Hospital wastewater systems are a reservoir for drug-resistant bacteria: 5 study findings

Hospital wastewater systems are a breeding ground for drug-resistant bacteria, a new study conducted by the National Institutes of Health suggests.  

For the investigation, researchers collected samples from the pipes beneath the intensive care unit in the NIH's flagship hospital in Bethesda, Md., and from outside manholes that drain hospital wastewater. Researchers then conducted whole-genome analyses on the samples to determine resistance to antibiotics.

Here are five things to know.

1. The majority of samples researchers studied from the pipes and sewers tested positive for bacterial plasmids that confer resistance to carbapenems, a "last-resort" antibiotic given to hospital patients who develop an infection from a multi-drug resistant bacterium.

2. While many of these bacteria are present in hospital wastewater systems, these superbugs are not common elsewhere in the hospital. Of 217 samples analyzed from high-touch surfaces such as sinks, countertops, door knobs and computers — only three (1.4 percent) had carbapenems-resistant plasmids, or ring-shaped pieces of DNA.

3. Additionally, only 11 of 340 samples collected from the drains inside the hospital tested positive for this plasmid. This reveals these superbugs are not observed in places where patients had access.

4. These findings and comparisons suggest that hospital efforts to control drug-resistant organisms on hospital surfaces have been successful at reducing the risk of patient infections. However, study co-author Karen Frank, MD, PhD, explains how the findings raise another important question: "How much should we care that there are a bunch of plasmids down in the wastewater system if they're not infecting our patients?"

5. The findings add to a growing body of evidence that hospital wastewater systems may play a role in antibiotic resistance. Some experts believe these resistant populations flourish in hospital wastewater and sewers near the hospital because of the regular use of antibiotics.   

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