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Antimicrobial Drugs Notes

Antimicrobial Drugs Notes

Key Terms

  • Bactericidal drugs: Kill bacteria.

  • Bacteriostatic drugs: Inhibit the growth of bacteria.

  • Antibacterials: Chemicals that inhibit bacterial growth or kill bacteria.

  • Antibiotics: Chemicals produced by one microorganism to inhibit the growth of another.

Mechanisms of Antibacterial Action

  • Inhibition of bacterial cell wall synthesis: Interference leads to cell lysis.

  • Alteration of membrane permeability: Disrupts cell functions.

  • Inhibition of protein synthesis: Affects bacterial growth and reproduction.

  • Inhibition of RNA and DNA synthesis: Prevents bacterial replication.

  • Interference with metabolism: Disrupts essential metabolic processes in bacteria.

Factors Affecting Body Defenses

  • Age, Nutrition, Immunoglobulins: Influence the effectiveness of defenses against infection.

  • **Circulation: ** Helps transport immune cells to infection sites.

  • WBC count: Indicator of immune response and infection.

  • Organ function: Impacts the body’s ability to respond to infection.

Drug Resistance

  • Resistance development: Occurs when bacteria multiply despite antibiotic treatment.

  • Antibiotic misuse: Can occur when antibiotics are taken for viral infections or when not needed, leading to increased resistance.

  • Cross-resistance: Can occur between similar acting antibacterial drugs (e.g., PCN and cephalosporins).

Antibiotic Combination Effects

  • Additive Effect: Combined antibacterial activity.

  • Potentiative Effect: One drug enhances the effect of another.

  • Antagonistic Effect: When one bactericidal and one bacteriostatic drug are combined, their desired effects may be reduced.

Adverse Reactions to Antibacterials

  • General reactions: Hypersensitivity, rash, pruritus, anaphylactic shock.

  • Superinfection: Occurs when normal flora is killed, leading to infections in areas such as the mouth and intestines.

  • Organ Toxicity: Possible effects include ototoxicity, hepatotoxicity, and nephrotoxicity.

Antibacterial Spectrum

  • Narrow Spectrum: Effective against specific bacterial types (e.g., Gram-positive bacteria: penicillin).

  • Broad Spectrum: Effective against both Gram-positive and Gram-negative bacteria (e.g., tetracyclines, cephalosporins).

Penicillins Overview

  • Structure: Natural antibacterial agent derived from Penicillium.

  • Action: Interferes with bacterial cell wall synthesis; can be bacteriostatic or bactericidal.

  • Types:

    • Narrow Spectrum: Effective primarily against Gram-positive bacteria (e.g., penicillin G, V).

    • Broad Spectrum: Treats both Gram-positive and negative bacteria (e.g., amoxicillin, ampicillin).

    • Penicillinase-Resistant: Effective against penicillinase-producing Staphylococcus aureus (e.g., dicloxacillin).

    • Extended-Spectrum: Useful against more resistant Gram-negative bacteria (e.g., piperacillin-tazobactam).

Side Effects of Penicillins

  • Common effects include GI distress, tooth discoloration, and inflammation of the mouth.

  • Risk of Clostridium difficile-associated diarrhea and superinfection.

Clinical Judgment: Penicillins

  • Assess for allergies: History of hypersensitivity and priority on lab results.

  • Monitor for infections and superinfections.

  • Action: Obtain cultures before beginning therapy.

Cephalosporins Overview

  • Definition: Derived from fungus; inhibits bacterial cell wall synthesis.

  • Generations:

    • First Generation: Mostly effective against Gram-positive bacteria (e.g., cefazolin).

    • Second Generation: Broader effect (e.g., cefoxitin, cefuroxime).

    • Third Generation: Effective against Pseudomonas and more resistant to beta-lactamases (e.g., cefotaxime).

    • Fourth Generation: Broad-spectrum, resistant to beta-lactamases, good CNS penetration (e.g., cefepime).

Side Effects of Cephalosporins

  • Possible effects include headache, GI distress, nephrotoxicity, and risk of anaphylaxis.

Clinical Judgment: Cephalosporins

  • Assess allergies and lab results, especially renal and liver function.

  • Complete cultures before starting therapy.

