Effects of Glucose and Temperature on Exopolysaccharides, Extracellular Matrix Proteins Production and Biofilm Formation of Carbapenem- Resistant Acinetobacter baumannii

Acinetobacter baumannii is one of the most nosocomial pathogens as it can form biofilm on hospital surfaces. The objective of this work was to analyze the production of exopolysaccharides, extracellular proteins, and biofilm formation of carbapenem-resistant A. baumannii on silicone and ceramic surfaces.

Qualitative and quantitative tests were conducted to evaluate the production of exopolysaccharides in different culture conditions. The Biuret method was applied for protein determination. Furthermore, the count of viable cultivable cells was used to study biofilm formation. For physicochemical characterization, the surfaces were subjected to contact angle measurements.

Incubation at 37°C with glucose (1.5%) was the optimal condition for producing exopolysaccharides. Glucose supplementation has also impacted the protein production by A. baumannii. Moreover, proteins were abundant in the extracellular matrix compared to exopolysaccharides (0.46 mg/mL for exopolysaccharides and 2.48 mg/mL for proteins). The strains formed biofilms on both surfaces but with different capacities, possibly due to the hydrophilic nature of ceramic and the hydrophobic nature of silicone. The addition of 1.5% glucose enhanced biofilm formation on ceramic for all strains. A positive correlation was established between the EPS concentration and the number of cells forming biofilm on silicone with 0.2% of glucose and between protein production and biofilm formed on ceramic with 0.2% and 1.5% of glucose. On the contrary, a negative correlation was detected between protein production and biofilm formation on the silicone surface with 0.2% glucose concentration.

  The environmental conditions significantly affect A. baumannii biofilm and its extracellular matrix compounds.