Date of Award

Winter 12-22-2021

Degree Type


Degree Name

Master of Science (MS)


Biomedical and Chemical Engineering


Ren, Dacheng

Second Advisor

Movileanu, Liviu


Antimicrobial susceptibility, Artificial Sputum Medium, cystic fibrosis, P. aeruginosa

Subject Categories

Biomedical Engineering and Bioengineering | Engineering


Long-term infection caused by P. aeruginosa poses a major threat to personal and public health, and causes billions of dollars in medical expenses. To develop more effective controls, it is important to accurately evaluate antibiotic susceptibility of clinical isolates and understand how susceptibility changes during the course of infection. Conventional drug susceptibility tests using nutrient-rich media have been questioned regarding their relevance due to the difference between the model in vivo test conditions and the environment in the patients. Here, we report that 27 clinical strains of P. aeruginosa isolated from cystic fibrosis patients showed higher drug resistance in Artificial Sputum Medium (ASM) than in the lab medium Lysogeny broth (LB) (up to 32 times). In addition, the MIC of the clinical isolates from a patient shows different changes in antibiotic susceptibility between LB and ASM. Specifically, when tested in LB, the ciprofloxacin MIC of clinical strains from patient No. 5 gradually increased over the time of isolation. However, the MIC of late isolates decreased in LB. In comparison, MIC continued to increase in ASM. This is important to note because the ASM better represents the clinical condition of cystic fibrosis(CF) patient. To better understand how P. aeruginosa adapts to the host airway environment, we sequenced the genomes of P. aeruginosa strains chronically isolated from CF patients at Seattle Children Hospital and compared with the wild-type PAO1. Several mutations were identified in genes related to flagella, biofilm, intercellular communication, and antibiotic targets. In summary, the findings from this study provide new insights into the development of antibiotic resistance in P. aeruginosa and and the importance to use appropriate in vitro testing methods, which will help future research to control P. aeruginosa infections.


Open Access



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