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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

Ability of different A. baumannii strains to out-compete E. coli.A) Comparative analysis between the T6SS gene loci of A. baumannii ATCC17978, DSM30011 and clinical strains. Black arrows indicate genes specific to Acinetobacter. B) Survival of DH5α E. coli after incubation in growth medium (control) or with A. baumannii ATCC17978 or DSM30011 at the indicated A. baumannii: E. coli ratios (top panel). Bottom panel corresponds to survival of apramycin-resistant DH5α E. coli after incubation in growth medium (control) or with Ab242, Ab244 or Ab825 strains at the indicated ratios. Images correspond to one representative experiment from a minimum of three independent assays quantified in C) to visualize experimental variation, expressed as means ± SDM plotted in a logarithmic scale.
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pone.0138265.g001: Ability of different A. baumannii strains to out-compete E. coli.A) Comparative analysis between the T6SS gene loci of A. baumannii ATCC17978, DSM30011 and clinical strains. Black arrows indicate genes specific to Acinetobacter. B) Survival of DH5α E. coli after incubation in growth medium (control) or with A. baumannii ATCC17978 or DSM30011 at the indicated A. baumannii: E. coli ratios (top panel). Bottom panel corresponds to survival of apramycin-resistant DH5α E. coli after incubation in growth medium (control) or with Ab242, Ab244 or Ab825 strains at the indicated ratios. Images correspond to one representative experiment from a minimum of three independent assays quantified in C) to visualize experimental variation, expressed as means ± SDM plotted in a logarithmic scale.

Mentions: The genomes of the DSM30011 and the MDR strains were sequenced and analysed for T6SS genes. This search revealed the presence in the genome of each of these strains a single cluster of 18 T6SS genes similar to that previously described in other Acinetobacter species [10,11], from which four are specific to the genus (Fig 1A, black arrows, see also S3 Table). The DNA sequence of the tss loci of the Ab242/244/825 clinical strains were identical between them. Sequence comparison analyses indicated that the homologous polypeptides encoded by 17 out of the 18 genes of the tss clusters of DSM30011, ATCC17978, and the A. baumannii clinical strains shared an overall identity of >97% between them. The least homologous polypeptides encoded by DSM_11700/A1S_1292/Ab244_01 (Fig 1A) shared an identity of ~81% and all contained a predicted signal peptide at their N-terminal regions, but no homology could be revealed to protein domains described in databases (data not shown).


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)

Ability of different A. baumannii strains to out-compete E. coli.A) Comparative analysis between the T6SS gene loci of A. baumannii ATCC17978, DSM30011 and clinical strains. Black arrows indicate genes specific to Acinetobacter. B) Survival of DH5α E. coli after incubation in growth medium (control) or with A. baumannii ATCC17978 or DSM30011 at the indicated A. baumannii: E. coli ratios (top panel). Bottom panel corresponds to survival of apramycin-resistant DH5α E. coli after incubation in growth medium (control) or with Ab242, Ab244 or Ab825 strains at the indicated ratios. Images correspond to one representative experiment from a minimum of three independent assays quantified in C) to visualize experimental variation, expressed as means ± SDM plotted in a logarithmic scale.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0138265.g001: Ability of different A. baumannii strains to out-compete E. coli.A) Comparative analysis between the T6SS gene loci of A. baumannii ATCC17978, DSM30011 and clinical strains. Black arrows indicate genes specific to Acinetobacter. B) Survival of DH5α E. coli after incubation in growth medium (control) or with A. baumannii ATCC17978 or DSM30011 at the indicated A. baumannii: E. coli ratios (top panel). Bottom panel corresponds to survival of apramycin-resistant DH5α E. coli after incubation in growth medium (control) or with Ab242, Ab244 or Ab825 strains at the indicated ratios. Images correspond to one representative experiment from a minimum of three independent assays quantified in C) to visualize experimental variation, expressed as means ± SDM plotted in a logarithmic scale.
Mentions: The genomes of the DSM30011 and the MDR strains were sequenced and analysed for T6SS genes. This search revealed the presence in the genome of each of these strains a single cluster of 18 T6SS genes similar to that previously described in other Acinetobacter species [10,11], from which four are specific to the genus (Fig 1A, black arrows, see also S3 Table). The DNA sequence of the tss loci of the Ab242/244/825 clinical strains were identical between them. Sequence comparison analyses indicated that the homologous polypeptides encoded by 17 out of the 18 genes of the tss clusters of DSM30011, ATCC17978, and the A. baumannii clinical strains shared an overall identity of >97% between them. The least homologous polypeptides encoded by DSM_11700/A1S_1292/Ab244_01 (Fig 1A) shared an identity of ~81% and all contained a predicted signal peptide at their N-terminal regions, but no homology could be revealed to protein domains described in databases (data not shown).

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