Infective form of Hookworms?
Cutaneous larva migrans is due to ?
What type of spore is produced by Ascomycota during sexual reproduction?
The 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?
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?
NEET-PG 2013 - Microbiology NEET-PG Practice Questions and MCQs
Question 51: Infective form of Hookworms?
- A. Egg
- B. Rhabditiform larva
- C. Filariform larva (Correct Answer)
- D. Adult worm
Explanation: ***Filariform larva*** - The **filariform larva (L3)** is the infective stage of hookworms, capable of penetrating intact skin. - Upon penetration, these larvae migrate through the bloodstream to the lungs, then up the bronchial tree to be swallowed, eventually maturing in the intestines. *Egg* - Hookworm **eggs** are passed in the feces of infected individuals and are not infective to humans directly. - They require favorable conditions (warm, moist soil) to embryonate and hatch into rhabditiform larvae. *Rhabditiform larva* - The **rhabditiform larva (L1)** is the first larval stage that hatches from the egg in the soil. - It is a non-infective, free-living stage that feeds on bacteria and molts twice to become the infective filariform larva. *Adult worm* - **Adult worms** reside in the small intestine of the host and are not the infective form. - They attach to the intestinal mucosa and feed on blood, causing the characteristic anemia associated with hookworm infection.
Question 52: Cutaneous larva migrans is due to ?
- A. W.bancrofti
- B. B. Malayi
- C. D. medinensis
- D. Ancylostoma braziliense (Correct Answer)
Explanation: ***Ancylostoma braziliense*** - **Cutaneous larva migrans** is primarily caused by the larvae of **dog and cat hookworms**, especially *Ancylostoma braziliense*. - Humans become **accidental hosts** when these larvae penetrate the skin but cannot complete their life cycle, leading to **serpiginous tracks**. *W. bancrofti* - This parasite, **Wuchereria bancrofti**, is a filarial nematode that causes **lymphatic filariasis** (elephantiasis). - Its effects are characterized by **lymphedema** and **hydrocele**, not migrating skin lesions. *B. Malayi* - **Brugia malayi** is another filarial nematode responsible for **lymphatic filariasis** in humans, similar to *W. bancrofti*. - It primarily causes **swelling of the limbs** and scrotum, not cutaneous larva migrans. *D. medinensis* - **Dracunculus medinensis** is the parasite that causes **dracunculiasis**, also known as **Guinea worm disease**. - This infection is characterized by a **painful blister** and subsequent emergence of the adult worm, which is distinct from creeping eruptions.
Question 53: What type of spore is produced by Ascomycota during sexual reproduction?
- A. Asexual spores
- B. Ascospores (Correct Answer)
- C. Conidia
- D. None of the options
Explanation: ***Ascospores*** - **Ascospores** are the sexual spores produced by fungi belonging to the phylum **Ascomycota** during their sexual reproductive cycle. - These spores are formed inside a sac-like structure called an **ascus** after **karyogamy (nuclear fusion)** and **meiosis**. - Each ascus typically contains **4-8 ascospores** arranged in a characteristic pattern. - Examples of Ascomycota include *Aspergillus*, *Penicillium*, *Candida*, and yeasts like *Saccharomyces*. *Asexual spores* - **Asexual spores** are produced during **asexual reproduction** without the fusion of gametes or meiosis. - Examples include **conidia** and **sporangiospores**, which allow for rapid proliferation and dispersal. *Conidia* - **Conidia** are a specific type of **asexual spore**, not sexual spores. - They are formed exogenously on specialized structures called **conidiophores**. - While Ascomycota can produce conidia asexually, the question asks specifically about sexual reproduction. *None of the options* - This option is incorrect because **ascospores** are indeed the sexual spores of Ascomycota.
Question 54: 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 55: 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 56: 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 57: 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 58: 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 59: 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 60: 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.