Infectious Diseases Practice Questions

Q: In AIDS, lymphadenopathy is most often due to which of the following?

Non specific enlargement of lymph node. In patients with HIV/AIDS, lymphadenopathy is a frequent clinical finding. The most common cause is **Persistent Generalized Lymphadenopathy (PGL)**, which histologically manifests as **non-specific follicular hyperplasia** (non-specific enlargement) [1]. This occurs due to the chronic immune activation and B-cell proliferation in response to the HIV virus itself, rather than a secondary opportunistic infection or malignancy [1]. PGL is defined as enlarged nodes (>1 cm) at two or more extra-inguinal sites persisting for more than 3 months without an obvious cause [1]. **Analysis of Incorrect Options:** * **A. Tuberculosis:** While TB is the most common *opportunistic infection* causing lymphadenopathy in AIDS patients (especially in India), it is statistically less frequent than the non-specific reactive changes caused by HIV itself [1]. * **B. Lymphoma:** HIV patients have a significantly higher risk of Non-Hodgkin Lymphoma (NHL), but it represents a small percentage of total lymphadenopathy cases compared to reactive hyperplasia [1]. * **D. Kaposi’s Sarcoma:** This is an AIDS-defining illness caused by HHV-8. While it can involve lymph nodes, it typically presents with characteristic cutaneous lesions and is far less common than non-specific enlargement [1]. **NEET-PG High-Yield Pearls:** * **PGL Definition:** Nodes >1cm, ≥2 extra-inguinal sites, >3 months duration [1]. * **Biopsy Indication:** In AIDS, a lymph node biopsy is indicated if there are constitutional symptoms (fever, weight loss), rapid enlargement of nodes, or asymmetrical/fixed nodes to rule out TB or Lymphoma [1]. * **Most common site for PGL:** Cervical, axillary, and posterior occipital nodes. * **Histology of PGL:** Early stage shows exuberant follicular hyperplasia; late stage shows follicular involution/depletion.

Q: Which of the following is NOT true about Salmonella hepatitis?

ALT/LDH ratio will be >5. **Explanation:** Salmonella hepatitis is a complication of enteric fever (Typhoid) characterized by liver involvement. Understanding the biochemical markers is crucial for differentiating it from viral hepatitis. **1. Why Option D is the Correct Answer (The False Statement):** In Salmonella hepatitis, the **ALT/LDH ratio is typically 5 [2]. **2. Analysis of Incorrect Options:** * **Option A:** Enteric fever classically presents with **high-grade fever** and **Faget’s sign (relative bradycardia)**, where the pulse rate does not increase proportionately with the temperature. * **Option B:** The biochemical profile often mimics **infiltrative liver disease** rather than pure hepatocellular necrosis [2]. This includes modest elevations in transaminases (usually <10 times the upper limit) and alkaline phosphatase. * **Option C:** Most cases of Salmonella hepatitis are **anicteric** (without jaundice). Clinical jaundice occurs in only 5-10% of cases and usually signifies a more severe course or complications like cholecystitis [1]. **Clinical Pearls for NEET-PG:** * **Histology:** Look for "Typhoid nodules" (small focal areas of hepatocyte necrosis with Kupffer cell hyperplasia and mononuclear infiltration). * **Widal Test:** Usually becomes positive in the 2nd week of illness [1]. * **Treatment:** Ceftriaxone or Azithromycin are preferred due to widespread multidrug resistance (MDR) and Nalidixic acid-resistant S. typhi (NARST). * **Key Differentiator:** Unlike viral hepatitis, Salmonella hepatitis rarely leads to fulminant hepatic failure.

Q: Which of the following corticosteroids is NOT used in any form of tuberculosis?

