Bacteria Can Survive Longer In Environment Than Previously Thought

Anders P. Hakansson, Ph.D. Assistant Professor of Microbiology Department of Microbiology and Immunology Buffalo, NY Interview with:
Anders P. Hakansson, Ph.D.
Assistant Professor of Microbiology
Department of Microbiology and Immunology
Buffalo, NY 14214 What are the main findings of the study:

Dr. Hakansson: During the last couple of years we have shown that Streptococcus pneumoniae, a common colonizer of the nasopharynx in small children and elderly that sometimes cause respiratory infections such as middle ear infections and pneumonia, and Streptococcus pyogenes, a common colonizer of the oropharynx and also the cause of strep throat and skin infections, colonize us humans by forming biofilms; intricate bacterial communities. Biofilms have been studied for a long time but these specific organisms have not been shown to form biofilms during colonization until recently. As biofilms are much more resistant to environmental stresses and antibiotics, we were interested to see whether biofilms formed by these organisms could survive in the environment. The main reason for doing the experiments was that CDC guidelines indicate that spread of these organisms between individuals occur solely by inhalation of bacteria-containing droplets after coughing or sneezing. The risk of spread through surfaces has been estimated to be very low as laboratory experiments over the last 40 years have shown that these bacteria die very rapidly on surfaces. These studies were not, however, done with biofilm bacteria. Laura Marks in the laboratory with help from Ryan Reddinger therefore first tested how long biofilm bacteria could survive on plastic surfaces and found that rather than hours these bacteria were alive even after a month and could be used to successfully colonize animals. This made us interested in understanding if these bacteria survive better on hands, a common way to spread bacteria. And just as on inanimate surfaces, the biofilms survived much better on hands than bacteria grown in laboratory media. Based on these results, we were allowed to sample bacteria from stuffed toys, books, crib linens and others surfaces in a day care center early in the morning before the children arrived, and found both S. pneumoniae and S. pyogenes on these items. The results of the study indicate that these bacteria can survive in the environment longer than we have previously thought and may therefore play a role in spread between individuals. Were any of the findings unexpected?

Dr. Hakansson: Although we hypothesized that biofilms would survive longer than bacteria grown in laboratory medium, we were a little surprised that they survived for so long. We were also a little surprised initially that it was so easy to culture these bacteria from inanimate objects in the day care center. What should clinicians and patients take away from your report?

Dr. Hakansson: These studies add a piece to the puzzle of how these bacteria may spread between individuals, and could be potentially important in preventing spread. The studies are initial and they only suggest that spread of these two bacterial species may occur through surfaces. Other studies will be needed to understand how important this type of spread is. If it is common, it may be worth revisiting the recommendations for handling colonization and infection with these  bacteria in health care settings and in environments dealing with children, such as schools and day care centers. As always, good hand hygiene, and keeping surfaces clean goes a long way to prevent spread both for those bacteria and other microorganisms in our environment. What recommendations do you have for future research as a result of this study?

Dr. Hakansson: As mentioned above, future studies should investigate the level of spread that occurs through surfaces and fomites for these two bacteria. If it is substantial, new recommendations limiting the spread of these bacteria can be implemented in the environments these bacteria are most often found, such as hospitals, day care centers and schools.


Biofilm Formation enhances Fomite Survival of S. pneumoniae and S. pyogenes

Laura R. Marks, Ryan M. Reddinger, and Anders P. Hakansson

Infect. Immun. IAI.01310-13; published ahead of print 26 December 2013, doi:10.1128/IAI.01310-13