FMGE 2019 — Microbiology
20 Previous Year Questions with Answers & Explanations
A bacterium that can thrive at temperatures around 60-70 degrees Celsius is classified as
Which of the following viruses is from the Herpes virus family?
Increased susceptibility to N. meningitidis infections is associated with deficiency of which complement component:
Molluscum contagiosum is caused by a:
Antemortem diagnosis of rabies is made with:
EBV is most strongly associated with which of the following?
What is the mode of transmission of genetic material to bacteria through bacteriophage?
A patient presented with some unknown fungal infection. Microscopic examination revealed brown coloured spherical fungi with septate hyphae. Possible condition:
The causative agent for duodenal ulcer is:
Bacillus anthracis is:
FMGE 2019 - Microbiology FMGE Practice Questions and MCQs
Question 1: A bacterium that can thrive at temperatures around 60-70 degrees Celsius is classified as
- A. Thermophilic (Correct Answer)
- B. Mesophilic
- C. Cryophilic
- D. Halophilic
Explanation: ***Thermophilic*** - **Thermophilic** bacteria are heat-loving organisms that thrive at high temperatures, typically in the range of **45°C to 80°C**, with optimal growth around 50-70°C - These organisms are commonly found in hot springs, compost heaps, and industrial processes - **Note**: Extreme thermophiles (hyperthermophiles) can grow at temperatures exceeding 80-100°C, found in hydrothermal vents and geothermal environments *Mesophilic* - **Mesophilic** bacteria grow best at moderate temperatures, typically between **20°C and 45°C** - This includes most human pathogens and bacteria found in normal body temperature environments - These organisms cannot survive the high temperatures characteristic of thermophiles *Cryophilic* - **Cryophilic** (or psychrophilic) bacteria are cold-loving organisms that thrive at low temperatures, typically **below 20°C** - These organisms are adapted to cold environments like polar regions, deep oceans, and refrigerated foods - They would be rapidly killed at thermophilic temperature ranges *Halophilic* - **Halophilic** bacteria require high concentrations of salt (NaCl) for growth - This classification is based on **salt tolerance**, not temperature preference - Halophiles can be mesophilic, thermophilic, or psychrophilic depending on their temperature requirements
Question 2: Which of the following viruses is from the Herpes virus family?
- A. Rubella
- B. EBV (Correct Answer)
- C. Rabies
- D. Measles
Explanation: ***EBV*** - **Epstein-Barr Virus (EBV)** is a member of the **Herpesviridae** family, specifically **Human Herpesvirus 4 (HHV-4)**. - It is a **DNA virus** (double-stranded DNA), which is characteristic of all herpesviruses. - It is known to cause **infectious mononucleosis** and is associated with various malignancies. *Rubella* - **Rubella virus** belongs to the family **Togaviridae** and is the causative agent of **German measles**. - It is an **RNA virus** and is not classified within the Herpesviridae family. *Rabies* - **Rabies virus** is a member of the **Rhabdoviridae** family, specifically the genus **Lyssavirus**. - It is a neurotropic **RNA virus** causing a rapidly progressive, fatal encephalitis. *Measles* - **Measles virus**, also known as **Rubeola**, belongs to the family **Paramyxoviridae**. - It is an **RNA virus** responsible for a highly contagious airborne disease.
Question 3: Increased susceptibility to N. meningitidis infections is associated with deficiency of which complement component:
- A. C1-C4 deficiency
- B. C3 deficiency
- C. C5-C9 deficiency (Correct Answer)
- D. C2 deficiency
Explanation: ***C5-C9 deficiency*** - Deficiencies in **C5-C9 components** impair the formation of the **Membrane Attack Complex (MAC)**, which is crucial for lysing Gram-negative bacteria like **N. meningitidis**. - Patients with MAC deficiencies are at significantly higher risk for recurrent invasive **N. meningitidis** infections. *C1-C4 deficiency* - Deficiencies in **C1-C4 components** primarily affect the **classical complement pathway** and are associated with increased susceptibility to **bacterial infections** and **immune complex diseases** (e.g., SLE). - While these deficiencies compromise opsonization and inflammation, they are not specifically linked to recurrent **N. meningitidis** infections. *C3 deficiency* - **C3 deficiency** is a severe primary immunodeficiency leading to profound defects in complement activation via all pathways, affecting **opsonization** and the formation of the MAC. - This deficiency causes severe recurrent **pyogenic infections** due to encapsulated bacteria but is not as specifically or commonly linked to **N. meningitidis** as deficiencies in the terminal pathway. *C2 deficiency* - **C2 deficiency** is the most common complement deficiency and primarily impacts the **classical pathway**, leading to impaired opsonization and immune complex clearance. - It is often associated with recurrent infections (especially with encapsulated bacteria) and **lupus-like syndromes**, but not specifically increased susceptibility to **N. meningitidis** infections.
