The formation of biofilms by Pseudomonas aeruginosa strains, and methods of its control (review)

Abstract

The majority of natural bacterial populations exist in the form of biofilms, highly-structured multicellular communities incorporated in extracellular polymer matrix of own production. For a considerable part of clinically significant species this form of existence provides optimal conditions for reaching of pathogenic and colonizational potential, and also encourages saving of metabolically inactive part of population which is characterized by a low level of sensitivity to antibiotics impact. The latter plays a significant role in formation of chronic persistent infections resistant to antibiotics treatment.Members of microbial group are united basing on the principle which excludes antagonism, determines their nutritional, energetic and another connections between them and environment. Such a connection of microorganisms community behavior received a special definition of “quorum sensing”. Quorum sensing is an ability of some bacteria (probably, also another microorganisms) to communicate and coordinate their behavior through secretion of substances which are the signals for coordination of certain behavior or interaction between bacteria of the same type or subtype depending on their growth tightness.When the concentration of excreted signaling agents reaches a borderline value the group of bacteria starts working as a single organism. Furthermore, signaling agents for Gram-negative and Gram-positive microorganisms differ. For instance, for Pseudomonas aeruginosa microorganism a signaling molecule of quorum sensing is acyl homoserine lactone, and biofilm created by this pathogen produces pyocyanin which functions as an electronic transporter in current generation. A large-scale investigation of P.aeruginosa biofilm morphology, mechanisms of its production and degradation, peculiarities of formation under different conditions and impact of various factors are at the infancy stage. According to undivided opinion of scientists who investigate this problem the main source of nosocomial diseases and persistence factor of their causative agents in hospital ecosystems from air and water to inner surfaces of catheters and body systems are represented by biofilms. Bacteria of P. aeruginosatype are human opportunistic pathogens which being a part of biofilm may cause different nosological forms of pyoinflammatory diseases with severe course and high fatality in immunocompromised patients. These microorganisms are able to contaminate external and internal surfaces of catheters, probes, respiratory tubes, lenses, and form biofilm on them.The given information determines reasonability of searching the methods of control of biofilm production in P. aeruginosa cultures which can be used to increase the effectiveness of antibiotic treatment in blue pus infection and/or decontamination of medical equipment, and another objects of hospital environment. One of the methods to control biofilms produced by P. aeruginosa on abiotic surfaces from different materials is impact of antiseptics and decontaminants. Modern decontaminants are represented by a wide spectrum of chemical compounds of different classes which have a common ability to destroy microorganisms even in low concentrations. At present the impact of bacteria on separate elements of biofilm formation is considered to be one of the most perspective targets for the action of new antimicrobial medicines. Numerous investigations of recent 40 years demonstrated that the process of biofilm formation is complex and multistage. Currently the principal directions of development of new antimicrobial preparations are the following: development of antiadhesive coatings and preparations able to interrupt the function of eternal structures of cells in charge of adhesion (fimbriae, adhesins); development of preparations that block synthesis or destabilize matrix of biofilm; development of preparations that cause cell adhesion deficiency in microcolony, and block cell fission; development of preparations that block intercellular signaling (quorum sensing), and cause disconnection of cells from biofilm and their transition into plankton existence or resist pathogenicity factor expression. Nowadays the influence of certain physical factors on biological properties of biofilms is studied as well. At the present time the new technology that is photodynamic therapy is in intensive progress. Low intensity electromagnetic radiation has widespread application practically in all areas of medicine. In fact, under the influence of light emitting diode radiation metabolic and functional properties of biological system variety can be significantly changed. According to a number of investigators a direct method of light emitting diode radiation effect provides direct influence on cellular structure elements, moreover it has been proved that membrane structures of cell are the most sensitive to optical radiation effect. It was found that under influence of light emitting diode radiation a breakdown of daily biofilms with inhibition of plankton cells production capacity was observed. All the above allows to assess current problem of medical science and practice that is process of biofilm formation in microorganisms particularly in Pseudomonas aeruginosa strains. Analysis of literature sources shows practicability of research line of specific subject that is proved by crisis of antibiotic therapy observed for now and characterized not only by multitude of resistant microorganisms but also by absence of preparations and infection pathology therapeutic regimen that have assuring effectiveness and therefore search for alternative control methods is critical and challenging.