Q.1 Which bacterium is the primary causative agent of tuberculosis?
Streptococcus pneumoniae
Mycobacterium tuberculosis
Escherichia coli
Clostridium difficile
Explanation - Mycobacterium tuberculosis is a slow-growing, acid-fast bacterium responsible for tuberculosis, primarily affecting the lungs.
Correct answer is: Mycobacterium tuberculosis
Q.2 Which microorganism is responsible for causing malaria?
Plasmodium falciparum
Trypanosoma brucei
Leishmania donovani
Giardia lamblia
Explanation - Plasmodium species, particularly P. falciparum, are protozoan parasites transmitted by Anopheles mosquitoes and cause malaria.
Correct answer is: Plasmodium falciparum
Q.3 Which of the following viruses causes chickenpox?
Varicella-zoster virus
Measles virus
Rubella virus
Influenza virus
Explanation - Varicella-zoster virus (VZV) is a herpesvirus that causes chickenpox as the primary infection and shingles upon reactivation.
Correct answer is: Varicella-zoster virus
Q.4 Which bacterium is Gram-negative and often associated with urinary tract infections?
Staphylococcus aureus
Escherichia coli
Bacillus anthracis
Listeria monocytogenes
Explanation - Escherichia coli, a Gram-negative rod-shaped bacterium, is a common cause of urinary tract infections.
Correct answer is: Escherichia coli
Q.5 Which fungus is commonly responsible for athlete’s foot?
Candida albicans
Aspergillus fumigatus
Trichophyton rubrum
Cryptococcus neoformans
Explanation - Trichophyton rubrum is a dermatophyte fungus that infects skin, hair, and nails, causing athlete’s foot and other tinea infections.
Correct answer is: Trichophyton rubrum
Q.6 Which bacteria are known for producing tetanus toxin?
Clostridium botulinum
Clostridium tetani
Bacillus cereus
Listeria monocytogenes
Explanation - Clostridium tetani produces a neurotoxin called tetanospasmin, causing tetanus characterized by muscle rigidity and spasms.
Correct answer is: Clostridium tetani
Q.7 Which pathogen is primarily responsible for gonorrhea?
Neisseria gonorrhoeae
Treponema pallidum
Chlamydia trachomatis
Haemophilus influenzae
Explanation - Neisseria gonorrhoeae is a Gram-negative diplococcus that causes the sexually transmitted infection gonorrhea.
Correct answer is: Neisseria gonorrhoeae
Q.8 Which protozoan parasite causes sleeping sickness in humans?
Plasmodium vivax
Trypanosoma brucei
Leishmania major
Entamoeba histolytica
Explanation - Trypanosoma brucei, transmitted by tsetse flies, causes African trypanosomiasis or sleeping sickness.
Correct answer is: Trypanosoma brucei
Q.9 Which virus is responsible for causing AIDS?
Hepatitis B virus
Human Immunodeficiency Virus (HIV)
Influenza virus
Herpes simplex virus
Explanation - HIV targets CD4+ T cells and leads to acquired immunodeficiency syndrome (AIDS), characterized by severe immune suppression.
Correct answer is: Human Immunodeficiency Virus (HIV)
Q.10 Which Gram-positive bacterium causes diphtheria?
Corynebacterium diphtheriae
Streptococcus pyogenes
Bacillus anthracis
Listeria monocytogenes
Explanation - Corynebacterium diphtheriae produces diphtheria toxin, which can cause severe respiratory disease and systemic complications.
Correct answer is: Corynebacterium diphtheriae
Q.11 Which virus is responsible for causing measles?
Rubella virus
Measles virus
Mumps virus
Varicella-zoster virus
Explanation - Measles virus is a highly contagious paramyxovirus causing fever, cough, conjunctivitis, and a characteristic skin rash.
Correct answer is: Measles virus
Q.12 Which bacterium is known for causing whooping cough?
Bordetella pertussis
Haemophilus influenzae
Streptococcus pneumoniae
Neisseria meningitidis
Explanation - Bordetella pertussis produces toxins that lead to severe coughing fits, characteristic of whooping cough.
Correct answer is: Bordetella pertussis
Q.13 Which fungus is most commonly associated with opportunistic infections in immunocompromised patients?
