Which of the following statements about B. quintana is false?
Which organism can be isolated from stool & sputum?
Largest intestinal protozoan is?
Which poxvirus does not grow in eggs or animal cells?
Which virus is primarily responsible for causing Ebola virus disease, a type of hemorrhagic fever?
Which of the following is a member of the kingdom Protista?
Katayama fever is caused by which of the following?
Necrotizing fasciitis is caused by -
The gene encoding cholera toxin is carried on -
Unsegmented eggs are in which parasite?
NEET-PG 2012 - Microbiology NEET-PG Practice Questions and MCQs
Question 41: Which of the following statements about B. quintana is false?
- A. Tick is the vector (Correct Answer)
- B. Recurrence is common
- C. Causes trench fever
- D. Not detected by Weil-Felix reaction
Explanation: ***Tick is the vector*** - This statement is **false** because *Bartonella quintana* (B. quintana) is primarily transmitted by the **human body louse**, not ticks. - The disease it causes, **trench fever**, was historically associated with crowded and unsanitary conditions where lice thrive. *Causes trench fever* - *B. quintana* is the causative agent of **trench fever**, a louse-borne illness characterized by recurrent febrile episodes. - This symptom was highly prevalent among soldiers in the trenches during World War I. *Recurrence is common* - **Relapsing fever** (recurrence) is a characteristic feature of trench fever, often occurring several times over weeks or months. - This recurrence is due to the **intracellular survival of *Bartonella* species** within erythrocytes and endothelial cells, making clearance difficult. *Not detected by Weil-Felix reaction* - The **Weil-Felix reaction** is a serological test used to detect certain rickettsial infections, which cross-react with *Proteus* antigens. - *Bartonella quintana* infections **do not typically produce antibodies** that cross-react with *Proteus* antigens; therefore, the Weil-Felix test would not be positive for trench fever.
Question 42: Which organism can be isolated from stool & sputum?
- A. Fasciola
- B. P. carinii
- C. Clonorchis
- D. Paragonimus (Correct Answer)
Explanation: ***Paragonimus*** - *Paragonimus* species, particularly *P. westermani* (the **lung fluke**), are known to infest the lungs, leading to symptoms like **cough** and **sputum production**, where their eggs can be found. - While residing in the lungs, eggs can be swallowed, passed through the gastrointestinal tract, and subsequently found in **stool samples**. *Fasciola* - *Fasciola hepatica* (the **sheep liver fluke**) primarily infects the **liver and biliary ducts**. - Its eggs are typically found in **stool samples** but not in sputum, as it does not infest the respiratory tract. *Clonorchis* - *Clonorchis sinensis* (the **Chinese liver fluke**) also primarily inhabits the **bile ducts** of the liver. - Similar to *Fasciola*, its eggs are excreted in **feces** and are not found in sputum. *P. carinii* - *Pneumocystis jirovecii* (formerly *Pneumocystis carinii*) is a **fungus** that causes **pneumonia** (PCP) in immunocompromised individuals. - It is exclusively found in the **lungs** and identified in respiratory specimens like sputum or bronchoalveolar lavage, not in stool.
Question 43: Largest intestinal protozoan is?
- A. E. coli
- B. Balantidium coli (Correct Answer)
- C. Giardia
- D. T. gondii
Explanation: ***Balantidium coli*** - *Balantidium coli* is the **largest protozoan parasite** known to infect humans, specifically found in the intestines. - It causes **balantidiasis**, an intestinal infection, and is notable for its ciliated trophozoite stage. *E. coli* - *E. coli* is a **bacterium**, not a protozoan. - While it is a common inhabitant of the intestines, it is significantly smaller than parasitic protozoa. *Giardia* - *Giardia lamblia* (or *intestinalis*) is a **flagellate protozoan** that causes giardiasis. - Though an intestinal parasite, it is considerably smaller than *Balantidium coli*. *T. gondii* - *Toxoplasma gondii* is an **intracellular protozoan parasite** known for causing toxoplasmosis. - It is much smaller than *Balantidium coli* and primarily infects cells, not existing as a large free-living form in the intestine.
Question 44: Which poxvirus does not grow in eggs or animal cells?
