GB/T 14926.4-2026 Laboratory animal—Method for examination of pathogenic dermal fungi English, Anglais, Englisch, Inglés, えいご
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ICS 13.220.10
CCS H 57
National Standard of the People's Republic of China
GB/T 14926.4-2026
Replaces GB/T 14926.4-2001
Laboratory animal - Method for examination of pathogenic dermal fungi
实验动物 皮肤病原真菌检测方法
Issue date: 2026-01-28 Implementation date: 2027-02-01
Issued by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
the Standardization Administration of the People's Republic of China
Contents
Foreword
Introduction
1 Scope
2 Normative References
3 Terms and Definitions
4 Principle
5 Main Equipment and Materials
6 Culture Media and Reagents
7 Detection Procedure
8 Operating Steps
9 Result Reporting
Laboratory Animals — Detection Method for Dermatophytic Fungi
1 Scope
This document describes the detection method for dermatophytic fungi in laboratory animals.
This document applies to the detection of dermatophytic fungi in laboratory animals such as mice, rats, guinea pigs, hamsters, rabbits, dogs, and monkeys.
2 Normative References
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 14926.42-2001 Laboratory animal – Bacteriological examination – Collection of specimens
GB/T 14926.43-2001 Laboratory animal – Bacteriological examination – Staining, media and reagents
3 Terms and Definitions
No terms and definitions are required for this document.
4 Principle
Dermatophytic fungi exhibit specific growth, morphological, physiological, and biochemical characteristics on culture media. Typical pathological forms, such as scales, broken hairs, pustules under the stratum corneum, folliculitis, and onychomycosis, can be observed in parasitized hair or stratum corneum.
5 Main Equipment and Materials
5.1 Inoculating needle/spatula.
5.2 Sterile inoculation hood.
5.3 Incubator, 28°C.
5.4 Biological microscope.
6 Culture Media and Reagents
6.1 Sabouraud dextrose agar (SDA).
6.2 Dermatophyte test medium (DTM).
6.3 Potassium hydroxide-dimethyl sulfoxide solution.
6.4 Lactophenol cotton blue stain.
7 Detection Procedure
The specific detection procedure is shown in Figure 1.
8 Operating Steps
8.1 Sampling
Collect fur/hair and skin scales. Sample collection shall be carried out according to the requirements of 4.2 in GB/T 14926.42-2001.
8.2 Direct Examination
Place the specimen on a slide and add one drop of potassium hydroxide-dimethyl sulfoxide solution. Cover with a coverslip and let stand for 10 min to 15 min. Gently press the coverslip, absorb the surrounding liquid, and observe under a microscope.
8.3 Isolation Culture
Inoculate the specimen onto a Sabouraud dextrose agar slant at three points. Place in a 28°C incubator for culture. Observe colony morphology after 7 to 14 days. Prepare a smear from the culture for microscopic examination. Sabouraud dextrose agar and DTM shall be prepared according to the requirements of 4.16 and 4.17 in GB/T 14926.43-2001.
8.4 Smear Microscopy
Place one drop of lactophenol cotton blue stain on a slide. Using an inoculating needle or loop, transfer a portion of the culture into the stain. Cover with a coverslip and examine microscopically.
8.5 Identification
8.5.1 Determine the fungal species based on colony morphology and microscopic examination results, referring to the morphological characteristics of the following main dermatophytic fungi that can cause dermatophytosis in animals:
a) Trichophyton mentagrophytes: This fungus grows rapidly on Sabouraud dextrose agar at 28°C. Colonies are flat, with a texture ranging from granular to powdery, white to yellowish-white, sometimes pale pink, grey, or yellow. The reverse side is pale yellow to dark brown, often with radiating brown furrows. Microscopically, numerous microconidia, some macroconidia, and spiral hyphae are observed. Microconidia are predominantly spherical, produced laterally and terminally on multi-branched hyphae, forming large clusters. Macroconidia are relatively common, cylindrical, measuring (20 μm – 50 μm) × (7 μm – 10 μm), with thin, smooth walls, mostly having 3 to 4 septa.
b) Trichophyton interdigitale: This fungus grows rapidly on Sabouraud dextrose agar at 28°C. Colonies are flat, sometimes folded, with a texture ranging from powdery to velvety/ downy, white with a cream-colored center, sometimes pink or grey. The reverse side is cream-colored to dark brown. Microscopically, numerous microconidia are observed; macroconidia and spiral hyphae are rarely seen. Microconidia are predominantly spherical, produced laterally and terminally on multi-branched hyphae. Macroconidia, if present, are sparse, cylindrical with thin, smooth walls, and have 3 to 4 septa.
c) Microsporum gypseum: This fungus grows rapidly on Sabouraud dextrose agar at 28°C. Colonies are initially white, gradually turning into yellowish to brownish-yellow powdery colonies. The reverse side of the medium is brown. Microscopically, numerous macroconidia are observed, fusiform (spindle-shaped) with 4 to 6 septa, measuring (12 μm – 13 μm) × (40 μm – 60 μm), with thin, rough, echinulate walls. Hyphae are sparse. A few microconidia may be seen, which are single-celled, clavate (club-shaped), measuring (2.5 μm – 3.5 μm) × (3 μm – 5 μm). Racquet hyphae, pectinate hyphae, nodular bodies, and chlamydospores may also be observed. Species identification is based primarily on colony morphology and macroconidia characteristics. Differentiation from Trichophyton mentagrophytes is necessary.
d) Microsporum canis: This fungus grows rapidly on Sabouraud dextrose agar at 28°C. Colonies are initially downy/velvety, becoming woolly after 2 weeks, often covering the slant, with the center tending towards a powdery texture. Colony color changes from white to pale brownish-yellow. The reverse side is orange-yellow or reddish-brown. Microscopically, septate hyphae and numerous characteristic fusiform macroconidia are observed. Macroconidia are broad in the center, tapering towards the ends, measuring (15 μm – 20 μm) × (60 μm – 125 μm), with thick, rough, echinulate walls (especially at the tips), and multi-septate, typically with 5 to 15 septa. Microconidia are fewer, single-celled, clavate (club-shaped), measuring (2.5 μm – 3.5 μm) × (4 μm – 7 μm). Racquet hyphae, pectinate hyphae, nodular bodies, and chlamydospores may be seen. On rice medium at room temperature, hyphae are denser, colonies gradually become powdery, and the medium turns brownish-yellow; microscopic examination reveals numerous macroconidia. Species identification is based primarily on colony characteristics and macroconidia morphology.
e) Trichophyton simii: This fungus grows rapidly on Sabouraud dextrose agar at room temperature. Colonies are flat or slightly folded and raised, with rapid growth, texture granular to powdery, surface white to yellow, reverse yellow or reddish-brown. Microscopically, numerous clavate macroconidia are observed. They are thin-walled, smooth, typically with 5 to 10 septa of varying sizes, with noticeable constriction at the septa. In older macroconidia, individual cells may enlarge and develop thick walls, forming chlamydospores, also known as endochlamydospores. Cells adjacent to these endochlamydospores often become empty and rupture. Free endochlamydospores are biconvex lens-shaped, often with remnants of ruptured cells, which is characteristic. Microconidia are lateral or terminal, short and club-shaped. Spiral hyphae may occasionally be present.
8.5.2 Subculture onto Dermatophyte Test Medium (DTM). All five dermatophytic fungi mentioned above will cause the DTM medium to change color from yellow to red.
9 Result Reporting
A positive result shall be reported for specimens conforming to all the above-mentioned test results. A negative result shall be reported for specimens not conforming.
