UPSC-CMS 2012 — Microbiology

Q: All of the following organisms are involved in post-splenectomy sepsis except

Staphylococcus aureus. ***Staphylococcus aureus*** - While *Staphylococcus aureus* can cause various infections, it is **not typically considered a primary encapsulated organism** for which the spleen's filtering function is critical, and therefore, it is **less commonly implicated in overwhelming post-splenectomy infection (OPSI)** compared to encapsulated bacteria. - The risk of OPSI is significantly higher with **encapsulated bacteria** due to the spleen's role in clearing these pathogens. *Neisseria meningitidis* - *Neisseria meningitidis* is an **encapsulated bacterium** and a well-known cause of **meningitis and sepsis**, particularly in individuals with **asplenia**. - The **spleen plays a crucial role in filtering encapsulated organisms** from the bloodstream, making asplenic individuals highly susceptible. *Haemophilus influenzae* - **Encapsulated strains** of *Haemophilus influenzae* (especially type b) are a significant cause of invasive infections in asplenic patients, including **meningitis and epiglottitis**. - The **lack of splenic immune function** impairs the body's ability to clear these bacteria. *Streptococcus pneumoniae* - *Streptococcus pneumoniae* is the **most common cause of OPSI** (overwhelming post-splenectomy infection) due to its **polysaccharide capsule**. - The spleen is essential for **opsonization and phagocytosis** of encapsulated bacteria, a function lost post-splenectomy. [Practice more Microbiology PYQs on OnCourse]

Q: The pathogenic organism responsible for the causation of Donovaniasis is

Klebsiella granulomatis. ***Klebsiella granulomatis*** - This bacterium is the causative agent of **granuloma inguinale**, also known as **donovaniasis**. - It infects macrophages and causes chronic, progressive **genital ulcers** with a characteristic beefy-red appearance. *Herpes simplex virus* - This virus causes **genital herpes**, characterized by painful **vesicular or ulcerative lesions** that tend to recur. *Haemophilus ducreyi* - This bacterium causes **chancroid**, characterized by painful, soft chancres with **ragged, undermined borders**. *Chlamydia trachomatis* - This bacterium is responsible for several sexually transmitted infections, including **lymphogranuloma venereum (LGV)**, which presents with transient genital lesions followed by painful, suppurative lymphadenopathy, and **genital chlamydial infections** which often cause urethritis or cervicitis. [Practice more Microbiology PYQs on OnCourse]

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All of the following organisms are involved in post-splenectomy sepsis except

The pathogenic organism responsible for the causation of Donovaniasis is