🔬 Active Treatment

Discussion

Active phage therapy — also called active phage treatment — is a mode of phage therapy in which therapeutic efficacy depends on phage population growth occurring in situ at the site of treatment. The number of phages initially administered is, by definition, insufficient on its own to destroy the target bacterial population or culture; adequate therapeutic titers are attained only because phages replicate and accumulate during the course of antibacterial treatment.

Active treatment is therefore accessible only to phages that are capable of replication within the target host — that is, phages whose infections are both lytic and productive. Phages that can kill bacteria but cannot themselves replicate are limited to passive treatment strategies. Contrast passive treatment.

For active treatment to succeed, three conditions must be met: (1) target bacteria must be present in sufficient densities to support phage population growth in situ; (2) phage population growth must be sufficiently rapid; and (3) phages must accumulate to densities sufficient to destroy the bacterial population. At the level of individual infections, sufficiently large burst sizes, sufficiently rapid adsorption, and sufficiently short latent periods are all relevant to achieving successful active treatment.

Active treatment can also be used to describe phage penetration into target bacterial populations or into bacterial biofilms when that penetration is itself driven by active phage replication — a process sometimes termed "active penetration."

Gill and Young (2011, p. 401) define active treatment as: "A model of phage therapy characterized by lower initial phage dosages, requiring active replication of the phage at the site of infection to generate enough phage to eradicate the bacterial population. In contrast to inundative therapy."

See also

Phage therapy, Passive treatment, Lytic infection, Productive infection, Burst size, Latent period, Adsorption, Titer

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