Method Name

Procedure

Advantage

Disadvantage

Direct methods

Direct diffusion method
(Well and disc)

The wood material is directly placed on microbe-inoculated agar or in a well and incubated for recommended time
Presence of the zone of inhibition is considered a positive result

1. Rapid and time saving
2. Applicable for low amount of material
3. Adapted for screening

1. Disc preparation time
2. High variability for quantitative applications
3. Studies only the effect of agar-diffused chemicals
4. May require the sterilization of wood samples

Culture-based microbial survival test

Initial microbial quantity is inoculated on wood samples and after the incubation time, the microbes are recovered, cultured, and viable cells are counted

1. Can study the structural and chemical role of wood components
2. Qualitative and quantitative results
3. Applicable for low amount of material

1. Difficulty in recovering all microbes present in pores
2. Microbial quantification is an extra step needed
3. Only viable cells are identified, while there can be still non-viable infectious cells present

Microscopy

The behavior and distribution of inoculated microbes on wooden structures is observed via microscopy

1. Rapid and time saving
2. Applicable for low amount of material
3. Adapted for screening

1. May require the fixation of samples
2. Difficult to differentiate microbial structures from wooden structures
3. May require competencies of image analysis

ATP luminescence

The ATP of microbes on wood is measured

1. Rapid and easy
2. Applicable for low amount of material
3. Adapted for screening

1. Difficult to differentiate the microbial ATP from other organic debris
2. Adapted only for solid surfaces

Molecular biology methods

The quantity and viability of microbes is tested via nucleic acid amplification 

Accurately measures the microbial survival

1. Expensive
2. Require sophisticated handling 

Extractive based methods

Extractive-based diffusion and dilution method

Extractives are placed on agar or in agar wells, or in broth, after loading on filter paper discs or directly

1. Adapted for qualitative and quantitative antimicrobial studies
2. Specific chemicals can be extracted depending upon the solvent used

1. Involves chemical handling
Extra step of extraction
2. One solvent cannot extract all active components
3. Does not study the role of structure of wood

Bioautography

Extractives are loaded on a chromatographic layer, and then the diffusion of active chemicals is studied for their antimicrobial properties

1. Adapted for qualitative antimicrobial studies
2. Specific chemicals can be extracted depending upon the solvent used and identified on the basis of their diffusion on the chromatographic layer

1. Involves chemical handling and extraction
2. One solvent cannot extract all active components
3. Does not study the role of structure of wood
4. Not a quantitative method

Mass spectrometry

The total profile of microbes is measured

1. Applicable for a low amount of material
2. Accurately measure the content of the active ingredient

For more specific results, the identified compounds are supposed to be tested by other culture-based methods