It may not sound healthy, but having your intestines crowded by a wide variety of microbial life is a very good thing. Unfortunately for Intensive Care Unit (ICU) patients, it has been found that they are very likely to lose nearly all their microbes over the course of a hospital stay, making them vulnerable to dangerous infections.
A study recently published in the journal mBio details how ICU patients are particularly vulnerable to a life-threatening systemic infection known as sepsis.
"I have watched patients die from sepsis - it isn't their injuries or mechanical problems that are the problem," John Alverdy, a gastrointestinal surgeon and one of two senior authors on the study, said in a recent statement.
"Our hypothesis has always been that the gut microflora in these patients are very abnormal, and these could be the culprits that lead to sepsis."
According to the US Centers of Disease Control and Prevention (CDC), sepsis is becoming increasingly more prevalent in the United States, with nearly twice as many lab-confirmed cases seen in 2008 (about 1,141,000 infections) than were seen in the year 2000.
To determine exactly why this is occurring, Alverdy and his colleague Olga Zaborina at the University of Chicago wanted to know what happens to the gut microbes of ICU patients who receive repeated courses of multiple antibiotics to ward off infections.
Stunningly, they found that over time, these anti-infection treatments were helping patients become more vulnerable to sepsis. This was because while the standard healthy person has over 40 different types of bacteria living in their gut at one time, antibiotic treatment can cull that number to up-to only four different types of microbes. Not surprisingly, these survivor microbes are almost always found to be highly resistant to standard antibiotics.
Alverdy adds that it's not only about which microbes are left, "but how they behave when provoked by the harsh and hostile conditions of critical illness."
Zaborina explained that traditionally microbial populations in the gut balance one another out, suppressing their virulence, "but if you do something to one of them, then that can change their behavior."
One such change the team found was with opioids (pain killers). The presence of this drug can potentially switch remaining microbes from a peaceful co-existence to virulence - leading to an overwhelming infection. However, how and why these reactions occur remains unclear.
More work will need to be done, while researchers struggle to find ways to keep antibiotic-resistant gut microbes calm and harmless even in the ICU.