Question 1

Malaria parasite lives in?

Accepted Answer

Answer reason: Plasmodium parasites undergo an initial hepatic phase but the symptomatic blood-stage infection occurs within red blood cells. Asexual replication in RBCs leads to cyclic hemolysis, fever, and anemia. Therefore, among the options, the parasite lives in RBCs.

Question 2

Bordetella pertussis causes ...?

Accepted Answer

Answer reason: Bordetella pertussis is a small gram-negative coccobacillus that causes pertussis (whooping cough). It adheres to the ciliated respiratory epithelium and releases pertussis toxin, leading to paroxysmal coughing with an inspiratory "whoop." The other conditions are caused by different pathogens: Neisseria gonorrhoeae (gonorrhea), Mycobacterium leprae (leprosy), and Treponema pallidum (syphilis). Therefore, whooping cough is the correct choice.

Question 3

Of the following infectious organisms, which of these will result in colitis for a patient?

Accepted Answer

Answer reason: Clostridium difficile overgrowth in the colon produces toxins A and B that cause pseudomembranous colitis, leading to watery diarrhea and abdominal pain, often after antibiotic use. MRSA and VRE are important nosocomial pathogens but typically cause skin/soft tissue, bloodstream, or urinary infections rather than colitis. Therefore, C. difficile is the organism classically associated with colitis.

Question 4

Malaria is caused by?

Accepted Answer

Answer reason: Malaria is caused by Plasmodium species, which are protozoan parasites transmitted by Anopheles mosquitoes. These eukaryotic organisms invade liver cells and red blood cells, leading to cyclic fevers, anemia, and other complications. They are not bacteria or fungi, making parasite the correct classification.

Question 5

Hepatitis A usually resolves in?

Accepted Answer

Answer reason: Hepatitis A is an acute, self-limited viral infection, and most uncomplicated cases recover within several weeks. Standard references note that symptomatic illness typically resolves in about 2–6 weeks, with no progression to chronic hepatitis. A minority may have a prolonged or relapsing course lasting up to 6 months, but this is not the usual outcome.

Question 6

Blood transfusion can transmit?

Accepted Answer

Answer reason: Hepatitis C is a well-recognized transfusion-transmitted virus because it spreads via blood and blood products; although screening has markedly reduced risk, it remains the classic example. Hepatitis A and E are primarily fecal–oral infections and are not typically transmitted through transfusion in standard exam contexts. Hepatitis B is also transfusion-transmissible but not listed. Therefore, the best answer from the options is Hepatitis C.

Question 7

Malaria is transmitted by?

Accepted Answer

Answer reason: Malaria is transmitted to humans via the bite of infected female Anopheles mosquitoes, which require blood meals for egg development. Male mosquitoes do not bite and therefore do not transmit malaria. Aedes mosquitoes transmit diseases such as dengue, Zika, and yellow fever, not malaria. Fleas are vectors for plague, not malaria.

Question 8

Hepatitis D virus requires which other virus to infect?

Accepted Answer

Answer reason: Hepatitis D virus (HDV) is a defective RNA virus that requires the hepatitis B virus (HBV) for replication and assembly. It uses the hepatitis B surface antigen (HBsAg) as its envelope to enter hepatocytes. Thus, HDV infection occurs only as coinfection with or superinfection of HBV. Immunization against HBV prevents HDV infection.

Question 9

Chickenpox lesions are described as?

Accepted Answer

Answer reason: Varicella (chickenpox) eruptions occur in successive crops, so lesions are seen simultaneously as macules, papules, vesicles, and crusts. This polymorphic appearance at different stages is characteristic. Therefore they are not all in the same stage, nor limited to scabs, and a rash is present.

Question 10

Rash in smallpox appears?

Accepted Answer

Answer reason: Smallpox produces a centrifugal rash that begins on the face and distal extremities and then spreads to the trunk. Lesions are most dense on the face, arms, and legs, including the palms and soles, and are typically in the same stage of development. In contrast, varicella starts on the trunk with a centripetal distribution. Therefore, the first appearance is on the face and extremities.

Question 11

The organism causing malaria is found in?

Accepted Answer

Answer reason: Malaria is caused by Plasmodium species, which after an initial hepatic stage, invade and multiply within red blood cells. The clinical disease correlates with the erythrocytic cycle, and diagnosis is made by detecting parasites on peripheral blood smears. Therefore, the organism is found in the blood of infected individuals.

Question 12

Urethral discharge is common in?

