Illustration of antibiotic resistance spreading in Spain

Superbugs in Spain: Are Everyday Foods Fueling Antibiotic Resistance?

Reese Marlowe in Health & Wellness July 2025 • 4 min read.

"New research reveals how common mobile genetic elements in ESBL-producing E. coli are spreading through food and the environment, threatening human health."

Antibiotic resistance is a growing global crisis, threatening to undo decades of medical progress. The rise of resistant bacteria in the Enterobacteriaceae family, especially those producing extended-spectrum β-lactamases (ESBLs), is alarming. These enzymes make bacteria resistant to many common antibiotics, leaving fewer treatment options for infections.

The spread of antibiotic resistance is fueled by mobile genetic elements (MGEs), such as plasmids, transposons, and integrons. These elements allow bacteria to easily share resistance genes, accelerating the evolution of "superbugs." Understanding how these MGEs are spreading is crucial to combating antibiotic resistance.

A recent study focused on the prevalence of integrons and insertion sequences in ESBL-producing E. coli isolates from various sources in Navarra, Spain. The study aimed to determine how these genetic elements are contributing to the spread of antibiotic resistance in different environments.

Decoding the Superbug Spread: Integrons and Insertion Sequences

Illustration of antibiotic resistance spreading in Spain

The research team analyzed 150 ESBL-producing E. coli isolates from diverse sources, including food products, farms, aquatic environments, and humans. They used PCR to detect class 1, 2, and 3 integrons (intI1, intI2, and intI3) and insertion sequences (IS26, ISEcp1, ISCR1, and IS903).

The results revealed a high prevalence of class 1 integrons (intI1), found in 92% of the isolates. Class 1 integrons are known for their role in antibiotic resistance. Interestingly, class 2 integrons (intI2) were more common in food isolates, suggesting a potential link between food and the spread of resistance. The co-existence of class 1 and class 2 integrons was also observed in 8% of the isolates, raising concerns about the accumulation of resistance genes.

Key Findings on Integrons:

Class 1 integrons (intI1) were widespread (92% of isolates).
Class 2 integrons (intI2) were prevalent in food isolates.
Class 3 integrons (intI3) were not detected.
Co-existence of class 1 and class 2 integrons was observed (8% of isolates).

The majority of isolates had two or three insertion sequence elements, with IS26 being the most common (99.4%). The genetic pattern IS26–ISEcp1, linked to the ST131 pathogen clone, was found in 22% of isolates, including those from humans. Furthermore, a novel combination of ISEcp1–IS26–IS903–ISCR1 was identified in 11 isolates, highlighting the complex genetic arrangements that can arise.

What Does This Mean for You?

This study underscores the increasing threat of antibiotic resistance and the role of mobile genetic elements in its spread. The presence of these elements in food and the environment highlights the potential for exposure to resistant bacteria in everyday life.

While the study didn't find a direct link between specific genetic elements and β-lactam resistance, the variability observed suggests that multiple types of integrons and insertion sequences are involved in the dissemination of antimicrobial resistance genes.

Further research is needed to fully understand the role of these genetic elements and how they contribute to the spread of resistance. In the meantime, practicing good hygiene, avoiding unnecessary antibiotic use, and supporting policies that promote responsible antibiotic stewardship are essential steps in combating antibiotic resistance.

About this Article -

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This article is based on research published under:

DOI-LINK: 10.3390/ijerph15102308, Alternate LINK

Title: Prevalence Of Integrons And Insertion Sequences In Esbl-Producing E. Coli Isolated From Different Sources In Navarra, Spain

Subject: Health, Toxicology and Mutagenesis

Journal: International Journal of Environmental Research and Public Health

Publisher: MDPI AG

Authors: Lara Pérez-Etayo, Melibea Berzosa, David González, Ana Vitas

Published: 2018-10-20

Everything You Need To Know

What did the study discover about the prevalence of different classes of integrons in ESBL-producing E. coli?

The study showed a high prevalence of class 1 integrons (intI1) in 92% of the E. coli isolates examined. Class 2 integrons (intI2) were found more commonly in food isolates, suggesting a connection between food and the spread of antibiotic resistance. Class 3 integrons (intI3) were not detected in this study. Additionally, the co-existence of class 1 and class 2 integrons was observed in 8% of the isolates, raising concerns about the accumulation of resistance genes.

How do mobile genetic elements contribute to the spread of antibiotic resistance, and what specific elements were examined in the study?

Mobile genetic elements (MGEs) like plasmids, transposons, and integrons enable bacteria to easily share resistance genes, speeding up the evolution and spread of "superbugs." In this study, specific MGEs like class 1, 2, and 3 integrons (intI1, intI2, and intI3) and insertion sequences (IS26, ISEcp1, ISCR1, and IS903) were examined to understand their role in spreading antibiotic resistance among E. coli strains.

What exactly are ESBL-producing E. coli, and why are they a concern?

ESBL-producing E. coli refers to strains of Escherichia coli bacteria that produce extended-spectrum β-lactamases (ESBLs). These enzymes confer resistance to many common antibiotics, including penicillins and cephalosporins, making infections caused by these bacteria more difficult to treat. This study focused on understanding how mobile genetic elements contribute to the spread of these resistant bacteria.

What role do insertion sequences play in the spread of antibiotic resistance, and which ones were identified in the study?

Insertion sequences, such as IS26, ISEcp1, ISCR1, and IS903, are DNA sequences that can insert themselves into different locations within a bacterium's genome. These sequences often carry antibiotic resistance genes or promote the movement of such genes, contributing to the spread of resistance. The study revealed that IS26 was the most common insertion sequence and certain combinations of insertion sequences were associated with specific pathogen clones.

What are the potential implications of finding class 2 integrons more commonly in food isolates?

The finding that class 2 integrons are more common in food isolates suggests that food products could be a significant pathway for the transmission of antibiotic-resistant bacteria to humans. This highlights the importance of food safety measures and monitoring to prevent the spread of resistance through the food chain. Additionally, the presence of specific genetic patterns like IS26–ISEcp1, linked to the ST131 pathogen clone, in isolates from humans underscores the potential for direct transmission of resistance from food sources to human populations, raising public health concerns.