| Date |
Apr 18, 2013 |
| Speaker |
Dr. Ia Kusradze, Eliava Institute of Bacteriophages, Microbiology and Virology
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| Title |
Characterization of Antibiotic resistant Acinetobacter baumannii Specific Phages for Creation the Therapeutic-preventive Preparation
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| Abstract |
Gram-negative Acinetobacter spp. has become an emerging nosocomial pathogen. There are a lot of clinical manifestations of Acinetobacter infections, including septicaemia, pneumonia, endocarditis, meningitis, wound infections. Antibiotic susceptibility of these strains have been changed since it was isolated first time from clinical sample. To date, strains of A.baumannii have become resistant to almost all currently available antibiotics, including imipenem, that is the drug of choice for treatment of infections caused by Acinetobacter strains. The worldwide spread of MDR strains has renewed interest in phage therapy. Phage preparations are widely used to treat infections caused by different bacteria, however A. baumannii phages have not yet been used as therapeutic tools. The aim of this study was creation of experimental Acinetobacter phage preparation. Early steps of this research were included identification and study of the bacterial strains and investigation of the molecular mechanisms of imipenen resistance in IMP-resistant strains. A total 210 Acinetobacter spp. strains were characterized by using following methods: Etest, DD, PCR, Plasmid transformation. According to the results among 6 IMP-resistant A.baumannii strains, in 5 strains (A.baumannii 3, 4, 5, 6, 9) IMP-resistance was conditioned by blaOXA23like gene located on a plasmid. However IMP-resistant A. baumannii G7 strain (isolated in Georgia) contained OXA-24-like-encoding gene chromosomally and a plasmid bearing the ISAba1 and blaOXA51like genes. Phage research work was done by using classical methods. 5 Acinetobacter phages are characterized in this study, among them 2 phages are serologically relative Myoviridae (vB_Ab-M-G7, vB_Ab-M-40), rest 3 phages (vB_Ab-S-31, vB-Ab-S-14, vB_Ag-S-7) are belonged to Siphoviridae family. Characteristics of these phages (a short latent period (12-40 nim), large burst size (80-200 pfu), stability in different pH ranges (pH=5-11) and in high thermal condition (500)) help made these phages a very promising component for phage therapy. Phage vB_Ab-M-G7 and an animal wound model was used to demonstrate that phage application did not have a toxic effect on wounded rats, phage administration in wound infections caused by A. baumannii strains effectively reduced the number of bacteria isolated from treated animals. Genetical characterization of the phage vB_Ab-M-G7 showed that DNA of this phage contains blaOXA24like gene, despite that no successful transduction was manifested during the experiments, this phage will not be used for treatment remedy. Characterized phages were used for creation phage "cocktail" that could be determined as an experimental phage preparation that is non-toxic, remains stability in different conditions and has wide host range.
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