Whole genome pyrosequencing of the epidemic multidrug-resistant Acinetobacter baumannii European clone II

Abstract number: P921

Iacono M., Villa L., Fortini D., Bordoni R., Imperi F., Bonnal R., Sicheritz-Ponten T., De Bellis G., Visca P., Cassone A., Carattoli A.

Objectives: the whole genomic DNA sequence was determined for an epidemic Acinetobacter baumannii strain (ACICU), belonging to the European clone II and carrying the plasmid-mediated blaOXA58 gene, implicated in carbapenem resistance. We compared the ACICU genome with that of A. baumannii ATCC 17978 and of Acinetobacter baylyi ADP-1, with the aim of identifying novel traits related to virulence, drug resistance and pathogenesis.

Methods: the genome was sequenced by high-density pyrosequencing and characterised for both genes coding and non coding. The genome was also analysed for lateral gene transfer.

Results:A. baumannii ACICU strain contains a single circular cromosome of 3,904,116 bp and two plasmids (ACICUp1 and ACICUp2) of 28,279 and 64,366 bp, respectively; the chromosome contains 3,758 genes. (3,670 CDSs, 64 tRNA genes 8 rRNA operons).

Genome comparison showed 86.4% of syntheny versus the reference A. baumannii ATCC 17978 strain and 14.81% versus A. baylyi ADP-1.

36 putative alien islands (pAs) are detected in the ACICU genome: 24 of them were previously described in the ATCC 17978 genome, 4 identified by the lateral gene transfer analysis in both ATCC and ACICU and 8 completely new, being absent in the ATCC 17978 genome

21 putative TonB-dependent outer membrane receptors were found in the ACICU genome, likely involved in iron uptake. ACICU has a conspicuous number of transporters belonging to different superfamilies, the number of which for unit length of genome (76.2) is much higher than that of ATCC 17978 (57.2) and ADP-1 (62.5), and similar to values reported for some pseudomonads.

Moreover, an antibiotic resistant island, AbaR2, was identified but it is shorter than the AbaR1 previously described in the multiresistant A. baumannii AYE strain.

Conclusion: the pathogenicity of A. baumannii is poorly understood and this organism is commonly regarded as a low-virulence bacterium, in spite of the severity of infections it causes. pAs in ACICU genome are partly divergent from those described in ATCC 17978, by acquisition of several interesting genes encoding membrane transporters, drug resistance and virulence trait for invasion and adherence. Four clusters of acquired genes were identified associated to putative phages. Since phage-related pathogenicity islands have been identified in the genome of important pathogens, the presence of unknown sequences poses the question of whether they could be involved in pathogenicity.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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