Comparative study on the virulence of mycobacteriophages

Area of Science:

• Microbiology
• Virology
• Biotechnology

Background:

• Tuberculosis (TB) remains a major global health challenge, with multidrug-resistant strains complicating treatment.
• Mycobacteriophages, viruses infecting TB-causing bacteria, offer a potential alternative therapeutic strategy.
• Assessing phage performance, including virulence and adsorption, is crucial for developing effective phage-based treatments.

Purpose of the Study:

• To characterize the virulence of three mycobacteriophages (Fionnbharth, Muddy, D29) and their cocktails.
• To evaluate phage efficacy against *Mycobacterium smegmatis* in both planktonic and early-stage biofilm conditions.
• To understand the impact of host growth conditions on mycobacteriophage infection dynamics.

Main Methods:

• Virulence assays were conducted on planktonic and early-stage biofilm cultures of *Mycobacterium smegmatis*.
• Three individual mycobacteriophages (Fionnbharth, Muddy, D29) and their combinations (cocktails) were tested.
• Adsorption efficiency of phages on planktonic and biofilm phenotypes was quantified.

Main Results:

• Phage D29 and cocktails containing D29 demonstrated the highest virulence across all tested conditions.
• Phages Fionnbharth and Muddy, individually and in combination, exhibited greater virulence against early-stage biofilms than planktonic bacteria.
• All tested phages showed reduced adsorption efficiency on early-stage biofilms compared to planktonic cells, suggesting alternative infection advantages.

Conclusions:

• Mycobacteriophage virulence is influenced by host growth state, with some phages performing better against biofilms.
• Despite lower adsorption rates on biofilms, phages can maintain or increase virulence, indicating biofilm-specific infection facilitators.
• These findings provide foundational data for developing mycobacteriophage-based therapies targeting diverse TB bacterial states, including biofilms.