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People themselves are main source of ESBL antibiotic resistance

Researchers from the National Institute for Public Health and the Environment, Utrecht University, University Medical Center Utrecht, the Animal Health Service and Wageningen Bioveterinary Research, all members of the ESBLAT consortium, have previously shown that ESBL antimicrobial resistance is common in humans, livestock and companion animals, food of animal origin and the environment. However, ESBL types in humans were found to differ from those in animals and food. The most important source of contamination for humans remained unknown until now.

New research published in The Lancet Planetary Health shows that humans themselves are the most important source of ESBL antibiotic resistance.

According to a mathematical model, human-to-human transmission is responsible for more than 60% of all humans that are carriers of ESBLs in their intestines. The contribution of food was estimated at around 19%, contact with pets at 8%, non-professional contact with livestock at 4% and swimming in surface water and contact with wild birds at 3%. This means that ESBLs are mainly transferred between people and that people get ESBLs to a lesser extent through animals, animal food and the environment. These results indicate that ESBL transmission and contamination has a true One Health character. The results also show that continuous exposure from different sources such as humans, animals, food and the environment maintains the occurrence of ESBLs in the population. These are the main conclusions of the scientific research recently published in the journal The Lancet Planetary Health.

ESBL-producing bacteria

ESBL stands for Extended Spectrum Beta Lactamase, which is an enzyme produced by certain bacteria that inactivates certain types of antibiotics (in particular penicillins and cephalosporins) and as a consequence makes these bacteria insensitive (= resistant) to these antibiotics. The bacteria that produce ESBLs are often common intestinal bacteria (for example Escherichia coli). About 5% of the Dutch population carries ESBL-producing bacteria. These bacteria are harmless as long as they are in the gut of healthy people. They can sometimes cause infections, such as difficult-to-treat bladder infections. Infections with these bacteria are a problem especially for vulnerable people and patients in the hospital.


The study used data from previous studies on the occurrence of ESBLs and on the different types of ESBLs in different sources. These sources were patients, healthy people in the general population, people with professional contact with animals, travelers, pets, cattle, wild birds, food and surface water. A mathematical model has been used to estimate the extent of these sources’ contribution to human infections. The research was made possible in part by the 1Health4Food public-private research program and the European subsidy program for research and innovation in Europe Horizon-2020 through the One Health European Joint Programme.