II. Definitions
- Antibiotic
- Substances that selectively kill or inhibit Microorganisms
- Targets specific to Microbes include Bacterial cell walls, cell membrane, and 30S or 50S ribosomal subunits
- Most Antibiotics are either naturally produced by Microorganisms, or their synthetic derivatives
- Bacteriocidal Antibiotic
- Bacteriocidal Antibiotics kill Bacteria
- Bacteriostatic Antibiotic
- Bacteriostatic Antibiotics inhibit Bacterial proliferation and spread, but do not kill the Bacteria
- Often works in concert with the Immune System, which subsequently kills Bacteria
- Minimum Inhibitory Concentration (MIC)
- Minimum concentration of an Antibiotic in a culture medium that will suppress Bacterial growth
- MIC cutoffs vary by organism and by Antibiotic, and are typically categorized as susceptible, intermediate or resistant
- One drug's lower MIC values than another drug, does not imply greater efficacy
- (2024) Presc Lett 31(1): 2-3
- Minimum Bactericidal Concentration (MBC)
III. Mechanism: Bacterial Cell Wall Inhibitors (Beta lactams)
-
Penicillins
- Natural Penicillins (e.g. Penicillin V) and semisynthetic Penicillins (e.g. Benzathine Penicillin)
- Cover Streptococci and Anaerobes
- Penicillinase-Resistant Semisynthetic Penicillin (e.g. Dicloxacillin, Nafcillin)
- Cover streptococci and MSSA (Methicillin-Sensitive Staphylococcus Aureus)
- Aminopenicillins (e.g. Amoxicillin, Augmentin)
- Cover streptococci and Gram Negative Bacteria
- Extended Spectrum Penicillin (e.g. Piperacillin Tazobactam)
- Cover streptococci, Gram Negatives and Pseudomonas
- Natural Penicillins (e.g. Penicillin V) and semisynthetic Penicillins (e.g. Benzathine Penicillin)
-
Cephalosporins
- First Generation Cephalosporins (Cephalexin, Cefazolin)
- Covers Gram Positive Cocci (Streptococcus and MSSA), EKP Gram Negative Bacteria
- Second Generation Broad-spectrum Cephalosporins (e.g. Cefuroxime )
- Second Generation Anti-anaerobe Cephalosporins (e.g. Cefotetan, Cefoxitin)
- Covers Gram Positives, Gram Negatives, Bacteroides fragilis
- Third Generation Broad-Spectrum Cephalosporins (e.g. Ceftriaxone, Cefixime, Cefdinir)
- Covers Gram Positive Cocci, EKP and ESP Gram Negative Bacteria
- Third Generation Anti-Pseudomonal Cephalosporins (e.g. Ceftazidime)
- Covers EKP and ESP Gram Negative Bacteria, Pseudomonas
- Poor Gram Positive Cocci coverage, and no Coccobacilli coverage
- Fourth Generation Cephalosporins (e.g. Cefepime)
- Adds to broad spectrum third generation (broad spectrum Gram-positive and Gram-negative organisms)
- Additionally covers Beta-Lactamase resistant organisms and Pseudomonas
- Fifth Generation Cephalosporins (e.g. Ceftaroline)
- Adds to broad spectrum third generation (broad spectrum Gram-positive and Gram-negative organisms)
- Covers Pseudomonas and MRSA (Methicillin Resistant Staphylococcus Aureus)
- First Generation Cephalosporins (Cephalexin, Cefazolin)
- Other Bacterial Cell Wall Inhibitors
- Carbapenems (e.g. Meropenem, Ertapenem)
- Monolactams (e.g. Aztreonam)
- Cover Gram Negative aerobic Bacteriaa
- Lipopeptides (e.g. Daptomycin)
- Covers MRSA, Streptococcal Species, Vancomycin Sensitive Enterococcus
IV. Mechanism: DNA Inhibitors (Antimetabolites)
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Fluoroquinolone
- First Generation Quinolones (Nalidixic Acid)
- Gram Negative Rod efficacy (no Pseudomonas coverage)
-
Second Generation Quinolones (e.g. Ciprofloxacin )
- Covers Aerobic Gram Negative Rods (including Pseudomonas), and some Gram Positive coverage
-
Third Generation Quinolones (e.g. Levofloxacin)
- Covers Gram Negative Rods, with greater Gram Positive Cocci coverage
-
Fourth Generation Quinolones (e.g. Trovafloxacin)
- Covers Gram Negative Rods, Gram Positive Cocci and Anaerobes
- First Generation Quinolones (Nalidixic Acid)
-
Sulfonamides (Inhibit DNA, as well as RNA and Protein synthesis)
- Trimethoprim Sulfamethoxazole (Bactrim, Septra)
- Covers enteric Gram Negative Bacteria (Urinary Tract Infections) and some Gram Positive organisms
- Also used in PCP Pneumonia treatment and prophylaxis (AIDS) and MRSA Skin Infections
- Other Sulfonamides
- Sulfadiazine (Toxoplasmosis prophylaxis)
- Sulfisoxazole (UTI prophylaxis)
- Trimethoprim Sulfamethoxazole (Bactrim, Septra)
- Other DNA Inhibitors
- Metronidazole
- Covers Anaerobes (e.g. Bacteroides, Peptococcus, Clostridioides difficile)
- Nitrofurantoin
- Covers many urinary pathogens (but NOT Pseudomonas, Klebsiella, Proteus Serratia or Acinetobacter)
- Rifamycin (e.g. Rifampin)
- Covers Mycobacterium (esp. Tuberculosis as part of multi-drug regimen)
- Metronidazole
V. Mechanism: Protein Synthesis Inhibitors (at 30s or 50s ribosome)
-
Macrolides
- Erythromycin
- Covers Bacteria without cell walls (Mycoplasma, Legionella, Chlamydia)
- Covers Aerobic Bacteria, Gram Positive Aerobes, Gram Negative Aerobes (except Campylobacter, Pasteurella)
- Extended Spectrum Macrolides (e.g. Azithromycin, Clarithromycin)
- Coverage includes organisms covered by Erythromycin
- Cover Chlamydia trachomatis, Non-tuberculous Mycobacteria, Helicobacter and some respiratory infections
- Fidaxomicin (Dificid)
- Narrow spectrum Antibiotic (C. difficile, Staphylococcus, Enterococcus)
- Minimal systemic absorption when taken orally
- Erythromycin
-
Tetracyclines (e.g. Doxycycline)
- Cover MRSA, Helicobacter Pylori, Tick-borne illness (e.g. Lyme Disease), STDs (e.g. Chlamydia trachomatis)
-
Aminoglycosides (e.g. Gentamicin)
- Cover aerobic and facultative Gram Negative Rods (including Pseudomonas)
- NO anaerobic activity
- Other Protein Synthesis Inhibitors
- Chloramphenicol
- Bacteriostatic activity against Gram Positives, Gram Negatives and Anaerobic Bacteria
- Linezolid
- Bacteriostatic against VRE, MRSA and bactertiocidal against Streptococcus species
- Clindamycin
- Covers Anaerobes and Gram Positive Bacteria (including MRSA coverage, but with high risk of resistance)
- Chloramphenicol