Infectious Diseases

Infectious Diseases Indian Medical PG Question 1: Which of the following is NOT a mechanism of antibiotic resistance?

• A. Efflux pump activity
• B. Inactivation by enzymes such as beta-lactamase
• C. Modification of drug target sites
• D. Increased drug absorption (Correct Answer)

Infectious Diseases Explanation: ***Increased drug absorption*** - **Increased drug absorption** would lead to a higher intracellular concentration of the antibiotic, making it *more potent* against the bacteria rather than contributing to resistance. - Antibiotic resistance mechanisms aim to *reduce the effective concentration* of the drug at its target site or *alter the target itself*. *Efflux pump activity* - **Efflux pumps** are bacterial membrane proteins that actively pump antibiotics out of the bacterial cell [3]. - This mechanism *reduces the intracellular concentration* of the antibiotic, preventing it from reaching its therapeutic target [3]. *Inactivation by enzymes such as beta-lactamase* - Bacteria can produce enzymes like **beta-lactamase** that *chemically modify or degrade* the antibiotic molecule, rendering it inactive [2]. - This is a common mechanism of resistance against **beta-lactam antibiotics** (e.g., penicillin, cephalosporins) [2]. *Modification of drug target sites* - Bacteria can develop mutations that *alter the structure of the antibiotic's target site*, such as a bacterial ribosome or cell wall component [1]. - This change in the target means the antibiotic can no longer bind effectively or interfere with cellular processes, thus *losing its efficacy* [1].

Infectious Diseases Indian Medical PG Question 2: Which of the following statements about antibiotic resistance in N. gonorrhoeae is FALSE?

• A. Ceftriaxone resistance typically involves alterations in the penA gene
• B. Resistance to fluoroquinolones is often due to mutations in gyrA and parC genes
• C. Spectinomycin resistance remains extremely rare globally
• D. Tetracycline resistance is primarily mediated by beta-lactamase production (Correct Answer)

Infectious Diseases Explanation: ***Tetracycline resistance is primarily mediated by beta-lactamase production*** - This statement is **FALSE**. Beta-lactamases (such as TEM-1 and TEM-135) in *N. gonorrhoeae* confer resistance to **penicillins and related beta-lactam antibiotics**, not tetracyclines. - **Tetracycline resistance** in *N. gonorrhoeae* is mediated by two distinct mechanisms: **plasmid-borne TetM determinants** (conferring high-level resistance through ribosomal protection) and **chromosomal mutations** (affecting mtrR, penB, and rpsJ genes, leading to increased efflux or altered ribosomal targets). - Beta-lactamase production and tetracycline resistance are independent resistance mechanisms. *Ceftriaxone resistance typically involves alterations in the penA gene* - This is **TRUE**. Ceftriaxone resistance in *N. gonorrhoeae* is primarily associated with **mosaic _penA_ alleles** encoding altered penicillin-binding protein 2 (PBP2). - These mosaic alleles result in decreased affinity of PBP2 for cephalosporins, reducing drug effectiveness. - Additional mechanisms include mtrR mutations (increasing efflux) and penB mutations (decreasing permeability). *Resistance to fluoroquinolones is often due to mutations in gyrA and parC genes* - This is **TRUE**. Fluoroquinolone resistance in *N. gonorrhoeae* primarily results from mutations in the **quinolone resistance-determining regions (QRDRs)** of **_gyrA_** and **_parC_** genes. - These genes encode subunits of DNA gyrase and topoisomerase IV respectively, the primary targets of fluoroquinolones. - The most common mutation is S91F in GyrA, with additional mutations in ParC contributing to higher-level resistance. *Spectinomycin resistance remains extremely rare globally* - This is **TRUE**. Spectinomycin resistance in *N. gonorrhoeae* remains **extremely rare worldwide**, with only sporadic case reports. - Resistance is mediated by mutations in the **16S rRNA gene** (particularly at position 1192), but this mechanism has not become widespread. - Spectinomycin remains a valuable alternative therapy, particularly for patients with cephalosporin allergies or in areas with cephalosporin resistance.

