Microbiology
10 questionsThe fungus with septate hyphae and dichotomous branching is?
In a patient presenting with respiratory symptoms, acute angled septate hyphae are seen in which of the following fungi?
Which of the following statements about Penicillium marneffei is incorrect?
Color of granules in mycetoma caused by Actinomadura pelletierrii -
Which of the following conditions is NOT caused by Aspergillus?
Which of the following is a cause of Valley fever (desert rheumatism)?
Most common type of HPV associated with cervical cancer?
A plant prick can produce sporotrichosis. Which of the following statements about sporotrichosis is false?
Which of the following statements about viruses is false?
Which is not a DNA virus?
NEET-PG 2013 - Microbiology NEET-PG Practice Questions and MCQs
Question 671: The fungus with septate hyphae and dichotomous branching is?
- A. Aspergillus (Correct Answer)
- B. Penicillium
- C. Mucor
- D. Rhizopus
Explanation: ***Aspergillus*** - *Aspergillus* species are characterized by their **septate hyphae** and **acute-angle branching** (branching at approximately 45-degree angles), which are key distinguishing features in histopathology. - This branching pattern is sometimes referred to as "dichotomous branching" in medical literature, though true dichotomous branching is more characteristic of certain tissue forms. - This fungal morphology is often seen in infections such as **invasive aspergillosis** in immunocompromised patients. *Penicillium* - *Penicillium* also has **septate hyphae**, but its branching pattern is typically *not acute-angled or dichotomous*. - It is more commonly known for its **brush-like** conidiophores (penicillus) in culture rather than distinctive tissue branching patterns. *Mucor* - *Mucor* is a type of **zygomycete** (now classified under Mucorales) and is characterized by **aseptate or sparsely septate hyphae** with **irregular, right-angle branching**. - This is a key histological feature distinguishing it from *Aspergillus* in cases of **mucormycosis**. *Rhizopus* - Similar to *Mucor*, *Rhizopus* is also a zygomycete with **aseptate or sparsely septate hyphae** and **irregular, wide-angle branching**. - It is often identified in culture by the presence of **rhizoids** (root-like structures) and sporangiophores.
Question 672: In a patient presenting with respiratory symptoms, acute angled septate hyphae are seen in which of the following fungi?
- A. Aspergillus (Correct Answer)
- B. Mucor
- C. Penicillium
- D. Candida
Explanation: ***Aspergillus*** - *Aspergillus* species are characterized by their distinctive **acute-angled (dichotomous) septate hyphae** when observed microscopically in tissue sections or clinical samples. - This morphological feature is crucial for differentiating *Aspergillus* infections, such as **aspergillosis**, from other fungal infections. *Mucor* - *Mucor* (along with *Rhizopus* and *Lichtheimia*) belongs to the Zygomycetes class, which are characterized by **broad, non-septate, ribbon-like hyphae** with irregular branching, not acute-angled septate hyphae. - These fungi are associated with **mucormycosis**, often seen in immunocompromised patients, particularly those with diabetes. *Penicillium* - *Penicillium* is a common mold known for producing penicillin and typically appears as **septate hyphae** but is more often recognized by its branching, brush-like conidiophores (penicilli) in culture rather than a distinct acute-angled septate hyphal morphology in clinical samples causing invasive disease. - While it can cause opportunistic infections, its hyphae are less commonly described as having uniquely acute angles compared to *Aspergillus*. *Candida* - *Candida* species are typically observed as **yeast cells (oval budding forms)**, often forming **pseudohyphae** (elongated yeast cells that remain attached) or true hyphae under specific conditions, but not as acute-angled septate hyphae. - *Candida* is a common cause of superficial and invasive candidiasis, and its microscopic appearance is distinct from filamentous fungi.
Question 673: Which of the following statements about Penicillium marneffei is incorrect?
- A. Forms black colonies (Correct Answer)
- B. Is a dimorphic fungus
- C. Amphotericin B is used for treatment
- D. Causes severe infections in immunocompromised patients
Explanation: ***Forms black colonies*** - *Penicillium marneffei* typically forms colonies that are often **reddish-beige** or **pigmented red-diffusible**, not black. - The production of a characteristic **red-to-burgundy pigment** is a key identifying feature of this fungus, especially in culture. *Is a dimorphic fungus* - This statement is correct. *Penicillium marneffei* is a **thermally dimorphic fungus**, meaning it grows as a mould at 25°C (room temperature) and as yeast-like cells at 37°C (body temperature). - This dimorphism is crucial for its pathogenesis and identification. *Amphotericin B is used for treatment* - This statement is correct. **Amphotericin B** is a commonly used antifungal agent for the treatment of severe *Penicillium marneffei* infections, particularly in immunocompromised patients. - It is often followed by a maintenance regimen with an azole antifungal like itraconazole. *Causes severe infections in immunocompromised patients* - This statement is correct. *Penicillium marneffei* is an **opportunistic pathogen** that primarily causes severe, disseminated infections in individuals with compromised immune systems, especially those with HIV/AIDS. - Endemic regions include Southeast Asia, where it is a leading cause of systemic mycosis in HIV-positive patients.
