Title : Correlation analysis between biofilm formation and virulence of Enterococcus faecium and E. faecalis isolated from gastrointestinal tract of humans and animals.
Enterococcus are pathogens that can cause nosocomial infections. Their ability to form biofilm influences the growth of virulence and also contributes to increase of antimicrobial resistance. Certain virulence factors may play an important role in biofilm formation. The aim of the study was analysis of relationship between the ability of E. faecium and E. faecalis to produce biofilm and presence of virulence factors.
The research was carried out on 153 E. faecium and 125 E. faecalis isolated from the digestive tract of humans and various group of animals. The evaluation of the biofilm formation capacity was performed by the crystal violet assay. The virulence analysis of the strains was performed based on the detection of 22 genes: esp, cylA, cylB, cylM, agg, gelE, cpd, ccf, cob, efaAfs, afaAfm, ebpA, ebpB, ebpC, pil, srt, ace, sprE, fsrA, fsrB, fsrC, hyl and gelatinase activity.
In this study, 7% of E. faecium and 59% of E. faecalis were able to produce biofilm. The most frequently detected virulence genes among E. faecium were efaAfm (95%), ebpB (92%), ccf (90%), srt (84%) and pil (74%). There were no cylA, cylM, fsrA, fsrB, fsrC genes detected in any of E. faecium, as well as gelatinase activity. E. faecium that do not produce biofilm had a higher percentage of detection of ebpB gene compare to biofilm positive E. faecium (statistically significant differences, p<0.05).
E. faecalis showed a high percentage of efaAfc (98%), ebpA (97%), ebpB (96%), ebpC (97%), srt (97%) and pil (96%) detection. Moreover, 19% of E. faecalis had gelatinase activity. Statistical analysis showed on the one hand a higher percentage of sprE, fsrA, fsrB, fsrC and gelE genes and gelatinase activity among E. faecalis not producing biofilm compare to biofilm positive strains, on the other, biofilm positive E. faecalis were characterized by frequent presence of esp, agg cylA, cylB and cylM genes compare to biofilm negative E. faecalis.
To sum up, E. faecalis compare to E. faecium have higher ability to form biofilm, as well as a higher variety of virulence factors. The high percentage of detection of esp, agg, and cyl genes among biofilm producing E. faecalis may indicate the important role of these factors in biofilm formation. On the other hand, the more frequent presence of some virulence factors among the non-biofilm producing strains indicates that biofilm formation is a more complex phenomenon.
Presented research will help to understand the mechanisms of biofilm formation created by microbes of key importance for public health
Research sheds new light on Enterococcus virulence factors previously considered as markers of biofilm formation as a complex phenomenon.
Understanding the phenomenon of biofilm formation by Enterococcus play an important role in areas such as human and veterinary surgery, as well as treatment due to contribution of spread of antibiotic resistance (e.g., via medical devices)