ClO2 Study - P. larvae Spores on Wood

From wood on 5-10-15.
From metal on 5-13-15.

I was able to count colonies of P. larvae that grew on MYPGP agar. These spores were exposed to ClO2 gas on pine chips for six hours.

How to calculate CFU/mL
(CFU * Dilution Factor * Volume Factor)
or
(# CFU) * ( 1 / 10^ dilution factor) * ( 1 / volume plated in mL) = CFU / mL
ex:
3 * ( 1 / 10^ (-4)) *  ( 1 / 0.01mL) = 3x10^6 CFU /mL

ClO2 conc	CFU/mL	CFU/mL
0 mg	14000	1.40E+04
25 mg	9000	9.00E+03
50 mg	950	9.50E+02
100 mg	200	2.00E+02

Spore stock #14 was added to each pine chip. 1.6x10^6 CFU/mL was the concentration of this spore stock, which means there was 1.6x10^5 CFU added to each pine chip. That also means there was only about a 8.75% spore recovery from the pine chip that wasn't exposed to any ClO2 gas, which is terrible. Ideally, >90% recovery would be preferable. 

I attribute the poor spore recovery in part to the pine chips becoming saturated and portions of the spore stocks soaking through and onto the petri plate where it was drying. Another possible contributor could be due to the properties of the pine chip with retaining the spores once re-suspended. I will have to alter my procedure to account for these possibilities. Either by added smaller volumes of spores at a time and allow them to dry before adding the entire volume. I may also try to locate some thicker pine chips to use that wont become saturated as quickly with only 100 uL volume.

Also, there appeared to be a lot of different colony morphologies present on the MYPGP agar plates, more than usual for P. larvae. It could be related to other endospores already present in the pine chips that survived the autoclave sterilization process.

//EWW