Dermatophytosis laboratory findings: Difference between revisions

Jump to navigation Jump to search
VisualWikitext
No edit summary
m (Bot: Removing from Primary care)
 
(10 intermediate revisions by 4 users not shown)
Line 1: Line 1:
== Overview ==
Laboratory findings consistent with the [[diagnosis]] of dermatophytosis include [[KOH test|KOH preparation]] showing refractile, long, smooth, undulating, branching, and [[septate]] [[Hyphae|hyphal]] filaments with or without [[Arthroconidia|arthroconidiospores]]; [[Culture medium|culture and sensitivity]] may yield the diagnosis but it takes 7-14 days for colony growth; [[H&E stain|hemotoxylin and eosin]] stain may be used in diagnosis of [[Majocchi's granuloma]] in which [[KOH test|KOH examination]] of scale may be false negative. [[Polymerase chain reaction]] ([[Polymerase chain reaction|PCR]]) testing may be used to identify various dermatophytic [[Infection|infections]] and even help in evaluating [[Drug resistance|drug resistances]] of different species of dermatophytes.
__NOTOC__
__NOTOC__
{{Dermatophytosis}}
{{Dermatophytosis}}


=== Laboratory investigations ===
== Laboratory Findings ==
For a laboratory to provide optimal results, quantity and quality of material examined is critical. Scraping should be collected from active margin and transported in a presterilized black chart paper which keeps the specimen dry thus, preventing over growth of bacteria contaminants. Following are the various laboratory tests that can be used for confirming a diagnosis of dermatophytosis.
# Direct microscopic examination:[20] Treatment of skin specimen with 10–20% potassium hydroxide (KOH) is a quick and inexpensive bedside tool to provide evidence of dermatophytic infection. Positive scrapings are characterized by presence of refractile, long, smooth, undulating, branching, and septate hyphal filaments with or without arthroconidiospores. False negative results are seen in 15% cases. Fluorescent staining with optical brighteners (diaminostilbene) is the most sensitive method to microscopically detect fungi in skin scales as well as in specimens from nails and hair.[21] These substances bind to chitin, the main cell wall component of fungi
# Culture and antifungal sensitivity:[22] Sabouraud dextrose agar (SDA, 4% peptone, 1% glucose, agar, water) is the most commonly used isolation media for dermatophytosis and serves as the medium on which most morphologic descriptions are based. Development of colony takes 7–14 days. Modified SDA, with addition of gentamicin, chloramphenicol and cycloheximide is more selective for dermatophytes as chroramphenicol inhibits the growth of saprophytic fungus. Dermatophyte test medium is an alternative to isolation media that contain pH indicator phenol red. It is incubated at room temperature for 5–14 days. Dermatophytes utilize the protein resulting in excess ammonium ion and alkaline environment which turn the medium from yellow to bright red.


==== Antifungal susceptibility testing ====
=== Specimen collection ===
# Microdilution method: The broth microdilution assay for antifungal susceptibility testing of dermatophytes has been previously developed as a modification of the Clinical and Laboratory Standards Institute M38-A2 standard method. The final concentrations of terbinafine and itraconazole used is 0.06–32.0 μg/ml and for fluconazole, 0.13–64.0 μg/ml.[23] A standardized inoculum is prepared by counting the microconidia microscopically. Cultures are grown on SDA slants for 7 days at 35°C to produce conidia. Sterile normal saline (85%) is added to the agar slant, and the cultures are gently swabbed with a cotton-tipped applicator to dislodge the conidia from the hyphal mat. The suspension is transferred to a sterile centrifuge tube, and the volume is adjusted to 5 ml with sterile normal saline. The resulting suspension is counted on a hemacytometer and is diluted in RPMI 1640 medium to the desired concentration. Microdilution plates are set up in accordance with the reference method. The microdilution plates are incubated at 35°C and read visually after 4 days of incubation. The minimum inhibitory concentration is defined as the concentration at which the growth of the organism will be inhibited by 80% compared with the growth in the control well
Scrapings should be collected from active margin and transported in a presterilized black chart paper which keeps the specimen dry thus, preventing over growth of [[Bacteria|bacterial]] [[contaminants]]. Tinea capitis may be diagnosed via [[dermoscopy]].
# Minimum fungicidal concentration (MFC) determination: For determination of the MFC, 100-μl aliquots are removed from the assay wells showing no visible growth at the end of incubation and streaked onto SDA plates. The plates are incubated at 30°C for 7 days. The MFC is defined as the lowest drug concentration at which no visible fungal growth or colonies developed
* 3.  Dermatophyte identification: This can be based on colony characteristics, microscopic morphology, and physiologic tests. Dermatophytes can be distinguished based upon their morphology of the macroconidia. Few physiological tests are available which help in confirmation of certain species. In addition, special amino acid and vitamin requirements can differentiate ''Trichohyton'' species from others. Ability to hydrolyse urea differentiates ''T. mentagrophytes'' (urease positive) from ''T. rubrum'' (urease negative).


