Emerging Bacterial Infections — MCQs
Which disease is most closely associated with intensive international surveillance for global eradication?
Which of the following causes Melioidosis?
A young man, home on leave from the military, went camping in the woods to detect deer movement for future hunting. Ten days later, he developed fever, malaise, and myalgia. Leukopenia and thrombocytopenia were observed, as well as several tick bites. Which of the following statements best describes human monocytic ehrlichiosis (HME)?
A diabetic patient developed cellulitis due to S. aureus, which was found to be methicillin resistant on the antibiotic sensitivity testing. All of the following antibiotics will be appropriate except ?
Lyme disease is caused by:
Insane paresis is associated with -
All the following statements are true regarding beta-lactams except:
Botryomycosis is a ___ disease
An adult man presents with the clinical condition shown in the image, and a Gram stain reveals Gram-negative diplococci. What is the most appropriate treatment?
All of the following statements are true regarding neutrophil extracellular trapping (NET) except for which of the following?
Emerging Bacterial Infections Indian Medical PG Practice Questions and MCQs
Question 1: Which disease is most closely associated with intensive international surveillance for global eradication?
- A. Polio (Correct Answer)
- B. Hepatitis
- C. TB
- D. Leprosy
Explanation: **Polio** - **Polio** has been the focus of an intensive global eradication campaign, requiring robust **international surveillance** to track cases, mutations, and vaccine-derived polioviruses. - The **Global Polio Eradication Initiative (GPEI)**, a major international collaboration, relies heavily on coordinated surveillance efforts to ensure no wild poliovirus remains undetected. *Hepatitis* - While **hepatitis** is a significant global health burden, particularly hepatitis B and C, it is not subject to the same level of internationally coordinated, aggressive surveillance aimed at **global eradication** as polio. - Surveillance for hepatitis often focuses on prevalence, incidence, and risk factors at national and regional levels rather than a centralized, real-time eradication tracking system. *TB* - **Tuberculosis (TB)** is a major global health concern, and there are international efforts for control and elimination, but it is not currently targeted for **global eradication** in the same manner as polio. - Surveillance for TB often involves tracking drug-resistant strains and treatment outcomes, but it doesn't involve the immediate, outbreak-focused international alert system seen with diseases like polio or novel pandemics. *Leprosy* - **Leprosy** is a neglected tropical disease, and while there are international efforts for its control and elimination, primarily led by the WHO, it does not involve the same level of intensive, real-time global surveillance for eradication as **polio**. - Surveillance for leprosy is typically focused on case detection, treatment completion, and identifying areas with high endemicity rather than rapid international notification of individual cases for eradication purposes.
Question 2: Which of the following causes Melioidosis?
- A. Burkholderia pseudomallei (Correct Answer)
- B. Burkholderia cepacia
- C. Burkholderia mallei
- D. None of the options
Explanation: ***Burkholderia pseudomallei*** - **Melioidosis** is caused by the bacterium **_Burkholderia pseudomallei_**, a **Gram-negative rod** found in soil and water. - This organism is endemic in tropical and subtropical regions, particularly Southeast Asia and northern Australia, and can cause a wide spectrum of disease from asymptomatic infection to fulminant sepsis. *Burkholderia cepacia* - **_Burkholderia cepacia complex_** is a group of bacteria known to cause infections, particularly in individuals with **cystic fibrosis** or **immunocompromised states**. - While it can cause opportunistic infections, it is not the causative agent of melioidosis. *Burkholderia mallei* - **_Burkholderia mallei_** is the causative agent of **glanders**, a contagious disease primarily affecting **horses, donkeys, and mules**, which can be transmitted to humans. - It is related to **_B. pseudomallei_** but does not cause melioidosis. *None of the options* - This option is incorrect because **_Burkholderia pseudomallei_** is the specific and well-established causative agent of melioidosis.
