This document provides information about Sporotrichosis, including its definition, etiology, clinical features, diagnosis, and treatment. It is caused by the dimorphic fungus Sporothrix schenckii, which can cause subcutaneous nodules and ulceration. Diagnosis involves microscopic examination, culture, histology, and serology to demonstrate the presence of the fungus. Treatment typically involves oral antifungal medication such as itraconazole or potassium iodide for at least 4-6 weeks after symptoms resolve.

1. Name: Purshotam Kumar Sah Kanu
Roll No.: MB 1318/075
Level: M.Sc Microbiology (3rd Sem)
Central Department of Microbiology
Tribhuvan University, Kirtipur
Kathmandu, Nepal
MB 609 Systemic and Diagnostic
Mycology

2. Definition
•Subcutaneous fungal
infection, characterized
by mobile tender
nodules forming ulcer,
may be followed by
chronic sporotrichosis
in the form of multiple
hard nodules along
lymphatic channels.

3. SPOROTRICHOSIS
 Sporotrichosis is a chronic infection characterised by nodular
lesions and ulcers in the lymph nodes, skin or subcutaneous
tissues and occasionally in the internal organs.
 The localised lesions are usually found on the hands, arms or
legs.
 It is a chronic infection often limited to the cutaneous and
subcutaneous tissues, and may rarely become disseminated.
 It is caused by a dimorphic fungus Sporothrix schenckii which
lives as a saprophyte in the external milieu.
 It has been isolated from the soil, the plants and the wood.

4.  S.schenckii is a dimorphic fungus found all over the world and
occurs mainly in Central and SouthAmerica, parts of the
USA andAfrica andAustralia.
 It is rare in Europe.
 The fungus is found in soil, decaying woods, thorns, and on
infected animals including rats, cats, dogs, and horses.

5. Etiology:
 Causative Agent: It is caused by Sporothrix
schenckii,a saprophyte in nature.
 Sporothrix schenckii(A dimorphic
fungus).
 S.schenckii is a complex of several clinico-
epidemiologically important species.These
include S.albicans, S.brasiliensis (in Brazil), S.
mexicana (in Mexico), S.globosa (in UK,
Spain, Italy, China, Japan, USA, and India),
and S.schenckii sensu stricto (“in the strict
sense”)

6. Morphology:
 S.schenckii is a dimorphic fungus.
 In nature and in culture at 25 to 30°C, it develops as a
mould with very thin (1-2 mm) septate hyphae; spore-
bearing hyphae carry clusters of oval spores.
 The yeast phase is formed in tissue and in culture at 37°C,
and is composed of spherical or cigar-shaped cells (1-3 × 3-
10 mm).

7. Cont..
 In infected tissues, the fungus is seen as cigar shaped yeast
cells, without mycelia.
 Sometimes ‘asteroid bodies’ are seen in the lesion,
composed of a central fungus cell with eosinophilic material
radiating from it.
 Spore is the infective stage of the fungus.
 It causes infection primarily on the hand or the forearm
through direct contact of the skin by spores.
 Typically, infection is introduced in skin through a
penetration of thorn.

8. Cont..
 At the site of thorn injury, it causes a local pustule or ulcer
with the nodules along the draining lymphatics.
 Frequently, the regional lymph nodes draining the ulcer
enlarge, suppurate, and ulcerate.
 The primary lesion may remain localized or in the
immunocompromised individuals may disseminate to involve
the bones, joints, lung, and rarely the central nervous
system.
 In infected tissue, the yeast appears as round, oval, or cigar
shaped cells with irregular borders.

9. Cont..
 Periodic acid-Schiff (PAS) or Gomori‟s methenamine silver
(GMS) stain is useful to demonstrate these structures in the
stained smears.
 The fungus on SDA at 25°C produces black and shiny
colonies, which become wrinkled and foggy during course of
time.
 The mold contains hyphae bearing flower-like structures of
small conidia on delicate sterigmata.
 Laboratory diagnosis of sporotrichosis is made by
demonstration of asteroid bodies in pus of the abscesses.

10. Cont..
 Asteroid bodies consist of a central basophilic budding yeast
cell with eosinophilic material, which radiates from the
center.
FIG. 72-4. Sclerotic bodies.

11. Pathogenesis
• The fungus is a saprophyte found widely on plants, thorns
and timber.
 Infection is acquired through thorn pricks or other minor
injuries. Rare instances of transmission from patients and
infected horses and rats have been recorded.
 Sporotrichosis most frequently presents as a nodular,
ulcerating disease of the skin and subcutaneous tissues, with
spread along local lymphatic channels but seldom extends
beyond the regional lymph nodes.
 Most cases occur in the upper limb.

