Antimicrobial Agents Flashcards
What is the difference between bacteriostatic and bacteriocidal? Which one is better for perioperative ABX?
Bacteriostatic = stops bacteria from growing and reproducing
disrupts protein formation
disrupts DNA synthesis-> prevents reproduction
Bacteriocidal = kills the bacteria
better choice for perioperative ABX
better choice for the critically ill and immunocompromised
Disrupts cell wall or cell membrane
Give two reasons for giving Antimicrobial agents
- Prevent surgical site infection (SSI)
2. Treat known/ suspected infection
What is MIC (minimum inhibitory concentration)?
the minimum serum concentration that is needed to be effective. Want to avoid under dosing bc it could promote bacterial resistance. Exception- hepatic and renal dysfunction
What is the difference between narrow spectrum and braod spectrum ABX?
A broad-spectrum antibiotic
-acts against a wide range of disease-causing bacteria
-acts against both Gram-(+) & Gram-(-) bacteria,
-in contrast to a narrow-spec which is effective against specific families of bacteria.
Narrow Spectum
-only effective against agents of concern
-minimize effects on other “normal” flora (broad spectrum)
When are broad spectrum ABXs used?
- Before the formal ID of the causative bacteria, when there is a wide range of possible illnesses and a potentially serious illness would result if treatment is delayed.
- This occurs, for example, in meningitis, where the patient can become fatally ill within hours if B.S. ABX aren’t started
- For drug resistant bacteria that do not respond to other, more narrow-spectrum antibiotics.
- In the case of superinfections, where there are multiple types of bacteria causing illness, thus warranting either a broad-spectrum antibiotic or combination antibiotic therapy.
- Empirically (i.e., based on the experience of the practitioner)
What is the difference between aerobic bacteria and anaerobic bacteria? Where are each type found in/on the body?
Aerobic = able to use O2, gets energy from breaking down food
-skin (gram +)
-gut (gram -)
Anaerobic = can sustain itself w/o O2, can’t break down food
-intestinal
-GYN
What is the difference between Gram (+) and Gram (-) bacteria?
Gram (+) - thinner cell wall - more easily penetrated by ABX Gram (-) - more resilient cell wall - less susceptible to most ABX
Identify the following aerobe as gram(+) or gram(-) and identify where it is found:
strep
gram +, skin
Identify the following aerobe as gram(+) or gram(-) and identify where it is found:
staph
gram +, skin
Identify the following aerobe as gram(+) or gram(-) and identify where it is found:
enterobacilli
gram -, gut
Identify the following aerobe as gram(+) or gram(-) and identify where it is found:
E. coli
gram -, gut
What are the three ways to classify ABXs?
Bacteriostatic vs Bacteriocidal
Narrow Spectrum vs Broad Spectrum
Gram(-) vs Gram(+)
What are the 3 types of ABX cellular targets? (sites of action)
- cell wall
- protein synthesis (ribosomes)
- nucleic acid synthesis
- What type/class of ABXs most commonly cause allergic rxns?
- What are 4 symptoms of this immune-related rxn?
- Will a test dose trigger an allergic rxn?
- beta-lactams and derivatives
- rash, pruritus, bronchospasm, anaphylaxis
- yes
After administration of vancomycin, your patient displays the following symptoms: rash, pruritus, bronchospasm and flushing. Is your patient having an allergic reaction?
Not necessarily. They can be having a non-immune mediated histamine release. Certain drugs can cause release of histamine in a dose- and/or rate-dependent fashion. This used to be called anaphylactoid, but this term is not really used much anymore. This reaction can be just as severe as immune-mediated anaphylaxis.
Cefazolin is the preferred ABX is which 4 types of surgeries?
- Cardiac or vascular
- Neuro
- Ortho: TKA/THA
- General (hernia repair, breasts)
For a given procedure, cefazolin is the preferred ABX; however, the patient has a B-lactam allergy. What ABX should be used instead? What if the patient had a known history of MRSA?
B-lactam allergy - Clindamycin or vancomycin
MRSA - vancomycin
What types of surgeries is cefoxitin the preferred ABX? What if the pt has a B-lactam allergy?
- Colon
- General (gastroduodenal, hepatobiliary)
- Gynecological (hysterectomy, c-section)
B-lactam allergy -> gentamicin + metronidazole OR
Ciprofloxacin + metronidazole
When are ABXs not indicated?
not indicated for elective “clean” surgical procedures
Name 4 ABX groups that target the cell wall/membrane.
PCNs (B-lactam)
Cephalosporins (B-lactam)
Vancomycin
Daptomycin
What are beta lactamase inhibitors? Name 3 examples.
They overcome resistance to PCNs. Resistance is caused by inactivation by beta lactamases.
Unasyn, Zosyn, Aumentin
Name 3 common Cephalosporins.
Cefazolin, Cefoxitin, Ceftriaxone
What are cephalosporins excellent coverage for?
skin flora
What are cephalosporins commonly used for?
cardiovascular, orthopedic, biliary, pelvic, intraabdominal surgry