Infectious Diseases Indian Medical PG Question 3: A healthcare worker develops fever, night sweats, and cough. Sputum shows acid-fast bacilli. What is the next diagnostic test?

• A. Gram stain
• B. Serology for TB
• C. NAAT for TB (Correct Answer)
• D. Sputum culture

Infectious Diseases Explanation: ***NAAT for TB*** - Nucleic Acid Amplification Tests (**NAAT**) rapidly confirm the presence of **Mycobacterium tuberculosis** DNA or RNA, crucial after an **acid-fast bacilli (AFB) smear** is positive [1]. - This test offers high sensitivity and specificity and can also detect **drug resistance**, guiding immediate treatment decisions [1]. *Gram stain* - A **Gram stain** is not appropriate for **Mycobacterium tuberculosis** because these bacteria have a unique cell wall that makes them **acid-fast**, not readily stained by the Gram method. - The initial finding of **acid-fast bacilli** already indicates a general type of organism, making a Gram stain redundant and uninformative for TB. *Serology for TB* - **Serological tests for TB** (detecting antibodies to M. tuberculosis) are generally **not recommended** for the diagnosis of active pulmonary TB due to their **poor sensitivity and specificity**. - They have limited utility in diagnosing active disease and are not endorsed by major health organizations for this purpose. *Sputum culture* - **Sputum culture** is the **gold standard** for confirming TB diagnosis and for **drug susceptibility testing**, but it is a **slow process** (taking several weeks) [2]. - While essential for definitive diagnosis and resistance profiling, it is not the **"next" rapid diagnostic test** required given the positive AFB smear.

Infectious Diseases Indian Medical PG Question 4: Why is a regimen of four drugs recommended for a TB patient on the first visit?

• A. To prevent emergence of drug-resistant strains (Correct Answer)
• B. To reduce bacterial load effectively
• C. To minimize treatment duration
• D. None of the options

Infectious Diseases Explanation: ***To prevent emergence of drug-resistant strains*** - Using a **four-drug regimen** at the initial stage significantly reduces the likelihood of **Mycobacterium tuberculosis** developing resistance to any single drug. - This strategy ensures that even if a small number of bacteria are naturally resistant to one drug, the other drugs will still be effective in killing them, preventing the proliferation of **resistant strains**. *To minimize treatment duration* - While a multi-drug regimen is effective, its primary goal is not to minimize treatment duration but rather to ensure **eradication of the infection** and prevent resistance. - Treatment duration is determined by the need to kill both actively multiplying and dormant bacteria, which typically takes several months even with multiple drugs. *To reduce bacterial load effectively* - Reducing bacterial load is certainly a goal of TB treatment, but the use of four drugs is specifically aimed at achieving this while simultaneously preventing **drug resistance**. - A single effective drug could reduce bacterial load, but it would quickly lead to the emergence of resistant bacteria, making the long-term goal of **cure** impossible. *None of the options* - This option is incorrect because the primary reason for a **four-drug regimen** in TB treatment is indeed to prevent the emergence of **drug-resistant strains**.

Infectious Diseases Indian Medical PG Question 5: Which of the following is the best parameter to predict virulence of acute infectious illness?

• A. Incidence
• B. Secondary attack rate
• C. Case fatality rate (Correct Answer)
• D. Crude death rate

Infectious Diseases Explanation: ***Case fatality rate*** - The **case fatality rate (CFR)** directly measures the **proportion of individuals diagnosed with a disease who die from it**, reflecting the pathogen's ability to cause death. - A higher CFR indicates greater **virulence** and a more severe disease outcome, making it the most direct predictor of an illness's ability to harm. *Incidence* - **Incidence** measures how often a disease occurs in a population over a specified period, indicating the **risk of contracting the disease**. - It does not provide information about the **severity** or **lethality** of the disease once contracted. *Secondary attack rate* - The **secondary attack rate** quantifies the probability that infection will occur among susceptible individuals within a particular group exposed to a primary case. - While it measures **transmissibility** and the potential for spread within a close group, it does not reflect the **virulence** or severity of the illness itself. *Crude death rate* - The **crude death rate** is the total number of deaths from all causes in a population over a given period, divided by the total population. - This parameter measures **overall mortality** in a population and is not specific to the deaths caused by a particular infectious illness, nor does it solely reflect its virulence.