=== Histopathology ===
=== Direct microscopic examination ===
Histology may be used in diagnosis of Majocchi's granuloma in which KOH examination of scale on the surface may more often be negative. When present, hyphae may be appreciated in stratum corneum on hematoxylin and eosin staining. Special stains most commonly used are periodic acid-Schiff and Gomori methanamine silver which helps to highlight hyphae.
* Treatment of [[skin]] specimen with 10–20 percent [[potassium hydroxide]] (KOH) is a convenient bedside tool to provide evidence of dermatophytic [[infection]].<ref name="pmid22474120">{{cite journal |vauthors=Kelly BP |title=Superficial fungal infections |journal=Pediatr Rev |volume=33 |issue=4 |pages=e22–37 |year=2012 |pmid=22474120 |doi=10.1542/pir.33-4-e22 |url=}}</ref>
* Positive scrapings are characterized by:
** Refractile, long, smooth, undulating, branching, and [[septate]] [[Hyphae|hyphal]] filaments with or without [[Arthroconidia|arthroconidiospores]].
* Fluorescent staining of the [[cell wall]] is the most sensitive method to microscopically detect fungi in skin [[Scaling skin|scales]] as well as in specimens from nails and hair.
 
=== Culture and antifungal sensitivity ===
* [[Agar|Sabouraud dextrose agar]] (SDA, 4% peptone, 1% glucose, agar, water) is the most commonly used isolation [[Culture media|media]] for dermatophytosis and serves as the [[Growth medium|medium]] for fungal growth.<ref name="pmid16479181">{{cite journal |vauthors=Ecemis T, Degerli K, Aktas E, Teker A, Ozbakkaloglu B |title=The necessity of culture for the diagnosis of tinea pedis |journal=Am. J. Med. Sci. |volume=331 |issue=2 |pages=88–90 |year=2006 |pmid=16479181 |doi= |url=}}</ref><ref name="pmid1379146">{{cite journal |vauthors=Rezabek GH, Friedman AD |title=Superficial fungal infections of the skin. Diagnosis and current treatment recommendations |journal=Drugs |volume=43 |issue=5 |pages=674–82 |year=1992 |pmid=1379146 |doi= |url=}}</ref><ref name="pmid22474120" />
* The development of colony takes 7–14 days.
* Modified [[Culture media|culturing techniques]], with addition of [[gentamicin]], [[chloramphenicol]] and [[cycloheximide]] is more selective for dermatophytes, as [[chloramphenicol]] inhibits the growth of saprophytic [[fungus]].
* Dermatophyte test [[Culture medium|medium]] is an alternative to isolation [[Culture media|media]] that contain pH indicator [[phenol red]]. It is [[Incubation period|incubated]] at room temperature for 5–14 days.
* Dermatophytes utilize the [[protein]] resulting in excess ammonium ion and [[alkaline]] environment which turn the medium from yellow to bright red.
 
