---
title: "Fifteen years of sewage, one refrigerator, and a library of bacteria-killing viruses"
description: "University of Colorado researchers stockpile bacteriophages against gut bacteria that have learned to shrug off antibiotics"
author: "Tomasz Idle"
published: 2026-09-26T08:43:32.170Z
modified: 2026-09-26T19:00:58Z
url: https://rews.cc/a/fifteen-years-of-sewage-one-refrigerator-and-a-library-of-ba-ba258c
language: en
tags: ["phages", "antibiotics", "bacteria", "health", "research", "science"]
publisher: "Rews (https://rews.cc)"
---

# Fifteen years of sewage, one refrigerator, and a library of bacteria-killing viruses

*University of Colorado researchers stockpile bacteriophages against gut bacteria that have learned to shrug off antibiotics*

By Tomasz Idle · September 26, 2026 · https://rews.cc/a/fifteen-years-of-sewage-one-refrigerator-and-a-library-of-ba-ba258c

## In brief

- An estimated 38 trillion bacteria live in the human body; rising antibiotic resistance is driving renewed interest in bacteriophages
- A University of Colorado Anschutz team has spent 15 years building a phage library targeting drug-resistant gut bacteria
- Phages are harvested from untreated wastewater, purified by centrifuge and stored refrigerated with long shelf lives
- The library holds 30-plus phages against enterococcal bacteria and roughly 15 to 20 against Enterobacter and Klebsiella
- Phages can be given orally, by IV or topically on burns, but bacteria can also evolve resistance to them

Somewhere in a refrigerator at the University of Colorado Anschutz School of Medicine there sits a library whose entire collection was recruited from untreated sewage. The books are viruses. Each one is a specialist killer of exactly one kind of bacterium, and they keep beautifully on the shelf.

Of the estimated 38 trillion bacteria living in the human body, only a small fraction do us harm — but the harmful ones are increasingly learning to survive antibiotics. That is why researchers are turning to bacteriophages, or phages: viruses found in nature that infect bacteria and nothing else. “Phages have been used historically for decades as tools to understand molecular biology, but there’s been a resurgence in interest in them due to the rising incidence of antibiotic-resistant bacterial infections,” says Breck Duerkop, associate professor of immunology and microbiology. “We can isolate viruses against infections that are difficult to treat, and some of the viruses will kill the bacteria very readily.”

Duerkop’s group has spent 15 years building its collection, and it has strong opinions about which bacteria deserve the library’s attention. The primary targets are Enterococcus faecalis and Enterococcus faecium, two highly drug-resistant species that live peacefully in healthy human guts but can cause severe infections in people with compromised immunity. Rounding out the collection are emerging pathogens like Enterobacter hormaechei and Klebsiella oxytoca.

A phage’s method is charming in its brutality: it pokes holes through the bacterial cell wall and injects its genetic material directly inside, hijacking the cell to make copies of itself — roughly the same vandalism that human viruses commit against us, aimed at the bacteria instead. Crucially, phages cannot infect human cells. The assassin does not mistake you for the mark.

Recruitment happens at the sewage works. Untreated wastewater teems with the bacteria of the gut microbiome and the viruses that prey on them, so the team exposes its target bacteria to the water, grows the bacteria on agar plates known as bacterial lawns, and waits. Where a phage has gone to work, a round clearing called a plaque forms in the lawn; the researchers extract phages directly from the plaques, purify the samples in a centrifuge, and store them in buffers in the refrigerator, where they stay stable with long shelf lives.

The current holdings: more than 30 different viruses that infect enterococcal bacteria, and roughly 15 to 20 aimed at Enterobacter and Klebsiella. “The idea of generating a library is you want some diversity,” says Duerkop. “Not every phage infects every type of bacteria. They’re very specific.” Some phages attack broadly across a species; some will touch only a single strain, which makes them less a weapon than a sniper.

In practice, phages can be combined with FDA-approved antibiotics and given orally or by IV — especially for blood infections like septicemia — and have even been applied topically to infected burns and other skin injuries. They are not a cure-all: bacteria can evolve resistance to phages, too, in the timeless spirit of the arms race. But when antibiotics fail on their own, the library offers a fallback. “It’s imperative that we explore creative ways to use phages in combination with antibiotics to target antibiotic-resistant bacteria,” Duerkop says.

> We are just beginning to scratch the surface on the diversity of phages that have therapeutic potential. By continuing to study the biology of these phages, we stand to learn more about our natural world and the role of phages in it.

For most of a century, medicine fought bacteria with chemistry, and the bacteria studied harder each year. The sewer, it turns out, had already hired the assassins. All that remained was to keep them cold.