Date of Degree

12-2016

Document Type

Thesis

Degree Name

Master of Science (MS)

Program

Biology

Advisor

Ana Vallor

Advisor

Russell Raymond

Advisor

Christopher Pierce

Abstract

Stenotrophomonas maltophilia has emerged as an important opportunistic pathogen in the debilitated host. It possesses the ability to target and colonize respiratory-tract epithelial cells and grow on the surface of medical devices. It is associated with a significant case-fatality ratio in cystic fibrosis patients. S. maltophilia species have the ability to grow in bacterial biofilms, which further complicates these infections by providing the opportunity for acquisition of antibiotic resistant genes. This study investigated the effects on the growth of different strains of the same species of S. maltophilia, ATCC 51331 and 13637, when the selected environmental factors are varied. Factors studied were temperature and salt concentration in the medium, sodium chloride (NaCl) and ferric chloride (FeCl3). Further, minimal inhibitory concentrations (MICs), against a select panel of antibiotics were assessed for both strains when cultured in the different growth conditions proposed. The expectation of this study is that Ferric Chloride concentrations provided the most significant effects on S. maltophilia biofilm growth. Initially Luria Bertani (LB) media (with proper modification to salt content) were used to culture the organisms to visually assess colony growth under these conditions at the following temperatures: 40C, 200C, 370C, 550C and also to conduct MICs. The effects of various experimental conditions were also determined on S. maltophilia biofilms formed in the 96 well plate format. Viability of the biofilms have assessed using a previously published metabolic assay. Our data show that different environmental conditions affect S. maltophilia growth. For instance, when grown in different temperatures the morphology of S. maltophilia X51331 and X13637 varied during 3 days growth period and the S. maltophilia could not grow in the low and high temperatures of 40C and 550C. Furthermore, our data shows the effect of iron and sodium chloride with different concentrations of salt on the growth and metabolic activity of the biofilms of S. maltophilia X51331 and X13637 incubated at 300 C and 370 C, as well as S. maltophilia growth at varying FeCl3 and NaCl concentrations for 24, 48, and 72 hours. There was a significant increase in the average size of S. maltophila X51331 and X13637 colonies when grown in low concentrations of salt 0 μM and 1 μM, and growth was inhibited in the presence of concentrations ≥ 2% NaCl and FeCl3.

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