Biology subjects

Schneiders, T.

Publications and source records attributed to Schneiders, T..

4 recordsLinked to original sources

bioRxiv2024

Genome Analyses of A Worldwide Multisource Collection of Klebsiella variicola Reveal Adaptation Relevant for Human Infection

AO_SCPLOWBSTRACTC_SCPLOWKlebsiella variicola (K.var), part of the Klebsiella pneumoniae (K.pne) species complex, is an emerging human pathogen originally associated with plants. Phylogenomic analyses of a global dataset of isolates categorised as human, animal, plant, or environmental strains suggest that K.var are broadly disseminated regardless of hosts or habitats and exhibit genomic variability that is relevant for occupying and transmitting within and across multiple sources. Ancestral state analyses confirm that K.var are originally derived from non-human sources. Genome-wide association analyses of human versus non-human isolates of K.var indicate isolates from human origins are linked to the loss of cold-shock response genes such as lpxP and cspB. Importantly, human K.var isolates also showed enriched antimicrobial resistance gene content and diversity acquired through mobile genetic elements, horizontal gene transfer and mutations within the chromosomal loci which underscore the impact of antimicrobial exposure and proximity to antibiotic resistant K.pne in nosocomial environments. Capsular profiles of K.var suggest high levels of variability in gene composition and indicate that gene functionality for wcaJ in capsule formation differs between K.var and K.pne. Although capsular specialisation was not observed in a host/habitat or lineage-dependent manner, human isolates harbour, on average, a higher siderophore gene content in addition to mrkD mutations which impact on fimbriae and biofilm formation. There is limited evidence of any specific K.var lineages exhibiting convergence of both virulence and antimicrobial resistance genotypes which suggest that these attributes are evolving independently in clinical strains. Our work highlights that gene attrition and acquisition provide a basis for adaptation of K.var as human pathogens. The broad distribution and evolution of K.var highlight the need for improved diagnostic precision and surveillance under a One Health framework.

microbiology↗

bioRxiv2023

Transposon mutagenesis screen in Klebsiella pneumoniae identifies genetic determinants required for growth in human urine and serum

Klebsiella pneumoniae is a global public health concern due to the rising myriad of hypervirulent and multi-drug resistant clones both alarmingly associated with high mortality. The molecular microbial genetics underpinning these recalcitrant K. pneumoniae infections is unclear, coupled with the emergence of lineages resistant to nearly all present day clinically important antimicrobials. In this study, we performed a genome-wide screen in K. pneumoniae ECL8, a member of the endemic K2-ST375 pathotype most often reported in Asia, to define genes essential for growth in a nutrient-rich laboratory medium (Luria-Bertani medium), human urine and serum. Through transposon directed insertion-site sequencing (TraDIS), a total of 427 genes were identified as essential for growth on LB agar, whereas transposon insertions in 11 and 144 genes decreased fitness for growth in either urine or serum, respectively. These studies provide further knowledge on the genetics of this pathogen but also provide a strong impetus for discovering new antimicrobial targets to improve current therapeutic options for K. pneumoniae infections.

microbiology↗

bioRxiv2022

Rapid Evolution of Colistin Resistance in a Bioreactor Model of Infection of Klebsiella pneumoniae

SynopsisO_ST_ABSObjectivesC_ST_ABSWe seek to understand the dynamics of de novo resistant mutations arising during colistin treatment of an antibiotic-naive population of K. pneumoniae. MethodsWe used a bioreactor model of infection and colistin treatment against the colistin susceptible K. pneumoniae Ecl8. Whole-genome sequencing and MIC profiling was used to characterize genetic and phenotypic state of the bacterial culture at three time points: before treatment, immediately after regrowth following challenge, and at the end point of the experiment. A mathematical model based on the birth-death process was used to gain further insights on the population dynamics of emerging resistant variants. ResultsWe find that, after an initial decline, the population recovers within 24h due to the evolution of highly resistant clones which exhibit MICs >100-fold higher than the parental strain. Recovery is caused by a small number of "founder cells" which have single point mutations mainly in the regulatory genes encoding crrB and pmrB. The mutants arise through spontaneous mutations prior to colistin treatment. ConclusionsDevelopment of colistin resistance during treatment of K. pneumoniae infections is readily achieved if colistin is used as a monotherapy.

microbiology↗

bioRxiv2017

The Envelope Proteome Changes Driven By RamA Overproduction in Klebsiella pneumoniae That Enhance Acquired β-Lactam Resistance

OBJECTIVESIn Klebsiella pneumoniae, overproduction of RamA results in reduced envelope permeability and reduced antimicrobial susceptibility but clinically relevant resistance is rarely observed. Here we have tested whether RamA over-production can enhance acquired {beta}-lactam resistance mechanisms in K. pneumoniae and have defined the envelope protein abundance changes seen upon RamA overproduction during growth in low and high osmolarity media.\n\nMETHODSEnvelope permeability was estimated using a fluorescent dye accumulation assay. Antibiotic susceptibility was measured using disc testing. Total envelope protein production was quantified using LC-MS/MS proteomics and transcript levels quantified by Real Time RT-PCR.\n\nRESULTSRamA overproduction enhanced {beta}-lactamase mediated {beta}-lactam resistance, in some cases dramatically, without altering {beta}-lactamase production. It increased production of efflux pumps and decreased OmpK35 porin production, though micF over-expression showed that OmpK35 reduction has little impact on envelope permeability. A survey of K. pneumoniae bloodstream isolates revealed ramA hyperexpression in 3 out of 4 carbapenemase producers, 1/21 CTX-M producers and 2/19 strains not carrying CTX-M or carbapenemases.\n\nCONCLUSIONSWhilst RamA is not a key mediator of antibiotic resistance in K. pneumoniae on its own, it is potentially important for enhancing the spectrum of acquired {beta}-lactamase mediated {beta}-lactam resistance. LC-MS/MS proteomics analysis has revealed that this enhancement is achieved predominantly through activation of efflux pump production.

microbiology↗