EXPERIMENTAL RESEARCH
Dentistry
doi: 10.25005/2074-0581-2026-28-2-471-479
DIGITAL SEMI-QUANTITATIVE COLONY COUNTING ON SECTOR PLATES: REPEATABILITY ACROSS INOCULUM LEVELS (CANDIDA ALBICANS)

YA.N. KHARAKH1, P.YU. KOLESNIKOV2,3, S.N. KERASOV1, V.V. ALYAMOVSKIY4, A.S. OGANESYAN1, V.N. TSARYOV5, S.D. ARUTYUNOV1

1Department of Prosthodontic Dentistry and Digital Technologies, Russian University of Medicine, Moscow, Russian Federation
2Laboratory of Human Microbial Ecology, State Scientific Center of the Russian Federation – Institute of Biomedical Problems of the Russian Academy of Sciences, Moscow, Russian Federation
3Laboratory of Molecular Biological Research, Russian University of Medicine, Moscow, Russian Federation
4Department of Propedeutics of Therapeutic Dentistry, Russian University of Medicine, Moscow, Russian Federation
5Department of Microbiology, Virology and Immunology, Russian University of Medicine, Moscow, Russian Federation

Objective: This study aimed to evaluate the repeatability of a semi-quantitative digital growth metric for colony counting on sector plates and to determine its practical working range using a Candida albicans model.

Methods: A 24-hour culture of C. albicans grown on meat-peptone agar was standardized to 0.5 McFarland units. Serial dilutions were prepared to achieve initial inoculum levels of 10⁰, 10², 10⁴, 10⁶, and 10⁸ CFU/mL. Sectoral seeding (100 µl) was performed on meat-peptone agar plates, followed by incubation at 37°C for 24 hours (three independent replicates per level). Digital counting was performed using automated image recognition with the Scan 500 automatic colony counter (software version 6.3.8.0; Interscience, Saint Nom-la-Bretèche, France) in "Total Count" mode with fixed processing parameters. Non-microbial artifacts were manually removed to ensure count accuracy. The primary dependent variable was the U-metric, defined as the operator-corrected number of recognized colonies.

Results: The distributions of the U index differed significantly across initial load levels (Kruskal-Wallis H-test, p=0.012). Repeatability was range-dependent: low levels exhibited zero values and high variability (CV: 173.2% for 10⁰ and 102.4% for 10²), while the 10⁴-level showed minimal variance (CV: 6.1%). At high ranges, the relationship between the U-metric and nominal load was non-monotonic. The number of artifacts removed by the operator ranged from 0 to 99 per plate.

Conclusion: The U-metric serves as a standardized digital count – combining fixed recognition settings with operator correction – suitable for "control vs. experiment" comparisons using a consistent protocol. For this specific model, the practical working range was approximately 10⁴ CFU/mL.

Keywords: Candida albicans, microbial colony counting, automated image processing, reproducibility, microbiological techniques, culture methods.

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Authors' information:

Kharakh Yaser Naserovich,
Candidate of Medical Sciences, Associate Professor of the Department of Prosthodontic Dentistry and Digital Technologies, Russian University of Medicine
Researcher ID: AAI-6091-2021 Scopus ID: 57204823557
ORCID ID: 0000-0001-7181-8211
SPIN: 7217-1160
Author ID: 949859
E-mail: c.kharakh@gmail.com

Kolesnikov Pyotr Yuryevich,
Junior Researcher, Laboratory of Human Microbial Ecology, State Scientific Center of the Russian Federation – Institute of Biomedical Problems of the Russian Academy of Sciences; Junior Researcher, Laboratory of Molecular Biological Research, Russian University of Medicine
Researcher ID: ACD-4368-2022
Scopus ID: 57954196100
ORCID ID: 0000-0003-2947-726X
SPIN: 3349-0841
Author ID: 1239130
E-mail: petrs8@mail.ru

Kerasov Stefan Nikolaevich,
Postgraduate Student, Department of Prosthodontic Dentistry and Digital Technologies, Russian University of Medicine
Scopus ID: 59407222500
ORCID ID: 0009-0004-3144-2781
SPIN: 7994-8670
Author ID: 1277964
E-mail: stefankerasov@gmail.com

Alyamovskiy Vasiliy Viktorovich,
Doctor of Medical Sciences, Full Professor, Professor of the Department of Propedeutics of Therapeutic Dentistry, Russian University of Medicine
Researcher ID: H-8834-2012
ORCID ID: 0000-0001-6073-2324
SPIN: 2830-5640
Author ID: 614955
E-mail: valyamovsky@gmail.com

Oganesyan Artak Stepanovich,
Applicant for a Scientific Degree, Department of Prosthodontic Dentistry and Digital Technologies, Russian University of Medicine
ORCID ID: 0009-0009-5127-7847
SPIN: 3051-2946
Author ID: 1217531
E-mail: artac@yandex.ru

Tsaryov Viktor Nikolaevich,
Doctor of Medical Sciences, Full Professor, Head of the Department of Microbiology, Virology and Immunology, Russian University of Medicine
Scopus ID: 7005569282
ORCID ID: 0000-0002-3311-0367
SPIN: 8180-4941
Author ID: 638394
E-mail: nikola777@rambler.ru

Arutyunov Sergey Darchoevich,
Doctor of Medical Sciences, Full Professor, Head of the Department of Prosthodontic Dentistry and Digital Technologies, Russian University of Medicine
Researcher ID: AAG-1917-2020
Scopus ID: 6601980084
ORCID ID: 0000-0001-6512-8724
SPIN: 1052-4131
Author ID: 262790
E-mail: sd.arutyunov@mail.ru

Information about support in the form of grants, equipment, medications

The authors did not receive financial support from manufacturers of medicines and medical equipment

Conflicts of interest: No conflict

Address for correspondence:

Kharakh Yaser Naserovich
Candidate of Medical Sciences, Associate Professor of the Department of Prosthodontic Dentistry and Digital Technologies, Russian University of Medicine

127006, Russian Federation, Moscow, Dolgorukovskaya str., 4

Tel.: +7 (916) 9618007

E-mail: c.kharakh@gmail.com


This work is licensed under a Creative Commons Attribution 4.0 International License.

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