Research

Drs. Ken Bayles, Paul Fey, and Tammy Kielian are leading this multi-investigator program project grant from the National Institutes of Health (NIH) that seeks to provide a broader understanding of the mechanisms of Staphylococcus aureus (S. aureus) biofilm development and dispersal, and how these processes interface with the host immune response.

Dr. Tammy Kielian’s research interests span the fields of immunology, infectious diseases, and neuroscience with a unifying theme of innate immunity. Her laboratory has a long-standing interest in studying the pathogenesis and immune responses elicited by S. aureus biofilm using mouse models of prosthetic joint and craniotomy infection. Her laboratory also collaborates with orthopaedic surgeons and neurosurgeons at UNMC to explore immune responses in patients with prosthetic joint and craniotomy infections with the goal of identifying novel immune biomarkers for infection diagnosis and therapy. Ongoing studies are to identify the mechanisms responsible for skewing the host innate immune response to an anti-inflammatory state following S. aureus biofilm infection and how this may be targeted to facilitate bacterial clearance. Additional areas of interest include immunometabolism and how S. aureus biofilm-leukocyte metabolic crosstalk influences the epigenetic landscape of leukocytes to promote their anti-inflammatory attributes.

Dr. Marat R. Sadykov's research is focused on understanding the physiological and metabolic processes governing fitness, virulence, and versatility of Gram-positive bacterial pathogens. Specifically, he is interested in i) regulation of staphylococcal carbohydrate metabolism in response to various environmental cues and its contribution to fitness, virulence determinant production, and pathogenesis during infections; and ii) metabolic and physiological basis of staphylococcal biofilm formation and its roles in pathogenesis of biomaterial-related and nosocomial infections. Dr. Sadykov's research interests also encompass contribution of the overflow and central carbohydrate metabolic pathways to fitness and sporulation of Bacillus anthracis.

Dr. Dong Wang's laboratory research focuses on development of nanomedicine/drug delivery systems for musculoskeletal diseases. S. aureus is a major cause of bacterial infection often associated with orthopedic and infection often associated with orthopedic and other medical devices and implants. The treatment can be difficult, partially due to the lack of methodologies that would maintain proper antimicrobial concentration at the implantation site. To address this problem, our laboratory has developed a biomineral-binding liposomal delivery platform, which will allow retention and sustained release of antimicrobials at the implant surface for the prevention of S. aureus colonization. The biomineral binding capacity of the liposome is achieved by conjugating a biomineral binding moiety to the liposome surface using “click-chemistry”. Our data show that this novel liposome could swiftly (within 5 minutes) bind to hydroxyapatite (HA, or main component of the bone) particles. In vitro S. aureus culture experiments have revealed that the biomineral binding liposome loaded with oxacillin provides significantly better prevention of S. aureus biofilm formation on HA discs compared to non-binding liposomes loaded with oxacillin, empty biomineral-binding liposomes, saline, and untreated controls, which may be explained by the retention and the sustained oxacillin release. A series of other biomineral binding drug delivery platforms such as biomineral binding micelles are also being developed for the formulation of other antimicrobials.

Dr. Gus Wang's research focuses on the identification, characterization, and engineering of novel antimicrobial agents based on structural, bioinformatics, and functional studies. The ultimate goal is to develop novel compounds that curb pathogenic microbes, especially difficult-to-kill microbes such as methicillin-resistant Staphylococcus aureus (MRSA).

Naturally occurring antimicrobial peptides (AMPs) are universal effector molecules that directly eliminate invading pathogenic bacteria, fungi, viruses, and parasites. In mammals, including humans, such peptides may also modulate the adaptive immune systems. To date, more than 1,600 AMPs have been identified in bacteria, fungi, plants, and animals. To better manage this information, Dr. Wang's laboratory has established the Antimicrobial Peptide database (APD) as a tool for AMP naming, classification, search, statistical analysis, prediction, and design. Their database is also a useful resource for developing novel antimicrobial agents. These miniature proteins are capable of adopting a variety of three-dimensional structures, inspiring the design of natural mimics that benefit mankind. The objective of one of their NIH-funded projects is to develop AMPs into novel anti-HIV microbicides in collaboration with ImQuest BioSciences.

