Biology subjects

Idelevich, E. A.

Publications and source records attributed to Idelevich, E. A..

3 recordsLinked to original sources

bioRxiv2024

In-host evolution of classic to convergent Klebsiella pneumoniae sequence type 147 isolates and impact of associated capsular changes on different morphotypes

Klebsiella pneumoniae, an important opportunistic pathogen, has long been categorized into two distinct pathotypes: the often multidrug-resistant classic (cKp) and the highly virulent hypervirulent (hvKp). However, a recent global trend has witnessed the emergence of convergent strains, seamlessly combining antimicrobial resistance with hypervirulence. Our study delved into a series of K. pneumoniae isolates sourced from the same patient, all belonging to the international, high-risk clonal lineage of sequence type 147. As reported in a previous study, these isolates exhibited diverse morphotypes on blood agar, ranging from small white to normal-sized white, grey, or grey and dry (g/d) colonies. Through an interplay of omics and phenotypic experiments, we unraveled the intricate mechanisms governing these distinct colony morphologies and their implications on bacterial virulence and resilience. While the earlier isolates demonstrated modest levels of resistance and virulence, their later counterparts showed significantly heightened levels, attributed to the acquisition of additional plasmids. Bioinformatics analysis unveiled a chromosomal insertion of a hybrid plasmid in one isolate, marking an unprecedented in-host microevolution from the classic to the convergent pathotype. All morphotypes exhibited positive insertion sequences around or within the K loci, with the grey or g/d phenotypes arising from impaired K loci. Despite lower serum resistance, these morphotypes demonstrated superior adhesion to human epithelial cells. Interestingly, while capsule-deficient strains are conventionally associated with decreased virulence, our isolates displayed high mortality rates in the Galleria mellonella infection model. In conclusion, our findings not only provide unprecedented insights into in-host microevolution within a patient, transitioning from the classic to the convergent pathotype, but also contribute significantly to the understanding of the diverse morphotypes exhibited by K. pneumoniae.

microbiology↗

bioRxiv2024

Temperatures above 37°C increase virulence of a convergent Klebsiella pneumoniae sequence type 307 strain

Hypermucoviscosity in Klebsiella pneumoniae is often related to the overexpression of capsular polysaccharides, regulated by complex biosynthetic mechanisms in response to external cues. However, little is known about the processes involved in hypermucoviscosity in convergent K. pneumoniae, which combine extensive drug resistance with high bacterial virulence, under pathophysiological conditions. This study aimed to fill this gap by investigating the temperature dependence of hypermucoviscosity and overall virulence in a convergent K. pneumoniae strain isolated during a clonal outbreak belonging to the high-risk sequence type (ST)307. Hypermucoviscosity, biofilm formation, and mortality rates in Galleria mellonella larvae were examined at different temperatures (room temperature, 28{degrees}C, 37{degrees}C, 40{degrees}C and 42{degrees}C) and with various phenotypic experiments including electron microscopy. The underlying mechanisms of the phenotypic changes were explored via qPCR analysis to evaluate plasmid copy numbers, and transcriptomics. Our results indicate a temperature-dependent "switch" above 37{degrees}C to a hypermucoviscous phenotype, correlating with increased biofilm formation capacity and in vivo mortality, which might be due to a bacterial response to pathophysiological conditions, i.e., fever. In addition, we detected upregulation of a hybrid plasmid encoding both carbapenemase and the mucoid regulator rmpA genes. Surprisingly, rmpA did not exhibit temperature-dependent differential gene expression, suggesting other drivers. Apparent co-regulation of hypermucoviscosity and fimbrial expression was also identified. This study not only revealed the impact that increased temperatures above 37{degrees}C have on hypermucoviscosity and virulence in a convergent K. pneumoniae strain but contributes to the understanding of previously unrecognized dimension of K. pneumoniaes behavior, emphasizing its adaptability to changing environments. Abstract importanceUnderstanding the temperature-dependent dynamics of hypermucoviscosity in Klebsiella pneumoniae is crucial for unraveling the intricacies of its hypervirulence. This study investigates a convergent K. pneumoniae strain, ST307, revealing a temperature-dependent switch to hypermucoviscosity above 37 {degrees}C. The findings showcase a correlation between increased temperature, hypermucoviscosity, enhanced attachment, and heightened in vivo mortality. Notably, a hybrid plasmid encoding carbapenemase and mucoid regulator genes was upregulated at elevated temperatures. The study sheds light on previously unexplored aspects of K. pneumoniae behavior, emphasizing its adaptability in response to changing environments. The identified temperature-associated regulatory mechanisms offer insights into the pathogens response to fever, contributing to our broader understanding of bacterial adaptation. This research contributes to addressing the global challenge of hypervirulent, drug-resistant K. pneumoniae strains, providing valuable implications for future treatment strategies.

microbiology↗

bioRxiv2024

Klebsiella pneumoniae exhibiting a phenotypic hyper-splitting phenomenon including the formation of small colony variants

In this study, we characterized a Klebsiella pneumoniae strain in a patient with shrapnel hip injury, which resulted in multiple phenotypic changes, including the formation of a small colony variant (SCV) phenotype. Although already described since the 1960s, there is little knowledge about SCV phenotypes in Enterobacteriaceae. The formation of SCVs has been recognized as a bacterial strategy to evade host immune responses and compromise the efficacy of antimicrobial therapies, leading to persistent and recurrent courses of infections. In this case, 14 different, clonally identical resisto- and morpho-types were distinguished from the patients urine and tissue samples. Whole genome sequencing revealed the K. pneumoniae high-risk clonal lineage belonging to sequence type 147. Subculturing the SCV colonies consistently resulted in the reappearance of the initial SCV phenotype and three stable normal-sized phenotypes with distinct morphological characteristics. Additionally, an increase in resistance was observed over time in isolates that shared the same colony appearance. Our findings highlight the complexity of bacterial behavior by revealing a case of phenotypic "hyper-splitting" in a K. pneumoniae SCV and its potential clinical significance.

microbiology↗