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Published on: October 27, 2013
Diagnosis of infections caused by pathogenic free-living amoebae
Bruno da Rocha-Azevedo1, Herbert B Tanowitz, Francine Marciano-Cabral
1Department of Microbiology and Immunology, Virginia Commonwealth University School of Medicine, Richmond, VA 23298, USA.
Abstract:
Naegleria fowleri, Acanthamoeba spp., Balamuthia mandrillaris, and Sappinia sp. are pathogenic free-living amoebae. N. fowleri causes Primary Amoebic Meningoencephalitis, a rapidly fatal disease of the central nervous system, while Acanthamoeba spp. and B. mandrillaris cause chronic granulomatous encephalitis. Acanthamoeba spp. also can cause cutaneous lesions and Amoebic Keratitis, a sight-threatening infection of the cornea that is associated with contact lens use or corneal trauma. Sappinia pedata has been identified as the cause of a nonlethal case of amoebic encephalitis. In view of the potential health consequences due to infection with these amoebae, rapid diagnosis is critical for early treatment. Microscopic examination and culture of biopsy specimens, cerebral spinal fluid (CSF), and corneal scrapings have been used in the clinical laboratory. For amoebic keratitis, confocal microscopy has been used to successfully identify amoebae in corneal tissue. More recently, conventional and real-time PCR assays have been developed that are sensitive and specific for the amoebae. In addition, multiplex PCR assays are available for the rapid identification of these pathogens in biopsy tissue, CSF, and corneal specimens.
Insights
Rapid diagnosis of pathogenic free-living amoebae like Naegleria fowleri is critical. Advanced PCR assays offer sensitive and specific identification for early treatment of severe CNS and eye infections.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Parasitology
Background:
- Pathogenic free-living amoebae (FLA) such as Naegleria fowleri, Acanthamoeba spp., Balamuthia mandrillaris, and Sappinia sp. pose significant health risks.
- Infections caused by these amoebae include Primary Amoebic Meningoencephalitis (PAM), granulomatous encephalitis, cutaneous lesions, and the sight-threatening Amoebic Keratitis.
Purpose of the Study:
- To highlight the critical need for rapid diagnosis of infections caused by pathogenic free-living amoebae.
- To review current and emerging diagnostic methods for timely and accurate identification of these organisms.
Main Methods:
- Traditional methods include microscopic examination and culture of clinical specimens (biopsy, CSF, corneal scrapings).
- Confocal microscopy is utilized for visualizing amoebae in corneal tissue for Amoebic Keratitis diagnosis.
- Development and application of conventional and real-time PCR assays for sensitive and specific amoebae detection.
- Availability of multiplex PCR assays for simultaneous identification of multiple amoebic pathogens in various specimens.
Main Results:
- Microscopy and culture are established diagnostic tools but can be time-consuming.
- Confocal microscopy aids in diagnosing Amoebic Keratitis.
- PCR-based assays demonstrate high sensitivity and specificity for detecting pathogenic free-living amoebae.
- Multiplex PCR enables rapid, simultaneous identification of several amoebic species from clinical samples.
Conclusions:
- Rapid and accurate diagnosis of pathogenic free-living amoebae infections is essential for effective and timely treatment.
- Molecular diagnostic techniques, particularly PCR and multiplex PCR, offer significant advantages in speed and accuracy over traditional methods.
- Continued development and implementation of advanced diagnostic tools are crucial for combating severe amoebic infections of the central nervous system and eyes.
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