Guidance

Mycology reference laboratory: reference and diagnostic services

The mycology reference laboratory (MRL) provides a comprehensive laboratory service for the diagnosis and management of fungal infections.

Clinical services

The mycology reference laboratory (MRL) provides advice by phone to:

  • ensure you select the most appropriate test or specimen types for patients
  • help you interpret results
  • help with the clinical management of individual cases

Reference services: identification

The following tests are available:

  • moulds (including dermatophytes)
  • unusual yeasts
  • dimorphic fungal pathogens
  • reference antifungal drug susceptibility testing of yeasts and moulds

These tests are carried out as confirmatory tests for isolates producing equivocal or unexpected results.

Serological tests

Serology of non-indigenous mycoses

The following tests are available:

  • histoplasmosis
  • coccidioidomycosis
  • blastomycosis
  • paracoccidioidomycosis

Histological examination of referred slides

Pre-stained histology slides may be submitted to the laboratory for examination. Grocott’s Silver stain is preferred.

Referred tests (charged)

Antifungal drug susceptibility testing of yeasts

The following drug susceptibility testing may be requested:

  • anidulafungin
  • amphotericin
  • caspofungin
  • clotrimazole
  • econazole
  • fluconazole
  • flucytosine
  • itraconazole
  • ketoconazole
  • micafungin
  • miconazole
  • nystatin
  • posaconazole
  • voriconazole

Antifungal drug susceptibility testing of moulds

The following tests are available:

  • amphotericin
  • caspofungin
  • clotrimazole
  • griseofulvin
  • itraconazole
  • natamycin
  • posaconazole
  • terbinafine
  • voriconazole

Other drugs may be available on request.

Antifungal drug assays

The following tests are available:

  • amphotericin (not usually necessary)
  • fluconazole (not usually necessary)
  • flucytosine
  • itraconazole
  • posaconazole
  • voriconazole

Contact the laboratory before sending samples for amphotericin or fluconazole assays.

Serological tests

The following tests are available:

  • tests for antibodies to Aspergillus, Candida, Thermophilic actinomycetes (farmer’s lung) and avian allergens
  • tests for Aspergillus (galactomannan), Candida (mannan) and Cryptococcus antigens
  • Beta 1-3 Glucan antigen detection for invasive fungal infections (this test has a very high negative predictive value)

Microscopy and culture of clinical specimens

If infection with a hazard group 3 fungus is suspected we are happy to process primary specimens.

Diagnostic polymerase chain reaction (PCR) on blood, fluids and tissue

Tests available:

  • Aspergillus-specific PCR
  • Candida-specific PCR
  • panfungal PCR

Environmental sampling

Where an associated health problem has been identified by a practitioner we may be able to undertake or advise on sampling.

Typing of common fungal pathogens

Available for some Aspergillus and Candida species in outbreak situations.

Samples: request form

Use the following request forms to submit isolates and clinical samples:

  • Y1 form - mycology identification and susceptibility testing
  • Y2 form - diagnostic mycology and assays

Samples

Package all samples securely, conforming to current postal regulations.

Cultures for identification and susceptibility testing

Follow these instructions:

  • send pure cultures on slopes rather than plates
  • for hazard group 3 pathogens, alert the laboratory in advance, by phone, that you’re submitting a culture
  • only send slopes of cultures and don’t wait for the organisms to start to sporulate

Serological tests

Follow these instructions:

  • supply 1 to 2 mL of serum (don’t send whole blood)
  • label all high risk samples
  • send samples for Beta 1-3 Glucan determination to the MRL within 48 hours

Antifungal assays

Follow these instructions:

  • contact the laboratory before submitting samples for amphotericin B or fluconazole assays, as their measurement is not often indicated
  • supply 1 to 2 mL serum taken at the appropriate times and labelled accordingly

Laboratory turnaround times

Laboratory turnaround times are from receipt of sample.

All reports are sent by first class mail. Urgent results can be telephoned to laboratories on request if you’ve provided an appropriate contact name and current telephone number on the request form.

