A September 2014 sewer line break in unincorporated Pinellas County caused untreated wastewater to flow into a St. Petersburg neighborhood and Boca Ciega Bay at a rate of 250 to 500 gallons a minute.
Now, researchers from the University of South Florida investigating the aftermath of the break have found dangerous antibiotic-resistant bacteria in the untreated wastewater that had gushed into both neighborhoods and Boca Ciega Bay.
Their findings, just published in the journal Applied and Environmental Microbiology and announced in a news release, raise several significant public health concerns.
First, a strain of bacteria found in the water tested resistant to vancomycin, an antibiotic considered to be a “last resort” treatment for serious infections that do not respond to other antibiotics. Second, the combination of aging sewer infrastructure and an increase in stormwater flooding with extreme rain events increases the likelihood of more spills occurring and continuing to spread these dangerous, drug-resistant bacteria in populated areas. Finally, the researchers found that the vancomycin-resistant enterococci (VRE) bacteria found in the untreated waste water has a gene capable of transferring vancomycin resistance to other kinds of bacteria. This fuels the greater problem of increasing antibiotic resistance.
The researchers sampled the water and soil for seven weeks following the spill from the broken sewer line which totaled about 500,000 gallons of released untreated sewage. Genes from the vancomycin-resistant bacteria were detected for nearly two weeks after the spill.
“While we have known that raw sewage contains many disease-causing bacteria, this experience tells us that sewage and fecal pollution also carry vancomycin-resistant bacteria,” said Dr. Valerie Harwood, a professor in the USF Department of Integrative Biology and study co-author. “Most VRE are confined to hospitals, but detecting them in waters of the Tampa Bay community is quite concerning. People need to be aware of what may be entering the water after heavy rains, accidental spills, or after intentional sewage releases.”
According to lead study author, USF Ph.D. student Suzanne Young, their finding is also a public health “wake-up call” to be more prudent with the use of antibiotics in both humans and animals.
“The more antibiotics we use — in both humans and animals — the more the antibiotic resistant organisms and antibiotic resistance genes can enter the environment and contribute to the spread of antibiotic resistance, especially for those drugs considered the “last resort’ for many infections,” explained Young. “Also, we need to invest in more sustainable infrastructure for managing stormwater and wastewater to decrease the frequency of sewage spills.”
The researchers also called for more monitoring of VRE and the presence of resistance genes outside of the hospital setting where they are more commonly found.
According to the authors, the bacteria they discovered in the sewage spill waters — VRE — are on the U.S. Center for Disease Control’s list of serious threats.
“The spread of pathogens with high levels of vancomycin resistance beyond hospitals and into the community is a public health threat,” concluded the researchers. “While further studies are needed to better define risks, knowing these pathogens are in Tampa Bay sewage is an important development.”