Neisseria and Moraxella — MCQs
A patient presents with urethral discharge. Gram stain shows intracellular gram-negative diplococci. What is the causative organism?
A sex worker presents with purulent urethral discharge and gram-negative diplococci in culture. What is the most likely diagnosis?
Increased susceptibility to N. meningitidis infections is associated with deficiency of which complement component:
A sex worker presents with purulent urethral discharge and gram-negative diplococci. Diagnosis?
What is the most common genetic factor associated with increased susceptibility to Neisseria infections?
Meningitis with rash is seen in -
A 9-year-old child presented to OPD with complaints of high-grade fever, vomiting, and one episode of seizure. CSF examination was done and Gram staining of the culture showed lanceolate-shaped gram-positive diplococci. What is the probable causative agent?
An adult patient with a military background is admitted with a rash, fever, altered sensorium, and a deficiency of the membrane attack complex. What is the most likely etiological agent?
A lady came with yellowish discharge and stain showing gram-negative diplococci. What is the most likely causative organism of her condition?
A male patient presents with white discharge from the urethra, as shown in the image. What is the most probable causative organism?
Neisseria and Moraxella Indian Medical PG Practice Questions and MCQs
Question 1: A patient presents with urethral discharge. Gram stain shows intracellular gram-negative diplococci. What is the causative organism?
- A. Mycoplasma genitalium
- B. Treponema pallidum
- C. Chlamydia trachomatis
- D. Neisseria gonorrhoeae (Correct Answer)
Explanation: ***Neisseria gonorrhoeae*** - The presence of **intracellular gram-negative diplococci** in urethral discharge is a classic microscopic finding for *Neisseria gonorrhoeae*. - This organism directly invades host cells, and its unique gram staining characteristic makes it readily identifiable in clinical samples. *Mycoplasma genitalium* - This organism does not have a **cell wall** and therefore will not gram stain. It cannot be identified by Gram stain. - Diagnosis typically requires molecular methods like **PCR**. *Treponema pallidum* - This spirochete is too thin to be visualized with standard Gram stain and is typically identified using **dark-field microscopy** or serological tests. - It does not present as gram-negative diplococci. *Chlamydia trachomatis* - *Chlamydia trachomatis* is an **obligate intracellular bacterium** but does not stain well with Gram stain due to its unique cell wall structure (lacks peptidoglycan). - It is often diagnosed using **nucleic acid amplification tests (NAATs)**.
Question 2: A sex worker presents with purulent urethral discharge and gram-negative diplococci in culture. What is the most likely diagnosis?
- A. Treponema pallidum
- B. Haemophilus ducreyi
- C. Chlamydia trachomatis
- D. Neisseria gonorrhoeae (Correct Answer)
Explanation: ***Neisseria gonorrhoeae*** - **Purulent urethral discharge** and identification of **Gram-negative diplococci** on microscopy are classic diagnostic features of gonococcal urethritis [1]. - This sexually transmitted infection is common among sexually active individuals, including **sex workers** [1]. *Treponema pallidum* - This bacterium causes **syphilis**, which is characterized by **chancres** in the primary stage, and widespread rashes or lesions in later stages [2]. - It would not typically present with Gram-negative diplococci or purulent urethral discharge [2]. *Haemophilus ducreyi* - This organism is responsible for **chancroid**, a sexually transmitted infection that causes painful **genital ulcers** with ragged borders and often associated with lymphadenopathy [3]. - It would not lead to purulent urethral discharge, and while Gram-negative, it is typically seen as pleomorphic rods in chains. *Chlamydia trachomatis* - **Chlamydia** infection often presents with mucopurulent urethral discharge, but it is typically less purulent than gonorrhea and may be **asymptomatic** [1]. - **Chlamydia** is an **obligate intracellular bacterium** and would not be visualized as Gram-negative diplococci on a Gram stain [1].
