One major contributor to the resilience of pathogenic bacteria is their ability to undergo communal responses to form biofilm, a protective extracellular polymeric matrix that enhances resistance to antibiotics. P. aeruginosa, a common nosocomial pathogen, is a known biofilm producer. As such, it is important to identify antibiofilm agents. Of note, neem leaf extracts have been shown to inhibit biofilm formation. The purpose of my project was to identify the effect of neem extracts (bark, fresh leaf, dried leaf) on formed biofilm of P. aeruginosa (ATCC 27853, 10145, BAA-1744) using a microplate biofilm quantitative assay. Bacteria were first inoculated into tryptic soy broth (TSB) and incubated overnight. Afterwards, bacteria were density standardized, transferred to 24-well microplates, and incubated overnight to form biofilm. To isolate and treat the formed biofilm, microplates were washed, TSB was replaced, neem extracts were added (to a final concentration of 10%), and plates were incubated for 5 days. Afterwards, biofilm associated bacteria were killed with glutaraldehyde and microplates were washed again. Subsequently, crystal violet was added to stain the biofilm and excess dye was removed by washing. Stained biofilm was solubilized and quantitated by A590 readings. Average A590 of P. aeruginosa was 0.691 in TSB alone, 0.514 in fresh neem extract, 0.639 in dried neem extract, and 1.016 in neem bark extract. Statistical analysis (p=0.3003, Friedman Test) indicated that all the neem extracts had no significant (p<0.05) effect on formed biofilm of P. aeruginosa. Financial support was received from the DeNardo Education and Research Foundation.

Vishnu Kaverimanian would like to thank their faculty sponsor Rita Heuertz for their support of this project.