December 29, 2013

Researchers report strep bacteria can last for up to several months on objects

Protocols for cleaning day care centers and home nurseries may need to change, authors of a new study say.

By Geoffrey Mohan
Los Angeles Times

That crib toy you got your son? It might be just the thing to give him strep throat, according to a new study.

The bacteria that cause strep throat may linger far longer on inanimate objects than previous lab tests suggested, according to University of Buffalo researchers.

Streptococcus pneumoniae, the leading cause of ear and respiratory tract infection in children, and Streptococcus pyogenes, the bacterial culprit behind strep throat and skin infections, lingered on surfaces in cribs, toys and books many hours after they had been cleaned, according to a study published Friday in the journal Infection and Immunity.

Conventional wisdom held that both bacteria died quickly outside a human host, and that the prevailing means of infection came through immediate human contact or via expelled droplets from coughing or sneezing.

“These findings should make us more cautious about bacteria in the environment,” said Anders Hakansson, a University of Buffalo School of Medicine and Biomedical Sciences microbiologist who is senior author of the study.

Hakansson said he believes that some items could serve as reservoirs where the bacteria can linger for as long as several months.

Researchers based their findings on tests conducted on items in a day care center, where they found four of five stuffed toys tested positive for S. pneumoniae, and several other surfaces showed evidence of S. pyogenes – even after cleaning. The testing was done in the early morning before the center opened, long after the last human contact with the objects.

The Buffalo research team last year showed that bacteria colonizing human skin can form stubborn biofilms that are hardier than other forms of bacteria.

Knowing how stubborn these biofilms can be, Hakansson and doctoral students Laura R. Marks and Ryan M. Reddinger wanted to test whether conventional methods of determining bacterial survival, using cultures grown in a laboratory, accurately depicted the form of the pathogens in day care centers and home nurseries.

“We knew that this form of bacteria may not represent how they actually grow in the host,” Hakansson said in a statement. “We wanted to know how well biofilm bacteria survive outside the body.”

The researchers also showed that month-old biofilms of the bacteria, taken from contaminated objects, could readily colonize in mice, a likely sign that they can infect humans.

The researchers said it was unclear how much human infection with the strep bacteria is attributable to potential biofilm reservoirs on inanimate objects. But they suggested that protocols for cleaning day care centers and home nurseries may need to change.

While strep infections tend to be little more than a painful inconvenience in the developed world, in areas that lack adequate water, nutrition and antibiotics, they kill 1 in 1 million children annually, through respiratory tract infections, pneumonia and sepsis.

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