Automated Colony Counting – Scan 1200 Performance Evaluation
One of the most time-consuming tasks in microbiology laboratories is manually counting colonies on Petri dishes. However, the question is not simply whether automated systems are faster, but whether they can match the accuracy of the manual method.
The performance of the Scan 1200 colony counter was evaluated in a comprehensive study comparing manual and automated counting in accordance with ISO 7218:2007.
How was the comparison conducted?
During the study:
- 6 different microorganisms were examined (E. coli, Bacillus cereus, Pseudomonas aeruginosa, Saccharomyces cerevisiae, Penicillium roqueforti, Lactobacillus casei var. rhamnosus)
- 502 Petri dishes were evaluated on 7 different culture media:
- PCA (Plate Count Agar)
- MacConkey agar
- VRBL (Violet Red Bile Lactose agar)
- EMB (Eosin Methylene Blue agar)
- TBX (Tryptone Bile X-glucuronide agar)
- MRS (de Man, Rogosa and Sharpe agar)
- Sabouraud agar
- more than 45,000 colonies were counted both manually and automatically
The aim was to compare the results of the two methods on a statistically sound basis.
Results?
The study results showed an exceptionally strong correlation between the manual and automated methods.
The lowest correlation coefficient (R²) was 0.9787, indicating a strong linear relationship.
In most cases, the mean log difference represented a deviation of only a few percent. Across the entire study, the average difference between automated and manual counting was 2.35%.
Based on the 95% confidence interval specified in ISO 7218:2007, the automated result fell outside the permitted range in only 8 cases (1.59%).
In practical terms, this means that the Scan 1200 provides reliable colony detection under standard laboratory conditions.
The document also included a time analysis. When counting a single Petri dish, the automated system was significantly faster than the manual method, particularly for medium and high colony counts
On a daily basis—in a laboratory with one user and dishes containing 50–150 colonies—the Scan1200 can provide time savings of up to 80%.
This is not merely a matter of convenience. With high sample volumes, it can deliver a significant increase in capacity.
Traceability and data storage
The system saves every counting result in “session” files containing images of the Petri dishes and the counting data
This provides full traceability, which is particularly important in audited or documentation-intensive environments.
Summary
The performance evaluation of the Scan 1200 shows that automated colony counting is not only faster but also demonstrates good statistical agreement with the manual method.
Strong correlation, low deviation and significant time savings—together, these factors may justify the introduction of automated colony counting in laboratories that need accuracy and efficiency when handling high sample volumes.
This blog post is based on the manufacturer's official application note for the Scan® 1200 entitled “Evaluation des performances” (version 2, 2021.03.30.).
