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Differential Role of the T6SS in Acinetobacter baumannii Virulence.

Repizo GD, Gagné S, Foucault-Grunenwald ML, Borges V, Charpentier X, Limansky AS, Gomes JP, Viale AM, Salcedo SP - PLoS ONE (2015)

Bottom Line: The T6SS genomic locus is present and was actively transcribed in all of the above strains.In addition, DSM30011 was able to outcompete ATCC17978 as well as Pseudomonas aeruginosa and Klebsiella pneumoniae, bacterial pathogens relevant in mixed nosocomial infections.Finally, we found that the T6SS of DSM30011 is required for host colonization of the model organism Galleria mellonella suggesting that this system could play an important role in A. baumannii virulence in a strain-specific manner.

View Article: PubMed Central - PubMed

Affiliation: Bases Moléculaires et Structurales des Systèmes Infectieux, CNRS UMR 5086, Université Lyon 1, Institut de Biologie et Chimie des Protéines, Lyon, France.

ABSTRACT
Gram-negative bacteria, such as Acinetobacter baumannii, are an increasing burden in hospitals worldwide with an alarming spread of multi-drug resistant (MDR) strains. Herein, we compared a type strain (ATCC17978), a non-clinical isolate (DSM30011) and MDR strains of A. baumannii implicated in hospital outbreaks (Ab242, Ab244 and Ab825), revealing distinct patterns of type VI secretion system (T6SS) functionality. The T6SS genomic locus is present and was actively transcribed in all of the above strains. However, only the A. baumannii DSM30011 strain was capable of killing Escherichia coli in a T6SS-dependent manner, unlike the clinical isolates, which failed to display an active T6SS in vitro. In addition, DSM30011 was able to outcompete ATCC17978 as well as Pseudomonas aeruginosa and Klebsiella pneumoniae, bacterial pathogens relevant in mixed nosocomial infections. Finally, we found that the T6SS of DSM30011 is required for host colonization of the model organism Galleria mellonella suggesting that this system could play an important role in A. baumannii virulence in a strain-specific manner.

No MeSH data available.


Related in: MedlinePlus

Competition between A. baumannii DSM30011 and nosocomial pathogens.Survival of A) different P. aeruginosa strains and C) rifampicin-resistant K. pseumoniae after incubation in growth medium (control) or with A. baumannii DSM30011 wild type, tssM deleted or complemented strains at a 10:1 ratio. Pseudomonas strains were selected with Pseudomonas Isolation Agar (PIA) media. Quantification is shown in B) and D), in which data are expressed as means ± SDM plotted in a logarithmic scale to visualize experimental variation from 3 independent experiments.
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pone.0138265.g005: Competition between A. baumannii DSM30011 and nosocomial pathogens.Survival of A) different P. aeruginosa strains and C) rifampicin-resistant K. pseumoniae after incubation in growth medium (control) or with A. baumannii DSM30011 wild type, tssM deleted or complemented strains at a 10:1 ratio. Pseudomonas strains were selected with Pseudomonas Isolation Agar (PIA) media. Quantification is shown in B) and D), in which data are expressed as means ± SDM plotted in a logarithmic scale to visualize experimental variation from 3 independent experiments.

Mentions: As hospital-acquired infections are often the result of colonization of patients with a mixed population of bacteria we analysed the ability of A. baumannii to kill Klebsiella pneumoniae and Pseudomonas aeruginosa, two other nosocomial pathogens associated with respiratory infections. For these experiments, we focused on the DSM30011 that showed the strongest ability to outcompete E. coli. We found that in our killing conditions, DSM30011 efficiently outcompeted the P. aeruginosa PAK strain in a T6SS-dependent manner (Fig 5A and 5B), when present at a ratio of 10:1 against its prey. This was also observed for other P. aeruginosa strains, namely PA14 and PA7 (data not shown). More interestingly, the DSM30011 could also outcompete a PAK retS mutant in which the T6SS is active [12] and data not shown, [28]. In addition, killing of K. pneumoniae was also observed (Fig 5C and 5D). In all cases, we consistently observed enhanced killing for the complemented strain ΔtssMptssM confirming T6SS dependency (Fig 5B and 5D). Together these data show that the A. baumannii DSM30011 strain has the ability to kill other nosocomial pathogens.