=== Hematoxylin and eosin staining ===
* Histology may be used in diagnosis of [[Majocchi's granuloma]] in which KOH examination of scale may be false negative.<ref name="pmid14744085">{{cite journal |vauthors=Al-Amiri A, Chatrath V, Bhawan J, Stefanato CM |title=The periodic acid-Schiff stain in diagnosing tinea: should it be used routinely in inflammatory skin diseases? |journal=J. Cutan. Pathol. |volume=30 |issue=10 |pages=611–5 |year=2003 |pmid=14744085 |doi= |url=}}</ref><ref name="pmid21987154">{{cite journal |vauthors=Bressan AL, Silva RS, Fonseca JC, Alves Mde F |title=Majocchi's granuloma |journal=An Bras Dermatol |volume=86 |issue=4 |pages=797–8 |year=2011 |pmid=21987154 |doi= |url=}}</ref><ref name="pmid16804445">{{cite journal |vauthors=Feng WW, Chen HC, Chen HC |title=Majocchi's granuloma in a 3-year-old boy |journal=Pediatr. Infect. Dis. J. |volume=25 |issue=7 |pages=658–9 |year=2006 |pmid=16804445 |doi=10.1097/01.inf.0000224312.87417.fc |url=}}</ref>
* [[Hyphae]] may be visualized in [[stratum corneum]] on hematoxylin and eosin staining.  
* Special stains most commonly used are:
** [[Periodic acid-Schiff stain|Periodic acid-Schiff]]
** Gomori methanamine silver  


=== Dermoscopy ===
=== Dermoscopy ===
The comma hairs, which are slightly curved, fractured hair shafts, and corkscrew hair shave been described as the dermoscopic marker of tinea capitis. Broken and dystrophic hairs are also seen. However, in tinea corporis, the involvement of vellus hair as seen on dermoscopy is an indicator of systemic therapy.[24]
* [[Tinea capitis]] may show:<ref name="pmid25471133">{{cite journal |vauthors=Lacarrubba F, Verzì AE, Micali G |title=Newly described features resulting from high-magnification dermoscopy of tinea capitis |journal=JAMA Dermatol |volume=151 |issue=3 |pages=308–10 |year=2015 |pmid=25471133 |doi=10.1001/jamadermatol.2014.3313 |url=}}</ref><ref name="pmid25728878">{{cite journal |vauthors=Arrazola-Guerrero J, Isa-Isa R, Torres-Guerrero E, Arenas R |title=[Tinea capitis. Dermoscopic findings in 37 patients] |language=Spanish; Castilian |journal=Rev Iberoam Micol |volume=32 |issue=4 |pages=242–6 |year=2015 |pmid=25728878 |doi=10.1016/j.riam.2014.09.002 |url=}}</ref>
** Comma hairs, which are slightly curved, fractured hair shafts
** Corkscrew hair
** Broken hair
* [[Tinea corporis]] may show:
** Involvement of [[vellus hair]]


