KEY BISCAYNE, Fla. – A swimming advisory has been issued for two South Florida beaches after water samples showed high levels of fecal bacteria.

The Florida Department of Health in Miami-Dade issued the warning for the following beaches on Wednesday:

CRANDON SOUTH (Crandon Park Key Biscayne)

NORTH SHORE (73rd Street and Collins Avenue)

The advisory was issued after two consecutive water samples exceeded the recommended standards for enterococci. The health department advises visitors to not swim at either beach until the advisory is lifted.

Enterococci bacteria, like those shown here, can be resistant to common antibiotics, making infections difficult to treat. Centers for Disease Control and Prevention (CDC)

Children and adults with weakened immune systems are most vulnerable to infections. Authorities recommend not swimming at these beaches. The most common symptoms associated include vomiting, diarrhea, headache and fever. Ear, eye, nose and throat infections are also possible.

The same beaches were closed multiple times last year over the same issue and later reopened.

The advisories will remain in effect for the beaches until levels lower. For more information about the advisory, visit the Florida Healthy Beaches Program site or call 850-245-4240.