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Objective Pseudomonas aeruginosa effectively facilitate resistance to phagocyte killing by biofilm formation. However,b the cross talk between biofilm components and phagocytes is still unclear. We hypothesize that a biofilm provides a concentrated extracellular source of LPS, DNA and exopolysaccharides (EPS), which polarize neighbouring phagocytes into an adverse hyperinflammatory state of activation. Methods We measured the release of a panel of mediators produced in vitro by murine neutrophils and macrophages exposed to various biofilm components of P. aeruginosa cultures. Results We found that conditioned media from a high biofilm-producing strain of P. aeruginosa, PAR5, accumulated high concentrations of extracellular bacterial LPS, DNA and EPS by 72 h. These conditioned media induced phagocytes to release a hyperinflammatory pattern of mediators, with enhanced levels of $TNF-\alpha$, IL-6, IL12p40, $PGE_{2}$ and NO. Moreover, the phagocytes also upregulated COX-2 and iNOS with no influence on the expression of arginase-1. Conclusions Phagocytes exposed to biofilm microenvironment, called by us biofilm-associated neutrophils/macrophages (BANs/BAMs), display secretory properties similar to that of N1/M1-type phagocytes. These results suggest that in vivo high concentrations of LPS and DNA, trapped in biofilm by EPS, might convert infiltrating phagocytes into cells responsible for tissue injury without direct contact with bacteria and phagocytosis.

Formation of bacterial biofilm on dental surfaces is characteristic for existence of oral microbiota. It was also proved that uncontrolled biofilms on dental surfaces, as well as on biomaterials used in dentistry, are the main cause of oral cavity diseases such as dental caries and periodontitis. For years chlorhexidine (CHX) has been known as an excellent antiseptic and anti-biofilm agent. However, due to some of its unwanted adverse effects novel antiseptics are currently being tested by many laboratories. Our preliminary data have suggested that taurine bromamine (TauBr), a strong antiseptic against planktonic form of various bacteria and an anti-inflammatory agent, may also be a good candidate for treatment of biofilm-associated infections. Nevertheless, beneficial therapeutic effect of TauBr in the treatment of inflammatory acne lesions was not fully supported in vitro in the experimental model of Pseudomonas aeruginosa biofilm. Such discrepancies may be explained by distinct antiseptic resistance of biofilms generated by different microbial species. In this study we have extended the investigations of anti-biofilm properties of TauBr using novel in vitro models of Streptoccocus mutans and Candida albicans biofilms formed on orthodontic appliances. The ability of TauBr to kill the experimental pathogens hidden in a mature biofilm was compared with that of CHX.

Formation of biofilm is observed in a majority of chronic bacterial skin infections such as non-healing wounds. These infections are persistent as they show increased resistance to antibiotics. Moreover, bacteria hidden in biofilm are protected from the host defence system. It raises serious therapeutic problems in human and veterinary medicine. Therefore, novel anti-biofilm therapeutic strategies should be used. It has been shown in vitro that taurine bromamine (TauBr), the product of reaction between taurine and hypobromous acid (HOBr), exerts anti-microbial properties against planktonic form of various bacteria. Moreover, clinical studies have shown that TauBr is effective in the local treatment of skin and mucosa chronic infections. Nevertheless, it is still not clear whether it can kill bacteria hidden in a biofilm or destroy biofilm and enhance the effect of antibiotics. In this study we have investigated the capacity of TauBr to inhibit in vitro the formation of P. aeruginosa biofilm. Preformed biofilm was treated with TauBr alone or TauBr and ciprofloxacin, the antibiotic commonly used in skin infections. Efficacy of TauBr was compared with that of chlorhexidine (CHX), the most effective anti-biofilm agent that has been developed to date. Our results show that TauBr and CHX are able to inhibit the formation of P. aeruginosa biofilm in vitro but only CHX destroys the mature biofilm and effectively kills hidden bacteria. In contrast, only TauBr shows antioxidant properties. It therefore suggests that CHX and TauBr could be combined in treatment of chronic infections associated with biofilm formation and generation of oxidative stress.

antibiotic resistance is a common problem accompanying biofilm-associated chronic infections. new therapeutic strategies are based on a combined application of antiseptics with anti-biofilm agents. Taurine haloamines, taurine chloramine (Taucl) and taurine bromamine (TauBr), show antimicrobial and anti-inflammatory properties, which have been examined in a variety of local infections, including biofilm-associated infections. in contrast to beneficial antimicrobial effects of taurine haloamines against the planktonic form of bacteria, their efficacy against bacteria hidden in biofilm need to be enhanced. one possibility is to use them together with agents capable of destroying components of biofilm matrix. in this study we ask a question whether Taucl or TauBr are effective in killing streptococcus mutans and Porphyromonas gingivalis, major oral bacteria responsible for the development of dental plaque and pathogenesis of periodontal diseases. Moreover, we have examined TauBr and Taucl stability in the presence of n -acetylcysteine ( nac ) and dn ase, agents with known anti-biofilm activity. We have found that TauBr was much stronger than Taucl microbicidal agent against both tested bacterial strains. however, TauBr was less stable than Taucl. nac readily decomposed TauBr but not Taucl. in addition, TauBr inhibited dnase activity, when used in excess. This preliminary study confirms previous opinions that taurine haloamines have great potential in killing oral bacteria. however, further studies are necessary to find anti-biofilm agent(s) which together with Taucl/TauBr will give at least an additive therapeutic effect in the treatment of chronic infections, to support or replace ineffective antibiotic therapy.

Biofilms are consortia of microorganisms (sessile cells) that form on various surfaces including mucosal membranes or teeth. Bacterial biofilms cause many human infections such as chronic sinusitis, acne vulgaris, periodontal diseases, and chronic wounds. These infections are persistent as they show increased resistance to antibiotics and host defense system. Taurine chloramine (TauCl) and taurine bromamine (TauBr) are the physiological products of activated neutrophils, resulting from the reaction between taurine with hypochlorous acid (HOCl) and hypobromous acid (HOBr), respectively. It has been shown in vitro that taurine haloamines exert antimicrobial properties against various pathogenic bacteria. Moreover, clinical studies have shown that both haloamines are effective in the local treatment of skin and mucose infections, including biofilm-related infections. Nevertheless, it has been not tested yet whether they can kill bacteria hidden in biofilm or disrupt biofilm structure. In this study we have investigated the capacity of TauCl and TauBr to inhibit in vitro the formation of P. aeruginosa biofilm. We have also tested their ability to destroy the mature biofilm. Our results suggest that TauBr is able to inhibit in vitro the formation of P. aeruginosa biofilm but cannot destroy the mature biofilm and effectively killed hidden bacteria. In further studies, the combined effect of TauBr and DNase, one of suggested biofilm inhibitors, was tested. Together, we conclude that TauBr is a better than TauCl candidate for local therapy of biofilm-related infections. However, a combined therapy, an application of TauBr together with other anti-biofilm agents (e.g., DNase), seems to be more promising.