Intestinal tuberculosis. In the management of Tuberculosis (TB), corticosteroids are used as an **adjunct** to Anti-Tubercular Therapy (ATT) to reduce the harmful effects of the host's inflammatory response, prevent fibrosis, and decrease edema in critical anatomical sites. [1] **Why Intestinal TB is the Correct Answer:** Corticosteroids are generally **avoided** in Intestinal TB. The primary concern is that steroids can mask symptoms of an acute abdomen or, more critically, increase the risk of **bowel perforation** and delay the healing of tubercular ulcers. [1] Unlike other forms of TB, there is no proven survival benefit or reduction in stricture formation with steroid use in intestinal involvement. **Analysis of Other Options:** * **Miliary TB:** Steroids are indicated in severe cases with associated respiratory failure (ARDS) or adrenal insufficiency to reduce overwhelming systemic inflammation. * **Meningeal TB:** This is a **Class I indication**. Steroids (Dexamethasone or Prednisolone) are mandatory as they reduce cerebral edema, prevent vasculitis, and decrease the formation of basal exudates, significantly improving survival and neurological outcomes. [2] * **Renal TB:** Steroids are used specifically to prevent **ureteric strictures** and subsequent hydronephrosis during the early healing phase of the disease. **High-Yield Clinical Pearls for NEET-PG:** * **Absolute Indications for Steroids in TB:** Tuberculous Meningitis (TBM) and Tuberculous Pericarditis (to prevent constrictive pericarditis). [2] * **Other Indications:** Pleural effusion (if large/symptomatic), endobronchial TB (to prevent bronchiectasis), and laryngeal TB (to prevent airway obstruction). * **Standard Regimen:** Prednisolone 1 mg/kg/day for 4–6 weeks, followed by a gradual taper.

Q: All are cardiovascular manifestations of late syphilis, EXCEPT?

Pulmonary stenosis. **Explanation:** Cardiovascular syphilis is a manifestation of **Tertiary (Late) Syphilis**, typically occurring 10–30 years after the primary infection [1]. The underlying pathology is **obliterative endarteritis of the vasa vasorum**, which leads to ischemia and destruction of the elastic tissue in the tunica media (mesoaortitis). **Why Pulmonary Stenosis is the correct answer:** Syphilis primarily affects the **aorta** due to its rich supply of vasa vasorum. It does not involve the pulmonary valves or the pulmonary artery. Pulmonary stenosis is typically a congenital heart defect or a result of rheumatic heart disease, not a sequela of *Treponema pallidum* infection. **Analysis of Incorrect Options:** * **Uncomplicated Aortitis:** This is the most common manifestation. It involves asymptomatic dilation of the ascending aorta, often identified only by linear calcification on a chest X-ray. * **Saccular Aneurysm:** Weakening of the aortic media leads to aneurysm formation [2]. These are typically **saccular** (rather than fusiform) and most commonly involve the **ascending aorta**, followed by the aortic arch. * **Coronary Ostial Stenosis:** The inflammatory process and scarring at the root of the aorta can narrow the openings (ostia) of the coronary arteries, leading to angina or myocardial infarction. **High-Yield Clinical Pearls for NEET-PG:** * **Most common site:** Ascending aorta (unlike atherosclerotic aneurysms, which favor the abdominal aorta). * **Aortic Regurgitation:** Syphilitic aortitis causes dilation of the aortic ring, leading to valvular insufficiency. * **Tree-barking appearance:** Gross pathological finding of the aortic intima due to patchy subintimal scarring. * **Diagnosis:** Screening with VDRL/RPR; confirmation with FTA-ABS or TPPA. * **Treatment:** Penicillin G is the drug of choice, though it cannot reverse existing structural damage.

Q: All of the following are included in the diagnostic criteria for Clostridium difficile infection, EXCEPT:

Fever. The diagnosis of **Clostridium difficile infection (CDI)** is based on a combination of clinical symptoms and laboratory or endoscopic findings. **Explanation of the Correct Answer:** **Option D (Fever)** is the correct answer because it is a **non-specific systemic symptom** and not a formal diagnostic criterion. While patients with CDI may present with fever, leukocytosis, or abdominal pain, these are considered clinical features or markers of severity rather than definitive diagnostic criteria. **Explanation of Incorrect Options:** * **Option A (Three unformed stools):** This is the standard clinical threshold. CDI should only be tested in patients with clinically significant diarrhea (≥3 loose stools in 24 hours) that is new and unexplained. * **Option B (Detection of toxin A or B):** This is the gold standard for laboratory diagnosis. Since *C. difficile* can colonize healthy individuals, the presence of the organism (GDH) is not enough; the presence of **free toxins** (via EIA) or **toxin-producing genes** (via NAAT/PCR) must be confirmed. * **Option C (Pseudomembranes):** The visualization of yellow-white plaques (pseudomembranes) on the colonic mucosa during sigmoidoscopy or colonoscopy is **pathognomonic** for CDI and is a valid diagnostic criterion, even in the absence of lab confirmation. **High-Yield Clinical Pearls for NEET-PG:** * **Risk Factors:** Recent antibiotic use (Clindamycin, Fluoroquinolones, Cephalosporins) and PPI use. * **Toxins:** Toxin A (Enterotoxin) and Toxin B (Cytotoxin). Toxin B is 1000x more potent. * **Treatment:** Oral **Vancomycin** or **Fidaxomicin** are first-line agents. Metronidazole is now reserved for non-severe cases in resource-limited settings. * **Hypervirulent Strain:** The **NAP1/BI/027** strain produces more toxins and is associated with outbreaks.