Infectious Diseases Indian Medical PG Question 6: An adult male patient presented in the OPD with complaints of cough and fever for 3 months and haemoptysis off and on. His sputum was positive for AFB. On probing it was found that he had already received treatment with RHZE for 3 weeks from a nearby hospital and discontinued. How will you categorize and manage the patient?

• A. Category I: New case, intensive phase (2RHZE) (Correct Answer)
• B. Category II: Relapse, intensive phase (2RHZES)
• C. Category IV: Multi-drug resistant TB, intensive phase (individualized regimen)
• D. Category II: Treatment after default, intensive phase (2RHZE)

Infectious Diseases Explanation: ***Category I: New case, intensive phase (2RHZE)*** - This patient meets the criteria for a **newly diagnosed TB case** as they have not received more than 4 weeks of anti-TB treatment previously [1]. - The standard intensive phase regimen for new cases is **2 months of Rifampicin, Isoniazid, Pyrazinamide, and Ethambutol (2RHZE)** [1]. *Category II: Relapse, intensive phase (2RHZES)* - **Relapse** applies to patients who were previously treated for TB, declared cured, but present again with active disease. This patient had discontinued treatment after only 3 weeks, so it's not a relapse. - The intensive phase for relapse cases typically includes **Streptomycin (S)** in addition to RHZE, which is not indicated here. *Category IV: Multi-drug resistant TB, intensive phase (individualized regimen)* - **Multi-drug resistant TB (MDR-TB)** is diagnosed when the TB bacilli are resistant to at least both Rifampicin and Isoniazid. While treatment discontinuation increases the risk of resistance [2], it cannot be assumed without **drug susceptibility testing (DST)**. - An individualized regimen is appropriate for MDR-TB, but more information (like DST results) is needed before categorizing it as such. *Category II: Treatment after default, intensive phase (2RHZE)* - **Default** usually refers to patients who interrupted their treatment for 2 consecutive months or more. This patient only took treatment for 3 weeks, which does not constitute a default in the context of requiring a re-treatment regimen. - While this option mentions "intensive phase (2RHZE)", the categorization of "Treatment after default" is inaccurate given the short duration of initial treatment.

Infectious Diseases Indian Medical PG Question 7: In a patient with suspected sepsis, which of the following is the MOST appropriate initial intervention?

• A. Start vasopressor support as first-line treatment
• B. Obtain blood cultures and start broad-spectrum antibiotics immediately (Correct Answer)
• C. Begin aggressive fluid restriction to prevent organ dysfunction
• D. Wait for culture results before starting any treatment

Infectious Diseases Explanation: ***Obtain blood cultures and start broad-spectrum antibiotics immediately*** - This is the **most appropriate initial intervention** following the **Surviving Sepsis Campaign Hour-1 Bundle** - Blood cultures should be obtained **before** antibiotics when possible, but antibiotic administration should not be delayed beyond 1 hour of sepsis recognition - **Early antibiotic therapy** (within 1 hour) significantly reduces mortality in sepsis - Broad-spectrum coverage is initiated empirically, then narrowed based on culture results and clinical response *Begin aggressive fluid restriction to prevent organ dysfunction* - This is **completely contraindicated** in sepsis management - Sepsis causes **vasodilation and capillary leak** leading to relative hypovolemia - The Surviving Sepsis Campaign recommends **aggressive fluid resuscitation** with 30 mL/kg crystalloid bolus within 3 hours - Fluid restriction would worsen **tissue hypoperfusion** and organ dysfunction *Start vasopressor support as first-line treatment* - Vasopressors are **second-line** therapy in sepsis - They should only be initiated when **fluid resuscitation alone** is insufficient to maintain MAP ≥65 mmHg - Starting vasopressors before adequate fluid resuscitation can worsen tissue perfusion *Wait for culture results before starting any treatment* - Sepsis is a **medical emergency** where every hour of delayed antibiotic therapy increases mortality by approximately 7-8% - Treatment must be initiated **immediately** based on clinical suspicion - Cultures are obtained to guide **de-escalation** of therapy, not to delay initiation

