Preservative that ONLY kills Gram-negative bacteria

Tagged: gram negative, preservative

Formulating

Preservative that ONLY kills Gram-negative bacteria

Posted by Bluebird on June 6, 2023 at 6:48 pm

Does anyone know any preservative or a preservative mix that ONLY kills Gram-negative bacteria, or mainly kills Gram-negative bacteria only? I read potentially ethylhexylglycerin, but also read a paper or two that contradicted that.

PhilGeis replied 11 months ago 4 Members · 11 Replies
- gram negative
- preservative
11 Replies

Abdullah

Member
June 6, 2023 at 6:52 pm

Phenoxyethanol
- Bluebird
  
  Member
  June 6, 2023 at 10:44 pm
  
  Thank you, I just ordered it to try.
  
  My formulation is a low pH (~4) water type.
  
  Do you know whether people would normally directly dissolve phenoxyethanol into the final product (did read low solubility in water); dissolve in Tween 80 or such and then put into the rest; or use some other method?
  - Abdullah
    
    Member
    June 7, 2023 at 7:27 pm
    
    What is in the product?
    
    Never mix with Tween 80.
    
    Heating the product a bit or high shear mixer will accelerate dissolving.
    
    You need something for gram+/y/m too.
Graillotion

Member
June 6, 2023 at 11:08 pm
EHG is a potentiator. Helps thing like Phenoxy do a better job….EHG is the cell membrane disruptor.

Not sure what you mean…by just Gram -…as Phenoxy will also zap the gram +.
- This reply was modified 11 months ago by Graillotion.
- This reply was modified 11 months ago by Graillotion.
- Bluebird
  
  Member
  June 7, 2023 at 1:07 am
  After I read Abdullah’s comment I searched, and found that the minimum inhibitory concentration for Staph is more than twice higher than that of E. coli and Pseudomonas. So his comment may be true (I hope so).
  
  https://www.sci-hub.se/10.1111/j.1468-2494.2010.00619.x
  
  But I will have to test whether it’s of sufficient power using the bacteria myself.
  - This reply was modified 11 months ago by Bluebird.
  - Abdullah
    
    Member
    June 12, 2023 at 12:10 am
    
    @PhilGeis in this paper Table V and Table VI, diazolidinyl urea 0.25%+ CMI MI 3ppm failed for Candida albicans but diazolidinyl urea 0.125%+CMI MI 3ppm passed with A criteria in the same cream product. <div>
    
    Any comments on why this happened?
    
    </div>
    - PhilGeis
      
      Member
      June 12, 2023 at 12:21 am
      
      Formaldehyde releasers and isothiazolinones are not that great vs fungi. In any case, we can’t use isothiazolinones in leave on products like creams due to sensitization,
PhilGeis

Member
June 10, 2023 at 5:22 am

You might also consider phenylethyl alcohol. At low concentration, it’s used in media to selectively isolate staph from a Gram negative mixed culture. It’s not that great vs. pseudomonads and doubt you’ll find much antifungal efficacy.

https://microbeonline.com/phenylethyl-alcohol-agar-pea-principle-composition-and-preparation/

I gather you’re looking at a Gram positive probiotic - is this your “change the microbiome” deodorant?
- Bluebird
  
  Member
  June 10, 2023 at 9:51 pm
  
  Thanks, good to know phenylethyl alcohol.
  
  And oh, I meant by “change the microbiome”: I do believe that many if not most deodorants do affect the microbiome, synthetic and “natural” deodorants alike.
  - Bluebird
    
    Member
    June 10, 2023 at 9:52 pm
    
    Having Gram + only vs Gram - only preservatives help if I want to do a challenge test with both kinds into the product, but plate out separately and do selection.
  - PhilGeis
    
    Member
    June 11, 2023 at 1:08 pm
    
    Why do you say that? It is extremely hard to study the microbiome of the axilla. Culture methods are useless and molecular methods are complicated by the 3 dimensional elements skin and hair follicles and the spatial and microbial aspects of odor production..