New research: Nasty bacteria biofilm may stay alive for hours, even after washing

Long-living bacteria on inanimate objects endangers children and hospital patients.

A daycare in Israel (photo credit: Zoog Productions)
A daycare in Israel
(photo credit: Zoog Productions)
Many parents and even scientists think that bacteria that cause colds, ear infections and strep throat quickly die when left on furniture, books, toys or hospital surfaces and exposed to the air. Even numerous scientific studies have concluded that two common bacteria, Streptococcus pneumoniae and Streptococcus pyogenes, cannot live for long outside the human body.
But we may need to think again, according to research from New York State’s University of Buffalo. The findings, recently published in Infection and Immunity, show that such bacteria do persist on surfaces for far longer than previously believed, even after the surfaces are cleaned.
The authors said their findings suggested that additional precautions may be necessary to prevent infections, especially in settings such as schools, day care centers and hospitals.
“These findings should make us more cautious about bacteria in the environment, since they change our ideas about how these particular bacteria are spread,” said senior author Prof.
Anders Hakansson, a microbiologist and immunologist at the UB school of medicine and biomedical sciences. “This is the first paper to directly investigate that these bacteria can survive well on various surfaces, including hands, and potentially spread between individuals.”
The Jerusalem Post asked the Health Ministry about the new study and its implications for hospital, kindergarten and day center hygiene. The ministry said it was “aware that objects in daycare centers and kindergartens can be a possible source for the spread of infectious diseases, and thus there are detailed guidelines via the Economy Ministry [for] these institutions.”
It did not indicate, however, that it knew inanimate objects could spread disease even after so many hours had passed.
S. pneumoniae – a leading cause of ear infections in children, as well as of morbidity and mortality from respiratory tract infections among children and the elderly – is widespread in daycare centers and a common cause of hospital infections, Hakansson said. And in developing countries, where fresh water, good nutrition and common antibiotics may be scarce, S. pneumoniae often leads to pneumonia and sepsis, killing one million children every year. S. pyogenes commonly causes strep throat and skin infections in schoolchildren, but can also cause serious infection in adults.
The researchers found that in the daycare center, four out of five stuffed toys tested positive for S. pneumoniae, and several surfaces, such as cribs, tested positive for S. pyogenes, even after being cleaned. The testing was done just prior to the center opening in the morning, so it had been many hours since the last human contact.
Hakansson and his co-authors became interested in the possibility that some bacteria might persist on surfaces, when they published work last year showing that bacteria form biofilms when colonizing human tissues. They found that these sophisticated, highly structured biofilm communities were hardier than other forms of bacteria.
“Bacterial colonization doesn’t, by itself, cause infection, but it’s a necessary first step if an infection is going to become established in a human host,” he explained. “Children, the elderly and others with compromised immune systems are especially vulnerable to these infections.”
He explained that studies of how long bacteria survived on inanimate objects had used cultures grown in laboratory media, called broth-grown planktonic bacteria, and invariably showed that bacteria died rapidly.
“But we knew that this form of bacteria may not represent how they actually grow in the host,” he said. “Since discovering that biofilms are key to the pathogenesis of S. pneumoniae, we wanted to find out how well biofilm bacteria survive outside the body.”
The UB experiments found that month-old biofilm of S.
pneumoniae and S. pyogenes from contaminated surfaces readily colonized mice, and that biofilms survived for hours on human hands and persisted on books, soft and hard toys, and surfaces in a day care center – in some cases, even after a thorough cleaning.
“In all of these cases, we found that these pathogens can survive for long periods outside a human host,” said Hakansson. But, he continued, the scientific literature maintains that you can only become infected by breathing in infected droplets expelled when infected individuals cough or sneeze.
“Commonly handled objects that are contaminated with these biofilm bacteria could act as reservoirs of bacteria for hours, weeks or months, spreading potential infections to individuals who come in contact with them,” he concluded. He cautioned that more research was necessary to understand under what circumstances this type of contact led to spread between individuals.
“If it turns out that this type of spread is substantial, then the same protocols that are now used for preventing the spread of other bacteria, such as intestinal bacteria and viruses, which do persist on surfaces, will need to be implemented especially for people working with children and in health-care settings,” he added.