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Antibiotic Classification & Mechanism

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Topic updated on 10/23/13 2:20am
Overview of By Mechanism
 
 
 
Antibiotic Grouping By Mechanism
Cell Wall Synthesis Penicillins
Cephalosporins
Vancomycin
Beta-lactamase Inhibitors
Carbapenems
Aztreonam
Polymycin
Bacitracin
Protein Synthesis Inhibitors

Inhibit 30s Subunit
Aminoglycosides (gentamicin)
Tetracyclines
Inhibit 50s Subunit
Macrolides
Chloramphenicol
Clindamycin
Linezolid 
Streptogramins

DNA Synthesis Inhibitors Fluoroquinolones 
Metronidazole
RNA synthesis Inhibitors Rifampin
Mycolic Acid synthesis inhibitors
Isoniazid
Folic Acid synthesis inhibitors Sulfonamides
Trimethoprim
 
Antibiotic Classification & Indications
 
Inhibits Cell Wall Synthesis
Penicillins
(bactericidal: blocks cross linking via competitive inhibition of the transpeptidase enzyme)
Class/Mechanism Drugs Indications (**Drug of Choice) Toxicity
Penicillin Penicillin G
Aqueous penicillin G
Procaine penicillin G
Benzathine penicillin G
Penicillin V

Strep. pyogenes (Grp.A)**
Step. agalactiae (Grp.B)**
C. perfringens(Bacilli)**

Hypersensitivity reaction
Hemolytic anemia
Aminopenicillins Ampicillin
Amoxicillin

Above + 
↑ Gram-negative:
E. faecalis**
E. Coli**

 Above
Penicillinase-resistant-penicillins Methicillin
Nafcillin
Oxacillin
Cloxacillin
Dicloxacillin
Above +
PCNase-producingStaph. aureus
Above + 
Interstitial nephritis
Antipseudomonal penicillins Carbenicillin
Ticarcillin
Piperacillin
Above +
Pseudomonas aeruginosa**

 Above
Cephalosporins
(bactericidal: inhibits bacterial cell wall synthesis via competitive inhibition of the transpeptidase enzyme)
1st generation  Cefazolin
Cephalexin
Staph. aureus**
Staph. epidermidis**
Some Gram-negatives:
E. Coli
Klebsiella
Allergic reaction
Coombs-positive anemia (3%)
2nd generation Cefoxitin
Cefaclor
Cefuroxime
Above +
 Gram-negative
Allergic Reaction
ETOH Disulfiram reaction
3rd generation Ceftriaxone
Cefotaxime
Ceftazidime
Cefepime (4th generation)
Above +
 Gram-negative
Pseudomonas
Allergic Reaction
ETOH Disulfiram reaction
Other Cell Wall Inhibitors
Vancomycin q
(bactericidal: disrupts peptioglycan cross-linkage)
 Vancomycin

MRSA**
PCN/Ceph allegies**
S. aureus
S. epidermidis

Red man syndrome
Nephrotoxicity
Ototoxicity
Beta-lactamase Inhibitors 
(bactericidal: blocking cross linking)
Clavulanic Acid
Sulbactam
Tazobactam

S aureus**
S epidermis**
E.Coli**
Klebsiella**

Hypersensitivity Reaction
Hemolytic anemia
Carbapenems

Imipenem (+ cilastatin)
Meropenem
Doripenem
Ertapenem
Broadest activity of any antibiotic
(except MRSA, Mycoplasma)
 
Aztreonam

Aztreonam Gram-negative rods
Aerobes
Hospital-acquired infections
 
Polymyxins Polymyxin B
Polymyxin E
Topical Gram-negative infections  
Bacitracin Bacitracin Topical Gram-positive infections  
Protein Synthesis Inhibition
Anti-30S ribosomal subunit
Aminoglycosides
(bactericidal: irreversible binding to 30S) q
Gentamicin
Neomycin
Amikacin
Tobramycin
Streptomycin
Aerobic Gram-negatives
Enterobacteriaceae 
Pseudomonas
Nephrotoxicity
Ototoxicity
Tetracyclines
(bacteriostatic: blocks tRNA)
Tetracycline
Doxycycline
Minocycline
Demeclocycline

Rickettsia
Mycoplasma
Spirochetes (Lyme's disease)

