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Image result for icu A recent study of microbiomes (microbial communities) of patients admitted to intensive care units (ICU) found that they had rapid loss of normal, “health promoting” bacteria", which resulted in the "overgrowth of disease-promoting pathogenic bacteria (dysbiosis), which, in turn, makes patients susceptible to hospital-acquired infections, sepsis, and organ failure". In other words, serious illnesses disrupt human microbial communities, as do treatments, medicines, antibiotics, and lack of proper nutrition in intensive care units. Interestingly, they observed "large depletions of organisms previously thought to confer anti-inflammatory benefits, such as Faecalibacterium". Faecalibacterium prausznitzii has been discussed in other posts as an incredibly important beneficial bacteria for health, a keystone species in the gut (here and here).

The researchers, who took skin, oral, and fecal samples at two time points, expressed surprise over how rapidly the microbial communities changed, and suggested that possible treatments for the micobial communities being out-of-whack (dysbiosis) are "probiotics or with targeted, multimicrobe synthetic “stool pills” that restore a healthy microbiome in the ICU setting to improve patient outcomes." In other words, "restoration of a healthy gut microbiome may be important for improving outcomes in critically ill patients".  Of course.... From Science Daily:

ICU patients lose helpful gut bacteria within days of hospital admission

The microbiome of patients admitted to the intensive care unit (ICU) at a hospital differs dramatically from that of healthy patients, according to a new study published in mSphere. Researchers analyzing microbial taxa in ICU patients' guts, mouth and skin reported finding dysbiosis, or a bacterial imbalance, that worsened during a patient's stay in the hospital. Compared to healthy people, ICU patients had depleted populations of commensal, health-promoting microbes and higher counts of bacterial taxa with pathogenic strains -- leaving patients vulnerable to hospital-acquired infections that may lead to sepsis, organ failure and potentially death

What makes a gut microbiome healthy or not remains poorly defined in the field. Nonetheless, researchers suspect that critical illness requiring a stay in the ICU is associated with the the loss of bacteria that help keep a person healthy. The new study, which prospectively monitored and tracked changes in bacterial makeup, delivers evidence for that hypothesis. "The results were what we feared them to be," says study leader Paul Wischmeyer, an anesthesiologist at the University of Colorado School of Medicine. "We saw a massive depletion of normal, health-promoting species."

Wischmeyer, who will move to Duke University in the fall, runs a lab that focuses on nutrition-related interventions to improve outcomes for critically ill patients. He notes that treatments used in the ICU -- including courses of powerful antibiotics, medicines to sustain blood pressure, and lack of nutrition -- can reduce the population of known healthy bacteria. An understanding of how those changes affect patient outcomes could guide the development of targeted interventions to restore bacterial balance, which in turn could reduce the risk of infection by dangerous pathogens.

Previous studies have tracked microbiome changes in individual or small numbers of critically ill patients, but Wischmeyer and his collaborators analyzed skin, stool, and oral samples from 115 ICU patients across four hospitals in the United States and Canada. They analyzed bacterial populations in the samples twice -- once 48 hours after admission, and again after 10 days in the ICU (or when the patient was discharged). They also recorded what the patients ate, what treatments patients received, and what infections patients incurred.

The researchers compared their data to data collected from a healthy subset of people who participated in the American Gut project dataset. (American Gut is a crowd-sourced project aimed at characterizing the human microbiome by the Rob Knight Lab at the University of California San Diego.) They reported that samples from ICU patients showed lower levels of Firmicutes and Bacteroidetes bacteria, two of the largest groups of microbes in the gut, and higher abundances of Proteobacteria, which include many pathogens.

Wischmeyer was surprised by how quickly the microbiome changed in the patients. "We saw the rapid rise of organisms clearly associated with disease," he says. "In some cases, those organisms became 95 percent of the entire gut flora -- all made up of one pathogenic taxa -- within days of admission to the ICU. That was really striking." Notably, the researchers reported that some of the patient microbiomes, even at the time of admission, resembled the microbiomes of corpses. "That happened in more people than we would like to have seen," he says.....In addition, now that researchers have begun to understand how the microbiome changes in the ICU, Wischmeyer says the next step is to use the data to identify therapies -- perhaps including probiotics -- to restore a healthy bacterial balance to patients.

Sad, but not surprising results. It highlights the damage repeated courses of antibiotics, and even illness, do to gut microbial communities. The researchers write that during a prolonged stay in ICU they found the emergence of "ultra-low-density communities" (only 1 to 4 bacteria species) in patients. From Science Daily:

Critically ill ICU patients lose almost all of their gut microbes and the ones left aren't good

Researchers at the University of Chicago have shown that after a long stay in the Intensive Care Unit (ICU) only a handful of pathogenic microbe species remain behind in patients' intestines. The team tested these remaining pathogens and discovered that some can become deadly when provoked by conditions that mimic the body's stress response to illness.

"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," he says. The current study supports this idea. Alverdy and Olga Zaborina, a microbiologist, wanted to know what happens to the gut microbes of ICU patients, who receive repeated courses of multiple antibiotics to ward off infections.

They found that patients with stays longer than a month had only one to four types of microbes in their gut, as measured from fecal samples -- compared to about 40 different types found in healthy volunteers.

Four of these patients had gut microbe communities with just two members-- an infectious Candida yeast strain and a pathogenic bacterial strain, such as Enterococcus faecium or Staphylococcus aureus and other bugs associated with hospital-associated infections. Not surprisingly, almost all of the pathogenic bacteria in these patients were antibiotic resistant.