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Published on: March 22, 2012
Invasive aspergillosis due to cryptic Aspergillus species: A prospective study from a single centre in India
R Sruti Janani1, Immaculata Xess1, Bimal Kumar Das1
1All India Institute of Medical Sciences, New Delhi, India.
Background:
& objective: The existence of visually identical cryptic Aspergillus species that can be distinguished only by molecular techniques is becoming more widely acknowledged. For the majority of antifungal drugs, these are known to exhibit a greater minimal inhibitory concentration in vitro. For the purpose of receiving the proper care, it is crucial to identify these species at right time. Our aim in this work is to identify and describe the Aspergillus species that are cryptic from all of the clinical samples.
Methods:
Routine samples from inpatients and outpatients received in department of Microbiology, All India Institute of Medical Sciences, New Delhi, showing growth of Aspergillus species were included in this study. Phenotypic and Matrix Assisted Laser Desorption Ionisation - Time of Flight identified isolates were analysed for cryptic species, by PCR and ITS/ß - tubulin sequencing. In accordance with CLSI recommendations, antifungal susceptibility testing was conducted using micro broth dilution.
Results:
Of the 94 isolates, 54 A. fumigatus, 34 A. flavus, 3 A. nidulans, 2 A. terreus, and 1 A. niger were morphologically identified. MALDI-TOF misidentified 2 A. nidulans isolates and 1 A, stellatus isolate. The ß - tubulin sequence analysis revealed that 2 isolates (2.08 %) were cryptic, one was A. stellatus and another one was A. tubingensis.
Insights
Cryptic Aspergillus species, visually identical but molecularly distinct, pose diagnostic challenges. This study identified two cryptic species, Aspergillus stellatus and Aspergillus tubingensis, in clinical samples using molecular techniques.
Area of Science:
- Medical Mycology
- Molecular Diagnostics
- Antimicrobial Resistance
Background:
- Visually identical cryptic Aspergillus species require molecular identification due to differing antifungal susceptibility.
- Accurate identification is crucial for appropriate patient treatment and management.
- Cryptic species often exhibit higher minimal inhibitory concentrations for antifungal drugs.
Purpose of the Study:
- To identify and characterize cryptic Aspergillus species from clinical samples.
- To highlight the importance of molecular methods in distinguishing cryptic Aspergillus species.
- To contribute to better understanding of Aspergillus-related infections.
Main Methods:
- Analysis of Aspergillus isolates from clinical samples using phenotypic identification and Matrix Assisted Laser Desorption Ionisation - Time of Flight (MALDI-TOF).
- Molecular identification of cryptic species through Polymerase Chain Reaction (PCR) and Internal Transcribed Spacer (ITS)/ß-tubulin gene sequencing.
- Antifungal susceptibility testing performed using micro broth dilution according to CLSI guidelines.
Main Results:
- Morphological identification revealed common Aspergillus species, but MALDI-TOF misidentified some isolates.
- Molecular analysis, specifically ß-tubulin sequencing, identified two cryptic species: Aspergillus stellatus and Aspergillus tubingensis (2.08% of isolates).
- This highlights limitations of phenotypic and MALDI-TOF identification for certain Aspergillus species.
Conclusions:
- Molecular techniques like ß-tubulin sequencing are essential for accurate identification of cryptic Aspergillus species.
- The identification of Aspergillus stellatus and Aspergillus tubingensis underscores the need for molecular diagnostics in clinical microbiology.
- Distinguishing cryptic species is vital for guiding antifungal therapy and improving patient outcomes.
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