Q.1 Which bacterium is the primary cause of tuberculosis?
Streptococcus pneumoniae
Mycobacterium tuberculosis
Escherichia coli
Clostridium tetani
Explanation - Mycobacterium tuberculosis is a slow-growing, acid-fast bacillus responsible for tuberculosis.
Correct answer is: Mycobacterium tuberculosis
Q.2 What is the primary mode of transmission for Hepatitis B virus?
Fecal-oral route
Respiratory droplets
Blood and body fluids
Vector-borne
Explanation - Hepatitis B virus is transmitted mainly via blood, sexual contact, or from mother to child during childbirth.
Correct answer is: Blood and body fluids
Q.3 Which Gram-negative bacillus is most commonly associated with urinary tract infections?
Pseudomonas aeruginosa
Escherichia coli
Salmonella typhi
Listeria monocytogenes
Explanation - E. coli, particularly uropathogenic strains, are the leading cause of community-acquired urinary tract infections.
Correct answer is: Escherichia coli
Q.4 Which microorganism causes the disease known as whooping cough?
Bordetella pertussis
Haemophilus influenzae
Streptococcus pyogenes
Corynebacterium diphtheriae
Explanation - Bordetella pertussis is a Gram-negative coccobacillus that produces toxins causing severe coughing fits in whooping cough.
Correct answer is: Bordetella pertussis
Q.5 What is the main virulence factor of Staphylococcus aureus responsible for toxic shock syndrome?
Exotoxin TSST-1
Capsule
Endotoxin LPS
Flagella
Explanation - Toxic shock syndrome toxin-1 (TSST-1) is a superantigen produced by some strains of Staphylococcus aureus, causing systemic inflammation.
Correct answer is: Exotoxin TSST-1
Q.6 Which of the following is a characteristic feature of Gram-positive bacteria?
Thin peptidoglycan layer
Presence of lipopolysaccharide
Thick peptidoglycan layer
Outer membrane with porins
Explanation - Gram-positive bacteria have a thick peptidoglycan cell wall which retains the crystal violet stain during Gram staining.
Correct answer is: Thick peptidoglycan layer
Q.7 The causative agent of malaria belongs to which group?
Bacteria
Virus
Protozoa
Fungi
Explanation - Malaria is caused by Plasmodium species, which are protozoan parasites transmitted by Anopheles mosquitoes.
Correct answer is: Protozoa
Q.8 Which of the following viruses is known to cause hemorrhagic fever?
Dengue virus
Influenza virus
Rotavirus
Rhinovirus
Explanation - Dengue virus, transmitted by Aedes mosquitoes, can lead to dengue hemorrhagic fever, characterized by bleeding and plasma leakage.
Correct answer is: Dengue virus
Q.9 Which antibiotic is the drug of choice for treating syphilis?
Penicillin G
Ciprofloxacin
Vancomycin
Erythromycin
Explanation - Penicillin G is highly effective against Treponema pallidum, the bacterium causing syphilis.
Correct answer is: Penicillin G
Q.10 Which bacterial genus is known for producing endospores?
Clostridium
Neisseria
Mycoplasma
Vibrio
Explanation - Clostridium species produce highly resistant endospores that allow survival in harsh environments.
Correct answer is: Clostridium
Q.11 Which virus is responsible for causing chickenpox?
Varicella-zoster virus
Measles virus
Rubella virus
Coxsackievirus
Explanation - Varicella-zoster virus (VZV) causes chickenpox; it can later reactivate as shingles.
Correct answer is: Varicella-zoster virus
Q.12 Which microorganism is the leading cause of bacterial meningitis in adults?
Streptococcus pneumoniae
Haemophilus influenzae
Listeria monocytogenes
Neisseria meningitidis
Explanation - S. pneumoniae is the most common cause of bacterial meningitis in adults, leading to inflammation of the meninges.
Correct answer is: Streptococcus pneumoniae
Q.13 Which of the following is a common symptom of tetanus infection?
