UVM Theses and Dissertations
Format:
Print
Author:
Cramer, Todd James
Dept./Program:
Microbiology and Molecular Genetics
Year:
2013
Degree:
MS
Abstract:
The aerobic yeast Candida albicans is a commensal microorganism that lives on the skin and in the gastrointestinal tract and mucosal membranes ofthe majority of humans. C. albicans can act as an opportunistic pathogen and cause a variety of diseases including localized oral and esophageal thrush, vulvovaginitis, urinary tract infections, meningitis and systemic candidemia. C. albicans is responsible for 80% of all fungal infections and causes the fourth most common nosocomial infection. These diseases often manifest in immunocompromised individuals, such as AIDS or organ transplant patients, or those receiving intravenous or other invasive medical treatments. Systemic C. albicans infections have an approximately 40% mortality rate.
The pathogenicity of C. albicans is largely attributed to its pleomorphic nature. Under a variety of environmental and physiological conditions, including those associated with human physiology such as a temperature of 37 DC, a morphological shift is initiated. Round, budded cells switch to elongated hyphal or pseudohyphal cells during a metamorphosis known as the budded-to-hyphal transition (BHT). Hyphal cells more readily aggregate with each other and aid C. albicans in forming robust 3-dimensional structures called biofilms on biotic or abiotic surfaces. Biofilms are difficult to control as they can be over 1,000 times more resistant to antifungals than planktonic cells. C. albicans biofilms create a reservoir of cells that aid in virulence. Treatment of C. albicans biofilms is further complicated by the use of antifungals or broad spectrum antimicrobials that can have adverse side effects in the host, such as liver damage or allergic reactions, and·the wide range of minimum inhibitory concentrations or applications needed to be effective depending upon the infecting strain.
An alternative approach to controlling C. albicans infections and biofilm formation is to utilize small molecules that inhibit the BHT but do not kill cells. This would greatly reduce or eliminate the possibility of resistance arising in the cells as they would still be able to live as commensals but would remain avirulent. Three small molecules tested in our lab, 5, 8, 11, 14-eicosatetraynoic acid (ETYA), CGP-37157 and clozapine were able to block the BHT and prevent biofilm formation of C. albicans in various media and conditions tested. When medical equipment such as silicone contact lenses or intravenous polyurethane catheters were inoculated with C. albicans concomitantly with inhibitory concentrations of small molecule BHT inhibitors, C. albicans biofilms did not form. Researchers have been successful in soaking similar materials with antimicrobials such as chlorhexidine acetate and silver sulfadiazine, rendering them incapable of supporting a range of microbial growth, including C. albicans.
The studies herein indicate that soaking similar materials with small molecule BHT inhibitors leads to a lack of subsequent C. albicans biofilm formation. Several conditions were examined including amount of time spent soaking, temperature, concentration of small molecule and vehicle control. Co-administering a-tocopherol (vitamin E) alongside small molecule BHT inhibitors enhances their ability to prevent C. albicans biofilm formation on silicone substrates and reduces the concentration of small molecule needed to be effective. These data suggest the possibility that new and innovative approaches to controlling C. albicans infections are possible.
The pathogenicity of C. albicans is largely attributed to its pleomorphic nature. Under a variety of environmental and physiological conditions, including those associated with human physiology such as a temperature of 37 DC, a morphological shift is initiated. Round, budded cells switch to elongated hyphal or pseudohyphal cells during a metamorphosis known as the budded-to-hyphal transition (BHT). Hyphal cells more readily aggregate with each other and aid C. albicans in forming robust 3-dimensional structures called biofilms on biotic or abiotic surfaces. Biofilms are difficult to control as they can be over 1,000 times more resistant to antifungals than planktonic cells. C. albicans biofilms create a reservoir of cells that aid in virulence. Treatment of C. albicans biofilms is further complicated by the use of antifungals or broad spectrum antimicrobials that can have adverse side effects in the host, such as liver damage or allergic reactions, and·the wide range of minimum inhibitory concentrations or applications needed to be effective depending upon the infecting strain.
An alternative approach to controlling C. albicans infections and biofilm formation is to utilize small molecules that inhibit the BHT but do not kill cells. This would greatly reduce or eliminate the possibility of resistance arising in the cells as they would still be able to live as commensals but would remain avirulent. Three small molecules tested in our lab, 5, 8, 11, 14-eicosatetraynoic acid (ETYA), CGP-37157 and clozapine were able to block the BHT and prevent biofilm formation of C. albicans in various media and conditions tested. When medical equipment such as silicone contact lenses or intravenous polyurethane catheters were inoculated with C. albicans concomitantly with inhibitory concentrations of small molecule BHT inhibitors, C. albicans biofilms did not form. Researchers have been successful in soaking similar materials with antimicrobials such as chlorhexidine acetate and silver sulfadiazine, rendering them incapable of supporting a range of microbial growth, including C. albicans.
The studies herein indicate that soaking similar materials with small molecule BHT inhibitors leads to a lack of subsequent C. albicans biofilm formation. Several conditions were examined including amount of time spent soaking, temperature, concentration of small molecule and vehicle control. Co-administering a-tocopherol (vitamin E) alongside small molecule BHT inhibitors enhances their ability to prevent C. albicans biofilm formation on silicone substrates and reduces the concentration of small molecule needed to be effective. These data suggest the possibility that new and innovative approaches to controlling C. albicans infections are possible.