Numerous scientific studies have concluded that two common bacteria that cause ear infections, strep throat and other more serious infections cannot live for long outside the human body. This has led to a long held belief that these bacteria won`t linger on objects like furniture, dishes or toys.
But researchers at the University of Buffalo have found that the two bacteria that are the main cause of infections in children and the elderly - Streptococcus pneumoniae and Streptococcus pyogenes – do persist on surfaces longer than appreciated. This suggests that additional precautions may be necessary to prevent infections in places such as schools, daycare 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," says senior author Anders Hakansson, assistant professor of microbiology and immunology at the UB School of Medicine and Biomedical Sciences.
S. pyogenes is a common cause of strep throat and skin conditions in schoolchildren, and the bacteria can also cause severe infections in adults.
S. pneumonia is a leading cause of morbidity and mortality from respiratory tract infections in children and the elderly, and is also a leading cause of ear infections.
Previous research from the team showed that certain bacteria develop biofilms when they colonize human tissues. A biofilm is a group of microorganisms that bind together on a surface.
The researchers found that these bacteria are stronger than other bacteria that do not form biofilms, leading them to believe that the bacteria may linger on surfaces.
To test this hypothesis, the investigators analyzed a number of objects, including books, stuffed toys and cribs, in a child daycare center. The testing was done just prior to the center in the morning, ensuring that it had been several hours since the last human contact.
The researchers found that four out of five stuffed toys tested positive for S. pneumonia, and several surfaces, such as cribs, tested positive for S. pyogenes.
"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 explains.
The researchers then tested a one month old biofilm of S. pyogenes and S. pneumonia to see whether the bacteria could colonize. Results showed that the biofilms could effectively colonize a mouse model, and survive many hours on human hands, books, toys and surfaces – even after cleaning.
"Commonly handled objects that are contaminated with these biofilm bacteria could act as reservoirs of bacteria for hours, weeks or months, spreading potential infections," says Hakannson. He cautions that more research should be done to better understand under what circumstance this type of contact leads to spread between individuals.
"Cleaning, even with soap and water, could make a big difference," he says, "as we saw that the bacteria survive much better on hands."