Question 4: Molluscum contagiosum is caused by a:
- A. Flavi virus
- B. Adenovirus
- C. Rubivirus
- D. Pox virus (Correct Answer)
Explanation: ***Pox virus*** - **Molluscum contagiosum** is a common **cutaneous viral infection** caused by the **Molluscum Contagiosum Virus (MCV)**. - MCV belongs to the **Poxviridae family**, which are known for causing characteristic skin lesions. *Flavi virus* - **Flaviviruses** are a genus of RNA viruses, which cause diseases like **Dengue fever**, **Yellow fever**, and **Zika virus infection**. - They typically cause **systemic illnesses** with fever and rash, rather than localized skin lesions like molluscum contagiosum. *Adenovirus* - **Adenoviruses** are DNA viruses primarily associated with **respiratory infections** (e.g., common cold, bronchitis) and **conjunctivitis**. - They are not known to cause the characteristic **umbilicated papules** seen in molluscum contagiosum. *Rubivirus* - **Rubivirus** is a genus that includes the **Rubella virus**, which causes **German measles** (Rubella). - Rubella is characterized by a **maculopapular rash** and **lymphadenopathy**, which is distinct from the **umbilicated papules** seen in molluscum contagiosum.
Question 5: Antemortem diagnosis of rabies is made with:
- A. Inoculation in culture media
- B. Negri bodies in hippocampus
- C. Corneal impression smear (Correct Answer)
- D. Rabies virus specific antibodies
Explanation: ***Corneal impression smear*** - A **corneal impression smear** can detect viral antigens in the cornea using fluorescent antibody staining, a method that can be performed on living patients. - This technique provides a relatively rapid and non-invasive way to diagnose rabies **antemortem**. *Inoculation in culture media* - Rabies virus is notoriously difficult to culture in standard cell culture media, making this method impractical and unreliable for **antemortem diagnosis**. - While viral isolation is possible in specialized research settings, it is not a routine diagnostic tool for rabies in living patients. *Negri bodies in hippocampus* - **Negri bodies** are eosinophilic inclusions found in the cytoplasm of neurons, particularly in the hippocampus, which are pathognomonic for rabies. - However, their detection requires **postmortem brain tissue biopsy**, making this a **postmortem diagnostic** method, not antemortem. *Rabies virus specific antibodies* - While the presence of **rabies virus-specific antibodies** (particularly in CSF) can indicate exposure and infection, they often appear late in the disease course. - The detection of antibodies may not be reliable for early **antemortem diagnosis**, especially in naive individuals whose immune response has not yet fully developed.
Question 6: EBV is most strongly associated with which of the following?
- A. Gastric cancer
- B. Esophageal cancer
- C. Nasopharyngeal carcinoma (Correct Answer)
- D. Hepatocellular carcinoma
Explanation: ***Nasopharyngeal carcinoma*** - **Epstein-Barr virus (EBV)** is strongly and consistently associated with the development of **nasopharyngeal carcinoma**, particularly the undifferentiated (endemic) type. - EBV DNA is found in virtually **100% of undifferentiated nasopharyngeal carcinomas**, highlighting its critical role in the pathogenesis of this cancer. - This represents one of the strongest virus-cancer associations in human medicine. *Gastric cancer* - While EBV is linked to a specific subtype of **EBV-associated gastric adenocarcinoma**, it accounts for only about **10% of gastric cancers**. - This makes it a less strong and less prevalent association compared to nasopharyngeal carcinoma. *Esophageal cancer* - **Esophageal cancer** (adenocarcinoma and squamous cell carcinoma) has various risk factors such as GERD, smoking, and alcohol consumption. - **EBV is not a significant etiologic factor** for esophageal cancer. - There is no strong, consistent evidence linking EBV as a primary cause of esophageal malignancy. *Hepatocellular carcinoma* - **Hepatocellular carcinoma** is primarily associated with **hepatitis B virus (HBV)** and **hepatitis C virus (HCV)**, not EBV. - Other risk factors include chronic liver disease, cirrhosis, aflatoxin exposure, and alcohol abuse. - EBV does not play a significant role in hepatocellular carcinoma pathogenesis.
Question 7: What is the mode of transmission of genetic material to bacteria through bacteriophage?
