Project description:The present study examines changes in global gene expression patterns and in virulence factor-associated genes in an extended spectrum beta-lactamase (ESBL)-producing UPEC (ESBL019) during the morphologic transitions induced by an ineffective antibiotic and in the presence of human primary bladder epithelial cells. The morphological shifts induced by ineffective antibiotics are associated with significant transcriptional virulence alterations in ESBL-producing UPEC, which may affect survival and persistence in the urinary tract.
Project description:The spread of antibiotic resistance has developed to all known antibiotics. Extended spectrum β-lactamase-producing bacteria are particularly problematic, as they are resistant to a wide range of commonly used antibiotics. Resistance to β-lactams is known to be multifactorial, although the underlying mechanisms generally are poorly understood but critical factors for effective therapy against infections, especially for multi-resistant pathogenic bacteria. In the present study, a plasmid-based homologous recombination system was used to target and delete specific β-lactamase genes (i.e., the blaOXA-1, blaTEM-1 or the ESBL blaCTX-M15) of the clinical strain ESBL Escherichia coli CCUG 73778, generating three “knock-out” clone variants, each one lacking only one of the β-lactamases. The objective was to determine the genotypic impacts of each gene loss on the phenotypic antibiotic resistance and proteome of the bacterium. Quantitative proteomic analyses performed on the three clone variants and the original strain, using tandem mass tags (TMT) and bottom-up liquid chromatography tandem mass spectrometry (LC-MS/MS), after exposure to different concentrations of cefadroxil. Variation of the proteome in each clone variant was determined, to establish the relative importance of each resistance gene and better understand the genetic and proteomic responses and mechanisms of the resistance phenotypes. The knockout of blaCTX-M-15 was observed to have the greatest impact in protein expression, with the knockout of blaOXA-1 also effecting a marked but lower degree of changes. Proteins known to be associated with antibiotic resistance, cell membrane integrity, cellular stress, gene expression and hypothetical/unknown function proteins, among others, demonstrated distinct differences in expression levels (Fold change >1-5 or <-1.5), that may be related to aspects of compensation for the mutant resistance phenotypes. The present study provides a framework to study the impacts of targeted loss of antibiotic resistance genes in clinically relevant strains for understanding the mechanisms of phenotypic antibiotic resistance.
Project description:The emergence of polymyxin resistance in carbapenem-resistant and extended-spectrum -lactamase (ESBL)-producing bacteria is a critical threat to human health, and new treatment strategies are urgently required. Here, we investigated the ability of the safe-for-human use ionophore PBT2 to restore antibiotic sensitivity in polymyxin-resistant, ESBL-producing, carbapenem-resistant Gram-negative human pathogens. PBT2 was observed to resensitize Klebsiella pneumoniae, Escherichia coli, Acinetobacter baumannii and Pseudomonas aeruginosa to last-resort polymyxin class antibiotics, including the less-toxic next-generation polymyxin derivative, FADDI-287. We were unable to select for mutants resistant to PBT2 + FADDI-287 in polymyxin resistant E. coli containing a plasmid-borne mcr-1 gene or K. pneumoniae carrying a chromosomal mgrB mutation. Using a highly invasive K. pneumoniae strain engineered for polymyxin resistance through mgrB mutation, we successfully demonstrated the efficacy of PBT2 + FADDI-287 in vivo for the treatment of Gram-negative sepsis. These data present a new treatment modality to break antibiotic resistance in high priority polymyxin-resistant Gram-negative pathogens.