Bird droppings carry risk of antibiotic resistance
Engineers show feces from gulls, ducks and crows harbor abundant
resistant bacteria, resistance genes

Date:
July 13, 2020
Source:
Rice University
Summary:
Engineers analyze the droppings of urban birds and show persistent
levels of antibiotic-resistant genes and bacteria that may be
transferred to humans through the environment.



FULL STORY ==========================================================================
Bird droppings may pose more health risks than people realize, according
to Rice University environmental engineers who study antibiotic
resistance.


========================================================================== Their study found high levels of genes that encode antibiotic resistance harbored by opportunistic pathogens in the droppings of common urban
ducks, crows and gulls.

The study led by postdoctoral research associate Pingfeng Yu of Rice's
Brown School of Engineering appears in the Elsevier journal Environmental Pollution.

Yu is a member of the lab of civil and environmental engineer and
co-author Pedro Alvarez.

Previous studies determined bird-carried antibiotic resistant genes
(ARGs) and bacteria (ARBs) can be transferred to humans through swimming, contact with feces or impacted soil or inhalation of aerosolized fecal particles. Studies have also analyzed bird feces found near ARG hotspots
like wastewater treatment plants and drainage from poultry farms.

But the Rice study digs deeper to quantify the abundance, diversity and seasonal persistence of ARGs.

"We still do not fully understand what factors exert selective pressure
for the occurrence of ARGs in the gastrointestinal system of wild urban
birds," Alvarez said. "Residual antibiotics that are incidentally
assimilated during foraging is likely one of these factors, but
further research is needed to discern the importance of other potential etiological factors, such as bird diet, age, gut microbiome structure
and other stressors." The team that included lead authors Huiru Zhao,
a student at Nankai University in China, and Rice graduate student Ruonan
Sun compared "freshly deposited" samples from each species found around
Houston during the winter and summer months to samples from poultry and livestock known to carry some of the same mutations.



==========================================================================
They found that ARGs in all of the species, regardless of season, encoded significant resistance to tetracycline, beta-lactam and sulfonamide antibiotics. The researchers were surprised to see the relatively high abundance of ARGs were comparable to those found in the fresh feces of
poultry occasionally fed with antibiotics.

They also found intI1, an integron that facilitates rapid bacterial
acquisition of antibiotic resistance, was five times more abundant in
the birds than in farm animals.

"Our results indicate that urban wild birds are an overlooked but
potentially important reservoir of antimicrobial resistance genes,
although their significance as vectors for direct transmission of
resistant infections is possible but improbable due to low frequency of
human contact," Alvarez said.

The team also looked for ARGs in soil up to 1 inch deep around bird
deposits and discovered they are "moderately persistent" in the
environment, with half- lives of up to 11.1 days.

Of the three species, crows showed a significantly lower level of ARGs
during the summer compared to ducks and gulls, they reported.



========================================================================== "That's probably due to differences in their ecological niches, foraging patterns and gut microbiome," Sun said. "Crows are omnivores and feed
on abundant natural food with less anthropogenic contaminations in the
summer. In addition, the composition of their gut microbiome impacts ARG dissemination and enrichment in vivo, and therefore influences ARG levels
in the excreted bird feces." The researchers found that opportunistic pathogens including bacteria that cause urinary tract infections,
sepsis and respiratory infections were common in the feces of all of
the birds, and another associated with food poisoning was detected in
samples collected during the winter.

Winter feces, they wrote, contained more of the bad bacteria that may also harbor ARGs, possibly due to lower sunlight inactivation and differences
in moisture levels and temperature.

"Our study raises awareness to avoid direct contact with bird droppings in urban public areas, especially for vulnerable or sensitive populations,"
Yu said. "Meanwhile, regular cleaning should also help to mitigate
associated health risks."

========================================================================== Story Source: Materials provided by Rice_University. Note: Content may
be edited for style and length.


========================================================================== Journal Reference:
1. Huiru Zhao, Ruonan Sun, Pingfeng Yu, Pedro J.J. Alvarez. High
levels of
antibiotic resistance genes and opportunistic pathogenic bacteria
indicators in urban wild bird feces. Environmental Pollution,
2020; 266: 115200 DOI: 10.1016/j.envpol.2020.115200 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200713133452.htm

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