In the medical world, the name Klebsiella pneumoniae is increasingly associated not with typical bacterial infections, but with a serious threat that is difficult to treat. This gram-negative bacterium has become a symbol of a new challenge for modern medicine: antibiotic resistance. When antimicrobials no longer provide protection, bacteriophages—natural viruses that "hunt" bacteria—take the lead.

In this article, we'll look at what Klebsiella pneumoniae is , how it infects humans, why it's so dangerous, how phage therapy can help, and what science says about it.

What is Klebsiella pneumoniae: A Stealthy Threat

Klebsiella pneumoniae is an opportunistic bacterium that can normally live in the human intestine without causing any symptoms. However, in weakened individuals or in hospital settings, it quickly becomes an aggressive pathogen.

This microorganism belongs to the Enterobacteriaceae family . It has a protective capsule, making it particularly resistant to the body's immune response. Klebsiella readily colonizes mucous membranes, skin, respiratory tract, and genitourinary system. It is precisely because of this ability to quickly adapt that the bacterium is often implicated in hospital-acquired infections.

Who is most often affected by Klebsiella?

Klebsiella pneumoniae infections most often occur in hospitals. Transmission routes include contact (hands of medical staff), airborne droplets, catheters, endoscopic equipment, ventilation tubes, and direct contact with surfaces where the organism lives.

The risk of infection is lower in everyday life, but it increases in conditions of poor hygiene or close contact with infected people.

At risk:

• newborns;

• patients with weakened immune systems;

• patients with diabetes;
  postoperative patients;

• elderly people.

Diseases caused by Klebsiella pneumoniae

• Pneumonia is the most common form. It presents with fever, shortness of breath, and a cough with sputum that is sometimes foul-smelling or blood-tinged. X-rays show infiltrates or abscesses.

• Urinary tract infections - painful urination, fever, cloudy urine.

• Sepsis is a serious condition that can occur after surgery or prolonged catheterization.

• Meningitis - mainly in newborns, causes convulsions, loss of consciousness, fever.

• Wound infections and postoperative complications.

Klebsiella and antibiotic resistance

The main problem in treatment is resistance. Klebsiella pneumoniae can produce:

• Extended-spectrum beta-lactamases (ESBL) destroy cephalosporins.

• Carbapenemases are enzymes that neutralize even “reserve” antibiotics such as carbapenems.

• Biofilms are a protective coating that makes bacteria inaccessible to drugs.

As a result, doctors often lack effective treatment options. Treatment of such infections is delayed, mortality increases, and hospitalization costs rise. Combination treatment regimens—expensive, toxic, and time-consuming—are increasingly required.

Bacteriophages offer a chance to defeat resistant bacteria

When conventional treatment fails and antibiotics prove ineffective, hope remains in bacteriophages—viruses that destroy bacteria with sniper-like precision. They recognize a specific type of bacteria, inject their genetic material into it, replicate within the cell, and destroy it from the inside.

In the case of Klebsiella pneumoniae, phage therapy can be used in several forms depending on the location of the infection:

• Inhalation – if the infection affects the lungs. Phages are administered as an aerosol through a nebulizer or inhaler, ensuring direct contact with the pathogen in the respiratory tract.

• Orally - in case of intestinal damage or as an adjuvant in septic conditions.

• Intravenously - in severe cases (for example, sepsis or generalized infections).

• Locally - for wound infections, bedsores or postoperative complications.

• Instillation - for urinary tract infections (introduction of the drug into the bladder or urethra).

Another important advantage is the ability to combine phages with antibiotics. This is particularly relevant for the treatment of diseases caused by Klebsiella pneumoniae, as some studies show a synergistic effect of such combinations: phages disrupt the bacteria's defenses, while the antibiotic ultimately destroys them.

In clinical practice, bacterial culture is first performed to identify the specific strain. The laboratory then selects the appropriate phage preparation—either from an existing bank or a custom cocktail. In cases of chronic or complex infections, therapy may last several weeks, and its effectiveness is monitored through testing.

Phages have already proven effective in treating pneumonia, sepsis, urinary tract infections, and postoperative lesions caused by Klebsiella pneumoniae. They not only reduce the bacterial load but also reduce inflammation, promote tissue regeneration, and shorten the length of hospital stay.

Phage therapy studies against Klebsiella pneumoniae

• 2023: Scientists conducted a study using phages against a multidrug-resistant strain of Klebsiella pneumoniae in mice. After treatment, liver inflammation was significantly reduced ( nature.com ).

• Another study found that phage cocktails completely killed multidrug-resistant Klebsiella pneumoniae strains in vitro, even those that did not respond to any existing antibiotics ( journals.asm.org ).

• 2021: A combination of phages with the antibiotic ceftazidime-avibactam effectively killed the superbug KPC (Klebsiella pneumoniae carbapenemase) enzymes , reducing the bacteria levels in the lungs by more than 99% ( nature.com ).

• The American company BiomX conducted a phase 1a study showing that oral administration of the phage preparation safely and effectively delivers phages to the lower intestine ( bacteriophages.info ).

• Indian scientists have demonstrated the effectiveness of intranasal phage administration in mice with Klebsiella pneumoniae pneumonia . The phage reduced the bacterial load and accelerated recovery ( bacteriophages.info ).

• In Belgium, phage therapy was successfully used to treat an infection caused by multidrug-resistant Klebsiella pneumoniae that was resistant to antibiotics. The patient recovered after combined treatment with phages and antibiotics ( bacteriophages.info ).

Who will win - bacteria or phage?

Klebsiella pneumoniae is a challenge for the entire world. Its ability to survive, adapt, and hide from drugs makes it particularly dangerous. But we have a weapon that nature developed long before the advent of synthetic drugs: bacteriophages.

These bacteria hunters are opening up new avenues for treating infections that were considered fatal just yesterday. With the support of science, updated medical protocols, and the active use of phage therapy, we can change the course of this fight.