Kinetics of Biofilm Formation by Staphylococcus aureus and Pseudomonas aeruginosa

Abstract

Biofilms are structured communities attached to surfaces that have been implicated in increasing antimicrobic resistance and infections that are chronic or medical device‐associated. This study focused on quantitative assessment of biofilm formation by S. aureus (either MRSA, methicillin‐resistant or MSSA, methicillin susceptible) and P. aeruginosa in a kinetic manner. Bacteria assessed were ATCC strains and clinical isolates from an area hospital laboratory and incubation conditions were static or shaking (250 rpm) during incubation (2‐48 hours). A microplate assay allowed for quantitative spectrophotometric (A590) evaluation of crystal violet‐stained biofilm adherent to microwells at indicated time points. Results indicated that clinical isolates of MRSA and MSSA produced different amounts of biofilm (with MRSA producing twice as much as MSSA) but had similar timing of biofilm peaks and declines. Clinical isolates of P. aeruginosa produced less biofilm than MRSA but as much as MSSA. Interestingly, results suggested that half of the P. aeruginosa were delayed biofilm producers indicating kinetic diversity that differed from a striking similarity among the S. aureus, especially clinical MRSA isolates. Results suggested that ATCC strains closely approximated results of clinical isolates from hospitalized patients thereby justifying use of ATCC strains for future studies. Finally, results indicated that there was no difference between shaking and static incubation conditions for biofilm formation. Future studies will focus on reversible versus irreversible bacterial adherence to better define steps of biofilm formationFinancial support for TDZ was received from the DeNardo Education and Research Foundation.