Project description:With the global increase in the use of carbapenems, several gram-negative bacteria have acquired carbapenem resistance, thereby limiting treatment options. Klebsiella pneumoniae is one of such notorious pathogen that is being widely studied to find novel resistance mechanisms and drug targets. These antibiotic-resistant clinical isolates generally harbor many genetic alterations, and identification of causal mutations will provide insights into the molecular mechanisms of antibiotic resistance. We propose a method to prioritize mutated genes responsible for antibiotic resistance, in which mutated genes that also show significant expression changes among their functionally coupled genes become more likely candidates. For network-based analyses, we developed a genome-scale co-functional network of K. pneumoniae genes, KlebNet (www.inetbio.org/klebnet). Using KlebNet, we could reconstruct functional modules for antibiotic-resistance, and virulence, and retrieved functional association between them. With complementation assays with top candidate genes, we could validate a gene for negative regulation of meropenem resistance and four genes for positive regulation of virulence in Galleria mellonella larvae. Therefore, our study demonstrated the feasibility of network-based identification of genes required for antimicrobial resistance and virulence of human pathogenic bacteria with genomic and transcriptomic profiles from antibiotic-resistant clinical isolates.
Project description:The increasing antibiotic resistance of Klebsiella pneumoniae poses a serious threat to global public health. To investigate the antibiotic resistance mechanism of Klebsiella pneumonia, we performed gene expression profiling analysis using RNA-seq data for clinical isolates of Klebsiella pneumonia, KPN16 and ATCC13883. Our results showed that mutant strain KPN16 is likely to act against the antibiotics through increased increased butanoate metabolism and lipopolysaccharide biosynthesis, and decreased transmembrane transport activity.
Project description:The emergence and spread of polymyxin resistance, especially among Klebsiella pneumoniae isolates threaten the effective management of infections. This study profiled for polymyxin resistance mechanisms and investigated the activity of polymyxins plus vancomycin against carbapenem- and polymyxin-resistant K. pneumoniae.
Project description:The study aimed to characterize plasmids mediating carbepenem resistance in Klebsiella pneumoniae in Pretoria, South Africa. We analysed 56 K. pneumoniae isolates collected from academic hospital around Pretoria. Based on phenotypic and molecular results of these isolates, 6 representative isolates were chosen for further analysis using long reads sequencing platform. We observed multidrug resistant phenotype in all these isolates, including resistance to aminoglycosides, tetracycline, phenicol, fosfomycin, floroquinolones, and beta-lactams antibiotics. The blaOXA-48/181 and blaNDM-1/7 were manily the plasmid-mediated carbapenemases responsible for carbapenem resistance in the K. pneumoniae isolates in these academic hospitals. These carbapenemase genes were mainly associated with plasmid replicon groups IncF, IncL/M, IncA/C, and IncX3. This study showed plasmid-mediated carbapenemase spread of blaOXA and blaNDM genes mediated by conjugative plasmids in Pretoria hospitals.
Project description:This study identified and compared the bacterial diversity and the antimicrobial resistance profile of clinically relevant isolates around a newly developed hospital and university precinct
Project description:Virulence is a key trait under selection during host-parasite coevolution. In order to obtain increased fitness, parasites are predicted to increase their ability to circumvent and overcome host immunity. A particular challenge for pathogens are external immune systems, found among various invertebrates. Such external immune systems are chemical defence systems comprised of highly potent antimicrobial compounds released by prospective hosts into the environment. We carried out a coevolution experiment with the entomopathogenic fungus, Beauveria bassiana, and the red flour beetle, Tribolium castaneum, which has a well-documented external immune system. Surprisingly, after just seven transfers of experimental evolution we saw a significant increase in virulence in all B. bassiana. This increase in virulence was mainly the result of the B. bassiana isolates evolving resistance to the external immune defences of the T. castaneum beetles, but not obviously through the increased production of toxins or other harmful substances. Furthermore, transcriptomic analyses of B. bassiana RNA-seq data implicates up-regulation of genes responsible for resistance to oxidative stress underlying the observed resistance. We conclude that external immunity acts as a powerful selective force for virulence evolution, with an increase in virulence being achieved apparently entirely by overcoming these defences, most likely due to elevated oxidative stress resistance.
