Molecular characterization of a new efficiently transducing bacteriophage identified in meticillin-resistant Staphylococcus aureus

In Staphylococcus aureus, generalized transduction mediated by temperate bacteriophages represents a highly efficient way of transferring antibiotic resistance genes between strains. In the present study, we identified and characterized in detail a new efficiently transducing bacteriophage of the family Siphoviridae, designated phi JB, which resides as a prophage in the meticillin-resistant S. aureus (MRSA) strain Jevons B. Whole-genome sequencing followed by detailed in silico analysis uncovered a linear dsDNA genome consisting of 43 012 bp and comprising 70 ORFs, of which similar to 40 encoded proteins with unknown function. A global genome alignment of phi JB and other efficiently transducing phages phi 11, phi 53, phi 80, phi 80 alpha and phi NM4 showed a high degree of homology with phi NM4 and substantial differences with regard to other phages. Using a model transduction system with a well-defined donor and recipient, phi JB transferred the tetracycline resistance plasmid pT181 and a penicillinase plasmid with outstanding frequencies, beating most of the above-mentioned phages by an order of magnitude. Moreover, phi JB demonstrated high frequencies of transferring antibiotic resistance plasmids even upon induction from a lysogenic donor strain. Considering such transducing potential, phi JB and related bacteriophages may serve as a suitable tool for elucidating the nature of transduction and its contribution to the spread of antibiotic resistance genes in naturally occurring MRSA populations.