C9 - Antimicrobials Flashcards by Mark James Mateo

chemical substances produced by microorganisms with the capacity to inhibit (bacteriostatic) or kill (bactericidal) other microorganisms

can also be synthesized by means of chemical procedures that are independent from microbial activity

ANTIBIOTICS

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Antibiotics examples

Bacitracin
Polymyxin
Cephalosporins
Gentamicin
Penicillin
Erythromycin
Neomycin
Amphotericin B
Nystatin
Chloramphenicol

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Source of Bacitracin

Bacillus subtilis

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Source of Polymyxin

Bacillus polymyxa

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Source of Cephalosporins

Cephalosporium

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Source of Gentamicin

Micromonospora purpurea

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Source of Erythromycin

Streptomyces erythraeus

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Source of Penicillin

Penicillium notatum

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Source of Amphotericin B

Streptomyces nodosus

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Source of Nystatin

Streptomyces noursei

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Source of Neomycin

Streptomyces fradiae

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Source of Chloramphenicol

Streptomyces venezuelae

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antimicrobial agents that inhibit bacterial
growth but generally do not kill the organism

BACTERIOSTATIC AGENTS

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agents that usually kill target organisms

BACTERICIDAL AGENTS

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Generally Bacteriostatic agents

Chloramphenicol
Erythromycin and other macrolides
Clindamycin
Sulfonamides
Trimethoprim
Tetracyclines
Tigecycline
Linezolid
Quinupristin/dalfopristin

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Generally Bactericidal agents

Aminoglycosides
ẞ-lactams
Vancomycin
Daptomycin
Teicoplanin
Telavancin
Quinolones (e.g., ciprofloxacin, levofloxacin)
Rifampin
Metronidazole

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effective against limited number of pathogens

Narrow-Spectrum

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Narrow-Spectrum antimicrobials

bacitracin,
clindamycin,
dapsone,
erythromycin,
isoniazid,
penicillin,
polymyxin B and
vancomycin

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destroys different kinds of organisms

Broad-Spectrum

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Broad-Spectrum examples

ampicillin,
cephalosporins,
chloramphenicol,
ciprofloxacin,
rifampicin,
sulphonamides,
trimethoprim and
tetracyclin

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Classification of Antibacterial Drugs

Natural Drugs
Semi-synthetic Drugs
Synthetic Drugs

produced by bacteria and fungi

Natural Drugs

Natural Drugs examples

amphotericin B,
erythromycin,
kanamycin,
neomycin,
nystatin,
rifampicin,
streptomycin,
tetracyclin,
vancomycin,
bacitracin,
gentamicin,
polymyxin,
griseofulvin,
penicillin and
cephalosporin

modified natural drugs with added chemical group

Semi-synthetic Drugs

Semi-synthetic Drugs Examples

ampicillin, carbenicillin and methicillin

chemically produced drugs

Synthetic Drugs

Synthetic Drugs Examples

sulphonamides, trimethoprim, chloramphenicol, ciprofloxacin and dapson

MODE OF ACTION OF ANTIBACTERIAL AGENTS

A. Inhibitors of Cell Wall Synthesis B. Protein Synthesis Inhibitors C. Nucleic Acid Synthesis Inhibitors D. Cell Membrane Inhibitors E. Essential Metabolite Inhibitors

most selective with a high therapeutic index inhibit the activity of the transpeptidase enzymes in which cell growth stops and death of the cell often follows

Inhibitors of Cell Wall Synthesis

Inhibitors of Cell Wall Synthesis examples

β-Lactam (Beta-Lactam) Vancomycin Bacitracin Isoniazid Cephalosporins Penicillinase-resistant penicillin drugs Carbenicillin

inhibits transpeptidation and cell wall synthesis

β-Lactam (Beta-Lactam)

β-Lactam (Beta-Lactam) examples

penicillins, cephalosporins, carbapenems and monobactams

inhibits translocation and elongation of peptidoglycan layer

Vancomycin

inhibits synthesis of peptidoglycan precursors

Bacitracin

acts only on growing cells and can either be bactericidal or bacteriostatic

Isoniazid

Cephalosporins examples

cephalothin, cefoxitin, ceftriaxone, cephalexin, cefixime and cefoperazone

Penicillinase-resistant penicillin drugs examples

methicillin, nafcillin and oxacilin

binds with 30S subunit that results in the misreading of mRNA and thus interferes with aminoacyl-tRNA binding also binds with 50S subunit that results in the inhibition of peptidyl transferase and peptide chain elongation

Protein Synthesis Inhibitors

Protein Synthesis Inhibitors Examples: Binds to 30S

aminoglycosides(gentamicin), kanamycin, neomycin, streptomycin, tobramycin), tetracyclins, spectinomycin mioglycosides

Protein Synthesis Inhibitors Examples: Binds to 50S

chloramphenicol, erythromycin, lincomycin and clindamycin

blocks the initial step in protein synthesis

Linezolid

C. Nucleic Acid Synthesis Inhibitors examples

Rifampicin Quinolone Metronidazole

 inhibits RNA polymerase

Rifampicin

interferes with DNA gyrase and topoisomerase IV and highly effective for enteric bacteria (e.g, E.coli)

Quinolone

Quinolone examples

ciprofloxacin, norfloxacin and levofloxacin

disrupts DNA and effective against anaerobic bacteria

Metronidazole

D. Cell Membrane Inhibitors

Polymyxin B and E

for gram(-) bacteria (e.g., Pseudomonas aeruginosa) and as topical antibiotic

Polymyxin B and E

Essential Metabolite Inhibitors examples

Sulfamethoxazole (SMZ) Trimethoprim (TMP) Dapsone Isoniazid

inhibits folic acid metabolism and has a high therapeutic index

Sulfamethoxazole (SMZ)

blocks tetrahydrofolate synthesis

Trimethoprim (TMP)

interferes with folic acid synthesis

Dapsone