Biofilm formation correlates with bacterial binding to enterocytes in Enterococcus faecalis.

Patrick Delaplain; Alec Borsook; Jin Wang; Anatoly Grishin; Henri Ford

Although necrotizing enterocolitis (NEC) is believed to be associated with bacterial colonization, the exact nature of the relationship between NEC and bacterial populations remains elusive. Our previous studies implicated a clinically relevant strain of Cronobacter muytjensii, but not several other strains of this species, as a causative agent of NEC. This led us to hypothesize that certain strain characteristics may account for the difference between pathogenic and potentially protective bacteria. We are characterizing multiple isolates of Enterococcus faecalis, a common first colonizer of rat intestine, and their role in the pathogenesis of experimental NEC.

Ability to form a biofilm has been shown to enhance bacterial virulence or pathogenicity, although the underlying mechanism is still undefined. We hypothesize that biofilm formation may enhance bacterial binding to the intestinal epithelium.

Bacteria were isolated from 4-day-old rats and characterized. Isolates with different combinations of characteristics were considered different strains. The identified strains were examined for their ability to bind to IEC-6 enterocytes and to form biofilm on polystyrene microtiter 96-well plates using a quantitative crystal violet assay.

21 strains were identified among the 146 isolates. There was considerable diversity in the ability of the E. faecalis strains to bind IEC-6 enterocytes. When biofilm production was compared between the high-binding group (>2% bacteria bound) and the low-binding group (<0.8% bacteria bound), the latter had significantly lower biofilm formation (0.012± vs. 0.008±, p = 0.014).

Ability of E. faecalis to effectively bind intestinal epithelial cells positively correlates with another potentially pathogenic characteristic—ability to form biofilm. Further characterization of these bacteria may identify potentially pathogenic or protective strains.