SEM Analysis of Surface Impact on Biofilm Antibiotic Treatment

The aim of this work was to use scanning electron microscopy (SEM) to investigate the effect of ampicillin treatment onEscherichiacolibiofilms formed on two surface materials with different properties, silicone (SIL) and glass (GLA). Epifluorescence microscopy(EM) was initially used to assess biofilm formation and killing efficiency on both surfaces. This technique showed that higherbacterial colonization was obtained in the hydrophobic SIL than in the hydrophilic GLA. It has also shown that higher biofilminactivation was attained for GLA after the antibiotic treatment (7-log reduction versus 1-log reduction for SIL). Due to its highresolution and magnification, SEM enabled a more detailed analysis of the antibiotic effect on biofilm cells, complementing thekilling efficiency information obtained by EM. SEM micrographs revealed that ampicillin-treated cells have an elongated formwhen compared to untreated cells. Additionally, it has shown that different materials induced different levels of elongation oncells exposed to antibiotic. Biofilms formed on GLA showed a 37% higher elongation than those formed on SIL. Importantly, cellelongation was related to viability since ampicillin had a higher bactericidal effect on GLA-formed biofilms. These findings raisethe possibility of using SEM for understanding the efficacy of antimicrobial treatments by observation of biofilm morphology.