Bacterial killing assays in ecoimmunology require cross-validation by agreement statistics
Data files
Apr 20, 2026 version files 21.08 KB
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Cell_Based_BKA.xlsx
14.97 KB
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Plasma_Based_BKA.csv
3.31 KB
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README.md
2.80 KB
Abstract
The bacterial killing assay (BKA) is a simple assay that assesses the ability of the constitutive immune system, typically the plasma-based immune system, to clear pathogens in vitro. Historically, this has been accomplished through counting bacterial colonies on solid agar plates (CFU-based), however, over the last 15 years, a technique that makes use of optical density (OD-based) has been steadily gaining in popularity. Although cross-validations have been performed between these two methods in the past, they only compared measurements of growth (colony counts and absorbance) using correlation statistics with plasma. We performed our own method cross-validation using first blood cells (red and white blood cells with plasma removed) and then plasma, and compared measurements of growth and bactericidal ability using both correlation and agreement statistics. Our results found that while there was a weak correlation between colony counts and absorbance at 300nm, we found poor agreement between techniques in the cell-based BKA, with slightly stronger agreement when done with plasma. We believe this is caused by immunological processes, especially in the case of the cell-based BKA, changing the optical properties of the culture.
Dataset DOI: 10.5061/dryad.z8w9ghxtb
Description of the data and file structure
This dataset contains the experimental data obtained during a bacterial killing assay performed on blood cells and plasma isolated from the Mojave desert tortoise. The first dataset is the cell-based bacterial killing assay (BKA) and is split into three separate sheets: the first contains sampling season, tortoise ID, colony counts, and optical density (OD) at 300nm; the second contains sampling season, tortoise ID, colony forming unit (CFU)-based bactericidal ability, OD300-based bactericidal ability, the difference in bactericidal ability between the two methods, and the mean bactericidal ability of the two methods; the final sheet contains tortoise ID, incubation temperature, CFU-based, OD300-based, and OD600-based bactericidal ability, the difference in bactericidal ability between the CFU-based and OD600-based and the OD300- and OD600-based methods, and the mean of the CFU- and OD600-based and OD300- and OD600-based bactericidal abilities. The second dataset is the plasma-based BKA and contains one sheet with the following variables: tortoise ID; CFU-, OD300-, and OD600-based bactericidal ability; the difference in bactericidal ability between the CFU- and OD300-based, CFU- and OD600-based, and OD300- and OD600-based BKAs; and the average bactericidal ability between the CFU- and OD300-based, CFU- and OD600-based, and OD300- and OD600-based BKAs.
Files and variables
File: Cell_Based_BKA.xlsx
Description: Bactericidal ability of tortoise blood cells as measured by colony counts and spectrophotometry. Incubation temperature is in °C; all other variables are unitless.
Colony Counts and Absorbance
- Tortoise ID
- Season
- Colony Counts
- OD at 300nm
Bactericidal ability (CFU and OD300)
- Tortoise ID
- Season
- CFU-based bactericidal ability (BA)
- OD-based bactericidal ability at 300 nm
- Difference in bactericidal ability
- Mean of bactericidal ability
Bactericidal ability (all measures)
- Tortoise ID
- Incubation Temperature
- CFU-based bactericidal ability
- OD-based bactericidal ability at 300 nm
- OD-based bactericidal ability at 600 nm
- Difference in bactericidal ability
- Mean of bactericidal ability
File: Plasma_Based_BKA.csv
Description: Bactericidal ability of tortoise plasma as measured by colony counts and spectrophotometry. Variables are all unitless.
Variables
- Tortoise ID
- CFU-based bactericidal ability
- OD-based bactericidal ability at 300 nm
- OD-based bactericidal ability at 600 nm
- Difference in bactericidal ability
- Mean of bactericidal ability