Community Medicine
1 questionsPneumonic plague is spread by:
NEET-PG 2015 - Community Medicine NEET-PG Practice Questions and MCQs
Question 591: Pneumonic plague is spread by:
- A. Direct contact with infected tissue
- B. Bite of infected flea
- C. Ingestion of contaminated food
- D. Droplet infection (Correct Answer)
Explanation: ***Correct: Droplet infection*** - Pneumonic plague is a severe form of plague that affects the **lungs** and is transmitted through **respiratory droplets** expelled by an infected person or animal during coughing or sneezing. - This direct person-to-person transmission distinguishes it from other forms of plague. - It is the **only form of plague** that can spread directly from human to human without an animal or flea vector. *Incorrect: Bite of infected flea* - This is the primary mode of transmission for **bubonic plague**, where the bacterium *Yersinia pestis* is transmitted from rodents to humans via infected fleas. - While bubonic plague can progress to pneumonic plague, the initial transmission route for the pneumonic form itself is not flea bites. *Incorrect: Direct contact with infected tissue* - Direct contact with infected tissues or fluids can lead to **septicemic plague** or sometimes bubonic plague, especially in cases where there is a break in the skin. - This is not the typical or primary route for the spread of pneumonic plague, which is respiratory. *Incorrect: Ingestion of contaminated food* - Ingestion of contaminated food or water is a route for various **gastrointestinal infections** and diseases like salmonella or cholera. - It is not a known or common method for the transmission of any form of plague, including pneumonic plague.
Internal Medicine
2 questionsWhat is the most common form of leptospirosis?
What is the causative agent of trench fever?
NEET-PG 2015 - Internal Medicine NEET-PG Practice Questions and MCQs
Question 591: What is the most common form of leptospirosis?
- A. Icteric form
- B. Hepatorenal form
- C. Anicteric form (Correct Answer)
- D. Weil's disease
Explanation: ***Anicteric form*** - The **anicteric form** accounts for about 90% of all leptospirosis cases, presenting with milder, flu-like symptoms without jaundice. - Patients typically experience **fever, headache, myalgia**, and conjunctival suffusion during the initial septicemic phase [1], followed by an immune phase that can involve meningitis or uveitis [1]. *Icteric form* - The **icteric form** (Weil's disease) is a severe manifestation, characterized by jaundice, renal failure, and hemorrhage, occurring in a minority of cases (5-10%). - Although more severe and often life-threatening, it is **less common** than the anicteric presentation [1]. *Hepatorenal form* - This term describes the severe complications of leptospirosis, including **liver and kidney dysfunction**, specifically associated with Weil's disease. - While a critical aspect of severe leptospirosis, it is a description of the organ involvement rather than a distinct common form of the disease. *Weil's disease* - **Weil's disease** is the most severe and potentially fatal form of leptospirosis, characterized by **jaundice, renal failure, hemorrhage, and myocarditis**. - It is a severe subset of the icteric form, making it a very serious but **uncommon variant** of the overall disease.
Question 592: What is the causative agent of trench fever?
- A. Q-fever
- B. Boutonneuse fever
- C. Indian tick typhus
- D. Bartonella quintana (Correct Answer)
Explanation: ***Bartonella quintana*** - **Trench fever** is a **rickettsial-like illness** primarily transmitted by the human body louse. - The causative agent is the bacterium **Bartonella quintana**, which causes recurrent fever, headache, and body pains. *Q-fever* - Q-fever is caused by the bacterium **Coxiella burnetii** and is typically transmitted through airborne exposure to contaminated aerosols from infected animals. - It presents with fever, headache, and atypical pneumonia, and is not associated with human body lice. *Boutonneuse fever* - This fever is caused by **Rickettsia conorii**, transmitted by the **brown dog tick**. - Characterized by a **maculopapular rash** and an **eschar (tache noire)** at the site of the tick bite. *Indian tick typhus* - This is a form of spotted fever group rickettsiosis caused by **Rickettsia conorii subspecies indica**, transmitted by ticks [1]. - It presents with fever, rash, and an eschar, similar to boutonneuse fever, but is specified for the Indian subcontinent [1].
Microbiology
7 questionsBrill-Zinsser disease is a recrudescent form of which infection?
Listeria escapes from phagosomes (phagolysosomes) due to:
Which bacteria can grow even in the presence of antiseptics?
A chronic alcoholic is presenting with clinical features of meningitis. Most likely organism to grow on CSF culture:
Bartonella quintana causes:
Which immunoglobulin does Protein A of Staphylococcus aureus bind to?
