Staphylococcus epidermidis is a leading opportunistic pathogen causing nosocomial infections that is notable for its ability to form a biofilm and for its high rates of antibiotic resistance. It serves as a reservoir of multiple antimicrobial resistance genes that spread among the staphylococcal population by horizontal gene transfer such as transduction. While phage-mediated transduction is well studied in Staphylococcus aureus, S. epidermidis transducing phages have not been described in detail yet. Here, we report the characteristics of four phages, 27, 48, 456, and 459, previously used for S. epidermidis phage typing, and the newly isolated phage E72, from a clinical S. epidermidis strain. The phages, classified in the family Siphoviridae and genus Phietavirus, exhibited an S. epidermidis-specific host range, and together they infected 49% of the 35 strains tested. A whole-genome comparison revealed evolutionary relatedness to transducing S. aureus phietaviruses. In accordance with this, all the tested phages were capable of transduction with high frequencies up to 10-4 among S. epidermidis strains from different clonal complexes. Plasmids with sizes from 4 to 19 kb encoding resistance to streptomycin, tetracycline, and chloramphenicol were transferred. We provide here the first evidence of a phage-inducible chromosomal island transfer in S. epidermidis Similarly to S. aureus pathogenicity islands, the transfer was accompanied by phage capsid remodeling; however, the interfering protein encoded by the island was distinct. Our findings underline the role of S. epidermidis temperate phages in the evolution of S. epidermidis strains by horizontal gene transfer, which can also be utilized for S. epidermidis genetic studies.IMPORTANCE Multidrug-resistant strains of S. epidermidis emerge in both nosocomial and livestock environments as the most important pathogens among coagulase-negative staphylococcal species. The study of transduction by phages is essential to understanding how virulence and antimicrobial resistance genes spread in originally commensal bacterial populations. In this work, we provide a detailed description of transducing S. epidermidis phages. The high transduction frequencies of antimicrobial resistance plasmids and the first evidence of chromosomal island transfer emphasize the decisive role of S. epidermidis phages in attaining a higher pathogenic potential of host strains. To date, such importance has been attributed only to S. aureus phages, not to those of coagulase-negative staphylococci. This study also proved that the described transducing bacteriophages represent valuable genetic modification tools in S. epidermidis strains where other methods for gene transfer fail.

• Keywords
• Staphylococcus epidermidis, antibiotic resistance, bacteriophages, horizontal gene transfer, pathogenicity islands, transduction,
• MeSH
• Anti-Bacterial Agents pharmacology   MeSH
• Drug Resistance, Bacterial genetics   MeSH
• Genomic Islands genetics   MeSH
• Humans MeSH
• Plasmids genetics   MeSH
• Staphylococcus Phages classification   drug effects   genetics   MeSH
• Staphylococcal Infections microbiology   MeSH
• Staphylococcus epidermidis drug effects   virology   MeSH
• Transduction, Genetic * MeSH
• Virulence MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Anti-Bacterial Agents MeSH

Alphaproteobacteria, which are the most abundant microorganisms of temperate oceans, produce phage-like particles called gene transfer agents (GTAs) that mediate lateral gene exchange. However, the mechanism by which GTAs deliver DNA into cells is unknown. Here we present the structure of the GTA of Rhodobacter capsulatus (RcGTA) and describe the conformational changes required for its DNA ejection. The structure of RcGTA resembles that of a tailed phage, but it has an oblate head shortened in the direction of the tail axis, which limits its packaging capacity to less than 4,500 base pairs of linear double-stranded DNA. The tail channel of RcGTA contains a trimer of proteins that possess features of both tape measure proteins of long-tailed phages from the family Siphoviridae and tail needle proteins of short-tailed phages from the family Podoviridae. The opening of a constriction within the RcGTA baseplate enables the ejection of DNA into bacterial periplasm.

• MeSH
• Bacteriophages genetics   physiology   ultrastructure   MeSH
• DNA, Bacterial genetics   MeSH
• Cryoelectron Microscopy MeSH
• Gene Transfer, Horizontal MeSH
• Gene Expression Regulation, Bacterial MeSH
• Rhodobacter capsulatus genetics   virology   MeSH
• Siphoviridae genetics   physiology   ultrastructure   MeSH
• Gene Transfer Techniques * MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• DNA, Bacterial MeSH

The properties of staphylococcal phages from the Siphoviridae, Podoviridae, and Myoviridae families were monitored using capillary electrophoretic methods on fused-silica capillaries with different morphology of surface roughness. Isoelectric points of the examined phages were determined by capillary isoelectric focusing in the original, smooth fused-silica capillary, and they ranged from 3.30 to 3.85. For capillary electrophoresis of phages, fused-silica capillaries with the "pock" and "cone" roughened surface types were prepared by etching a part of the capillary with supercritical water. The best resolution of the individual phages (to range from 3.2 to 4.6) was achieved with the "cone" surface-type fused-silica capillary. Direct application of phage K1/420 at the infection site, represented by human plasma or full blood spiked with Staphylococcus aureus, was on-line monitored by micellar electrokinetic chromatography. The phage particles were dynamically adhered onto the roughened surface of the capillary from 10 μL of the prepared sample at the optimized flow rate of 6.5 μL min-1. The limit of detection was determined to be 104 phage particles. The linearity of the calibration lines was characterized by the regression coefficient, R2 = 0.998. The relative standard deviation (RSD) of the peak area, calculated from ten independent measurements, was (±) 2%. After analysis, viability of the detected phages was verified by the modified "double-layer drop assay" method, and collected phage fractions were simultaneously off-line analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Graphical abstract.

• Keywords
• Capillary electrophoresis, MALDI-TOF mass spectrometry, Nano-etched fused-silica capillary, Phage propagation, Staphylococcal bacteriophages, Supercritical water,
• MeSH
• Bacteriophages pathogenicity   MeSH
• Humans MeSH
• Blood Specimen Collection instrumentation   MeSH
• Silicon Dioxide chemistry   MeSH
• Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization methods   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Silicon Dioxide MeSH

Lytic bacteriophages are valuable therapeutic agents against bacterial infections. There is continual effort to obtain new phages to increase the effectivity of phage preparations against emerging phage-resistant strains. Here we described the genomic diversity of spontaneous host-range mutants of kayvirus 812. Five mutant phages were isolated as rare plaques on phage-resistant Staphylococcus aureus strains. The host range of phage 812-derived mutants was 42% higher than the wild type, determined on a set of 186 methicillin-resistant S. aureus strains representing the globally circulating human and livestock-associated clones. Comparative genomics revealed that single-nucleotide polymorphisms from the parental phage 812 population were fixed in next-step mutants, mostly in genes for tail and baseplate components, and the acquired point mutations led to diverse receptor binding proteins in the phage mutants. Numerous genome changes associated with rearrangements between direct repeat motifs or intron loss were found. Alterations occurred in host-takeover and terminal genomic regions or the endolysin gene of mutants that exhibited the highest lytic activity, which implied various mechanisms of overcoming bacterial resistance. The genomic data revealed that Kayvirus spontaneous mutants are free from undesirable genes and their lytic properties proved their suitability for rapidly updating phage therapeutics.

• MeSH
• Drug Resistance, Bacterial MeSH
• Bacteriophages genetics   MeSH
• Genome Size MeSH
• Genome, Viral MeSH
• Genomics MeSH
• Polymorphism, Single Nucleotide MeSH
• Methicillin pharmacology   MeSH
• Mutation * MeSH
• Staphylococcus aureus growth & development   virology   MeSH
• Base Composition MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Methicillin MeSH