Emerging Antimicrobial Resistance — MCQs
Which of the following is NOT a core component of the WHO's global STI control strategy?
Which of the following statements about antibiotic resistance in N. gonorrhoeae is FALSE?
The initial origin of new drug resistance genes in bacteria most commonly occurs due to:
Which of the following strategies are part of the National Leprosy Control Programme?
Drug resistance is not transmitted by-
Which of the following is NOT a criterion for defining extensively drug-resistant tuberculosis (XDR-TB)?
Production of inactivating enzymes is an important mechanism of drug resistance for all of these antibiotics EXCEPT
Which of the following statements about Campylobacter jejuni is correct?
Following are true of Gram negative bacterial cell wall compared to Gram positive bacteria except:
What is the drug of choice for organism producing the following colonies?
Emerging Antimicrobial Resistance Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following is NOT a core component of the WHO's global STI control strategy?
- A. Case management
- B. Universal mandatory screening (Correct Answer)
- C. Strategic information systems
- D. Prevention services
Explanation: ***Universal mandatory screening*** - While screening is part of STI control, **universal mandatory screening** for all STIs in the general population is not a core component of the WHO's strategy due to feasibility, cost, and ethical considerations. - The strategy emphasizes **targeted screening** for at-risk populations and opportunistic screening. *Case management* - **Case management**, including accurate diagnosis and effective treatment, is a critical component for managing current infections and preventing further transmission. - This involves syndromic or etiologic approaches to treatment and partner notification. *Strategic information systems* - **Strategic information systems** are essential for monitoring trends, evaluating interventions, and informing policy decisions related to STI control. - This includes surveillance data, program monitoring, and research. *Prevention services* - **Prevention services** are a cornerstone of the WHO's strategy, aiming to reduce the incidence of new infections. - These services encompass health education, condom promotion and distribution, vaccination, and pre-exposure prophylaxis (PrEP).
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)
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.
Question 3: The initial origin of new drug resistance genes in bacteria most commonly occurs due to:
- A. Translation
- B. Mutation (Correct Answer)
- C. Conjugation
- D. Transduction
Explanation: ***Mutation*** - **Random genetic changes** in bacteria can alter drug targets or introduce drug-inactivating enzymes, leading to resistance. - **Spontaneous mutations** in the bacterial genome are the primary source of new resistance genes that did not previously exist in the bacterial population. - While mutations occur at low frequency, they are the fundamental mechanism by which novel resistance traits first arise. *Translation* - This is the process of synthesizing proteins from mRNA; it is a fundamental cellular process and not a cause of drug resistance. - Errors in translation are generally lethal to the cell and do not typically confer specific drug-resistant phenotypes. *Conjugation* - This is a mechanism for **horizontal gene transfer** where bacteria directly transfer genetic material, including resistance genes, via a pilus. - While conjugation is the **most important mechanism for spreading resistance** in clinical settings, it transfers pre-existing resistance genes rather than creating new ones. *Transduction* - This is another form of **horizontal gene transfer** involving bacteriophages (viruses) carrying bacterial genes, including resistance genes, between bacteria. - Similar to conjugation, transduction is a mechanism for the **transfer** of pre-existing resistance genes, not their original creation.
Question 4: Which of the following strategies are part of the National Leprosy Control Programme?
- A. Early detection of cases and short course multi-drug therapy (Correct Answer)
- B. Chemoprophylaxis with dapsone and rehabilitation
- C. Short course multi-drug therapy and chemoprophylaxis
- D. Rehabilitation and early detection of cases
Explanation: ***Early detection of cases and short course multi-drug therapy*** - The primary strategy of the National Leprosy Control Programme (NLCP) is to actively identify new cases early to prevent disabilities. - **Multi-drug therapy (MDT)**, a short-course regimen, is administered to cure the disease and interrupt transmission. - This combination represents the **core control strategy** of NLCP. *Chemoprophylaxis with dapsone and rehabilitation* - **Chemoprophylaxis with dapsone** is not a standard strategy under NLCP due to concerns about resistance and limited effectiveness for mass prevention. - **Rehabilitation** is important for disability management but is a secondary/tertiary prevention strategy, not a primary control measure. *Short course multi-drug therapy and chemoprophylaxis* - While **MDT** is a cornerstone of NLCP, **chemoprophylaxis** is not included as a widespread intervention. - The focus remains on treating diagnosed cases rather than mass preventive drug administration. *Rehabilitation and early detection of cases* - **Early detection** is indeed a key component, but pairing it with **rehabilitation** alone misses the critical treatment component. - The core control strategy requires both early detection **and MDT treatment**, not just detection and rehabilitation.
