Welcome, PharmD students, to this MCQ quiz on the Principles of Important Gram-Negative Bacteria and Antimicrobials! Gram-negative bacteria are a significant cause of diverse infections, often presenting unique challenges due to their cell wall structure and propensity for developing antimicrobial resistance. This quiz will test your understanding of key Gram-negative pathogens, their characteristics, common infections they cause, and the principles of antimicrobial agents used to combat them, including their spectrum of activity and resistance mechanisms. Let’s delve into this critical area of infectious diseases!
1. A key structural feature of Gram-negative bacteria that differentiates them from Gram-positive bacteria is the presence of:
- a) A thick peptidoglycan layer.
- b) An outer membrane containing lipopolysaccharide (LPS).
- c) Teichoic acids in their cell wall.
- d) The ability to form endospores.
Answer: b) An outer membrane containing lipopolysaccharide (LPS).
2. Lipopolysaccharide (LPS) in the outer membrane of Gram-negative bacteria is also known as:
- a) Exotoxin
- b) Endotoxin, which can trigger a strong inflammatory response.
- c) Murein
- d) Peptidoglycan
Answer: b) Endotoxin, which can trigger a strong inflammatory response.
3. Which of the following bacterial groups belongs to the Enterobacterales order (formerly Enterobacteriaceae)?
- a) Pseudomonas aeruginosa
- b) Staphylococcus aureus
- c) Escherichia coli and Klebsiella pneumoniae
- d) Streptococcus pneumoniae
Answer: c) Escherichia coli and Klebsiella pneumoniae
4. Escherichia coli is a common cause of which type of infection?
- a) Strep throat
- b) Urinary tract infections (UTIs)
- c) Fungal skin infections
- d) Malaria
Answer: b) Urinary tract infections (UTIs)
5. Pseudomonas aeruginosa is a non-fermenting Gram-negative bacillus known for its:
- a) Universal susceptibility to all antibiotics.
- b) Intrinsic resistance to many antibiotics and ability to cause opportunistic infections, especially in immunocompromised patients or those with cystic fibrosis.
- c) Strict anaerobic growth requirements.
- d) Production of a potent neurotoxin.
Answer: b) Intrinsic resistance to many antibiotics and ability to cause opportunistic infections, especially in immunocompromised patients or those with cystic fibrosis.
6. Extended-spectrum beta-lactamases (ESBLs) produced by some Gram-negative bacteria confer resistance primarily to:
- a) Vancomycin and daptomycin.
- b) Many penicillins and cephalosporins (including 3rd generation).
- c) Aminoglycosides.
- d) Fluoroquinolones.
Answer: b) Many penicillins and cephalosporins (including 3rd generation).
7. Aztreonam, a monobactam antibiotic, has a spectrum of activity primarily limited to:
- a) Gram-positive cocci only.
- b) Anaerobic bacteria only.
- c) Aerobic Gram-negative bacteria (including Pseudomonas aeruginosa for some strains).
- d) Fungi.
Answer: c) Aerobic Gram-negative bacteria (including Pseudomonas aeruginosa for some strains).
8. Carbapenems (e.g., imipenem, meropenem) are broad-spectrum beta-lactam antibiotics that are generally effective against many Gram-negative bacteria, including ESBL producers, but resistance can occur via:
- a) Increased penicillin-binding protein affinity.
- b) Production of carbapenemases (e.g., KPC, NDM, OXA-48-like).
- c) Decreased porin expression only.
- d) Enhanced efflux pump activity only.
Answer: b) Production of carbapenemases (e.g., KPC, NDM, OXA-48-like).
9. Aminoglycosides (e.g., gentamicin, tobramycin) exert their bactericidal effect by inhibiting:
- a) Cell wall synthesis.
- b) Bacterial protein synthesis (binding to the 30S ribosomal subunit).
- c) DNA gyrase.
- d) Folic acid synthesis.
Answer: b) Bacterial protein synthesis (binding to the 30S ribosomal subunit).
10. Fluoroquinolones (e.g., ciprofloxacin, levofloxacin) are broad-spectrum antibiotics that target:
- a) Bacterial cell wall.
