Photodynamic Inactivation of Legionella Pneumophila Biofilm Formation by Cationic Tetra- and Tripyridylporphyrins in Waters of Different Hardness

The bacterium Legionella pneumophila is still one of the probable causes of waterborne diseases, causing serious respiratory illnesses. In the aquatic systems, L. pneumophila exists inside free-living amoebae or can form biofilms. Currently developed disinfection methods are not sufficient for complete eradication of L. pneumophila biofilms in water systems of interest. Photodynamic inactivation (PDI) is a method that results in an antimicrobial effect by using a combination of light and a photosensitizer (PS). In this work, the effect of PDI in waters of natural origin and of different hardness, as a treatment against L. pneumophila biofilm, was investigated. Three cationic tripyridylporphyrins, which were previously described as efficient agents against L. pneumophila alone, were used as PSs. We studied how differences in water hardness affect the PSs’ stability, the production of singlet oxygen, and the PDI activity on L. pneumophila adhesion and biofilm formation and in biofilm destruction. Amphiphilic porphyrin showed a stronger tendency for aggregation in hard and soft water, but its production of singlet oxygen was higher in comparison to tri- and tetracationic hydrophilic porphyrins that were stable in all water samples. All three studied porphyrins were shown to be effective as PDI agents against the adhesion of the L. pneumophila to polystyrene, against biofilm formation, and in the destruction of the formed biofilm, in their micromolar concentrations. However, a higher number of dissolved ions, i.e., water hardness, generally reduced somewhat the PDI activity of all the porphyrins at all tested biofilm growth stages.

Maggot Therapy in Chronic Wounds: New Approaches to Historical Practices

Blowfly larvae of Lucilia sericata (Meigen) (Diptera: Calliphoridae) are well established as debridement agents in nonhealing wounds. Maggot therapy (MT) experienced reduced application following adoption of Penicillin and other antibiotics, but the advent of antibiotic resistance and the growing global wound burden have boosted demand for new therapies. The mechanisms of action are well accepted, with debridement, disinfection, biofilm destruction, and inhibition, as well as the stimulation of tissue growth uniformly acknowledged as a remarkable biotherapy. The mechanisms of action, while well-recognized, are still being examined. The efforts to understand isolated aspects of a complex system, have resulted in a tendency to approach the field from simplified viewpoints that remove the holistic system of the larvae. Furthermore, clinical studies have conflated wound debridement and healing in definitions of ‘success’. Thus, both in vitro and clinical studies have reported mixed results, presenting some uncertainty regarding the utility of MT that prohibits routine clinical adoption. This review builds from the generally accepted basic mechanisms to justify a future for MT that encompasses larval-bacterial symbioses as the basis to a holistic system. Symbioses are well documented in the Insecta, and literature in MT supports the existence of established symbiotic associations that provide enhanced debridement action. The future of MT requires consideration of a biological system that confers enhanced antimicrobial action on larvae when selective pre-exposure to carefully selected symbionts is adopted. In treating contemporary infections, there is much to be gained from reflecting on the natural biology of the organism, as MT was used with success long before we sterilized the system.

Novel Chronic Wound Healing by Anti-biofilm Peptides and Protease

Chronic wounds have made a challenge in medical healthcare due to their biofilm infections, which reduce the penetrance of the antibacterial agents in the injury site. In infected wounds, the most common bacterial strains are Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa). Biofilm disruption in chronic wounds is crucial in wound healing. Due to their broad-spectrum antibacterial properties and fewer side effects, anti-biofilm peptides, especially bacteriocins, are promising in the healing of chronic wounds by biofilm destruction. This study reviews the effects of antimicrobial and anti-biofilm agents, including bacteriocins and protease enzymes as a novel approach, on wound healing, along with analyzing the molecular docking between a bacterial protease and biofilm components. Among a large number of anti-biofilm bacteriocins identified up to now, seven types have been registered in the antimicrobial peptides (AMPs) database. Although it is believed that bacterial proteases are harmful in wound healing, it has recently been demonstrated that these proteases like the human serine protease, in combination with AMPs, can improve wound healing by biofilm destruction. In this work, docking results between metalloprotease from Paenibacillus polymyxa (P. polymyxa) and proteins of S. aureus and P. aeruginosa involved in biofilm production, showed that this bacterial protease could efficiently interact with biofilm components. Infected wound healing is an important challenge in clinical trials due to biofilm production by bacterial pathogens. Therefore, simultaneous use of proteases or anti-biofilm peptides with antimicrobial agents could be a promising method for chronic wound healing.