Hepatotoxicity
Tooth discoloration Impaired growth
Avoid in children < 12 years of age
Anti-50S ribosomal subunit
Macrolides
(bacteriostatic: reversibly binds 50S)
Erythromycin
Azithromycin
Clarithromycin
Streptococcus
H. influenzae
Mycoplamsa pneumonia

Coumadin Interaction (cytochrome P450)

Chloramphenicol
(bacteriostatic)
Chloramphenicol H influenzae
Bacterial Meningitis
Brain absces
Aplastic Anemia
Gray Baby Syndrome
Lincosamide
(bacteriostatic: inhibits peptidyl transferase by interfering with amino acyl-tRNA complex)
Clindamycin

Bacteroides fragilis
S aureus
Coagulase-negative Staph & Strep
Excellent Bone Penetration

Pseudomembranous colitis
Hypersensitivity Reaction

Linezolid
(variable)
Linezolid Resistant Gram-positives  
Streptogramins Quinupristin
Dalfopristin
VRE
GAS and S. aureus skin infections
 
DNA Synthesis Inhibitors
Fluoroquinolones
(bactericidal: inhibit DNA gyrase enzyme, inhibiting DNA synthesis)
1st generation   Nalidixic acid Steptococcus
Mycoplasma
Aerobic Gram +

Phototoxicity
Achilles tendon rupture
Impaired fracture healing 
q

2nd generation Ciprofloxacin
Norfloxacin
Enoxacin
Ofloxacin
Levofloxacin
As Above +Pseudomonas as above
3rd generation Gatifloxacin As above + Gram-positives as above
4th generation Moxifloxacin
Gemifloxacin
As above + Gram-positives + anaerobes as above
Other DNA Inhibitors
Metronidazole
(bacteridical: metabolic biproducts disrupt DNA)
Metronidazole (Flagyl) Anaerobics Seizures
Crebelar dysfunction
ETOH disulfram reaction
RNA Synthesis Inhibitors
Rifampin
(bactericidal: inhibits RNA transcription by inhibiting RNA polymerase)
Rifampin Staphylococcus
Mycobacterium 
(TB) q
Body fluid discoloration
Hepatoxicity (with INH)
Mycolic Acids Synthesis Inhibitors
Isoniazid Isoniazidz TB
Latent TB
 
Folic acid Synthesis Inhibitors
Trimethoprim/Sulfonamides
(bacteriostatic: inhibition with PABA)
Trimethoprim/Sulfamethoxazole (SMX)
Sulfisoxazole
Sulfadiazine
UTI organisms
Proteus
Enterobacter

Thrombocytopenia
Avoid in third trimester of pregnancy

Pyrimethamine Pyrimethamine Malaria
T. gondii
 
 
 Bacteria Overview
 
Gram Postive Cocci
Staphylococcus Staph. aureus
MSSA
MRSA
Staph. epidermis
Staph saprophyticus
Streptococcus Strep pneumoniae
Strep pyogenes (Group A) 
Strep agalacticae (Group B) 
Strep viridans
Strep Bovis (Group D)
Enterococci E. faecalis (Group D strep)
Gram Positive Bacilli
Spore Forming

Bacillus anthracis
Bacillus cereus
Clostridium tetani
Clostridium botulinum
Clostridium perfringens
Clostridium difficile

Non-Spore Forming Corynebacterium diphtheriae
Listeria monocytogenes
Gram Negative Cocci
Neisseria Neisseria meningitidis
Neisseria gonorrhoeae
Gram Negative Bacilli
Enterics Escherichia coli
Salmonella typhi
Salmonella enteridis
Shigella dysenteriae
Klebsiella pneumoniae
Serratia
Proteus
Campylobacter jejuni
Vibrio cholerae
Vibrio parahaemolyticus/vulnificus
Helicobacter pylori
Pseudomonas aeruginosa
Bacteroides fragilis
Respiratory bacilli Haemophilus influenzae
Haemophilius ducreyi
Bordatella pertussis
Zoonotic bacilli Yersinia enterocolitica
Yersinia pestis
Brucella 
Francisella tularensis 
Pasteurella multocida 
Bartonella henselae
Other
Gardnerella vaginalis
Other Bacteria
Mycobacteria Mycobacterium tuberculosis
Mycobacterium leprae
MOTTS
Spirochetes Borrelia burgdorferi
Leptospira interrogans
Treponema pallidum
Chlamydiaceae Chlamydia trachomatis
Chlamydophila 
Rickettsia
Ehrlichia
Mycoplasmataceae Mycoplasma pneumoniae
Ureaplasma urealyticum
Fungus-like Bacteria Actinomyces israelii
Nocardia
 
