Biocontrol of methicillin-resistant Staphylococcus aureus using a virulent bacteriophage derived from a temperate one

Prophage transduction promotes the transmission of phage resistance interfering with adsorption among Chinese foodborne Staphylococcus aureus

Although bacteriophages have proven to be efficient biocontrol agents for foodborne Staphylococcus aureus, the transmission of phage resistance resulting in the reduced efficacy of phage therapy remains to be explored. In this study, phage resistance and adsorption of 91 Chinese foodborne S. aureus isolates by 18 phages were estimated, and the distribution and transmission of phage resistance genes were investigated. The isolated 91 S. aureus comprised 50 multidrug-resistance isolates, all of which showed sensitivity to more than two phages. However, 9.9 % (9/91) of S. aureus isolates were resistant to all 18 phages, and the majority of phages (83.3 %, 15/18) did not adsorb to all foodborne S. aureus strains. Whole-genome analysis revealed that the 91 isolates comprised 101 phage resistance genes, including 24 genes were found in prophages (intact prophages, 19.8 %, 20/101; incomplete prophages, 16.8 %, 17/101). Notably, a temperate phage SapYZUs631 was successfully induced and exhibited better biological characteristics compared to other isolated S. aureus temperate phages, including higher titre (6.2 × 109 PFU/mL), stronger pH (4-11) and thermal (60 °C for 60 min) stability, and a wider host range (80.2 %, 73/91). The SapYZUs631 genome contained phage resistance gene tarP interfering with adsorption and virulence genes. The lysogeny of SapYZUs631 into S. aureus strains YZUstau27, YZUstau31, and YZUstau35 resulted in increased phage resistance and decreased adsorption. Therefore, our analysis suggests that the interruption of adsorption is the main reason for the phage resistance of foodborne S. aureus in China, which resulted from the transmission of phage resistance by prophage transduction.

Characterization, genomic analysis and preclinical evaluation of the lytic Staphylococcus bacteriophage PSK against methicillin-resistant Staphylococcus aureus wound isolate

BACKGROUND

The dissemination of multi-drug-resistant bacteria, particularly Methicillin-resistant Staphylococcus aureus (MRSA), necessitates exploring new alternatives for their control. Bacteriophages are promising antibiotic alternatives with unique features. Here, we have performed a comprehensive characterization of a newly isolated bacteriophage (PSK) and compared its therapeutic potential with vancomycin in vivo.

METHODS

Sewage samples were processed and enriched with the MRSA S. aureus SK1 strain in a search for isolation of a lytic bacteriophage. The isolated bacteriophage was assessed in vitro in terms of thermal and pH stability and kinetic parameters using absorption and one step growth curve assays. Moreover, its potential antibacterial activity was evaluated against S. aureus SK1 lone and in combination of standard of care antibiotics used for treatment of wound infections. We further analyzed its genome to exclude the presence of any potential toxin or antibiotic resistance genes. Finally, its antibacterial potential and capability to alleviate wound infection were assessed using a murine wound-infection model.

RESULTS

The lytic bacteriophage (PSK) was isolated as a new species of the genus Rosenblumvirus with a genome size of 17,571 bp that is free from potential resistance or virulence genes. PSK displays infectivity against 4/10 S. aureus strains including two vancomycin-resistant strains. Moreover, it demonstrates favorable infection kinetics of fast adsorption with latent period and burst size of 20 min and 123 PFU/infected cell, respectively. Stability analysis revealed thermal stability up to 60 °C with wide pH range stability (4-11). In vitro, PSK kills S. aureus SK1 with multiplicity of infection (MOI) as low as 10- 4 with an overall mutation frequency of 2.47 × 10- 6 CFU/mL that is further improved when combined with 0.25× MIC of oxacillin, fusidic acid or vancomycin. In vivo, a single dose of PSK in murine wound infection model exhibited a comparable performance to four doses of vancomycin, when treatment started 2 h post-infection. However, when applied 2 days post-infection, PSK demonstrates superior antibacterial activity (up to 4.58 log unit count reduction) and enhances wound closure and tissue healing.

CONCLUSION

These findings represent PSK as a potential vancomycin alternative effective in treating S. aureus- induced wound infections.

