Biology subjects

Rattle, J.

Publications and source records attributed to Rattle, J..

4 recordsLinked to original sources

bioRxiv2026

The capsule of hypervirulent Klebsiella pneumoniae maintains neutrophils in neutral activation state

Hypervirulent Klebsiella pneumoniae (hvKp) cause invasive infections despite robust neutrophil recruitment, yet the mechanisms enabling persistence in neutrophil-rich environments remain poorly defined. Here, we show that hvKp do not simply resist neutrophil antimicrobial mechanisms but instead constrain neutrophils into a neutral functional state characterised by limited bactericidal activity. Using genetic dissection of the rmpADC locus, pharmacological inhibition of neutrophil effector pathways, and analysis of a diverse panel of clinical isolates, we demonstrate that rmpADC-driven capsule properties uncouple neutrophil recognition and activation from bacterial killing. Deletion of rmpADC restores phagocytosis, degranulation, and intraphagosomal killing, whereas loss of individual rmpD or rmpC permits neutrophil activation without bacterial killing. Moreover, hypermucoviscosity alone is sufficient to protect bacteria from neutrophil-mediated killing across multiple genetic backgrounds. Together, these findings identify capsule-driven immune state control as a central mechanism of hvKp neutrophil evasion and reveal distinct thresholds governing neutrophil activation and bactericidal outcome.

immunology↗

bioRxiv2025

TraN variants mediate conjugation species specificity of IncA/C, IncH and Acinetobacter baumannii plasmids

IncA/C and IncH plasmids commonly carry antimicrobial resistance genes, notably blaNDM-1. Although these plasmids disseminate among Gram-negative pathogens via conjugation, the mechanisms underlying mating pair stabilisation (MPS) and conjugation species specificity remain poorly understood. In IncF plasmids, MPS is mediated by interactions between outer membrane proteins (OMP) encoded by the plasmids in the donor (TraN) and by the chromosome in the recipient. Using the Plascad database, we extracted 1,436 TraN sequences: 62.5% (898/1,436), mainly in IncF plasmids, are 550-660aa (we renamed TraN short, TraNS); 15% (216/1,436), in IncA/C plasmids, are 880-950aa (TraN medium, TraNM); and 11% (160/1,436), in IncH plasmids, are 1,050-1,070aa (TraN long, TraNL). A group of six TraN from Acinetobacter baumannii plasmids (891aa) were designated TraN V-shaped (TraNV). Like TraNS, TraNM and TraNL contain base and distal tip domains essential for conjugation, whereas TraNV has a base and two distinct tip domains forming a V-shaped structure. TraNM, TraNL and TraNV determine conjugation species specificity, with TraNL cooperating with OmpA. Tip swapping reverses conjugation specificity, revealing how TraNM and TraNL diversity influence plasmid host range and AMR dissemination. Our new data reveal the molecular basis of plasmid host specificity and broaden our understanding of how conjugation drives the dissemination of antimicrobial resistance genes among clinically relevant bacteria.

microbiology↗

bioRxiv2025

citrOgen: a synthesis-free polysaccharide and protein antigen-presentation to antibody-induction platform

Existing technologies employed to generate antibodies against bacterial polysaccharides and proteins rely on the availability of purified or synthetic antigens. Here we present a genetics-based platform that utilises Citrobacter rodentium (CR), an enteric mouse pathogen, to both produce and present complex heterologous polysaccharides and protein antigen complexes during natural infection. As proof of concept, we use lipopolysaccharides (O), capsular polysaccharides (K) and type 3 fimbrial (T3F) antigens expressed by the WHO critical priority pathogens Klebsiella pneumoniae (KP) and Escherichia coli (EC). Following one infection cycle (28 days) CR induces specific IgG antibodies against KPO1, ECO25b, KPK2 and KPT3F. We demonstrate that the antibodies are functional in downstream applications including protection against pathogenic KP challenge, KP capsular serotyping and KP biofilm inhibition. Whilst KP and EC antigens were used as prototypical examples, this modular platform is now readily adaptable to generate antibodies against diverse polysaccharide and protein antigens, with basic science, public health and therapeutic applications.

microbiology↗

bioRxiv2024

The exopolysaccharide Poly-N-Acetyl-Glucosamine (PNAG) coats Klebsiella pneumoniae in vivo

The conserved bacterial polysaccharide Poly-N-Acetyl-Glucosamine (PNAG) is a potential broad-spectrum vaccine candidate. While the immunogenicity of PNAG-based vaccine candidates has been established, characterisation of PNAG production across clinically relevant bacteria remains largely unknown. In particular, PNAG production in the Gram-negative pathogen Klebsiella pneumoniae (KP) is not well understood. Here, we demonstrate that PNAG production is prevalent in clinical KP isolates, where it is secreted as extracellular networks during adherent growth conditions. However, during severe KP pulmonary infection, KP PNAG production undergoes a switch to a cell-associated phenotype, coating the bacterial cell surface. By screening a panel of isogenic KP mutants in prominent cell surface components ({Delta}wcaJ,{Delta} rmpADC,{Delta} rfb,{Delta} ompA and{Delta} ompk36), we identified KP capsular polysaccharide as a key determinant underpinning the phenotype. Deleting genes involved in capsule synthesis ({Delta}wcaJ) and regulation ({Delta}rmpADC) resulted in cell-associated PNAG during adherent growth and infection of alveolar epithelial cells in vitro. Taken together, we describe a novel interaction between KP surface polysaccharides and detect for the first time, cell-associated PNAG in KP during lung infection, highlighting PNAG as an attractive KP vaccine antigen. Author summaryThe Gram-negative pathogen Klebsiella pneumoniae (KP) is a leading cause of hospital-associated lung and bloodstream infections worldwide. As KP exhibits resistance to most frontline antibiotics, there is a growing demand for immune-based strategies to treat KP infections. Poly-N-Acetyl-Glucosamine (PNAG) is a surface sugar produced by most clinically relevant bacteria, including KP. However, relatively little is known about PNAG production in KP. Therefore, we set out to characterise PNAG production in KP during in vitro growth and following lung infection in a pulmonary mouse model. During in vitro growth, KP produces extracellular PNAG networks. In contrast, during an in vivo severe lung infection, PNAG is found cell-associated, coating the bacterial surface. We propose that the visible change in KP PNAG between in vitro and in vivo environments is due to crosstalk with capsule, another polysaccharide on the KP surface. Together, this supports PNAG as an attractive KP antigen.

microbiology↗