Question 3: Increased susceptibility to N. meningitidis infections is associated with deficiency of which complement component:
- A. C1-C4 deficiency
- B. C3 deficiency
- C. C5-C9 deficiency (Correct Answer)
- D. C2 deficiency
Explanation: ***C5-C9 deficiency*** - Deficiencies in **C5-C9 components** impair the formation of the **Membrane Attack Complex (MAC)**, which is crucial for lysing Gram-negative bacteria like **N. meningitidis**. - Patients with MAC deficiencies are at significantly higher risk for recurrent invasive **N. meningitidis** infections. *C1-C4 deficiency* - Deficiencies in **C1-C4 components** primarily affect the **classical complement pathway** and are associated with increased susceptibility to **bacterial infections** and **immune complex diseases** (e.g., SLE). - While these deficiencies compromise opsonization and inflammation, they are not specifically linked to recurrent **N. meningitidis** infections. *C3 deficiency* - **C3 deficiency** is a severe primary immunodeficiency leading to profound defects in complement activation via all pathways, affecting **opsonization** and the formation of the MAC. - This deficiency causes severe recurrent **pyogenic infections** due to encapsulated bacteria but is not as specifically or commonly linked to **N. meningitidis** as deficiencies in the terminal pathway. *C2 deficiency* - **C2 deficiency** is the most common complement deficiency and primarily impacts the **classical pathway**, leading to impaired opsonization and immune complex clearance. - It is often associated with recurrent infections (especially with encapsulated bacteria) and **lupus-like syndromes**, but not specifically increased susceptibility to **N. meningitidis** infections.
Question 4: A sex worker presents with purulent urethral discharge and gram-negative diplococci. Diagnosis?
- A. N. gonorrhoeae (Correct Answer)
- B. T. pallidum
- C. C. trachomatis
- D. H. ducreyi
Explanation: ***N. gonorrhoeae*** - The presence of **purulent urethral discharge** and **Gram-negative diplococci** on microscopy is highly characteristic of **gonorrhea**. - **Neisseria gonorrhoeae** is a common cause of sexually transmitted infections, particularly in individuals with a higher risk profile like sex workers. *T. pallidum* - **Treponema pallidum** causes syphilis, which typically presents with a **chancre** (primary stage) or a rash (secondary stage), not purulent urethral discharge. - It is a **spirochete** and cannot be visualized as Gram-negative diplococci. *C. trachomatis* - **Chlamydia trachomatis** causes **nongonococcal urethritis**, which often presents with a less purulent or mucoid discharge, and may be asymptomatic. - It is an **obligate intracellular bacterium** and does not appear as Gram-negative diplococci on Gram stain. *H. ducreyi* - **Haemophilus ducreyi** causes **chancroid**, characterized by painful genital ulcers with regional lymphadenopathy. - It would not typically present with purulent urethral discharge and is a **Gram-negative rod**, not diplococci.
Question 5: What is the most common genetic factor associated with increased susceptibility to Neisseria infections?
- A. HLA-B27
- B. Complement deficiency (Correct Answer)
- C. IgA deficiency
- D. Factor H deficiency
Explanation: ***Complement deficiency*** - Deficiencies in the **terminal complement pathway (C5-C9)**, particularly C5b-C9 (membrane attack complex, MAC), significantly increase susceptibility to disseminated *Neisseria* infections. - The MAC is crucial for lysing Gram-negative bacteria like *Neisseria meningitidis* and *Neisseria gonorrhoeae*, and its absence allows for uncontrolled bacterial proliferation. *Factor H deficiency* - **Factor H** is a regulatory protein of the alternative complement pathway, preventing its overactivation on host cells. - Its deficiency typically leads to conditions like **atypical hemolytic uremic syndrome (aHUS)** and **dense deposit disease**, not primarily increased susceptibility to *Neisseria* infections. *HLA B27* - **HLA-B27** is a human leukocyte antigen strongly associated with a group of autoimmune inflammatory diseases called **spondyloarthropathies**, such as ankylosing spondylitis. - It does not directly impact the immune response to *Neisseria* infections or increase susceptibility to them. *IgA deficiency* - **Selective IgA deficiency** is the most common primary immunodeficiency, characterized by low or absent IgA levels. - Individuals with IgA deficiency are more prone to **recurrent respiratory and gastrointestinal infections**, but not specifically disseminated *Neisseria* infections.
