antibiotic_microbial background and resistance Flashcards
What are antimicrobials used for?
To treat infectious diseases by killing or suppressing microorganisms (bacteria, viruses, fungi).
What is an antibiotic?
A chemical produced by one microbe that can harm other microbes.
What is selective toxicity?
The ability of a drug to target and kill bacterial cells without harming human cells.
What are three ways antimicrobials achieve selective toxicity?
- Disrupt bacterial cell wall 2. Inhibit bacterial enzymes 3. Disrupt bacterial protein synthesis
What is the difference between bactericidal and bacteriostatic drugs?
Bactericidal kills bacteria, while bacteriostatic inhibits growth so the immune system can eliminate the infection.
What is a narrow-spectrum antibiotic?
An antibiotic that targets specific bacteria, reducing the impact on beneficial bacteria.
What is a broad-spectrum antibiotic?
An antibiotic that targets a wide range of bacteria, which increases the risk of secondary infections.
What are the mechanisms of action for antimicrobials?
- Inhibit cell wall synthesis 2. Disrupt cell membrane 3. Inhibit protein synthesis 4. Interfere with DNA/RNA synthesis 5. Act as antimetabolites 6. Inhibit viral enzymes
How are bacteria classified by staining?
- Gram-positive: Thick cell wall that retains violet stain (e.g., Staphylococcus, Streptococcus) - Gram-negative: Does not retain violet stain (e.g., Escherichia, Klebsiella, Pseudomonas)
What are the three shapes of bacteria?
- Bacilli - Rod-shaped 2. Cocci - Spherical 3. Spirilla - Spiral-shaped
What is the difference between aerobic and anaerobic bacteria?
- Aerobic: Require oxygen for growth - Anaerobic: Do not require oxygen for growth
What are the four basic mechanisms of acquired resistance?
- Decrease drug concentration at site of action (limit uptake or pump drug out) 2. Inactivate the drug (e.g., penicillinase) 3. Alter drug target molecules 4. Produce a drug antagonist
What is the difference between single-drug resistance and multi-drug resistance?
- Single-drug resistance: Caused by mutations - Multi-drug resistance: Caused by conjugation (DNA transfer between bacteria)
What are key strategies to prevent antimicrobial resistance?
- Vaccinations 2. Hand hygiene 3. Prevent infections when possible 4. Diagnose and treat infections properly 5. Use antimicrobials appropriately 6. Promote responsible prescribing 7. Reduce unnecessary antibiotic demand 8. Ensure adherence to prescribed regimens 9. Prevent transmission
What are nosocomial infections (HAIs)?
Infections acquired in healthcare settings, including UTIs, surgical site infections, pneumonia, and bloodstream infections.
What are common sources of HAIs?
- Patient flora 2. Invasive devices (e.g., catheters, central lines) 3. Medical personnel 4. Contaminated medical environments
What are examples of drug-resistant healthcare-associated infections?
- CAUTI (Catheter-Associated UTI) - VAP (Ventilator-Associated Pneumonia) - CLABSI (Central Line-Associated Bloodstream Infection) - SSI (Surgical Site Infection) - C. difficile (CDIFF) (Clostridioides difficile infection)
What is the role of normal host flora?
- Produce natural antibacterial substances 2. Break down toxic agents
What happens when antibiotics kill normal flora?
Pathogens have room to grow, leading to superinfections.
What is a superinfection?
A new infection that appears during treatment for a primary infection.
What are common signs and symptoms of a superinfection?
Diarrhea, bladder pain, dysuria, vaginal discharge.
Give two examples of organisms that cause superinfections.
Clostridium difficile, Candida albicans.
What is empiric therapy?
Treatment based on the most likely pathogen before culture results are available.
Why is it important to culture before starting antibiotic treatment?
To identify the organism and determine its drug sensitivity.
What are the steps in a Culture & Sensitivity (C&S) test?
- Obtain a specimen 2. Isolate and identify the pathogen in the lab 3. Expose the pathogen to different antibiotics
What host factors influence antibiotic selection?
- Host defenses – Strength of immune system 2. Infection site – Ability to reach site (e.g., cross blood-brain barrier) 3. Allergies 4. Blood flow to the area
When are prophylactic antimicrobials used?
To prevent infection rather than treat an existing one.
What surgeries require prophylactic antibiotics?
Cardiovascular, peripheral vascular, orthopedic, GI tract, hysterectomy, emergency C-sections.
Why do patients with prosthetic heart valves need antibiotics before medical or dental procedures?
To prevent bacterial endocarditis.
Who might receive antibiotics for immune suppression?
Patients with severe neutropenia, HIV/AIDS, chemotherapy recipients.
What are other indications for prophylactic antibiotics?
- Deep puncture wounds (e.g., dog bites, stepping on nails) 2. Preventing maternal-to-newborn transmission of infections 3. Healthcare workers after needlestick injuries 4. STI exposure 5. Recurrent UTIs
What are common misuses of antimicrobials?
- Treating viral infections 2. Treating fever of unknown origin (unless immunocompromised) 3. Incorrect dosage 4. Treating without bacteriologic information 5. Omitting surgical drainage when needed
Why shouldn’t antibiotics be used for viral upper respiratory infections?
Only 1 in 4000 people benefit, but many experience side effects like diarrhea, rash, or severe allergic reactions.
When is it acceptable to use antibiotics for a fever of unknown origin?
Only if the patient is severely immunocompromised.
Why might an infection require drainage instead of antibiotics?
If there’s an abscess (pus), draining it is often more effective than antibiotics alone.
What is the main function of bacterial cell walls?
To protect bacterial cells from the environment.
What is the primary material in bacterial cell walls?
Peptidoglycan.
What are penicillin-binding proteins (PBPs)?
Enzymes that help build bacterial cell walls.
How do penicillins (PCNs) and related antibiotics work?
They bind to PBPs and disrupt cell wall synthesis.
Why are penicillins more effective against gram-positive bacteria?
Gram-positive bacteria have a thicker peptidoglycan layer, making them more susceptible to cell wall-targeting antibiotics.