Differential Role of the T6SS in Acinetobacter baumannii Virulence.

Repizo GD, Gagné S, Foucault-Grunenwald ML, Borges V, Charpentier X, Limansky AS, Gomes JP, Viale AM, Salcedo SP - PLoS ONE (2015)

Competition between A. baumannii DSM30011 and nosocomial pathogens.Survival of A) different P. aeruginosa strains and C) rifampicin-resistant K. pseumoniae after incubation in growth medium (control) or with A. baumannii DSM30011 wild type, tssM deleted or complemented strains at a 10:1 ratio. Pseudomonas strains were selected with Pseudomonas Isolation Agar (PIA) media. Quantification is shown in B) and D), in which data are expressed as means ± SDM plotted in a logarithmic scale to visualize experimental variation from 3 independent experiments.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4581634&req=5

pone.0138265.g005: Competition between A. baumannii DSM30011 and nosocomial pathogens.Survival of A) different P. aeruginosa strains and C) rifampicin-resistant K. pseumoniae after incubation in growth medium (control) or with A. baumannii DSM30011 wild type, tssM deleted or complemented strains at a 10:1 ratio. Pseudomonas strains were selected with Pseudomonas Isolation Agar (PIA) media. Quantification is shown in B) and D), in which data are expressed as means ± SDM plotted in a logarithmic scale to visualize experimental variation from 3 independent experiments.
Mentions: As hospital-acquired infections are often the result of colonization of patients with a mixed population of bacteria we analysed the ability of A. baumannii to kill Klebsiella pneumoniae and Pseudomonas aeruginosa, two other nosocomial pathogens associated with respiratory infections. For these experiments, we focused on the DSM30011 that showed the strongest ability to outcompete E. coli. We found that in our killing conditions, DSM30011 efficiently outcompeted the P. aeruginosa PAK strain in a T6SS-dependent manner (Fig 5A and 5B), when present at a ratio of 10:1 against its prey. This was also observed for other P. aeruginosa strains, namely PA14 and PA7 (data not shown). More interestingly, the DSM30011 could also outcompete a PAK retS mutant in which the T6SS is active [12] and data not shown, [28]. In addition, killing of K. pneumoniae was also observed (Fig 5C and 5D). In all cases, we consistently observed enhanced killing for the complemented strain ΔtssMptssM confirming T6SS dependency (Fig 5B and 5D). Together these data show that the A. baumannii DSM30011 strain has the ability to kill other nosocomial pathogens.

Bottom Line: The T6SS genomic locus is present and was actively transcribed in all of the above strains.In addition, DSM30011 was able to outcompete ATCC17978 as well as Pseudomonas aeruginosa and Klebsiella pneumoniae, bacterial pathogens relevant in mixed nosocomial infections.Finally, we found that the T6SS of DSM30011 is required for host colonization of the model organism Galleria mellonella suggesting that this system could play an important role in A. baumannii virulence in a strain-specific manner.

View Article: PubMed Central - PubMed

Affiliation: Bases Moléculaires et Structurales des Systèmes Infectieux, CNRS UMR 5086, Université Lyon 1, Institut de Biologie et Chimie des Protéines, Lyon, France.

ABSTRACT
Gram-negative bacteria, such as Acinetobacter baumannii, are an increasing burden in hospitals worldwide with an alarming spread of multi-drug resistant (MDR) strains. Herein, we compared a type strain (ATCC17978), a non-clinical isolate (DSM30011) and MDR strains of A. baumannii implicated in hospital outbreaks (Ab242, Ab244 and Ab825), revealing distinct patterns of type VI secretion system (T6SS) functionality. The T6SS genomic locus is present and was actively transcribed in all of the above strains. However, only the A. baumannii DSM30011 strain was capable of killing Escherichia coli in a T6SS-dependent manner, unlike the clinical isolates, which failed to display an active T6SS in vitro. In addition, DSM30011 was able to outcompete ATCC17978 as well as Pseudomonas aeruginosa and Klebsiella pneumoniae, bacterial pathogens relevant in mixed nosocomial infections. Finally, we found that the T6SS of DSM30011 is required for host colonization of the model organism Galleria mellonella suggesting that this system could play an important role in A. baumannii virulence in a strain-specific manner.

No MeSH data available.


Related in: MedlinePlus