How is Microbial Growth Rate Associated with Biofilm Formation?

Mina Izadjoo, PhD:

My name is Mina Izadjoo. I'm the President and also Chief Science Officer for Integrated Pharma Services. Integrated Pharma Services is a contract research organization in Rockville, Maryland.

The focus of the poster is the results of a 2-year study that we conducted in my laboratory, and the study was focused on trying to understand if there is any association between the rate of microbial growth and formation of biofilm. And to be more relevant to what happens in a clinical setting, we tested organisms that were clinical isolates and a total of 157 gram positive and gram negative organisms were tested to find out if we can see any association.

There were several reasons why we were interested in this study. One, simply to have a better understanding of biofilms and the difference between gram positive and gram negative organism. The second reason was that I had a lot of interest in coming up with standardized methodologies for evaluating biofilms that are cost-effective and relatively high throughput. I thought if I can develop a tool that other scientists can use when they're interested in screening anti-biofilm related products and therapeutics, or simply doing research, I felt like this is a contribution that would be valuable. Most of the work that we did was trying to optimize that methodology. At the conclusion we showed that simply using a 96 well microtiter plate and looking at the biofilm formation over time, you can get very valuable information as far as how these organisms behave is not only a single time point because most of the biofilm studies are done, I hardly have seen things that is older than 24 or 48 hours, so that platform allows us to monitor biofilm over time in a very cost-effective and consistent manner.

The third area that I think it was important for biofilm staining scientists usually use crystal violet. Crystal violet is a toxic stain, and at the conclusion of this study, we were able to demonstrate that other types of staining, such as safranin O, which are not as toxic, the results are as consistent as crystal virus, so we strongly also encourage scientists to look into replacing crystal violet with this safe stain.

What was surprising is simply having a lot of organisms, that doesn't translate into biofilms, because biofilms, we always think about biofilms as communities and a lot of organisms. What we show, just having a high growth rate or a high biomass, that doesn't mean that you have a strong biofilm. The other thing that we observed that for gram negatives, the behavior was very different than gram positive. For example, Pseudomonas, Acinetobacter, these are the organisms that are of significant, I would say, interest to the wound care professionals because it's difficult to get rid of them. Those organisms, the growth rate was not as high, but they made the strongest biofilm. That gives, I would say, wound care professionals a different perspective, and that is looking at the organisms that are available on a wound side, gram positive versus gram negative, there is a difference. I hope that they would use more relevant therapeutics considering that not all biofilms are the same.

I am hoping that in the near future there is going to be commercially available tools such as what we have for researchers to use this system and use it for understanding the biofilms and also for drug discovery. There is not a commercially available very high throughput system that is cost-effective and easy to use, and I'm hoping that eventually what we have proposed can be commercialized.

What I wanted to add to the discussion is in wound care, we know the importance of biofilm. We know that biofilms and pathogenic organisms, they're impediment to wound healing. I would say there should be more dialogue between clinicians and researchers. Even early discovery, such as what we have found out in our laboratory, can be shared with the clinicians and hopefully that would help them with making better decisions for treating patients that are suffering from chronic wound infections.