Question 674: Color of granules in mycetoma caused by Actinomadura pelletierrii -
- A. Black
- B. Yellow
- C. Red (Correct Answer)
- D. Brown
Explanation: ***Red*** - *Actinomadura pelletierrii* is a common cause of **actinomycetoma** and is characterized by producing **red granules** in the lesions. - The color of these granules is a key diagnostic feature, helping differentiate it from other causes of mycetoma. *Black* - **Black granules** are typically associated with **eumycetoma** caused by **dematiaceous fungi** such as *Madurella mycetomatis*. - This color indicates the presence of **melanin**, a pigment produced by these fungal species. *Yellow* - **Yellow granules** are commonly seen in actinomycetoma caused by organisms such as *Nocardia brasiliensis* or sometimes *Actinomadura madurae*. - This color helps differentiate these specific actinomycetes from other types that produce different granule colors. *Brown* - While varying shades of color can occur, **brown granules** are not the characteristic color produced by *Actinomadura pelletierrii*. - Some *Streptomyces* species or certain eumycetoma agents can occasionally produce brownish granules, but red is specific for *A. pelletierrii*.
Question 675: Which of the following conditions is NOT caused by Aspergillus?
- A. Otomycosis
- B. Dermatophytosis (Correct Answer)
- C. Allergic sinusitis
- D. Bronchopulmonary allergy
Explanation: ***Dermatophytosis*** - This condition is caused by **dermatophytes** (e.g., *Trichophyton*, *Microsporum*, *Epidermophyton*), which are a specific group of fungi that metabolize keratin. - *Aspergillus* species are generally **opportunistic molds** but do not typically cause dermatophytosis, which is a superficial fungal infection of the skin, hair, or nails. *Otomycosis* - **Otomycosis** is a fungal infection of the external ear canal, and *Aspergillus* species are a common cause, particularly *Aspergillus niger*. - It can lead to ear pain, discharge, itching, and hearing impairment. *Allergic sinusitis* - **Allergic fungal sinusitis (AFS)** is a common form of fungal sinusitis where *Aspergillus* species are significant contributors, often leading to a thick, tenacious allergic mucin. - This condition is an IgE-mediated hypersensitivity reaction to the fungal elements in the nasal and sinus cavities. *Bronchopulmonary allergy* - **Allergic bronchopulmonary aspergillosis (ABPA)** is a hypersensitivity reaction to *Aspergillus fumigatus* antigens that colonize the airways, particularly in individuals with asthma or cystic fibrosis. - It results in recurrent episodes of wheezing, cough, and transient pulmonary infiltrates, and can lead to bronchiectasis if left untreated.
Question 676: Which of the following is a cause of Valley fever (desert rheumatism)?
- A. Sporothrix
- B. Cladosporium
- C. Phialophora
- D. Coccidioides (Correct Answer)
Explanation: ***Coccidioides*** - **Valley fever**, or desert rheumatism, is caused by infection with the dimorphic fungus **Coccidioides**, primarily **Coccidioides immitis** and **Coccidioides posadasii**. - This fungus is endemic to arid and semi-arid regions, especially the **southwestern United States** and parts of Central and South America. *Sporothrix* - **Sporothrix schenckii** causes sporotrichosis, a chronic fungal infection typically involving the skin, subcutaneous tissue, and adjacent lymphatics, often through skin trauma. - It does not cause Valley fever. *Cladosporium* - **Cladosporium** species are ubiquitous molds commonly found in outdoor and indoor environments, often associated with allergic reactions and occasionally superficial infections. - They are not a cause of Valley fever. *Phialophora* - **Phialophora** species are dematiaceous fungi that can cause phaeohyphomycosis, chromoblastomycosis, and eumycetoma, which are subcutaneous or systemic fungal infections. - They are not associated with Valley fever.
Question 677: Most common type of HPV associated with cervical cancer?
