Infection teacher note
Antibacterials and Their Differentiation
Key types of organisms include:
Bacteria: These are prokaryotic cells, differing in shapes (e.g., cocci/spheres, bacilli/rods, spirilla/spirals) and cell wall characteristics (Gram-positive with a thick peptidoglycan layer, Gram-negative with a thin peptidoglycan layer and an outer membrane). Antibacterials primarily target bacterial cells.
Viruses: These are intracellular parasites that require a host cell to replicate. Antivirals target specific viral replication processes.
Fungi: Eukaryotic organisms with cell walls containing ergosterol. Antifungals target fungal cell structures or metabolic pathways.
Parasites: Diverse group including protozoa (single-celled) and helminths (worms). Antiparasitics target their specific life cycles or structures.
Aerobic organisms: Require oxygen for survival and growth.
Anaerobic organisms: Thrive in environments without oxygen.
Different classes of anti-infective medications to review are antibacterials, antifungals, and antivirals, each with distinct mechanisms of action and spectrums of activity.
Important Medications and Monitoring
Acyclovir: An antiviral used primarily for Herpes simplex virus (HSV-1, HSV-2), Varicella-zoster virus (VZV), and some cases of Epstein-Barr virus (EBV). It works by inhibiting viral DNA synthesis. Important to monitor BUN/Creatinine for potential nephrotoxicity, especially with high doses or in dehydrated patients. Ensure the IV site is patent to prevent extravasation, which can cause tissue damage.
Amoxicillin: A penicillin-class, broad-spectrum antibacterial effective against many Gram-positive and some Gram-negative bacteria, commonly used for respiratory tract infections, UTIs, and ear infections. Side effects include common GI distress (nausea, diarrhea) and the risk of superinfections like candidiasis. Always verify allergy history for anaphylaxis risk; note that it can reduce the effectiveness of oral contraceptives, requiring alternative birth control methods.
Amphotericin B: A potent antifungal agent, often reserved for severe, life-threatening systemic fungal infections. Its mechanism involves binding to ergosterol in fungal cell membranes, leading to cell leakage. It is highly nephrotoxic; rigorous monitoring of renal function (BUN and creatinine levels) and electrolyte levels (potassium, magnesium) is crucial. Infusion-related reactions (fever, chills, rigors) are common.
Chloroquine: An antimalarial drug, also used for some autoimmune conditions. It may cause visual symptoms, including retinopathy, necessitating regular ophthalmologic exams. Recommend wearing sunglasses to mitigate photophobia and taking with food to minimize GI disturbances (nausea, abdominal pain).
Aztreonam: A monobactam antibacterial, primarily effective against multidrug-resistant Gram-negative bacteria, including Pseudomonas aeruginosa. It is generally safe for patients with penicillin allergies. Monitor IV site for thrombophlebitis and pain, ensuring proper dilution and slow infusion.
Adverse Reactions and Client Education
Ciprofloxacin: A fluoroquinolone antibacterial, it inhibits bacterial DNA gyrase and topoisomerase IV. Risk of Achilles tendon rupture, especially in older adults, patients on corticosteroids, or those with renal impairment; advise immediate reporting of tendon pain. Also causes phototoxic reactions; clients must avoid direct sunlight and use broad-spectrum sunscreen. Other side effects include CNS effects (dizziness, confusion) and QT prolongation.
Cephalosporins: Beta-lactam antibacterials that inhibit bacterial cell wall synthesis. They have cross-sensitivity with penicillin allergies; always inquire about penicillin reactions and watch for signs of anaphylaxis (e.g., rash, swelling, difficulty breathing). Cephalexin (a first-generation cephalosporin) can lead to superinfections like Clostridioides difficile (C. diff) diarrhea, requiring prompt recognition and treatment.
Gentamicin: An aminoglycoside antibacterial that inhibits bacterial protein synthesis, primarily used for serious Gram-negative bacterial infections. Ototoxicity (hearing loss, vestibular dysfunction) and nephrotoxicity are significant concerns. Monitor peaks (30-60 min post-infusion to ensure efficacy) and troughs (just before next dose to minimize toxicity) to maintain therapeutic drug levels and prevent adverse effects.
Medication-Specific Concerns
Imipenem: A carbapenem antibacterial, known for its very broad spectrum against Gram-positive, Gram-negative, and anaerobic bacteria. It carries a risk of superinfection and seizures (especially at high doses or in patients with CNS disorders). Monitor liver and renal labs due to potential organ toxicity. It is typically co-administered with cilastatin to prevent its inactivation by renal dehydropeptidase I.
Isoniazid: A first-line antimycobacterial drug used for the treatment and prophylaxis of tuberculosis. It works by inhibiting mycolic acid synthesis in the mycobacterial cell wall. Can cause peripheral neuropathy (numbness/tingling in extremities); prophylactic Pyridoxine (Vitamin B6) supplementation ( mg/day) is often prescribed to prevent this. Also monitor for hepatotoxicity (elevated LFTs, jaundice).
Metronidazole: An antibacterial and antiprotozoal agent effective against anaerobic bacteria (e.g., C. diff) and certain parasites (e.g., Giardia, Trichomonas). Caution with alcohol consumption due to a severe disulfiram-like reaction (nausea, vomiting, flushing, tachycardia, hypotension, headache). Advise patients to avoid alcohol during therapy and for at least days after.
Nitrofurantoin: An antibacterial used specifically for the treatment and prophylaxis of uncomplicated urinary tract infections (UTIs). It may cause reddish-brown urine, which is a harmless side effect. Significant side effects include acute and chronic lung damage (pulmonary fibrosis), peripheral neuropathy, and hepatotoxicity. Advise patients to report dyspnea, cough, or numbness/tingling.
Risk and Education at Point of Care
Rifampin: An antimycobacterial drug used for tuberculosis, often in combination therapy. It works by inhibiting bacterial RNA synthesis. It significantly decreases the effectiveness of oral contraceptives, requiring alternative birth control methods. It also turns bodily fluids (urine, sweat, tears, saliva) red-orange, which is a harmless but noticeable side effect, and can stain contact lenses.
Vancomycin: A glycopeptide antibacterial used for serious Gram-positive infections, including MRSA and C. diff colitis. It inhibits bacterial cell wall synthesis. Rapid infusion can cause Red Man Syndrome (flushing, rash, pruritus, tachycardia, hypotension) due to histamine release; administer slowly over at least minutes. Monitor renal function and trough levels to prevent nephro/ototoxicity.
Tetracycline: A broad-spectrum antibacterial that inhibits bacterial protein synthesis. Causes photosensitivity, so advise sun protection. Should not be given to children under years old or pregnant women due to the risk of permanent teeth discoloration (yellow-grey-brown). Avoid taking with calcium products (milk, antacids, iron supplements) as they chelate the drug, reducing its absorption; administer at least hours before or hours after.
Definitions
Superinfection: A new infection arising during the treatment of a primary infection, typically caused by the overgrowth of opportunistic pathogens due to the disruption of normal microbial flora by broad-spectrum antibiotics. Monitor for signs such as oral candidiasis (thrush), vaginal yeast infections, or Clostridioides difficile-associated diarrhea in patients receiving carbapenems (like imipenem) or other broad-spectrum agents.