Which type of DNase produced by Streptococcus is known to be the most antigenic in humans?
NEET-PG 2015 - Microbiology NEET-PG Practice Questions and MCQs
Question 591: Brill-Zinsser disease is a recrudescent form of which infection?
- A. Recrudescence of R prowazekii infection (Correct Answer)
- B. Recrudescence of R typhi infection
- C. None of the options
- D. Recrudescence of Coxiella burnetii infection
Explanation: **Recrudescence of R prowazekii infection** - Brill-Zinsser disease is a **late-onset complication** of **epidemic typhus**, caused by *Rickettsia prowazekii*. - It occurs years after the initial infection, due to **reactivation of dormant bacteria** in the body. *Recrudescence of R typhi infection* - *Rickettsia typhi* causes **murine typhus**, but its recrudescent form is not referred to as Brill-Zinsser disease. - Murine typhus is typically a **milder disease** compared to epidemic typhus. *Recrudescence of Coxiella burnetii infection* - *Coxiella burnetii* causes **Q fever**, which can have a chronic form but is not a recrudescence of a typhus infection. - Q fever presents with different clinical manifestations, such as **endocarditis** or **hepatitis**, not typically a rash or neurological symptoms seen in typhus. *None of the options* - This option is incorrect because the specific recrudescent form described in the question clearly points to *Rickettsia prowazekii*.
Question 592: Listeria escapes from phagosomes (phagolysosomes) due to:
- A. Opacity associated protein (OAP)
- B. Caspases
- C. Cell membrane adhesion molecules
- D. beta-hemolysin (Correct Answer)
Explanation: ***beta-hemolysin*** - *Listeria monocytogenes* produces **listeriolysin O (LLO)**, a **beta-hemolysin**, which is a pore-forming toxin that lyses the phagosomal membrane. - This allows the bacteria to escape into the host cell cytoplasm, thus **avoiding destruction** by lysosomal enzymes and neutralizing the microbicidal environment. *Caspases* - **Caspases** are a family of proteases that play essential roles in programmed cell death (apoptosis) and inflammation. - While bacteria can manipulate host cell apoptosis, caspases themselves are **host enzymes** and do not directly confer resistance to phagosome destruction. *Cell membrane adhesion molecules* - **Adhesion molecules** facilitate bacterial attachment to host cells and internalisation, but they do not directly provide a mechanism for **escaping the phagosome** once internalised. - Examples include internalins, which are involved in bacterial entry into cells. *Opacity associated protein (OAP)* - **Opacity associated proteins (OAPs)** are primarily associated with *Neisseria gonorrhoeae* and are involved in adherence to host cells and evasion of the immune response. - They are not a mechanism for **phagosomal escape** or directly related to *Listeria's* intracellular survival.
Question 593: Which bacteria can grow even in the presence of antiseptics?
- A. Staphylococcus
- B. Streptococcus
- C. E. coli
- D. Pseudomonas (Correct Answer)
Explanation: ***Pseudomonas*** - **Pseudomonas aeruginosa** is unique among common bacteria in its ability to not just survive but actually **grow in the presence of antiseptics**. - It can multiply in **quaternary ammonium compounds**, **chlorhexidine solutions**, and even **distilled water** due to minimal nutritional requirements. - Resistance mechanisms include **efflux pumps**, **biofilm formation**, and **low outer membrane permeability** that exclude many antiseptic agents. - This characteristic makes it a notorious cause of **hospital-acquired infections** and contaminant of disinfectant solutions. *Staphylococcus* - While some strains like **MRSA (methicillin-resistant Staphylococcus aureus)** are resistant to many antibiotics, they are generally **susceptible to common antiseptics**. - Standard antiseptics like alcohols, iodophors, and chlorhexidine effectively kill Staphylococcus species. *Streptococcus* - **Streptococcus species** are generally **susceptible to most common antiseptics and disinfectants**. - They are known for causing infections like strep throat and cellulitis but do not exhibit antiseptic resistance. *E. coli* - **Escherichia coli** is typically **susceptible to standard antiseptic agents**. - While some strains can be antibiotic-resistant, their resistance mechanisms do not generally extend to antiseptics, unlike **Pseudomonas**.
