NEET-PG 2015 - Microbiology Practice Questions

Q: Which of the following is a non-motile bacterium?

Clostridium perfringens. ***Clostridium perfringens*** - *Clostridium perfringens* is unique among the *Clostridium* species for being **non-motile**, lacking flagella. - This immotility distinguishes it from other closely related bacteria and is an important characteristic in its identification. *Vibrio* - *Vibrio* species are **highly motile**, possessing a single **polar flagellum** that enables rapid movement in liquid environments. - Their motility is crucial for their survival and pathogenesis, particularly in aquatic habitats and the human intestine. *Legionella* - *Legionella* species, including *Legionella pneumophila*, are **motile** by means of one or more **polar flagella**. - Their motility is important for disseminating within water systems and for infecting macrophages. *Clostridium septicum* - *Clostridium septicum* is a **motile** bacterium, possessing **peritrichous flagella** that allow it to move through tissues. - Its motility contributes to its ability to spread rapidly in infected hosts, often causing severe gas gangrene.

Q: Viral DNA is integrated into Bacterial DNA in:

Lysogenic cycle. ***Lysogenic cycle*** - In the **lysogenic cycle**, the **bacteriophage DNA integrates** into the host bacterial chromosome, becoming a **prophage**. - This integration allows the viral genome to be **replicated along with the host DNA** without immediately lysing the cell. *Bacterial transduction* - **Transduction** involves the transfer of **bacterial DNA** from one bacterium to another via a bacteriophage, not the integration of viral DNA into the host genome. - While phages are involved, the primary event is the accidental packaging and transfer of bacterial genes, not viral integration into the host for replication. *Bacterial transformation* - **Transformation** is the process where bacteria take up **naked DNA from their environment** and incorporate it into their own genome. - This DNA is typically from another bacterium or is artificially introduced, not viral DNA undergoing a natural integration process within the cell. *Bacterial conjugation* - **Conjugation** is the transfer of genetic material (usually a **plasmid**) between bacteria through direct cell-to-cell contact, mediated by a **pilus**. - This process involves the transfer of bacterial or plasmid DNA, not the integration of a viral genome into the host chromosome.

Q: River blindness is caused by?

Onchocerca volvulus. ***Onchocerca volvulus*** - **River blindness**, or **onchocerciasis**, is caused by the parasitic nematode *Onchocerca volvulus*. - This parasite is transmitted by the bite of infected **blackflies** (genus *Simulium*), which breed in fast-flowing rivers. *Loa loa* - *Loa loa* causes **Loiasis**, also known as African eye worm disease. - While it can manifest as an eye worm and cause itching and swelling, it does not typically lead to permanent blindness or the widespread skin lesions associated with river blindness. *Ascaris* - *Ascaris lumbricoides* causes **ascariasis**, an intestinal infection. - Symptoms are primarily gastrointestinal, such as abdominal pain, malnutrition, and, in severe cases, intestinal obstruction; it does not affect the eyes or cause blindness. *B. malayi* - *Brugia malayi* is one of the causes of **lymphatic filariasis**, also known as **elephantiasis**. - This disease primarily affects the lymphatic system, causing severe swelling in the limbs and genitals, but it does not cause blindness.

Q: Naegler's reaction is due to:

Lecithinase. ***Lecithinase*** - The **Naegler reaction** is a bacterial identification test used to detect the production of **lecithinase** (also known as alpha-toxin) by certain bacteria, particularly *Clostridium perfringens*. - This enzyme hydrolyzes **lecithin** (a lipid found in egg yolk), resulting in a visible opaque precipitate around the bacterial colonies on egg yolk agar. *Coagulase* - **Coagulase** is an enzyme produced by some bacteria (e.g., *Staphylococcus aureus*) that causes the coagulation of blood plasma. - While it is an important virulence factor, it is not involved in the **Naegler reaction**. *Hyaluronidase* - **Hyaluronidase** is an enzyme that breaks down **hyaluronic acid**, a component of connective tissue, facilitating the spread of bacteria. - It is often referred to as a **spreading factor** but is not detected by the **Naegler reaction**. *None of the options* - This option is incorrect because **Lecithinase** is directly responsible for the **Naegler reaction**.

Q: Most common route of nosocomial infection [Hospital-acquired infection]?

