ABSTRACT
Biofilms are communities of clustered cells that develop on various surfaces in in vivo or in vitro conditions. The formation of biofilm plays a significant role in most human pathogens, as it intensifies the virulence factors challenging the host's immune responses and therapy. Most facultative and opportunistic pathogens are highly persistent as biofilm outside the host. Bacteria in the biofilm are differentiated due to the influence of cell-signaling mechanisms that include several factors such as c-di-GMP, regulatory small RNAs (sRNAs), and quorum signaling regulators. Biofilm-forming bacteria are embedded in the matrix of exopolysaccharide (EPS) and other complex materials produced by the bacteria that enable anchorage. EPS is a hydrated anionic exopolymer that encompasses certain trapped entities of proteins, nucleic acids, lipids, organic molecules, and teichoic acids. The biofilm biomass is made of 90% EPS, which also functions as a physiological and mechanical barrier to most antagonistic substances. Microniches found within the matrices show gradient variation and optimized metabolism. Many outbreaks of facultative human pathogens result in the formation of biofilms, which are also a reservoir of future infections.
Several gram-positive and gram-negative bacteria have been identified to form biofilms, however, clinical setups most often use Pseudomonas aeruginosa, Staphylococcus aureus, and Staphylococcus epidermidis. Various other pathogenic bacteria, including Haemophilus influenzae that causes otitis media and Fusobacterium nucleatum that causes periodontitis, are found to be highly resistant to antimicrobials as well as innate and adaptive immune responses. Formation of biofilm in medical devices is mostly seen among pathogenic bacteria like Enterococcus faecalis, Lactobacillus spp., Staphylococcus haemolyticus, and Prevotella spp.