Question 3: A young man, home on leave from the military, went camping in the woods to detect deer movement for future hunting. Ten days later, he developed fever, malaise, and myalgia. Leukopenia and thrombocytopenia were observed, as well as several tick bites. Which of the following statements best describes human monocytic ehrlichiosis (HME)?
- A. It is a fatal disease transmitted by the bite of a dog
- B. Clinical diagnosis is based on the presence of erythema migrans (EM)
- C. Diagnosis is usually made serologically but morulae may be seen in the cytoplasm of monocytes (Correct Answer)
- D. Symptoms include vomiting and paralysis
Explanation: Diagnosis is usually made serologically but morulae may be seen in the cytoplasm of monocytes - **Human monocytic ehrlichiosis (HME)** is caused by *Ehrlichia chaffeensis*, an obligate intracellular bacterium that infects monocytes. [1] - The gold standard for diagnosis is often **serology** (e.g., indirect immunofluorescence assay), but microscopic examination of peripheral blood smears may reveal characteristic **morulae** (microcolony of bacteria) within the cytoplasm of monocytes, especially in the early stages of infection. *It is a fatal disease transmitted by the bite of a dog* - HME is typically transmitted by the **lone star tick** (*Amblyomma americanum*), not by dog bites. While severe cases can be fatal, it is not universally fatal and is generally treatable with antibiotics. - The primary vector is the lone star tick, with reservoir hosts including white-tailed deer. [1] *Clinical diagnosis is based on the presence of erythema migrans (EM)* - **Erythema migrans (EM)** is the characteristic rash associated with **Lyme disease**, caused by *Borrelia burgdorferi*, and is not seen in HME. [1] - HME symptoms include fever, headache, malaise, and muscle aches, often accompanied by **leukopenia** and **thrombocytopenia**, but no distinctive rash like EM. *Symptoms include vomiting and paralysis* - While vomiting can occur with HME, **paralysis** is not a typical symptom of this disease. - Symptoms more commonly include **fever, headache, malaise, muscle aches, leukopenia, and thrombocytopenia**.
Question 4: A diabetic patient developed cellulitis due to S. aureus, which was found to be methicillin resistant on the antibiotic sensitivity testing. All of the following antibiotics will be appropriate except ?
- A. Vancomycin
- B. Teicoplanin
- C. Linezolid
- D. Imipenem (Correct Answer)
Explanation: ***Imipenem*** - **Imipenem** is a carbapenem antibiotic that is effective against many Gram-positive and Gram-negative bacteria, but it is **not active against MRSA (methicillin-resistant *Staphylococcus aureus*)**. - MRSA strains are resistant to all beta-lactam antibiotics, including penicillins, cephalosporins, and carbapenems like imipenem, due to the presence of the **mecA gene** which encodes for an altered penicillin-binding protein (PBP2a). *Vancomycin* - **Vancomycin** is a glycopeptide antibiotic that is a primary choice for treating **MRSA infections**, including cellulitis. - It inhibits cell wall synthesis by binding to the D-Ala-D-Ala precursor, preventing cross-linking, and is specifically active against **Gram-positive bacteria**. *Teicoplanin* - **Teicoplanin** is another glycopeptide antibiotic, similar to vancomycin, and is also considered a suitable agent for treating **MRSA infections**. - It works by inhibiting bacterial cell wall synthesis and has a **longer half-life** than vancomycin, allowing for less frequent dosing. *Linezolid* - **Linezolid** is an oxazolidinone antibiotic known for its activity against **Gram-positive bacteria**, including **MRSA** and vancomycin-resistant enterococci (VRE). - It inhibits protein synthesis by binding to the 50S ribosomal subunit, preventing the formation of the initiation complex.
