Chitosan coated catheters alleviates mixed species biofilms of Staphylococcus epidermidis and Candida albicans

Microorganisms which adhere to the surfaces of indwelling medical implants develop into a sessile microbial community to form monomicrobial or polymicrobial biofilms. Staphylococcus epidermidis and Candida albicans are the most common pathogens co-isolated from device mediated infections. Hence development of catheters coated with anti-fouling substances is of great interest. In this current study, chitosan, extracted from the shells of marine crab Portunus sanguinolentus was coated over the surface of the urinary catheters and checked for its efficacy to inhibit the adherence of both mono and mixed species biofilms. The Extracted Chitosan (EC) coated catheters showed profound activity in reducing the preformed biofilms and the other virulence factors of the pathogens like slime production in S. epidermidis and yeast to hyphal swtich in C. albicans. Furthermore, qPCR analysis showed that EC could downregulate the virulence genes in both the pathogens when grown as monospecies and mixed species biofilms.

Investigation of mixed species biofilm on corrosion of X65 steel in seawater environment

Microbiologically influenced corrosion (MIC) is a complex process involving the cooperative effect of different bacterial species that coexist in the biofilm. Early studies focused on the MIC of single bacterial communities. However, in natural and industrial fields, biofilms are mostly composed of a variety of species. In this work, the effect of interspecific interaction on corrosion of X65 steel was investigated through the mixed culture of sulfate reducing bacteria (SRB) and iron oxidizing bacteria (IOB). Results demonstrated that the mixed microbial consortia created a cooperative effect to aggravate the local corrosion of X65 steel. Compared with the single species, the presence of IOB increased the growth activity of SRB cells and promoted the role of SRB in steel corrosion. The corrosion form on the surface of X65 steel gradually changed to annular pits induced by anaerobic SRB. The succession of dominant bacteria and the development of mixed species biofilm led to an increase in corrosion rate and local corrosion. The corrosion mechanism of X65 steel by mixed species biofilm at different stages was carefully elucidated.

Effect of scaling on the invasion of oral microorganisms into dentinal tubules including the response of pulpal cells-an in vitro study

Objectives

To investigate how scaling affects the penetration of microorganisms into dentinal tubules, how pulpal cells seeded into the pulp cavity respond to bacterial challenge, and how penetration and inflammatory response may depend on the bacterial composition.

Materials and methods

Root canals of 102 extracted human teeth underwent shaping and cleaning. Half of the teeth were subjected to scaling and root planing, the other half remained untreated. Teeth were exposed to either Streptococcus gordonii and Actinomyces oris or S. gordonii and Porphyromonas gingivalis for 10 weeks. Bacterial invasion was assessed in a depth of 1 mm to the root surface. Human pulpal cells were seeded into the cavities to assess the expression of interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1), and matrix metalloproteinase-3 (MMP-3) by real-time polymerase chain reaction and immunoassay.

Results

The percentage of teeth with bacteria detected in dentine was higher when teeth received scaling than when they were untreated: 66.6% versus 44.4% when exposed to A. oris/S. gordonii, and 50% versus 25% when exposed to P. gingivalis/S. gordonii (p = 0.043). Scaling had no impact on IL-8 and MMP-3 expression in pulpal cells. P. gingivalis/S. gordonii caused higher levels of IL-8, MCP-1, and MMP-3 than A. oris/S. gordonii (p = 0.003, p = 0.011, p = 0.037).

Conclusion

Scaling supports the penetration of bacteria into the dentine of extracted human teeth. P. gingivalis may affect the immune response in pulpal cells.

Clinical relevance

Root surface debridement with hand instruments may facilitate bacterial penetration. Other kinds of mechanical instrumentation in this experimental setting should be investigated.

Mixed species biofilm: Structure, challenge and its intricate involvement in hospital associated infections

Hospital associated infections or healthcare associated infections (HAIs) are a major threat to healthcare and medical management, mostly because of their recalcitrant nature. The primary cause of these HAIs is bacterial associations, especially the interspecies interactions. In interspecies interactions, more than one species co-exists in a common platform of extracellular polymeric substances (EPS), establishing a strong interspecies crosstalk and thereby lead to the formation of mixed species biofilms. In this process, the internal microenvironment and the surrounding EPS matrix of the biofilms ensure the protection of the microorganisms and allow them to survive under antagonistic conditions. The communications between the biofilm members as well as the interactions between the bacterial cells and the matrix polymers, also aid in the rigidity of the biofilm structure and allow the microorganisms to evade both the host immune response and a wide range of anti-microbials. Therefore, to design a treatment protocol for HAIs is difficult and it has become a growing point of concern. This review therefore first aims to discuss the role of microenvironment, molecular structure, cell-cell communication, and metabolism of mixed species biofilms in manifestation of HAIs. In addition, we discuss the electrochemical properties of mixed-species biofilms and their mechanism in developing drug resistance. Then we focus on the most dreaded bacterial HAI including oral and gut multi-species infections, catheter-associated urinary tract infections, surgical site infections, and ventilator-associated pneumonia. Further, we highlight the challenges to eradication of the mixed species biofilms and the current and prospective future strategies for the treatment of mixed species-associated HAI. Together, the review presents a comprehensive understanding of mixed species biofilm-mediated infections in clinical scenario, and summarizes the current challenge and prospect of therapeutic strategies against HAI.