12. Cont…
 Human infections are mainly associated with S.schenckii sensu
stricto, S.brasiliensis and S.globosa.
 S.brasiliensis and S.schenckii are the most virulent species in
terms of mortality, tissue burden, and tissue damage with S.
globosa being just next in virulence.
 Occupations such as agriculture, gardening, foresting,
nursery and veterinary work are particularly at risk.
 Human infections have also been associated with insect bites,
fish handling and bites of birds, cats, dogs, horses, reptiles.
 Occurrence of infection depends upon presence of abundant
fungus in the environment and not portal of entry, age,
gender, and race.

13.  The disease frequently occurs in young individuals between
20 and 50 years of age.
 Only up to 60% of patients would recall history of prior
injury.
 The incubation period varies from a few days to a few
months (average 3 weeks).

14. Clinical Features
 The primary lesion is a small, indurated, progressively
enlarging papulonodule, developing at inoculation site.
 It may ulcerate (sporotrichotic chancre) with or without
transient satellite adenopathy.
 Clinical variants include
a. lymphocutaneous sporotrichosis,
b. fixed cutaneous sporotrichosis, or
c. extracutaneous or systemic disease.

15.  Extracutaneous dissemination may be in the form of
osteoarticular, pulmonary, ocular or central nervous
system disease; osteoarticular being the most common.
 Multifocal or disseminated cutaneous sporotrichosis
means three or more lesions involving two different anatomical
sites.
 Lymphocutaneous sporotrichosis is the classic form (Fig. 1)
accounting for 70–80% of the cases.
 A string of nodules may appear along the draining lymphatics.
 Secondary lesions present as erythematous papules, nodules or
plaques with smooth or verrucous surface.
 Some may soften, ulcerate and produce seropurulent discharge.
 They are mostly asymptomatic or mildly pruritic or painful.

16.  In fixed cutaneous sporotrichosis, the infection remains
confined to a single skin lesion at inoculation site (Fig. 2).
 Lesional morphology may be noduloulcerative or crusted
erythematous to verrucous plaque (Fig. 3).
 Rare forms include those resembling keratoacanthoma, facial
cellulitis, pyoderma gangrenosum, prurigo nodularis, soft tissue
sarcoma, basal cell carcinoma, erysipeloid orrosacea.
 Involvement of exposed parts like extremities is common.
 This form is associated with high host resistance and better
therapeutic outcome.
 It has been suggested that fixed cutaneous disease is caused by
strains growing best at 35°C, whereas lymphocutaneous and
extracutaneous disease is by strains that grow both at 35°C and
37°C.

17.  The extracutaneous (systemic) form is a result of
hematogenous spread in immunosuppressed patients.
 Manifestations include sinusitis, osteoarticular disease,
meningitis and endophthalmitis.
 Pulmonary disease is rare and may manifest as cough, low-
grade fever, weight loss, mediastinal lymphadenopathy and
cavitation.
 Extracutaneous sporotrichosis has been reported as an
emerging mycosis in human immunodeficiency virus (HIV)
seropositive individuals in recent years.

18. Figs 1A and B: Cutaneous sporotrichosis. Lymphocutaneous sportrichosis
involving upper limb; (A) Lower limb; (B) A string of noduloulcerative
lesions appear along the lymphatics proximal to the initial inoculation
(injury) site
A B

19. Figs 2A to D: Cutaneous sporotrichosis: Fixed cutaneous sporotrichosis.A large
indurated granulomatous plaque over forehead (A), Nasal bridge (B), Right cheek (C),
Nose tip (D). Small papular lesions at the periphery of primary lesion are suggestive of
destabilization of the lesion and results from trauma of surgery or manipulation of
lesion

20. Figs 3A and B: Cutaneous sporotrichosis. (A) Ulcerative variant of cutaneous
sportrichosis presenting as painless, nonhealing ulcers involving left
mandibular area (B) Noduloulcerative lesions involving ear pinna and
retroauricular area as a result of inoculation of Sporothrix schenckii following
ear prick

21. Box 1: Differential diagnosis for cutaneous
sporotrichosis
 • Cutaneous tuberculosis
 • Cutaneous leishmaniasis
 • Nocardiosis
 • Chromoblastomycosis
 • Paracoccidioidomycosis
 • Atypical mycobacteriosis

22. Laboratory Diagnosis
Diagnosis is made by culture as frequently the fungus may not be
demonstrable in pus or tissues.
Collection of Infected Material:
 Pus should be aspirated from unruptured nodules.
 Swabs, scrapings or biopsies of ulcerated lesions should be
collected in a sterile container.
A. Micrscopic Examination:
Direct microscopy is of little.
 Fine-needle aspiration cytology may show epithelioid cell
granuloma, asteroid bodies and/or yeast cells and cigarshaped
bodies [periodic acid Schiff (PAS) or Grocott‟s methanamine silver
(GMS) stains].
 The sensitivity/specificity of direct microscopic examination
remains under evaluated as most studies consider it unhelpful due
to paucity of fungal cells.