Direct contact. **Direct contact** - **Direct contact** with colonized or infected patients is the predominant mode of transmission for many common nosocomial pathogens like **MRSA** and **VRE**. - This often involves healthcare workers' hands becoming contaminated and then touching other patients. *Droplet transmission* - Involves the transmission of infectious agents through **respiratory droplets** produced during coughing, sneezing, or talking. - While significant for some infections (e.g., influenza, pertussis), it is not the most common route overall for nosocomial infections. *Indirect contact* - Occurs when an infectious agent is transferred via a **contaminated intermediate object** or person. - Although important (e.g., contaminated medical devices), it is generally less frequent than direct patient-to-patient transmission. *Vehicle transmission* - Involves transmission through **contaminated inanimate vehicles** like food, water, medications, or surgical instruments. - While outbreaks can occur via this route (e.g., contaminated endoscopes), it is not the most common day-to-day transmission mechanism in hospitals.

Q: All are true about anaerobic infections except:

Exudates and swabs are ideal for culture. ***Exudates and swabs are ideal for culture.*** - **Swabs exposed to air** are generally **not ideal** for anaerobic culture because oxygen exposure can kill obligate anaerobes, leading to false-negative results. - Optimal anaerobic specimen collection requires techniques that **minimize oxygen exposure**, such as aspirates or tissue biopsies placed in anaerobic transport media. *Most infections are endogenous* - Anaerobic infections commonly arise from **one's own commensal flora**, which becomes pathogenic under specific conditions like tissue damage or impaired blood supply. - These bacteria are part of the normal microbiota of various body sites, including the gastrointestinal tract, oral cavity, and skin. *Specimen for UTI is suprapubic aspiration* - For **suspected anaerobic urinary tract infections (UTIs)**, suprapubic aspiration is considered the gold standard for specimen collection. - This method bypasses potential contamination from urethral flora and ensures a sterile, oxygen-free sample for accurate anaerobic culture. *They are found normally on skin and GIT* - **Anaerobic bacteria** are a significant component of the normal flora of the **skin and gastrointestinal tract (GIT)**, as well as the oral cavity and genitourinary tract. - Their presence in these sites is crucial for maintaining normal physiological functions and preventing the overgrowth of pathogens.

Q: What is the causative agent of Izumi fever?

Yersinia pseudotuberculosis. ***Yersinia pseudotuberculosis*** - Izumi fever (also called **Far East scarlet-like fever**) is caused by Yersinia pseudotuberculosis, particularly referring to outbreaks that occurred in Japan. - This infection presents with **fever, abdominal pain, and a scarlet fever-like rash**, often mimicking appendicitis due to mesenteric lymphadenitis. - Y. pseudotuberculosis is transmitted through **contaminated food and water**, and the Izumi fever variant is characterized by systemic manifestations including erythema and desquamation. *Yersinia enterocolitica* - While this is a closely related species that also causes **gastroenteritis and mesenteric adenitis**, it is NOT the causative agent of Izumi fever. - Y. enterocolitica typically presents with diarrhea, abdominal pain, and fever, but lacks the distinctive scarlet fever-like rash seen in Izumi fever. *Pseudomonas aeruginosa* - This bacterium is an **opportunistic pathogen** often associated with nosocomial infections, especially in immunocompromised individuals. - It causes **pneumonia**, urinary tract infections, and wound infections, but not Izumi fever. *Pasteurella multocida* - This bacterium is common in the **respiratory tracts of animals**, especially cats and dogs, and is a frequent cause of wound infections from animal bites or scratches. - It typically causes localized cellulitis, abscesses, and occasionally severe infections like meningitis or osteomyelitis, not Izumi fever.

Q: What is the significance of the absence of Vi-antibody in a patient with typhoid fever?

Indicates a favorable prognosis. ***Indicates a favorable prognosis*** - The **Vi (Virulence) antigen** is a **polysaccharide capsule** that helps *Salmonella typhi* evade the immune system and is associated with **virulence** and **carrier state development**. - **Absence of Vi-antibody** indicates infection with a **less virulent strain**, successful **immune clearance**, and **lower likelihood** of developing a chronic carrier state. *Indicates a poor prognosis* - The **absence of Vi-antibody** is actually associated with **better outcomes**, not worse prognosis. - **Poor prognosis** in typhoid fever is typically related to complications like **intestinal perforation** or **septic shock**, not Vi-antibody status [1]. *No impact on prognosis* - **Vi-antibody status** is a **recognized prognostic marker** in typhoid fever and does have clinical significance. - The **presence of Vi-antibodies** may indicate **persistent infection** or **carrier state development**, making it a relevant prognostic indicator. *Suggests a negative response to treatment* - **Absence of Vi-antibody** typically indicates **successful treatment response** and **effective clearance** of the organism. - **Negative treatment response** would be evidenced by **persistent fever**, **positive cultures**, or **clinical deterioration** despite appropriate antibiotic therapy.

