Snapshot A 45-year-old woman presents to urgent care for a large abscess on her forearm. She had fallen and scraped herself a few days ago with subsequent erosions and increasing redness and warmth of the area. Today, she noticed some drainage of pus. A wound culture was sent, and she is started on a cephalosporin for soft tissue infection. Introduction Drugs see below Clinical use bacterial infections Cell Wall Synthesis Inhibitors Penicillins (Bactericidal: inhibits bacterial cell wall synthesis via competitive inhibition of the transpeptidase enzyme) Class Name of Drug(s) Indications Penicillin Penicillin G Aqueous (crystalline) penicillin G Procaine penicillin G Benzathine penicillin G Penicillin V S. pnuemoniae S. pyogenes (group A strep) N. meningitidis T. pallidum L. monocytogenes A. israelii P. multocida Aminopenicillins Ampicillin Amoxicillin ↑ gram-negative coverage Enterococci (group D strep) All others listed above Penicillinase-resistant penicillins Methicillin Nafcillin Oxacillin Cloxacillin Dicloxacillin Penicillinase-producing S. aureus All others listed above Antipseudomonal penicillins Carbenicillin Ticarcillin Piperacillin P. aeruginosa Anaerobic bacteria All others listed above Cephalosporins (Bactericidal: inhibits bacterial cell wall synthesis via competitive inhibition of the transpeptidase enzyme) Class Name of Drug(s) Indications 1st generation Cefazolin Cephalexin Gram-positives Some gram-negatives Skin infection prophylaxis 2nd generation Cefoxitin Cefaclor Cefuroxime Gram-positives Improved gram-negative coverage Anaerobes 3rd generation Ceftriaxone Cefotaxime Ceftazidime Serious gram-negative infections Meningitis Pseudomonas 4th generation Cefepime Same coverage as cephalosporins + expanded Pseudomonas coverage + expanded gram-positive coverage 5th generation Ceftaroline Expanded gram-positive and gram-negative coverage, non-suitable coverage of Pseudomonas Other Cell Wall Inhibitors Class Name of Drug(s) Indications Vancomycin (bactericidal: inhibits bacterial cell wall synthesis by disrupting peptioglycan cross linking) Vancomycin MRSA Patients with PCN or ceph allergies S aureus S epidermidis C. difficile Beta-lactamase inhibitors (beta-lactamse inhibitors that prevent the degradation of beta-lactam antibiotics) Clavulanic acid Sulbactam Tazobactam Gram-positive S. aureus S. epidermis Gram-negative E. coli Klebsiella Carbapenems (Inhibits bacterial cell wall synthesis) Imipenem (+ cilastatin) Meropenem Doripenem Ertapenem Broadest activity of any antibiotic (does NOT cover MRSA, Mycoplasma, and some Pseudomonas) Aztreonam (inhibits bacterial cell wall synthesis) Aztreonam Gram-negative rods Aerobes Difficult-to-treat hospital-acquired infections Polymyxins Polymyxin B Polymyxin E Topical gram-negative infections Bacitracin Bacitracin Topical gram-positive infections Protein Synthesis Inhibitors Anti-30S Ribosomal Subunit Class Name of Drug(s) Indications Aminoglycosides (bactericidal) Gentamicin Neomycin Amikacin Tobramycin Streptomycin Severe gram-negative infections Aerobes only Tetracycline (bacteriostatic) Tetracycline Doxycycline Minocycline Demeclocycline Chlamydia Rickettsia Bacteria without peptidoglycan cell walls Spirochetes V. cholerae H. pylori Anti-50S Ribosomal Subunit Class Name of Drug(s) Indications Macrolides Erythromycin Azithromycin Clarithromycin Outpatient URI, LRI Atypical pneumonia STDs Gram-positive cocci Chloramphenicol (bacteriostatic) Chloramphenicol H. influenzae Bacterial meningitis Brain abscess Bacteroides fragilis Clindamycin (bacteriostatic) Clindamycin Anaerobes above the diaphragm Female GU TSS Linezolid (variable) Linezolid Resistant gram-positives (MRSA, VRE) can cause serotonin syndrome Streptogramins Quinupristin Dalfopristin VRE GAS and S. aureus skin infections Note: bacteriocidal when used together DNA Synthesis Inhibitors Fluoroquinolones (Bactericidal: inhibit DNA gyrase enzyme, inhibiting DNA synthesis) Class Name of Drug(s) Indications 1st generation Nalidixic acid Gram-negative UTIs 2nd generation Ciprofloxacin Norfloxacin Enoxacin Ofloxacin Levofloxacin Gram-negative UTIs Gram-negative GI tract Pseudomonas 3rd generation Gatifloxacin As above + gram-positives 4th generation Moxifloxacin Gemifloxacin As above + gram-positives + anaerobes Other DNA Inhibitors Class Name of Drug(s) Indications Metronidazole (bacteridical: metabolic byproducts disrupt DNA) Metronidazole (Flagyl) Bacteria AND protozoa Anaerobes below the diaphragm C. difficile H. pylori RNA Synthesis Inhibitors Class Name of Drug(s) Indications Rifampin (bactericidal: inhibits RNA transcription) Rifampin TB Leprosy H.influenzae prophylaxis Antistaphylococcal Mycolic Acids Synthesis Inhibitors Class Name of Drug(s) Indications Isoniazid Isoniazid TB Latent TB Folic Acid Synthesis Inhibitors Class Name of Drug(s) Indications Sulfonamides Sulfamethoxazole (SMX) Sulfisoxazole Sulfadiazine Respiratory (S. pneumoniae, H. influenzae) GI (enterics) UTIs PCP and T. gondii Trimethoprim Trimethoprim Respiratory (S. pneumoniae, H. influenzae) GI (enterics) UTIs PCP and T. gondii Pyrimethamine Pyrimethamine Malaria T. gondii Miscellaneous Drugs Mechanism of Action Indications and Side Effects Pyrazinamide Uncertain mechanism: potentially accumulates in cells dsirupting membrane potential and fatty acid synthesis Part of RIPE therapy for TB Can cause hyperuricemia and hepatoxicity Ethambutol Inhibits arabinosyltransferase (inhibiting production of mycobacterium cell wall) Part of RIPE therapy for TB and used for M. avium-intracellulare Can cause optic neuropathy (red-green color blindness) Daptomycin Lipopeptide that disrupts cell membrane Multi-resistant gram-positives such as MRSA and VRE Can cause myopathy (elevated CK and rhabdomyolysis Ineffective in lung infections as drug cannot distinguish between surfactant lipid layer and bacterial membranes, thus is sequestered in surfactant