Q: A 28-year-old man presents with a 2-day history of painful urination and cloudy penile discharge. Physical examination reveals purulent discharge expressed from the penis. Microscopic examination of the fluid shows Gram-negative diplococci within neutrophils. Which of the following is the most appropriate treatment?

Intramuscular ceftriaxone plus oral doxycycline. **Explanation:** The clinical presentation of purulent urethral discharge and the microscopic finding of **Gram-negative intracellular diplococci (GNID)** within neutrophils are pathognomonic for **Gonococcal Urethritis** caused by *Neisseria gonorrhoeae* [1]. **1. Why Option A is Correct:** Current clinical guidelines (CDC and WHO) recommend dual therapy for urethritis. **Ceftriaxone (500 mg IM single dose)** is the drug of choice for *N. gonorrhoeae* due to increasing resistance to other antibiotics [2]. **Doxycycline (100 mg BID for 7 days)** is added to empirically treat potential co-infection with *Chlamydia trachomatis*, which occurs in up to 40% of patients with gonorrhea [2]. Even if Chlamydia is not confirmed, dual therapy is the standard of care in syndromic management. **2. Why Other Options are Incorrect:** * **Options B, C, and D:** Penicillins (Penicillin G, V, and Ampicillin) are no longer used for gonorrhea. *N. gonorrhoeae* has developed high levels of resistance through **plasmid-mediated penicillinase production** (PPNG) and chromosomal mutations. These drugs would result in high treatment failure rates. **Clinical Pearls for NEET-PG:** * **Gold Standard Diagnosis:** Culture on **Thayer-Martin medium** (Chocolate agar with antibiotics). * **Most Sensitive Test:** Nucleic Acid Amplification Test (NAAT). * **Fitz-Hugh-Curtis Syndrome:** A complication in females involving perihepatitis ("violin-string" adhesions). * **Disseminated Gonococcal Infection (DGI):** Presents with the triad of tenosynovitis, dermatitis, and polyarthralgia. * **Partner Management:** Always treat the sexual partner(s) to prevent reinfection (Expedited Partner Therapy) [2].

Q: A 40-year-old woman, found to be positive for HBsAg, is excluded from blood donation due to a chronic shortage of blood. She is asymptomatic with normal liver function tests and negative serologic tests for IgM anti-HAV, anti-HBc, and anti-HCV. Repeat testing 6 months later shows the same results. Which of the following is the most appropriate statement regarding the pathophysiology of this patient's condition?

Chronic carrier state with no therapy indicated. **Explanation:** This patient presents with a persistent **HBsAg positive** status for more than 6 months, which defines **Chronic Hepatitis B infection** [1]. However, her clinical profile—asymptomatic, normal liver function tests (LFTs), and lack of other viral markers—points toward an **Inactive HBsAg Carrier State**. **1. Why Option A is Correct:** A chronic carrier is defined by the presence of HBsAg in the serum for >6 months, normal serum aminotransferases (ALT/AST), and usually low or undetectable HBV DNA levels [1]. Since the patient has normal LFTs and no symptoms, she does not meet the criteria for active chronic hepatitis (which requires elevated ALT and high viral load). In the inactive carrier state, no antiviral therapy is indicated; management consists of periodic monitoring of LFTs and HBsAg status. **2. Why Incorrect Options are Wrong:** * **Option B:** Most inactive carriers remain stable for years. While reactivation can occur (especially under immunosuppression), it is not a rule that overt hepatitis will manifest within a year. * **Option C:** The results are consistent across two tests 6 months apart. This confirms chronicity rather than laboratory error [1]. * **Option D:** Hepatitis B vaccination is ineffective in individuals already infected with HBsAg [2]. Vaccination is a preventive measure for seronegative individuals. **NEET-PG High-Yield Pearls:** * **Chronic HBV Definition:** Persistence of HBsAg for >6 months [1]. * **Inactive Carrier Profile:** HBsAg (+), HBeAg (-), Anti-HBe (+), Normal ALT, and HBV DNA <2,000 IU/mL. * **Window Period:** The interval where HBsAg and Anti-HBs are both negative; **IgM anti-HBc** is the only diagnostic marker during this phase [1]. * **Blood Donation:** Any history of HBsAg positivity is a permanent deferral for blood donation, regardless of current LFTs.

