Biofilms cause many problems in many different aspects of
life, both biotically and abiotically. They cause biodeterioration of useful
structures leading to extensive maintenance costs, reduced efficacy of
antibiotics in disease systems and dental plaques leading to tooth decay. In disease systems, biofilm recalcitrance
often means that antibiotic dosage needs to be 100-1000 fold higher in order to
be effective, which is impractical as it would then be toxic to the host.
This article studies the effect of lasers on bacterial death
and the disruption of biofilms. Using a Q-switched (pulsed output) ND:YAG (the
crystal that emits the ionic activity of the beam) laser beam, the authors
bombarded Staphylococcus epidermis biofilms
grown on thin polycarbonate substrates, for a duration of <5ns with a peak
stress of >50MPa at a wavelength of 1064nm (i.e. a very short but high
powered beam). This beam specification was chosen due to earlier testing which
showed that it is sufficient to kill bacterial lawns but not powerful enough to
cause thermal damage to the surrounding (host) tissue.
Using this methodology, the authors observed a 55% reduction
in bacterial load in respect to control cultures, but state in the discussion that
higher bacterial reduction can be achieved through stiffer backing plates,
better positioning, and decrease in presence of air bubbles.
Personally I feel that this method is hardly going to
replace toothbrushing, but shows promising application in clinical therapy and
indeed, the authors conclude that the results of this study are the first steps
towards a clinically viable therapeutic method in infected wound treatment,
where antibiotics have proved ineffective. However it is important to note
that, to my best knowledge, I cannot find many studies on the effects of this
type of laser beam on human tissue, and due to the intense heat and ionising
damage caused by the laser, it is difficult to refrain from immediately
thinking of cancer. Nonetheless, the results of this study show the first steps
towards the potential clinical application of lasers in biofilm disruption,
which is heavily needed with the growing prevalence of antibiotic resistance. Moreover
lasers could also have a potential usage in the disruption of biofilms outside
disease systems.
REF: Taylor, Z.D., Navarro, A., Kealey, C.P., Beenhouwer, D.,
Haake, D.A., Grundfest, W.S., Gupta, V. (2010) Bacterial biofilm disruption
using laser generated shockwaves. Conference Proceedings of the Engineering in
the Medicine and Biology Society, 1028-1032.
ACCESSED FROM: http://www.ncbi.nlm.nih.gov/pubmed/21096997
Hi Harri,
ReplyDeleteThis is a very interesting post, you have mentioned that a greater bacterial reduction may be achieved with stiffer plates, precise positioning and low air bubbles, but did the authors use a variety of beam diameters to test bacterial reduction? It would be interesting to see if the percentage of biofilm reduction varies with different beam sizes.
The possibilities of laser removal of biofilms can be applied to clinical use as well as industrial use; if you are interested there is a paper by Nandakumar et al (2004) which also uses lasers to eradicate biofilms. It concentrated on the removal of natural marine biofilms off hard surfaces (titanium and glass) and the results showed a significant reduction of biofilm. The paper explains the potential use on industrial structures, to prevent the pollution of biocides and antifouling substances into the sea.
Nandakumar, K., Obika, H., Utsumi, A., Ooie, T., Yano T., (2004), In Vitro Laser Ablation of Natural Marine Bioļ¬lms, Applied and environmental microbiology, Nov. 2004, p. 6905–6908 Vol. 70, No. 11
Hi Kath,
ReplyDeleteSimple answer: No. The authors didn't mention any change to the positioning of the laser beam at all! I guessed this was due to a number of pilot studies which tested the efficacy of different angles but again, no mention is made of these.
That paper was actually listed underneath the one I have reviewed in my pubmed search! I chose to do this one because with the clinical aspects, I thought it was more significant. Though Nandakumar et al showed significant removal of bacteria - their beam duration was 30s, which would completely fry the host tissue in clinical aplications!