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.
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
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
It did not indicate, however, that it knew inanimate
objects could spread disease even after so many hours had passed.
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
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.
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.”
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
“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
“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
“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.