- A. Cow pox
- B. Vaccinia
- C. Variola
- D. Molluscum contagiosum (Correct Answer)
Explanation: ***Molluscum contagiosum*** - This poxvirus is unique among human poxviruses as it **cannot be propagated in cell culture** or embryonated eggs. - It specifically replicates in **human epidermal cells**, causing characteristic skin lesions. *Cow pox* - Cowpox virus can be readily grown in **cell cultures** (e.g., Vero cells) and in **embryonated eggs**, where it produces pocks on the chorioallantoic membrane (CAM). - It is known for its ability to **infect a wide range of host cells and animals**. *Vaccinia* - Vaccinia virus is a widely studied poxvirus that grows efficiently in various **mammalian cell lines** (e.g., Hela, Vero cells) and on the **chorioallantoic membrane of embryonated eggs**. - Its broad host range and ease of culture make it a popular **viral vector** for research and vaccine development. *Variola* - Variola virus, the causative agent of smallpox, was successfully propagated in **cell cultures** (e.g., primary human embryonic kidney cells) and in **embryonated chicken eggs**, producing characteristic pock lesions. - Its ability to grow in these systems was crucial for **vaccine production** and research before its eradication.
Question 45: Which virus is primarily responsible for causing Ebola virus disease, a type of hemorrhagic fever?
- A. Ebola virus (Correct Answer)
- B. Phlebovirus
- C. West Nile virus
- D. None of the options
Explanation: ***Ebola virus*** - The disease is named after the **Ebola River** in Congo, where it was first identified. - The **Ebola virus** is a member of the **Filoviridae family**, known for causing severe hemorrhagic fevers. *West Nile virus* - This virus is primarily transmitted by **mosquitoes** and causes **West Nile fever**, which can lead to neurological disease. - It does not cause the hemorrhagic fever associated with Ebola virus disease. *Phlebovirus* - **Phlebovirus** is a genus of viruses that includes several species capable of causing **encephalitis** or **febrile illness** with headache and myalgia. - While some can cause hemorrhagic fevers, it is not the primary agent for the disease specifically known as **Ebola virus disease**. *None of the options* - This option is incorrect because the **Ebola virus** is indeed listed as an option and is the correct pathogen responsible for Ebola virus disease.
Question 46: Which of the following is a member of the kingdom Protista?
- A. Fungi
- B. Protozoa (Correct Answer)
- C. Bacteria
- D. Virus
Explanation: ***Protozoa*** - **Protozoa** are single-celled eukaryotic organisms that are heterotrophic and typically motile, fitting the classification within the kingdom Protista. - Protista is a **diverse kingdom** encompassing various eukaryotic organisms that are not animals, plants, or fungi, and protozoa represent the animal-like protists. - Examples include **Amoeba, Plasmodium, Giardia**, and Entamoeba. *Virus* - **Viruses** are not classified within any kingdom as they are **acellular** (not made of cells). - They are obligate intracellular parasites that require a host cell to replicate. - Lack cellular machinery and metabolic processes that define living organisms. *Fungi* - **Fungi** belong to their own distinct kingdom, Fungi, and are not classified under Protista. - They are **heterotrophic eukaryotes** that absorb nutrients and have cell walls made of chitin. - Examples include yeasts, molds, and mushrooms. *Bacteria* - **Bacteria** are prokaryotic organisms, meaning they lack a membrane-bound nucleus and other membrane-bound organelles. - They belong to the kingdom **Monera** (or domain Bacteria in modern classification), separate from eukaryotic kingdoms like Protista. - They have peptidoglycan cell walls and reproduce by binary fission.
Question 47: Katayama fever is caused by which of the following?
- A. F. hepatica
- B. C. sinensis
- C. A. lumbricoides
- D. S. japonicum (Correct Answer)
Explanation: ***Correct: S. japonicum*** - Katayama fever, also known as **acute schistosomiasis**, is a systemic hypersensitivity reaction to the migrating schistosomula and oviposition of eggs that primarily occurs in infections with **_Schistosoma japonicum_** or _S. mansoni_. - It presents with fever, chills, cough, diarrhea, abdominal pain, hepatosplenomegaly, and eosinophilia, typically 2-8 weeks after exposure to contaminated water. - S. japonicum tends to cause the most severe form of Katayama fever. *Incorrect: F. hepatica* - **_Fasciola hepatica_** causes fascioliasis, an infection of the bile ducts and liver, which can present with fever and eosinophilia, but it does not typically cause the acute systemic reaction known as Katayama fever. - The disease is usually acquired by ingesting **metacercariae** on aquatic vegetation or in contaminated water. *Incorrect: C. sinensis* - **_Clonorchis sinensis_** is the Chinese liver fluke, causing clonorchiasis, an infection primarily of the bile ducts. - Symptoms are often mild or asymptomatic but can include abdominal pain, indigestion, diarrhea, and jaundice in heavy infections, without the distinct acute systemic syndrome of Katayama fever. *Incorrect: A. lumbricoides* - **_Ascaris lumbricoides_** is a roundworm that causes ascariasis, primarily affecting the gastrointestinal tract. - While it can cause pulmonary symptoms during larval migration (Löffler's syndrome), it does not cause Katayama fever, which is specific to schistosomiasis.