Macrolides Overview

  • Mechanism: Inhibit protein synthesis via the 50S ribosomal subunit.

  • Coverage: Effective against Gram-positive and some Gram-negative bacteria (e.g., azithromycin, erythromycin).

Side Effects of Macrolides

  • Common effects include GI distress, hepatotoxicity, and increased drug interactions.

Clinical Judgment: Macrolides

  • Monitor for liver function and adjust administration based on meal timing.

Oxazolidinones Overview

  • Mechanism: Inhibit protein synthesis; effective against Gram-positive bacteria.

  • Use: For severe infections like MRSA and VREF (e.g., linezolid).

Lincosamides Overview

  • Definition: Inhibit protein synthesis; utilized for skin, respiratory, and more infections (e.g., clindamycin).

Glycopeptides Overview

  • Mechanism: Inhibits cell wall synthesis, effective against Gram-positive bacteria including MRSA (e.g., vancomycin).

  • Adverse effect: Red man syndrome due to rapid infusion.

Lipopeptides Overview

  • Action: Binds to bacterial membranes; used for skin infections and septicemia (e.g., daptomycin).

  • Side Effects: Include hypotension and CNS effects.

Slide 2: Bacteria – The Basics

Two main bacteria shapes:

  • Bacilli = Rod-shaped

  • Cocci = Spherical (round)

Slide 3: Key Terms – Know These!

  1. Antibacterials → Drugs that fight bacterial infections.

  2. Antibiotics → Natural or man-made chemicals that kill bacteria or stop them from growing.

  3. Bactericidal = Kills bacteria.

  4. Bacteriostatic = Stops bacteria from growing (but doesn’t kill them).

Slide 4: How Antibacterials Work

Antibacterials fight bacteria by doing 1 or more of these:

  • Blocking cell wall synthesis → Bacteria can’t grow strong walls = they die.

  • 🚪 Changing membrane permeability → Messes up what enters/exits bacteria.

  • 🛑 Stopping protein synthesis → Bacteria can’t make the proteins they need.

  • Blocking RNA/DNA synthesis → Bacteria can’t grow or multiply.

  • 🔒 Interfering with metabolism inside the bacterial cell.

Slide 5: Body Defenses – How We Fight Back

Your body’s natural defenses help antibiotics work:

  • Age (older or very young = weaker defense)

  • Nutrition

  • WBCs (White blood cells)

  • Circulation

  • Organ function (especially liver/kidneys)

  • Immunoglobulins (antibodies)

Slide 6: What is Drug Resistance?

Drug resistance happens when bacteria stop responding to antibiotics that used to work.

💥 Causes of Drug Resistance:

  • Overuse or misuse of antibiotics:

    • Taking them for viral infections (like a cold or flu)

    • Not finishing the full prescription

    • Skipping doses

  • These actions give bacteria a chance to adapt and become stronger.

⚠ Cross-Resistance:

  • Happens when bacteria become resistant to multiple antibiotics that work the same way.

  • Example: Resistance to penicillin might also mean resistance to cephalosporins (because they work similarly).

🚫 Antibiotic Misuse = Trouble

Misusing antibiotics = More resistant bacteria = Fewer meds that work = Harder to treat infections

Slide 7: Combining Antibiotics – What Happens When We Mix Them?

Sometimes doctors use 2 antibiotics together. The result can be helpful… or not.

💊 Types of Antibiotic Interactions:

  1. Additive

    • Effect = Both drugs work together equally.

    • 🔹 Example: A + B = A+B

    • Each drug helps, but doesn’t boost the other.

  1. Potentiative (Synergistic)

    • One drug boosts the power of the other.

    • 🔹 Example: A + B = Super A

    • Together they’re stronger than alone.

  1. Antagonistic (Bad Combo)

    • One drug blocks or reduces the effect of the other.

    • 🔹 Example: A + B = Weaker result

    • This can happen when you mix:

      • A bactericidal drug (like penicillin)

      • With a bacteriostatic drug (like tetracycline)

⚠ Reminder:

Not all antibiotic combos are safe or smart—some can cancel each other out or cause side effects.