Infectious Diseases Indian Medical PG Question 8: Sepsis screen includes all the following EXCEPT?

• A. Total leucocyte count
• B. Absolute neutrophil count
• C. Platelet count (Correct Answer)
• D. IT ratio

Infectious Diseases Explanation: ***Platelet count*** - While **thrombocytopenia** can be a feature of severe sepsis or septic shock, it is not a primary component of the initial sepsis screen. [1] - Sepsis screens typically focus on markers of inflammation and infection burden rather than coagulopathy, which is a later complication. [1] *Total leucocyte count* - A **high (leukocytosis)** or **low (leukopenia)** total leucocyte count is an important indicator of infection and systemic inflammatory response. [1] [2] - It is a standard component of sepsis screening criteria, helping to assess the host's response to infection. *Absolute neutrophil count* - Neutrophils are the primary immune cells involved in fighting bacterial infections; therefore, an elevated **absolute neutrophil count** often suggests an ongoing infection. [1] - It provides a more specific measure of granulocyte response compared to the total leucocyte count, making it a valuable part of sepsis screening. [2] *IT ratio* - The **IT ratio** (Immature to Total neutrophil ratio) measures the proportion of immature neutrophils (bands) to total neutrophils. - An elevated IT ratio indicates a "left shift," suggesting the bone marrow is rapidly producing and releasing immature neutrophils in response to severe infection.

Infectious Diseases Indian Medical PG Question 9: Best guide for the management of Resuscitation is:

• A. Blood pressure
• B. Urine output (Correct Answer)
• C. Saturation of Oxygen
• D. CVP

Infectious Diseases Explanation: ***Urine output*** - **Urine output** is an excellent indicator of **renal perfusion** and overall tissue perfusion, reflecting the adequacy of fluid resuscitation [1]. - Maintaining a urine output of **0.5-1 mL/kg/hr** is generally a target for effective resuscitation in critically ill patients. *Blood pressure* - While blood pressure is a vital sign, it can be maintained within normal limits through **compensatory mechanisms** (e.g., vasoconstriction) even when significant hypovolemia or shock is present [1]. - Relying solely on blood pressure may lead to inadequate resuscitation as it can **normalize transiently** without true restoration of tissue perfusion. *Saturation of Oxygen* - **Oxygen saturation** primarily reflects the oxygenation status of the blood (**peripheral oxygen delivery**), not necessarily the adequacy of tissue perfusion or volume status [1]. - Normal oxygen saturation can occur in hypotensive or hypoperfused states if the lungs are functioning adequately. *CVP* - **Central venous pressure (CVP)** is a measure of the filling pressure of the right atrium and an indicator of **right ventricular preload** [1]. - While CVP can offer some insight into fluid status, it is often a **poor predictor of fluid responsiveness** and can be affected by many factors unrelated to intravascular volume, such as intrathoracic pressure and right ventricular function [1].

Infectious Diseases Indian Medical PG Question 10: A 64-year-old woman presents to the emergency room with flank pain and fever, accompanied by dysuria for the past three days. Blood and urine cultures are obtained, and she is started on intravenous ciprofloxacin. Six hours after admission, she becomes tachycardic and her blood pressure drops. Her intravenous fluid is normal saline at a rate of 100 mL/h. Her current vital signs are blood pressure of 79/43 mm Hg, heart rate of 128 beats per minute, respiratory rate of 26 breaths per minute, and a temperature of 39.2°C (102.5°F). She appears drowsy yet uncomfortable. Her extremities are warm with trace edema. What is the best next course of action?

