Friday, March 3, 2017

What non-antibiotic treatments may be effective against Propionibacterium?

N-acetylcysteine inhibits growth, adhesion and biofilm formation of Gram-positive skin pathogens

Propionibacterium are increasingly acquiring resistance to the antibiotics commonly used to kill them, such as tetracyclines and Clindamycin.

These authors investigated the antimicrobial efficacy of N-Acetylcysteine (NAC) against biofilm phenotypes of Gram-positive and Gram-negative bacteria. 

Although, no clinical isolate of P. acnes has been reported resistant to rifampicin so far, these authors observed that rifampicin resistance emerged rapidly and this strain can form stronger biofilm than the parent strain. Thus, they selected P. acnes VKM Ac-1450 Rifr strain with total resistance to rifampicin and used this microorganism for a multispecies P. acnes and S. epidermidis biofilm model.

The biofilm formation and growth of mixed culture of P. acnes and S. epidermidis was significantly slowed at 12.5 mg/ml of NAC. NAC also has a high disruptive effect on mature P. acnes and S. epidermidis biofilm.

Here's a plot of the growth (solid circles) and biofilm formation of Propionibacterium with different concentrations of NAC

Here's a plot of the relationship of growth (A) and biofilm formation (B) for Staph Epi, Rifampin resistant Propi and a mixture of the two.

In summary, they found that the bacterial growth and biofilm formation of P. acnes was slowed at sub-MIC of NAC (1.56 mg/ml). NAC prevented growth of plantonic cells of P. acnes VKM Ac-1450 Rifr as well as their biofilm formation. This sensitivity of P. acnes to NAC persisted even in the multispecies P. acnes plus S. epidermidis model.

They concluded that NAC appears to be a promising, non-antibiotic alternative to prevent biofilm-associated infections.

They suggest that long-term treatment with NAC might change of the skin microflora composition, in particular a reduction of propionic acid bacteria in comparison with staphylococci. 

Comment: We do not know if modification of the skin micro biome by reducing the Propi prevalence would be beneficial or harmful. However, we are interested in continuing to observe the efficacy of non-antibiotic measures to prevent and remove biofilms. See this related post: Prevention and treatment of propionibacterium biofilms