Antibiotics! Flashcards
What is selective toxicity?
Antibiotics are harmful to the microbe but harmless to the human host.
Antibiotic categories work by different ___________.
Mechanisms
What is bacteriocidal?
Drugs are directly lethal to bacteria at clinically achievable concentrations
What is bacteriostatic?
• Drugs can slow bacterial growth but do not cause cell death. Compromises the bacteria enough so the immune system can sweep in and save the day.
Name two kinds of antiobiotic use?
Prophylaxis and treatment
Name some examples of using antibiotics prophylactically:
THIS IS NOT ROUTINE! ◦ Used to prevent infection ◦ Pre-surgery ◦ Special populations: heart valves, rheumatic fever ◦ Immunosuppressed
Name examples of using antibiotics as treatment:
◦ Empiric therapy
◦ Based on identification of organism
When might using a bacteriostatic antibiotic not be helpful?
If someone is immunocompromised – HIV, organ transplant, chemo drugs. Immune system can’t kick in to kill the microorgs like it should.
When does the WHO say it is ok to use abx prophylactically with surgery?
Abx should be used to prevent infection before and during surgery but NOT after.
We should be giving _____________ abx ___ hours before incision, per the WHO.
Broad spectrum, 2
Some example of when we would use abx before and during sx?
Bowel sx, c-section, abdominal sx. Not minor surgeries.
If you see someone on abx post-sx, what is likely going on?
We are actively treating an infection.
What does empiric therapy mean?
Treating someone based on experience. Based on our best guess of what is causing the infection (ex: e coli causes most UTIs, will treat for it before getting culture).
What are three main ways we want to identify bacteria?
◦ Gram positive vs. gram negative
◦ Shape: bacilli, cocci, spirilla
◦ Ability to grow in relation to oxygen: aerobic vs. anaerobic
Ideally when should a C&S be taken?
BEFORE anti-infectives are started
What is the first action we would take in a lab to ID bacteria?
Gram stain
After we have done a gram stain, what will happen in the lab?
We will begin to grow it out on a petri dish (takes up to 48 hours).
What is it called when you are growing out the bacteria?
A culture
Why is it the best practice to get a sample of the bacteria before starting anti-infectives?
You risk killing off some of the microorgs, thus making it harder to ID what the problem bacteria might be.
What does PCR stand for?
Polymerase Chain Reaction
What is the benefit of a PCR test?
We can detect bacteria and viruses and very low titers
Name some gram + organisms:
Staphylococcus, streptococus, enterococus
Name some bad things caused by gram + bacteria:
carbuncles, furuncles, impetigo, group A hemolytic strep, necrotizing fascitis, MRSA, skin, pneumonia,
catheter infections
Name some gram - organisms:
GI tract: E.coli, Shigella, Salmonella, Klebsiella, Enterobacter, Serratia, Proteus, etc.
Name some bad things caused by gram - bacteria:
H. influenza, Neisseria (meningitis & gonorrhea), pseudomonas
Where would you find anaerobic bacteria and what is probably happening/what are you seeing when you find it?
Deep wounds, tissues, and internal organs
Abscess formation, tissue destruction, foul smelling pus
Name 3 examples of anaerobic bacteria:
C.diff, clostridium botulinum, MRSA, e. coli, clostridum tetani
Are anaerobic organisms are harder or easier to treat?
Harder. These are the bad guys!
Are anaerobic organisms more often:
Gram +
Gram -
Can be both
Can be both
Name two common treatments for anaerobic microorganisms.
Flagyl, Clindamycin
We have taken our sample to send out for C&S, what kind of antibiotics do we generally start with now?
Broad spectrum (effective against a wide variety of different microorganisms)
After we get our C&S back, what kid of antibiotic do we switch to?
Narrow spectrum (effective against only one or restricted group of microorganisms)
What is an example of a broad spectrum antibiotic?
Ciprofloxacin, Levofloxacin, Penicillin
What is an example of a narrow spectrum antibiotic?
Azithromycin, Clindamycin, Vancomycin
Why do we change from broad to narrow spectrum medications?
Decreases the risk of superinfections and antibiotic resistance.
What does MIC stand for?
Minimal Inhibitory Concentration
What does MIC mean?
Minimum Inhibitory Concentration. It is the lowest concentration of antibiotic that causes inhibition of bacteria growth.
Name 6 host considerations in antibiotic selection:
Allergy Ability to penetrate the site Immunocompromised patient Foreign hardware within the body Age Genetic Factors
What is something we need to look into when we are examining an allergy to a drug?
Is it really an allergy or a SE?
Name two issues that would cause a difficult in a drug penetrating the site?
Mengitis (need a drug that will cross the BBB), abscess (is walled off, need to be drained first often)
Some drugs that have a high rate of allergic rxns?
Sulfa drugs, penicillin, cephalosporins, erythromycin
What are some example of foreign hardware within the body and how it affects which antibiotic we choose:
Hip replacement, pacemakers.
Body attacks the foreign material – the phagocytes are busy fighting this
What do we think about when dosing infants?
They have a high level of toxicity
What do we think about when dosing children adolescents?
