Project description:While ESBL and AmpC beta-lactamases barely degrade carbapenems, they are able to bind them and prevent them from interacting with penicillin binding proteins thereby preventing their effect. When these beta-lactamases are expressed at a high level and combined with a decreased influx of carbapenems due to a decrease in membrane permeability, Enterobacterales can become resistant to carbapenems. In this study we developed a LC-MS/MS assay for the detection of the E. coli porins OmpC and OmpF, it’s chromosomal AmpC beta-lactamase and the plasmid-mediated CMY-2 beta-lactamase. Subsequently, we cultured CMY-2 positive E. coli isolates in the presence of meropenem and analyzed mutants that showed increased resistance to meropenem using our developed assay and western blot. In all five selected strains, a decrease in OmpC and/or OmpF was the first event towards an increase in meropenem minimum inhibitory concentrations (MICs). Subsequently, in four of the five isolate series, MICs increased further after an increase in CMY-2-like production.
Project description:Pseudomonas aeruginosa is a major opportunistic pathogen causing a wide range of infections and one of the most problematic bacteria regarding antibiotic resistance, with an increasing incidence of multidrug and extensively-drug resistant strains, including resistance to last resource antibiotics such as carbapenems. Resistances are often due to complex interplays of naturally and acquired resistance mechanisms which are enhanced by its remarkably large regulatory network. Thus, the use of non-targeted shotgun methodologies such as mass spectrometry-based proteomics is crucial to understand these interplays and to reveal possible strain and species-specific novel mechanisms of antibiotic resistance. The aim of this study was to determine the proteomic response of two carbapenem-resistant and extensively-drug-resistant P. aeruginosa strains to subminimal inhibitory concentrations (sub-MICs) of meropenem. The strains belonged to high-risk clones ST235 and ST395, one carrying a class 1 integron-encoded VIM-4 metallo-β-lactamase and one carrying no acquired antibiotic resistance genes. Each strain was cultivated with three different sub-MICs of meropenem, and a quantitative shotgun proteomic approach was applied, using tandem mass tag (TMT) isobaric labeling followed by nano-liquid chromatography tandem-mass spectrometry, to determine significantly up- or down-regulated proteins and enriched groups of proteins and pathways. Cultivation of both strains with ½ and ¼ of the MIC, resulted in hundreds of differentially regulated proteins, including several β-lactamases, transport-related proteins (including multiple porins and efflux pumps), proteins associated with peptidoglycan metabolism and cell wall organization and dozens of regulatory proteins. Remarkably, all components of the H1 type VI secretion system were up-regulated in one of the strains. Enrichment analyses revealed that multiple metabolic pathways were affected. Additionally, numerous proteins of unknown function were also differentially-regulated in each strain. In conclusion, high subminimal-inhibitory concentrations of meropenem cause massive changes in the proteomes of carbapenem-resistant P. aeruginosa strains, involving a wide range of common and strain-specific mechanisms and proteins, many still uncharacterized which might potentially play a role in the susceptibility of P. aeruginosa to meropenem.
Project description:New and rapid antimicrobial susceptibility/resistance testing methods are required for bacteria from positive blood cultures. In the current study we developed and evaluated a targeted LC-MS/MS assay for the detection of beta-lactam, aminoglycoside and fluoroquinolone resistance mechanisms in blood cultures positive for E. coli or K. pneumoniae. Selected targets were the beta-lactamases SHV, TEM, OXA-1-like, CTX-M-1-like, CMY-2-like, chromosomal E. coli AmpC, OXA-48-like, NDM, VIM and KPC, the aminoglycoside modifying enzymes AAC(3)-Ia, AAC(3)-II, AAC(3)-IV, AAC(3)-VI, AAC(6’)-Ib, ANT(2”)-I and APH(3’)-VI, the 16S-RMTases ArmA, RmtB, RmtC and RmtF, the quinolone resistance mechanisms QnrA, QnrB, AAC(6’)-Ib-cr, the wildtype QRDR of GyrA, and for E. coli, the porins OmpC and OmpF. The developed assay was evaluated using 100 prospectively collected positive blood cultures, 100 negative blood cultures inoculated with isolates that were previously collected from blood cultures, and 48 isolates inoculated with isolates carrying genes of less prevalent resistance mechanisms.
