S. epidermidis is currently described as one of the more encountered nosocomial pathogen, namely within biofilms. In this work, the complete genomes of two already described phages phi-IPLA5 (virulent phage) and phi-IPLA7 (temperate phage) have been sequenced, fully-annotated and compared with other staphylococcal phages already described. Lytic genes have been encountered, and genes encoding putative depolymerase activities have been identified. Finally a S. epidermidis strain collection has been analyzed for the presence of prophage using a multiplex PCR assay. Continue reading
Genomic characterization of two Staphylococcus epidermidis bacteriophages with anti-biofilm potential
Isolation and characterization of ZZ1, a novel lytic phage that infects Acinetobacter baumanii clinical isolates
A. baumanii is a bacteria responsible for innumerous nosocomial infections being resistant to common antibiotics. In this particular study, clinical isolates were used to screen phages from water samples.
Using fishpond water, strain AB09V served as indicator for the presence of phage cause it was the only strain where clear plaques with were formed (1-2 mm of diameter).
TEM micrographs showed that the phage possessed an icosahedral head and a long contractile tail, being a member of the Myoviridae family. Additionally, it was observed that phages has a rapid adsorption to the cell, cause after 5 min of infection a lot of ghost particles appeared.
When bacteriophages are used for clinical purposes a high level of purification and infectivity is required. There are several methods developed for phage purification, however chromatographic methods are generally developed for protein purification. Columns for protein purification have adjustable pore sizes according to the protein size. Chromatographic columns for phage purification should have large pore diameters in order to allow phages to have a larger binding surface area. Convective interaction media (CIM) methacrylate monoliths have recently shown to be efficient for phage purification and concentration. In this study, a purification method for Mycobacteriophage D29 was developed using CIM monolithic columns.
Proteus mirabilis is a common urinary tract infectious agent. This organism has the ability to alkalinize the urine and under this condition forms crystals (e.g. magnesium phosphate) and adheres to catheter surfaces forming biofilms.
It has been shown that depending on environmental conditions biofilms structure can vary. Consequently, in this study the authors wanted to observe the differences on Proteus mirabilis biofilm structures when grown in artificial urine (AU) and in a nutrient-rich laboratory media, such as LB broth.
This publication compiles a list of advantages and disadvantages of phage therapy.
The authors suggest as the bigger advantages of phages instead the use of antibiotics the following features:
– Obligate lytic phages are bactericidal agents, in opposition with some antibiotics that are bacteriostatic agents
– Phages have the ability of auto-dosing, being capable of establish themselves.
– When phages are applied with high purity, they are inherently non-toxic.
– The high specificity of phages contributes to the minimal disruption of normal microflora of the host.
– Phages possess narrower potential of inducing resistance than antibiotics and additionally as they have different receptors than antibiotics they can be used to treat antibiotics-resistant infections.
– Phages are the most abundant organisms on Earth, they are very easy to discover with low cost of production.
– They are very versatile in terms of formulation and application.
– Phages have shown potential to clear some biofilms, showing better results than some antibiotics.
– As phages are composed predominantly of nucleic acids and proteins, with narrow host range, they have low environmental impact.
Through Staphylococcus epidermidis biofilm formation, PIA is a cationic molecule responsible for association with negatively charged surfaces.
In this study the authors wanted to use a targeted cationic peptide with the goal to disrupt electrostatic interaction between S. epidermidis cells and PIA, so the biofilm formation can be reduced.
The authors used a fibrinogen-based β6-20 peptide (binds specifically to S. epidermidis surface) and fused this sequence with a cationic sequence. Three peptides were synthetized β6-20-G3K6 and two individual components of this peptide β6-20 and G3K6 that were used for controls. They saw that both of the peptides did not affect biofilm growth and concentration range of β6-20-G3K6 (0-100 μM) had minimal effects.
Lytic activity of the virio-associated peptidoglycan hydrolase HydH5 of Staphylococcus aureus bacteriophage vB_SauS-phiIPLA88
In this article, the authors described the structural endolysin of the previously characterized S. aureus bacteriophage vB_SauS-phiIPLA88 (phiIPLA88), belonging to Siphoviridae family.
The structural component with lytic activity corresponded to a protein with 72.5 kDa (orf58) placed in the morphogenetic module. This enzyme is constituted by two catalytic domains, a CHAP (N-terminal) and a LYZ2 (C-terminal). The middle region did not shown any conserved sequences and consequently no CDB was detected.
A phylogenetic study was performed with the 25 staphylococcal peptidoglycan (PG) hydrolases. The authors highlight that PG hydrolases from phages infecting S. epidermidis are similar to those infecting S. aureus. Furthermore, predicted 3D structure was obtained, using HHpred server and MODELLER software.