- b) Bacterial protein synthesis.
- c) Bacterial DNA gyrase and topoisomerase IV.
- d) Fungal ergosterol synthesis.
Answer: c) Bacterial DNA gyrase and topoisomerase IV.
11. Which characteristic is common among non-fermenting Gram-negative bacilli like Pseudomonas aeruginosa and Acinetobacter baumannii?
- a) They are typically highly susceptible to first-generation cephalosporins.
- b) They are often found as commensals in the human gut.
- c) They are frequently multi-drug resistant and associated with healthcare-associated infections.
- d) They primarily cause infections in healthy outpatients.
Answer: c) They are frequently multi-drug resistant and associated with healthcare-associated infections.
12. Trimethoprim/sulfamethoxazole (TMP/SMX) inhibits sequential steps in the synthesis of:
- a) Peptidoglycan
- b) Bacterial proteins
- c) Folic acid
- d) Bacterial DNA
Answer: c) Folic acid
13. Extended-spectrum penicillins like piperacillin are often combined with a beta-lactamase inhibitor (e.g., tazobactam) to:
- a) Decrease their oral bioavailability.
- b) Protect the penicillin from degradation by many bacterial beta-lactamases, thereby broadening its spectrum.
- c) Increase their protein binding.
- d) Specifically target Gram-positive organisms.
Answer: b) Protect the penicillin from degradation by many bacterial beta-lactamases, thereby broadening its spectrum.
14. Klebsiella pneumoniae is a Gram-negative bacterium that is a common cause of pneumonia and UTIs, and is notorious for producing which type of resistance enzyme?
- a) Vancomycin-resistance enzymes (VanA)
- b) Carbapenemases (e.g., KPC – Klebsiella pneumoniae carbapenemase)
- c) Daptomycin-inactivating enzymes
- d) Linezolid-modifying enzymes
Answer: b) Carbapenemases (e.g., KPC – Klebsiella pneumoniae carbapenemase)
15. Which of these cephalosporin generations generally has the best activity against Pseudomonas aeruginosa?
- a) First-generation (e.g., cefazolin)
- b) Second-generation (e.g., cefuroxime)
- c) Third-generation with anti-pseudomonal activity (e.g., ceftazidime) and Fourth-generation (e.g., cefepime)
- d) All cephalosporins have equal anti-pseudomonal activity.
Answer: c) Third-generation with anti-pseudomonal activity (e.g., ceftazidime) and Fourth-generation (e.g., cefepime)
16. Fosfomycin is an antibiotic often used as a single oral dose for uncomplicated UTIs caused by Gram-negative bacteria like E. coli. Its mechanism involves inhibiting:
- a) Protein synthesis.
- b) DNA gyrase.
- c) An early step in bacterial cell wall synthesis (enolpyruvyl transferase).
- d) Folic acid metabolism.
Answer: c) An early step in bacterial cell wall synthesis (enolpyruvyl transferase).
17. Stenotrophomonas maltophilia is an intrinsically resistant Gram-negative bacillus often treated with:
- a) Penicillin G
- b) Vancomycin
- c) Trimethoprim/sulfamethoxazole
- d) Clindamycin
Answer: c) Trimethoprim/sulfamethoxazole
18. Common virulence factors of Gram-negative bacteria include pili (fimbriae), which primarily function in:
- a) Motility
- b) Toxin production
- c) Adherence to host cells
- d) Spore formation
Answer: c) Adherence to host cells
19. The “space” between the inner and outer membranes of Gram-negative bacteria, containing peptidoglycan and various enzymes, is called the:
- a) Cytoplasm
- b) Nucleoid
- c) Periplasmic space
- d) Capsule
Answer: c) Periplasmic space
20. Which class of antibiotics is known for potential nephrotoxicity and ototoxicity, requiring therapeutic drug monitoring, and covers many Gram-negative aerobes?
