Morphology of Staphylococcus saprophyticus bacteriophages

Isolation and characterization of a potentially novel Siphoviridae phage (vB_SsapS-104) with lytic activity against Staphylococcus saprophyticus isolated from urinary tract infection

Antibiotic resistance is increasing among Staphylococcus saprophyticus strains isolated from urinary tract infection. This necessitates alternative therapies. For this, a lytic phage (vB_SsapS-104) against S. saprophyticus, which formed round and clear plaques on bacterial culture plates, was isolated from hospital wastewater and characterized. Microscopy analysis showed that it had a small head (about 50 nm), tail (about 80 nm), and a collar (about 22 nm in length and 19 nm in width) indicating to be a phage within Siphoviridae family. Phage vB_SsapS-104 showed a large latency period of about 40 min, rapid adsorption rate that was significantly enhanced by MgCl₂ and CaCl₂, and high stability to a wide range of temperatures and pH values. Restriction analyses demonstrated that phage consists of a double-stranded DNA with an approximate genome size of 40 Kb. BLAST results did not show high similarity (megablast) with other previously identified phages. But, in Blastn, similarity with Staphylococcus phages was observed. Phage vB_SsapS-104 represented high anti-bacterial activity against S. saprophyticus isolates in vitro as it was able to lyse 8 of the 9 clinical isolates (%88.8) obtained from a hospital in Gorgan, Iran. It was a S. saprophyticus-specific phage because no lytic activity was observed on some other pathogenic bacteria tested. Therefore, phage vB_SsapS-104 can be considered as a specific virulent phage against of S. saprophyitcus isolated from urinary tract infection. This study provided the partial genomic characterization of S. saprophyticus phage and its application against urinary tract infection associated with S. saprophyticus. This phage also can be considered as a good candidate for a therapeutic alternative in the future.

The Staphylococci phages family: an overview

Due to their crucial role in pathogenesis and virulence, phages of Staphylococcus aureus have been extensively studied. Most of them encode and disseminate potent staphylococcal virulence factors. In addition, their movements contribute to the extraordinary versatility and adaptability of this prominent pathogen by improving genome plasticity. In addition to S. aureus, phages from coagulase-negative Staphylococci (CoNS) are gaining increasing interest. Some of these species, such as S. epidermidis, cause nosocomial infections and are therefore problematic for public health. This review provides an overview of the staphylococcal phages family extended to CoNS phages. At the morphological level, all these phages characterized so far belong to the Caudovirales order and are mainly temperate Siphoviridae. At the molecular level, comparative genomics revealed an extensive mosaicism, with genes organized into functional modules that are frequently exchanged between phages. Evolutionary relationships within this family, as well as with other families, have been highlighted. All these aspects are of crucial importance for our understanding of evolution and emergence of pathogens among bacterial species such as Staphylococci.

Characterization of thirteen Staphylococcus epidermidis and S. saprophyticus bacteriophages

Thirteen bacteriophages of coagulase-negative staphylococci belonging to the Siphoviridae family (morphotype B1) were compared by seroneutralization kinetics, protein profiles, G + C content, DNA size and DNA/DNA hybridization. A previous classification into three morphological groups was confirmed. The Staphylococcus epidermidis phage group, although morphologically homogeneous, was heterogeneous by DNA/DNA hybridization (27 to 100% homology) and seroneutralization kinetics. Two new phage "species", STA1139 (STA for Staphylococcus) and STA1154A, corresponding to two morphological types of S. saprophyticus phages, were identified. Species STA1154A was particularly interesting because the size of its capsid, only 46 nm in diameter, and of its DNA, evaluated as 13 kbp, were smaller than those of other staphylococcal phages.