smegmatis, JOURNAL OF MEDICINAL CHEMISTRY, Vol: 60, Pages: 7425-7433, ISSN: 0022-2623
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