His lab is particularly interested in an in-depth understanding of the functional roles of human AMPs and their relationships with human diseases, including cancer. Recently, they have solved high-quality structures of human cathelicidin LL-37 and its important fragments by multidimensional nuclear magnetic resonance (NMR) spectroscopy. Dioctanoyl phosphatidylglycerol (D8PG) has been established as a new and unique membrane-mimetic model, which enables the detection of Phe-PG and Arg-PG interactions. Based on three-dimensional structures, they have identified the most potent region within LL-37 against MRSA, thereby identifying a useful template for designing novel therapeutic compounds against this superbug (US Patent 7,465,784). To elucidate the mechanism of action, they are utilizing a variety of biophysical and biochemical techniques. Their studies will lay the foundation for peptide engineering with a goal to overcome the hurdles (stability, toxicity, and production) on the way to the development of natural AMPs into novel therapeutics.

Another research direction of high interest to Dr. Wang is to engineer molecules that control protein-mediated signal transduction pathways essential for bacterial survival or infection in collaboration with colleagues in the Center for Staphylococcal Research (CSR). The lead compound will be optimized by combining NMR-based library screening with rational design based on three-dimensional structures of protein-protein complexes.

Dr. Vinai C. Thomas' laboratory studies staphylococcal adaptations in response to weak acid stress. Staphylococci commonly encounter biological weak acids like lactate and acetate when residing on the human skin. While lactate is present in human sweat gland secretions, acetate is produced as a byproduct of staphylococcal glucose metabolism. Both lactate and acetate can inhibit growth and adversely affect staphylococcal survival under conditions of low pH, normally associated with human sweat. Dr. Thomas's lab is interested in determining metabolic and physiological adaptations that enhance staphylococcal resistance to weak acid stress. Current projects focus on the role and regulation of glucose and arginine catabolism in response to weak acid stress. They are also investigating how weak acids modulate biofilm development by this organism. Biofilms are surface-attached bacterial communities that are encased in a matrix composed of proteins, DNA, and carbohydrates. During biofilm development, a subpopulation of staphylococci undergo a "suicidal" form of cell death and contribute to the buildup of the biofilm matrix, thus hastening the biofilm maturation process. Although they have recently demonstrated a role for acetate in potentiating cell death in staphylococcal populations, the mechanisms involved are not clear and therefore represent an active area of research in the lab. Their studies will not only help identify alternate targets for therapeutic intervention but also enhance an understanding on how staphylococci survive the harsh acidic environment of the skin.

Dr. Kevin Garvin is an orthopedic surgeon specializing in hip and knee reconstruction. His research interest focuses on the pathogenesis, prevention, and treatment of musculoskeletal infections caused by emerging multi-resistant strains of bacteria in the surgical setting. As chair of the Department of Orthopedic Surgery and Rehabilitation at UNMC, Dr. Garvin leads a dynamic team of clinicians and researchers who have earned a strong regional, national, and international reputation for excellence in patient care, orthopedic education, and expanding cutting-edge research. He is committed to collaborative research and through the CSR several projects are underway.

Dr. Mark Rupp is a professor of infectious diseases at UNMC and is also the medical director of the Nebraska Medical Center's Department of Health Care Epidemiology. His research focuses on the clinical epidemiology of Staphylococcus. He often works directly with graduate students by serving on their graduate committees, thereby helping the students understand the translation between research and clinical practice. Dr. Rupp, in collaboration with other members of the CSR, is trying to understand the mechanism of resistance and how the bacteria spread in order to better exploit the organism and develop improved antibiotics. In addition, he and other health care professionals are working hard to use antibiotics more prudently to preserve their value. Antibiotic resistance is considered to be one of the most urgent priorities in public health. Infectious disease specialists such as Dr. Rupp understand that antibiotic resistance by bacteria such as staph has led to increasing severity of disease, and possible death, as well as rising health care costs. Many infectious disease experts believe that the spread of staph is a public health crisis and that new solutions must be found soon. This is why Dr. Rupp feels collaborations between researchers and physicians, like those currently in place at the CSR, are essential.