Question 594: A chronic alcoholic is presenting with clinical features of meningitis. Most likely organism to grow on CSF culture:
- A. Streptococcus pneumoniae (Correct Answer)
- B. Neisseria meningitidis
- C. Escherichia coli
- D. Listeria monocytogenes
Explanation: ***Streptococcus pneumoniae*** - **Chronic alcoholism** is a significant risk factor for **pneumococcal infections**, including meningitis, due to impaired immune function. - **S. pneumoniae** is the most common cause of **bacterial meningitis** in adults, especially in those with underlying conditions like alcoholism. *Neisseria meningitidis* - While a common cause of meningitis, especially in **young adults** and crowded settings, it is not specifically associated with chronic alcoholism as a primary risk factor like *S. pneumoniae*. - **Meningococcal meningitis** often presents with a **petechial rash**, which is not mentioned in the clinical scenario. *Escherichia coli* - **E. coli meningitis** primarily affects **neonates** and **elderly** or immunocompromised individuals, usually associated with healthcare-acquired infections. - It is not a typical cause of community-acquired meningitis in an otherwise healthy adult alcoholic. *Listeria monocytogenes* - **Listeria monocytogenes** is a known cause of meningitis in **immunocompromised individuals**, **neonates**, and **elderly** people, often linked to contaminated food. - While chronic alcoholism does impair immunity, *S. pneumoniae* is a more frequently encountered pathogen in this specific population for meningitis.
Question 595: Bartonella quintana causes:
- A. Trench fever (Correct Answer)
- B. Scrub typhus
- C. Epidemic typhus
- D. Endemic typhus
Explanation: ***Trench fever*** - **Bartonella quintana** is the causative agent of **trench fever**, a louse-borne disease historically common during wartime. - Symptoms include **recurrent fevers**, headache, bone pain (especially in the shins), and rash. *Scrub typhus* - Scrub typhus is caused by **Orientia tsutsugamushi**, a rickettsial bacterium, not Bartonella. - It is transmitted by **chiggers** and characterized by a rash, fever, and eschar at the bite site. *Epidemic typhus* - Epidemic typhus is caused by **Rickettsia prowazekii** and is also louse-borne. - It presents with sudden high fever, severe headache, and a maculopapular rash that spares the face, palms, and soles. *Endemic typhus* - Endemic typhus (murine typhus) is caused by **Rickettsia typhi** and is transmitted by **rat fleas**. - Its symptoms are generally milder than epidemic typhus, including fever, headache, and a truncal rash.
Question 596: Which immunoglobulin does Protein A of Staphylococcus aureus bind to?
- A. IgA
- B. IgG (Correct Answer)
- C. IgD
- D. IgE
Explanation: ***IgG*** - **Protein A** of *Staphylococcus aureus* binds to the **Fc region** of IgG antibodies. - This binding mechanism helps *S. aureus* in **evading opsonization** and phagocytosis by interfering with the host immune response. *IgA* - IgA is primarily found in **mucosal secretions** and its primary role is in mucosal immunity. - Protein A does not preferentially bind to IgA; instead, some bacteria produce specific **IgA proteases** to cleave and inactivate IgA. *IgD* - IgD is found mostly on the surface of **B lymphocytes** and its main role is in B cell activation. - Protein A does not have a significant binding affinity for IgD. *IgE* - IgE is involved in **allergic reactions** and defense against parasites. - Protein A does not bind to IgE; binding to IgE is typically mediated by specific IgE receptors on mast cells and basophils.
Question 597: Which type of DNase produced by Streptococcus is known to be the most antigenic in humans?
- A. DNase C
- B. DNase D
- C. DNase A
- D. DNase B (Correct Answer)
Explanation: ***DNase B*** - **DNase B** is the most **antigenic** of the four DNases (A, B, C, D) produced by *Streptococcus pyogenes*. - Antibodies against DNase B are commonly measured as anti-DNase B titers in the diagnosis of **streptococcal infections** and their sequelae, like **acute rheumatic fever** and **post-streptococcal glomerulonephritis**, especially when ASO titers are negative. *DNase A* - While *Streptococcus pyogenes* produces **DNase A**, it is not considered the most antigenically potent or clinically relevant for antibody testing in humans. - Its antigenicity is generally **lower** than that of DNase B in response to streptococcal infection. *DNase C* - **DNase C** is another deoxyribonuclease produced by *Streptococcus pyogenes*. - Similar to DNase A, it does not elicit as strong or as consistent an **antibody response** in human infections compared to DNase B. *DNase D* - **DNase D** is the fourth type of deoxyribonuclease produced by *Streptococcus pyogenes*. - Its **antigenicity** in humans is less pronounced and less diagnostically significant than that of **DNase B**.