Sinusitus Savior from the Sea?

I became interested in this article because I am currently recovering from a bout of sinusitus. I originally saw it written up at http://www.sciencedaily.com/releases/2013/02/130218173302.htm (a reprint from a press release by Newcastle University

Full article: Efficacy of a Marine Bacterial Nuclease against Biofilm Forming Microorganisms Isolated from Chronic Rhinosinusitis. Robert C. Shields, Norehan Mokhtar, Michael Ford, Michael J. Hall, J. Grant Burgess, Mohamed Reda ElBadawey, Nicholas S. Jakubovics. PLOS ONE published on: 18th February 2013




As with any scientific article, go to the end of the introduction to (very briefly) see what they actually did:

"The exogenous addition of NucB to biofilms formed by Escherichia coli, Bacillus subtilis or Micrococcus luteus resulted in almost complete removal of bacterial cells from surfaces."

Their explanation is that NucB breaks down extracellular DNA (eDNA) and wipes away biofilms. Simple enough.

A little background: A few years back, they isolated a strain of Bacillus licheniformis from red dulce (sea lettuce) which created antimicrobial compounds and red pigments in a bioreactor (from an article by the same author in Applied and Environmental Microbiology, 2003). The antimicrobial compound was determined to be bacitracin, a widely known antimicrobial derived from the same species, and the pigment was unidentified. Later, they published on the NucB enzyme, derived from the same strain and growth conditions, saying that it causes biofilms to break up (reference 33).

Here, they get mucus from 20 sick folks and fix some of it from two of the patients up for electron microscopy. Figure 1 shows you their EM micrographs and it looks much like you would expect mucus to look. Not sure what the purpose of this is, other than to do some EM on snot, which is kind of cool, I guess...

Thankfully they wised up and stained the bacteria with a FISH probe, which binds to bacterial DNA and is fluorescent green (Figure 2). The probe is supposed to target DNA from living cells, but can get caught up in extracellular DNA giving larger fuzzy areas as seen in 2B. I wonder why the epithelial (blue) cells are in focus in panel A and not in panel B. I also wonder why the probe only showed up in parts of the field, but the authors ascribe this to the handling of the specimens during prep.

This is all warmup. Now we get to the 'meat of the paper'. They isolated 75 strains of bacteria from the patient's mucous and screened them for nuclease producers (11 out of 20 patients had them). They selected 20 representative strains (24 individual isolates) of nuclease producing and non-nuclease producing bugs to test for biofilm formation and there was hardly a difference between the two groups. Then they treated these 24 biofilms and found that 9/9 of the nuclease producing strains and 5/15 of the non-nuclease types were dispersed by their NucB enzyme when compared to a buffer treatment. In reality only 50-75 of the biofilm was dispersed, but that was significant when compared to their negative control.

I wish that they had used another nuclease for comparison. Of course the DNA degrading enzyme is going to disperse biofilms better than buffer solution. Why is this exotic isolate worth more than one found in your backyard (or nose for that matter)?

And now we get to Figure 5. Part A shows the difference in eDNA and iDNA size (obvious that eDNA is smaller than inside the cell) but FH29 seems to be lacking the so-called 30kbps band (it also doesn't produce nuclease). I say so-called because the first lane which is the ladder, does not go that high. It also looks like the DNA could have gotten trapped at the top of the gel. Part B shows that there is clearly more iDNA than eDNA, and their quantification showed just as much DNA for FH29 as the other two strains. Then part C  shows the eDNA for some of the other strains in the study and some of them appear to be lacking on the gel, but does not follow the nuclease/non-nuclease pattern. The thing that really bothers me about part C is that the ladder looks like it has been photoshopped onto the image, and the two halves of the gel have been spliced together as well. Also, the samples with nothing showing up in the gel have some of the highest values through their other quantification method. Sounds like either cross contamination or (more likely) nanodrop is not an accurate measure of DNA quantity.

Overall, not a bad study, but when you look at the science that's actually being reported, they are a LONG way away from putting this onto the drugstore shelves. I would like to see a study comparing NucB enzymes from different species and, of course, clinical trials on animals and perhaps humans if all else goes well. Until then, I will just have to tough it out, neti some seawater, or gargle some hydrogen peroxide. I think I will tough it out.