23.  B. Culture:
 Culture of S.schenckii from pus or biopsy specimen on
Sabouraud dextrose agar (SDA) or brain heart infusion agar
is diagnostic.
 Growth is generally obtained in 3–5 days or within 2 weeks.
 Cultures on SDA at 25°C showcharacteristic colonies which
are initially cream-colored turning brown/black after a few
weeks (Fig. 4).

24. Cont…
 Lactophenol cotton blue (LCB) mounts demonstrate delicate
branching septate hyphae with slender, short, conidiophores and
surrounding pyriform conidia, in a flower-like arrangement.
 Individual thick-walled, dark brown conidia can also be seen
attached directly to the hypha in a dense sleeve-like pattern (Fig.
5).
 The fungus exhibits temperature dimorphism.
 It is a mold at room temperature (26°C) and yeast in host tissues
(37°C).
 Demonstration of this dimorphism helps to confirm the identity of
S.schenckii.
 The fungus also produces melanin which may protect it against
phagocytosis and extracellular proteinases.

25. Figs 4A and B: Cutaneous sporotrichosis: Sporothrix schenckii
colony on Sabouraud’s glucose agar. Initial cream color (A)
turns brown black (B) as it matures
A B

26. Figs 5A to C: Cutaneous sporotrichosis:
Sporothrix schenckii in delicate branching,
mold form with pyriform conidia in (A)
characteristic flower-like arrangement or;
(B) dense sleeve-like pattern. Smears taken
from culture in Sabouraud glucose agar at
25oC (Stain: Lactophenol cotton blue × 40);
(C) yeast form from culture in brain heart
infusion broth at 37oC (Gram stain × 40)
A B
C

27. C. Histology:
 Histological features are usually nonspecific.
 They may vary from acute on chronic inflammation with
characteristic zonation to chronic epithelioid cell granuloma
 with foreign body or Langhans giant cells.
 There may also be nonspecific chronic granulomatous
inflammatory cell infiltration (Fig. 6).
 Fixed cutaneous sporotrichosis shows central ulceration,
hyperkeratosis at the edge, along with acanthosis and
epidermal hyperplasia.

28.  Neutrophilic abscesses may be seen.
 A dense cellular infiltrate comprising lymphocytes plasma
cells, and variable number of epithelioid histiocytes, giant
cells and eosinophils (mixed granulomatous cellular
infiltrate) in upper and mid dermis may be seen.
 Occasionally, asteroid, cigar-shaped (1–2 . 4–5 μm), oval to
round or single budding forms of the yeast can be visualized.

29.  Asteroid bodies are seen in 40–85% of cases of chronic
sporotrichosis.
 They are more frequent in lymphocutaneous variety.
 These are extracellular, 15–35 μm in diameter, bodies
localized within abscesses.
 They are several fungal organisms enveloped by eosinophilic
material radiating centrifugally in a sunburst fashion
(Splendore-Hoeppli phenomenon).
 These are not pathognomonic; asteroid bodies can also be
seen in other granulomatous and infectious diseases.

30.  Histologically, nodules of lymphocutaneous sporotrichosis
are organized into 3 concentric zones: the central necrotic
zone containing amorphous debris and polymorphonuclear
leukocytes (zone of chronic suppuration), the middle
tuberculoid zone is composed of epithelioid cells, giant cells
(predominantly Langhans type) and the outer zone
comprising numerous plasma cells, lymphocytes and
fibroblasts with prominent capillary hyperplasia and
proliferation (syphiloid zone).
 In older lesions, this zonation may be indistinct.
 The fungal elements may vary from globose budding cells to
cigar-shaped cells.

31. D. Serology:
 A latex agglutination test is of value for the diagnosis of the
extracutaneous forms of sporotrichosis.
 The test has poor prognostic value since titres change little after
successful therapy.
E. Intradermal Test:
 A skin test with sporotrichin antigen is„positive in almost all
patients with cutaneous sporotrichosis.
 It is performed by using sporotrichin or peptiderhamnomannan
(PRM) antigens to detect delayed hypersensitivity.
 The diagnostic value is ambiguous as it is often positive in healthy
people in endemic areas and may be negative in disseminated
sporotrichosis.

