Antimicrobial resistence in biofilms

PARAJE MARÍA GABRIELA

Science against microbial pathogens: communicating current research and technological advances

Formatex Research Center.

Año: 2011; p. 736 - 744

Despite the level of knowledge gained in recent years, some important aspects of biofilms have still not been clarified. Moreover, advances in bacterial physiology have not yet explained many aspects of training, resistance to chemotherapeutic agents used in clinical practice, and medical complications from bacterial infections associated with medical devices. The ability of microorganisms to form biofilms is closely related to infectious diseases and environmental and biotechnological processes. Currently, biofilms are considered to be virulence factors that constitute a protected mode of growth that allows survival in a hostile environment, by facilitating binding to different surfaces and helping to maintain and protect colonies from different factors, including changes in environmental conditions, the possibility of being swallowed up by the host macrophage or preyed upon by other protozoa, or the effect of antimicrobial agents (ATM). Microbial biofilms are implicated in chronic infections, which are slow and resistant to treatment, associated with adherence to natural tissues and involved in diseases such as native valve endocarditis, periodontitis, quísitca fibrosis, chronic tonsillitis, prostatitis or in artificial implants such as prostheses, catheters diverse lenses contact, intra uterine devices, among others. The microorganisms often associated with biofilms are S. aureus, S. epidermidis, Pseudomonas aeruginosa, Escherichia coli, among others. Another important aspect of biofilms is that by their structural nature and the characteristics of the sessile cells, they confer intrinsic resistance to antimicrobial agents. Several reasons for this have been investigated, although the precise mechanism of how this sensitivity is altered has not been clarified. Although it may be the main mechanism of resistance associated with biofilms, it is postulated that ATM could penetrate the structure, but not be able achieve an effective concentration in some parts of it due to the physical and/or chemical properties of the matrix. The depletion of nutrients and oxygen inside the biofilms might cause the bacteria to be in a dormant state, demonstrating resistance to ATM compared to planktonic cells. The existence of microenvironments that antagonize the action of antibiotics and the degradation mechanisms active in some parts of the biofilms could also be involved. We studied how the activation of oxidative stress causes changes in the physiology of bacteria, with specific phenotypic alterations, biofilms and antimicrobial resistance. Due to the heterogeneous nature of biofilms, it is likely that multiple mechanisms of antimicrobial resistance occur. Currently, resistance to disinfectants and ATM is a growing problem in public health, exacerbated by the use of modern medical devices primarily made of polymers which can promote the adhesion of biofilms and cause chronic infections. This review aims to analyze current knowledge about antibiotic resistance in clinical use of  biofilms (sessile cells) compared to planktonic (free-floating planktonic) cells and describe the different methodologies used. Keywords: biofilms; antibiotics; mechanism of action; oxidative stress