Question 48: Necrotizing fasciitis is caused by -
- A. Beta hemolytic streptococci (Correct Answer)
- B. Pneumococcus
- C. Staphylococcus aureus
- D. Clostridium perfringens
Explanation: ***Beta hemolytic streptococci*** - **Group A Streptococcus (GAS)**, specifically *Streptococcus pyogenes*, is the most common cause of **Type II necrotizing fasciitis**. - Its virulence factors, like **exotoxins**, contribute to rapid tissue destruction and systemic toxicity. *Staphylococcus aureus* - While *S. aureus* can cause severe skin and soft tissue infections, it is more commonly associated with **cellulitis**, **abscesses**, and **septic arthritis**. - It can be a co-pathogen in **polymicrobial (Type I) necrotizing fasciitis** but is less frequent as a sole cause compared to GAS for Type II. *Pneumococcus* - *Streptococcus pneumoniae* (Pneumococcus) is primarily known for causing respiratory infections like **pneumonia**, **otitis media**, and **meningitis**. - It is not a typical causative agent of necrotizing fasciitis. *Clostridium perfringens* - This bacterium is the primary cause of **gas gangrene** (clostridial myonecrosis), a severe form of necrotizing soft tissue infection involving muscle tissue. - While also a flesh-eating bacterium, its clinical presentation and typical affected tissues differ from those of necrotizing fasciitis caused by streptococci.
Question 49: The gene encoding cholera toxin is carried on -
- A. Chromosomal DNA
- B. Extrachromosomal plasmid
- C. Bacteriophage (Correct Answer)
- D. Transposon
Explanation: ***Bacteriophage*** - The gene encoding **cholera toxin (ctxA and ctxB)** is carried on the genome of a **lysogenic bacteriophage** known as CTXf. - This phage integrates its DNA into the *Vibrio cholerae* chromosome, allowing for toxin production. *Chromosomal DNA* - While the **phage DNA (containing the cholera toxin gene)** integrates into the *Vibrio cholerae* chromosome, the toxin itself is **not directly encoded by the core bacterial chromosomal DNA** but by the integrated phage DNA. - Many bacterial virulence factors are encoded on the main chromosome, but cholera toxin is a specific exception. *Extrachromosomal plasmid* - **Plasmids** are extrachromosomal DNA molecules that can carry virulence genes, but the cholera toxin gene is **not typically found on a plasmid** in *Vibrio cholerae*. - Examples of plasmid-encoded toxins include some enterotoxins in *E. coli*. *Transposon* - **Transposons** are "jumping genes" that can move within and between DNA molecules, but they are generally **mobile genetic elements** that carry genes, not the direct source of the cholera toxin gene. - While transposons can sometimes contribute to the movement of virulence genes, the cholera toxin gene specifically originates from a bacteriophage.
Question 50: Unsegmented eggs are in which parasite?
- A. Ancylostoma
- B. Necator americanus
- C. Dracunculus
- D. Trichuris trichiura (Correct Answer)
Explanation: ***Trichuris trichiura*** - *Trichuris trichiura* (whipworm) eggs are typically **unembryonated** or **unsegmented** when passed in feces. - Upon defecation, the eggs require a period of **development in soil** to become infective. *Ancylostoma* - **Hookworm (Ancylostoma)** eggs are typically **segmented** (possessing a 2-8 cell stage) when passed in feces. - They develop into **rhabditiform larvae** in the soil. *Necator americanus* - **Hookworm (Necator americanus)** eggs are also typically **segmented** (possessing a 2-8 cell stage) when passed in feces. - Like *Ancylostoma*, they require further development in soil to become infective. *Dracunculus* - *Dracunculus medinensis* (Guinea worm) does not lay eggs; instead, it releases **larvae** from the skin blister of the host into water. - The larvae are then ingested by **cyclops** (copepods) to continue their life cycle.