32. F.Animal Inoculation:
 Rats are highly susceptible and can be infected by
intraperitoneal or intratesticular inoculation.

33. Figs 6A to D: Cutaneous sporotrichosis: Histopathology - neutrophilic abscesses in the
dermis with lymphoplasmacytic, epitheloid cell infiltrate. (A) Acute on chronic
inflammation with characteristic central zone of chronic suppuration, middle
tuberculoid inflammation zone comprising epitheloid and Langhans’ giant cells and
outer syphiloid zone of lymphoplasmacytic cells, fibroblasts and capillary
proliferation; (B) Chronic inflammatory cell infiltrate with foreign body giant cell
reaction; (C) Epitheloid cell granuloma with a Langhans’ giant cell (D) (H & E, × 40)
A B
C
D

34. Treatment
 Fixed cutaneous form is associated with high host resistance
and minimal lesions may subside spontaneously.
 There are no well-controlled studies of treatment protocols.
 The treatment schedules recommended by Infectious
Diseases Society ofAmerica are empirical (Table 3).
 Nevertheless, treatment needs to be continued for at least 4–
6 weeks after complete clinical remission.
 Oral administration of SSKI remains the treatment of choice
for uncomplicated cutaneous sporotrichosis due to low cost
and consistent efficacy.

35.  Its mechanism of action remains unexplained; it may inhibit
granuloma formation through immunologic as well as
nonimmunologic mechanisms, exposing the fungus to host
defences.
 The starting dose is 5 drops three times a day, subsequently
increased daily by 5 drops up to a maximum of 30–40 drops thrice
a day till complete regression.
 Development of metallic taste signifies threshold for maximum
tolerable dose.
 The response is evident within 2 weeks with healing in 4–32
weeks.
 Adverse effects include metallic taste, flu-like syndrome, excessive
lacrimation, gastrointestinal upset, parotid swelling, acneiform or
papulopustular eruption, lesional pain and inflammation.

36.  Rare side effects include hypothyroidism or hyperthyroidism,
iododerma, cardiac irritability, vasculitis, pustular psoriasis,
pulmonary edema, urticaria and angioedema, myalgia,
lymphadenopathy and eosinophilia.
 Itraconazole is effective and well tolerated.
 Despite its high cost, it is currently the drug of choice with success
rates of 90–100% (60–80% for osteoarticular sporotrichosis).
 Recommended dose is 200–400 mg/day for 3–6 months (1 year
for osteoarticular and disseminated forms).
 It has good in vitro activity against S.brasiliensis; higher minimum
inhibitory concentrations are recorded against other species.

37.  Terbinafine, 500–1,000 mg/day, alone or in combination with
SSKI, has been used effectively for 4–37 weeks.
 Though less effective than itraconazole, fluconazole, 400–600
mg/day, alone or in combination with SSKI, is other useful
therapeutic option in patients intolerant to itraconazole.
 Amphotericin B (dose 0.5–1.0 mg/kg/day) is safe during
pregnancy but due to its toxicity, it is reserved as a drug of choice
for treating disseminated cutaneous, pulmonary or HIV-associated
sporotrichosis.
 There is paucity of data for the use of posaconazole or
ravuconazole; the former has shown good activity against all the
species; the latter has activity limited only against S.brasiliensis.

38.  Echinocandins have no activity and voriconazole is not
recommended for treatment of sporotrichosis.
 The daily application of local heat (42–43°C) for weeks using
wet heat or handheld pocket warmer or far infrared heater is
recommended particularly in pregnant women.
 As there is no risk of dissemination of sporotrichosis or to
the fetus, treatment is best delayed in pregnant patients.

39. Key Points
 • Most cases of sporotrichosis remain limited to skin/ subcutis and
systemic dissemination is seen more often in immunosuppressed
 • Lymphocutaneous sporotrichosis is the commonest form and can
be diagnosed readily
 • Spontaneous resolution is rare and treatment in all cases is
imperative
 • Uncomplicated cutaneous disease is readily treated with SSKI or
itraconazole while disseminated forms are difficult to treat and
need more aggressive therapy with amphotericin B
 • Patients with immunosuppression may require suppressive
therapy for life
 • Patient education for minimizing vocational exposure to source
of infection, prolonged and regular treatment, and adverse effects
of therapy is important.