Chapter 9: Antibiotics

Effective treatment requires matching the antibiotic to the specific invading organism, a critical process determined by culture and sensitivity testing, which is vital for reducing the pervasive threat of antimicrobial resistance. The chapter categorizes bacteria by oxygen requirement (aerobic or anaerobic) and staining properties (Gram-positive, often respiratory/soft tissue infections, or Gram-negative, common in GI/GU infections). Several major antibiotic classes are detailed, each with distinct mechanisms of action: Penicillins and Cephalosporins interfere with the structural integrity of the bacterial cell wall during division, necessitating the development of penicillinase-resistant drugs or adjuncts like clavulanic acid to overcome enzymatic bacterial breakdown. Aminoglycosides, Macrolides, and Tetracyclines exert their effects by disrupting bacterial protein synthesis, although tetracyclines carry risks of fetal bone and tooth damage and are contraindicated in pregnancy and young children. Fluoroquinolones prevent bacterial reproduction by interfering with the DNA enzymes required for growth, but they are associated with a black box warning concerning peripheral neuropathy and the risk of tendonitis and tendon rupture. Sulfonamides interrupt the synthesis of folic acid, an essential precursor for bacterial RNA and DNA production. The Antimycobacterials require prolonged, often combination, therapy to treat slow-growing pathogens causing tuberculosis and leprosy, with nursing teaching needed to address unique side effects like orange discoloration of body fluids (rifampin). Specialized classes, including Lincosamides (highly toxic, reserved for severe infections), Lipoglycopeptides (affecting cell wall synthesis and cell membrane function, high fetal risk), and Oxazolidinones (effective against resistant strains like MRSA and VRE, also acting as MAO inhibitors, requiring tyramine-free diet to prevent hypertension), are also covered. Across all therapies, patient teaching emphasizes completing the full course of medication, avoiding unnecessary use for viral infections, monitoring for common adverse effects such as GI distress and secondary superinfections, and recognizing the importance of using accurate measuring devices for pediatric suspensions.