Study Reveals Common Bacteria Linger on Surfaces, May Spread

This research, published in Infection and Immunity, “is the first to directly investigate that these bacteria can survive well outside a human host, and potentially spread between individuals,” says the study’s senior author Anders Hakansson, PhD, assistant professor of microbiology and immunology.

The researchers found that biofilms of Streptococcus pneumoniae and Streptococcus pyogenes survived for hours on human hands and could be isolated from books, soft and hard toys and other surfaces.

Four out of five stuffed toys tested positive for S. pneumoniae, and cribs and other items tested positive for S. pyogenes.

Tests were conducted before the day care center opened, several hours after the last human contact.

The researchers also found that month-old biofilms of S. pneumoniae and S. pyogenes from contaminated surfaces readily colonize mice.

“Although bacterial colonization doesn’t by itself cause infection, it’s a necessary first step if an infection is going to become established in a human host,” he explains.

Hakansson’s team previously demonstrated that bacteria form hardy, highly structured biofilms when colonizing human tissues.

“Our findings change our ideas about how these bacteria may spread between individuals and, if this spread is shown to be substantial, it should make us more cautious about bacteria in the environment,” says Hakansson.

The scientific literature maintains that one can only become infected by S. pneumoniae and S. pyogenes by breathing in droplets expelled as infected individuals cough or sneeze.

Hakansson concludes that “commonly handled objects contaminated with these biofilm bacteria could act as reservoirs of bacteria for hours, weeks or months, being vehicles of spread upon contact.”

More research is needed to understand how contact with surfaces could spread bacteria between individuals, and to what extent it occurs, Hakansson cautions.

“If this type of spread is substantial, then prevention protocols similar to those now used for intestinal bacteria and viruses — which do persist on surfaces — will need to be implemented,” he says.

“Hand washing, which is well implemented in most day care centers, is very effective in preventing spread and should be encouraged as one measure.”

Any resulting anti-infection precautions would be especially important for people who work with children or in health care settings.

Children, the elderly and others with compromised immune systems are especially vulnerable to infections caused by the bacteria studied.

S. pyogenes commonly causes strep throat in children and can cause skin infections and other serious infection in both children and adults.

S. pneumoniae is widespread in day care centers and a common cause of hospital infections. It is a leading cause of childhood ear infections as well as illness and death from respiratory tract infections in children and the elderly. In developing countries, where fresh water, good nutrition and common antibiotics may be scarce, the bacterium often leads to pneumonia and sepsis, killing 1 million children each year.

Much prior research has found that these bacteria cannot live long outside the human body, and therefore do not linger on inanimate objects.

These studies, however, have used broth-grown planktonic bacteria, or lab cultures, to show that bacteria die rapidly.

Based on his team’s previous research, “we knew this lab-produced form of bacteria may not represent how these pathogens actually grow in the host,” says Hakansson.

Co-authors on the study, “Biofilm Formation Enhances Fomite Survival of S. pneumoniae and S. pyogenes,” are both advanced student researchers at UB: MD/PhD candidate Laura R. Marks is first author and PhD candidate Ryan M. Reddinger is second author.

The research was funded by UB’s School of Medicine and Biomedical Sciences and its Department of Microbiology and Immunology.

Hakansson conducts research through two collaborative UB centers: the Witebsky Center for Microbial Pathogenesis and Immunology and the New York State Center of Excellence in Bioinformatics and Life Sciences.