Bacterial Resistance to β-lactam Antibiotics

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Questions and Answers

What is the primary reason for the higher production of β-lactamases in gram-positive bacteria compared to gram-negative bacteria?

Presence of β-lactamases in the inner membrane

Higher availability of antibiotics in gram-positive bacteria

Greater genetic variability in gram-positive bacteria

Secretion of enzymes in larger quantities (correct)

Where are β-lactamases located in gram-negative bacteria that contribute to their resistance?

Cell wall

Cytoplasmic membrane

Periplasmic space (correct)

Outer membrane vesicles

Which factor contributes to bacterial resistance to β-lactam antibiotics?

The inability of the antibiotic to reach effective concentrations (correct)

Increased permeability of the outer membrane

Inherent susceptibility to other antibiotic classes

Presence of ribosomes in the cell membrane

How is the gene for staphylococcal penicillinase commonly transferred between bacteria?

Via bacteriophage (C) Signup and view all the answers

What type of resistance alteration is more common among gram-positive bacterial pathogens?

Modifications to β-lactam target sites (C) Signup and view all the answers

What is one way that bacteria can acquire resistance to β-lactam antibiotics?

By mutations that decrease the affinity of PBPs for the antibiotic (A) Signup and view all the answers

How do β-lactam antibiotics primarily exert their effect on bacteria?

By inhibiting the last step in peptidoglycan synthesis (C) Signup and view all the answers

What structural feature of the bacterial cell wall varies significantly between gram-positive and gram-negative bacteria?

The thickness of the peptidoglycan layer (B) Signup and view all the answers

What genetic mechanism allows for the transfer of low-affinity PBPs among different bacterial species?

Homologous recombination (D) Signup and view all the answers

What mechanism is attributed to methicillin-resistant Staphylococcus aureus (MRSA) acquiring resistance?

Acquisition of a high-molecular-weight PBP with low affinity for β-lactams (C) Signup and view all the answers

Which component is NOT found in the structure of Gram-negative bacteria?

Glycopeptide polymer (D) Signup and view all the answers

What role does β-Lactamase play in bacterial resistance?

It degrades β-lactam antibiotics. (A) Signup and view all the answers

Which of the following accurately describes the peptidoglycan layer in bacteria?

Is a glycopeptide polymer outside the cell (C) Signup and view all the answers

What is the function of porin channels in Gram-negative bacteria?

To facilitate nutrient transport (B) Signup and view all the answers

Which of the following structures is specific to Gram-positive bacteria?

Thick peptidoglycan layer (C) Signup and view all the answers

What is the primary purpose of the plasma membrane in bacteria?

To regulate transport of substances (D) Signup and view all the answers

What is a unique feature of the cell wall in Gram-negative bacteria compared to Gram-positive bacteria?

Additional outer membrane layer (C) Signup and view all the answers

Which amino acid is NOT part of the peptidoglycan layer's structure?

Serine (D) Signup and view all the answers

Which of the following β-lactamase inhibitors is coformulated with ceftazidime?

Avibactam (A) Signup and view all the answers

What type of β-lactamases do avibactam and relebactam inhibit?

Both B and C (B) Signup and view all the answers

What structural component is the chief requirement for the biological activity of penicillins?

β-lactam ring (B) Signup and view all the answers

Which β-lactamase inhibitor is coformulated with meropenem?

Vaborbactam (B) Signup and view all the answers

What is the role of multi-drug efflux pumps in gram-negative bacteria?

Removing antibiotic compounds (C) Signup and view all the answers

Which of the following statements about β-lactamase inhibitors is FALSE?

They are effective against metallo-β-lactamases. (D) Signup and view all the answers

What drives the energy for the operation of antibiotic efflux pumps in gram-negative bacteria?

Proton motive force (B) Signup and view all the answers

Study Notes

Cell Envelope Disruptors: β-Lactam, Glycopeptide, and Lipopeptide Antibacterials

β-Lactams: A major class of antibiotics, including penicillins, cephalosporins, carbapenems, and monobactams. They share a common structure (β-lactam ring) and mechanism: inhibiting bacterial peptidoglycan cell wall synthesis.
Mechanism of Action: β-lactams inhibit the final step in peptidoglycan synthesis, acylating the transpeptidase (penicillin-binding proteins, PBPs) by cleaving the -CO-N- bond in the β-lactam ring.
Bacterial Resistance Mechanisms: Bacteria can develop resistance to β-lactams via mutations affecting PBP affinity for the antibiotic, decreased antibiotic concentration at the target site, or enzymatic degradation by β-lactamases.
β-lactamase Inhibitors: Molecules that bind to β-lactamases to prevent them from inactivating β-lactam antibiotics. Examples include clavulanate, sulbactam, tazobactam, avibactam, vaborbactam, and relebactam.
Penicillins: A subset of β-lactams with a varied spectrum, classified by their resistance to penicillinases (e.g., penicillin G, penicillinase-resistant penicillins, aminopenicillins, and antipseudomonal penicillins).
Cephalosporins: Another β-lactam class, generally more resistant to β-lactamases than penicillins, categorized into generations of increasing gram-negative activity.
Other β-lactam antibiotics: Carbapenems (broad spectrum, resistant to many β-lactamases), imipenem + cilastatin).
Glycopeptides: A class of antibiotics (e.g., vancomycin, teicoplanin, lipoglycopeptides) that target bacterial cell wall synthesis.
Mechanism of glycopeptide action: They target the D-alanyl-D-alanine terminus of peptidoglycans hindering both transpeptidase and transglycosidase function.
Lipopeptides: A class of antibiotics (e.g., daptomycin) that disrupt bacterial cell membranes, causing depolarization, and leading to cell death.
Mechanism of lipopeptide action: Daptomycin targets the bacterial inner membrane, leading to depolarization and cell death.
Bacitracin: A polypeptide antibiotic effective against many Gram-positive bacteria, used topically.

β-Lactamase Inhibitors

Clavulanic Acid: A mechanism-based inhibitor of many β-lactamases, coformulated with amoxicillin.
Sulbactam: A β-lactamase inhibitor coformulated with ampicillin.
Tazobactam: A β-lactamase inhibitor coformulated with piperacillin.
Avibactam, vaborbactam, relebactam: Newer β-lactamase inhibitors with wider spectra.

Penicillins

Penicillin G, Penicillin V: Natural penicillins effective against some Gram-positive bacteria, but easily hydrolyzed by penicillinase.
Penicillinase-Resistant Penicillins: More stable to penicillinases.

Cephalosporins

Generations: Categorized based on antibacterial activity against Gram-positive/negative bacteria. Later generations offer greater activity against gram-negative organisms.
First Generation: Cefazolin, cephalexin.
Second Generation: Cefuroxime, cefoxitin, cefotetan.
Third Generation: Cefotaxime, ceftriaxone, cefdinir, cefpodoxime.
Fourth Generation: Cefepime
Fifth Generation: Ceftaroline
Antipseudomonal: Ceftazidime, ceftolozane/tazobactam, cefepime.

Other Cell Envelope Disruptors

Glycopeptides: Vancomycin, teicoplanin, lipoglycopeptides
Lipopeptides: Daptomycin
Bacitracins: Often used topically; less common in systemic use.

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Description

This quiz explores critical concepts related to bacterial resistance mechanisms, specifically focusing on β-lactam antibiotics. It covers the production of β-lactamases, gene transfer among bacteria, and structural differences in cell walls between gram-positive and gram-negative bacteria. Advance your understanding of these essential topics in microbiology.