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Diagnostic Microbiology Laboratory (DML)

By Laboratories for Wildlife Disease Diagnostics

The USGS National Wildlife Health Center's Diagnostic Microbiology Laboratory (DML) routinely performs a variety of procedures to isolate and identify important pathogenic bacteria and fungi from wildlife.  Microbes are identified based upon morphological characteristics, biochemical/physiological properties, molecular assays (e.g., PCR), and DNA sequence analysis.

DML Capabilities

Diagnostic Bacteriology:

  • Routine culture of aerobic and anaerobic bacteria using a variety of standard culture media
  • Selective culture for slow-growing or fastidious bacteria such as Mycoplasma, Francisella tularensis (tularemia), etc.
  • Identification of bacterial isolates through the use of physiological tests and DNA sequencing
  • Identification of unculturable or difficult-to-culture bacteria (e.g., Mycobacterium) in tissue samples by pan-bacterial PCR and DNA sequencing of the 16S rRNA gene
  • Detection of Clostridium piliforme (Tyzzer’s disease) by PCR
  • Samples suspect for certain organisms such as Chlamydia/Chlamidophila (chlamydiosis), Leptospira (leptospirosis), and Francisella tularensis (tularemia), are submitted to a specialty laboratory
Conventional PCR and DNA sequencing
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Conventional PCR and DNA sequencing are used to detect unculturable microorganisms in diagnostic samples. (Public domain.)

Diagnostic Mycology:

  • Routine culture and identification of filamentous fungi and yeasts using a variety of culture media
  • Selective culture for slow-growing and difficult-to-isolate fungi such as dermatophytes, Batrachochytrium (chytridiomycosis), Ophidiomyces ophiodiicola (snake fungal disease) and other reptile-infecting fungi, Pseudogymnoascus destructans (white-nose syndrome), etc.
  • Identification of fungal isolates based on morphology and DNA sequencing
  • Identification of unculturable or difficult-to-culture fungi in tissue samples by pan-fungal PCR and DNA sequencing of the internal transcribed spacer (ITS) region of the rRNA gene complex
  • Detection of Batrachochytrium dendrobatidis and Batrachochytrium salamandrivorans (chytridiomycosis) by real-time PCR
  • Detection of Ophidiomyces ophiodiicola (snake fungal disease) by real-time PCR
  • Detection of Pseudogymnoascus destructans (white-nose syndrome) by real-time PCR

Microbial Toxins:

  • Identification of Clostridium botulinum neurotoxin types C and E using the mouse protection assay
Routine culture
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Routine microbial culture using a variety of culture media. (Public domain.)

Additional Characterizations of Isolates:

  • Strain characterization of bacteria and fungi for epidemiological investigations by multilocus sequence typing
  • Identification of Pasteurella multocida non-capsular serotypes
  • Identification of Salmonella serotypes is performed by a reference laboratory
  • Characterization of novel bacterial and fungal pathogens

Other Capabilities:

  • Detection of circoviruses by PCR (see Diagnostic Virology Laboratory (DVL) for additional viral diagnostic tests)
  • Confirmation of host-species identity through sequencing of DNA barcoding regions
  • Development and optimization of molecular assays for detection of bacterial and fungal pathogens
Real-time PCR
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Real-time PCR is used to confirm the presence of certain pathogenic microorganisms in samples.(Public domain.)