• A. Begin norepinephrine infusion and titrate to mean arterial pressure greater than 65 mm Hg.
• B. Add vancomycin to her antibiotic regimen for improved gram-positive coverage.
• C. Administer a bolus of NS. (Correct Answer)
• D. Administer IV hydrocortisone at stress dose.

Infectious Diseases Explanation: ***Administer a bolus of NS.*** - The patient is showing signs of **septic shock** (hypotension, tachycardia, fever, altered mental status) likely due to pyelonephritis [1]. The initial management of septic shock involves aggressive **intravenous fluid resuscitation** to restore circulating volume and improve tissue perfusion [3]. - Her current IV fluid rate of 100 mL/h is insufficient given her clinical picture, and a **fluid bolus** (e.g., 500-1000 mL of normal saline over 15-30 minutes) is the immediate priority to address hypotension [4]. *Begin norepinephrine infusion and titrate to mean arterial pressure greater than 65 mm Hg.* - While **norepinephrine** is the first-line vasopressor for septic shock, it should generally be initiated after initial **fluid resuscitation** has failed to improve hypotension [3]. - Administering vasopressors without adequate fluid repletion can worsen tissue hypoperfusion. *Add vancomycin to her antibiotic regimen for improved gram-positive coverage.* - The patient is already on ciprofloxacin, a broad-spectrum antibiotic. While **broadening antibiotic coverage** is important in sepsis, it's not the immediate life-saving intervention when the patient is in shock due to hypovolemia [2]. - Adding vancomycin would be considered if there was concern for **MRSA** or other resistant gram-positive infections, but hemodynamic stabilization with fluids takes precedence. *Administer IV hydrocortisone at stress dose.* - **Hydrocortisone** may be considered in septic shock patients who are refractory to fluids and vasopressors, or those with known adrenal insufficiency. - However, it is not the primary intervention for initial hemodynamic stabilization in a patient who has not yet received adequate **fluid resuscitation**.

Infectious Diseases Flashcard 1 of 10

Question: ICU inpatients of community acquired pneumonia are treated with:_____ + azithromycin or fluoroquinolone

Answer: -lactam

Infectious Diseases Flashcard 2 of 10

Question: In which opportunistic infections can ART be started immediately?_____

Answer: MAC, cryptosporidiosis, microsporidiosis and PML

Infectious Diseases Flashcard 3 of 10

Question: List of pathogens that can cause endocarditis in IVDUs:_____Candida albicans

Answer: Staphylococcus aureus

Infectious Diseases Flashcard 4 of 10

Question: _____ are susceptible to acute bacterial endocarditis of the tricuspid valve from staphylococcus aureus

Answer: IV drug users

Infectious Diseases Flashcard 5 of 10

Question: Secondary bacterial pneumonia is typically _____, Haemophilus influenzae, or Strep pneumo superimposed on Influenza

Answer: Staph aureus

Infectious Diseases Flashcard 6 of 10

Question: _____ caused by Coxiella burnetti is associated with hepatitis, interstitial pneumonia and culture-negative endocarditis (visceral complications)

Answer: Q fever

Infectious Diseases Flashcard 7 of 10

Question: a case of kala azar is defined as

Answer: fever>2 weeks + splenomegaly+ RDT or biopsy positive

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Infectious Diseases Flashcard 8 of 10

Question: 5c341ef5ff5d429098121a2448710a0a-ao-3

Answer: rules of HART in HIV

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Infectious Diseases Flashcard 9 of 10

Question: TB patient becomes 95% non infective within _____ of treatment

Answer: 2 weeks

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Infectious Diseases Flashcard 10 of 10

Question: _____% of Hep C cases are subclinical

Answer: 80-90

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