Dragana Ajdic Lab : Research


Biofilms are microbial communities that form on a variety of surfaces. Biofilms form when free-floating (planktonic) bacteria adhere to and colonize a surface. Following colonization, bacteria secrete exopolysaccharides and/or other biopolymers that form an extracellular matrix and encases a biofilm. Biofilms have been shown to promote the formation of complex microbial communities that are highly resistant to antibiotics. Thus, biofilms are extremely difficult to eradicate and are of interest to both translational and basic science research.

Microbiome of Wound Biofilms (translational project)

Diabetic foot ulcers (DFUs) lead to nearly 100,000 lower limb amputations annually in the US. One quarter of diabetic patients will develop DFUs in their lifetime and, despite standard care, one of three DFUs fails to heal. Infection is one of the most common reasons for diabetes-related hospitalizations and amputations. In these infections, DFUs are colonized by complex microbial communities (microbiota). DFUs are routinely analyzed by standard microbiology techniques. However, these techniques present barriers to accurate microbiota identification because many of the chronic wound bacteria are recalcitrant to growth in a culture and are therefore difficult to identify in this manner. To overcome these limitations we use high-throughput sequencing to study DFU microbiome. Our microbiome profiling data revealed complex bacterial communities containing four major phyla Firmicutes, Actinobacteria, Proteobacteria, and Bacteroidetes.

The goal of this study is to understand how specific microbiome compositions might contribute to inhibition of DFU healing.

Regulation of Streptococcus mutans Carbohydrate Transporters in Biofilms (basic science project)

Carbohydrate transport and metabolism by Streptococcus mutans is directly related to the onset and development of the biofilm commonly called dental plaque, leading to the formation of human dental caries (tooth decay). In S. mutans, carbohydrate substrates are taken up mostly by phosphoenolpyruvate (PEP)-sugar phosphotransferase systems (PTSs). To better understand sugar transport and metabolism of this important dental pathogen, we have performed global transcriptional analyses of S. mutans strain UA159 using expression microarrays. Detailed transcriptional analyses showed the presence of five constitutively transcribed and eleven inducible sugar transporters. We have also defined the carbohydrate-specificity for most of these transporters. The goal of this project is to obtain knowledge regarding the regulation of carbohydrate transport in S. mutans. Since the uptake and metabolism of carbohydrates are the key steps in the formation and release of cariogenic acid, this project will provide highly relevant information for understanding, and perhaps interfering with, the cariogenicity of S. mutans.

Funded Research

Grant #: R01 NIH/NIDCR
Title: “Regulation of Streptococcus mutans PTS Transporters”
Role: PI

Grant #: SAC 2014-11R2, University of Miami
Title: “Temporal Characterization of the Microbiome in Diabetic Foot Ulcers”
Role: PI