Q: What is the oropharyngeal manifestation of HIV infection?

Oral hairy leukoplakia. **Explanation:** **Oral Hairy Leukoplakia (OHL)** is a classic opportunistic manifestation of HIV infection. It is caused by the reactivation of the **Epstein-Barr Virus (EBV)** in the setting of profound immunosuppression (typically when CD4 counts fall below 200-300 cells/mm³). Clinically, it presents as white, corrugated (ribbed), non-scrapable patches, most commonly found on the **lateral borders of the tongue**. Unlike oral candidiasis, these lesions cannot be rubbed off. **Analysis of Incorrect Options:** * **B. Caries tooth:** While poor oral hygiene can occur in any patient, dental caries is not a specific or diagnostic opportunistic manifestation of HIV/AIDS. * **C. Cheilitis:** Angular cheilitis (inflammation of the corners of the mouth) can be seen in HIV due to secondary *Candida* infections or nutritional deficiencies, but it is non-specific and occurs in many other conditions (e.g., iron deficiency). * **D. Pharyngitis:** While acute HIV syndrome (seroconversion) can present with a sore throat, chronic oropharyngeal pharyngitis is not a defining opportunistic feature of HIV in the same way OHL is. **High-Yield Clinical Pearls for NEET-PG:** * **Diagnostic Significance:** OHL is considered a "highly suggestive" sign of HIV infection and often predicts the progression to AIDS. * **Histopathology:** Shows hyperkeratosis, parakeratosis, and "ballooning cells" in the upper layers of the epithelium. * **Treatment:** Usually, no specific treatment is required other than initiating **Antiretroviral Therapy (ART)**, which typically leads to the resolution of the lesions as the immune system recovers. * **Differential Diagnosis:** Must be distinguished from **Oral Candidiasis** (which is scrapable and shows pseudohyphae) and **Oral Leukoplakia** (a precancerous lesion associated with tobacco).

Q: A 33-year-old woman presented with a 1-day history of fever and chills. On examination, she was febrile with a blood pressure of 70/40 mmHg. Over several hours, a widespread erythrodermic rash developed, and she collapsed. Further questioning revealed that the patient had removed a tampon shortly before presentation as she had just ceased menstruating. What is the most likely diagnosis?

Toxic shock syndrome. ### Explanation **Correct Answer: D. Toxic shock syndrome (TSS)** The clinical presentation is classic for **Staphylococcal Toxic Shock Syndrome**. The diagnosis is based on the rapid onset of high fever, hypotension (shock), and a diffuse erythrodermic rash (resembling a sunburn) that typically desquamates 1–2 weeks later. The mention of **tampon use** is a high-yield "buzzword" for TSS, as highly absorbent tampons provide a niche for *Staphylococcus aureus* to provide **TSST-1 (Toxic Shock Syndrome Toxin-1)**. This toxin acts as a **superantigen**, non-specifically cross-linking MHC II and T-cell receptors, leading to a massive "cytokine storm" (IL-1, IL-2, TNF-α, and IFN-γ) [1]. **Why the other options are incorrect:** * **A. Haemolytic uraemic syndrome (HUS):** Typically follows a prodrome of bloody diarrhea (EHEC O157:H7). It is characterized by the triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury, not an erythrodermic rash and sudden shock. * **B. E. coli sepsis:** While it can cause hypotension and fever, it does not typically present with a diffuse erythrodermic rash or a specific association with tampon use. * **C. Fungal infection:** Systemic fungal infections (like Candidemia) usually occur in immunocompromised patients and follow a more subacute course rather than this hyper-acute presentation. **NEET-PG High-Yield Pearls:** * **Causative Agent:** *S. aureus* (TSST-1) or *S. pyogenes* (Exotoxin A). Streptococcal TSS is more likely to have an associated necrotizing soft tissue infection [1]. * **Criteria:** Fever >38.9°C, SBP <90 mmHg, diffuse rash, and involvement of ≥3 organ systems (GI, Muscular, Renal, Hepatic, Hematologic, or CNS). * **Management:** Aggressive fluid resuscitation, removal of the source (tampon/packing), and antibiotics (Clindamycin is added to inhibit toxin production).

