Biofilms: Survival Mechanisms of Clinically Relevant Microorganisms

Abstract

Though biofilms were first described by Antonie van Leeuwenhoek, the theory describing the biofilm process was not developed until 1978. We now understand that biofilms are universal, occurring in aquatic and industrial water systems as well as a large number of environments and medical devices relevant for public health. Using tools such as the scanning electron microscope and, more recently, the confocal laser scanning microscope, biofilm researchers now understand that biofilms are not unstructured, homogeneous deposits of cells and accumulated slime, but complex communities of surface-associated cells enclosed in a polymer matrix containing open water channels. Further studies have shown that the biofilm phenotype can be described in terms of the genes expressed by biofilm-associated cells. Microorganisms growing in a biofilm are highly resistant to antimicrobial agents by one or more mechanisms. Biofilm-associated microorganisms have been shown to be associated with several human diseases, such as native valve endocarditis and cystic fibrosis, and to colonize a wide variety of medical devices. Though epidemiologic evidence points to biofilms as a source of several infectious diseases, the exact mechanisms by which biofilm-associated microorganisms elicit disease are poorly understood. Detachment of cells or cell aggregates, production of endotoxin, increased resistance to the host immune system, and provision of a niche for the generation of resistant organisms are all biofilm processes which could initiate the disease process. Effective strategies to prevent or control biofilms on medical devices must take into consideration the unique and tenacious nature of biofilms. Current intervention strategies are designed to prevent initial device colonization, minimize microbial cell attachment to the device, penetrate the biofilm matrix and kill the associated cells, or remove the device from the patient. In the future, treatments may be based on inhibition of genes involved in cell attachment and biofilm formation

Clinical Characteristics of Biofilms in Patients with Chronic Rhinosinusitis: A Prospective Case–Control Study

“…Biofilms are aggregates of microorganisms in which cells adhere to each other on the surface of living or nonliving substrates. The bacteria in biofilms are known to be 1,000 times more resistant to antibiotics than the floating form of bacteria [2]. After forming biofilms, bacteria penetrate host defenses, thus decreasing antibiotic susceptibility, and releases floating bacteria to new sites [3].…”

Acinetobacter baumannii is not Associated with Osteomyelitis in a Rat Model: A Pilot Study

“…Primary and nosocomial infections are not easily prevented or eradicated in the presence of foreign bodies and a poor vascular supply. The presence of graft material and fixation devices provides excellent surfaces for bacterial biofilm formation that are less susceptible to antibiotics and host immune defenses [9,10].…”

Antimicrobial activity of Citrox® bioflavonoid preparations against oral microorganisms

“…Biofilms can be defined as microbial cells attached to a surface and organised into structured communities embedded within a matrix of extracellular material that has been produced by the biofilm cells. 36 Bacterial dental plaque is perhaps the most widely studied biofilm due to its association with caries and periodontal disease and there is increasing interest in the nature of biofilms formed by Candida spp. 37 It is widely recognised that both the biofilm structure and the phenotype of cells within a biofilm can afford protection against both host defence processes and administered antimicrobial agents.…”

“…37 It is widely recognised that both the biofilm structure and the phenotype of cells within a biofilm can afford protection against both host defence processes and administered antimicrobial agents. 36,38 Enhanced resistance of a biofilm to an antimicrobial has been related to failure of the agent to diffuse the biofilm, sequestering of the agent within the biofilm matrix, and the presence of persister cells within the biofilm that have a low activity status that promotes their survival in the presence of an antimicrobial. Studies have shown that antimicrobial activity is elevated up to 500-fold in biofilms when compared with equivalent planktonic studies.…”