Antibiotic Resistance Mechanisms
  • Bacteria develop ability to hydrolyze these drugs using β lactamase
    • confers resistance to penicillin
    • e.g. E. coli, Staph epidermidis, Pseudomonas aeruginosa, Klebsiella pneumoniae
    • add β lactamase inhibitor e.g. clavulanic acid in amoxicillin-clavulanate (Augmentin)
  • Genetic mutation of mecA
    • a bacterial gene encoding a penicillin-binding protein. New PBP has reduced affinity for antibiotics
    • confers resistance to methicillin, oxacillin, nafcillin
    • e.g. MRSA
  • Altered cell wall permeability
    • confers resistance to tetracyclines, quinolones, trimethoprim and β lactam antibiotics
  • Creation of biofilm barrier
    • provides an environment where offending bacteria can multiply safe from the hoste immune system
      • Salmonella
      • Staph epidermidis
  • Active efflux pumps
    • confers resistance to erythromycin and tetracycline
    • e.g. msrA gene in Staph
  • Altered peptidoglycan subunit (altered D-alanyl-D-alanine of NAM/NAG-peptide) 
    • confers resistance to vancomycin
    • e.g. vancomycin resistant enterococcus (VRE) 
  • Ribosome alteration
    • erm gene confer inducible resistance to MLS (macrolide lincosamide streptogranin) agents via methylation of 23s rRNA
    • demonstrate using D zone test   
      • for inducible clindamycin resistance in Staph and beta hemolytic Strep
Penicillins
  • Mechanism
    • interfer with bacterial cell wall synthesis
  • Subclassification and tested examples
    • natural
      • penicillin G
    • penicillinase-resistant
      • methicillin (Staphcillin)
    • aminopenicillins
      • ampicillin (Omnipen, Polycillin)
 
Cephalosporins
  • Overview
    • bactericidal
  • Mechanism
    • disrupts the synthesis of the peptidoglycan layer of bacterial cell walls  
      • does so through competitive inhibition on PCB (penicllin binding proteins)
      • peptidoglycan layer is important for cell wall structural integrity.
    • same mechanicsm of action as beta-lactam antibiotics (such as penicillins)
  • Subclassification and tested examples
    • first generation
      • cefazolin (Ancef, Kefzol)
    • second generation
      • cefaclor (Ceclor)
    • third generation
      • cefriazone (Rocephin)
    • fourth generation
      • cefepime (Maxipime)
Fluoroquinolones
  • Mechanism
    • blocks DNA replication via inhibition of DNA gyrase 
  • Side effects
    • inhibit early fracture healing through toxic effects on chondrocytes 
    • increased rates of tendinitis, with special predilection for the Achilles tendon. 
      • tenocytes in the Achilles tendon have exhibited degenerative changes when viewed microscopically after fluoroquinolone administration.
      • recent clinical studies have shown an increased relative risk of Achilles tendon rupture of 3.7. 
  • Subclassification and tested examples
    • ciprofloxacin (Cipro)
    • levofloxacin (Levaquin)
Aminoglycosides
  • Mechanism
    • bactericidal
    • inhibition of bacterial protein synthesis 
      • work by binding to the 30s ribosome subunit, leading to the misreading of mRNA. This misreading results in the synthesis of abnormal peptides that accumulate intracellularly and eventually lead to cell death. These antibiotics arebactericidal.
  • Subclassification and tested examples
    • gentamicin (Garamycin)
Vancomycin
  • Coverage
    • gram-positive bacteria
  • Mechanism
    • bactericidal
    • an inhibitor of cell wall synthesis 
  • Resistance
    • increasing emergence of vancomycin-resistant enterococci has resulted in the development of guidelines for use by the  (CDC) 
    • indications for vancomycin 
      • serious allergies to penicillins or beta-lactam antimicrobials 
      • serious infections caused by susceptible organisms resistant to penicillins (MRSA, MRSE)
      • surgical prophylaxis for major procedures involving implantation of prostheses in institutions with a high rate of MRSA or MRSE
Rifampin
  • Most effective against intracellular phagocytized Staphylococcus aureus in macrophages 
Linezolid
  • Linezolid binds to the 23S portion of the 50S subunit and acts by preventing the formation of the initiation complex between the the 30S and 50S subunits of the ribosome.
Splenectomy
  • Splenectomy patients or patients with functional hyposplenism require the following vaccines and/or antibiotics 
    • Pneumococcal immunization
    • Haemophilus influenza type B vaccine
    • Meningococcal group C conjugate vaccine
    • Influenza immunization
    • Lifelong prophylactic antibiotics (oral phenoxymethylpenicillin or erythromycin)

