Antimicrobial Resistance Practice Questions

Q: What is the primary mechanism of antibiotic resistance in Neisseria gonorrhoeae?

Altered penicillin-binding proteins (PBPs). ***Altered penicillin-binding proteins (PBPs)*** - Alterations in **penicillin-binding proteins (PBPs)**, particularly the mosaic *penA* gene, represent the **most clinically significant mechanism** of resistance in *N. gonorrhoeae* today. - These chromosomal mutations reduce the affinity of beta-lactam antibiotics (including **cephalosporins**) for their target, preventing inhibition of cell wall synthesis. - This mechanism is responsible for **reduced susceptibility and resistance to extended-spectrum cephalosporins** (ceftriaxone, cefixime), which are currently the recommended first-line treatment. - PBP alterations are now **widespread globally** and represent the primary concern for treatment failure. *Plasmid-mediated beta-lactamase production only* - Beta-lactamase production (PPNG strains) was historically important for **penicillin resistance** in the 1970s-1980s. - While still present, this mechanism is **less relevant clinically** today since penicillin is no longer used for gonorrhea treatment. - The word "only" makes this incorrect, as *N. gonorrhoeae* employs multiple resistance mechanisms simultaneously. *Efflux pump mechanisms only* - The **MtrCDE efflux pump system** contributes to resistance by expelling multiple antibiotic classes from the bacterial cell. - Efflux pumps enhance resistance to **hydrophobic antibiotics** including azithromycin and some beta-lactams. - However, they are typically part of a **multifactorial resistance pattern** rather than the sole mechanism, making "only" incorrect. *Ribosomal protection proteins only* - Ribosomal protection (e.g., *tetM* gene) confers resistance to **tetracyclines**. - This mechanism is important for tetracycline resistance but is **not the primary concern** for current gonorrhea treatment. - The word "only" makes this incorrect, as resistance involves multiple mechanisms.

Q: Vertical transmission of resistance to ciprofloxacin occurs :-

Mutation. ***Mutation*** - Vertical transmission of resistance occurs when a bacterium with a **resistance gene**, such as one conferring resistance to **ciprofloxacin**, replicates and passes that gene to its progeny. - This typically happens through **spontaneous mutations** in the bacterial genome that alter the drug's target or uptake, and these mutations are then inherited by subsequent generations. *Transduction* - **Transduction** involves the transfer of genetic material, including resistance genes, via **bacteriophages** (viruses that infect bacteria). - This is a **horizontal gene transfer** mechanism, not a vertical one. *Conjugation* - **Conjugation** is the direct transfer of genetic material, often in the form of **plasmids**, from one bacterium to another through direct cell-to-cell contact. - This is a form of **horizontal gene transfer**, not vertical transmission. *Transformation* - **Transformation** is the uptake of **free DNA** from the environment by a bacterium, which can then integrate this DNA into its own genome. - This mechanism is also a type of **horizontal gene transfer**, not vertical transmission of resistance to daughter cells during replication.

Q: Organism showing marked resistance to multidrug therapy -

Gonococci. ***Gonococci*** - **Gonococci (Neisseria gonorrhoeae)** increasingly show **resistance to multiple antibiotics**, including penicillin, tetracycline, macrolides, and some cephalosporins, making treatment challenging. - The Centers for Disease Control and Prevention (CDC) recommends **dual therapy with ceftriaxone and azithromycin** to overcome rising resistance. *Haemophilus ducreyi* - **Haemophilus ducreyi**, the causative agent of **chancroid**, is typically susceptible to macrolides and cephalosporins, with **less reported multidrug resistance** compared to gonococci. - Single-dose therapy with **azithromycin or ceftriaxone** is usually effective. *Calymmatobacterium granulomatosis* - Now known as **Klebsiella granulomatis**, this organism causes **donovanosis (granuloma inguinale)**, and it is generally sensitive to **doxycycline**, **azithromycin**, or ciprofloxacin. - While prolonged treatment may be needed, **widespread multidrug resistance** is not characteristic. *Treponema pallidum* - **Treponema pallidum**, which causes **syphilis**, remains exquisitely susceptible to **penicillin**, which is the gold standard treatment. - There is **no significant reported multidrug resistance** to penicillin, although macrolide resistance has emerged in some regions.