=== Polymerase chain reaction and nucleic acid sequence based amplification ===
=== Polymerase chain reaction and nucleic acid sequence based amplification ===
These tests not only help in the rapid and early diagnosis of infection but also help in determining drug resistance,[25] and include:
These tests not only help in the rapid and early [[diagnosis]] of infection but also help in determining [[drug resistance]], and include:<ref name="pmid23287391">{{cite journal |vauthors=Miyajima Y, Satoh K, Uchida T, Yamada T, Abe M, Watanabe S, Makimura M, Makimura K |title=Rapid real-time diagnostic PCR for Trichophyton rubrum and Trichophyton mentagrophytes in patients with tinea unguium and tinea pedis using specific fluorescent probes |journal=J. Dermatol. Sci. |volume=69 |issue=3 |pages=229–35 |year=2013 |pmid=23287391 |doi=10.1016/j.jdermsci.2012.11.589 |url=}}</ref><ref name="pmid27057486">{{cite journal |vauthors=Sahoo AK, Mahajan R |title=Management of tinea corporis, tinea cruris, and tinea pedis: A comprehensive review |journal=Indian Dermatol Online J |volume=7 |issue=2 |pages=77–86 |year=2016 |pmid=27057486 |pmc=4804599 |doi=10.4103/2229-5178.178099 |url=}}</ref><ref name="pmid25418736">{{cite journal |vauthors=Spiliopoulou A, Bartzavali C, Jelastopulu E, Anastassiou ED, Christofidou M |title=Evaluation of a commercial PCR test for the diagnosis of dermatophyte nail infections |journal=J. Med. Microbiol. |volume=64 |issue=Pt 1 |pages=25–31 |year=2015 |pmid=25418736 |doi=10.1099/jmm.0.079962-0 |url=}}</ref>
* Uniplex PCR for direct dermatophyte detection in clinical samples: A PCR for the direct detection of dermatophytes in skin scales is available as in-house PCR-ELISA assay which separately identifies numerous dermatophyte species. In a pilot study, the sensitivity and specificity of the test compared to cultures was 80.1% and 80.6%
* '''Uniplex [[Polymerase chain reaction|PCR]]''' for direct dermatophyte detection in clinical samples:  
* Multiplex PCR for fungal detection in dermatophytes: Commercially available multiplex PCR tests enable simultaneous amplification of 21 dermatomycotic pathogens with subsequent DNA detection by means of agarose gel electrophoresis.
** A PCR for the direct detection of dermatophytes in [[Scaling skin|skin scales]] may be used for diagnosis. PCR-ELISA assay separately identifies numerous dermatophyte species.
* '''Multiplex [[Polymerase chain reaction|PCR]]''' for [[Fungus|fungal]] detection in dermatophytes:  
** Commercially available multiplex [[PCR]] tests enable simultaneous amplification of 21 dermatomycotic [[pathogens]] with subsequent [[DNA]] detection by means of [[agarose gel]] [[electrophoresis]].
==References==
==References==
{{Reflist|2}}
{{Reflist|2}}
{{WikiDoc Help Menu}}
{{WikiDoc Sources}}
[[Category:Disease]]
[[Category:Disease]]
[[Category:Dermatology]]
[[Category:Dermatology]]
[[Category:Infectious disease]]
[[Category:Primary care]]
[[Category:Needs content]]
[[Category:Needs content]]
{{WikiDoc Help Menu}}
{{WikiDoc Sources}}

Latest revision as of 21:18, 29 July 2020

Overview

Laboratory findings consistent with the diagnosis of dermatophytosis include KOH preparation showing refractile, long, smooth, undulating, branching, and septate hyphal filaments with or without arthroconidiospores; culture and sensitivity may yield the diagnosis but it takes 7-14 days for colony growth; hemotoxylin and eosin stain may be used in diagnosis of Majocchi's granuloma in which KOH examination of scale may be false negative. Polymerase chain reaction (PCR) testing may be used to identify various dermatophytic infections and even help in evaluating drug resistances of different species of dermatophytes.

Dermatophytosis Microchapters

Home

Patient Information

Overview

Historical Perspective

Classification

Pathophysiology

Causes

Differentiating Dermatophytosis from other Diseases

Epidemiology and Demographics

Risk Factors

Screening

Natural History, Complications and Prognosis

Diagnosis

History and Symptoms

Physical Examination

Laboratory Findings

Electrocardiographic Findings

X-Ray Findings

CT scan Findings

MRI Findings

Ultrasound Findings

Other Imaging Findings

Other Diagnostic Studies

Treatment

Medical Therapy

Surgery

Primary Prevention

Secondary Prevention

Cost-Effectiveness of Therapy

Future or Investigational Therapies

Case Studies

Case #1

Dermatophytosis laboratory findings On the Web

Most recent articles

Most cited articles

Review articles

CME Programs

Powerpoint slides

Images

American Roentgen Ray Society Images of Dermatophytosis laboratory findings

All Images
X-rays
Echo & Ultrasound
CT Images
MRI

Ongoing Trials at Clinical Trials.gov

US National Guidelines Clearinghouse

NICE Guidance

FDA onDermatophytosis laboratory findings

CDC on Dermatophytosis laboratory findings

Dermatophytosis laboratory findings in the news

Blogs on Dermatophytosis laboratory findings

Directions to Hospitals Treating Dermatophytosis here

Risk calculators and risk factors for Dermatophytosis laboratory findings

Laboratory Findings

Specimen collection

Scrapings should be collected from active margin and transported in a presterilized black chart paper which keeps the specimen dry thus, preventing over growth of bacterial contaminants. Tinea capitis may be diagnosed via dermoscopy.