Accepted Answer

Answer reason: Purulent urethral discharge with dysuria is a hallmark of Neisseria gonorrhoeae urethritis. Gonorrhea commonly causes mucopurulent exudate due to inflammation of the urethral epithelium. Tuberculosis, diabetes, and typhoid do not typically present with urethral discharge.

Question 13

Tetanus is a?

Accepted Answer

Answer reason: Tetanus is caused by Clostridium tetani spores that enter the body through contaminated wounds, typically from soil or dust. It is not transmitted person-to-person, so it is considered non-communicable. It is not spread via airborne, waterborne, or foodborne routes.

Question 14

Painless genital ulcer is seen in?

Accepted Answer

Answer reason: Primary syphilis presents with a single, indurated, clean-based chancre that is typically painless, often with nontender regional lymphadenopathy. Gonorrhea and most chlamydial infections cause urethritis or cervicitis rather than ulcers. Herpes simplex virus produces painful vesicular lesions that ulcerate. Therefore, the classic painless genital ulcer is most consistent with syphilis.

Question 15

Dark-field microscopy is used to diagnose?

Accepted Answer

Answer reason: Dark-field microscopy allows visualization of thin, motile spirochetes that are not easily seen with Gram stain. Treponema pallidum, the causative agent of syphilis, can be identified directly from chancre exudate using dark-field examination. Gonorrhea and chlamydia are typically diagnosed by NAATs, and HIV is diagnosed by serology/antigen or nucleic acid testing, not microscopy.

Question 16

Which is Sexually Transmitted Disease?

Accepted Answer

Answer reason: Gonorrhea is a sexually transmitted infection caused by Neisseria gonorrhoeae and is spread through vaginal, oral, or anal sexual contact. Diabetes and anemia are not infectious diseases and are not transmitted sexually. While some types of hepatitis (especially hepatitis B) can be sexually transmitted, the term 'hepatitis' is nonspecific; the clearest STI listed is gonorrhea. Therefore, the best single answer is gonorrhea.

Question 17

Tuberculosis is a ... disease?

Accepted Answer

Answer reason: Tuberculosis is caused by Mycobacterium tuberculosis, which is an acid-fast bacterium. Therefore, TB is classified as a bacterial infectious disease rather than viral, fungal, or protozoal. While it primarily affects the lungs, it can disseminate to other organs. Its bacterial etiology explains why treatment requires prolonged multi-drug antibiotic therapy.

Question 18

A person diagnosed to have anogenital warts with high risk of cancer. Which strain of HPV is predisposing this patient with a high risk of cancer?

Accepted Answer

Answer reason: High-risk HPV types associated with anogenital cancers (especially cervical and anal cancer) include HPV 16 and HPV 18. These types produce oncogenic proteins (E6 and E7) that inactivate tumor suppressors (p53 and Rb), promoting malignant transformation. In contrast, HPV 6 is classically low-risk and causes benign genital warts. Therefore, HPV 18 is the best answer among the options.

Question 19

Among the given options, which disease has the highest mortality rate once it becomes clinically evident?

Accepted Answer

Answer reason: Rabies is almost universally fatal once clinical symptoms appear (near 100% case fatality), because the infection has reached the central nervous system and effective curative therapy is lacking at that stage. In contrast, Ebola and Nipah have high but variable case-fatality rates that are generally well below rabies and depend on outbreak context and care. Zika infection is usually mild with very low mortality, though it can cause serious congenital complications. Therefore, rabies has the highest mortality rate once clinically evident.

Question 20

Peptic ulcers are caused by which bacterium?

Accepted Answer

Answer reason: Helicobacter pylori is the most common infectious cause of peptic ulcer disease, especially duodenal ulcers, by colonizing the gastric mucosa and disrupting mucosal defenses. Its urease activity helps it survive in acidic environments and contributes to inflammation and mucosal injury. Vibrio cholerae causes secretory diarrhea, E. coli commonly causes gastroenteritis/UTIs, and Streptococcus is not a typical cause of peptic ulcer disease.

Question 21

What is the causative organism of plague?

Accepted Answer

Answer reason: Plague is caused by Yersinia pestis, a gram-negative coccobacillus typically transmitted by the bite of infected fleas from rodent reservoirs. It can present as bubonic plague (painful lymphadenopathy), septicemic plague, or pneumonic plague. The other options cause different diseases: Salmonella typhi causes typhoid fever, Mycobacterium tuberculosis causes tuberculosis, and Vibrio cholerae causes cholera.

Question 22

Measles is transmitted mainly by?

Accepted Answer

Answer reason: Measles (rubeola) spreads primarily via the respiratory route through airborne droplet nuclei/aerosolized particles that can remain suspended and infectious in the air. Transmission commonly occurs after inhalation of these particles or contact with respiratory secretions followed by self-inoculation of mucous membranes. It is not typically spread by contaminated food, insect vectors, or simple skin-to-skin contact.

