Sexually Transmitted Enteric Infections — MCQs
A man with pain during defecation, no gastrointestinal symptoms, and ulcers extending into the anal canal. Diagnosis?
A patient presents with urethral discharge. Gram stain shows intracellular gram-negative diplococci. What is the causative organism?
A 46-year-old woman with HIV presents with severe persistent diarrhea. Histological investigation reveals the presence of oocysts. Identify the organism causing diarrhea in this HIV patient.
Which of the following is NOT a cause of secretory diarrhea?
A man presents with a history of dysuria and urethral discharge after having unprotected sexual intercourse. What is the treatment of choice for this infection?
Episodes of repeated thin stools with mucus, subjective feeling of fever and lower abdominal pain, with leukocytes in stool. Which of the following is likely?
A patient living with HIV presents with foulsmelling stools. Microscopic examination of the stool reveals no cysts or ova, but a 200-micrometer larva is observed. What is the most likely pathogen?
All of the following are sexually transmitted, except.
Treatment of partner is required in all infection except:
Which one of the following statements best characterizes lympho-granuloma venereum (LGV)?
Sexually Transmitted Enteric Infections Indian Medical PG Practice Questions and MCQs
Question 1: A man with pain during defecation, no gastrointestinal symptoms, and ulcers extending into the anal canal. Diagnosis?
- A. Cytomegalovirus (CMV)
- B. Gonococcal infection
- C. Genital herpes (Correct Answer)
- D. HIV infection
Explanation: Herpes simplex virus (HSV) infection of the anal canal is characterized by lesions that present as painful ulcers [1]. Direct extension into the anal canal is common in individuals with receptive anal intercourse or autoinoculation, often causing symptoms such as anal or rectal pain [1]. CMV proctitis typically causes more diffuse inflammation, often with bloody stools, diarrhea, and abdominal pain, which are not described in this case. While CMV can cause ulcers, they are usually shallow and often associated with immunocompromised states. Gonococcal proctitis often presents with purulent anal discharge, rectal pain, itching, and tenesmus, but typically without deep ulcerations. HIV infection can cause various anorectal complications, including aphthous ulcers, but isolated anal ulcers and defecation pain would prompt investigation into sexually transmitted infections like herpes as a more direct cause.
Question 2: 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 3: A 46-year-old woman with HIV presents with severe persistent diarrhea. Histological investigation reveals the presence of oocysts. Identify the organism causing diarrhea in this HIV patient.
- A. Cryptosporidium (Correct Answer)
- B. Staphylococcus aureus
- C. Salmonella
- D. Clostridium botulinum
Explanation: ***Cryptosporidium*** - **Cryptosporidium** is a common cause of **severe, persistent diarrhea** in immunocompromised individuals, particularly those with **HIV/AIDS**. - Its presence is confirmed by identifying **oocysts in stool samples** through histological investigation or acid-fast staining. *Staphylococcus aureus* - **Staphylococcus aureus** typically causes **food poisoning** characterized by rapid onset of nausea, vomiting, and non-bloody diarrhea. - It is a bacterial infection and **does not produce oocysts**. *Salmonella* - **Salmonella** species are bacteria that cause **gastroenteritis**, typhoid fever, or bacteremia, often characterized by fever, abdominal cramps, and diarrhea. - Like other bacteria, they **do not form oocysts**; diagnosis is made by stool culture. *Clostridium botulinum* - **Clostridium botulinum** causes **botulism**, a neurologic illness resulting from toxin ingestion, leading to flaccid paralysis. - It is not associated with **diarrhea** and **does not produce oocysts**.
Question 4: Which of the following is NOT a cause of secretory diarrhea?
- A. Inflammatory bowel disease (IBD) (Correct Answer)
- B. Lactose intolerance
- C. Gastrinoma
- D. Celiac disease
Explanation: ***Inflammatory bowel disease (IBD)*** - IBD, which includes **Crohn's disease** and **ulcerative colitis**, primarily causes **inflammatory diarrhea**, characterized by damage to the intestinal lining and often with presence of blood or pus [1]. - While fluid secretion can occur, the predominant mechanism is altered absorption due to inflammation and mucosal damage, rather than active secretion. *Celiac disease* - Celiac disease causes **malabsorptive diarrhea** due to immune-mediated damage to the small intestine villi upon gluten ingestion [1]. - This leads to impaired absorption of nutrients and water, rather than active secretion [4]. *Lactose intolerance* - Lactose intolerance results in **osmotic diarrhea**, where undigested lactose in the gut draws water into the lumen [2]. - It does not involve active fluid secretion by the intestinal cells but rather an osmotic effect [3]. *Gastrinoma* - A gastrinoma is a neuroendocrine tumor that secretes excessive **gastrin**, leading to **Zollinger-Ellison syndrome**. - High gastrin levels cause increased gastric acid secretion, which overwhelms the intestine's neutralizing capacity, leading to inactivation of pancreatic enzymes and mucosal damage, all contributing to **secretory diarrhea**.