Question 5: Drug resistance is not transmitted by-
- A. Plasmids
- B. Ribosomes (Correct Answer)
- C. Chromosomes
- D. Transposons
Explanation: ***Ribosomes*** - Ribosomes are responsible for **protein synthesis** and do not carry or transmit genetic information for **drug resistance**. - While ribosomal mutations can sometimes lead to drug resistance, the ribosome itself is not a vehicle for its transmission between bacteria. *Plasmids* - **Plasmids** are small, extrachromosomal DNA molecules that can replicate independently and are a primary means of **horizontal gene transfer** for drug resistance genes. - They can be easily transferred between bacteria through **conjugation**, rapidly spreading resistance. *Chromosomes* - **Drug resistance genes** can be located on the bacterial chromosome and are passed down to daughter cells during **vertical gene transfer** (cell division). - While less frequent for initial acquisition compared to plasmids, chromosomal mutations and integrated resistance genes are significant causes of **antibiotic resistance**. *Transposons* - **Transposons**, or jumping genes, are DNA sequences that can move from one location in the genome to another, including between **plasmids and chromosomes**. - They often carry **antibiotic resistance genes** and facilitate their spread within a bacterial genome or between different genetic elements.
Question 6: Which of the following is NOT a criterion for defining extensively drug-resistant tuberculosis (XDR-TB)?
- A. Isoniazid + Rifampicin + Fluoroquinolone
- B. Isoniazid + Rifampicin + Ethambutol + Fluoroquinolone
- C. Fluoroquinolone (Correct Answer)
- D. Isoniazid + Rifampicin + Kanamycin
Explanation: ***Fluoroquinolone*** - Resistance to **fluoroquinolone alone** is NOT a criterion for XDR-TB because XDR-TB requires a **baseline of MDR-TB** (resistance to both rifampicin and isoniazid) plus additional resistances. - XDR-TB definition (WHO 2021): **MDR-TB** + resistance to **any fluoroquinolone** + resistance to **at least one Group A drug** (bedaquiline or linezolid). - Fluoroquinolone resistance in isolation does not meet any of these combined criteria. *Isoniazid + Rifampicin + Fluoroquinolone* - This represents **MDR-TB** (rifampicin + isoniazid resistance) plus **fluoroquinolone resistance**. - This is a partial criterion approaching XDR-TB but still requires additional resistance to at least one Group A drug (bedaquiline or linezolid) for complete XDR-TB classification. - However, this combination includes the essential MDR-TB base and fluoroquinolone component. *Isoniazid + Rifampicin + Ethambutol + Fluoroquinolone* - This includes **MDR-TB** (rifampicin + isoniazid), **fluoroquinolone resistance**, and ethambutol (first-line drug). - While ethambutol resistance alone doesn't define XDR-TB, this combination includes the critical MDR-TB and fluoroquinolone components required for XDR-TB classification. - Similar to above, would need Group A drug resistance for complete XDR-TB. *Isoniazid + Rifampicin + Kanamycin* - This represents **MDR-TB** plus resistance to **kanamycin** (a second-line injectable). - Under previous WHO definitions (pre-2021), injectable resistance was part of XDR-TB criteria. - This combination includes the MDR-TB base essential for any XDR-TB classification, though it lacks fluoroquinolone resistance.
Question 7: Production of inactivating enzymes is an important mechanism of drug resistance for all of these antibiotics EXCEPT
- A. Quinolone (Correct Answer)
- B. Penicillin
- C. Chloramphenicol
- D. Aminoglycoside
Explanation: ***Quinolone*** - The primary mechanisms of resistance to **quinolones** involve mutations in the **gyrase** and **topoisomerase IV** enzymes or efflux pump overexpression, rather than enzymatic inactivation of the drug itself. - Unlike other antibiotic classes listed, quinolones are not typically susceptible to bacterial enzymes that degrade or modify their structure. *Penicillin* - **Penicillins** are highly susceptible to inactivation by **beta-lactamase enzymes**, which hydrolyze the beta-lactam ring, rendering the antibiotic ineffective. - This enzymatic degradation is a major mechanism of resistance developed by many bacterial species to penicillin and other beta-lactam antibiotics. *Chloramphenicol* - Resistance to **chloramphenicol** is primarily mediated by the enzyme **chloramphenicol acetyltransferase (CAT)**, which acetylates the drug, preventing its binding to the bacterial ribosome. - This enzymatic modification is a classic example of drug inactivation leading to resistance. *Aminoglycoside* - **Aminoglycosides** are frequently inactivated by a variety of **aminoglycoside-modifying enzymes (AMEs)**, such as acetyltransferases, phosphoryltransferases, and nucleotidyltransferases. - These enzymes add chemical moieties to the aminoglycoside molecule, preventing its binding to the bacterial ribosome and inhibiting protein synthesis.