Test type turnaround times in days (min) turnaround times in days (mean)
Aspergillus antibodies 2 3.1
Aspergillus antigen (galactomannan) 1 1.2
Avian antibodies 5 6.9
Beta 1-3 Glucan 1 3
Candida antibodies 2 3.5
Candida antigen (mannan) 1 1.5
Cryptococcus antigen 1 1
Dimorphic serology 3 6
Farmers Lung antibodies 5 6.7
Flucytosine assay 1 1.2
Itraconazole assay 3 3.1
Mould antifungal susceptibilities 5 9.6
Mould identification 1 5
PCR (Diagnostic) 3 5
Posaconazole assay 2 2.6
Voriconazole assay 1 1
Yeast antifungal susceptibilities 2 5.5
Yeast identification 2 5

Guidelines for antifungal drug monitoring

Oral flucytosine pre-dose and 2 hours post-dose
IV flucytosine pre-dose and 30 minutes post-dose
Oral or IV itraconazole pre-dose after 7 days
Oral posaconazole pre-dose after 5 days
Oral voriconazole pre-dose after 3 to 5 days
IV voriconazole pre-dose after 3 to 5 days
Amphotericin 1 to 2 hours post-dose
Oral fluconazole 2 hours post-dose
IV fluconazole 30 minutes post-dose

Please clearly label all high risk samples.

Assay results: interpretation

Flucytosine

Serum samples should be taken just before a dose of flucytosine, and 2 hours after an oral dose or 30 minutes after an intravenous dose.

The dose and interval should be adjusted in order to produce peak serum concentrations of about 50 to 100 mg/L and trough concentrations of 20 to 40 mg/L. Levels higher than100 mg/L are toxic.

Itraconazole

The trough level should be maintained above 0.5 mg/L. Less than 0.5mg/L is a low concentration.

There may be toxicity issues at higher concentrations (greater than 4 mg/L). Liver function tests should be monitored during prolonged courses.

Posaconazole

The absorption and metabolism of posaconazole will vary from patient to patient. Recommended trough concentrations: 0.7 mg/L for prophylaxis and higher than 1 mg/L for invasive disease.

Voriconazole

The absorption and metabolism of voriconazole will vary from patient to patient. The voriconazole trough concentration should be maintained above 1 mg/L. Outcomes for bulky or disseminated infections are better when levels are higher than 2 mg/L.

Levels above 6 mg/L are more likely to lead to liver toxicity and levels above 10 mg/L should be avoided.

Amphotericin B

Monitoring of blood concentrations of amphotericin B during treatment is seldom indicated. The optimum serum concentrations of the drug for particular fungal infections have not been determined. Toxicity is assessed by monitoring renal function. Although amphotericin B is nephrotoxic, high blood concentrations do not lead to greater impairment of renal function, nor does renal failure result in higher blood concentrations.

Training courses

MRL organises regular training courses on the identification of pathogenic fungi. These are held at the University of Bristol and can accommodate up to 50 participants. Full details are available on request.

Individual training can be provided for NHS medical, technical and scientific staff. Please telephone or write to discuss your requirements.

External quality assurance

The MRL collaborates with the Quality Assurance laboratory in organising the UK National External Quality Assurance Schemes (NEQAS) in mycology. The laboratory itself participates in 3 UK NEQAS schemes; 2 for antibiotic assays (flucytosine and azole drugs) and the other for autoimmune serology and immunochemistry (Aspergillus, Candida, avian allergens and farmer’s lung antibody tests).

MRL also takes part in external quality assurance schemes for the validation of Aspergillus antigen detection and fungal PCR (quality control for molecular diagnostics), as well as the Instand e.V. (Germany) mycology external quality control scheme for mould and yeast identification, cryptococcal antigen and Candida antibody detection.

National collection of pathogenic fungi (NCPF)

The MRL is part of the Biological Resource Centre of Public Health England (HPACC). It houses the only UK microbial culture collection specialising in fungi pathogenic to humans and animals. At present the collection holds about 2,500 strains, many of which are available for distribution. These include:

  • approximately 700 strains of dermatophytes and related organisms from the UK and abroad from human and animal infections including many original type strains
  • approximately 1,500 mould strains from sub-cutaneous and deep-seated human and animal infection.
  • approximately 1,500 pathogenic yeast strains
  • more than 250 strains of dimorphic fungal pathogens

Fungal isolates

NCPF strains are supplied for research, quality control of microbiological media, disinfectants and antifungal susceptibility tests. Current prices and conditions of sale are available on request.

DNA services

As part of an ongoing modernisation of the collection, genomic DNA is being extracted for all of the fungal cultures in the collection. These can be made available on request.

Contact

Mycology reference laboratory (Mycology RL) Bristol

Public Health England South West Laboratory
Myrtle Road
Kingsdown

Bristol
BS2 8EL

Published 14 May 2013