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Temperate bacteriophages of Staphylococcus aureus play a major role in spreading mobile genetic elements among bacterial strains by transduction. This phenomenon leads to rapid evolution of the strains due to acquisition of antibiotic resistance genes and virulence factors. As a result, multiresistant strains of S. aureus insensitive to a broad spectrum of antimicrobial agents pose a significant threat to global health care system. In this work we characterized in detail a new, very efficiently transducing bacteriophage from methicillin-resistant S. aureus (MRSA) strain Jevons B. The bacteriophage, designated JB, was isolated from its host strain by UV induction to high titre and the phage lysate was used for transduction experiments. Whole-genome pyrosequencing of phage’s DNA was performed on Roche 454 GS FLX Titanium. Further, the DNA sequence was analyzed in silico to predict genes, regulatory elements, gene products’ functions and to find out homologies with other phage genes. Transmission electron microscopy was employed to visualize the shape of virions. Based on transduction experiments with laboratory S. aureus strains, and also the strains belonging to USA300 clone, we discovered that the phage efficiently transfers antibiotic resistance plasmids both directly after induction as well as after its propagation on donor strains. Restriction profile of phage’s DNA markedly differs from profiles of other serogroup B transducing S. aureus bacteriophages. DNA sequencing followed by in silico analysis explored the genome length of 43 kb and the presence of 70 ORF. By searching for homologies with other phages, we found out that the phage is very similar to phage NM4 present in the S. aureus Newman strain. Since both phages can be found as prophages in naturally occuring MRSA strains, they may serve as efficient vectors for the spread of antibiotic resistance and virulence genes in populations of staphylococci.

Seven coagulase-negative, oxidase-negative and novobiocin-susceptible staphylococci assigned tentatively as Staphylococcus petrasii were investigated in this study in order to elucidate their taxonomic position. All strains were initially shown to form a genetically homogeneous group separated from remaining species of the genus Staphylococcus by using a repetitive sequence-based PCR fingerprinting with the (GTG)5 primer. Phylogenetic analysis based on 16S rRNA gene, hsp60, rpoB, dnaJ, gap and tuf sequences showed that the group is closely related to Staphylococcus petrasii but separated from the three hitherto known subspecies, S. petrasii subsp. petrasii, S. petrasii subsp. croceilyticus and S. petrasii subsp. jettensis. Further investigation using automated ribotyping, MALDI-TOF mass spectrometry, fatty acid methyl ester analysis, DNA–DNA hybridization and extensive biotyping confirmed that the analysed group represents a novel subspecies within S. petrasii, for which the name Staphylococcus petrasii subsp. pragensis subsp. nov. is proposed. The type strain is NRL/St 12/356T ( = CCM 8529T = LMG 28327T).