Question 23

Prevention of Typhoid fever is done by?

Accepted Answer

Answer reason: Typhoid fever is caused by Salmonella enterica serovar Typhi, and specific prevention includes immunization with a typhoid vaccine (e.g., Vi polysaccharide or oral Ty21a). BCG is for tuberculosis, oral polio vaccine is for poliomyelitis, and rabies vaccine prevents rabies after exposure. Therefore, the correct preventive vaccine for typhoid is the typhoid vaccine.

Question 24

Tetanus spores are destroyed by?

Accepted Answer

Answer reason: Clostridium tetani forms hardy bacterial spores that are resistant to simple methods like washing with water, freezing, and brief boiling. Autoclaving uses pressurized steam at high temperature for a defined time, which is a validated sterilization method that reliably destroys spores. Boiling for 5 minutes is disinfection and does not consistently eliminate bacterial spores. Therefore, autoclaving is the best answer.

Question 25

The most common causative organism of UTI is?

Accepted Answer

Answer reason: Escherichia coli is the most common cause of community-acquired urinary tract infections because it is a frequent gastrointestinal flora organism that can colonize the periurethral area and ascend into the urinary tract. Its virulence factors (e.g., adhesins such as P fimbriae) facilitate attachment to uroepithelium and infection. Pseudomonas is more associated with complicated or healthcare-associated UTIs (e.g., catheter-related), while Streptococcus and Staphylococcus species are less common overall causes of UTI.

Question 26

Neonatal tetanus is usually due to?

Accepted Answer

Answer reason: Neonatal tetanus is most commonly caused by contamination of the umbilical stump with Clostridium tetani spores due to non-sterile delivery and cord-cutting practices. The organism produces tetanospasmin, a neurotoxin that blocks inhibitory neurotransmission and leads to rigidity and spasms. Breast milk is not a typical transmission route, mosquitoes do not transmit tetanus, and vaccination prevents rather than causes neonatal tetanus (maternal immunization provides passive protection to the newborn).

Question 27

Father of Microbiology is known as?

Accepted Answer

Answer reason: Louis Pasteur is widely recognized as the “father of microbiology” for foundational work proving microbes cause fermentation and disease, and for developing pasteurization and early vaccines (e.g., rabies, anthrax). Robert Koch is more specifically associated with bacteriology and Koch’s postulates linking specific organisms to specific diseases. Antonie van Leeuwenhoek is often called the father of microscopy/microbiology for first observing microorganisms, but standard exam usage for “father of microbiology” typically refers to Pasteur. Joseph Lister is primarily known for antiseptic surgery and infection prevention.

Question 28

Bacteria reproduce mainly by which method?

Accepted Answer

Answer reason: Most bacteria primarily reproduce asexually by binary fission, where a single cell replicates its DNA and divides into two genetically identical daughter cells. Budding is more typical of yeasts and only a few bacteria. Conjugation is horizontal gene transfer (genetic exchange) rather than a main reproductive method. Spore formation is a survival mechanism under harsh conditions, not the primary means of reproduction.

Question 29

Why is honey avoided in infants?

Accepted Answer

Answer reason: Honey can contain Clostridium botulinum spores, which can germinate in an infant’s immature gastrointestinal tract and produce botulinum toxin. This can lead to infant botulism, characterized by constipation, hypotonia ("floppy baby"), weak cry, and poor feeding. The risk is highest in infants under 12 months, so honey is avoided to prevent this potentially life-threatening neuroparalytic illness.

Question 30

How is malaria transmitted?

Accepted Answer

Answer reason: Malaria is most commonly transmitted by bites from infected female Anopheles mosquitoes. It can also be transmitted through exposure to infected blood, including blood transfusions, shared/contaminated needles, and less commonly via organ transplantation. Congenital transmission (mother to baby) can occur during pregnancy or delivery. Therefore, all listed routes are valid, making "All of Above" the best answer.

Question 31

Enteromix is the vaccine of?

Accepted Answer

Answer reason: Enteromix is a brand name used for a typhoid vaccine preparation, intended to induce immunity against Salmonella Typhi infection. Among the options, typhoid is the only disease classically associated with this vaccine name. Cholera vaccines are typically labeled as oral cholera vaccines, tuberculosis uses BCG, and there is no standard vaccine called Enteromix for cancer.

Question 32

Which of the following is NOT a water borne disease?