Project description:Salmonella Heidelberg is currently the 9th common serovar and has more than twice the average incidence of blood infections in Salmonella. A recent Salmonella Heidelberg outbreak in chicken infected 634 people during 2013-2014, with a hospitalization rate of 38% and an invasive illness rate of 15%. While the company’s history suggested longstanding sanitation issues, the strains’ characteristics which may have contributed to the outbreak are unknown. We hypothesized that the outbreak strains of S. Heidelberg might possess enhanced stress tolerance or virulence capabilities. Consequently, we obtained nine food isolates collected during the outbreak investigation and several reference isolates and tested their tolerance to processing stresses, their ability to form biofilms, and their invasiveness in vitro. We further performed RNA-sequencing on three isolates with varying heat tolerance to determine the mechanism behind our isolates’ enhanced heat tolerance. Ultimately, we determined that (i) many Salmonella Heidelberg isolates associated with a foodborne outbreak have enhanced heat resistance (ii) Salmonella Heidelberg outbreak isolates have enhanced biofilm-forming ability under stressful conditions, compared to the reference strain (iii) exposure to heat stress may also increase Salmonella Heidelberg isolates’ antibiotic resistance and virulence capabilities and (iv) Salmonella Heidelberg outbreak-associated isolates are primed to better survive stress and cause illness. This data helps explain the severity and scope of the outbreak these isolates are associated with and can be used to inform regulatory decisions on Salmonella in poultry and to develop assays to screen isolates for stress tolerance and likelihood of causing severe illness.
Project description:A collection of 61 Salmonella enterica serovar Typhimurium (S. Typhimurium) of animal and human origin, matched as closely as possible by phage type, antimicrobial resistance pattern and place / time of isolation, and sourced from farms or hospitals in Scotland, were analysed by antimicrobial susceptibility testing, phage typing, pulsed field gel electrophoresis (PFGE), plasmid profiling and DNA microarrays. PFGE of all 61 isolates revealed ten PFGE profiles, which clustered by phage type and antibiotic resistance pattern, with human and animal isolates distributed between PFGE profiles. Analysis of 23 representative S. Typhimurium strains hybridised to a composite Salmonella DNA microarray identified a small number of specific regions of genome variation between different phage types and PFGE profiles. These variable regions of DNA were typically located within prophage-like elements. Simple PCR assays were subsequently designed to discriminate between different isolates from the same geographical region.
Project description:We gathered the proteomic profile of 202 clinical P. aeruginosa isolates derived from a cystic fibrosis lung under planktonic growth conditions. Firstly, a comprehensive transcript/protein correlation across 174 clinical isolates at the same growth stage was performed allowing a characterization of proteins with long and short lifetimes. Consistent with the results from previous studies, proteins of the translational machinery and the key Quorum sensing mediators RpoS, Vfr, RhlR and MvfR were characterized as short-lived proteins. Again, no biochemical metric could explain differences between protein lifetimes further demonstrating a potentially undervalued importance of post-transcriptional regulation.
Secondly, a comparative multi-omics analysis was performed that highlighted the capacity to unearth novel characteristics for both antibiotic resistance and virulence traits. Investigating various tobramycin resistance mechanisms, the efflux pump system MexXY-OprM was determined as a key contributor of aminoglycoside modifying enzyme-driven resistance. MexY protein abundance was furthermore found to be directly regulated by the negative regulator MexZ. In tobramycin resistant isolates, the MexZ regulator was frequently identified as mutated or completely absent due to a possibly unidentified mechanism. This work found novel possible bacterial virulence factors by statistically comparing quantitative data and phenotypic survival data from a Galleria mellonella infection model. Additionally, a Random forest machine learning model was applied. The predictors with the highest predictive importance for the phenotypes of swarming motility, various antibiotic resistance phenotypes, and virulence were listed and discussed.
Project description:Antimicrobial resistance (AMR) is a pandemic spread across multiple infectious disease microbes. To provide a new tool to study AMR, here we develop a Klebsiella pneumoniae cell-free gene expression (CFE) system. To characterise the system, we use proteomics to compare this to a Escherichia coli MG1655 CFE model, to identify relative differences and unique proteins. Then we use this native CFE system to profile antimicrobial activity in comparison to whole cell inhibition, to reveal host differences in IC50/MIC50 values. Finally, we use the CFE tool to study AMR variants, at a proof-of-concept level. As an exemplar, we show that RpoB H526L confers a 58-fold increase in CFE resistance to rifampicin – a common genotype frequently observed in rifampicin-resistant Mycobacterium tuberculosis clinical isolates. In summary, we provide a cell-free synthetic biology strategy for the profiling of antibiotic sensitivity and resistance from K. pneumoniae. While initial processing requires Biosafety Level 2, the final extracts are non-living and suitable for long-term storage, and potentially transfer to a Biosafety Level 1 lab. This bioassay has potential uses for early-stage host-specific antimicrobial development and the testing of AMR variants for structure-activity relationship studies. The data reposited is label-free high-resolution LC-MS proteomics data performed to characterise the proteins in cell-free extract of K. pneumoniae ATCC 13882 and compare to that of E. coli MG1655 to identify common and unique proteins. We also characterised the proteins of K. pneumoniae clinically resistant isolates ST258-T1b and NJST258-1, and compared them to K. pneumoniae ATCC 13882 laboratory strain.