Q: Most common route of infection in pasteurella cellulitis -

Animal bites or scratches. ***Animal bites or scratches*** - *Pasteurella multocida* is a common commensal bacterium in the oral flora of **cats and dogs**. - **Animal bites or scratches** are the primary mode of transmission for *Pasteurella* infections, particularly cellulitis, due to direct inoculation. *Aerosols or dust* - Transmission via **aerosols or dust** is rare for *Pasteurella* infections, which typically require direct contact or inoculation. - While other bacteria can spread this way, *Pasteurella* cellulitis is not commonly acquired through airborne routes. *Contaminated tissue* - While possible in some contexts, **contaminated tissue** is not the most common route of infection for *Pasteurella* cellulitis. - Direct inoculation from an **animal's oral flora** is far more frequent than contact with contaminated environmental tissues. *Human to human* - *Pasteurella* infections are generally **not transmissible from human to human**. - The organism is primarily associated with animals and their bites or scratches.

Q: What is the most common cause of lung abscess in comatose patients?

Oral anaerobes. Oral anaerobes - **Comatose patients** are at high risk for **aspiration** of oropharyngeal flora, which predominantly consists of anaerobic bacteria. [1] - Aspiration of these organisms, especially in compromised lung tissue, frequently leads to **necrotizing pneumonia** and subsequent abscess formation. [1] *Staph aureus* - While *Staphylococcus aureus* can cause lung abscesses, particularly in the context of **hematogenous spread** (e.g., endocarditis) or nosocomial infections, it is not the most common cause in *comatose patients* who typically aspirate oral flora. [2] - *S. aureus* lung abscesses are often associated with multiple, smaller lesions rather than a single, large abscess from aspiration. *Klebsiella* - *Klebsiella pneumoniae* can cause severe, **rapidly progressive pneumonia** that may lead to abscess formation, especially in individuals with **alcoholism** or **diabetes**. - However, it is less common than oral anaerobes as the primary cause of abscess in the general population of comatose patients, whose main risk factor is aspiration of normal oral flora. [1] *Tuberculosis* - **Mycobacterium tuberculosis** can cause cavitary lung lesions, but these are typically chronic and result from primary or reactivated tuberculosis disease, not acute aspiration. [3] - Lung abscesses caused by tuberculosis are histologically distinct from pyogenic abscesses and are characterized by **granulomatous inflammation** and caseous necrosis.

Question 1

Which of the following is a non-motile bacterium?

Accepted Answer

Clostridium perfringens

Answer

Vibrio

Answer

Legionella

Answer

Clostridium septicum

Question 2

Viral DNA is integrated into Bacterial DNA in:

Accepted Answer

Lysogenic cycle

Answer

Bacterial transduction

Answer

Bacterial transformation

Answer

Bacterial conjugation

Question 3

River blindness is caused by?

Accepted Answer

Onchocerca volvulus

Answer

Loa loa

Answer

Ascaris

Answer

B. malayi

Question 4

Naegler's reaction is due to:

Accepted Answer

Lecithinase

Answer

Coagulase

Answer

Hyaluronidase

Answer

None of the options

Question 5

Most common route of nosocomial infection [Hospital-acquired infection]?

Accepted Answer

Direct contact

Answer

Droplet transmission

Answer

Indirect contact

Answer

Vehicle transmission

Question 6

All are true about anaerobic infections except:

Accepted Answer

Exudates and swabs are ideal for culture

Answer

Specimen for UTI is suprapubic aspiration

Answer

They are found normally on skin and GIT

Answer

Most infections are endogenous

Question 7

What is the causative agent of Izumi fever?

Accepted Answer

Yersinia pseudotuberculosis

Answer

Yersinia enterocolitica

Answer

Pseudomonas aeruginosa

Answer

Pasteurella multocida

Question 8

What is the significance of the absence of Vi-antibody in a patient with typhoid fever?

Accepted Answer

Indicates a favorable prognosis

Answer

Indicates a poor prognosis

Answer

No impact on prognosis

Answer

Suggests a negative response to treatment

Question 9

Most common route of infection in pasteurella cellulitis -

Accepted Answer

Animal bites or scratches

Answer

Aerosols or dust

Answer

Contaminated tissue

Answer

Human to human

Question 10

What is the most common cause of lung abscess in comatose patients?

Accepted Answer

Oral anaerobes

Answer

Staph aureus

Answer

Klebsiella

Answer

Tuberculosis

NEET-PG 2015 — Microbiology