Accepted Answer

Answer reason: Water-borne diseases are typically transmitted through ingestion of contaminated water via the fecal-oral route. Hepatitis A, cholera (Vibrio cholerae), and typhoid (Salmonella Typhi) are classic water/food-borne infections. Measles is primarily transmitted via respiratory droplets and airborne spread, not via contaminated water.

Question 33

Which of the following is a Communicable disease?

Accepted Answer

Answer reason: Measles is a highly contagious viral infection transmitted person-to-person via respiratory droplets/airborne spread, making it a communicable disease. Asthma, diabetes, and Alzheimer disease are noncommunicable conditions that do not spread through infectious transmission. Therefore, measles is the only option that fits the definition of a communicable disease.

Question 34

Which test confirms tuberculosis?

Accepted Answer

Answer reason: Confirmation of active pulmonary tuberculosis requires direct detection of Mycobacterium tuberculosis from respiratory specimens, such as sputum acid-fast bacilli (AFB) smear and/or culture/NAAT. CBC and ESR are nonspecific inflammatory markers and cannot establish a TB diagnosis. A chest X-ray can suggest TB (e.g., upper-lobe infiltrates/cavitation) but is not confirmatory without microbiologic evidence. Therefore, sputum AFB is the best confirmatory test among the options.

Question 35

Four years old baby was diagnose with Astma, brought to ER with complaining of mild fever, throat pain, fatigue and cough, Physical examination shows Hyperemia Conjunctivitis and nasal congestion, giving only symptomatic treatment to the patient, after 2 days patient again brought to emergency with dyspnea and cough, what possible virus could cause is infection?

Accepted Answer

Answer reason: The combination of fever, sore throat, cough, nasal congestion, and especially conjunctivitis is classic for adenovirus, which commonly causes pharyngoconjunctival fever and upper respiratory infection in children. In a child with asthma, a viral URI can precipitate bronchospasm, leading to dyspnea and worsening cough after a short interval. Influenza A typically causes more abrupt, high fever and prominent myalgias, while parainfluenza is more associated with croup (barking cough/stridor) than conjunctivitis. Coronaviruses can cause URI symptoms but conjunctivitis is less characteristic than with adenovirus.

Question 36

Which of the following disease has the highest mortality once clinically manifested?

Accepted Answer

Answer reason: Rabies has the highest mortality once clinical symptoms appear because symptomatic rabies is almost universally fatal due to progressive encephalitis. In contrast, Ebola and Nipah have high but variable case-fatality rates and some patients survive with supportive/targeted care. Zika infection is typically mild and rarely fatal, though it is associated with congenital complications. Therefore, the single best answer is rabies.

Question 37

Which of the following is not a non-communicable disease?

Accepted Answer

Answer reason: Non-communicable diseases are not spread person-to-person and typically include chronic conditions like diabetes, hypertension, and cancer. Tuberculosis is caused by Mycobacterium tuberculosis and is transmitted via airborne droplet nuclei from an infectious person. Because it is an infectious, transmissible disease, it is considered communicable and therefore is not a non-communicable disease.

Question 38

Who was the first person to view microorganisms (Bacteria and protozoa)-?

Accepted Answer

Answer reason: Antony (Antonie) van Leeuwenhoek was the first to directly observe and describe microorganisms using his handcrafted microscopes in the 1670s, reporting “animalcules” consistent with bacteria and protozoa. The other options are associated with different discoveries: Robert Brown (cell nucleus), Alexander Fleming (penicillin), and Edward Jenner (smallpox vaccination). Therefore, van Leeuwenhoek is the single best answer for first viewing microorganisms.

Question 39

Hepatitis A virus is transmitted mainly by which route?

Accepted Answer

Answer reason: Hepatitis A virus is classically transmitted via the fecal–oral route, typically through contaminated food or water or close person-to-person contact in settings with poor sanitation. In contrast, blood transfusion is a characteristic transmission route for hepatitis B/C (parenteral exposure), not HAV. Sexual contact can transmit HAV in certain practices but is not the main route overall. Insect bites are not a recognized transmission route for HAV.

Question 40

The causative organism of diphtheria is?

Accepted Answer

Answer reason: Diphtheria is caused by Corynebacterium diphtheriae, a gram-positive bacillus that can produce a potent exotoxin. The diphtheria toxin leads to local pseudomembrane formation and can cause systemic complications such as myocarditis and neuropathy. The other organisms listed cause different diseases (tetanus, streptococcal infections, and cholera, respectively).

Question 41

Which hepatitis is common in areas with poor sanitation?

