A New Antimicrobial Agent: N Atoms Produced by Plasma

Today, plasma appears to be a promising technology for bacterial inactivation. N₂-O₂ afterglow has already proved its efficiency for oral bacteria inactivation and the presumed role of Oxygen atoms and UV have been studied. Pure N₂ plasma produces Nitrogen atoms without UV emission. N atoms are less aggressive for instruments than O-atoms and allow a treatment temperature near to 30°C.

Objectives:

The objective of this work is to evaluate the inactivation of Escherichia coli by N-atoms.

Methods:

Esherichia coli, non-sporulating gram negative bacteria, is used. Different bacterial concentrations (from 10¹⁰ to 10⁴cfu/ml) are exposed to N atoms, for various treatment times (from 2 to 40 min). N atoms are produced by plasma (microwave discharge at 100 W, 6.65 mbar, 1Ln /min). After treatment, surviving bacteria are counted on Petri dishes.

Results:

A decrease of 6 logs of E. coli is obtained after 30 minutes of treatment, at ambient temperature. The D-value (Decimal Value), determined as the time for a one-log₁₀ reduction, is 5 min.

Conclusions:

N-atoms produced by plasma are efficient on Escherichia coli inactivation. Pure nitrogen post-discharge offers many advantages. The lack of oxygen and UV emission in the treatment chamber prevents any oxidation or damage of the medical devices. This process is particularly safe for polymers as treatment takes place at ambient temperature. Nitrogen is a non toxic and quite cheap gas. New experiments need to be performed in order to test other substrates (Gram+ bacteria, mycobacteria, and spores such as Bacillus stearothermophilus).