Q: Burkholderia cepacia is intrinsically resistant to:

Polymyxin B. ***Polymyxin B*** - *Burkholderia cepacia* demonstrates **classic intrinsic resistance** to **polymyxins (Polymyxin B and Colistin/Polymyxin E)** - **Mechanism**: Modifications in the **lipopolysaccharide (LPS) structure** of the outer membrane, particularly alterations in lipid A, reduce polymyxin binding - This resistance is **chromosomally encoded** and present in all strains, making polymyxins completely ineffective against *B. cepacia* infections - This is the **most characteristic example** of intrinsic resistance in this organism *Ciprofloxacin* - *B. cepacia* is **NOT intrinsically resistant** to ciprofloxacin - Ciprofloxacin may retain activity and is sometimes used in susceptible strains - Resistance can develop through **acquired mechanisms** (efflux pumps, DNA gyrase mutations), but this is not inherent to all strains - Susceptibility testing is essential before use *Ceftriaxone* - *B. cepacia* shows resistance to third-generation cephalosporins like ceftriaxone through **multiple resistance mechanisms** including chromosomal AmpC beta-lactamases and efflux pumps - While this resistance is widespread, it's **less characteristic** as a defining feature compared to polymyxin resistance - The beta-lactam resistance pattern in *B. cepacia* is complex and variable *Ampicillin* - *B. cepacia* is resistant to aminopenicillins like ampicillin through **chromosomal beta-lactamase production** and poor outer membrane permeability - While present in most strains, this resistance mechanism is **common to many Gram-negative bacteria** and not a distinguishing feature - Ampicillin is not considered for *B. cepacia* treatment

Q: The initial origin of new drug resistance genes in bacteria most commonly occurs due to:

Mutation. ***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.

Q: A 2-year-old infant is diagnosed with meningitis. A lumbar puncture reveals numerous neutrophils and gram-positive cocci in pairs that appear encapsulated. She is admitted to the hospital and started on intravenous (IV) beta-lactams. Which of the following targets would most likely play a role in the development of resistance to this antibiotic in the most likely etiologic agent of this child's meningitis?

Penicillin-binding protein. ***Penicillin-binding protein*** - The most likely pathogen causing meningitis in a 2-year-old with gram-positive cocci in pairs and capsules is *Streptococcus pneumoniae*. Resistance in *S. pneumoniae* to beta-lactam antibiotics (like penicillin and cephalosporins) primarily arises from **mutations in its penicillin-binding proteins (PBPs)**, which reduce their affinity for these drugs. - Beta-lactam antibiotics exert their effect by binding to and inactivating bacterial **PBPs**, which are essential for **cell wall synthesis**. *Reverse transcriptase* - **Reverse transcriptase** is an enzyme found in **retroviruses** and is involved in converting RNA into DNA; it is not present in bacteria. - This target is associated with resistance to **antiretrovirals** (e.g., in HIV treatment), not bacterial antibiotics. *Bactoprenol* - **Bactoprenol** is a lipid carrier molecule involved in the transport of peptidoglycan precursors across the bacterial cell membrane for cell wall synthesis. - While crucial for cell wall synthesis, it is not a direct target for beta-lactam antibiotics, nor is it the primary mechanism for beta-lactam resistance in *S. pneumoniae*. *DNA gyrase* - **DNA gyrase** is a bacterial enzyme responsible for relieving supercoiling during DNA replication. - It is the primary target for **fluoroquinolone antibiotics**, and mutations in DNA gyrase can lead to fluoroquinolone resistance, but it is not relevant to beta-lactam resistance.

Q: The most common mechanism of resistance to drugs in Staphylococcus is

Transduction. ***Correct Option: Transduction*** - **Transduction** is the transfer of genetic material via **bacteriophages** and is the **most common mechanism** of horizontal gene transfer in *Staphylococcus aureus*. - Bacteriophages play a crucial role in disseminating **antibiotic resistance genes** in staphylococci, including genes for **methicillin resistance (mecA)**, **toxins**, and **beta-lactamase**. - Phage-mediated transfer is responsible for spreading many **virulence factors** and **resistance determinants** among staphylococcal populations. *Incorrect Option: Episomes* - **Episomes** are plasmids capable of integrating into the bacterial chromosome or existing autonomously. - While episomes can **carry resistance genes**, they are a **genetic element**, not a **mechanism of transfer**. - The question asks about the mechanism, not the vehicle carrying resistance genes. *Incorrect Option: Transformation* - **Transformation** involves uptake of **naked DNA** from the environment. - *Staphylococcus* species are **not naturally competent** for transformation under normal conditions. - This is not a significant mechanism of resistance acquisition in staphylococci. *Incorrect Option: Conjugation* - **Conjugation** requires direct cell-to-cell contact through a **conjugative pilus**. - While possible in *Staphylococcus*, it is **less common** compared to transduction. - Conjugation is more characteristic of **Gram-negative bacteria** and enterococci among Gram-positives.

Q: Which of the following is the most clinically significant function of plasmids in antimicrobial resistance?