Question 5: A man presents with a history of dysuria and urethral discharge after having unprotected sexual intercourse. What is the treatment of choice for this infection?
- A. Erythromycin
- B. Azithromycin
- C. Ceftriaxone (Correct Answer)
- D. Penicillin G
Explanation: ***Ceftriaxone*** - The combination of **dysuria** and **urethral discharge** following unprotected sexual intercourse is highly suggestive of **gonorrhea**. - **Ceftriaxone** is the recommended first-line treatment for uncomplicated gonococcal infections due to increasing antibiotic resistance. *Erythromycin* - Erythromycin is primarily used for atypical bacterial infections, such as those caused by *Mycoplasma pneumoniae* or *Chlamydia trachomatis*. - While it can be used for chlamydia, it is not the preferred treatment for suspected gonorrhea. *Azithromycin* - Azithromycin is often used in combination with ceftriaxone for gonorrhea to cover potential co-infection with **Chlamydia trachomatis**. - However, **monotherapy with azithromycin is not recommended for gonorrhea** due to concerns about emerging resistance and suboptimal efficacy. *Penicillin G* - Penicillin G was historically used to treat gonorrhea, but this is no longer the case due to widespread **resistance** of *Neisseria gonorrhoeae* strains. - Its primary use now is for susceptible bacterial infections, such as syphilis and certain streptococcal infections.
Question 6: Episodes of repeated thin stools with mucus, subjective feeling of fever and lower abdominal pain, with leukocytes in stool. Which of the following is likely?
- A. Clostridium perfringens
- B. Staphylococcus aureus
- C. Giardia
- D. Entamoeba (Correct Answer)
Explanation: ***Entamoeba*** - The presence of **leukocytes in stool** along with symptoms like repeated thin stools with mucus, subjective fever, and lower abdominal pain are characteristic of **invasive amoebiasis** caused by *Entamoeba histolytica* [1]. - *Entamoeba histolytica* is known to cause **amoebic dysentery**, which involves inflammation and ulceration of the colon, leading to the presence of inflammatory cells in the stool [1]. *Clostridium perfringens* - This bacterium typically causes **food poisoning** with symptoms of abdominal cramps and watery diarrhea, which is usually **self-limiting** and does not typically involve significant inflammation or leukocytes in stool. - While it can cause necrotizing enteritis in severe cases, the more common presentation does not align with the description of mucosal stools and leukocytes. *Staphylococcus aureus* - *S. aureus* causes **food poisoning** through the ingestion of preformed toxins, leading to rapid onset of nausea, vomiting, and non-bloody diarrhea. - This condition is typically **short-lived** and does not usually involve leukocytes in the stool or significant inflammation, primarily affecting the upper gastrointestinal tract. *Giardia* - *Giardia lamblia* causes **giardiasis**, characterized by chronic diarrhea, malabsorption, bloating, and foul-smelling stools, but generally **does not cause invasive disease** or significant inflammation in the intestinal lining [2]. - Stool analysis in giardiasis typically shows **no leukocytes** or red blood cells, as the parasite does not invade the intestinal wall [2].
Question 7: A patient living with HIV presents with foulsmelling stools. Microscopic examination of the stool reveals no cysts or ova, but a 200-micrometer larva is observed. What is the most likely pathogen?
- A. Strongyloides stercoralis (Correct Answer)
- B. Ascaris lumbricoides
- C. Ancylostoma duodenale
- D. Schistosoma mansoni
Explanation: ***Strongyloides stercoralis*** - The presence of **larvae** in the stool [2], particularly **rhabditiform larvae**, is characteristic of *Strongyloides stercoralis* infection, as this parasite has an **autoinfective cycle** involving larval stages in the human host [2]. - In HIV-positive patients, *Strongyloides* can cause **hyperinfection syndrome**, leading to severe gastrointestinal symptoms like foul-smelling stools, and increased larval shedding [2]. *Ascaris lumbricoides* - *Ascaris lumbricoides* is a large intestinal nematode, but it typically presents with **ova** (eggs) in the stool, not larvae, as the eggs hatch in the small intestine. - While it can cause gastrointestinal symptoms, the hallmark microscopic finding in stool samples is the presence of **mammillated or decorticated eggs**. *Ancylostoma duodenale* - *Ancylostoma duodenale* (hookworm) infections are identified by the presence of **eggs** in the stool [1], which are typically oval with a thin shell and contain a developing larva. - Hookworm larvae usually develop in **soil** and infect humans through skin penetration, rather than being commonly found in stool samples from intestinal infection [1]. *Schistosoma mansoni* - *Schistosoma mansoni* is a **blood fluke** that causes intestinal schistosomiasis, characterized by the presence of **spined eggs** in the stool. - The parasite's life cycle involves **freshwater snails** as intermediate hosts, and a **larval stage (cercariae)** that penetrates human skin, but larvae are not typically found in human stool.