Quaternary ammonium silane (k21) based intracanal medicament triggers biofilm destruction

Background Compare antimicrobial efficacy of a quarternary ammonium silane (QAS)/k21 as an intracanal medicament against E. faecalis and C. albicans biofilms formed on root dentin. Methodology Dentin blocks were sterilized and E. faecalis and C. albicans microbial colonies were counted for colony-forming-units against 2%k21, 2%CHX and Ca(OH)2 medicaments. Biofilm colonies after 7 days on dentin were analysed using confocal laser scanning microscopy with live/dead bacterial viability staining. TEM was done to study dentin collagen matrix. Dentin discs from 3rd day and 7th day well plate was used for Raman spectra and observed under fluorescent-microscope. Docking studies were carried out on MMP-2 S1 binding-domain with k21. Results There was reduction of E. faecalis/C. albicans when k21, chlorhexidine and calcium hydroxide were used with highest percentage in 2%k21 treated specimens. 2%k21 showed dense and regular collagen network with intact cross-banding and decreased Raman intensity for 2%k21 on 3rd day. NaOCl + k21 showed least adherence, whereas saline groups showed highest adherence of E. faecalis and C. albicans to root-canal dentin. Alizarin red staining of hDPSCs revealed calcium deposition in all groups with significant difference seen amongst 2%k21 groups. MMP-2 ligand binding was seen accurately indicating possible target sites for k21 intervention. Conclusion 2%k21 can be considered as alternative intracanal medicament.

Enhancement in the antibacterial activity of cephalexin by its delivery through star-shaped poly(ε-caprolactone)-block-poly(ethylene oxide) coated silver nanoparticles

The antibacterial activity of silver nanoparticles (AgNPs) stabilized with a four-armed star-shaped poly(ε-caprolactone)-block-poly(ethylene oxide) copolymer [St-P(CL-b-EO)] and its application as a drug delivery vehicle for cephalexin (Cp) was evaluated against pathogenic Staphylococcus aureus . The prepared AgNPs were characterized by ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, zeta sizer and atomic force microscopy (AFM). The antibacterial efficiency of Cp is enhanced several-fold by its delivery through complexation with St-P(CL-b-EO)-AgNPs, monitored by microplate assay and biofilm destruction studies. Finally, the visual destruction of bacterial cells and its biofilms by employing Cp and its conjugates at their minimum inhibitory concentration (MIC 50 ) and minimum biofilm inhibitory concentration (MBIC 50 ), respectively, is observed by topographic imaging by AFM. Enhanced antibacterial activity of St-P(CL-b-EO)-AgNPs loaded Cp is attributed to penetrative nature of the drug cargo St-P(CL-b-EO)-AgNPs towards the bacterial cell wall.

Bacteriophage therapy against Pseudomonas aeruginosa biofilms: a review

Multi-Drug Resistant (MDR) Pseudomonas aeruginosa is one of the most important bacterial pathogens that causes infection with a high mortality rate due to resistance to different antibiotics. This bacterium prompts extensive tissue damage with varying factors of virulence, and its biofilm production causes chronic and antibiotic-resistant infections. Therefore, due to the non-applicability of antibiotics for the destruction of P. aeruginosa biofilm, alternative approaches have been considered by researchers, and phage therapy is one of these new therapeutic solutions. Bacteriophages can be used to eradicate P. aeruginosa biofilm by destroying the extracellular matrix, increasing the permeability of antibiotics into the inner layer of biofilm, and inhibiting its formation by stopping the quorum-sensing activity. Furthermore, the combined use of bacteriophages and other compounds with anti-biofilm properties such as nanoparticles, enzymes, and natural products can be of more interest because they invade the biofilm by various mechanisms and can be more effective than the one used alone. On the other hand, the use of bacteriophages for biofilm destruction has some limitations such as limited host range, high-density biofilm, sub-populate phage resistance in biofilm, and inhibition of phage infection via quorum sensing in biofilm. Therefore, in this review, we specifically discuss the use of phage therapy for inhibition of P. aeruginosa biofilm in clinical and in vitro studies to identify different aspects of this treatment for broader use.

Detection of Water Purity Levels by Using Biofilm as A Bio- Chip

Waste water treatment is the process of removing contaminants from wastewater. It includes physical, chemical, and biological processes to remove these contaminants and produce environmentally safe treated wastewater. The present work relates to a microbial technology enabled method in which biofilm, formed by a single psychrophilic bacterial culture, was used as a biochip to detect the water impurities. There was an optimum concentration limit of different metals and organic compounds of drinking water set by ISI and WHO. Here different metals, like Ca2+, Cu2+, Fe3+, Mg2+, Mn2+, Zn2+, Ar2+, Hg2+ and organic compounds, like benzene, toluene, DMSO, Di-Chloro phenol, chloroform were mixed with water at higher concentration than the optimum limit. Now the impurities of that contaminated water was detected by the biofilm destruction method. The change of Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) of different water samples were also detected by the biofilm destruction.