Project description:Carbapenem-resistant Acinetobacter baumannii (CRAb) is an urgent public health threat, according to the CDC. This pathogen has few treatment options and causes severe nosocomial infections with >50% fatality rate. Although previous studies have examined the proteome of CRAb, there have been no focused analyses of dynamic changes to β-lactamase expression that may occur due to drug exposure. Here, we present our initial proteomic study of variation in β-lactamase expression that occurs in CRAb with different β-lactam antibiotics. Briefly, drug resistance to Ab (ATCC 19606) was induced by the administration of various classes of β-lactam antibiotics, and the cell-free supernatant was isolated, concentrated, separated by SDS-PAGE, digested with trypsin, and identified by label-free LC-MS-based quantitative proteomics. Thirteen proteins were identified and evaluated using a 1789 sequence database of Ab β-lactamases from UniProt, the majority of which were Class C β-lactamases (≥80%). Importantly, different antibiotics, even those of the same class (e.g. penicillin and amoxicillin), induced non-equivalent responses comprising various isoforms of Class C and D serine-β-lactamases, resulting in unique resistomes. These results open the door to a new approach of analyzing and studying the problem of multi-drug resistance in bacteria that rely strongly on β-lactamase expression.
Project description:<p>The study of antimicrobial resistance (AMR) in infectious diarrhea has generally been limited to cultivation, antimicrobial susceptibility testing and targeted PCR assays. When individual strains of significance are identified, whole genome shotgun (WGS) sequencing of important clones and clades is performed. Genes that encode resistance to antibiotics have been detected in environmental, insect, human and animal metagenomes and are known as "resistomes". While metagenomic datasets have been mined to characterize the healthy human gut resistome in the Human Microbiome Project and MetaHIT and in a Yanomani Amerindian cohort, directed metagenomic sequencing has not been used to examine the epidemiology of AMR. Especially in developing countries where sanitation is poor, diarrhea and enteric pathogens likely serve to disseminate antibiotic resistance elements of clinical significance. Unregulated use of antibiotics further exacerbates the problem by selection for acquisition of resistance. This is exemplified by recent reports of multiple antibiotic resistance in Shigella strains in India, in Escherichia coli in India and Pakistan, and in nontyphoidal Salmonella (NTS) in South-East Asia. We propose to use deep metagenomic sequencing and genome level assembly to study the epidemiology of AMR in stools of children suffering from diarrhea. Here the epidemiology component will be surveillance and analysis of the microbial composition (to the bacterial species/strain level where possible) and its constituent antimicrobial resistance genetic elements (such as plasmids, integrons, transposons and other mobile genetic elements, or MGEs) in samples from a cohort where diarrhea is prevalent and antibiotic exposure is endemic. The goal will be to assess whether consortia of specific mobile antimicrobial resistance elements associate with species/strains and whether their presence is enhanced or amplified in diarrheal microbiomes and in the presence of antibiotic exposure. This work could potentially identify clonal complexes of organisms and MGEs with enhanced resistance and the potential to transfer this resistance to other enteric pathogens.</p> <p>We have performed WGS, metagenomic assembly and gene/protein mapping to examine and characterize the types of AMR genes and transfer elements (transposons, integrons, bacteriophage, plasmids) and their distribution in bacterial species and strains assembled from DNA isolated from diarrheal and non-diarrheal stools. The samples were acquired from a cohort of pediatric patients and controls from Colombia, South America where antibiotic use is prevalent. As a control, the distribution and abundance of AMR genes can be compared to published studies where resistome gene lists from healthy cohort sequences were compiled. Our approach is more epidemiologic in nature, as we plan to identify and catalogue antimicrobial elements on MGEs capable of spread through a local population and further we will, where possible, link mobile antimicrobial resistance elements with specific strains within the population.</p>
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:Faecal carriage and acquisition of Extended-Spectrum Beta-Lactamase (ESBL)-producing Enterobacteriaceae in dogs, cats and humans: prevalence, risk factors, and co-carriage.