- A. Transduction (Correct Answer)
- B. Transformation
- C. Conjugation
- D. Translation
Explanation: ***Transduction*** - **Transduction** is the process by which foreign DNA is introduced into a bacterium by a **bacteriophage** (a virus that infects bacteria). - This occurs when a bacteriophage carries bacterial DNA from one bacterium to another, often as a result of errors during viral replication. *Transformation* - **Transformation** involves the uptake of **naked DNA** from the environment by a bacterial cell. - This process does not involve a bacteriophage as an intermediary for genetic transfer. *Conjugation* - **Conjugation** is the transfer of genetic material between bacterial cells by direct cell-to-cell contact through a **pilus**. - This process requires physical contact between two bacteria and does not involve bacteriophages. *Translation* - **Translation** is the process by which messenger RNA (mRNA) is decoded to produce a specific protein. - This is a fundamental step in gene expression and is distinctly different from genetic material transmission between organisms.
Question 8: A patient presented with some unknown fungal infection. Microscopic examination revealed brown coloured spherical fungi with septate hyphae. Possible condition:
- A. Histoplasmosis
- B. Candida albicans
- C. Coccidioidomycosis
- D. Chromoblastomycosis (Correct Answer)
Explanation: ***Chromoblastomycosis*** - This infection is characterized by the presence of **sclerotic bodies** (also known as fumagoid bodies or Medlar bodies), which are **brown-pigmented**, **spherical**, copper-colored cells or muriform cells observed in tissue. - The causative fungi, often dematiaceous molds, exhibit **septate hyphae** in culture. These molds are pigmented due to melanin in their cell walls. *Histoplasmosis* - Caused by *Histoplasma capsulatum*, which appears as **small, oval, intracellular budding yeasts** within macrophages in tissue samples. - It does not typically form sclerotic bodies or prominent septate hyphae in infected tissue. *Candida albicans* - This yeast typically presents as **ovoid budding yeast cells**, pseudohyphae, and true hyphae in tissues. - It is an **achlorophyllous** fungus, meaning it lacks pigmentation and would not appear as "brown coloured" under microscopic examination. *Coccidioidomycosis* - Caused by *Coccidioides immitis* or *C. posadasii*, which are characterized by the formation of **spherules** containing endospores in tissue. - It does not form "brown coloured spherical fungi with septate hyphae" as described; spherules are large, non-pigmented, and contain smaller endospores.
Question 9: The causative agent for duodenal ulcer is:
- A. Lactobacilli
- B. E. coli
- C. H. Pylori (Correct Answer)
- D. Shigella
Explanation: ***H. pylori*** - ***H. pylori*** is a **Gram-negative spiral-shaped bacterium** that colonizes the stomach and duodenum, causing inflammation and increasing the risk of peptic ulcers, including duodenal ulcers. - It produces **urease**, which neutralizes stomach acid by converting urea to ammonia, protecting the bacteria and contributing to mucosal damage. *Lactobacilli* - **Lactobacilli** are **Gram-positive, rod-shaped bacteria** commonly found in the digestive tract and fermented foods. - They are generally considered **beneficial probiotics** and do not cause duodenal ulcers. *E. coli* - ***E. coli*** is a **Gram-negative, rod-shaped bacterium** typically found in the intestines of humans and animals. - While some strains can cause **gastrointestinal infections** (e.g., traveler's diarrhea), *E. coli* is not a known cause of duodenal ulcers. *Shigella* - **Shigella** is a **Gram-negative, rod-shaped bacterium** that causes **shigellosis**, an intestinal infection characterized by severe diarrhea (dysentery). - It primarily affects the **large intestine** and does not cause duodenal ulcers.
Question 10: Bacillus anthracis is:
- A. Gram negative cocci in cluster
- B. Gram positive rods with square ends (Correct Answer)
- C. Gram positive cocci in cluster
- D. Gram positive bacilli with spherical ends
Explanation: ***Gram positive rods with square ends*** - *Bacillus anthracis* is a **gram-positive bacterium**, meaning it retains the crystal violet stain due to its thick peptidoglycan layer. - Microscopically, it appears as **large, rod-shaped bacteria** (bacilli) with characteristic **square-cut ends**, often arranged in chains. *Gram negative cocci in cluster* - This describes organisms like **Neisseria gonorrhoeae** or **meningitidis**, which are spherical (cocci) and appear pink/red after Gram staining. - *Bacillus anthracis* is a **rod-shaped bacterium** that stains Gram-positive. *Gram positive cocci in cluster* - This morphology is characteristic of **Staphylococcus species**, which are spherical bacteria that stain purple and arrange in grape-like clusters. - *Bacillus anthracis* is a **rod-shaped bacterium**, not a coccus. *Gram positive bacilli with spherical ends* - While *Bacillus anthracis* is a **gram-positive bacillus**, its ends are distinctly **square-cut**, not spherical. - Bacteria with spherical or rounded ends would include some other *Bacillus* species or members of the **Clostridium** genus.