30 Questions
What is the primary mechanism by which bactericidal drugs kill bacteria?
Killing bacteria directly
Which of the following is a key advantage of using a combination of antimicrobial drugs?
Reduces the possibility of superinfections
Which of the following is a type of genetic alteration that can lead to antibiotic resistance in bacteria?
Spontaneous mutations of DNA
What is the primary disadvantage of using a combination of bacteriostatic and bactericidal antimicrobial agents?
Bacteriostatic agents may interfere with the action of a bactericidal drug
Which of the following is a key advantage of using a combination of $eta$-lactams and aminoglycosides as antimicrobial therapy?
Synergistic effect in killing bacteria
Which of the following is a primary mechanism by which bacteria can develop resistance to antimicrobial agents?
Altered protein expression
Which of the following is NOT one of the five basic mechanisms of antibiotic action?
Inhibiting protein folding
Which factor is NOT considered when selecting an antimicrobial agent?
Patient's socioeconomic status
Which of the following statements about the effect of infection site on therapy is FALSE?
Inflammation always facilitates antibiotic penetration to the site of infection.
Which of the following is a host factor that can affect antimicrobial therapy?
Renal dysfunction
Which statement about narrow spectrum antibiotics is TRUE?
Isoniazid is an example acting only on mycobacteria.
Based on the information provided, which antibiotic would be most appropriate for a Streptococcus pyogenes infection?
Amoxicillin
Which of the following is NOT one of the main objectives of the lecture described in the text?
Analyze the potential for hypersensitivity reactions, direct toxic effects, and development of superinfections with the use of β-lactam and other cell wall- and membrane-active antibiotics.
Which of the following is NOT a type of β-lactam antibiotic mentioned in the text?
Peptides
What is the primary mechanism of antibacterial action for β-lactam antibiotics according to the text?
Inhibiting the transpeptidation reaction by targeting penicillin-binding proteins (PBPs)
Which of the following is a characteristic of the killing kinetics of β-lactam antibiotics described in the text?
Time-dependent killing
Which of the following is NOT a type of penicillin antibiotic?
Antipseudomonal penicillins
What is the primary route of administration for penicillin V according to the text?
Oral (p.o.)
Which antibiotic is effective against Neisseria meningitidis, Treponema pallidum, and Leptospira?
Penicillin G
Which antibiotic class is effective against Staphylococcus aureus and Streptococcus species?
Antistaphylococcal penicillins
Which antibiotic combination is effective against Bacteroides fragilis?
Piperacillin/tazobactam
Which adverse effect is associated with penicillin antibiotics?
Pseudomembranous colitis
Which penicillin is effective against Pseudomonas aeruginosa?
Piperacillin/tazobactam
Which condition is not listed as an indication for extended-spectrum penicillins?
Osteomyelitis
Which of the following mechanisms can lead to decreased accumulation of an antibiotic within a bacterial cell?
Presence of a lipopolysaccharide layer
Which of the following is NOT a mechanism by which bacteria can develop resistance to antibiotics?
Increased uptake of the antibiotic
In the context of antimicrobial resistance, what is the significance of alterations in target proteins?
They induce resistance to certain antibiotics by modifying their target sites
Which of the following is an example of enzymatic inactivation of antibiotics, contributing to antimicrobial resistance?
Production of β-lactamases
What is the potential consequence of antimicrobial therapy, even when antibiotics exhibit selective toxicity?
The host may develop adverse effects
Which of the following statements regarding spontaneous mutations in DNA is correct?
Spontaneous mutations may persist, be corrected, or be lethal to the cell
Study Notes
Bactericidal and Bacteriostatic Agents
- Bactericidal agents kill bacteria, decreasing the total number of viable microorganisms.
- Bacteriostatic agents arrest the growth and replication of bacteria, limiting the spread of infection.
Antibiotic Combinations
- Treatment with a single agent reduces the possibility of superinfections and decreases the emergence of multi-drug resistant organisms.
- Advantages of combination therapy include synergism, treatment of mixed infections, and reduction of risk of microorganism developing resistance.
- Disadvantages of combination therapy include interference with the action of a bactericidal drug and potential toxicity.
Antibiotic Resistance
- Bacteria are designated resistant if their growth is not inhibited by the maximum level of antibiotic tolerated by the host.
- Resistance develops due to imprudent and inappropriate use of antibiotics.
- Genetic alterations and altered protein expression are mechanisms involved in the development of resistance.
Genetic Alterations Leading to Resistance
- Spontaneous mutations of DNA may persist, be corrected, or be lethal.
- DNA transfer of drug resistance involves plasmids that are passed between cells.
Altered Protein Expression in Drug-Resistant Organisms
- Modification of antibiotic target sites alters target proteins, inducing resistance to certain antibiotics.
- Decreased accumulation of antibiotic occurs due to decreased penetration or presence of a lipopolysaccharide layer.
- Enzymatic inactivation of antibiotic involves the ability to destroy or inactivate antibiotic, leading to development of resistance.
Complications of Antimicrobial Therapy
- Antibiotics exhibit selective toxicity, but the host may develop adverse effects.
- Bacterial cell wall-synthesizing enzymes, bacterial ribosome, DNA replication enzymes, and nucleotide synthesis are affected by antibiotics.
Selection of Antimicrobial Agents
- Factors affecting selection include microorganism identification, antimicrobial sensitivity, site of infection, severity of infection, and patient factors.
- The most narrow spectrum agent that is effective reduces the potential development of resistance.
Chemotherapeutic Spectra
- Narrow spectrum agents act on a single or limited group of microorganisms.
- Extended spectrum agents are effective against gram-positive and some gram-negative bacteria.
- Broad spectrum agents affect a wide variety of microbial species.
Bacterial Cell Wall Inhibitors
- b-Lactams target site is PBPs, inhibiting transpeptidation reaction.
- b-Lactam antibiotics include penicillins, cephalosporins, carbapenems, and monobactam.
Penicillins
- Spectrum of activity includes non-penicillinase producing gram-positive bacteria, spirochetes, and meningococci.
- Antistaphylococcal penicillins are effective against staphylococci and streptococci.
- Extended-spectrum penicillins have increased gram-negative activity.
- Antipseudomonal penicillin has the broadest spectrum of penicillins.
Test your knowledge on the bacterial cell wall synthesis, nucleotide synthesis, mechanisms of antibiotic action, and factors influencing the selection of antimicrobial agents.
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