Superbugs, Sewage and the Oceans

Environmental Protection Agency found drug-resistant bacteria in Los Angeles sewage plant.


Sewage treatment plants are all about keeping it clean--water, that is. But there may be a problem.

The Environmental Protection Agency (EPA) recently found a drug-resistant “superbug” in an unidentified Los Angeles sewage plant.

Carbapenem-resistant enterobacteriaceae (CRE) caused outbreaks in hospitalized patients at three Los Angeles hospitals. The bacteria is resistant to many antibiotics and very difficult to treat.

Hospitals, like homes and any building with a bathroom, release untreated sewage into sewers, which carry the waste to a treatment plant. In addition, since hospitals also use antibiotics to treat infections, the hospital sewage contains antibiotic residues.

The antibiotics come into contact with bacteria during the mixing process. Antibiotics kill weaker bacteria, promoting the growth of more drug-resistant bacteria in the sewage sludge.

CRE is particularly dangerous because it is resistant to nearly all antibiotics and has a very high mortality rate.

Research has found that sewage plants are not killing superbugs, a collective term for bacteria that have become resistant to most antibiotics. Pedro Alvarez, PhD, is one of the scientists studying the problem. Dr. Alvarez is a professor of environmental engineering at Rice University.

Dr. Alvarez commented in an interview for the LA Times that sewage plants are becoming “luxury hotels” where superbugs can multiply and become stronger. Dr. Alvarez said that the treatment of choice in most sewage plants--chlorine--is just not doing it.

The EPA's analysis found CRE in the sewage plant itself. However, the analysis did not include testing water released after treatment. In Los Angeles, sewage plants release treated water many miles offshore.

Doctors have become increasingly concerned at the number of people who are acquiring drug-resistant infections outside of the hospital. This report indicated that even treated sewage might be a factor in these community-acquired infections.

"The idea of CRE flowing down our sewer pipes gets me nervous," James McKinnell, MD, was quoted in the LA Times. "We should be testing our runoff."

Dr. McKinnell is an infectious disease expert at the Los Angeles Biomedical Research Institute.

Although waters off the California coast are monitored, the focus is on total bacteria count, not whether the organisms are drug-resistant. Surfers, swimmers and those who dive in the waters may be exposed to bacteria in the water.

The Centers for Disease Control and Prevention noted that water-borne infections can also include other organisms like Shigella, E. coli, giardia and campylobacter. Many of these organisms cause gastrointestinal diseases. People who are most at risk include those who have weak immune systems, children and the elderly.