Project description:Fosfomycin is a bactericidal antibiotic, analogous to phosphoenolpyruvate (PEP) that exerts its activity by inhibiting the activity of MurA. This enzyme catalyzes the first step of peptidoglycan biosynthesis, the transfer of enolpyruvate from PEP to uridine- diphosphate-N-acetylglucosamine. Fosfomycin is increasingly used in the last years, mainly for treating infections caused by Gram-negative multidrug resistant bacteria as Stenotrophomonas maltophilia, an opportunistic pathogen characterized by its low susceptibility to antibiotics of common use. The mechanisms of mutational resistance to fosfomycin in Stenotrophomonas maltophilia were studied in the current work. None of the mechanisms so far described for other organisms, which include the production of fosfomycin inactivating enzymes, target modification, induction of alternative peptidoglycan biosynthesis pathway and the impaired entrance of the antibiotic, are involved in the acquisition of such resistance by this bacterial species. Rather the unique cause of resistance in the studied mutants is the mutational inactivation of different enzymes belonging to the Embden-Meyerhof-Parnas central metabolism pathway. The amount of intracellular fosfomycin accumulation did not change in any of these mutants showing that neither the inactivation nor the transport of the antibiotic were involved. Transcriptomic analysis also showed that the mutants did not present changes in the expression level of putative alternative peptidoglycan biosynthesis pathway genes neither any related enzyme. Finally, the mutants did not present an increased PEP concentration that might compete with fosfomycin for its binding to MurA. Based on these results, we describe a completely novel mechanism of antibiotic resistance based on the remodeling of S. maltophilia metabolism.
Project description:Transcriptomic analysis of S. maltophilia D457 after one-hour induction with the antibiotic fosfomycin, the intermediate metabolites phosphoenolpyruvate or glyceraldehyde-3-phosphate
Project description:The antibiotic fosfomycin is widely recognized for treatment of lower urinary tract infections caused by Escherichia coli and lately gained importance as a therapeutic option to combat multidrug resistant bacteria. Still, resistance to fosfomycin frequently develops through mutations reducing its uptake. Whereas the inner membrane transport of fosfomycin has been extensively studied in E. coli, its outer membrane (OM) transport remains insufficiently understood. While evaluating minimal inhibitory concentrations in OM porin-deficient mutants, we observed that the E. coli ΔompCΔompF strain is five times more resistant to fosfomycin than the wild type and the respective single mutants. Continuous monitoring of cell lysis of porin-deficient strains in response to fosfomycin additionally indicated the relevance of LamB. Furthermore, the physiological relevance of OmpF, OmpC and LamB for fosfomycin uptake was confirmed by electrophysiological and transcriptional analysis. This study expands the knowledge of how fosfomycin crosses the OM of E. coli.
Project description:Stenotrophomonas maltophilia is an emerging opportunistic multidrug-resistant pathogen frequently co-isolated with other relevant nosocomial pathogens in respiratory tract infections. S. maltophilia uses the endogenous DSF quorum sensing (QS) system to regulate virulence processes but can also respond to exogenous AHL signals produced by neighboring bacteria. A whole-transcriptome sequencing analysis was performed for S. maltophilia strain K279a in the exponential and stationary phases and in exponential cultures after a treatment with exogenous DSF or AHLs. Among the common top upregulated genes, the putative TetR-like regulator Smlt2053 was selected for functional characterization. This regulator was found to sense long-chain fatty acids, including the QS signal DSF, and activate a β-oxidation catabolic pathway.
Project description:The goal of this study was to elucidate genes that are employed by the bacterivorous nematode Caenorhabditis elegans to respond to the emerging nosocomial bacterial pathogen Stenotrophomonas maltophilia.