Certain drugs should not be used
What do we think about when dosing pregnant/lactating people?
Risk to mom and fetus
What are some drugs to avoid giving during pregnancy/lactation?
Gentamicin causes hearing loss; sulfonamides causes kernicterus in nursing newborns
What do we think about when dosing older people?
Heightened sensitivity to medications
What is a genetic factor we need to consider when dosing abx?
G6PD deficiency with the use of sulfonamides (more common in African American, Middle Eastern, and male patients)
How do we know the antibiotic is working?
Clinical/lab Response
◦ Reduction in signs/symptoms and fever
◦ Reduction in WBC
◦ Peak/trough levels–checking for toxicity
Why wouldn’t we recheck the C&S while the patient is still on antibiotics?
We could get a negative culture reading, which may or may not be a true reading.
With antibiotic resistance, it is the __________ that becomes resistant, not the _________.
Microbe, patient
Name some things abx DON’T work for:
Flu, colds, vomiting, MOST coughs, MOST ear infections, MOST sore throats, MOST diarrhea, MOST cystitis
Name some things abx DO work for:
Serious bacterial infections including: Pneumonia, UTIs, STIs like gonorrhea, sepsis, meningococcal meningitis
Name 4 resistant organisms:
◦ MDRO
◦ MRSA
◦ VRE
◦ ESBL
What dies MDRO stand for?
Multi Drug Resistant Orgs
What dies MRSA stand for?
Methicillin-resistant Staphylococcus aureus
What dies VRE stand for?
Vancomycin resistant enterococcus
What dies ESBL stand for?
Extended spectrum beta-lactamase
Name some ways we can help stop the spread of drug resistant orgs?
◦ Using PPE – isolation procautions
◦ Identifying patients with these resistant orgs
◦ Putting patients on the appropriate meds
What are some common SEs with antibiotics?
Superinfection (host flora killed off by antibiotic, strong bacteria takes over), nausea/vomiting/ diarrhea (GI distress)
Name a common antibiotic related super- / supra-infection SE?
Candidiasis in mouth, yeast infection
probiotics can help!
Name a common antibiotic related GI SE?
C diff (this is also a superinfection)
Name some common antibiotic related allergic reactions?
Rash, hives, difficulty breathing
What to do if suspect of allergy?
Assess before and monitor after administration
• If suspected-> STOP medication immediately, think about airway (secure airway)
• Call Rapid Response/ Code Cart
What is the most common antibiotic to result in Cdiff?
Clindamycin
If a patient is going to have an allergic rxn, when it the most likely time it will occur?
Within 30 minutes of administration or second + administration (although can happen with first administration – could have been exposed to abx through food sources)
How do tetracyclines work?
Inhibition of protein synthesis
What is the tetracycline prototype?
Tetracycline!
Name 3 other tetracyclines:
- demeclocycline
- doxycycline
- minocycline
What is a unique characteristic of tetracyclines?
Yellow-brown discoloration of teeth (do not rx children under 8 and during pregnancy)
Why is there a lot of resistance to tetracyclines?
Overuse in the 1950-60s. Now we just use for weird things (RMSF, typhus, cholera, Lyme disease, H.pylori, chlamydia, acne).
What happens if you tell someone to take tetracyclines with food to help their GI issues?
It will actually decrease absorption
What are some other SE of tetracyclines?
GI issues (n/v/d), superinfections (Cdiff, candidiasis), photosensitivity
How do tetracyclines interact with food?
DO NOT TAKE WITH Calcium, Iron, Mg, Al – they bind to the drug and decrease drug absorption by 50%.
What should we tell people taking tetracyclines to avoid?
Avoid antacids, anti-diarrheal, dairy products
When is the best time to take the tetracyclines re: drug-drug or drug-food interactions?
1 hour before or 2 hours after contraindicated food/drugs
How do macrolides work?
Inhibition of Protein Synthesis
What is the prototype for macrolides?
erythromycin (E-mycin)
What are some other examples of macrolides?
Clarithromycin (Biaxin)
Azithromycin (Z-pack)
What is a unique trait of erythromycin?
Affects the motility of the GI tract (motilin)- this can used to HELP pts with diabetic gastroparesis and also with passing feeding tubes
What is a cardiac-related SE of erythromycin?
QT prolongation and cardiac death!
What are some drug-drug interactions with erythromycin?
Any drug that works through CYP3A4 pathway should be avoided. (CCB, antifungals, HIV protease inhibitors)
Why is azithromycin/Z-pack unique and why is this good?
It has a long duration of action (long 1/2 life), so it is given in a short course. Rx for 3-4 days, works in body for a week. This helps with compliance.
Some other SE of erythromycin?
GI upset, superinfections
Toxic levels with erythromycin (ASK KNOWLTON)
theophylline, carbamazepine, warfarin
How is administration preferred?
Continuous infusions rather that intermittent dosing (this is unusual).
How does clindamycin work?
Inhibition of protein synthesis
What is the biggest risk with using clindamycin?
C diff-associated diarrhea. Can be fatal. Stop immediately if concern for this, put on contact precautions. No alcohol-based hand sani.
What are the symptoms of C diff-associated diarrhea?
