Prolonged ICU Stay Depopulates Healthy Gut Microbiota

A new study shows that a long stay in the intensive care unit (ICU) drastically reduces the number of microbe species found in patients' intestines.

Researchers at the University of Chicago (IL, USA), Argonne National Laboratory (Argonne, IL, USA), and other institutions analyzed fecal samples of selected patients during a prolonged stay in an ICU to find the 16S rRNA amplicon composition of their gut bacteria. They found that the 30% of the patients had only 1–4 types of microbes present, compared to about 40 found in healthy volunteers. Four of the patients presented a lowly two-member community comprised of an infectious Candida yeast strain and a pathogenic bacterial strain, such as E. faecium or S. aureus.

To examine the virulence potential of the two-member communities, the researchers examined how the Caenorhabditis elegans worm behaved during nutrient deprivation and exposure to opioids, mimicing local conditions in the gut during critical illness. Under conditions of nutrient deprivation, the bacterial members attenuated the virulence of fungal members, but maintained a commensal lifestyle. However, exposure to opioids led to a breakdown in this commensalism and the creation of a potentially deadly pathogenic state. The study was published on September 23, 2014, in mBio.

“They've got a lot of bad guys in there, but the presence of bad guys alone doesn't tell you who's going to live or die,” said lead author gastrointestinal surgeon John Alverdy, MD, of the University of Chicago. “It's not only which microbes are there, but how they behave when provoked by the harsh and hostile conditions of critical illness.”

The researchers suggest that doctors try to find ways to minimize the excessive use of antibiotics and stabilize the microbes remaining in ICU patients' guts. They suggest this might be achieved by application of phosphate-polyethylene glycol (Pi-PEG), an antivirulence agent that creates local phosphate abundance, thus preventing opioid-induced virulence among pathogenic communities and rescuing the commensal lifestyle.

Related Links:
University of Chicago
Argonne National Laboratory