Fighting Bacteria — With Viruses

Fighting Bacteria — With Viruses

By Kenneth Skinner



As we near an era in which infectious bacteria are completely resistant to antibiotics, we’ll need to pull out the big guns.

By Kenneth Skinner

Since the discovery of penicillin in 1928, antibiotics have transformed medicine and saved millions of lives. Hailed as the “miracle drug” of the 20th century, antibiotics have become an easy fallback solution, and doctors are often quick to prescribe them, even for minor symptoms. But as often happens with too much of a good thing, overuse of antibiotics can be dangerous — and even deadly.

Although antibiotics target dangerous pathogens, they can also kill beneficial bacteria that help maintain health. It’s a familiar survival-of-the-fittest scenario. Microbes that are more susceptible to antibiotics — good and bad bugs alike — are the first to die off during treatment, allowing more resilient bacteria to take their place. Those microbes can then thrive and spread. Sometimes they even share their drug-resistance genes with other bugs, which can then also multiply, resulting in hard-to-treat superbugs that are resistant to multiple antibiotic drugs.

Staphylococcus aureus MRSA bacteria, computer artwork. Methicillin-resistant Staphylococcus aureus (MRSA, orange) is a Gram-positive, round (coccus) bacterium, shown here on a filamentous surface. It is resistant to many commonly prescribed antibiotics. S

Reinforcements in the bacteria war.

Source Corbis

It’s an expanding problem. According to the CDC, antibiotic-resistant bacteria infect 2 million Americans and kill at least 23,000 each year. Hospitalized and elderly patients are especially vulnerable.

Antibiotic-resistant bacteria infect 2 million Americans and kill at least 23,000 each year.

BW headshot of Felix as an older man

Félix d’Herelle

Source Getty

Instead of feeding the cycle of antibiotic resistance by creating yet more classes of drugs, scientists have turned to an unlikely weapon: viruses. Viruses, specifically phages, infect and kill bacteria but not human cells. Phages are much more targeted than antibiotics; each type of phage can attack only one specific bacterial strain. So why is it better to have a targeted attack instead of the “wide spectrum,” scattershot approach we know we get from antibiotics? In the focused attack, only the target microbes perish, while the body’s beneficial bacteria remain unaffected. This reduces the likelihood that harmful strains of bacteria will take over, spread and increase the risk to public health.

And even if the bacteria do become resistant to phage therapy, the virus — unlike an antibiotic — will adapt accordingly. Worst-case scenario, designing a phage therapy for a resistant bacterial strain would take only a matter of weeks, compared with months for an antibiotic to do the same work.

But by the time Herelle died in 1949, phages had fallen out of fashion. Their “narrow spectrum” behavior required scientists to understand the target bacterial strain in detail and know exactly what mixture of phages to use against it — a near-impossible task with the technology available at the time. Meanwhile, antibiotics were much simpler and had yielded a number of “miracle” cures. As a result, they largely displaced phages in Western medicine. Canadian physician Félix d’Herelle discovered phages in 1917. A few years later, phages surged in popularity. Herelle even developed a commercial phage medication sold by the company now known as L’Oréal to treat skin wounds and intestinal infections.

Since phages are live viruses, they can adapt even if the bacteria do develop resistance.

Farther East, the Soviet scientists Herelle had met during his travels continued to investigate phage therapy. In 1963, they tested phages in 30,000 children with dysentery in Tbilisi, which is now the capital of Georgia. Taking phages caused a nearly fourfold decrease in their chance of getting the disease. And today, phages are available over the counter in Russia and Georgia. Such products are often used to treat burn wounds, as well as staph and strep infections. 

After the fall of the Soviet Union, phage therapy began to attract the interest of some scientists in the West, when Soviet scientists could communicate freely with their peers abroad. But by then, the U.S. had become wary of approving viruses for treating diseases.

Labs have begun to tackle the hurdles that held back phage research over the past 60 years.

Phages are making a comeback, though, thanks to their crucial role in preventing us from developing resistance to the antibiotics that prevent infections in livestock. EcoShield, for example, is a phage cocktail added to meat that attacks a strain of E. coli that’s responsible for 62,000 cases of food poisoning a year. 

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Enterobacteria phage T4, a phage that infects E. coli bacteria

Western scientists gave phage therapy another shot in 2009, when University College London and Biocontrol Ltd. researchers enrolled 24 patients with chronic, antibiotic-resistant ear infections. With just a single phage dose, the levels of resistant bacteria in their ears dropped significantly, and their symptoms improved dramatically. In contrast, the most stubborn infections often require daily doses of antibiotics taken over several weeks. 

Meanwhile, academic, commercial and government labs have begun to tackle the hurdles that held back phage research over the past 60 years. Researchers now use sophisticated molecular techniques to design methods for classifying bacterial populations and identifying the right mixture of phages to use, for example.

And it may be about time. In a media briefing of the CDC’s antimicrobial resistance threat report last September, agency director Tom Frieden predicted that we might soon enter a “postantibiotic era” — one in which superbugs have rendered antibiotics useless. In our evolutionary battle against the bugs, phages might be just the reinforcement we need.