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Use of confocal scanning laser microscopy in a noninvasive particle image velocimetry method facilitates the detection and estimation of liquid flow velocity in a biofilm systems. A model biofilm, comprising Klebsiella pneumoniae, Pseudomonas fluorescens and Pseudomonas aeruginosa, helps analyze the associations between hydrodynamics and structural heterogeneity. Liquid flow is detected within biofilm pathways.

Abstract Background Bacterial targeting of tumours is an important anti-cancer strategy. We previously showed that strain SL7838 of Salmonella typhimurium targets and kills cancer cells. Whether NO generation by the bacteria has a role in SL7838 lethality to cancer cells is explored. This bacterium has the mechanism for generating NO, but also for decomposing it. Methods Mechanism underlying Salmonella typhimurium tumour therapy was investigated through in vitro and in vivo studies. NO measurements were conducted either by chemical assays (in vitro) or using Biosensors (in vivo). Cancer cells cytotoxic assay were done by using MTS. Bacterial cell survival and tumour burden were determined using molecular imaging techniques. Results SL7838 generated nitric oxide (NO) in anaerobic cell suspensions, inside infected cancer cells in vitro and in implanted 4T1 tumours in live mice, the last, as measured using microsensors. Thus, under these conditions, the NO generating pathway is more active than the decomposition pathway. The latter was eliminated, in strain SL7842, by the deletion of hmp- and norV genes, making SL7842 more proficient at generating NO than SL7838. SL7842 killed cancer cells more effectively than SL7838 in vitro, and this was dependent on nitrate availability. This strain was also ca. 100% more effective in treating implanted 4T1 mouse tumours than SL7838. Conclusions NO generation capability is important in the killing of cancer cells by Salmonella strains.

A study was conducted to examine the metabolic activity like oxygen consumption and acid formation and viability and the effect of antimicrobial chlorhexidine (CHX) treatment on the physiology of the dental biofilms during exposure to sucrose. The CHX exposure was observed to reduce the metabolic activity and microbial viability at the biofilm surface and drove metabolic activity deeper into the biofilm.