Question 6: Meningitis with rash is seen in -
- A. Neisseria meningitidis (Correct Answer)
- B. H. influenzae
- C. Strepto. agalactae
- D. Pneumococcus
Explanation: **Neisseria meningitidis** - **Meningococcal meningitis** is classically associated with an acute onset of fever, headache, stiff neck, and a characteristic **petechial or purpuric rash** [1]. - The rash is due to widespread **vasculitis** and disseminated intravascular coagulation (DIC) caused by the bacteria. *H. influenzae* - While *H. influenzae* type b (Hib) was a major cause of bacterial meningitis before vaccination, it typically does not cause a *rash*. - Meningitis caused by *H. influenzae* presents with fever, headache, stiff neck, and altered mental status without dermatological manifestations. *Strepto. agalactiae* - *Streptococcus agalactiae* (Group B Strep) is a common cause of meningitis in **neonates** and infants. - It usually presents with non-specific symptoms like fever, lethargy, and poor feeding, and a rash is not a typical feature of GBS meningitis. *Pneumococcus* - *Streptococcus pneumoniae* (Pneumococcus) is another leading cause of bacterial meningitis in adults and children [1]. - Symptoms include fever, headache, stiff neck, and altered mental status, but a cutaneous rash is not characteristic of pneumococcal meningitis [1].
Question 7: A 9-year-old child presented to OPD with complaints of high-grade fever, vomiting, and one episode of seizure. CSF examination was done and Gram staining of the culture showed lanceolate-shaped gram-positive diplococci. What is the probable causative agent?
- A. Haemophilus influenzae
- B. Streptococcus agalactiae
- C. Neisseria meningitidis
- D. Streptococcus pneumoniae (Correct Answer)
Explanation: ***Streptococcus pneumoniae*** - The description of **lanceolate-shaped gram-positive diplococci** in CSF is characteristic of *S. pneumoniae*. - This bacterium is a common cause of **bacterial meningitis** in children and can present with high fever, vomiting, and seizures. *Haemophilus influenzae* - This is a **gram-negative coccobacillus**, which would appear as small, pleomorphic rods rather than lanceolate-shaped diplococci on Gram stain. - While it causes meningitis, its Gram stain morphology is distinct from *S. pneumoniae*. *Streptococcus agalactiae* - *S. agalactiae* (Group B Streptococcus) is a **gram-positive coccus**, but it typically appears in **chains** and is a major cause of neonatal meningitis, not usually in a 9-year-old child. - Its morphology on Gram stain would not be described as lanceolate diplococci. *Neisseria meningitidis* - *N. meningitidis* is a **gram-negative diplococcus** and would appear as kidney-bean shaped or flattened paired cocci, not gram-positive. - Though a common cause of meningitis, the Gram stain morphology described rules it out.
Question 8: An adult patient with a military background is admitted with a rash, fever, altered sensorium, and a deficiency of the membrane attack complex. What is the most likely etiological agent?
