Cheating by type 3 secretion system-negative Pseudomonas aeruginosa during pulmonary infection
The opportunistic pathogen Pseudomonas aeruginosa expresses a type 3 secretion system (T3SS) strongly associated with bacterial virulence in murine models and human patients. T3SS effectors target host innate immune mechanisms, and T3SS-defective mutants are cleared more efficiently than T3SS-positive bacteria by an immunocompetent host. Nonetheless, T3SS-negative isolates are recovered from many patients with documented P. aeruginosa infections, leading us to test whether T3SS-negative strains could have a selective advantage during in vivo infection. Mice were infected with mixtures of T3SS-positive WT P. aeruginosa plus isogenic T3SS-OFF or constitutively T3SS-ON mutants. Relative fitness of bacteria in this acute pneumonia model was reflected by the competitive index of mutants relative to WT. T3SS-OFF strains outcompeted WT PA103 in vivo, whereas a T3SS-ON mutant showed decreased fitness compared with WT. In vitro growth rates of WT and T3SS-OFF bacteria were determined under T3SS-inducing conditions and did not differ significantly. Increased fitness of T3SS-OFF bacteria was no longer observed at high ratios of T3SS-OFF to WT, a feature characteristic of bacterial cheaters. Cheating by T3SS-OFF bacteria occurred only when T3SS-positive bacteria expressed the phospholipase A2 effector Exotoxin U (ExoU). T3SS-OFF bacteria showed no fitness advantage in competition experiments carried out in immunodeficient MyD88-knockout mice or in neutrophil-depleted animals. Our findings indicate that T3SS-negative isolates benefit from the public good provided by ExoU-mediated killing of recruited innate immune cells. Whether this transient increase in fitness observed for T3SS-negative strains in mice contributes to the observed persistence of T3SS-negative isolates in humans is of ongoing interest.
| Medienart: |
E-Artikel |
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| Erscheinungsjahr: |
2014 |
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| Erschienen: |
2014 |
| Enthalten in: |
Zur Gesamtaufnahme - volume:111 |
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| Enthalten in: |
Proceedings of the National Academy of Sciences of the United States of America - 111(2014), 21 vom: 27. Mai, Seite 7801-6 |
| Sprache: |
Englisch |
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| Beteiligte Personen: |
Czechowska, Kamila [VerfasserIn] |
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| Links: |
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| Themen: |
Bacterial Secretion Systems |
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| Anmerkungen: |
Date Completed 02.09.2014 Date Revised 21.10.2021 published: Print-Electronic Citation Status MEDLINE |
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| doi: |
10.1073/pnas.1400782111 |
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| funding: |
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| Förderinstitution / Projekttitel: |
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| PPN (Katalog-ID): |
NLM238191559 |
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| 520 | |a The opportunistic pathogen Pseudomonas aeruginosa expresses a type 3 secretion system (T3SS) strongly associated with bacterial virulence in murine models and human patients. T3SS effectors target host innate immune mechanisms, and T3SS-defective mutants are cleared more efficiently than T3SS-positive bacteria by an immunocompetent host. Nonetheless, T3SS-negative isolates are recovered from many patients with documented P. aeruginosa infections, leading us to test whether T3SS-negative strains could have a selective advantage during in vivo infection. Mice were infected with mixtures of T3SS-positive WT P. aeruginosa plus isogenic T3SS-OFF or constitutively T3SS-ON mutants. Relative fitness of bacteria in this acute pneumonia model was reflected by the competitive index of mutants relative to WT. T3SS-OFF strains outcompeted WT PA103 in vivo, whereas a T3SS-ON mutant showed decreased fitness compared with WT. In vitro growth rates of WT and T3SS-OFF bacteria were determined under T3SS-inducing conditions and did not differ significantly. Increased fitness of T3SS-OFF bacteria was no longer observed at high ratios of T3SS-OFF to WT, a feature characteristic of bacterial cheaters. Cheating by T3SS-OFF bacteria occurred only when T3SS-positive bacteria expressed the phospholipase A2 effector Exotoxin U (ExoU). T3SS-OFF bacteria showed no fitness advantage in competition experiments carried out in immunodeficient MyD88-knockout mice or in neutrophil-depleted animals. Our findings indicate that T3SS-negative isolates benefit from the public good provided by ExoU-mediated killing of recruited innate immune cells. Whether this transient increase in fitness observed for T3SS-negative strains in mice contributes to the observed persistence of T3SS-negative isolates in humans is of ongoing interest | ||
| 650 | 4 | |a Journal Article | |
| 650 | 4 | |a Research Support, N.I.H., Extramural | |
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| 700 | 1 | |a Kazmierczak, Barbara I |e verfasserin |4 aut | |
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