Polymicrobial communities in hemodialysis fluids: risk factor for morbidity and mortality in chronic renal failure patients

Abstract

Bacteria and fungi form highly structured, often surface-associated, communities termed biofilms. Environmental factors such as pH, temperature, nutrients and oxygen availably added to genes expression, which enhanced or inhibited the metabolic pathways that have influence in adaptation of the planktonic to biofilm growth mode of microorganisms. However, interactions between bacteria-fungus in mixed biofilms on nosocomial microenvironments such as hydraulic circuit of hemodialysis service and the influence of environmental factors such as oxygenation on these mixed communities are not found in the literature. This study proposes to assess the interaction that occurs between bacteria (Pseudomonas aeruginosa, Escherichia coli, Mycobacterium gordonae and Staphylococcus epidermidis) and fungi (Candida parapsilosis, Aspergillus niger and Fusarium spp) in the mixed biofilms formation under aerobic and microaerophilic conditions. Additionally will be quantified endotoxin released by biofilms generated by Gram-negative as well as the sensitivity of all biofilms against three antimicrobials. Strains arising from water circuit of a hemodialysis hospital service for the induction of biofilm formation on microtiter plates are used (96-well), and their biomass and cell viability were accessed by crystal violet and 3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) assays, respectively. The scanning electron microscopy will show the morphology and topography of these biofilms whereas the confocal laser scanning microscopic will aid in location of the microorganisms in the biofilm. The release of toxins by Gram-negative bacteria from biofilms will be quantified by the test "Limulus amebocyte lysate" after the maturation time. The efficacy of the antimicrobials against proposed biofilms will be performed on microtiter plates with quantification of total viable cells by plating on agar. The study may serve as a warning to regulatory agencies to the need for inclusion of biofilms in the standardization of water for use in dialysis centers, since they are focused on growth of free-form organisms. We also focus on the national and international pioneering study covering an undeniable importance of this topic since the world production of dialysis fluid is about 25,000 million liters, making it one of the largest products by volume used in medicine. (AU)