Biology subjects

Hampton, T.

Publications and source records attributed to Hampton, T..

3 recordsLinked to original sources

bioRxiv2026

A bistable type III secretion system is primed and loaded in Pseudomonas aeruginosa hypervirulent isolates with positively selected codon changes in exsA or exsD

Pseudomonas aeruginosa has multiple virulence factors that promote airway infections in people with immune deficiencies. Most clinical isolates from human infections have functional type III secretion systems (T3SSs) that are subject to bistable regulation and secrete the cytotoxic effector ExoS into neutrophils. During airway infection in people with cystic fibrosis (CF), P. aeruginosa maintains bistable regulation or genetically adapts by inactivating or hyperactivating T3SS expression. CF clinical isolates with hyperactive T3SSs have codon changes in the transcriptional regulators, exsA or exsD. It is not known how these mutations: 1) arise, 2) promote hypervirulence, or 3) impact bistable T3SS regulation. To understand how these mutants arise, ~24,000 genomes in the NCBI Pathogens database were searched for positively selected mutations in exs genes based on nonsynonomous to synonymous codon change ratios. Missense and nonsense mutations were detected in exsA (47) or exsD (45) the majority of which are predicted to be positively selected. To determine how one of these codon changes promotes hypervirulence, an exsAT48I isolate was used to establish lung infections in mice engineered with a CF genotype. The exsAT48I mutant and an exsA+ control had similar lung burdens, but the former caused exacerbated weight loss and lung inflammation, suggesting immunopathology from phagocyte death as the cause of hypervirulence. Two additional hyperactive mutants were identified by screening a small collection of isolates from children with CF. Immunoblotting and fluorescence microscopy showed that hyperactive exsA or exsD mutants increased production of T3SS injectisomes and effectors, indicating they have locked on (primed and loaded) phenotypes. ExsA dimer modeling revealed that codon changes like T48I in the {beta}-barrel domain cause a conformational change that hyperactivates the transcription factor. These results define that hyperactive mutants are positively selected, hypervirulent due to lung inflammation, and have primed and loaded T3SSs.

microbiology↗

bioRxiv2022

An rRNA fragment in extracellular vesicles secreted by human airway epithelial cells increases the fluoroquinolone sensitivity of P. aeruginosa

Lung infection by antibiotic resistant strains of Pseudomonas aeruginosa is a well-known concern for immunocompromised hosts including people with lung diseases such as cystic fibrosis. We have previously demonstrated that extracellular vesicles (EVs) secreted by primary human airway epithelial cells (AEC) deliver miRNA let-7b-5p to P. aeruginosa where it suppresses biofilm formation and increases sensitivity to beta-lactam antibiotics. In this study we used RNA-seq to characterize the small RNA (sRNA) content of EVs secreted by AEC and demonstrate transfer of multiple distinct RNA fragments from EVs to P. aeruginosa. Bioinformatic predictions reveal that several sRNAs may target all three subunits of the fluoroquinolone efflux pump MexHI-OpmD, an effect predicted to increase antibiotic sensitivity to fluoroquinolone antibiotics. Exposure of P. aeruginosa to EVs resulted in a significant reduction in the protein levels of MexH (-48%), MexI (-50%) and OpmD (-35%). Moreover, EVs reduced planktonic growth of P. aeruginosa in the presence of the fluoroquinolone antibiotic ciprofloxacin by 20%. A mexGHI-opmD deletion mutant of P. aeruginosa phenocopied this increased sensitivity to ciprofloxacin. Finally, we found that a fragment of an 18S rRNA external transcribed spacer that was transferred to P. aeruginosa by EVs was sufficient to reduce planktonic growth of P. aeruginosa in the presence of ciprofloxacin, to reduce the minimum inhibitory concentration (MIC) of P. aeruginosa for ciprofloxacin by over 50%, and to significantly reduce protein levels of MexH and OpmD. In conclusion, an rRNA fragment secreted by AEC in EVs increases the ciprofloxacin sensitivity of P. aeruginosa by targeting and down-regulating the fluoroquinolone efflux pump MexHI-OpmD. A combination of rRNA fragments and ciprofloxacin packaged in nanoparticles or EVs may benefit patients with antibiotic-resistant P. aeruginosa infections. Author SummaryAccording to the World Health Organization and the U.S. Centers for Disease Control and Prevention the development of antibiotic resistant strains of bacteria, including Pseudomonas aeruginosa, are a significant global threat to human health. Thus, development of new approaches to eliminate antibiotic resistant infections is required. In this study, we report that lung epithelial cells secrete extracellular vesicles (EVs) that fuse with and deliver small rRNAs to P. aeruginosa, and that the rRNAs increase the sensitivity of P. aeruginosa to the antibiotic ciprofloxacin by reducing protein levels of the drug efflux pump MexHI-OpmD. We identified one rRNA fragment that by itself significantly reduced the protein levels of MexH and OpmD and increased the ability of ciprofloxacin to kill P. aeruginosa. We propose that developing synthetic vesicles containing a combination of the rRNA that inhibits antibiotic efflux pumps and ciprofloxacin would benefit patients with antibiotic resistant P. aeruginosa infections.

microbiology↗

bioRxiv2017

An outbreak of Pseudomonas aeruginosa infection linked to a Black Friday piercing event

BackgroundOutbreaks linked to cosmetic piercing are rare, but can cause significant illness. We report the investigation and management of a point-source outbreak that occurred during a \"Black Friday\" event in North West England.\n\nMethodsOutbreak investigation was led by Public Health England, and included active case finding among individuals pierced at a piercing premises between 25/11/2016 (\"Black Friday\") and 7/12/2016. Detailed epidemiological, environmental (including inspection and sampling), and microbiological investigation was undertaken.\n\nResultsDuring the \"Black Friday\" event (25/11/2016), 45 people were pierced (13 by a newly-appointed practitioner). Eleven cases were identified (7 microbiologically-confirmed, 2 probable, and 2 possible). All cases had clinical signs of infection around piercing sites, and five required surgical intervention, with varying degrees of post-operative disfigurement. All confirmed and probable cases had a \"scaffold piercing\" placed with a guide bar by the newly-appointed practitioner. Pseudomonas aeruginosa, indistinguishable at nine-locus variable-number tandem repeat loci, was isolated from four of the confirmed cases, and from pre- and post-flush samples from five separate water taps (three sinks) in the premises. Water samples taken after remedial plumbing work confirmed elimination of Pseudomonas contamination.\n\nConclusionsAlthough high levels of Pseudomonas water contamination and some poor infection control procedures were identified, infection appeared to require additional exposure to an inexperienced practitioner, and the more invasive scaffold piercing. A proactive collaborative approach between piercers and health and environmental officials is required to reduce outbreak risk, particularly when unusually large events are planned.

epidemiology↗