Direct microscopic examination

  • Treatment of skin specimen with 10–20 percent potassium hydroxide (KOH) is a convenient bedside tool to provide evidence of dermatophytic infection.[1]
  • Positive scrapings are characterized by:
  • Fluorescent staining of the cell wall is the most sensitive method to microscopically detect fungi in skin scales as well as in specimens from nails and hair.

Culture and antifungal sensitivity

Hematoxylin and eosin staining

Dermoscopy

Polymerase chain reaction and nucleic acid sequence based amplification

These tests not only help in the rapid and early diagnosis of infection but also help in determining drug resistance, and include:[9][10][11]

  • Uniplex PCR for direct dermatophyte detection in clinical samples:
    • A PCR for the direct detection of dermatophytes in skin scales may be used for diagnosis. PCR-ELISA assay separately identifies numerous dermatophyte species.
  • Multiplex PCR for fungal detection in dermatophytes:

References

  1. ↑ 1.0 1.1 Kelly BP (2012). "Superficial fungal infections". Pediatr Rev. 33 (4): e22–37. doi:10.1542/pir.33-4-e22. PMID 22474120.
  2. ↑ Ecemis T, Degerli K, Aktas E, Teker A, Ozbakkaloglu B (2006). "The necessity of culture for the diagnosis of tinea pedis". Am. J. Med. Sci. 331 (2): 88–90. PMID 16479181.
  3. ↑ Rezabek GH, Friedman AD (1992). "Superficial fungal infections of the skin. Diagnosis and current treatment recommendations". Drugs. 43 (5): 674–82. PMID 1379146.
  4. ↑ Al-Amiri A, Chatrath V, Bhawan J, Stefanato CM (2003). "The periodic acid-Schiff stain in diagnosing tinea: should it be used routinely in inflammatory skin diseases?". J. Cutan. Pathol. 30 (10): 611–5. PMID 14744085.
  5. ↑ Bressan AL, Silva RS, Fonseca JC, Alves Mde F (2011). "Majocchi's granuloma". An Bras Dermatol. 86 (4): 797–8. PMID 21987154.
  6. ↑ Feng WW, Chen HC, Chen HC (2006). "Majocchi's granuloma in a 3-year-old boy". Pediatr. Infect. Dis. J. 25 (7): 658–9. doi:10.1097/01.inf.0000224312.87417.fc. PMID 16804445.
  7. ↑ Lacarrubba F, Verzì AE, Micali G (2015). "Newly described features resulting from high-magnification dermoscopy of tinea capitis". JAMA Dermatol. 151 (3): 308–10. doi:10.1001/jamadermatol.2014.3313. PMID 25471133.
  8. ↑ Arrazola-Guerrero J, Isa-Isa R, Torres-Guerrero E, Arenas R (2015). "[Tinea capitis. Dermoscopic findings in 37 patients]". Rev Iberoam Micol (in Spanish; Castilian). 32 (4): 242–6. doi:10.1016/j.riam.2014.09.002. PMID 25728878.
  9. ↑ Miyajima Y, Satoh K, Uchida T, Yamada T, Abe M, Watanabe S, Makimura M, Makimura K (2013). "Rapid real-time diagnostic PCR for Trichophyton rubrum and Trichophyton mentagrophytes in patients with tinea unguium and tinea pedis using specific fluorescent probes". J. Dermatol. Sci. 69 (3): 229–35. doi:10.1016/j.jdermsci.2012.11.589. PMID 23287391.
  10. ↑ Sahoo AK, Mahajan R (2016). "Management of tinea corporis, tinea cruris, and tinea pedis: A comprehensive review". Indian Dermatol Online J. 7 (2): 77–86. doi:10.4103/2229-5178.178099. PMC 4804599. PMID 27057486.
  11. ↑ Spiliopoulou A, Bartzavali C, Jelastopulu E, Anastassiou ED, Christofidou M (2015). "Evaluation of a commercial PCR test for the diagnosis of dermatophyte nail infections". J. Med. Microbiol. 64 (Pt 1): 25–31. doi:10.1099/jmm.0.079962-0. PMID 25418736.

Template:WikiDoc Sources

Retrieved from "https://www.wikidoc.org/index.php?title=Dermatophytosis_laboratory_findings&oldid=1637012"