Whenever there is a food poisoning outbreak linked to produce, we have told you that one source of the pathogen may be bird droppings. A new study conducted at Rice University and published in Elsevier journal Environmental Pollution states that bird droppings carry antibiotic resistant bacteria and may “harbor abundant” numbers of the pathogen along with resistance genes.
The study was conducted by environmental engineers and led by postdoctoral research associate Pingfeng Yu of Rice’s Brown School of Engineering and co-author Pedro Alvarez.
Earlier studies showed that bird-borne antibiotic resistant genes (ARGs) and bacteria can be transferred to humans through these vectors: swimming, contact with bird feces or contaminated soil, and inhaling aerosolized fecal particles.
Alvarez told Science Daily, “We still do not fully understand what factors exert selective pressure for the occurrence of ARGs in the gastrointestinal system of wild urban birds. 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 scientists compared fresh fecal samples from each bird species found in the Houston area in the winter and summer months to samples taken from poultry and livestock that may carry some of the same mutations. They found that antibiotic resistant genes in all species had significant resistance to tetracycline beta-lactam and sulfonamide antibiotics. And the “relatively high abundance” of ARGs were comparable to those found in fresh feces of domesticated poultry that are given antibiotics in their feed.
Alvarez added, “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.”
They also found that ARGs were in the soil up to 1 inch deep around the bird droppings, which may play a role in contamination of crops.
The researchers concluded that since bird droppings carry antibiotic resistant bacteria, people should avoid contact with them, especially vulnerable groups who are at high risk for complications from infections. The bacteria can cause respiratory infections, food poisoning, and sepsis.
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
