Why is enrichment of the sewage sample necessary for the isolation of phage?

Enrichment of sewage samples is necessary for the isolation of phages because it increases the concentration of phages specific to the target bacteria, improving the chances of recovery. Sewage contains a diverse microbial community, and enrichment helps to selectively amplify the phage population that can infect the desired host bacteria. Additionally, this process can enhance the viability of phages by providing optimal growth conditions for both bacteria and phages, leading to a more successful isolation.