- a) Macrolides
- b) Tetracyclines
- c) Aminoglycosides
- d) Lincosamides
Answer: c) Aminoglycosides
21. Nitrofurantoin is an antibiotic used for uncomplicated UTIs. Its activity is concentrated in the urine, and it is generally NOT effective for:
- a) E. coli UTIs
- b) Systemic infections or pyelonephritis
- c) Enterococcus faecalis UTIs
- d) Prophylaxis of recurrent UTIs
Answer: b) Systemic infections or pyelonephritis
22. Acinetobacter baumannii is a significant concern in healthcare settings primarily due to its:
- a) High susceptibility to common antibiotics.
- b) Ability to cause severe community-acquired pneumonia in healthy individuals.
- c) Propensity for extensive drug resistance and survival in hospital environments.
- d) Fastidious growth requirements.
Answer: c) Propensity for extensive drug resistance and survival in hospital environments.
23. The interaction of bacteria with the host immune system is complex. Gram-negative bacterial LPS can trigger the release of which pro-inflammatory cytokines?
- a) Interleukin-10 (IL-10)
- b) Transforming growth factor-beta (TGF-β)
- c) Tumor necrosis factor-alpha (TNF-α), Interleukin-1 (IL-1), and Interleukin-6 (IL-6)
- d) Erythropoietin
Answer: c) Tumor necrosis factor-alpha (TNF-α), Interleukin-1 (IL-1), and Interleukin-6 (IL-6)
24. Besides E. coli, other important members of the Enterobacterales that commonly cause infections include:
- a) Streptococcus pyogenes and Staphylococcus epidermidis
- b) Klebsiella spp., Enterobacter spp., Proteus spp., and Serratia spp.
- c) Clostridium difficile and Bacillus anthracis
- d) Candida albicans and Aspergillus fumigatus
Answer: b) Klebsiella spp., Enterobacter spp., Proteus spp., and Serratia spp.
25. Resistance to fluoroquinolones in Gram-negative bacteria can arise from mutations in genes encoding:
- a) Penicillin-binding proteins.
- b) DNA gyrase (gyrA, gyrB) and topoisomerase IV (parC, parE).
- c) 30S ribosomal subunit.
- d) Dihydropteroate synthase.
Answer: b) DNA gyrase (gyrA, gyrB) and topoisomerase IV (parC, parE).
26. Haemophilus influenzae type b (Hib) infections have dramatically decreased due to:
- a) Improved sanitation.
- b) Widespread use of Hib conjugate vaccines.
- c) Newer beta-lactam antibiotics.
- d) Its natural eradication.
Answer: b) Widespread use of Hib conjugate vaccines.
27. Neisseria gonorrhoeae is the causative agent of gonorrhea. A major concern with this Gram-negative diplococcus is:
- a) Its slow growth in culture.
- b) Its intrinsic resistance to all beta-lactams.
- c) Increasing antimicrobial resistance, including to cephalosporins and fluoroquinolones.
- d) Its ability to form spores.
Answer: c) Increasing antimicrobial resistance, including to cephalosporins and fluoroquinolones.
28. Which of the following is a key principle when selecting an antimicrobial for a Gram-negative infection?
- a) Always choose the antibiotic with the narrowest spectrum, regardless of suspected pathogen.
- b) Consider the likely pathogen(s), site of infection, local susceptibility patterns (antibiogram), and patient factors.
- c) Empiric therapy should always include vancomycin.
- d) Use the same antibiotic for all Gram-negative infections.
Answer: b) Consider the likely pathogen(s), site of infection, local susceptibility patterns (antibiogram), and patient factors.
29. The outer membrane of Gram-negative bacteria acts as a barrier, restricting the entry of certain antibiotics, particularly:
- a) Small, water-soluble molecules.
- b) Large or hydrophobic antibiotics (unless they use porins or other uptake mechanisms).
- c) All beta-lactam antibiotics.
- d) Fluoroquinolones.
Answer: b) Large or hydrophobic antibiotics (unless they use porins or other uptake mechanisms).
30. Porin channels in the outer membrane of Gram-negative bacteria are important for:
- a) Efflux of antibiotics out of the cell.
- b) Allowing passage of small hydrophilic molecules, including some antibiotics, into the periplasmic space.
- c) Anchoring the LPS.
- d) Bacterial motility.
