Give two reasons for giving Antimicrobial agents
- Prevent surgical site infection (SSI)
2. Treat known/ suspected infection
What is the difference between bacteriostatic and bacteriocidal? Which one is better for perioperative ABX?
Bacteriostatic = stops bacteria from growing & reproducing
- disrupts protein formation
- disrupts DNA synthesis-> prevents reproduction
Bacteriocidal = kills the bacteria
- better choice for perioperative ABX
- better choice for the critically ill & immunocompromised
- Disrupts cell wall or cell membrane
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, pruritis, bronchospasm, and 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-actam)
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
What do the later generations of cephalosporins have?
more gram-negative coverage (GI cases), more resistance to beta lactamases, and better penetration of BBB
What is the dosing for cephalosporins?
1 g every 3-4 hours up to max dose of 2g
In regards to the cross-reactivity with PCNs, when is it probably safe to give a pt with a PCN allergy a cephalosprin?
probably safe to give to pts with minor PCN allergy (fever, rash), reasonable to avoid in pts with anaphylaxis to PCN; controversial debate
Is anaphylaxis a common reaction to cephalosporins?
NO! it is rare
What does vancomycin inhibit?
cell wall synthesis
In what type of pt is vancomyosin commonly used instead of cephalosporin?
pts with Methicillin-resistant staphylococcus aureus (MRSA)
When would you want to be cautious in using vancomycin? What type of pt?
renal insufficiency- must modify dosing
When do you redose vancomyosin and what do you use oral dosing for?
every 12 hours; for C. difficile colitis
What are the adverse reactions to Vancomyosin?
fever/chills, irritation; ototoxcity/nephrotoxicity (rare)red man syndrome
What is red-man syndrome caused from and how can you prevent it?
due to non-immune mediated histamine release with fast infusion; infuse over 1 hour
What is daptomycin good for?
vacomycin-resistant bacteria
How do you give daptomycin?
give as a “slow bolus”
Name the four protein synthesis/ribosomal agents
Tetracyclines (doxycycline), macrolides (Erythromycin), clindamycin, aminoglycosides (Gentamycin)
Tetracyclines, Macrolides, clindamycin, and aminoglycosides all inhibit _______ and bind to _________.
Protein synthesis; ribosome
What ion do tetracyclines bind to?
Ca (teeth and bones in children)
Tetracyclines are used in these certain procedures because they cross what?
D&Cs, they crossed the placenta
What antibiotic is characterized by the following are adverse effects?
GI upset- local irritation
bone/ tooth deformation/ inhibition/discoloration
sunlight sensitivity, dizziness, N/V
neuromuscular blockade
Tetracyclines (Doxycycline)
The following adverse effects are caused by what protein synthesis/ribosomal agent:
GI upset, partially due to increase GI motility,
fever, rash, esoinophilia
inhibit CYP450–> increased drug concentrations (prolonged effects of midazolam, alfentanil)
Macrolides (Erythromycin)
Which protein synthesis/ribosomal agent is a common alternative to PCN/cephalosporins?
clindamycin
What is the dose of clindamycin?
600-900 mg IV every 6 hours
What are the adverse effects of clindamycin?
GI upse, rashes, C. difficile, histamine release with quick administration, cause/potentiate neuromuscular blockade
Cell-wall agents, Nafcillin and vancomycin, are commonly used together with which protein synthesis, ribosomal agent?
aminoglycosides- gentamycin
What are the two different doses aminoglycosides- gentamycin?
low dose: 80 mg IV;
high dose: 5 mg/kg IV (max 400 mg)
redose every 8 hours
What are the two major adverse effects of gentamycin?
ototoxicity (irreversible) and nephrotoxicity (mild)- give slowly to keep serum levels low
What effect on the body can gentamycin have at high doses? How can you treat it?
neuromuscular blockade- tx Ca gluconate, neostigmine
What are the two other names for Bactrim and what pathway does it interfere with?
Trimethoprim, sulfamethoxazole; folic acid pathway- hits two steps in conversion of PABA–> THF
What rare syndrome can be caused by Batrim?
stevens-johnson sx
What is bactrim necessary for?
purine synthesis–> DNA
What are the adverse reactions of Bactrim?
fever, rash, photosenstitivity, N/V/ diarrhea
What antimicrobial agent is a DNA gyrase inhibitor, used frequently in GU cases, you give it over an hour (per package), may cause N/V and diarrhea, tendinitis and arthropathy (But rarely)
Fluoroquinolones- ciprofloxacin
Which antimicrobial agent is an anti-protozoal, bactericidal that disrupts the electron transport, and is used in treatment for bacterial vaginitis/ trichomoniasis, C diff, abdominal infections, brain abscess, and has a disulfiram-like effect?
Metronidazole- Flagyl
T or F. The 4 Protein Synthesis/ Ribosomal Agents are bacteriostatic ABXs.
False. Tetracyclines, Erythromycin, and Clindamycin are bacteriostatic Aminoglycosides (Gentamycin) is bacteriocidal
T or F. Tetracyclines cause normal flora suppression -> overgrowth (bacterial, candidal).
TRUE
Which protein synthesis/ ribosomal agent causes C. Difficile?
Clindamycin
Which ABX is characterized by the following?
ototoxicity (irreversible) and nephrotoxicity (mild)- give slowly to keep serum levels low
Gentamycin
What ABX is characterized by the following:bacteriostatic - Hits 2 steps in the conversion of PABA->THF (folic acid pathway)
Bactrim
can pts who have sulfa allergies take Bactrim?
No
What ABX disrupts the electron transport chain?
Metronidazole (Flagyl)
Lis the 4 ABXs that cause C diff
PCNsCephalosporinsClindamycinMetronidazole (Flagyl)
List the 4 ABXs that are teratogenic
tetracyclines, trimethoprim, metronidazole, fluoroquinolones(TTMF - take that mother f’er)
Which 2 ABXs are associated with ototoxicity?
Aminoglycosides and vancomycin
What ABX is used to treat C diff?
Vancomycin
T or F. Vancomycin is used for C. Diff, MRSA, and in pts w/ B-lactam allergies but is not effective for VRE?
TRUE
T or F. GI upset is most common with Tetracyclines and Macrolides.
TRUE
T or F. Neuromuscular blockade is seen with aminoglyccosides (in high doses) and more often with tetracyclines.
TRUE
T or F. Most people are not allergic to the B-lactam rings, they are allergic to the side chains.
TRUE
