Diverse virulent pneumophages infect Streptococcus mitis

Area of Science:

• Microbiology
• Virology
• Genetics

Background:

• Streptococcus mitis is a leading cause of bacterial endocarditis.
• Increasing antibiotic resistance in S. mitis and Streptococcus pneumoniae necessitates alternative treatments.
• Bacteriophages are being re-evaluated as potential antimicrobial agents.

Purpose of the Study:

• To investigate the infectivity of pneumophages Cp-1 and Dp-1 on S. mitis.
• To compare phage replication and genomic stability in S. mitis versus S. pneumoniae.
• To re-evaluate and potentially reclassify phage Cp-1 based on genomic analysis.

Main Methods:

• Microbiological assays to assess phage replication and plaque formation.
• Phage adsorption and burst size experiments.
• Whole-genome sequencing of phages grown on different hosts.

Main Results:

• Virulent phages Cp-1 (Podoviridae) and Dp-1 (Siphoviridae) successfully infected and replicated in S. mitis.
• Phages produced visible plaques on S. mitis, though with lower burst size and adsorption rates compared to S. pneumoniae.
• Genomic sequencing confirmed identical nucleotide sequences, indicating the same phages infect both species.
• The genome of Cp-1 differed from previous reports, leading to its renaming as SOCP.

Conclusions:

• Pneumophages Cp-1 and Dp-1 demonstrate infectivity against S. mitis, expanding their potential therapeutic applications.
• Phage genomes remain stable when replicating in S. mitis, supporting their use in phage therapy.
• The reclassification of Cp-1 to SOCP refines phage taxonomy and understanding.