Project description:Background: Antimicrobial resistance is generally studied using a combination of growth inhibition measurements, sometimes in combination with DNA detection methods. However, the actual proteins that cause resistance such as enzymes, efflux pumps and a lack of porins cannot be detected by these methods. Improvements in liquid chromatography (LC) and mass spectrometry (MS) enabled easier and more comprehensive proteome analysis. In the current study, these three methods are combined into a multi-omics approach to analyze resistance against frequently used antibiotics within the beta-lactam, aminoglycoside and fluoroquinolone group in E. coli and K. pneumoniae. Objectives: We aimed to analyze which currently known antimicrobial resistance genes are detected at the protein level using liquid chromatography-mass spectrometry (LC-MS/MS) and to assess whether these could explain beta-lactam, aminoglycoside, and fluoroquinolone resistance in the studied isolates. Furthermore, we aimed to identify significant protein to resistance correlations which have not yet been described and to correlate the abundance of different porins to resistance. Methods: Whole genome sequencing, high-resolution LC-MS/MS and antimicrobial susceptibility testing by broth microdilution were performed for 187 clinical E. coli and K. pneumoniae isolates. Resistance genes and proteins were identified using the Comprehensive Antibiotic Resistance Database (CARD). All proteins were annotated using the NCBI RefSeq database and Prokka. Results & Conclusion: Proteins of small spectrum beta-lactamases, extended spectrum beta-lactamases, AmpC beta-lactamases, carbapenemases, and proteins of 16S ribosomal RNA methyltransferases and aminoglycoside acetyltransferases can be detected in E. coli and K. pneumoniae by LC-MS/MS. The detected mechanisms could explain phenotypic resistance in most of the studied isolates. Differences in the abundance and the primary structure of other proteins such as porins also correlated with resistance. LC-MS/MS is a different and complementary method which can be used to characterize antimicrobial resistance in detail as not only the primary resistance causing mechanisms are detected, but also secondary enhancing resistance mechanisms.
Project description:Background: Antimicrobial resistance is generally studied using a combination of growth inhibition measurements, sometimes in combination with DNA detection methods. However, the actual proteins that cause resistance such as enzymes, efflux pumps and a lack of porins cannot be detected by these methods. Improvements in liquid chromatography (LC) and mass spectrometry (MS) enabled easier and more comprehensive proteome analysis. In the current study, these three methods are combined into a multi-omics approach to analyze resistance against frequently used antibiotics within the beta-lactam, aminoglycoside and fluoroquinolone group in E. coli and K. pneumoniae. Objectives: We aimed to analyze which currently known antimicrobial resistance genes are detected at the protein level using liquid chromatography-mass spectrometry (LC-MS/MS) and to assess whether these could explain beta-lactam, aminoglycoside, and fluoroquinolone resistance in the studied isolates. Furthermore, we aimed to identify significant protein to resistance correlations which have not yet been described and to correlate the abundance of different porins to resistance. Methods: Whole genome sequencing, high-resolution LC-MS/MS and antimicrobial susceptibility testing by broth microdilution were performed for 187 clinical E. coli and K. pneumoniae isolates. Resistance genes and proteins were identified using the Comprehensive Antibiotic Resistance Database (CARD). All proteins were annotated using the NCBI RefSeq database and Prokka. Results & Conclusion: Proteins of small spectrum beta-lactamases, extended spectrum beta-lactamases, AmpC beta-lactamases, carbapenemases, and proteins of 16S ribosomal RNA methyltransferases and aminoglycoside acetyltransferases can be detected in E. coli and K. pneumoniae by LC-MS/MS. The detected mechanisms could explain phenotypic resistance in most of the studied isolates. Differences in the abundance and the primary structure of other proteins such as porins also correlated with resistance. LC-MS/MS is a different and complementary method which can be used to characterize antimicrobial resistance in detail as not only the primary resistance causing mechanisms are detected, but also secondary enhancing resistance mechanisms.
Project description:The goals of this dual-seq experiment were to 1) identify transcriptional changes between mono-species and dual-species biofilms of Candida albicans and Pseudomonas aeruginosa and 2) identify transcriptional changes within mono- or dual-species P. aeruginosa biofilm cells in response to meropenem treatment.
Project description:The aim of the experiment was to assay every gene in the E. coli genome to identify those that contribute to increased or decreased susceptibility to the beta-lactam antibiotic meropenem. A library of transposon-insertion mutants was grown overnight in the presence or absence of a range of concentrations of meropenem. Different concentrations of IPTG were also used to promote expression from a transposon-encoded promoter to assay the effects of increased transcription for each gene. DNA sequencing was then used to reveal the locations of the transposons in every mutant. By comparing the numbers of each mutant between conditions, information can be gained about the relative fitness of that mutant under the conditions tested.