Isolation, characterization and application of noble bacteriophages targeting potato common scab pathogen Streptomyces stelliscabiei

Bacteriophages have emerged as promising alternatives to pesticides for controlling bacterial pathogens in crops. Among these pathogens, Streptomyces stelliscabiei (syn. S. stelliscabiei) is a primary causative agent of potato common scab (PCS), resulting in substantial global economic losses. The traditional management methods for PCS face numerous challenges, highlighting the need for effective and environmentally friendly control strategies. In this study, we successfully isolated three novel bacteriophages, namely Psst1, Psst2, and Psst4, which exhibited a broad host range encompassing seven S. stelliscabiei strains. Morphological analysis revealed their distinct features, including an icosahedral head and a non-contractile tail. These phages demonstrated stability across a broad range of temperatures (20-50°C), pH (pH 3-11), and UV exposure time (80 min). Genome sequencing revealed double-stranded DNA phage with open reading frames encoding genes for phage structure, DNA packaging and replication, host lysis and other essential functions. These phages lacked genes for antibiotic resistance, virulence, and toxicity. Average nucleotide identity, phylogenetic, and comparative genomic analyses classified the three phages as members of the Rimavirus genus, with Psst1 and Psst2 representing novel species. All three phages efficiently lysed S. stelliscabiei in the liquid medium and alleviated scab symptom development and reduced pathogen abundance on potato slices. Furthermore, phage treatments of radish seedlings alleviated the growth inhibition caused by S. stelliscabiei with no disease symptoms. In soil potted experiments, phages significantly reduced disease incidence by 40%. This decrease is attributed to a reduction in pathogen density and the selection of S. stelliscabiei strains with reduced virulence and slower growth rates in natural environments. Our study is the first to report the isolation of three novel phages that infect S. stelliscabiei as a host bacterium. These phages exhibit a broad host range, and demonstrate stability under a variety of environmental conditions. Additionally, they demonstrate biocontrol efficacy against bacterial infections in potato slices, radish seedlings, and potted experiments, underscoring their significant potential as biocontrol agents for the effective management of PCS.

Evaluating the Stability of Lytic and Lysogenic Bacteriophages in Various Protectants

Phage therapy has regained value as a potential alternative and a complementary anti-infective approach to antibiotics in the fight against bacterial pathogens. Due to their host specificity, non-pathogenic nature for humans, and low production cost, phages offer an effective opportunity for utilization in healthcare, agriculture, and food preservation. Well-defined storage conditions are essential for commercialization and dissemination of phage usage. For this purpose, in our study, after the isolation and characterization of two different phages, one lytic and the other lysogenic; storage and shelf-life studies of phages were evaluated in a presence of various protectants (glycerol, sodium azide, DMSO with chloroform) and without any protectant during 8-month period at four different temperatures. The short-time stability of the lytic P. syringae phage and lysogenic MRSA phage, which were determined by STEM analysis to belong to the Straboviridae and Siphoviridae families, respectively were also examined for the different temperatures and the pH levels ranging from 1.0 to 14.0. This study revealed the storage-model of phages that exhibit distinct lifecycles, for the first time and provided a theoretical basis for development and application of phages, has yielded valuable findings contributing to understanding of phage biology.

Staphylococcus aureus - Review on potential targets for sensors development

Staphylococcus aureus (S. aureus) is accountable for a wide variety of clinical disease with a high rate of morbidity and mortality around the globe. It has a leading place into the ESKAPE group that includes six pathogens and exhibit multidrug resistance and are the major cause of healthcare associated infections: Enterococcus faecium, S. aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp. A critical overview regarding the development of sensors for both S. aureus and his, more dangerous alter ego, Methicillin-resistant S. aureus (MRSA) was presented focusing on the bacteria targets starting with the detection of the whole cell, up to specific wall components, toxins or other virulence factors. The literature data was systematically assessed having in sight the design of the sensing platforms, the analytical performances, and possible courses of action to be implemented in real practice as point-of-care (POC) devices. Moreover, a distinct section was dedicated to commercially available devices and out of the box approaches, namely the use of bacteriophages as an alternative to antimicrobial therapy and as sensors modifiers. The reviewed sensors and devices were discussed in terms of their suitability for different biosensing applications, in early screening of contamination regarding food analysis, environmental monitoring and in clinical diagnosis.