Growth rate and biofilm thickness of Streptococcus sobrinus and Streptococcus mutans on hydroxapatite^Note

Abstract

Bacteria in biofilm and planktonic bacteria exhibit different properties. The objective of the present study was to compare the growth rates of Streptococcus sobrinus and Streptococcus mutans on different types of biofilm with their planktonic growth rate. Our experimental model consisted of hydroxyapatite beads coated with human saliva (sHA). Glucans or fructans were synthesized in situ on sHA by immobilized cell-free glucosyltransferase or fructosyltransferase isolated from oral bacteria. S. sobrinus or S. mutans was then adsorbed onto the glucan- or fructan-coated sHA and incubated for different time intervals. The depth of the developing biofilm was measured. Our results show that growth rates of S. sobrinus and S. mutans on both fructan- and glucan-coated sHA were similar during a 23 h period. In addition, the profile was similar to the growth profile of the same planktonic bacteria. The resemblance in growth rates between planktonic and biofilm bacteria may be attributed to the thin and non-dense biofilm formed in the initial stages of the biofilm formation. The thin biofilm coat, reaching a maximal depth of 11 microm, has only imposed limited diffusion restrictions, thus not affecting the growth of the bacteria in the biofilm. Our study shows that growth of bacteria on surfaces may resemble their growth in suspension if the bacteria are not embedded in a thick dense biofilm.

Biofilm Formation by Group A Streptococci: Is There a Relationship with Treatment Failure?

“…The efficiency of GAS biofilm formation after 24 h, measured in log CFU, was normally distributed with a range of 10 (22,30,32). However, no other studies have looked at a variety of isolates of the same species.…”

“…This finding indicated that there was a spectrum of capacities for GAS isolates to initiate or expand the biofilm. Factors that contribute to the initiation and expansion of biofilms are numerous; some examples include the capability to adhere to the substratum (12), quorum sensing (19), growth rate (32), and establishing a biofilm structure (30,35). Using the total number of cells in the biofilm to measure efficiency was insufficient to establish the factor(s) that would assist in explaining the variation observed in the efficiency of GAS biofilm formation.…”

“…These attributes include, but are not limited to, a lower growth rate (30,32), an exopolysaccharide matrix (12,18), a change in gene expression (3,11,26), an optimal three-dimensional structure (1,8,35), and the production of potentially resistant genes (2). GAS may form a biofilm, but it requires one or more of these attributes to be present within the biofilm in order to facilitate antibiotic insensitivity.…”

Cranberry high molecular weight constituents promote Streptococcus sobrinus desorption from artificial biofilm

“…In brief, 40 mg of HA beads (80 m in diameter) (BioRad Laboratories, Hercules, CA) were equilibrated with phosphate-buffered-saline (PBS) and incubated for 1 h at 37 • C with clarified whole saliva. After three washes with PBS, the saliva-coated HA (sHA) were incubated for 1 h at 37 • C with cell-free GTF or FTF, prepared as described by Rozen et al [14]. The saliva and enzyme-coated HA beads were washed three times with PBS and further incubated at 37 • C with radioactively labelled S. sobrinus ( 3 H radiolabelled bacteria were prepared by supplementing the bacterial growth medium with 5 mci/ml of 3 H-thymidine.…”

Evaluation of bacteria-induced enamel demineralization using optical profilometry

“…Previous results demonstrated that S. mutans is able to form a biofilm on hydroxyapatite in vitro (28). Hydroxyapatite is composed of a complex calcium phosphate mineral and is a principal component found in tooth enamel.…”