Isolation and characterization of two plasmids in a clinical Acinetobacter nosocomialis strain

BACKGROUND: Acinetobacter species are recognised as important nosocomial pathogens that have become a major cause of invasive opportunistic infections in hospitalised patients. Their clinical significance is largely due to the rapid development of antimicrobial resistance among strains. The development of antibiotic resistance among bacterial strains occurs frequently by the acquisition of resistance genes by gene transfer systems such as bacterial plasmids. METHOD: Multi-antibiotic resistant Acinetobacter nosocomialis strain 178 was isolated from a hospital in Melbourne, Australia. This strain was screened for the presence of plasmids. The two plasmids isolated were sequenced and annotated. RESULTS: Two plasmids isolated from a single clinical Acinetobacter nosocomialis strain were sequenced. One plasmid, designated pRAY*-v3, appears to have evolved via the same lineage as the pRAY plasmid isolated from an Acinetobacter baumannii in South Africa. The other plasmid, designated pAB49-v1, appears to be an evolutionary descendent from a cryptic plasmid isolated from an A. baumannii almost 20 years ago. Both of the plasmid sequences here share a high level of sequence similarity with their ancestors, however differences are noted. CONCLUSION: The isolation of these plasmid-lineages across different decades and continents suggests their global dissemination.