- A. Klebsiella pneumoniae
- B. Neisseria meningitidis (Correct Answer)
- C. Haemophilus influenzae
- D. CMV
Explanation: ***Neisseria meningitidis*** - A deficiency in the **membrane attack complex (MAC)**, particularly **C5-C9 components**, predisposes individuals to recurrent infections with encapsulated bacteria, especially *N. meningitidis*. - *N. meningitidis* is a common cause of **meningitis**, presenting with **fever, altered sensorium**, and often a **petechial rash** due to disseminated intravascular coagulation (DIC), which align with the patient's symptoms. *Klebsiella pneumoniae* - While *K. pneumoniae* can cause severe infections, including pneumonia and meningitis, it is not specifically associated with **MAC deficiency**. - Its infections more commonly manifest as **severe pneumonia** or **urinary tract infections** in immunocompromised patients. *Haemophilus influenzae* - *H. influenzae* can cause meningitis and other invasive infections, especially in children, but it is not typically linked to **MAC deficiency**. - The classic presentation involving **rash** and severe systemic symptoms as described is more characteristic of **meningococcal disease**. *CMV* - **Cytomegalovirus (CMV)** is a herpesvirus that causes a wide range of diseases, particularly in immunocompromised individuals. - However, CMV infections are primarily associated with **cellular immunity defects** rather than a deficiency in the **membrane attack complex** of the complement system.
Question 9: A lady came with yellowish discharge and stain showing gram-negative diplococci. What is the most likely causative organism of her condition?
- A. Streptococcus pneumoniae
- B. Enterococcus faecalis
- C. Neisseria gonorrhoeae (Correct Answer)
- D. Both Streptococcus and Enterococcus
Explanation: ***Neisseria gonorrhoeae*** - The presence of **yellowish discharge** and **gram-negative diplococci** on a stain is a classic presentation for **gonorrhea**, caused by *Neisseria gonorrhoeae*. - This bacterium is a common cause of **sexually transmitted infections (STIs)**, leading to conditions like cervicitis, urethritis, and pelvic inflammatory disease. *Streptococcus pneumoniae* - This organism is a **gram-positive coccus** and typically causes **respiratory infections** (e.g., pneumonia, otitis media, meningitis), not genital discharge with gram-negative diplococci. - It is not associated with STI-related yellowish genital discharge. *Enterococcus faecalis* - This is a **gram-positive coccus** and a common cause of **urinary tract infections (UTIs)** and **nosocomial infections**, but not typically associated with yellowish genital discharge showing gram-negative diplococci. - It is also not classified as a gram-negative organism. *Both Streptococcus and Enterococcus* - This option is incorrect because both *Streptococcus* and *Enterococcus* are **gram-positive organisms**. - The clinical presentation clearly describes **gram-negative diplococci**, which rules out these bacteria as the primary cause.
Question 10: A male patient presents with white discharge from the urethra, as shown in the image. What is the most probable causative organism?
- A. Haemophilus ducreyi
- B. Klebsiella granulomatis
- C. Neisseria gonorrhoeae (Correct Answer)
- D. Treponema pallidum
Explanation: ***Neisseria gonorrhoeae*** - Among the given options, *Neisseria gonorrhoeae* is the **most probable causative organism** for **urethral discharge** in males. - Gonorrhea is a common sexually transmitted infection (STI) presenting with **purulent urethritis**, typically with thick, yellow-green discharge, though appearance can vary. - **Clinical note:** While classic gonococcal discharge is purulent and yellow-green, the clinical presentation can vary. None of the other organisms listed cause urethritis with discharge. *Haemophilus ducreyi* - This bacterium causes **chancroid**, a sexually transmitted infection characterized by **painful genital ulcers (chancres)** and **inguinal lymphadenopathy**, not urethral discharge. - Presents with ulcerative lesions, not discharge. *Klebsiella granulomatis* - This organism is responsible for **donovanosis** (granuloma inguinale), which manifests as **painless, progressive ulcerative lesions** on the genitals. - It does not cause urethral discharge; presents with beefy red granulomatous lesions. *Treponema pallidum* - This spirochete causes **syphilis**, which presents with **painless chancres** in the primary stage, **maculopapular rash** in the secondary stage, and gummas or neurological symptoms in later stages. - Urethral discharge is not a typical symptom of syphilis; primary lesions are ulcerative.
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