A study headed by a Virginia Tech researcher suggests that the City of Flagstaff’s reclaimed water system may be a breeding ground for antibiotic-resistant bacteria; however, opinions diverge as to whether the bacteria could ultimately harm residents.
Some researchers say the study’s findings suggest that otherwise normal bacteria living in the system are developing resistance to antibiotics while in the system, according to the Arizona Daily Sun; other researchers doubt the problem is significant.
The researchers claim this is “the only quantitative survey of antibiotic resistance genes in recycled water.” Other scientists note that the researchers simply looked for the presence of these genes in the water rather than examined whether potentially harmful bacteria were present.
Flagstaff’s wastewater is treated in multiple stages, which includes UV treatment and the addition of bleach before it is distributed to irrigate local golf courses, the grounds of city schools such as Northern Arizona University, and municipal parks, according to the Arizona Daily Sun.
The report explains that:
Antibiotic resistance is a growing problem and is a major challenge to human medicine because it results in drugs losing their effectiveness for treating bacterial infections. Bacteria are able to fight antibiotics through many mechanisms, all of which are encoded in their DNA by antibiotic resistance genes (ARGs). ARGs have been found in wastewater treatment systems, which receive antibiotics and resistant gastrointestinal flora excreted by humans. […] This has raised the question about the persistence of ARGs in recycled water.
The researchers specifically looked for the presence of five types of antibiotics at irrigation sites — which included soccer fields, baseball fields, and parks — in Flagstaff: tetracyclines, sulfonamides, macrolides, glycopeptides, and methicillin.
Amy Pruden, the author of the study and an associate professor of civil and environmental engineering at Virginia Tech, told the Arizona Daily Sun that the bacteria might be living and breeding in the city’s reclaimed water system, “except we cannot say for sure to what extent bacteria ‘acquired’ resistance in the purple pipes themselves, or if it was acquired upstream of the purple pipes. […] It is not necessarily a surprise that bacteria are growing […] bacteria grow everywhere and most of them are harmless.” She adds that some types of antibiotic resistance genes occur naturally.
She adds that, “One of the resistance genes detected at one sprinkler head […] is not commonly found in soil or water and allows bacteria to survive vancomycin treatment, which is a last-resort antibiotic used to save human life.”
The City of Flagstaff was compelled to study the matter after Robin Silver, a local physician, and other residents presented their concerns to Flagstaff’s leaders. The city has clearly stated that neither the state nor the United States Environmental Protection Agency regulate antibiotic-resistant genes in water.
Hans-Peter Kohler, an environmental microbiologist with the Swiss Federal Institute of Aquatic Science and Technology, Switzerland, told the newspaper:
The question whether these findings raise a public health issue cannot be so easily answered, as there is not enough data provided on the bacteria that are the carriers of such genes — are they alive, are they pathogenic, do they really grow in the pipe system — and on control systems that have been sampled with the same methods, which I deem necessary comparisons.
“It seems quite preliminary so it’s really impossible to know what the implications are,” stated Gerry Wright, a professor of biochemistry at McMaster University in Ontario, Canada, who specializes in antibiotic resistance. “We’ve done surveys of bacteria and DNA from water samples in the past and consistently find resistance genes so this is no big surprise to me.”
The City of Flagstaff noted:
We understand that studying antibiotic-resistant genes in reclaimed water both at the local and national levels is very early on in its research development. We also understand from this study that no quantitative health risk conclusions can be drawn from this limited information.
Pruden states there is no cause for alarm as most bacteria are actually harmless to humans. She adds:
Water conservation is a very important and necessary goal, but to be successful, it is necessary to fully consider potential risks and reduce them to the best practical extent. Several studies around the world have shown that antibiotic resistant bacteria, including pathogens, survive and sometimes even thrive in wastewater treatment plants. […] More research is needed on reclaimed water systems to determine what risks they may pose, if any, to increasing background levels of resistance and ultimately the number of people that become ill with infections that cannot be treated with antibiotics.
The next course of action, according to the Arizona Daily Sun, is for the city to appoint an advisory panel. Its members would be tasked with developing a plan for studying particulates detected in untreated water, drinking water, and reclaimed water; and how to proceed based on those results. According to the newspaper, the city has “no immediate plans to alter the ways in which reclaimed wastewater is distributed and applied throughout the city.”