Question 5: Lyme disease is caused by:
- A. T. pertenue
- B. B. vincenti
- C. B. recurrentis
- D. B. burgdorferi (Correct Answer)
Explanation: ***Correct: B. burgdorferi*** - **Lyme disease** is a **tick-borne illness** caused by the spirochete *Borrelia burgdorferi*. - This bacterium is transmitted to humans through the bite of infected ticks, primarily the **black-legged tick** (*Ixodes scapularis*). *Incorrect: B. vincenti* - *Borrelia vincenti* is associated with **Vincent's angina** (fusospirochetal disease), a severe gingivitis, and periodontitis. - It is not implicated in Lyme disease but rather in an oro-dental infection. *Incorrect: B. recurrentis* - *Borrelia recurrentis* is the causative agent of **epidemic relapsing fever**. - This disease is transmitted by the **human body louse** and is characterized by recurring episodes of fever. *Incorrect: T. pertenue* - *Treponema pertenue* is the bacterium responsible for **yaws**, a chronic, disfiguring skin infection. - It is a related spirochete to *Treponema pallidum* (syphilis) but causes a non-venereal disease primarily in tropical regions.
Question 6: Insane paresis is associated with -
- A. Leishmaniasis
- B. Yellow fever
- C. Syphilis (Correct Answer)
- D. Neisseria meningitidis
Explanation: ***Syphilis*** - **General paresis**, or "insane paresis," is a neuropsychiatric manifestation of **tertiary syphilis**, resulting from chronic meningoencephalitis. - It presents with progressive **dementia**, personality changes, delusions, and neurological deficits. *Leishmaniasis* - This parasitic disease is characterized by various forms including **cutaneous**, **mucocutaneous**, and **visceral leishmaniasis** (kala-azar). - It typically causes skin lesions, mucocutaneous destruction, or systemic symptoms like fever, hepatosplenomegaly, and pancytopenia, but not general paresis. *Yellow fever* - **Yellow fever** is a viral hemorrhagic disease transmitted by mosquitoes, primarily affecting the liver and kidneys. - Symptoms include fever, jaundice, hemorrhage, and shock, but not the neurological degeneration seen in general paresis. *Neisseria meningitidis* - This bacterium causes **meningococcal meningitis** and **meningococcemia**, which are acute and severe infectious diseases. - While it can lead to acute neurological symptoms due to meningitis, it does not cause the chronic, progressive neuropsychiatric syndrome known as general paresis.
Question 7: All the following statements are true regarding beta-lactams except:
- A. Methicillin is not orally bioavailable and is given parenterally.
- B. Imipenem should be given with cilastatin
- C. Meropenem does not require cilastatin for protection against renal toxicity.
- D. Aztreonam shows cross-reactivity with cephalexin. (Correct Answer)
Explanation: ***Aztreonam shows cross-reactivity with cephalexin.*** - **Aztreonam** is a monobactam with a distinct chemical structure from other beta-lactams, resulting in a different **allergy profile** and lack of significant **cross-reactivity** with other beta-lactams, including cephalosporins like cephalexin. - Its unique structure also means it is specifically active against **gram-negative bacteria** and generally resistant to common beta-lactamases that deactivate other beta-lactams. *Imipenem should be given with cilastatin* - **Imipenem** is rapidly metabolized in the renal tubules by **dehydropeptidase-1**, leading to reduced antibiotic concentrations and potential for nephrotoxicity. - **Cilastatin** is a dehydropeptidase inhibitor that prevents the breakdown of imipenem, ensuring adequate drug levels and reducing renal damage. *Methicillin is not orally bioavailable and is given parenterally.* - **Methicillin** is an acid-labile penicillin, meaning it is extensively degraded by stomach acid when taken orally, leading to poor absorption. - Due to its instability in acidic environments, methicillin must be administered **parenterally (intravenously or intramuscularly)** to achieve therapeutic concentrations. *Meropenem does not require cilastatin for protection against renal toxicity.* - **Meropenem** is another carbapenem, but it is much more stable to metabolism by **renal dehydropeptidase-1** compared to imipenem. - This inherent stability eliminates the need for co-administration with **cilastatin** to prevent its degradation and protect against nephrotoxicity.