Project description:Stenotrophomonas maltophilia is an important opportunistic pathogen affecting primarily hospitalized and immuno-compromised hosts. We constructed an hfq deletion mutant (Delta-hfq) of S. maltophilia, and compared the behaviour of wild-type and Delta-hfq S. maltophilia cells in a variety of assays. Differential RNA sequencing analysis (dRNA-seq) of RNA isolated from S. maltophilia wild-type and Delta-hfq strains showed that Hfq regulates expression of genes encoding flagellar and fimbrial components, transmembrane proteins, as well as enzymes involved in different metabolic pathways. Moreover, we analysed expression of several sRNAs identified by dRNA-seq in wild-type. The accumulation of two sRNAs was strongly reduced in the absence of Hfq. TEX (terminator exonuclease) treated and untreated libraries of the wild type and the Delta-hfq mutant were sequenced and compared
Project description:The interactions between Gram-negative respiratory pathogens and the host environment at the site of infection largely unknown. Pulmonary surfactant serves as an initial point of contact for inhaled bacteria entering the lung and is thought to contain molecular cues that aid colonization and pathogenesis. To gain insight into this ecological transition, we characterized the transcriptional responses of Pseudomonas aeruginosa PA14, Burkholderia thailandensis E264, Klebsiella pneumoniae MGH 78578, and Stenotrophomonas maltophilia K279A exposed to purified pulmonary surfactant (Survanta) through microarrays. This study provides novel insight into the interactions occurring between Gram-negative opportunistic pathogens and the host at an important infection site, and demonstrates the utility of purified lung surfactant preparations for dissecting host-lung pathogen interactions in vitro. The goal of this study was to compare the transcriptional responses of Pseudomonas aeruginosa PA14, Burkholderia thailandensis E264, Klebsiella pneumoniae MGH 78578, and Stenotrophomonas maltophilia K279A exposed to pulmonary surfactant using a custom affymetrix chip designed for their genomes. The goal of this study was to compare the transcriptional responses of Pseudomonas aeruginosa PA14, Burkholderia thailandensis E264, Klebsiella pneumoniae MGH 78578, and Stenotrophomonas maltophilia K279A exposed to pulmonary surfactant using a custom affymetrix chip designed for their genomes.
Project description:Stenotrophomonas maltophilia is an important opportunistic pathogen affecting primarily hospitalized and immuno-compromised hosts. We constructed an hfq deletion mutant (Delta-hfq) of S. maltophilia, and compared the behaviour of wild-type and Delta-hfq S. maltophilia cells in a variety of assays. Differential RNA sequencing analysis (dRNA-seq) of RNA isolated from S. maltophilia wild-type and Delta-hfq strains showed that Hfq regulates expression of genes encoding flagellar and fimbrial components, transmembrane proteins, as well as enzymes involved in different metabolic pathways. Moreover, we analysed expression of several sRNAs identified by dRNA-seq in wild-type. The accumulation of two sRNAs was strongly reduced in the absence of Hfq.
Project description:In this work we describe a robust fosfomycin collateral sensitivity phenotype of Pseudomonas aeruginosa resistant mutants selected by antibiotics from different structural families. The underlying mechanism was the reduced expression of the genes encoding the peptidoglycan-recycling pathway, which preserves the peptidoglycan synthesis in situations where the de novo synthesis is blocked, and of fosA, encoding a fosfomycin-inactivating enzyme.
Project description:Biofilm formation by Escherichia coli was significantly inhibited when co-cultured with Stenotrophomonas maltophilia in static systems. Genes of E. coli involved in species interactions with S. maltophilia were identified in order to allow the study of the mechanisms of inhibited E. coli biofilm formation in co-culture. A total of 89 and 108 genes were identified as differentially expressed in mixed species cultures when growing as biofilm and as planktonic cultures, respectively, compared to the counterpart of pure cultured E. coli. Differential expression of certain identified genes was confirmed using E. coli reporter strains combined with single-cell based flow cytometry analysis. Co-culture with S. maltophilia affected genes involved in metabolism, signal transduction, cell wall composition, and biofilm formation of E. coli. Several selected genes were further confirmed as affecting E. coli biofilm formation in mixed species cultures with S. maltophilia. The data suggest that these genes were involved in species interactions between E. coli and S. maltophilia. This SuperSeries is composed of the SubSeries listed below. Refer to individual Series.