 

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Qbank (10 Questions)

TAG
(OBQ12.53) What mechanism allows Staphylococcus epidermidis to adhere to surfaces and resist phagocytosis? Topic Review Topic

1. Creation of active efflux pumps
2. Methylation of 23s rRNA
3. Biofilm production
4. Alteration of cell wall permeability
5. Beta-lactamase production

PREFERRED RESPONSE ▶
TAG
(OBQ11.70) Which of the following antibiotic families inhibit bacterial DNA gyrase? Topic Review Topic

1. Quinolones
2. Penicillins
3. Aminoglycosides
4. Macrolides
5. Sulfonamides

PREFERRED RESPONSE ▶
TAG
(OBQ11.138) MecA is the bacterial gene which encodes for a penicillin-binding protein that alters the efficacy of beta-lactam antibiotics. Which of the following species of bacteria are known to produce mecA? Topic Review Topic

1. Clostridium dificile
2. Clostridium tetani
3. Vancomycin-resistant enterococcus
4. Methicillin-resistant staphylococcus aureus
5. Streptococcus epidermidis

PREFERRED RESPONSE ▶
TAG
(OBQ08.275) What is the mechanism of action of vancomycin? Topic Review Topic

1. inhibition of cell wall synthesis
2. increase cell wall permeability
3. ribosomal inhibition
4. interference with DNA metabolism
5. antimetabolite action

PREFERRED RESPONSE ▶
TAG
(OBQ06.87) Which class of antibiotics inhibit early fracture healing through toxic effects on chondrocytes? Topic Review Topic

1. cephalosporins
2. quinolones
3. penicillins
4. macrolides
5. sulfonamides

PREFERRED RESPONSE ▶
TAG
(OBQ06.134) Rifampin is highly effective against phagocytized intracellular Staphylococcus aureus especially in combination with other antibiotics because of its: Topic Review Topic

1. Hydrophilic activity
2. High cell penetration
3. Structural similarity to penicillin
4. Structural similarity to vancomycin
5. Beta-lactamase activity

PREFERRED RESPONSE ▶
TAG
(OBQ05.99) A 62-year-old man undergoes an uncomplicated total shoulder replacement 9 months ago. What is an appropriate choice of prophylactic antibiotics to be taken prior to dental work if he has no allergies? Topic Review Topic

1. daptomycin 600 milligrams intravenous 2 hours prior to procedure
2. amoxicillin 4 grams oral 1 week prior to procedure
3. levaquin 500 milligrams oral 1 hour prior to procedure
4. trimethoprim-sulfamethoxazole 2 tablets double-strength oral 1 hour prior to procedure
5. cephalexin 2 grams oral 1 hour prior to procedure

PREFERRED RESPONSE ▶
TAG
(OBQ04.42) A splenectomy is performed in a 7-year-old boy following a motor vehicle accident. All of the following are recommended for long-term management EXCEPT: Topic Review Topic

1. Pneumococcal vaccination
2. Haemophilus influenza type B vaccination
3. Meningococcal group C vaccination
4. Lifelong prophylactic antibiotics
5. Hepatitis A vaccination

PREFERRED RESPONSE ▶
TAG
(OBQ04.58) All of the following antibiotics function by interfering with protein synthesis by inhibiting ribosomes EXCEPT Topic Review Topic

1. gentamycin
2. tobramycin
3. vancomycin
4. erythromycin
5. linezolid

PREFERRED RESPONSE ▶
TAG
(OBQ04.190) All of the following antibiotics function by interfering with cell wall synthesis EXCEPT Topic Review Topic

1. Cefazolin
2. Penicillin G
3. Vancomycin
4. Imipenem
5. Gentamicin

PREFERRED RESPONSE ▶




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