Investigations
1st investigations to order
skin lesion fungal culture
Test
Skin lesion material may be swabbed or aspirated or a skin lesion may be biopsied. Cultures become positive within 8 days in 89% of cases and within 4 weeks in the remaining 11% of cases; thus the microbiology laboratory should be notified to keep the agar plates for 1 month.[11]
Result
positive culture on Sabouraud's agar
skin lesion histopathology (Gomori methenamine silver, periodic acid-Schiff staining)
Test
In patients without HIV, yeast forms may not be seen and multiple tissue sections need to be examined due to the small numbers of microorganisms; by contrast, in patients with HIV, identification of Sporothrix on tissue sections may be easier owing to the larger number of infecting fungal organisms.
A mixed pyogranulomatous inflammatory reaction is common with epidermal hyperplasia, hyperkeratosis, and papillomatous acanthosis. Such inflammatory changes may be less pronounced in patients with HIV. The asteroid body - extracellular eosinophilic material surrounding yeast cells (known as the Splendore-Hoeppli phenomenon) may be seen in 20% to 40% of cases.
Result
3- to 5-micrometre cigar- or oval-shaped yeast forms of Sporothrix schenckii may be seen
FBC
Test
Result
normal
erythrocyte sedimentation rate
Test
Result
elevated in osteoarticular and pulmonary sporotrichosis
joint x-ray
Test
For evaluation of osteoarticular disease.
Result
non-specific findings of osteoporosis, periosteal reaction, articular surface erosions, and soft tissue swelling may be seen
fungal culture of arthrocentesis synovial fluid
Test
Repeated synovial fluid cultures are typically necessary for diagnosis of osteoarticular disease.
Result
positive culture on Sabouraud's agar
sputum or bronchoalveolar lavage (BAL) fungal culture
Test
For evaluation of pulmonary disease.
Result
sputum or BAL cultures may be positive
lumbar puncture for cerebrospinal fluid analysis
Test
Results common in meningeal sporotrichosis.
Result
elevated protein, low glucose, lymphocytic predominance
cerebrospinal fluid (CSF) fungal culture
Test
Repeated large-volume CSF fungal cultures are typically necessary for diagnosis as the sensitivity of CSF culture for Sporothrix in meningeal disease is low.
Result
CSF culture may be positive on Sabouraud's agar
fungal blood culture
Test
Rarely positive in disseminated sporotrichosis cases.
Result
positive or negative
Investigations to consider
synovial tissue biopsy for fungal culture
Test
Synovial tissue culture has a higher yield compared with synovial fluid culture for Sporothrix in osteoarticular disease.
Result
positive culture on Sabouraud's agar
synovial tissue histopathology (Gomori methenamine silver, periodic acid-Schiff staining)
Test
Synovial tissue histopathological examination may reveal Sporothrix yeast forms in osteoarticular disease.
Result
3- to 5-micrometre cigar- or oval-shaped yeast forms of S schenckii
bronchial biopsy fungal culture
Test
Bronchial biopsy cultures have higher sensitivity than sputum or bronchoalveolar lavage cultures. Used in pulmonary disease.
Result
positive culture on Sabouraud's agar
bronchial biopsy histopathology
Test
In pulmonary disease.
Result
Sporothrix yeast forms
CXR
Test
Result
upper lobe cavitary lesions; hilar lymphadenopathy and pleural effusions may be seen
CT of chest
Test
Result
upper lobe cavitary lesions; hilar lymphadenopathy and pleural effusions may be seen
serum itraconazole levels
Test
Result
>1 microgram/mL are desirable in patients with osteoarticular, pulmonary, meningeal, and disseminated sporotrichosis and unresponsive cutaneous sporotrichosis
serum urea
Test
Renal function should be monitored during amphotericin B treatment.
Result
normal; may rise due to amphotericin B therapy
serum creatinine
Test
Renal function should be monitored during amphotericin B treatment.
Result
normal; may rise due to amphotericin B therapy
LFTs
Test
LFTs should be monitored in those on terbinafine.
Result
normal; may rise due to terbinafine therapy
Emerging tests
immunohistochemical staining
Test
Reported to have higher sensitivity than routine histopathology methods. Neither commercially available nor standardised.
Result
cigar- or oval-shaped yeast forms of S schenckii
polymerase chain reaction (PCR)
Test
Reported to have high sensitivity and specificity in diagnosis of cutaneous sporotrichosis in one study with 12 patients; no literature exists regarding the role of PCR for diagnosis of extracutaneous manifestations of sporotrichosis.
The 18S ribosomal RNA was the reported target gene for the PCR reaction.[33]
Result
positive
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