In vitro estimation of the infectious potential of the enterococcal strain by an analysis of monocytes’ response to the formed biofilm

The aim of our study was to assess the possibility of predicting Enterococcus faecalis pathogenicity based on morphological changes of monocytes interacting with of bacteria and their adherence to biofilm. Changes in the size and granularity of monocytes, as well as their adherence to biofilm were assessed using FACScan flow cytometer after 1h co-incubation of monocytes and enterococcal biofilm in 37°C. The obtained results were validated with respect to monocytes incubated without bacteria. The most prominent changes in size of monocytes were observed in the case of commensal bacteria. The interaction with bacteria isolated from the blood stream and urine caused comparable changes in the size of THP-1 cells and were smaller than the changes of cells incubated with commensal bacteria. Changes in THP-1 granularity were comparable regardless of the source of bacteria forming biofilm. The parameter which differed the most was connected to the adherence index relating to the monocytes remaining on the surface of biofilm after 1h of incubation. Taking into consideration the obtained results, we conclude that changes in the morphology of monocytes can be treated as a tool assessing the potential pathogenicity of the bacteria. What is more, the adhesive properties towards bacterial biofilm alone might be considered as a tool allowing for the assessment of the pathogenicity of the isolated strain bypassing time-consuming techniques.