Muscle spasms
Cough
Skin rash
Diarrhea
Explanation - Tetanus toxin (produced by Clostridium tetani) affects the nervous system, causing severe muscle spasms.
Correct answer is: Muscle spasms
Q.14 Which bacteria is associated with peptic ulcers?
Helicobacter pylori
Escherichia coli
Salmonella enterica
Staphylococcus aureus
Explanation - H. pylori colonizes the stomach lining and produces urease, contributing to ulcer formation.
Correct answer is: Helicobacter pylori
Q.15 Which microorganism is the causative agent of gonorrhea?
Neisseria gonorrhoeae
Chlamydia trachomatis
Treponema pallidum
Mycoplasma genitalium
Explanation - Neisseria gonorrhoeae is a Gram-negative diplococcus causing sexually transmitted infection gonorrhea.
Correct answer is: Neisseria gonorrhoeae
Q.16 Which test is commonly used for rapid diagnosis of influenza virus infection?
ELISA
Rapid antigen detection test
Gram stain
PCR for bacteria
Explanation - Rapid antigen tests detect influenza virus antigens in respiratory specimens within minutes.
Correct answer is: Rapid antigen detection test
Q.17 Which of the following fungi causes systemic infection in immunocompromised patients?
Candida albicans
Aspergillus fumigatus
Histoplasma capsulatum
All of the above
Explanation - Candida, Aspergillus, and Histoplasma species can all cause serious systemic infections, especially in immunocompromised individuals.
Correct answer is: All of the above
Q.18 Which parasite is responsible for lymphatic filariasis?
Wuchereria bancrofti
Plasmodium falciparum
Trypanosoma brucei
Entamoeba histolytica
Explanation - Wuchereria bancrofti is transmitted by mosquitoes and causes lymphatic filariasis, leading to elephantiasis.
Correct answer is: Wuchereria bancrofti
Q.19 Which bacterial structure is primarily responsible for motility?
Pili
Flagella
Capsule
Cell wall
Explanation - Flagella are whip-like structures that provide motility to bacteria.
Correct answer is: Flagella
Q.20 Which virus is known for causing severe acute respiratory syndrome (SARS)?
SARS-CoV
MERS-CoV
Influenza A
Respiratory syncytial virus
Explanation - SARS-CoV is a coronavirus responsible for the outbreak of severe acute respiratory syndrome in 2002–2003.
Correct answer is: SARS-CoV
Q.21 Which of the following is a common zoonotic bacterial infection?
Brucellosis
Measles
Polio
Rubella
Explanation - Brucellosis is a bacterial zoonosis transmitted from animals to humans through unpasteurized dairy or contact with infected animals.
Correct answer is: Brucellosis
Q.22 Which microorganism causes diphtheria?
Corynebacterium diphtheriae
Streptococcus pyogenes
Bordetella pertussis
Haemophilus influenzae
Explanation - Corynebacterium diphtheriae produces diphtheria toxin, causing pseudomembrane formation in the throat.
Correct answer is: Corynebacterium diphtheriae
Q.23 Which of the following is the primary reservoir for rabies virus?
Dogs
Cattle
Birds
Fish
Explanation - Dogs are the main reservoir for rabies virus, which is transmitted to humans via bites.
Correct answer is: Dogs
Q.24 Which laboratory test is used to confirm HIV infection?
Western blot
Gram stain
Rapid antigen test
PCR for bacteria
Explanation - Western blot is used to confirm the presence of HIV-specific antibodies after initial screening tests.
Correct answer is: Western blot
Q.25 Which of the following bacteria is acid-fast?
Mycobacterium tuberculosis
Staphylococcus aureus
Escherichia coli
Clostridium difficile
Explanation - Acid-fast bacteria, like Mycobacterium tuberculosis, retain carbol fuchsin dye even after acid-alcohol decolorization.
Correct answer is: Mycobacterium tuberculosis