Project description:Antibiotic use can lead to expansion of multi-drug resistant pathobionts within the gut microbiome that can cause life-threatening infections. Selective alternatives to conventional antibiotics are in dire need. Here, we describe a Klebsiella PhageBank that enables the rapid design of antimicrobial bacteriophage cocktails to treat multi-drug resistant Klebsiella pneumoniae. Using a transposon library in carbapenem-resistant K. pneumoniae, we identified host factors required for phage infection in major Klebsiella phage families. Leveraging the diversity of the PhageBank and experimental evolution strategies, we formulated combinations of phages that minimize the occurrence of phage resistance in vitro. Optimized bacteriophage cocktails selectively suppressed the burden of multi-drug resistant K. pneumoniae in the mouse gut microbiome and drove bacterial populations to lose key virulence factors that act as phage receptors. Further, phage-mediated diversification of bacterial populations in the gut enabled co-evolution of phage variants with higher virulence and a broader host range. Altogether, the Klebsiella PhageBank represents a roadmap for both phage researchers and clinicians to enable phage therapy against a critical multidrug-resistant human pathogen.
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:Carbapenem-resistant Klebsiella pneumoniae classified as multilocus sequence type 258 (ST258)are a problem in healthcare settings in many countries globally. ST258 isolates are resistant tomultiple classes of antibiotics and can cause life-threatening infections, such as pneumonia andsepsis, in susceptible individuals. Treatment strategies for such infections are limited. Hence,understanding the response of K. pneumoniae to host factors in the presence of antibiotics couldreveal mechanisms employed by the pathogen to evade killing in the susceptible host, as well asinform treatment of infections. Here, we investigated the ability of subinhibitory concentrationsof antibiotics to alter K. pneumoniae capsule polysaccharide (CPS) production and survival innormal human serum. Several antibiotics tested enhanced ST258 survival in normal humanserum. Unexpectedly, subinhibitory concentrations of mupirocin increased survival in 7 of 10clinical isolates tested, and caused up-regulated expression of CPS biosynthesis genes and CPSproduction in a selected ST258 clinical isolate (34446) compared with untreated controls.Additionally, mupirocin treatment caused a reduction in the deposition of the serum complementproteins C3b and C5b-9 on the surface of ST258. Transcriptome analyses with isolate 34446indicated that genes implicated in serum resistance, such as aroE, csrD, pyrB, pyrC and traT,were up-regulated following mupirocin treatment. In conclusion, mupirocin causes changes inthe K. pneumoniae transcriptome that likely contribute to the observed decrease in serumsusceptibility via a multifactorial process. Whether these responses are triggered by othercomponents of host defense or therapeutics that were not tested here merits further investigation.
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:K. pneumoniae, a Gram-negative bacterium, is normally associated with pneumonia in patients with weakened immune systems. However, it is also a prevalent nosocomial infectious agent that can be found in infected surgical sites and combat wounds. Many of these clinical strains display multi-drug resistance. We have worked with a clinical strain of K. pneumoniae that was initially isolated from a wound of an injured soldier. This strain demonstrated resistance to many commonly used antibiotics, but sensitivity to carbapenems. This isolate was capable of forming biofilms in vitro, contributing to its increased antibiotic resistance and impaired clearance. We were interested in determining how sublethal concentrations of carbapenem treatment specifically affect K. pneumoniae biofilms both in morphology and genomic expression. Scanning electron microscopy showed striking morphological differences between untreated and treated biofilms, including rounding, blebbing, and dimpling of treated cells. Comparative transcriptome analysis using RNA sequencing technology identified a large number of open reading frames (ORFs) differentially regulated in response to carbapenem treatment at 2 and 24 hours. ORFs upregulated with carbapenem treatment included genes involved in resistance, antiporters, and autoinducers. ORFs downregulated included metal transporters, membrane biosynthesis proteins, and motility proteins. Quantitative real time PCR validated the general trend of some of these differentially regulated ORFs. Treating K. pneumoniae biofilms with sublethal concentrations of carbapenems induced a wide-range of phenotypic and gene expression changes. This study reveals some of the mechanisms underlying how sublethal amounts of carbapenems could affect the overall fitness and pathogenic potential of K. pneumoniae biofilm cells.
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.