- A. 6, 11
- B. 5, 8
- C. 16, 18 (Correct Answer)
- D. 6, 8
Explanation: ***16, 18*** - **HPV types 16 and 18** are considered **high-risk HPV types** and are responsible for approximately **70% of all cervical cancer cases** globally. - These types produce **oncoproteins E6 and E7** that interfere with tumor suppressor genes (p53 and Rb), leading to uncontrolled cell growth and malignancy. *6, 11* - **HPV types 6 and 11** are considered **low-risk HPV types** and are primarily associated with **genital warts (condyloma acuminata)**. - While they can cause benign lesions, they are **rarely associated with cervical cancer**. *5, 8* - **HPV types 5 and 8** are **cutaneous HPV types** primarily associated with **epidermodysplasia verruciformis**, a rare genetic condition predisposing to skin cancers. - These types affect the **skin** and are **not associated with cervical cancer**, making them incorrect for this question. *6, 8* - This combination includes **HPV 6**, which is a **low-risk type** primarily associated with genital warts. - **HPV 8** is a cutaneous type associated with skin lesions, not cervical cancer. - This pairing does not represent the most common types responsible for cervical cancer.
Question 678: A plant prick can produce sporotrichosis. Which of the following statements about sporotrichosis is false?
- A. Enlarged lymph nodes extending centripetally as a beaded chain are a characteristic finding
- B. Most cases are acquired via cutaneous inoculation
- C. It is an occupational disease of butchers, doctors (Correct Answer)
- D. Is a chronic mycotic disease that typically involves skin, subcutaneous tissue and regional lymphatics
Explanation: ***It is an occupational disease of butchers, doctors*** - Sporotrichosis is an **occupational hazard for gardeners, florists, and agricultural workers** due to exposure to decaying plant matter, not typically for butchers or doctors. - The disease is caused by **direct inoculation** of the fungus *Sporothrix schenckii* into the skin, often through a thorn prick or minor trauma. *Most cases are acquired via cutaneous inoculation* - This statement is **true** as sporotrichosis is primarily caused by **traumatic implantation** of fungal spores into the skin. - Common sources include **thorns, splinters, sphagnum moss**, and other plant materials. *Enlarged lymph nodes extending centripetally as a beaded chain are a characteristic finding* - This statement is **true** and describes the classic **lymphocutaneous sporotrichosis**, where lesions and **nodular lymphangitis** track along lymphatic channels. - The "beaded chain" appearance refers to the multiple subcutaneous nodules formed along the lymphatic vessels. *Is a chronic mycotic disease that typically involves skin, subcutaneous tissue and regional lymphatics* - This statement is **true** because sporotrichosis is a **slow-progressing fungal infection** that primarily affects the skin, the tissue just beneath the skin, and the lymphatics draining the infected area. - While systemic dissemination can occur in immunocompromised individuals, the **cutaneous and lymphocutaneous forms** are most common.
Question 679: Which of the following statements about viruses is false?
- A. Viruses contain nucleic acid.
- B. Viruses lack mitochondria.
- C. Viruses are capable of independent motility. (Correct Answer)
- D. Viruses lack ribosomes.
Explanation: ***Viruses are capable of independent motility.*** - Viruses are **acellular infectious agents** and lack the cellular machinery required for independent movement or motility. - They rely on host cell processes or environmental factors for their dissemination and entry into cells. *Viruses lack ribosomes.* - Viruses are **obligate intracellular parasites**; they lack ribosomes and other cellular organelles necessary for protein synthesis. - They hijack the host cell's ribosomes and metabolic machinery to replicate their genetic material and produce viral proteins. *Viruses lack mitochondria.* - Viruses lack mitochondria, as they are **not capable of generating their own ATP** through cellular respiration. - They depend on the host cell's energy-generating systems to provide the ATP required for their replication cycle. *Viruses contain nucleic acid.* - All viruses contain a **nucleic acid genome**, which can be either DNA or RNA. - This genetic material carries the instructions for viral replication and is enclosed within a protein coat called a **capsid**.
Question 680: Which is not a DNA virus?
- A. Rhabdovirus (Correct Answer)
- B. Poxvirus
- C. Papovavirus
- D. Parvovirus
Explanation: ***Rhabdovirus*** - Rhabdoviruses, such as the rabies virus, are characterized by their **single-stranded RNA genome** and distinctive bullet-shaped morphology. - They replicate in the cytoplasm of infected cells, using their **RNA-dependent RNA polymerase** to transcribe their genome. *Papovavirus* - Papovaviruses (now split into Papillomaviridae and Polyomaviridae) are **DNA viruses** known for causing warts and some cancers. - They possess a small, **double-stranded, circular DNA genome**. *Poxvirus* - Poxviruses are large, complex **DNA viruses** that replicate entirely within the cytoplasm of the host cell. - They have a **double-stranded DNA genome** and are notable for causing diseases like smallpox and molluscum contagiosum. *Parvovirus* - Parvoviruses are among the smallest viruses, characterized by their **single-stranded DNA genome**. - They require actively dividing host cells to replicate their **linear DNA**.