Answer: b) Allowing passage of small hydrophilic molecules, including some antibiotics, into the periplasmic space.
31. Which of the following is a common characteristic used to differentiate among Enterobacterales species in the lab?
- a) Gram stain reaction (they are all Gram-negative).
- b) Ability to ferment lactose and other biochemical tests.
- c) Presence of an outer membrane.
- d) Sensitivity to penicillin G.
Answer: b) Ability to ferment lactose and other biochemical tests.
32. Beta-lactamase inhibitors like clavulanate, sulbactam, and tazobactam work by:
- a) Directly killing bacteria.
- b) Binding to and inactivating bacterial beta-lactamase enzymes, thereby protecting the partner beta-lactam antibiotic.
- c) Inhibiting bacterial protein synthesis.
- d) Damaging the bacterial outer membrane.
Answer: b) Binding to and inactivating bacterial beta-lactamase enzymes, thereby protecting the partner beta-lactam antibiotic.
33. Carbapenem-Resistant Enterobacterales (CRE) are a serious public health threat because:
- a) They are easily treated with oral penicillins.
- b) They are resistant to nearly all commonly used antibiotics, leaving very limited treatment options.
- c) They only cause mild infections.
- d) They are only found in animals.
Answer: b) They are resistant to nearly all commonly used antibiotics, leaving very limited treatment options.
34. Ceftriaxone, a third-generation cephalosporin, has good activity against many Enterobacterales but generally lacks reliable activity against:
- a) Escherichia coli
- b) Klebsiella pneumoniae (non-ESBL)
- c) Pseudomonas aeruginosa
- d) Proteus mirabilis
Answer: c) Pseudomonas aeruginosa
35. Aminoglycosides require _______ for uptake into bacterial cells, making them ineffective against strict anaerobes.
- a) An acidic environment
- b) Oxygen-dependent active transport
- c) High lipid content in the membrane
- d) The presence of beta-lactamases
Answer: b) Oxygen-dependent active transport
36. Helicobacter pylori, a Gram-negative bacterium, is a primary cause of:
- a) Urinary tract infections
- b) Peptic ulcer disease and gastric cancer
- c) Bacterial meningitis
- d) Skin and soft tissue infections
Answer: b) Peptic ulcer disease and gastric cancer
37. An important consideration when using fluoroquinolones is their potential for:
- a) Causing severe nephrotoxicity similar to aminoglycosides.
- b) Interactions with divalent and trivalent cations (e.g., calcium, iron, antacids), reducing absorption.
- c) Inducing beta-lactamase production.
- d) Covering MRSA effectively.
Answer: b) Interactions with divalent and trivalent cations (e.g., calcium, iron, antacids), reducing absorption.
38. Burkholderia cepacia complex is a group of Gram-negative bacteria particularly problematic for patients with:
- a) Diabetes
- b) Cystic fibrosis
- c) Hypertension
- d) Osteoarthritis
Answer: b) Cystic fibrosis
39. The principle of “collateral damage” in antibiotic therapy refers to the unintended ecological effects, such as:
- a) Selection for resistant organisms and disruption of normal host microbiota.
- b) Improvement in the patient’s overall mood.
- c) Reduction in the cost of subsequent therapies.
- d) Enhanced efficacy of other concurrently administered drugs.
Answer: a) Selection for resistant organisms and disruption of normal host microbiota.
40. Which Gram-negative organism is characteristically associated with a “grape-like” or “tortilla chip” odor in culture and often produces a blue-green pigment (pyocyanin)?
- a) Escherichia coli
- b) Klebsiella pneumoniae
- c) Pseudomonas aeruginosa
- d) Serratia marcescens (often produces a red pigment)
Answer: c) Pseudomonas aeruginosa
41. The presence of an efflux pump in a Gram-negative bacterium can contribute to resistance against:
- a) Only one specific class of antibiotics.
- b) Multiple classes of antibiotics if the pump has broad substrate specificity.
- c) Only Gram-positive targeting antibiotics.
- d) Beta-lactamases.
Answer: b) Multiple classes of antibiotics if the pump has broad substrate specificity.
