London School of Hygiene & Tropical Medicine

While many people will have heard of bacteria such as E. coli and salmonella, Klebsiella pneumoniae (also referred to as Klebsiella or K. pneumoniae) is not such a household name even though it leads to 250,000 global deaths each year.

The latest evidence suggests Klebsiella, which can cause illnesses including pneumonia, sepsis, and urinary tract infections, is becoming increasingly resistant to antibiotics, highlighting the global antimicrobial resistance crisis.

Professor José Bengoechea, Dean of the Faculty of Infectious and Tropical Diseases at the London School of Hygiene & Tropical Medicine, has spent more than two decades studying how bacteria interact with our defences and how this drives infection and resistance. His team has pioneered therapeutic approaches that protect parts of our immune system targeted by Klebsiella.

As we mark World Antimicrobial Awareness Week 2025 (18–24 November), we asked Professor Bengoechea about Klebsiella and why it has become a global concern.

What is Klebsiella and where is it found?

Klebsiella belongs to the Enterobacteriaceae family, which includes Salmonella, Shigella and E. coli. It commonly lives in the gut of healthy people without causing illness; more than 2 billion people are estimated to carry it. It is also found in soil, hospital environments such as sinks and beds, and in animals including cows, pigs, cats and dogs. Its ability to feed off a wide range of nutrients allows it to survive in many settings.

What illnesses does Klebsiella cause?

Klebsiella is one of the leading microbes associated with antibiotic-resistant infections. It can cause pneumonia, bloodstream infections, sepsis, neonatal sepsis and urinary tract infections and, less frequently, wound or eye infections. More than 250,000 people die each year from these infections, with mortality reaching up to 80% when treatment fails. Strains resistant to antibiotics including carbapenems and third-generation cephalosporins leave clinicians with very limited treatment options, which is why the World Health Organization lists Klebsiella as a priority pathogen.

Why is it such a concern for antimicrobial resistance?

Klebsiella rapidly acquires and spreads genes that make antibiotics ineffective. It is surrounded by a thick sugary capsule which acts like a slippery shield, helping it hide from the immune system and making it harder for antibiotics to reach it. Beneath this sits a tough outer membrane that provides further protection.

It commonly produces enzymes including KPC, NDM and OXA-48, which destroy carbapenems, a critical group of last-resort antibiotics. These highly resistant strains often circulate in hospitals, where vulnerable patients and intensive antibiotic use favour outbreaks. Particularly concerning are strains that combine extensive drug resistance with an enhanced ability to evade immune defences.

How do you get Klebsiella, and who is most at risk?

Klebsiella spreads mainly through contact in healthcare settings. It survives on hands, gloves, bed rails and medical equipment, and is transferred when these are not properly cleaned. It does not spread through the air. Many people carry Klebsiella in their gut without symptoms, and from there it can reach other parts of the body.

Hospitalised patients, especially those in intensive care and those with medical devices such as urinary catheters, central lines, ventilators or feeding tubes, are at highest risk. Older adults, immunocompromised individuals and premature infants are also particularly vulnerable. In recent years, increasing numbers of community-acquired Klebsiella infections have been reported, affecting people both with and without underlying conditions.

What’s happening globally right now?

Global data from the latest WHO Global Antimicrobial Resistance and Use Surveillance System (GLASS) show a sharp rise in resistance. More than 55% of Klebsiella isolates worldwide are resistant to third-generation cephalosporins, and in some regions the figure exceeds 70%. In several countries, resistance to last-resort antibiotics has left few or no effective treatments, with especially severe consequences in low- and middle-income settings.

How is Klebsiella infection treated?

With few new antibiotics being developed, alternative strategies are urgently needed. Host-directed therapies, which strengthen the patient’s immune response rather than targeting the bacteria directly, are a promising approach. The London School of Hygiene & Tropical Medicine is leading in this area. Researchers are also developing new drug combinations to bypass resistance mechanisms, as well as monoclonal antibodies that block factors Klebsiella uses to cause infection.

What can be done to control it?

Infection prevention remains essential. Effective cleaning, hand hygiene and proper management of medical devices help limit transmission, while antibiotic stewardship programmes ensure antibiotics are used appropriately to slow the development of resistance.

Klebsiella infections are a serious and growing public health threat. Once mainly confined to hospitals, Klebsiella is now an important cause of community-acquired infections, including in healthy individuals. Its capacity to develop resistance to multiple antibiotics makes some infections extremely difficult to treat.

This rise threatens modern medicine by making routine treatments and procedures riskier. Vulnerable groups - including older adults, infants, people with chronic illnesses and those undergoing medical care - are most affected, but no one is completely protected. Continued investment in research, responsible antibiotic use and strong infection-control practices are critical to prevent antibiotic-resistant Klebsiella from escalating into an even greater global crisis.