While hospital surfaces are known to carry potentially dangerous microbes, the majority of hospital-acquired bacteria might be the ones patients bring in themselves, according to a study published Wednesday in Science Translational Medicine.
For the study, a research team led by University of Chicago (UC) researchers sought to better understand a hospital's microbiome by mapping the spread of bacteria in a hospital's first year. The researchers theorized that a hospital might have a distinctive microbiome just as the human gut has one. The researchers said understanding a hospital's mix of microbes, as well as how those microbes move throughout the facility, might help reduce hospital-acquired infections.
The researchers launched the project, called the Hospital Microbiome Project, to coincide with the 2013 opening of the UC's Center for Care and Discovery. Two months before the center opened, researchers swabbed the center's surfaces to collect samples of omnipresent microorganisms such as bacteria, fungi, and viruses.
Researchers continued collecting samples during the first year that the hospital admitted patients. In total, the researchers collected 6,523 samples in 10 patient rooms and two nurse stations on two floors, and monitored the center's humidity, temperature, and ventilation. They also collected more than 10,000 samples from 252 patients.
The researchers compared patients' microbial profiles from the time of their arrival to the time they were discharged, and used statistical methods to determine what influenced microbial profiles.
The researchers noted that one of the study's limitations is that it is observational, and it does not draw connections between patients' microbes and any conditions they developed.
Overall, 20 patients who participated in the study were diagnosed with a hospital-acquired infection. That figure is comparable to CDC's estimate that about one in 25 hospitalized patients acquires such infections. According to the study, however, the bacteria responsible for the patients' infections were not found in samples collected from their rooms, nurses, or doctors, which the researchers said suggests that the microbes causing the infections might not have come from the hospital.
The researchers highlighted several interesting trends in microbial transmission, which they say could be helpful for hospitals looking to reduce the presence of harmful bacteria.
For instance, they found that, prior to opening, bacteria in the hospital primarily consisted of microbes commonly found in soil and water, but after the facility started admitting patients, new microbes associated with human skin—such as Corynebacterium, Staphylococcus, and Streptococcus—began to populate within the hospital. Those bacteria are responsible for infections such as Methicillin-resistant Staphylococcus aureus and pneumonia, Science reports. Further, the study found some of those new microbes remained even after routine disinfections and cleanings using ammonia or bleach.
The researchers also found the makeup of the microbes changed after each patient's admission to the hospital. On day one, microbes tended to transfer from surfaces in the patient's room to the patient, but by the second day, the patient's microbes took over the room. According to the study, the bacteria in patients' rooms, in particular on their bedrails, consistently resembled their own. And over time, medical treatments, such as antibiotics, had little effect on the microbes travelling between a patient's skin and the room, according to the study.
Further, the researchers found microbial exchanges among hospital staff increased in the summer, particularly during humid weather. They also found the amount of antibiotic-resistant bacteria increased with patients' hospital stays.
Jordan Peccia, a Yale University engineer who studies disease transmission, said the findings serve as the "first environmental verification" that "hospital-associated infection pathogens might be coming in with patients."
Jack Gilbert, a microbial ecologist who led the study, said the findings show that patients who are diagnosed with hospital-acquired infections mostly likely "already had those bacteria when they were admitted." He said if this is true, then there will be a "paradigm shift in how we think of hospital-acquired infections." Gilbert added that these findings could be used to "design the most accurate intervention possible."
Gilbert said, next, he hopes to collect more detailed information to track how patients' movement within a hospital affects the number and type of microbes exchanged (Kuhrt, FierceHealthcare, 5/25; Potenza, The Verge, 5/24; Price, Science, 5/24; Staedter, Live Science, 5/24).
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