Red-naped ibises in Udaipur carry

A new study has found that red-naped ibises in Udaipur, Rajasthan, carry diverse bacteria in their faeces, including strains resistant to multiple antibiotics. The research, conducted by scientists from Mohanlal Sukhadia University, identified 60 bacterial isolates from 45 faecal samples collected between July 2022 and June 2023.

Vijay Kumar Koli, a co-author of the study, explained the bird's suitability for such research. Its year-round presence, broad habitat use, and frequent contact with human-influenced environments make it useful for investigating how bacteria and antibiotic resistance circulate. The ibis is an opportunistic omnivore, consuming insects, amphibians, and even foraging at garbage sites.

Sampling and analysis methods

Researchers collected fresh faecal samples from free-ranging birds without capturing them, observing from over 15 meters away. Namita Ashish Singh, another co-author, described the process. Samples were taken across summer, monsoon, and winter seasons from various habitats in Udaipur city.

The team isolated coliform bacteria and used DNA sequencing for identification. They tested 30 representative isolates for antibiotic susceptibility using the Kirby-Bauer disk diffusion method. Statistical tests compared bacterial findings across the three seasons.

Seasonal variations in bacteria

Coliform counts were highest in winter, followed by summer and monsoon. Escherichia coli was the most common bacterium found. The bacterial composition changed with the seasons.

The study identified four novel bacterial taxa not previously reported in this bird species: Enterobacter mori, Enterobacter soli, Citrobacter freundii, and Leclercia adecarboxylata. Koli noted that detecting E. Mori and E. Soli suggests the birds acquire environmental bacteria while foraging in soil, wetlands, and garbage-influenced areas.

Antibiotic resistance findings

All Enterobacterales isolates were resistant to linezolid and rifampicin. However, all isolates were susceptible to chloramphenicol, ciprofloxacin, cefepime, and ofloxacin. Concerning patterns emerged with other drugs.

Of the 30 isolates tested, 50% were resistant to amoxicillin and 30% showed intermediate resistance to ampicillin. A notable finding was reduced susceptibility to imipenem, a carbapenem antibiotic used for severe multidrug-resistant infections. Sixteen percent of isolates were resistant to imipenem, with another 30% showing intermediate resistance.

40% of the tested isolates were multidrug resistant, showing non-susceptibility to at least three antibiotic classes. Singh called this an important public health finding. Resistance patterns varied between bacterial groups.

Study limitations and context

The researchers caution against overinterpreting the results. Koli stated the study does not establish the ibis as a major source of antibiotic resistance or that it transmits resistant bacteria to humans or livestock. It indicates the species can carry resistant bacteria and may contribute to their environmental dispersal through faeces.

A separate 2026 study by the same group on cattle egrets in Udaipur found about 33% of bacterial isolates were multidrug resistant. The studies do not establish that one species carries more resistant bacteria than another.

Limitations include the study's confinement to Udaipur, its sample size of 45 faecal samples and 60 isolates, and its focus only on culturable Enterobacterales bacteria. Koli said the resistance percentages apply only to the tested isolates, not the entire ibis population, and the study does not provide a complete picture of all bacteria present. The research suggests birds may acquire environmental bacteria while foraging but calls for further genomic and cross-species studies.