Aspergillus fumigatus
Trichophyton rubrum
Microsporum canis
Candida albicans
Explanation - Candida albicans is a yeast that can cause systemic infections in immunocompromised individuals, such as oral thrush and candidemia.
Correct answer is: Candida albicans
Q.14 Which bacteria is responsible for causing plague?
Yersinia pestis
Salmonella typhi
Vibrio cholerae
Clostridium perfringens
Explanation - Yersinia pestis is a Gram-negative bacterium transmitted by flea bites and causes bubonic, septicemic, and pneumonic plague.
Correct answer is: Yersinia pestis
Q.15 Which of the following viruses is an RNA virus causing hemorrhagic fever?
Ebola virus
Hepatitis B virus
Herpes simplex virus
Adenovirus
Explanation - Ebola virus is a filovirus with RNA genome that causes severe hemorrhagic fever with high mortality rates.
Correct answer is: Ebola virus
Q.16 Which protozoan parasite causes amebic dysentery?
Giardia lamblia
Entamoeba histolytica
Plasmodium malariae
Trypanosoma cruzi
Explanation - Entamoeba histolytica infects the colon and can cause severe diarrhea, abdominal pain, and dysentery.
Correct answer is: Entamoeba histolytica
Q.17 Which bacterium causes food poisoning due to its heat-stable toxin in rice dishes?
Clostridium botulinum
Bacillus cereus
Salmonella enterica
Listeria monocytogenes
Explanation - Bacillus cereus produces a heat-stable enterotoxin causing vomiting and diarrhea, often from improperly stored rice.
Correct answer is: Bacillus cereus
Q.18 Which virus is primarily responsible for causing viral hepatitis B?
Hepatitis B virus
Hepatitis A virus
Hepatitis C virus
Hepatitis E virus
Explanation - Hepatitis B virus (HBV) is a DNA virus that infects the liver, causing acute and chronic hepatitis, cirrhosis, and hepatocellular carcinoma.
Correct answer is: Hepatitis B virus
Q.19 Which bacteria is associated with causing dental caries?
Streptococcus mutans
Staphylococcus aureus
Lactobacillus acidophilus
Escherichia coli
Explanation - Streptococcus mutans metabolizes sugars to produce acids that demineralize tooth enamel, causing dental caries.
Correct answer is: Streptococcus mutans
Q.20 Which fungus is known to cause cryptococcal meningitis in immunocompromised individuals?
Candida albicans
Aspergillus fumigatus
Cryptococcus neoformans
Histoplasma capsulatum
Explanation - Cryptococcus neoformans is an encapsulated yeast that can cross the blood-brain barrier and cause life-threatening meningitis, especially in AIDS patients.
Correct answer is: Cryptococcus neoformans
Q.21 Which Gram-negative bacterium causes cholera?
Vibrio cholerae
Escherichia coli
Salmonella typhi
Shigella dysenteriae
Explanation - Vibrio cholerae produces cholera toxin, causing profuse watery diarrhea and dehydration, typically via contaminated water.
Correct answer is: Vibrio cholerae
Q.22 Which virus causes rabies in humans?
Lyssavirus
Influenza virus
Paramyxovirus
Rhabdovirus
Explanation - Rabies virus is a rhabdovirus that infects the nervous system and is transmitted mainly through the bite of infected animals.
Correct answer is: Rhabdovirus
Q.23 Which bacterium is known for causing botulism through preformed toxins in food?
Clostridium botulinum
Clostridium tetani
Bacillus cereus
Listeria monocytogenes
Explanation - Clostridium botulinum produces a potent neurotoxin leading to flaccid paralysis when ingested in contaminated food.
Correct answer is: Clostridium botulinum
Q.24 Which microorganism is responsible for leprosy?
Mycobacterium leprae
Mycobacterium tuberculosis
Treponema pallidum
Borrelia burgdorferi
Explanation - Mycobacterium leprae is an acid-fast bacillus that infects skin and peripheral nerves, causing leprosy (Hansen's disease).
Correct answer is: Mycobacterium leprae
Q.25 Which protozoan parasite is known to cause toxoplasmosis?
Plasmodium falciparum
Toxoplasma gondii
Giardia lamblia
Trypanosoma cruzi
Explanation - Toxoplasma gondii infects humans through contaminated food or cat feces and can cause severe disease in immunocompromised individuals and during pregnancy.
Correct answer is: Toxoplasma gondii