According to lead researcher Renata Picao, the "super bacteria" entered the city's waterways when sewage coming from local hospitals got channeled into the bay.
"We have been looking for 'super bacteria' in coastal waters during a one-year period in five beaches," Picao told CNN during a visit to her lab. "We found that the threats occur in coastal waters in a variety of concentrations and that they are strongly associated with pollution."
The news comes as Rio prepares to host hundreds of thousands of athletes and tourists during next month's Summer Olympics.