42. For serious infections caused by Pseudomonas aeruginosa, combination therapy (e.g., an anti-pseudomonal beta-lactam plus an aminoglycoside or fluoroquinolone) is often considered to:
- a) Reduce cost.
- b) Provide synergistic activity and potentially prevent the emergence of resistance.
- c) Narrow the spectrum of activity.
- d) Decrease the risk of nephrotoxicity.
Answer: b) Provide synergistic activity and potentially prevent the emergence of resistance.
43. Which factor is NOT a primary mechanism contributing to the intrinsic resistance of Pseudomonas aeruginosa to many antibiotics?
- a) Low outer membrane permeability (restrictive porins).
- b) Production of potent exotoxins.
- c) Expression of various efflux pump systems.
- d) Production of an inducible chromosomal beta-lactamase (AmpC).
Answer: b) Production of potent exotoxins. (While it produces exotoxins which are virulence factors, they are not a primary mechanism of intrinsic antibiotic resistance).
44. What is a key educational point for patients prescribed trimethoprim/sulfamethoxazole?
- a) Take with dairy products to enhance absorption.
- b) Discontinue immediately if any mild rash occurs without consulting a doctor.
- c) Maintain adequate fluid intake to prevent crystalluria.
- d) Expect urine to turn bright orange.
Answer: c) Maintain adequate fluid intake to prevent crystalluria.
45. The interaction between bacteria and the host immune system often begins with recognition of PAMPs (Pathogen-Associated Molecular Patterns) like LPS by:
- a) Bacterial ribosomes.
- b) Host Toll-Like Receptors (TLRs) and other pattern recognition receptors.
- c) Antibiotics.
- d) Bacterial DNA gyrase.
Answer: b) Host Toll-Like Receptors (TLRs) and other pattern recognition receptors.
46. Which generation of cephalosporins has the broadest Gram-negative activity, including Pseudomonas aeruginosa, while also retaining some Gram-positive activity?
- a) First-generation (e.g., cefazolin)
- b) Second-generation (e.g., cefoxitin)
- c) Third-generation (e.g., ceftriaxone – good G neg, but not typically P. aeruginosa; ceftazidime – good P. aeruginosa)
- d) Fourth-generation (e.g., cefepime)
Answer: d) Fourth-generation (e.g., cefepime)
47. A principle of empiric therapy for suspected Gram-negative sepsis in a critically ill patient often involves:
- a) Starting with a single, narrow-spectrum oral antibiotic.
- b) Initiating broad-spectrum intravenous antibiotics that cover likely pathogens, including resistant strains, as soon as possible.
- c) Waiting for culture results before starting any treatment.
- d) Using only bacteriostatic agents.
Answer: b) Initiating broad-spectrum intravenous antibiotics that cover likely pathogens, including resistant strains, as soon as possible.
48. The term “Enterobacterales” is preferred over “Enterobacteriaceae” now because:
- a) It reflects a change in their Gram stain reaction.
- b) It is based on updated taxonomic classification using genomic data.
- c) They no longer ferment glucose.
- d) They are now all obligate anaerobes.
Answer: b) It is based on updated taxonomic classification using genomic data.
49. A common feature of infections caused by non-fermenting Gram-negative bacilli is that they often occur in:
- a) Healthy children in the community.
- b) Hospitalized, immunocompromised, or critically ill patients, or those with indwelling devices.
- c) Patients with no prior antibiotic exposure.
- d) Only tropical climates.
Answer: b) Hospitalized, immunocompromised, or critically ill patients, or those with indwelling devices.
50. Pharmacists play a crucial role in managing infections caused by Gram-negative bacteria by:
- a) Only dispensing prescribed antibiotics.
- b) Ensuring appropriate drug selection based on susceptibility, optimizing dosing regimens, monitoring for efficacy and toxicity, and promoting antimicrobial stewardship.
- c) Performing Gram stains in the pharmacy.
- d) Discouraging all antibiotic use.
Answer: b) Ensuring appropriate drug selection based on susceptibility, optimizing dosing regimens, monitoring for efficacy and toxicity, and promoting antimicrobial stewardship.