Antibiotics

Question 1

Mechanisms of action

Answer 1

• inhibition of bacterial cell wall
• inhibition of nucleic acid synthesis
• inhibition of protein synthesis
• inhibition of cell membrane
• inhibition of folic acid synthesis

Question 2

Inhibition of Cell Wall Synthesis

Answer 2

• Bacteriostatic
• Penicillin and Cephalosporins- block cross-linking between peptidoglycans
• Vancomycin- Blocks peptidoglycan elongation
• Cycloserine- Prevents the cell from making NAG and NAM

Question 3

Penicillin

Answer 3

• Penicillium Chrysogenum
• A diverse group: 1st, 2nd, and 3rd generations
• Natural: Penicillin G and V
• Semisynthetic: Ampicillin and Carbenicillin
• Structure: - Thiazolidine ring - Beta-Lactam Ring- Variable side chain (R group)

Question 4

Cephalosporin

Answer 4

• Cephalosporin Acremonium (mold)
• Widely Administered today
• Diverse Group: (natural and semisynthetic): 1st, 2nd, 3rd, and 4th generations
• Structure: similar to Penicillin except it has a different main group and it has 2 sites for R groups

Question 5

The structure of cephalosporin:

Answer 5

The different R groups allow for versatility and improved effectiveness

Question 6

Inhibition of Protein Synthesis

Answer 6

Chloramphenicol-

Aminoglycosides-

Tetracycline-

Erythromycin-

Question 7

Chloramphenicol:

Answer 7

• binds to 50s ribosomal subunits
• prevents peptide bond formation
• inhibits protein synthesis
• broad-spectrum
• treats typhoid fever and brain abscesses
• rarely used now due to side effects: aplastic anemia

Question 8

Aminoglycosides:

Answer 8

• binds to 30s ribosomal subunits
• causes misreading of mRNA
• inhibits protein synthesis
• from Streptomyces ssp.
• Streptomyces synthesizes many different types of antibiotics, such as; erythromycin, chloramphenicol, and tetracycline.

Question 9

Tetracycline:

Answer 9

• blocks attachment of tRNA
• inhibits protein synthesis
• broad-spectrum and low cost
• commonly used to treat STD’s
• minor side effects: gastrointestinal disruption

Question 10

Erythromycin:

Answer 10

• inhibits protein synthesis
• broad-spectrum
• commonly used as prophylactic drug prior to surgery
• side effects: low toxicity

Question 11

Injury to the plasma membrane:

Answer 11

• polymyxin B (gram negative)
• topical (triple antibiotic ointment)
• combined with bacitracin and neomycin (broad spectrum) in OTC preparation
• neosporin

Question 12

Inhibitors of Nucleic Acid Synthesis

Answer 12

Rifamycin:

• inhibits RNA synthesis
• Antituberculosis

Quinolones and fluoroquinolones:

• UTI’s
• inhibits DNA gyrase (enzyme that helps wind up DNA once it’s been replicated)
• Ciprofloxacin

Question 13

Folic Acid Synthesis

Answer 13

Sulfonamides (sulfa drug) and trimethoprim

• competitive inhibition of enzymes
• analogs
• prevents the metabolism of DNA, RNA, and amino acids
• -this works because mammals get folic acid from their diet and bacteria mush make their own

Question 14

Antivirals

Answer 14

• increasing types of drugs becoming available, however; it is difficult to maintain selective toxicity
• effective drugs- target replication cycle: entry, nucleic acid synthesis, and assembly/release.
• INTERFERON= genetically engineered antiviral protein from a human gene

Question 15

Antiviral medications and what they treat:

Answer 15

• blocking viral entry: tamiflu- blocks the action of neuraminidases of influenza virus
• blocking viral replication: Zidovudine (AZT)- blocks reverse transcription of HIV
• inhibiting viral cleavage: Protease inhibitors- block HIV protease

Question 16

Other types of antimicrobials:

Answer 16

Antifungal- ketoconizole treats valley fever

Antiprotozoal- metronidazole treats giardia

Antimalarial- quinine treats malaria

Anthelmintic- mebendazole treats tapeworms and roundworms

Question 17

Mechanisms of Antibiotic Resistance

Answer 17

• Rapid ejection of the drug
• Alteration of drug’s target site
• Prevention of penetration of drug
• Enzymatic destruction of drug

Question 18

Antimicrobial Resistance means:

Answer 18

a relative or complete lack of effect of antimicrobial against a previously susceptible microbe

Question 19

Antibiotic Resistance means:

Answer 19

Intermicrobial transfer of plasmids containing resistance genes (R factors) occurs by conjugation, transformation, and transduction

Question 20

What factors promote antimicrobial resistance?

Answer 20

• Exposure to sub-optimal levels of antimicrobial
• inappropriate use
• exposure to microbes carrying resistance genes

Question 21

Inappropriate Antimicrobial Use:

Answer 21

• prescriptions not being taken correctly
• antibiotics for viral infections
• antibiotics sold OTC without medical supervision
• spread of resistant microbes (C. difficile) in hosptials
• inadequate surveillance or defective susceptibility assays (giving drugs that are not effective)
• poverty or war (penicillin)
• use of antibiotics in food

Question 22

Antibiotics in Food

Answer 22

Antibiotics are used in animal feeds and sprayed on plants to prevent infection and to promote growth.
- tetracycline in the soil

Multi drug-resistant Salmonella Typhi has been found in 4 states in 18 people who ate beef fed antibiotics

Question 23

Antibiotic Drug and Host Interaction

Answer 23

• Toxicity to organs
• Allergic reactions
• suppress/ alter microflora
• effective drugs

Question 24

What can tetracycline treatments do to the teeth?

Answer 24

it can cause teeth discoloration

Question 25

Disrupting the normal flora in the intestines can result in:

Answer 25

superinfections

Question 26

Finding an effective drug for treatments:

Answer 26

• Identifying infectious agent (culture)
• Perform sensitivity testing (on Mueller Hinton Agar)
• Often the Minimum Inhibitory Concentration (MIC) is determinined

Question 27

Consequences of Antimicrobial Resistance

Answer 27

infections resistant to available antibiotics and increases cost of treatment