Slide 8: General Adverse Reactions to Antibacterials

When using antibiotics, watch for these 3 big problems:

1. Allergic Reactions

  • Signs:

    • Rash

    • Itching (pruritus)

    • Hives

    • ⚠ Anaphylactic shock (life-threatening reaction)

      • Trouble breathing

      • Drop in blood pressure

      • Emergency! Use epinephrine immediately

2. Superinfections

  • Happen when normal good bacteria are wiped out by antibiotics

  • Bad bacteria or yeast take over

  • Common sites:

    • Mouth (thrush)

    • Skin

    • Intestines

    • Genitourinary tract (yeast infections, UTIs)

  • Look for: White patches, new discharge, itching

3. Organ Toxicity

  • Some antibiotics can damage organs:

    • Ear (ototoxicity) → hearing loss, ringing

    • Liver (hepatotoxicity) → monitor liver labs: ALT, AST

    • Kidneys (nephrotoxicity) → watch urine output and kidney labs (BUN, creatinine)

Summary:

Always monitor for allergic reactions, superinfections, and organ damage—especially in long-term or high-dose antibiotic therapy.

Slide 9: Antibacterial Spectrum

Antibiotics can be narrow-spectrum or broad-spectrum—here’s what that means:

Narrow-Spectrum Antibiotics

  • Target a specific group of bacteria.

  • Usually effective against gram-positive bacteria.

  • 🔹 Examples:

    • Penicillin

    • Erythromycin

  • Used when we know the exact bacteria causing the infection.

🌐 Broad-Spectrum Antibiotics

  • Work against both gram-positive and gram-negative bacteria.

  • Good choice when the exact bacteria hasn’t been identified yet.

  • 🔹 Examples:

    • Tetracycline

    • Cephalosporins

  • Often used before culture & sensitivity (C&S) results come back.

Summary:

  • Narrow-spectrum = targeted strike 🎯

  • Broad-spectrum = wide coverage 🌍 (but can wipe out good bacteria too)

Slide 10: What is Penicillin?

Penicillin was the first antibiotic ever discovered—and it’s still widely used today!

Penicillin Facts:

  • Made from a mold (genus Penicillium).

  • Has a beta-lactam ring —this part kills bacteria by:

    • Interrupting cell wall synthesis (bacteria can’t build a strong wall = they die).

  • Can be:

    • Bactericidal (kills bacteria)

    • OR Bacteriostatic (slows down bacteria growth)—depends on the dose and type.

Summary:

Penicillin = 💥 Breaks bacteria’s walls so they pop and die.
It’s a beta-lactam antibiotic, and it changed the world of medicine!

Slide 11: Penicillins – 4 Types to Know

1. Narrow-Spectrum Penicillin

  • Works mostly on gram-positive bacteria.

  • Used for:

    • Anthrax, diphtheria

    • Skin & respiratory infections

    • STIs, scarlet fever, meningitis, otitis media

  • 🔹 Examples: Penicillin G, Penicillin V

🌐 2. Broad-Spectrum Penicillin

  • Works on both gram-positive and gram-negative.

  • Used for:

    • UTIs, respiratory, skin, intraabdominal, and gynecologic infections

  • 🔹 Examples: Amoxicillin, Ampicillin

3. Penicillinase-Resistant Penicillin

  • Works against bacteria that produce penicillinase (an enzyme that destroys penicillin).

  • Used for:

    • Staph infections (Staphylococcus aureus), endocarditis, meningitis, bacteremia

  • 🔹 Examples: Dicloxacillin, Oxacillin

4. Extended-Spectrum Penicillin

  • Very strong against gram-negative bacteria.

  • Used for:

    • Pseudomonas, Proteus, Klebsiella, and other serious infections.

  • 🔹 Example: Piperacillin-tazobactam

Summary:

Each type of penicillin is designed to fight specific kinds of bacteria. Some are stronger, broader, or better for resistant strains.

Slide 12: What Are Beta-Lactamase Inhibitors?

Some bacteria produce an enzyme called beta-lactamase (aka penicillinase) that breaks down penicillin—making it useless.

💡 Solution?

Add a beta-lactamase inhibitor to protect the penicillin.

How It Works:

  • The inhibitor blocks the enzyme so the penicillin can still work.

  • This combo gives the drug extra power against resistant bacteria.

