Singularities of Pyogenic Streptococcal Biofilms - From Formation to Health Implication

Abstract

Biofilms are generally defined as communities of cells involved in a self-produced extracellular matrix adhered to a surface. In biofilms, the bacteria are less sensitive to host defense mechanisms and antimicrobial agents, due to multiple strategies, that involve modulation of gene expression, controlled metabolic rate, intercellular communication, composition, and 3D architecture of the extracellular matrix. These factors play a key role in streptococci pathogenesis, contributing to therapy failure and promoting persistent infections. The species of the pyogenic group together with Streptococcus pneumoniae are the major pathogens belonging the genus Streptococcus, and its biofilm growth has been investigated, but insights in the genetic origin of biofilm formation are limited. This review summarizes pyogenic streptococci biofilms with details on constitution, formation, and virulence factors associated with formation.

Keywords: antibiotic resistance; biofilm; quorum-sensing; streptococcal; virulence factors.

FIGURE 1

The three stages of biofilm formation and main events involved: (i) initiation, when bacteria attach to the surface; (ii) maturation, when microcolonies are formed, adhered to the surface and embedded by the EPS matrix; and (iii) dispersion, when some members of the community are released from the biofilm entering the planktonic phenotype. Maintenance of the biofilm ensures the community survival (Vasudevan, 2014).

FIGURE 2

General structure of lipoteichoic acids (LTAs) showing the membrane anchoring moiety (A) and the most common repeating unit (B). LTAs repeating unit is more conserved than WTAs; Opposite to WTAs, LTAs are not bound to peptidoglycan but anchored to the membrane via the fatty acid.

FIGURE 3

Schematic representation of the extracellular polymeric substances (EPS) matrix, showing the biofilm water channels, surfactants, the short and long sugar chains, the different proteins/enzymes and extracellular DNA (eDNA). This intricate 3D net of biomolecules is responsible for the chemical/physical and mechanical characteristics of the biofilm, allowing cell–cell communication, nutrients/gas diffusion and antimicrobial tolerance.