Question 8: Botryomycosis is a ___ disease
- A. Viral
- B. Bacterial (Correct Answer)
- C. Parasitic
- D. Fungal
Explanation: ***Bacterial*** - **Botryomycosis** is primarily a **bacterial infection**, commonly caused by *Staphylococcus aureus* or, less frequently, by gram-negative bacteria like *Pseudomonas aeruginosa*. - It presents as chronic suppurative granulomatous inflammation characterized by the presence of **"grains" or "granules"** composed of bacterial microcolonies surrounded by hyaline material. *Viral* - **Viral infections** are caused by viruses and are typically characterized by intracellular replication and various cytopathic effects. - Botryomycosis does not involve viral pathogens; its pathogenesis is entirely distinct from viral diseases. *Parasitic* - **Parasitic diseases** are caused by parasites such as protozoa, helminths, or ectoparasites. - The clinical and pathological features of botryomycosis, including the distinct bacterial grains, do not align with parasitic infections. *Fungal* - Although it can superficially resemble **mycetoma (a fungal infection)** due to the presence of "grains," botryomycosis is not caused by fungi. - Mycetoma involves fungal organisms like *Madurella mycetomatis* or *Actinomadura madura*, which are distinctly different from the bacterial agents of botryomycosis.
Question 9: An adult man presents with the clinical condition shown in the image, and a Gram stain reveals Gram-negative diplococci. What is the most appropriate treatment?
- A. Ceftriaxone (Correct Answer)
- B. Azithromycin
- C. Doxycycline
- D. Acyclovir
Explanation: ***Ceftriaxone*** - The image shows **urethritis** (discharge from the urethra), and the Gram stain revealing **Gram-negative diplococci** is characteristic of **Neisseria gonorrhoeae**. - **Ceftriaxone** is the recommended first-line treatment for **gonorrhea**, often administered as a single intramuscular dose. *Azithromycin* - While often co-administered with ceftriaxone to cover potential **Chlamydia coinfection**, it is not the primary treatment for gonorrhea alone. - Azithromycin is the main treatment for uncomplicated **Chlamydia trachomatis** infections. *Doxycycline* - **Doxycycline** is a highly effective antibiotic for treating **Chlamydia trachomatis** infections and certain other bacterial STIs. - It is not the primary treatment for **gonorrhea** due to resistance concerns and preferred efficacy of cephalosporins. *Acyclovir* - **Acyclovir** is an antiviral medication used to treat infections caused by the **herpes simplex virus (HSV)**. - It has no activity against **bacterial infections** like gonorrhea, making it inappropriate for this presentation.
Question 10: All of the following statements are true regarding neutrophil extracellular trapping (NET) except for which of the following?
- A. It is detected in blood during sepsis
- B. It is chromatin with antibacterial enzymes
- C. Mitochondrial DNA is seen (Correct Answer)
- D. It is produced in response to bacterial infection
Explanation: ***Mitochondrial DNA is seen*** - NETs (Neutrophil Extracellular Traps) are made primarily of **nuclear chromatin**, not mitochondrial DNA [2]. - The main purpose of NETs is to trap and kill pathogens, focusing on **nuclear genetic material** rather than mitochondrial components. *It is detected in blood during sepsis* - NETs can indeed be found in the **circulation during sepsis**, serving as a defense mechanism against infections. - Their presence in blood indicates an **active immune response**, particularly in severe systemic infections. *It is produced in response to bacterial infection* - NET formation is a known response to **bacterial infections**, as neutrophils deploy them to capture and neutralize pathogens. - This process helps in controlling infections, showcasing the importance of NETs in **innate immunity**. *It is chromatin with antibacterial enzymes* - NETs consist primarily of **decondensed chromatin**, embedded with **antimicrobial proteins** and enzymes to combat pathogens [1][2]. - This characteristic underscores their role in targeting and eliminating invading microorganisms effectively. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 91-92. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 92-93.
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