🔹 Common Combo Medications:

Penicillin

+

Beta-Lactamase Inhibitor

Amoxicillin

+

Clavulanic acid → Augmentin

Piperacillin

+

Tazobactam → Zosyn

Ampicillin

+

Sulbactam → Unasyn

Summary:

Beta-lactamase inhibitors = bodyguards 🛡 for penicillin, helping it survive attacks from resistant bacteria.

Slide 13: What to Watch for with Penicillin

Side Effects / Adverse Reactions:

  1. Allergic reactions

    • Rash, itching, hives

    • ⚠ Anaphylaxis = life-threatening → treat with epinephrine

  2. GI issues

    • Nausea, vomiting, diarrhea, abdominal pain

  3. Superinfections

    • Yeast infections (mouth, skin, genitals)

  4. Blood issues (with long-term use)

    • Anemia, bleeding

  5. Liver/kidney toxicity (rare but possible)

Nursing Interventions:

  • Check for allergies to penicillin or cephalosporins before giving!

  • Monitor for signs of allergic reaction, especially on first dose

  • Teach patients to:

    • Take the full prescription (don’t stop early)

    • Take with food to reduce stomach upset (if allowed)

    • Use back-up birth control (penicillin may weaken oral contraceptives)

  • Watch for signs of:

    • Superinfection (yeast, diarrhea, mouth sores)

    • Liver or kidney issues (check labs)

Slide 14: Cephalosporins – What Are They?

  • Beta-lactam antibiotics like penicillins

  • Bactericidal → They kill bacteria by breaking the cell wall

  • Divided into 5 generations (each one stronger or broader)

🔍 Uses:

  • Respiratory infections

  • Urinary tract infections (UTIs)

  • Skin infections

  • Bone & joint infections

  • Surgical prophylaxis (to prevent infection)

⚠ Important!

  • People allergic to penicillin may also react to cephalosporins (because they’re chemically similar)

Summary:

Cephalosporins are versatile, often used when penicillin doesn’t work or isn’t tolerated.
They get stronger with each generation—and can treat more types of infections.

Cephalosporins – 5 Generations Overview

Each generation fights more bacteria and can better resist beta-lactamase.

1st Generation

  • Great for gram-positive bacteria.

  • Used for skin, soft tissue, and surgical prophylaxis.

  • 🔹 Example: Cefazolin

2nd Generation

  • Works on gram-positive and some gram-negative.

  • Used for respiratory, ear, skin, and abdominal infections.

  • 🔹 Example: Cefaclor

3rd Generation

  • Stronger against gram-negative bacteria.

  • Crosses the blood-brain barrier → used for meningitis.

  • 🔹 Example: Ceftriaxone (Rocephin)

🔵 4th Generation

  • Broad-spectrum: Strong against gram-positive AND gram-negative.

  • More resistant to beta-lactamase.

  • 🔹 Example: Cefepime

5th Generation

  • Effective against MRSA (a tough, resistant bacteria).

  • 🔹 Example: Ceftaroline

💢 Adverse Reactions:

  • Allergic reactions (similar to penicillin)

  • GI upset: Nausea, vomiting, diarrhea

  • Risk of superinfections

  • Possible nephrotoxicity (watch kidney labs)

  • Drug interactions: Alcohol → causes severe vomiting, headache, drop in BP

Slide 16: Macrolides – What You Need to Know

What Are Macrolides?

  • Broad-spectrum antibiotics

  • Bacteriostatic in low doses

  • Bactericidal in higher doses

🔍 Uses:

  • Respiratory infections (like pneumonia, bronchitis)

  • Skin infections

  • Ear infections

  • STIs

  • Mycoplasma infections (no cell wall)

🔹 Common Macrolides:

  • Azithromycin (Zithromax)

  • Clarithromycin (Biaxin)

  • Erythromycin (the oldest one)

⚠ Side Effects:

  • GI distress (nausea, diarrhea, abdominal cramps)

  • Liver toxicity (especially with long use)

  • Ototoxicity (hearing issues at high doses)

  • QT prolongation (heart rhythm changes – watch ECG!)

Nursing Interventions:

  • Give with food if GI upset occurs (unless contraindicated)

  • Monitor liver function tests (AST, ALT)

  • Avoid use with other QT-prolonging meds

  • Encourage full course of antibiotics

Summary:

Macrolides are versatile and widely used—but monitor for GI, liver, and heart effects.