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  • [lowest] that kills 99.9% of inoculum
  • Used for serious infections: endocarditis, meningitis, sepsis
  • [lowest] that prevents growth of culture
  • determined for most infections
Antibiotics that cross BBB
  • antibiotic must accumulate in CSF @ therapeutic levels
  • inflammation facilitates penetration of antibiotic
  • Penicillins: 3rd gen. Cephalosporins
Antibiotics that cross Prostatic Epithelium
  • Fluoroquinolones
Crossing the lipid barrier: lipid solubility & pKa
  • + lipophillic = + crossability
  • Uncharged= + crossability
Immune System
  • Patient factors
  • Immunosuppression in general = need for higher dose or longer tx.
Hepatic & Renal Dysfunction
  • Patient Factors
Accumulation of antibiotics --> toxicity unless dosage is modified

most drugs eliminated in urine, (elderly affected)

: erythromycin, tetracycline
Pregnancy & Lactation
  • Patient Factors
Placenta permeable to ALL antimicrobials, most have no effects
  • Tetracyclines: tooth dysplasia & inhibits bone growth
  • Aminoglycosides: ototoxic
  • Anthelmintics: embryotoxic/teratogenic
Poor Perfusion & Age
  • Patient Factors
  • ↓Q --> ↓ [antimicrobial]
Neonates: kidney/liver not developed     
Contraindicated in Neonates
  • Chloramphenicol: Gray baby syndrome
  • Sulfonamides: kernicterus
Contraindications in Young Kids
  • Tetracycline: inhib. bone growth
  • Fluoroquinolones: inhib. cartilage growth
Bacteriostatic Drugs
inhibit proliferation of bacteria & reduce the spread of infx. until immune system eradicates mo.
Bactericidal Agents
Kill bacteria: [] or time-dependent killing
Narrow Spectrum Antibiotic
Acts only on a single group of mo's
  • Pen G: Gm+
  • Isoniazid: Mycobacterium
Extended Spectrum Antibiotics
Effective against Gm+ & few Gm-
  • Amoxicillin
Broad Spectrum Antibiotics
Wide range of microbial species; may --> superinfection
Combination Therapy (Pros/Cons)
  1. Synergy: B-lactams/Aminoglycosides, Sulfanomides/Trimethoprim
  2. Serious, polymicrobial infx.
  3. Empiric therapy
  4. Used for mycobacterial & HIV infx.: decrease resistance
  1. antagonism: Ex. B-lactams only effective when mo's are proliferating, so using a static agent would antagonize the -cidal drug
Drug Resistance
Resistance= when bacterial growth is not inhibited by the [highest] that the patient can tolerate

