Posts tagged: microbes

Study Shows Increased Effectiveness Of Light-Activated Antimicrobial Agents Against MRSA

Many bacteria capable of causing life-threatening infections are now resistant to a wide range of antibiotics.  It is essential, therefore, that alternatives to antibiotics are developed for use in the prevention and treatment of such infections. Light-activated antimicrobial agents (LAAAs) are one possible new approach to this problem. LAAAs are compounds that display no antimicrobial activity in the dark but, when exposed to light of a certain wavelength, can kill microbes in the vicinity.  One of the essential attributes of any antimicrobial agent, including a LAAA, is that it be effective at low concentrations so as to reduce the risks of any toxicity to the patient.

The new LAAAs as seen through a very powerful electron microscope. The diameter of each particle is approximately 0.000000005 metre.

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Microbial Mob Mentality – In The Wake Of The Vancouver Riots

Clearly, the ability of bacteria to communicate with each other is limited – their unicellular form restricts them in this endeavour.  Bacteria can, however, communicate by giving off signals called quorum sensing molecules.  These molecules are constantly released by bacteria to let each other know how many of them are in the immediate vicinity.  When they realize that they have enough of their buddies around, their behaviour suddenly changes and the whole group begins acting in a different manner, often manifesting as an infection (note: the best lecture that I have seen on quorum sensing is available for free below from TED, and it’s only 20 minutes long).  Only recently, riots quickly engulfed my hometown of Vancouver, and I was struck by how similar the two processes were.  It gives me a small measure of satisfaction to write a piece comparing mindless bacteria to the equally mindless degenerates that briefly infected our city on June 15th.

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Photodynamic Disinfection (PDD) is the Antimicrobial application of PDT (aPDT)

The key features of aPDT can be summarized as follows [1]:

  • Broad spectrum of action, since one photosensitizer can act on bacteria, fungi, yeasts and parasitic protozoa
  • Efficacy independent of the resistance pattern of the given microbe
  • Extensive reduction of pathogen counts in minutes, without damaging host cells
  • No selection of resistant strains after multiple treatments
  • Readily available, non-toxic photosensitizers
  • Relatively low-cost light sources for activation of the photosensitizing agent
  • No cytotoxic effects on key sensitive host cells such as human keratinocytes or fibroblasts

The treatment of topical infections has traditionally relied upon antibiotics in either topical or systemic dosage forms. However, the inexorable increase in antibiotic resistance (including to vancomycin and other glycopeptides) has led to the spectre of potentially untreatable infections, and this in turn has led to the development of alternative antimicrobial approaches based on light-activated chemotherapy 2, 3. Photodynamic Disinfection (called antimicrobial PDT by the scientific community) is an extension to traditional photodynamic therapy (PDT) which was originally focused on oncotherapy and intra-ocular indications, utilizing systemically-administered photosensitizers. Read more »

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