SM SM Virology & Molecular Diagnostics 2 — Questions and Answers
Question 1: Which molecular method is used to detect and quantify HIV viral load in clinical practice?
- Southern blot hybridization
- Real-time quantitative RT-PCR (qRT-PCR) (Correct answer)
- Whole-genome sequencing by Sanger method
- Restriction fragment length polymorphism (RFLP) analysis
Correct answer: Real-time quantitative RT-PCR (qRT-PCR)
Real-time qRT-PCR quantifies HIV RNA copies/mL in plasma, guiding treatment decisions and monitoring antiretroviral therapy effectiveness.
Question 2: Herpes simplex virus (HSV) DNA PCR of cerebrospinal fluid is considered the gold standard for diagnosing:
- HSV genital ulcers
- HSV encephalitis (Correct answer)
- HSV labialis (cold sores)
- Neonatal HSV skin lesions
Correct answer: HSV encephalitis
CSF HSV PCR has >95% sensitivity and specificity for HSV encephalitis, replacing brain biopsy as the standard diagnostic approach.
Question 3: Which enzyme is the target of nucleoside reverse transcriptase inhibitors (NRTIs) used in HIV therapy?
- Integrase
- Reverse transcriptase (Correct answer)
- Protease
- Helicase
Correct answer: Reverse transcriptase
NRTIs are nucleoside analogs that competitively inhibit HIV reverse transcriptase, terminating DNA chain elongation during reverse transcription of viral RNA.
Question 4: Cytomegalovirus (CMV) disease in immunocompromised transplant patients is monitored using which laboratory approach?
- CMV IgM serology to detect active infection
- CMV pp65 antigenemia or quantitative PCR from blood (Correct answer)
- Shell vial culture with early antigen detection
- CMV-specific T-cell proliferation assay
Correct answer: CMV pp65 antigenemia or quantitative PCR from blood
CMV pp65 antigenemia assay and quantitative PCR are the standard methods for monitoring CMV viremia in transplant patients to guide preemptive antiviral therapy.
Question 5: Which feature distinguishes a virus's tropism for specific cell types?
- Size of the viral capsid relative to cell surface pores
- Interaction between viral surface proteins and specific host cell receptors (Correct answer)
- pH tolerance of the virus in the extracellular environment
- Replication rate compared to host cell division cycle
Correct answer: Interaction between viral surface proteins and specific host cell receptors
Viral tropism is determined by the compatibility between viral attachment proteins (e.g., glycoproteins, spikes) and specific host cell surface receptors required for entry.
Question 6: In next-generation sequencing (NGS) for clinical microbiology, which application is most established for direct patient care?
- Whole-genome sequencing for outbreak investigation and AMR gene detection (Correct answer)
- Metagenomics for routine diagnosis of all respiratory infections
- Single-cell sequencing to measure host immune response
- Nanopore sequencing for real-time antibiotic susceptibility testing
Correct answer: Whole-genome sequencing for outbreak investigation and AMR gene detection
Whole-genome sequencing (WGS) is most established clinically for outbreak epidemiology and comprehensive identification of antimicrobial resistance genes in bacterial isolates.
SM SM Virology & Molecular Diagnostics 2
Which molecular method is used to detect and quantify HIV viral load in clinical practice?