College of Liberal Arts & Social Sciences Theses and Dissertations

Graduation Date


Document Type


Department/Program Conferring Degree

Biological Sciences


Stenotrophomomas maltophilia, Biofilm, Antimicrobial resistance, Bacterial biofilms, Pseudomonas aeruginosa


Stenotrophomonas maltophilia is an emerging worldwide, opportunistic respiratory pathogen that is associated with a significant case-fatality ratio in immunocompromised patient populations and has the ability to cause serious infection in cystic fibrosis patients. Populations of S. maltophilia are able to produce biofilms, which complicates these infections and provides resistance to antimicrobials. Factors such as ferric chloride (FeCl3), and sodium chloride (NaCl) have been shown to inhibit the biofilm development of another respiratory pathogen, Pseudomonas aeruginosa, without affecting culture growth. The effect of FeCl3 and NaCl on P. aeruginosa biofilm formation has been well studied and characterized, but little is known about the effect of FeCl3 and NaCl on the biofilm development of S. maltophilia. This study tested three different hypotheses. Based on the fact that S. maltophilia is in environmental organism which exists in various temperatures and requires iron, the first hypothesis was that temperature and ferric chloride would affect S. maltophilia growth. The second hypothesis was that ferric chloride has an effect on the biofilm development of S. maltophilia in the same way it affects P. aeruginosa biofilm development. The third hypothesis was that sodium chloride inhibits biofilm development of S. maltophilia. In the culture conditions used in this study, the growth and biofilm formation of S. maltophilia was not inhibited in the presence of FeCl3 at final concentrations of 1 μM, 5 μM, and 100 μM or with NaCl, but was inhibited in the presence of concentrations ≥ 2% NaCl. In this current study, in contrast to S. maltophilia, a strain of P. aeruginosa demonstrated a decrease in growth when exposed to FeCl3 at 100 µM. However, the effects of NaCl on S. maltophilia mirrored that of P. aeruginosa. Our data shows that FeCl3 at the concentrations tested in the culture medium used on this study was not an effective inhibitor of the biofilm of S. maltophilia.