Question 8: Which of the following statements about Campylobacter jejuni is correct?
- A. Gram-positive coccus
- B. Most often occurs several days after consumption of undercooked chicken. (Correct Answer)
- C. Symptoms may initially mimic appendicitis
- D. Macrolides should be used in all cases
Explanation: ***Most often occurs several days after consumption of undercooked chicken.*** - *Campylobacter jejuni* infections are typically acquired through the consumption of **contaminated food or water**, with **undercooked poultry** being a common source. - The **incubation period** for *Campylobacter* gastroenteritis is usually **2 to 5 days**, explaining the delay between consumption and symptom onset. - This is the most characteristic epidemiological feature of *Campylobacter* infection. *Gram-positive coccus* - *Campylobacter jejuni* is a **Gram-negative, curved (seagull-shaped) rod**, not a Gram-positive coccus. - Its characteristic **spiral or S-shaped morphology** and staining properties are key for laboratory identification. - It is microaerophilic and grows best at 42°C. *Symptoms may initially mimic appendicitis* - While *Campylobacter* infections can cause **abdominal pain** and sometimes **right lower quadrant tenderness** (particularly in children), this is not the most characteristic or common presentation. - The hallmark feature is **acute diarrhea** (often bloody), which helps differentiate it from appendicitis. - When mimicking appendicitis does occur, it's typically due to mesenteric adenitis rather than the primary infection pattern. *Macrolides should be used in all cases* - Most *Campylobacter* infections are **self-limiting** and do not require antibiotic treatment. - **Macrolides** (e.g., azithromycin, erythromycin) are reserved for **severe cases**, immunocompromised patients, or those with prolonged symptoms. - Routine antibiotic use is not recommended for uncomplicated cases and may contribute to antimicrobial resistance.
Question 9: Following are true of Gram negative bacterial cell wall compared to Gram positive bacteria except:
- A. Thinner
- B. Presence of lipopolysaccharide
- C. Presence of outer membrane
- D. Presence of Teichoic acid (Correct Answer)
Explanation: ***Presence of Teichoic acid*** - **Teichoic acid** is a unique component of the cell wall in **Gram-positive bacteria**, playing a role in cell wall structure and antigenicity. - Its presence is **not a characteristic of Gram-negative bacteria**, making this statement the exception. *Thinner* - The cell wall of **Gram-negative bacteria** is indeed **thinner** than that of Gram-positive bacteria. - This **thin peptidoglycan layer** (2-3 nm) is much less substantial compared to the thick peptidoglycan layer (20-80 nm) of Gram-positive bacteria. *Presence of lipopolysaccharide* - **Lipopolysaccharide (LPS)**, or endotoxin, is a characteristic component of the **outer membrane** of Gram-negative bacteria. - LPS contributes to the **pathogenicity** of Gram-negative bacteria and is absent in Gram-positive bacteria. *Presence of outer membrane* - **Gram-negative bacteria** have a unique **outer membrane** that lies external to the thin peptidoglycan layer. - This outer membrane contains LPS and porins, and is a distinguishing feature **absent in Gram-positive bacteria**, which have only a single cytoplasmic membrane.
Question 10: What is the drug of choice for organism producing the following colonies?
- A. Erythromycin
- B. Ciprofloxacin (Correct Answer)
- C. Ceftriaxone
- D. No treatment with approx. 100% mortality
Explanation: ***Ciprofloxacin*** - The image displays characteristic **"Medusa head" colonies**, which are pathognomonic for *Bacillus anthracis* (anthrax). - **Ciprofloxacin** is a fluoroquinolone and is the **first-line drug of choice** for *Bacillus anthracis* infections (treatment and prophylaxis). - Other first-line options include **doxycycline**, and combination therapy is often used for systemic/inhalational anthrax. - Early antibiotic therapy significantly reduces mortality, though delayed treatment in inhalational anthrax carries high mortality risk. *Erythromycin* - Erythromycin is a **macrolide antibiotic** that is **not recommended** for *Bacillus anthracis* infections. - It has lower efficacy and is not considered effective against anthrax, especially in severe systemic forms. *Ceftriaxone* - Ceftriaxone is a **third-generation cephalosporin** that is **not recommended** for anthrax. - *Bacillus anthracis* produces **beta-lactamase enzymes** that confer resistance to many beta-lactam antibiotics. - Therefore, ceftriaxone would be ineffective as monotherapy. *No treatment with approx. 100% mortality* - This is **incorrect** as a treatment option since effective antibiotics are available. - While untreated inhalational anthrax has very high mortality (approaching 90-100%), **treatment exists and is effective**, especially when initiated early. - The drug of choice for anthrax is ciprofloxacin (or doxycycline), not "no treatment."
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