  1. Innate resistance
  2. Resistant Strains: spontan. mutation, acquired & selection (alteration in protein expression in resistant mo)
Genetic Alterations
  • Drug resistance
  1. Spontaneous mutation: chromosomal bc of nt changes. Ex. Rifampin-resistant-M. tuberculosis
  2. DNA transfer of plasmids: plasmids passed between cells (result of overuse) Ex. pts. w/ Vanc-R-SA have obtained the R plasmid from Vanc-R-enterococcus
Altered Protein Expression
  • Drug Resistance
  1. Alteration in target proteins: Δ PBP in MRSA, modification of 50S ribosome in Azithro-R-Gm+ mos
  2. Reduced accumulation: mos produce LPS layer or use an efflux pump to ↓ [Ab], Tetracyclines
  3. Enzymatic inactivation: mos produce Ab-inactivating enzymes, Ex. B-lactamases
CTI (Chemotherapeutic Index)
CTI = Toxicitypt/toxicitypathogen
HIGH CTI = selective toxicity
Ampho"terrible" B: CTI=2 (bad!)
Complications with Antimicrobial Therapy
  1. Hypersensitivity: Ex. Penicillins & Sulfonamides (sx. urticaria --> shock)
  2. Direct Toxicity: Elevated [serum] --> direct actions on cellular fx. Ex. Aminoglycosides-->directly damage Organ of Corti
  3. Superinfections: bc of broad spec, or combination therapy
Caused by use of broad spectrum Ab that destroys normal flora of upper resp. & GI/GU tracts
  • C.difficile --> pseudomembraneous collitis
  • Staph Aureus--> staph. enterocolitis
  • Candida--> intestinal candidiasis
Classification of Antimicrobials
  • Chemical Structure (11)
  • Mechanism of Action (5)
  • Activity against specific kids of mos (6)
Inhibition of Cell Wall Synthesis: Bactericidal
  • Mechanism of action
  • B-lactams (Penicillins, Cephalosporins, Monobactams, Carbapenems)
  • Bacitracin
  • Vancomycin: inhibits synthesis of phospholipids & peptidoglycan X-linking
  • Fosfomycin
  • Cycloserine: antimycobacterial
Inhibition of Metabolism
  • Mechanism of action
  • Sulfonamides: inhibit folic acid synthesis of mo
Inhibition of protein synthesis
  • Mechanism of Action
  • Tetracyclines: bind to 30S bacterial ribosome & block tRNA binding to mRNA ribosome complex
  • Aminoglycosides: irreversible inhib, diffuse through channels formed by proteins of Gm- bacteria-->30S:misreading of the DNA
  • Macrolides: bind 50S & block translocation of the ribosome
-mycin: think protein synthesis inhibitor, EXCEPT for 1. Vancomycin 2. Fosfomycin 3. Daptomycin
Inhibition of DNA/RNA fx. or synthesis
  • Mechanism of action
Inhibition of cell membrane function
  • Mechanism of action
  • Daptomycin (unique: depolarizes membrane potential)
  • Polymyxins: bind to & disrupt cell membranes
B-lactam Abs
  • Penicillins
Peptide Ab
  • Lincomycin
  • Clindamycin
Macrolides: 14-16 mem. lactone ring
  • Erythromycin
  • Clarithromycin
Ketolide: (macrolide + ketone @C3 +carbanamine)
  • Telithromycin
  • Linezolid
Common (& safe) for Peds. (& Preggos)
  1. Penicillins: Amoxicillin, Augmentin, Pen. V
  2. Cephalosporins: Cephalexin, Cefprozil, Cefurox
  3. Macrolides: Erythromycin, Azithromycin, Clarithromycin
  4. Co-trimoxazole (SMX-TMP)
Common Antibiotics (List)
  1. Amoxicillin
  2. Augmentin (Amox/Clavulanate)
  3. Azithromycin
  4. Cephalexin
  5. Levaquin
  6. SMX-TMP
  7. Valtrex
  8. Fluconazole: (crosses BBB & antifungal)
  9. Doxycycline
  10. Penicillin V (oral of Pen G)
  11. Ciprofloxacin
  12. Omnicef: 3rd gen, broadest oral cephalosporin
  13. Avelox
  14. Clindamycin
  15. Mupirocin
  • B-lactam Antibiotics
Cell wall synthesis (must be actively proliferating) inhibitors: inhibit transpeptid. & X-linking
4-mem B-lactam ring essential to activity
  • Penicillins
  • Cephalosporins
  • Carbapenems
  • Monobactam: Aztreonam (Azactam)
Penicillins (Classes)
  • B-lactam antibiotics
  1. Standard Penicillins: G (Pfizerpen) & V               Depot Penicillins: Benzathine pen G (Biciliin L-A), Benzathine pen G/Procaine pen G, Procaine pen G
  2. Antistaphylococcal Penicillins: Naficillin, Oxacillin, Dicloxacillin
  3. Extended Spectrum Penicillins: Amoxicillin, Amoxicillin/K+Clavulanate (Augmentin), Ampicillin, Ampicillin/sulbactamNa (Unasyn)
  4. Antipseudomonal Penicillins: Ticarcillin/K+Clavulanate (Timentin), Piperacillin, Piperacillin/tazobactamNa (Unasyn)
  5. Penicillin & Aminoglycides = synergy
B-lactamase inhibitors (can use with mos that produce B-lactamases)
  • B-lactam antibiotics
  1. Augmentin: amox/clavulanate
  2. Unasyn: amp/sulbactam
  3. Timentin: ticarcillin/clavulanate
  4. Zosyn: piperacillin/tazobactam
Cephalosporin Antibiotics
  • B-lactam antibiotics
  1. Cephalexin (Keflex, Panixine), Cefazolin, Cefadroxil
  2. Cefzil, Ceftin, Zinacef, Cefaclor, (Cefoxitin, Cefotan)
  3. Rocephin, Claforan, Fortaz (Tazicef), Cefizox, Omnicef, Suprax, Cedax, Vantin, Spectracef
  4. Cefepime (Maxipime)
  • B-lactam antibiotics
  1. Iminipenum (Primaxin IM/IV): broadest B-lactam on market, UTIs (Entero, Proteus) Resp. tract (Strept. pneum & Klebsiella) & Nosocomial (Serratia & Acinetobacter)
  2. Meropenem (Merrem IV): like Primaxin but >Gm- & <Gm+
  3. Doripenem (Doribax): same as Merrem but +Pseudomonas
  4. Ertapenem (Invanz): like Primaxin but INACTIVE against Pseudomonas & Acinetobacter
what the body does to the drug
what the drug does to the body
Size & MW
  • nature of drugs
MW: 100-1000
too small = no selectivity
too large = poor absorption

large & hydrophillic: need endocytosis
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