Antibiotic Resistance in Biofilm

Abstract

Biofilms can be found on several living and nonliving surfaces, which are formed by a group of microorganisms, complex assembly of proteins, polysaccharides, and DNAs in an extracellular polymeric matrix. By forming a biofilm, bacteria protect themselves from host defense, disinfectants, and antibiotics. Bacteria inside biofilm are much more resistant to antimicrobial agents than planktonic forms since bacteria that are unresisting to antimicrobial agents in any way can turn resistant after forming a biofilm. Low penetration of antibiotics into the biofilm, slow reproduction, and the existence of adaptive stress response constitute the multiphased defense of the bacterium. This antibiotic resistance, which is provided by biofilm, makes the treatments, which use effective antibiotic doses on the bacterium in planktonic shape, difficult. Biofilm formation potential of bacteria appears as an important virulence factor in ensuring the colonization on the living tissues or medical devices and makes the treatment difficult. The aim of this chapter is to overview the current knowledge of antimicrobial resistance mechanisms in biofilms.

From Nanobiotechnology, Positively Charged Biomimetic Dendrimers as Novel Antibacterial Agents: A Review

“…The ability of a bacterium to resist the damaging activity of an antimicrobial agent can be inferred by intrinsic mechanisms, based on the innate ability of a bacterial species to elude the activity of a particular drug, through its inherent structural or functional characteristics. More frequently, nevertheless, insusceptibility to a drug (or several drugs) is genetically determined, and can be transmitted across the same pathogen or even to similar bacterial species, by passing the DNA responsible for the mechanism of resistance through several complex mechanisms such as conjugation, transformation and even transduction [ 20 ].…”

“…The biofilm biomass is made of extracellular polymeric substances (EPSs) including a complex assemblage of enzyme proteins, polysaccharides, such as cellulose, polyglucosamine (PGA) and exopolysaccharides, genetic material, as extracellular DNA (eDNA), anionic and cationic glycoproteins and glycolipids, which enable intercellular interactions, keep bacteria in close proximity with each other, serve as a connecting agents, and stabilize the scaffold for the three-dimensional biofilm structure [ 20 , 21 ]. In the matrix, nutrients are trapped for metabolic uses by the resident bacteria and enzymes secreted by the bacteria modify EPS composition in response to changes in nutrient availability, while water is efficiently retained through H-bond interactions with hydrophilic polysaccharides [ 21 ].…”

“…QS mechanisms exist in Gram-positive and Gram-negative bacteria, but the signal molecules used to transmit information in the two groups are different. However, QS allows bacteria to synchronize and act as a unique great workforce that actively exchanges and shares products that play a pivotal role in maintaining biofilm architecture and providing a favorable living environment for the resident bacteria [ 20 , 23 ].…”

“…Bacteria can easily grow undisturbed in biofilms on a wide variety of surfaces and attach to inert or alive surfaces, including tissues, industrial surfaces, and artificial devices, such as catheters, intrauterine contraceptive devices, and prosthetic medical devices, implants, cardiac valves, dental materials, and contact lenses [ 20 , 23 ]. Due to the protective action of biofilm, bacteria that growth in the biofilm conditions (sessile form), are much more resistant to antimicrobial agents than bacteria that growth in normal conditions (planktonic forms) and their susceptibility to antibiotics dramatically decreases.…”

“…Moreover, biofilm-specific characteristics limit the diffusion of drugs, making it difficult to reach the bacteria, and nullify antibiotic activity [ 24 ]. To counteract biofilm-forming microorganisms, an antimicrobial agent must overcome several additional obstacles, such as an increased number of resistant mutants, high cell density, molecular exchanges, substance delivery, efflux pump, persistent and dormant cells, altered bacteria growth rate and different gene expression [ 20 , 25 ]. In this regard, Table 1 reports the mechanisms through which biofilms hamper the activity of antibiotics with examples of microorganisms producing biofilms and the related inactivated antibiotics.…”