Drug Penetration and Efflux in Gram-Negative Organisms

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What is the major difference between cephalosporins and penicillins in terms of susceptibility?

Penicillins are generally more resistant to beta-lactamase destruction.

Cephalosporins are generally more resistant to beta-lactamase destruction. (correct)

Penicillins are generally more susceptible to beta-lactamase destruction.

Cephalosporins are generally more susceptible to beta-lactamase destruction.

How do beta-lactam antimicrobials impair the development of bacterial cell walls?

By inhibiting the autolysins responsible for cleaving cell wall lattices.

By interfering with transpeptidase enzymes responsible for the formation of cross-links between peptidoglycan strands. (correct)

By mimicking the structure of peptidoglycan strands in the bacterial cell wall.

By enhancing the synthesis of new strands of bacterial cell walls.

What are the penicillin-binding proteins (PBPs) associated with in bacteria?

Development of bacterial cell wall lattices.

Formation of cross-links between peptidoglycan strands. (correct)

Synthesis of new strands of bacterial cell walls.

Formation of bacterial cell wall autolysins.

What balances bacterial growth by continually cleaving cell wall lattices during cell wall synthesis?

Autolysins Signup and view all the answers

How do gram-negative beta-lactamases primarily act?

By hydrolysis of the amide bond in the 4-member beta-lactam ring Signup and view all the answers

Which bacterial species is NOT mentioned as capable of resistance due to beta-lactamase production?

Mycobacterium Signup and view all the answers

What is the impact of beta-lactamase protectors such as clavulanic acid on the treatment of gram-negative organisms?

It may not be as positive for treatment compared to gram-positive organisms Signup and view all the answers

What leads to a sizable increase in resistance to beta-lactam antimicrobials?

Decrease in affinity of crucial PBP due to acquired gene mutations Signup and view all the answers

In which environment can L-forms, a phenotypic form of resistance, survive?

A hyperosmotic environment like the renal medulla Signup and view all the answers

What results in resistance to all beta-lactam drugs, including carbapenems and most generations of cephalosporins in Staphylococcus spp?

Acquisition of the mec gene resulting in a mutation in PBP-2 Signup and view all the answers

What is the most important mechanism of bacterial resistance to beta-lactam antimicrobials?

Enzymatic inactivation by beta-lactamases Signup and view all the answers

What do porins in gram-negative organisms do in relation to drugs?

Effectively remove drugs after penetration of the lipopolysaccharide covering Signup and view all the answers

What do second- and third-generation cephalosporins reflect in their modifications?

Larger R groups minimizing beta-lactamase access Signup and view all the answers

Which antimicrobials are not subject to extended-spectrum beta-lactamases (ESBLs)?

Carbapenems Signup and view all the answers

What do newer beta-lactamases emerging reflect, in part?

Continued manipulation of the drugs in an attempt to circumvent bacterial beta-lactamase production Signup and view all the answers

What renders cephalosporins resistant to penicillinases?

Addition of larger R groups on the beta-lactam structure Signup and view all the answers

What do inhibitors of beta-lactamases such as clavulanic acid and sulbactam aim to do?

Minimize penicillin destruction Signup and view all the answers

What are some gram-positive beta-lactamases unable to initiate?

Self-transmission Signup and view all the answers

In which bacterial species are gram-positive beta-lactamases generally excreted into the external environment as exoenzymes?

Staphylococcus aureus Signup and view all the answers

What is the main resistance mechanism for Staphylococcal strains?

Altered PBP targets Signup and view all the answers

What is a common difference between gram-negative and gram-positive bacteria in terms of beta-lactamase production?

Plasmid-mediated production Signup and view all the answers

What is one of the characteristics of gram-positive beta-lactamases related to their self-transmission?

Inducible production Signup and view all the answers

At subinhibitory concentrations, what effects do beta-lactam antimicrobials have on bacterial structure and function?

They promote host-mediated cell death Signup and view all the answers

In the context of beta-lactam antimicrobials, what is the significance of the log phase of bacterial growth?

Susceptible organisms must be actively multiplying or growing Signup and view all the answers

What is a contributing factor to the development of resistance to beta-lactam antimicrobials?

Increased expression of efflux pumps Signup and view all the answers

Which type of organisms are susceptible to the action of beta-lactam antimicrobials?

Organisms that have cell walls Signup and view all the answers

In the context of gram-negative bacteria, what hinders access to the cytoplasmic membrane?

Capsular materials Signup and view all the answers

Which bacteria present a greater obstacle to beta-lactam antimicrobials due to their outer membranes?

Escherichia coli Signup and view all the answers

What is a characteristic feature of beta-lactam antimicrobials' activity in a slightly acidic environment?

Increased membrane penetration Signup and view all the answers

What is the primary factor related to the efficacy of beta-lactam antimicrobials?

Time that plasma or tissue drug concentrations exceed the MIC Signup and view all the answers

What is a common mechanism of antimicrobial resistance to beta-lactam antimicrobials in bacteria?

Downregulation of porins Signup and view all the answers

What is a characteristic feature of carbapenems in relation to time-dependent antimicrobials?

Concentrations should remain above the MIC for approximately 25% of the dosing interval Signup and view all the answers

What type of bacteria have a restricting sieving mechanism (porins) in their outer membranes?

Gram-negative bacteria Signup and view all the answers