Profuse, watery diarrhea, abdominal pain, fever, leukocytosis.
If you give clindamycin rapidly IV, what can happen?
Risk for cardiac arrest. Give slow.
How do aminoglycosides work?
By inhibiting protein synthesis, but specifically by producing abnormal proteins – are bacterialcidal. STRONGER.
What is our aminoglycoside prototype?
Gentamicin
Name 6 other aminoglycosides.
Tobramycin, Amikacin, Kanamycin, Neomycin, Paromycin, Steptomycin,
What are the two unusual adverse effects?
Ototoxicity and nephrotoxicity (just like vancomycin!)
Related to trough levels
What is often the first sign of vestibular toxicity/effects?
Headache
How common is nephrotoxicity with aminoglycosides? How should we monitor for this?
5-25%! Usually reversible though.
Monitor BUN & creatinine
What can ototoxicity with aminiglycosides affect?
Cochlea (tinnitus) and vestibular area
How do sulfonamides work?
Inhibition of folate synthesis
What is the sulfonamide prototype?
Trimethoprim/Sulfamethoxazole
What are some other names for Trimethoprim/Sulfamethoxazole?
TMP/SMX AKA: Bactrim, Cotrim, Septra, Co-trimoxazole
What is the TMP/SMX ratio?
Ratio 1:5. FIXED DOSE PRODUCT
When put together, Trimethoprim and Sulfamethoxazole have a/an _________________ effect.
Synergistic
SEs of TMP/SMX?
GI (N/V)
Rash (CONCERN FOR SJS, stop medication immediately)
Blood dyscrasias (abnormal or disordered, more common with DS)
Crystalluria- Pts should increase hydration
Photophobia – Pts need sun protection, will easily get burned
CNS effects
What are some blood dyscrasias that are seen as SEs of TMP/SMX?
- Hemolytic anemia (with G6PD deficiency)
- Bone marrow suppression (folks with alcohol use disorder and pregnant people more at risk for this)
Refresher: Who is more likely to have a G6PD deficiency?
More common in AA and ME males
TMP/SMX is taken in what population to treat ________________ prophylactically?
HIV positive patients, PCP pneumonia
Whra CNS effects can TMP/SMX have?
Headaches, depression, hallucinations
If we give TMP/SMX to a pregnant woman, what can happen to the baby?
Kernicterus risk (bilirubin build up, nephrotoxic) & birth defects.
Should not be used in pregnancy, breast-feeding or in children under the age of 2months (this is used for UTI tx – should get a preg test first?).
What are some drug-drug interactions with TMP/SMX?
Warfarin, Dilantin
is 68% protein bound
If patients say they have a sulfa allergy what else should they not take?
Thiazide diuretics, loop diuretics, sulfa-DM meds
other drugs in same category
TMP/SMX can also cause _________kalemia.
Hyper
Tell me a little bit about SJS?
Symptoms: Widespread lesions, fever, malaise
Mortality rate 25%
Often treated in burn unit
How do fluroquinolones work?
Disrupt DNA Replication/cell division
What is our fluroquinolone prototype?
Ciprofloxacin (Cipro)
Name some other fluroquinolones:
ofloxacin
moxifloxacin
levofloxacin
gemifloxacin
How are fluroquinolone given?
Oral or IV. BOTH ARE EQUAL IN BIOAVAILABILITY!
If giving cipro via IV how should it be pushed?
Over 60 minutes (SAME AS VANCOMYCIN)
What is a unique side effect of ciprofloxacin?
Tendon rupture!
High risk with elderly & people on steroids (Think: COPD patients with exasperation)
Watch for heel pain
Avoid in kids under 18
Name other SEs of ciprofloxacin:
CNS issues in elderly
Photosensitivity
Dysrhythmias if on anti-dysrhythmia agent
Superinfections (Candida & Cdiff)
What is the main drug-food interaction with cipro?
Interacts with Al, Mg, iron, zinc, Ca
Milk/dairy products
Give drug 6 hours after or 2 hours before these food/supplements.
What happens when cipro is taken with milk/dairy products?
Medication binds to Al, Mg, iron, zinc, Ca, reduces absorption by 90%!!!!
Name some drug-drug interactions with cipro
Sucralfate, theophylline, warfarin, tinidazole
How does metronidazole (Flagyl) work?
Inhibition of nucleic acid synthesis
What does metronidazole work best against?
Protozoa and anaerobic bacteria. Has NO action against aerobic bacteria.
How does metronidazole work against these anaerobic bacteria?
Is only taken up by anerobic orgs and then converted into an active form, then causes death.
When is metronidazole often prescribed?
C.difficile (PO)
GI and Pelvic surgery
How do you give vancomycin for treatment of c diff?
ONLY IN ORAL FORM. IV will not work.
How do you administer metronidazole via IV?
Infuse over 1 hour (Same as vanco, cipro)
What are some unusual SEs of metronidazole?
- NO alcohol (3 days) due to Disulfiram (antabuse )-like reaction ALTHOUGH THIS IS BEING DEBATED, research not supporting this.
- Urine may turn dark reddish-brown
- Metallic taste in mouth
