"I chose Wake Forest’s MD/PhD program based on the Microbiology and Immunology Department.  During my interviews, I was really impressed by the faculty and quality of research being done.  In addition, the focus of research on host-pathogen interactions would easily translate to my medical studies.  I also liked the opportunities that a smaller department would allow with more interaction and hands on training from the faculty."

Streptococcus pneumoniae and Haemophilus influenzae mixed infection biofilms in the chinchilla model of otitis media

Otitis media (OM) is the number one reason for pediatric office visits, new antibiotic prescriptions and surgery in children. The two most commonly isolated pathogens from otitis media infections are Streptococcus pneumoniae (40-50%) and Haemophilus influenzae (30-40%). Once established, these bacteria can cause persistent and/or recurrent infections. One hypothesis to explain this persistence is the presence of biofilms. A biofilm is a structured, sessile bacterial community attached to a surface surrounded by an extracellular matrix. It is inherently resistent to host clearance mechanisms and antibiotics. While current data indicate that most OM infections are polymicrobial, the majority of work done on experimental OM to date has used only single infection models. Our lab has a well established chinchilla model for experimental OM with H. influenzae, but there are only in vitro models for S. pneumoniae biofilm formation. The goal of this research was to establish an in vivo model for S. pneumoniae biofilm formation using the chinchilla model and to determine what happens in a mixed infection biofilm with S. pneumoniae and H. influenzae. Chinchillas were infected with S. pneumoniae strain TIGR4 and harvested at 1, 3, 7 and 12 days post-infection. Effusions were plated for bacterial counts and the macroscopic mass (biofilm) was fixed for microscopy. OM infection with viable biofilm was present at all four time points. Chinchillas were then infected with 10:1 and 1:1 ratios of H. influenzae to S. pneumoniae. At the 10:1 ratio, all S. pneumoniae bacteria were cleared by day 7, while H. influenzae persisted. However, at the 1:1 ratio and 10:1 ratio, with 10-fold higher inoculum, both bacteria persisted and were present in the biofilm and effusion at 7 days.