by Shane Henson — October 24, 2012—It appears that the “superbugs” responsible for countless hospital infections truly deserve the name. According to University of Leeds researchers, beyond being highly contagious on contact, they can also float on air currents and contaminate surfaces far from infected patients’ beds.
The results of the study, Bioaerosol Deposition in Single and Two-Bed Hospital Rooms: A Numerical and Experimental Study, which was funded by the Engineering and Physical Sciences Research Council, may explain why, despite strict cleaning regimes and hygiene controls, some hospitals still struggle to prevent bacteria moving from patient to patient, say the researchers.
It is already recognized that hospital superbugs, such as MRSA and C. difficile, can be spread through contact. Patients, visitors or even hospital staff can inadvertently touch surfaces contaminated with bacteria and then pass the infection on to others, resulting in a great stress in hospitals on keeping hands and surfaces clean.
But the University of Leeds research showed that coughing, sneezing or simply shaking the bedclothes can send superbugs into flight, allowing them to contaminate recently cleaned surfaces.
PhD student Marco-Felipe King used a biological aerosol chamber, one of a handful in the world, to replicate conditions in one and two-bedded hospital rooms. He released tiny aerosol droplets containing Staphyloccus aureus, a bacteria related to MRSA, from a heated mannequin simulating the heat emitted by a human body. He placed open Petri dishes where other patients’ beds, bedside tables, chairs and washbasins might be and then checked where the bacteria landed and grew.
The results confirmed that contamination can spread to surfaces across a ward.
“The level of contamination immediately around the patient’s bed was high, but you would expect that. Hospitals keep beds clean and disinfect the tables and surfaces next to beds,” said Dr. Cath Noakes, from the University’s School of Civil Engineering, who supervised the work. “However, we also captured significant quantities of bacteria right across the room, up to 3.5 meters away and especially along the route of the airflows in the room.”
“We now need to find out whether this airborne dispersion is an important route of spreading infection,” added co-supervisor Dr. Andy Sleigh.
The researchers are hoping that computer modeling will help them determine the risk. The findings have been compared to airflow simulations of the mock-up hospital rooms, and the research team has shown that they are able to accurately predict how airborne particles can be deposited on surfaces.
“Using our understanding of airflow dynamics, we can now use these models to investigate how different ward layouts and different positions of windows, doors and air vents could help prevent microorganisms being deposited on accessible surfaces,” said King.
