How infections travel around hospitals
December 6, 2016
For all the medicine, medical equipment and doctors around, hospitals are actually good places to get sick. According to the Centers for Disease Control and Prevention, 722,000 people picked up an infection at hospitals in 2011.
The CDC and individual hospitals are having success fighting these hospital-acquired infections (HAIs), reducing some types by up to 50 percent. With more than 125 million people visiting the hospital every year, however, understanding and preventing HAIs is still an extremely important means of improving public health.
Now new research from Duke University has shown exactly how those infections spread through hospitals.
Dr. Deverick Anderson, an associate professor of medicine at Duke and lead author of the study, examined how bacteria and viruses jump between the three sides of what epidemiologists call the “transmission triangle.” In hospitals, infectious agents jump back and forth between patients, their room and equipment and the medical personnel.
The question is how these agents move. Hospital protocols call for washing hands, regularly cleaning surfaces and other measures to stop the spread, but Anderson and his colleagues wanted to see how the infections were still moving.
The researchers used cultures to track how those agents moved over 12-hour shifts. They took samples from 40 nurses’ scrubs at the beginning and end of a total of 120 shifts in Duke’s intensive care unit, to see onto what the infections jumped. They also took swabs from each patient the nurses visited in those shifts and the bed, bedrail and supply cart in each patient’s room for a total of more than 5,000 cultures over the course of the study.
They specifically zeroed in on five common pathogens that lead to tricky-to-treat infections: methicillin resistant Staphylococcus aureus (MRSA), an antibiotic-resistant staph infection; S. maltophilia, a common bacteria that lives on the human body; Acinetobacter and P. aeruginosa, two pathogens that commonly live in the environment but cause human disease; and Klebsiella, a bacteria that causes pneumonia and other illnesses.
All told, the researchers tallied 22 instances where at least one of those five pathogens jumped from one side of the triangle to another. Pathogens moved from scrubs to patients and from the room to the scrubs six times each. The last ten transmissions went from patients to their rooms.
The pathogens were most likely to take hold on the bedrails in patient rooms and on the sleeves and in the pockets of the scrubs, three places closely related to hands. While the researchers did not see any instances where the pathogens leapt from the scrubs to the patients or their rooms, the hands seem to be a primary vector for transmitting disease.
Anderson says a key measure in preventing HAIs from spreading is health care providers sticking to protocols like hand washing and wearing gloves every time they enter a patient room, regardless of whether they even touch the patient or not.
“Oftentimes, especially when dealing with very sick patients, health care personnel may feel a conflict between providing care and following protocol that helps prevent pathogen transmission,” Anderson said in a press release. “Our study shows following prevention strategies has to be a top priority, and that health care providers should be looking for ways to improve the likelihood that they are.”
With flu season coming up, the CDC is advocating the same thing, strict adherence to hand washing protocols, as part of their effort to stop the spread of the flu through healthcare settings. Protocols like those have been helping to fight HAIs, but with more vigilance and studies that show exactly where that vigilance needs to be directed, the number of HAIs can drop even further.
Daniel Lane covers science, medicine, engineering and the environment in North Carolina.