Sam Limsuwannarot

All Publications

• A compensatory RNase E variation increases Iron Piracy and Virulence in multidrug-resistant Pseudomonas aeruginosa during Macrophage infection PLOS PATHOGENS Vaillancourt, M., Galdino, A., Limsuwannarot, S. P., Celedonio, D., Dimitrova, E., Broerman, M., Bresee, C., Doi, Y., Lee, J. S., Parks, W. C., Jorth, P. 2023; 19 (4): e1010942

  Abstract

  During chronic cystic fibrosis (CF) infections, evolved Pseudomonas aeruginosa antibiotic resistance is linked to increased pulmonary exacerbations, decreased lung function, and hospitalizations. However, the virulence mechanisms underlying worse outcomes caused by antibiotic resistant infections are poorly understood. Here, we investigated evolved aztreonam resistant P. aeruginosa virulence mechanisms. Using a macrophage infection model combined with genomic and transcriptomic analyses, we show that a compensatory mutation in the rne gene, encoding RNase E, increased pyoverdine and pyochelin siderophore gene expression, causing macrophage ferroptosis and lysis. We show that iron-bound pyochelin was sufficient to cause macrophage ferroptosis and lysis, however, apo-pyochelin, iron-bound pyoverdine, or apo-pyoverdine were insufficient to kill macrophages. Macrophage killing could be eliminated by treatment with the iron mimetic gallium. RNase E variants were abundant in clinical isolates, and CF sputum gene expression data show that clinical isolates phenocopied RNase E variant functions during macrophage infection. Together these data show how P. aeruginosa RNase E variants can cause host damage via increased siderophore production and host cell ferroptosis but may also be targets for gallium precision therapy.

  View details for DOI 10.1371/journal.ppat.1010942

  View details for Web of Science ID 000967513900002

  View details for PubMedID 37027441

  View details for PubMedCentralID PMC10115287

• Pseudomonas aeruginosa mexR and mexEF Antibiotic Efflux Pump Variants Exhibit Increased Virulence ANTIBIOTICS-BASEL Vaillancourt, M., Limsuwannarot, S. P., Bresee, C., Poopalarajah, R., Jorth, P. 2021; 10 (10)

  Abstract

  Antibiotic-resistant Pseudomonas aeruginosa infections are the primary cause of mortality in people with cystic fibrosis (CF). Yet, it has only recently become appreciated that resistance mutations can also increase P. aeruginosa virulence, even in the absence of antibiotics. Moreover, the mechanisms by which resistance mutations increase virulence are poorly understood. In this study we tested the hypothesis that mutations affecting efflux pumps can directly increase P. aeruginosa virulence. Using genetics, physiological assays, and model infections, we show that efflux pump mutations can increase virulence. Mutations of the mexEF efflux pump system increased swarming, rhamnolipid production, and lethality in a mouse infection model, while mutations in mexR that increased expression of the mexAB-oprM efflux system increased virulence during an acute murine lung infection without affecting swarming or rhamnolipid gene expression. Finally, we show that an efflux pump inhibitor, which represents a proposed novel treatment approach for P. aeruginosa, increased rhamnolipid gene expression in a dose-dependent manner. This finding is important because rhamnolipids are key virulence factors involved in dissemination through epithelial barriers and cause neutrophil necrosis. Together, these data show how current and proposed future anti-Pseudomonal treatments may unintentionally make infections worse by increasing virulence. Therefore, treatments that target efflux should be pursued with caution.

  View details for DOI 10.3390/antibiotics10101164

  View details for Web of Science ID 000713512100001

  View details for PubMedID 34680745

  View details for PubMedCentralID PMC8532662