Question 8: All of the following are sexually transmitted, except.
- A. Echinococcus (Correct Answer)
- B. Molluscum contagiosum
- C. Group B streptococcus
- D. Candida albicans
Explanation: ***Echinococcus*** - **Echinococcus** (*Echinococcus granulosus* or *Echinococcus multilocularis*) causes **echinococcosis** (hydatid disease) which is transmitted through **ingestion of parasite eggs** found in contaminated food, water, or soil, often from dog feces. - The life cycle involves a **definitive host** (dogs) and an **intermediate host** (sheep, humans), with transmission occurring via the **fecal-oral route**, NOT through sexual contact. *Candida albicans* - While *Candida albicans* is part of normal human flora, **candidiasis** can be **sexually transmitted** through intimate contact. - Vaginal candidiasis and balanitis can be transmitted between sexual partners. *Molluscum contagiosum* - **Molluscum contagiosum** is a **viral skin infection** caused by a poxvirus that is commonly **sexually transmitted in adults** through direct skin-to-skin contact. - The lesions are small, raised, and dome-shaped with a central dimple. *Group B Streptococcus* - **Group B Streptococcus (GBS)** can colonize the **genital and gastrointestinal tracts** and can be transmitted through sexual contact. - While GBS is more clinically significant for vertical (perinatal) transmission from mother to newborn during delivery, colonization in adults can occur through sexual activity.
Question 9: Treatment of partner is required in all infection except:
- A. Trichomonas
- B. Herpes
- C. Gardnerella (Correct Answer)
- D. Candida
Explanation: ***Gardnerella*** - **Gardnerella vaginalis** is a common inhabitant of the vaginal flora and its overgrowth causes **bacterial vaginosis**, which is not typically considered a sexually transmitted infection (STI) in the same way others are. - While it can be transmitted sexually, treating the male partner has not been shown to prevent recurrence in the female; therefore, routine **partner treatment is generally not recommended**. *Trichomonas* - **Trichomoniasis** is a sexually transmitted infection caused by the parasite **Trichomonas vaginalis**. [1] - **Partner treatment is essential** to prevent reinfection and interrupt the cycle of transmission, as asymptomatic infection is common. [1] *Herpes* - **Genital herpes** is caused by the **Herpes Simplex Virus (HSV)** and is highly transmissible sexually. [2] - While treatment often focuses on managing symptoms in the infected individual, open communication and potential treatment or counseling for partners are crucial to prevent transmission and manage outbreaks. *Candida* - **Candidiasis** (yeast infection) is typically caused by an overgrowth of **Candida albicans**, a fungus naturally present in the body. - While it is not strictly an STI, sexual activity can sometimes trigger or exacerbate symptoms, and in recurrent cases, treating a male partner might be considered, but **it's not routinely required** as it is for true STIs like trichomonas or chlamydia. [2]
Question 10: Which one of the following statements best characterizes lympho-granuloma venereum (LGV)?
- A. It is most common in temperate regions
- B. The causative agent is C. trachomatis (Correct Answer)
- C. In the United States, it is more common among women
- D. Penicillin is effective in early treatment
Explanation: **The causative agent is *C. trachomatis*** - **Lymphogranuloma venereum (LGV)** is a sexually transmitted infection caused by specific serovars (**L1, L2, L2a, L2b, L3**) of *Chlamydia trachomatis*. [1] - These serovars are **invasive** and replicate in **mononuclear phagocytes** of lymphatic tissue, leading to the characteristic lymphadenopathy. [1] *It is most common in temperate regions* - LGV is **most common in tropical and subtropical regions**, particularly in parts of Africa, Southeast Asia, South America, and the Caribbean. - Its prevalence is much lower in temperate regions, though outbreaks can occur, especially in specific *high-risk populations*. *In the United States, it is more common among women* - In developed countries like the United States, LGV primarily affects **men who have sex with men (MSM)**, particularly those who are HIV-positive. [1] - While it can occur in women, its incidence is **significantly lower** in this population. *Penicillin is effective in early treatment* - LGV is caused by *Chlamydia trachomatis*, which is a **bacterium that lacks a peptidoglycan cell wall**, making it inherently resistant to penicillin. - The recommended treatments for LGV are **doxycycline** or **erythromycin**, not penicillin.
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