Petr Kašpárek

Identification of bacteriophage types and their carriage in Staphylococcus aureus.

Summary.Conserved genomic sequences distinctive of Staphylococcus aureus phage types 3A, 11, 77, 187 and Twort, representative of phage serogroups A, B, F, L and D, were identified and characterized. PCR primers designed for the above sequences were used for development of a multiplex PCR assay which enabled us not only to classify all phages of the International Typing Set plus 16 additional phages, but also to detect prophages in S. aureus genomes. One to four different prophages were unambiguously detected in experimentally lysogenized S. aureus strains, and substantial variation in prophage content was found in 176 S. aureus clinical strains of different provenance. In addition, by using a comparative genomics approach, all the prophages in the S. aureus genomes sequenced to date could be revealed and classified.

Genome rearrangements in host-range mutants of the polyvalent staphylococcal bacteriophage 812.

Mutations extended the host range of the polyvalent bacteriophage 812 of the familyMyoviridae in up to 95 % ofStaphylococcus aureus strains and 43 % of strains of different coagulase-positive and -negativeStaphylococcus species. Mutational changes in the genome of several host-range mutants of phage 812 were identified. Host-range mutant 812F1 harbors a deletion in endolysin gene that arose together with intron excision. Four mutants (812i, 812b, 812p, 812F3) harbor deletion in the structural geneorf8 that results from a genome rearrangement associated with intron insertion. This rearrangement was also detected in the genome of the closely related phages U16 and ϕ131. Another intron was discovered in therecA812 gene in these four mutants. An insertion was found in a non-coding region of the restriction fragmentPstI-O of three mutants (812b, 812F3, 812g) and phages U16 and ϕ131. The above results contribute to the explanation of genetic factors affecting the host range of polyvalent staphylococcal bacteriophages.