Question 1

A 24-year-old woman presents with fever, chills, and rigors. On physical examination, her temperature is 39.4°C, blood pressure 100/60 mm Hg, pulse 110/min, and oxygen saturation 95%. There is a 3/6 pansystolic murmur at the right sternal border, which increases with inspiration. Her arms show multiple tattoos and needle marks from injection drug use. Blood cultures are positive for S. aureus, and she is started on appropriate antibiotics. Her renal function is mildly impaired, and her urinalysis is positive for protein with red blood cell casts on microscopy. Which of the following mechanisms is the most likely explanation for her renal abnormalities?

Accepted Answer

High level of circulating immune complexes

Answer

Septic emboli

Answer

Cardiac failure with prerenal azotemia

Answer

Fungal disease

Question 2

In AIDS, lymphadenopathy is most often due to which of the following?

Accepted Answer

Non specific enlargement of lymph node

Answer

Tuberculosis

Answer

Lymphoma

Answer

Kaposi's sarcoma

Question 3

Which of the following is NOT true about Salmonella hepatitis?

Accepted Answer

ALT/LDH ratio will be >5

Answer

High grade fever with relative bradycardia

Answer

Biochemical profile suggestive of infiltrative liver disease pattern

Answer

Usually anicteric

Question 4

Which of the following corticosteroids is NOT used in any form of tuberculosis?

Accepted Answer

Intestinal tuberculosis

Answer

Miliary tuberculosis

Answer

Meningeal tuberculosis

Answer

Renal tuberculosis

Question 5

All are cardiovascular manifestations of late syphilis, EXCEPT?

Accepted Answer

Pulmonary stenosis

Answer

Uncomplicated aoitis

Answer

Saccular aneurysm (usually of the ascending aorta)

Answer

Coronary ostial stenosis

Question 6

All of the following are included in the diagnostic criteria for Clostridium difficile infection, EXCEPT:

Accepted Answer

Fever

Answer

Three unformed stools in 24 hours for 2 days

Answer

Detection of toxin A or B in stool

Answer

Pseudomembranes observed during colonoscopy

Question 7

A 28-year-old man presents with a 2-day history of painful urination and cloudy penile discharge. Physical examination reveals purulent discharge expressed from the penis. Microscopic examination of the fluid shows Gram-negative diplococci within neutrophils. Which of the following is the most appropriate treatment?

Accepted Answer

Intramuscular ceftriaxone plus oral doxycycline

Answer

Oral penicillin G

Answer

Intramuscular penicillin V

Answer

Intramuscular ampicillin and oral penicillin V

Question 8

A 40-year-old woman, found to be positive for HBsAg, is excluded from blood donation due to a chronic shortage of blood. She is asymptomatic with normal liver function tests and negative serologic tests for IgM anti-HAV, anti-HBc, and anti-HCV. Repeat testing 6 months later shows the same results. Which of the following is the most appropriate statement regarding the pathophysiology of this patient's condition?

Accepted Answer

Chronic carrier state with no therapy indicated

Answer

Clinically overt hepatitis will occur within 1 year

Answer

Erroneous test results that need to be repeated

Answer

Hepatitis B vaccination series is now required

Question 9

What is the oropharyngeal manifestation of HIV infection?

Accepted Answer

Oral hairy leukoplakia

Answer

Caries tooth

Answer

Cheilitis

Answer

Pharyngitis

Question 10

A 33-year-old woman presented with a 1-day history of fever and chills. On examination, she was febrile with a blood pressure of 70/40 mmHg. Over several hours, a widespread erythrodermic rash developed, and she collapsed. Further questioning revealed that the patient had removed a tampon shortly before presentation as she had just ceased menstruating. What is the most likely diagnosis?

Accepted Answer

Toxic shock syndrome

Answer

Haemolytic uraemic syndrome

Answer

E. coli sepsis

Answer

Fungal infection

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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