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ESBL-Producing Bacteria Found in 61% of Sampled Urban Hooded Crows in Hungary

Hooded crow on a street in Budapest
Research · Disease, parasites & microbiology

ESBL-producing Enterobacterales were detected far more often in urban than rural hooded crows (Corvus corone cornix) in Hungary. The study, published online on 10 August 2026, found these antibiotic-resistant bacteria in 130 of 212 urban birds, or 61%, compared with four of 52 rural birds, or 7.7%.

The researchers collected faecal samples from wild crows caught with ladder traps and identified the bacteria in the laboratory. They also tested antibiotic susceptibility and looked for genes that encode extended-spectrum beta-lactamases (ESBLs). These enzymes can break down several commonly used beta-lactam antibiotics and make the bacteria resistant to them.

E. coli dominated, but belonged to many lineages

Escherichia coli was overwhelmingly the dominant ESBL-producing bacterium. The blaCTX-M-1 group was the most common group of ESBL genes in both urban and rural samples. The researchers also detected resistance genes affecting other antibiotic classes and plasmids, mobile DNA elements that can carry resistance genes between bacteria.

Whole-genome sequencing was completed for 197 of the isolated ESBL-producing E. coli. The bacteria belonged to 22 sequence types, a genetic classification used to distinguish bacterial lineages, with ST58 the most common. This showed that the resistant E. coli found in the crows were genetically diverse rather than belonging to a single sequence type.

The authors interpret the strong urban–rural difference as evidence that anthropogenic sources in cities play an important role in exposure to ESBL-producing bacteria. Because hooded crows increasingly use cities and move through human-dominated environments, the authors suggest that the birds may help disseminate resistant bacteria between the environment and people; the study did not directly trace transmission between crows and humans.

Sources and image credit

  1. Carriage of ESBL-Producing Enterobacterales in Urban and Rural Hooded Crows in HungaryOpen-access peer-reviewed primary study comparing faecal carriage of ESBL-producing Enterobacterales in 212 urban and 52 rural hooded crows in Hungary, with whole-genome sequencing of ESBL-producing E. coli.
  2. PubMed — Carriage of ESBL-Producing Enterobacterales in Urban and Rural Hooded Crows in HungaryBibliographic record and abstract confirming sample sizes, prevalence contrast and genomic results.

Image: Jakub Hałun / Wikimedia Commons — hooded crow (Corvus corone cornix) on a street in Budapest, Hungary; representative image from the same country as the study, not one of the sampled birds · CC BY-SA 4.0 · Source

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