Accepted Answer

Answer reason: Poor sanitation is associated with fecal-oral transmission through contaminated food and water. Hepatitis A virus (HAV) and hepatitis E virus (HEV) are primarily spread via the fecal-oral route and therefore cluster in settings with inadequate sewage treatment and unsafe drinking water. In contrast, hepatitis B and C are mainly bloodborne/sexual, and hepatitis D requires coinfection with hepatitis B.

Question 42

Salmonella typhi belongs to family?

Accepted Answer

Answer reason: Salmonella enterica serovar Typhi is a Gram-negative, facultative anaerobic bacillus classified within the Enterobacteriaceae family. This family includes many enteric pathogens (e.g., Escherichia, Klebsiella, Shigella) that share similar biochemical and structural characteristics. Streptococcaceae are Gram-positive cocci, Mycobacteriaceae are acid-fast rods, and Vibrionaceae contains curved Gram-negative rods like Vibrio cholerae, making them incorrect.

Question 43

Which virus is responsible for causing rabies?

Accepted Answer

Answer reason: Rabies is caused by rabies virus, which belongs to the genus Lyssavirus in the family Rhabdoviridae. The other listed viruses primarily cause gastrointestinal illness: norovirus causes acute gastroenteritis and rotavirus causes severe diarrhea in infants/children. "Provius" is not a recognized virus genus associated with rabies.

Question 44

Blood and mucus in stool is typical of?

Accepted Answer

Answer reason: Blood and mucus in stool indicates an inflammatory, invasive diarrhea (dysentery) with colonic mucosal invasion and ulceration. This is classically seen in bacillary dysentery due to Shigella, which causes frequent small-volume stools with blood and mucus and tenesmus. In contrast, cholera and most viral diarrheas cause watery, non-bloody diarrhea, and amoebic dysentery can also cause blood/mucus but is more often described with flask-shaped ulcers and less acute high-fever/toxicity than Shigella.

Question 45

Mantoux test is used to detect?

Accepted Answer

Answer reason: The Mantoux test (tuberculin skin test/PPD) screens for infection with Mycobacterium tuberculosis by assessing a delayed-type (type IV) hypersensitivity reaction. Induration at the injection site is measured after 48–72 hours and interpreted using risk-based cutoffs. It does not diagnose diabetes, typhoid, or malaria; those require different laboratory tests (e.g., glucose testing, Widal/blood culture, or malaria smear/rapid antigen).

Question 46

Measles is caused by which type of organism?

Accepted Answer

Answer reason: Measles is caused by the measles virus (a Morbillivirus in the Paramyxoviridae family), making it a viral infection. It spreads primarily via respiratory droplets and airborne transmission and is not treatable with antibiotics. Fungi and parasites do not cause measles, and bacteria can cause other febrile rash illnesses but not classic measles.

Question 47

BCG vaccine is given for ...?

Accepted Answer

Answer reason: BCG (Bacillus Calmette-Guérin) is a live attenuated vaccine derived from Mycobacterium bovis and is used to provide protection against tuberculosis, especially severe forms in children (e.g., TB meningitis and miliary TB). It is not a vaccine for typhoid (Typhoid conjugate/Vi vaccines) or tetanus (tetanus toxoid-containing vaccines). Dementia is not prevented by vaccination and is unrelated to BCG’s indication.

Question 48

Which of the following S. pyogenes virulence factors blocks complement activation and phagocytosis?

Accepted Answer

Answer reason: M protein is a key S. pyogenes surface virulence factor that is antiphagocytic by interfering with opsonization, including reducing complement (C3b) deposition and promoting factor H binding, which downregulates complement activation. This impairs neutrophil recognition and ingestion, helping the organism evade phagocytosis. Superantigens instead cause massive nonspecific T-cell activation and cytokine release (e.g., toxic shock-like syndrome). Streptokinase promotes fibrinolysis and tissue spread by activating plasminogen, not by blocking complement.

Question 49

Which one of the following is not a viral disease?

Accepted Answer

Answer reason: Typhoid fever is not a viral disease; it is caused by the bacterium Salmonella enterica serovar Typhi and is typically treated with appropriate antibiotics. In contrast, AIDS is caused by HIV, dengue is caused by dengue virus, and influenza is caused by influenza viruses. Therefore, typhoid is the only non-viral option listed.

Question 50

A characteristic early sign of measles seen in the mouth is?

Accepted Answer

Answer reason: Measles (rubeola) has a characteristic enanthem called Koplik spots—tiny bluish-white lesions on an erythematous base—classically found on the buccal mucosa opposite the molars. They appear early in the prodromal phase before the maculopapular rash. The other options are nonspecific oral findings and are not distinctive for measles.

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