Which of the following bacterial structures is responsible for antibiotic resistance through enzymatic inactivation?
Answer: A
Plasmids are extrachromosomal DNA that carry antibiotic resistance genes and can be transferred between bacteria, making them primary vectors for resistance.
Q.62Easy
What is the primary mode of transmission for Hepatitis A virus in developing countries?
Answer: A
HAV is transmitted through fecal-oral route, particularly in areas with poor sanitation and hygiene practices.
Q.63Easy
Which bacterial species is most commonly associated with food poisoning from poultry products?
Answer: A
Salmonella typhimurium is a major cause of foodborne illness from poultry, causing acute gastroenteritis.
Q.64Easy
Which viral envelope protein is primarily responsible for binding to host cell receptors in influenza virus?
Answer: A
Hemagglutinin (H protein) binds to sialic acid receptors on host cells, initiating viral entry in influenza.
Q.65Easy
In bacterial DNA replication, which enzyme unwinds the double helix?
Answer: A
DNA helicase breaks hydrogen bonds between base pairs to unwind the DNA double helix during replication.
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Q.66Medium
Which of the following is a characteristic feature of SARS-CoV-2 that contributes to its high transmissibility?
Answer: A
The spike protein of SARS-CoV-2 has high affinity for ACE2 receptors, enabling efficient cellular entry and transmission.
Q.67Medium
A patient presents with atypical pneumonia. Which bacterial pathogen should be considered if Gram staining shows no organism but PCR is positive?
Answer: A
Mycoplasma lacks a cell wall and does not stain with Gram staining but is detectable by PCR, causing atypical pneumonia.
Q.68Medium
Which viral replication strategy involves reverse transcription of RNA to DNA?
Answer: A
Retroviruses like HIV use reverse transcriptase to synthesize DNA from their RNA genome for integration into host DNA.
Q.69Medium
Which bacterial structure mediates horizontal gene transfer through direct cell-to-cell contact?
Answer: A
The F pilus establishes a bridge between donor and recipient cells for plasmid transfer during bacterial conjugation.
Q.70Easy
Which of the following viruses has been successfully eradicated from the wild through vaccination programs?
Answer: A
Smallpox was declared eradicated in 1980 following intensive global vaccination campaigns, the only human virus to achieve this status.
Q.71Medium
A diagnostic lab suspects tuberculosis. Which staining technique is most appropriate for detecting Mycobacterium tuberculosis?
Answer: A
Mycobacterium tuberculosis has a waxy cell wall rich in mycolic acids that require acid-fast staining for visualization.
Q.72Medium
Which bacterial toxin directly inhibits protein synthesis by modifying EF-2 in host cells?
Answer: A
Diphtheria toxin catalyzes ADP-ribosylation of EF-2, blocking translation and causing severe systemic toxicity.
Q.73Medium
In viral latency, which herpesvirus establishes latency in sensory nerve ganglia?
Answer: A
HSV establishes latency in dorsal root ganglia and trigeminal ganglia, leading to recurrent herpes infections.
Q.74Hard
Which bacterial species is an obligate intracellular pathogen that causes Q fever?
Answer: A
Coxiella burnetii is highly infectious, forms spores, and is transmitted through aerosol route from infected animals.
Q.75Hard
A patient with recurrent respiratory infections is found to have defective viral interferon response. Which immune component is primarily affected?
Answer: A
Type I interferons (IFN-α/β) are crucial for antiviral immunity; defects impair early viral containment.
Q.76Hard
Which mechanism allows certain bacteria to survive within macrophages despite phagocytosis?
Answer: A
Mycobacterium tuberculosis inhibits phagolysosome maturation and produces catalase to neutralize reactive oxygen species.
Q.77Hard
In the context of emerging infectious diseases 2024-25, which coronavirus variant has shown increased immune evasion?
Answer: A
Recent variants like XEC demonstrate accumulated mutations in the receptor binding domain conferring immune escape properties.
Q.78Medium
Which viral enzyme is responsible for integrating retroviral DNA into the host genome?
Answer: A
Integrase catalyzes the insertion of viral DNA into the host chromosome, establishing persistent infection in retroviruses like HIV.
Q.79Medium
A nosocomial outbreak of antibiotic-resistant Acinetobacter baumannii is investigated. Which transmission route is most likely?
Answer: A
A. baumannii survives on dry surfaces and spreads via contact; it is a major nosocomial pathogen in ICU settings.
Q.80Easy
Which of the following bacterial structures is responsible for adherence to host cells?
Answer: A
Pili and fimbriae are hair-like appendages that facilitate bacterial adhesion to host cells and surfaces, essential for pathogenesis.