Involved in multidrug resistance transfer. ***Involved in multidrug resistance transfer*** - **R-plasmids (resistance plasmids)** carry genes that provide bacteria with resistance to multiple antibiotics simultaneously. - These resistance genes can be transferred horizontally between bacteria through conjugation, transformation, or transduction, contributing to the rapid spread of **multidrug-resistant infections**. - This is the most **clinically significant** function of plasmids in medical microbiology. *Involved in conjugation* - While **F-plasmids (fertility plasmids)** encode the machinery for bacterial conjugation, this is a specific function of fertility plasmids rather than the primary clinical concern. - Conjugation is the mechanism by which plasmids (including R-plasmids) transfer between bacteria, but the question asks about the function most relevant to antimicrobial resistance. *Imparts capsule formation* - **Capsule formation** is typically encoded by genes on the **bacterial chromosome**, not plasmids. - Capsule genes are part of the core bacterial genome and represent a stable chromosomal trait. *Imparts pili formation* - While **sex pili** involved in conjugation can be plasmid-encoded (by F-plasmids), most **common pili** (fimbriae) involved in adhesion are chromosomally encoded. - This is not the primary clinically significant function of plasmids in the context of antimicrobial resistance.

Q: Mycobacterium tuberculosis having resistance to rifampicin, isoniazid, and pyrazinamide is described as -

Multi drug resistant tuberculosis. ***Multi drug resistant tuberculosis*** - This classification specifically refers to *Mycobacterium tuberculosis* resistant to at least **rifampicin** and **isoniazid**, which are the two most potent first-line anti-TB drugs. - While resistance to **pyrazinamide** is also present in this case, the definition of multidrug-resistant tuberculosis (MDR-TB) primarily hinges on resistance to these two core drugs [1]. *Drug resistant tuberculosis* - This is a broad term that can apply to any resistance to one or more anti-TB drugs, but it is not specific enough for resistance to these crucial first-line agents [1]. - It does not convey the clinical and public health implications of resistance to both rifampicin and isoniazid. *Extremely drug resistant tuberculosis* - **Extensively drug-resistant tuberculosis (XDR-TB)** is defined as MDR-TB (resistance to rifampicin and isoniazid) plus resistance to any **fluoroquinolone** and at least one of the three injectable second-line drugs (amikacin, kanamycin, or capreomycin). - The given resistance pattern does not include fluoroquinolones or injectable second-line drugs. *None of the options* - This option is incorrect because the resistance pattern described perfectly fits the definition of multidrug-resistant tuberculosis.

Question 1

A high-risk STI clinic sees increasing antibiotic resistance in N. gonorrhoeae isolates. Which laboratory strategy would best inform local treatment guidelines?

Accepted Answer

Culture with antimicrobial susceptibility testing from all anatomical sites

Answer

Periodic random sampling of cases

Answer

Selective culture of treatment failures

Answer

Universal NAAT testing only

Question 2

What is the primary mechanism of antibiotic resistance in Neisseria gonorrhoeae?

Accepted Answer

Altered penicillin-binding proteins (PBPs)

Answer

Efflux pump mechanisms only

Answer

Ribosomal protection proteins only

Answer

Plasmid-mediated beta-lactamase production only

Question 3

Vertical transmission of resistance to ciprofloxacin occurs :-

Accepted Answer

Mutation

Answer

Transduction

Answer

Conjugation

Answer

Transformation

Question 4

Organism showing marked resistance to multidrug therapy -

Accepted Answer

Gonococci

Answer

Haemophilus ducreyi

Answer

Calymmatobacterium granulomatosis

Answer

Treponema pallidum

Question 5

Burkholderia cepacia is intrinsically resistant to:

Accepted Answer

Polymyxin B

Answer

Ciprofloxacin

Answer

Ceftriaxone

Answer

Ampicillin

Question 6

The initial origin of new drug resistance genes in bacteria most commonly occurs due to:

Accepted Answer

Mutation

Answer

Translation

Answer

Conjugation

Answer

Transduction

Question 7

A 2-year-old infant is diagnosed with meningitis. A lumbar puncture reveals numerous neutrophils and gram-positive cocci in pairs that appear encapsulated. She is admitted to the hospital and started on intravenous (IV) beta-lactams. Which of the following targets would most likely play a role in the development of resistance to this antibiotic in the most likely etiologic agent of this child's meningitis?

Accepted Answer

Penicillin-binding protein

Answer

Reverse transcriptase

Answer

Bactoprenol

Answer

DNA gyrase

Question 8

The most common mechanism of resistance to drugs in Staphylococcus is

Accepted Answer

Transduction

Answer

Transformation

Answer

Episomes

Answer

Conjugation

Question 9

Which of the following is the most clinically significant function of plasmids in antimicrobial resistance?

Accepted Answer

Involved in multidrug resistance transfer

Answer

Involved in conjugation

Answer

Imparts capsule formation

Answer

Imparts pili formation

Question 10

Mycobacterium tuberculosis having resistance to rifampicin, isoniazid, and pyrazinamide is described as -

Accepted Answer

Multi drug resistant tuberculosis

Answer

Drug resistant tuberculosis

Answer

Extremely drug resistant tuberculosis

Answer

None of the options

Antimicrobial Resistance — MCQs

Antimicrobial Resistance — MCQs

On this page

Practice by Chapter

Want unlimited practice?