Abx Flashcards
4 main Gram Positive Bugs
_Staphylococcus (Staph)
Streptococcus (Strep)
Enteroccous
C. difficile (Clostridioides difficile)
Gram-Negative Bugs
Just about everything else!
Neisseria gonorrhoeae
Neisseria meningitidis
E. coli, Shigella, Campylobacter, Salmonella
Pasteurella
Rickettsia, Borrelia
Proteus, Pseudomonas, Legionella, others
Gram-Positive Bug — Staphylococcus
Staphylococcus aureus (skin)
Methicillin-susceptible Staphylococcus aureus (MSSA) (skin)
Methicillin-resistant Staphylococcus aureus (MRSA) (skin)
* Staph saprophyticus (UTI, vagina)
* Staph epidermis (skin)
Gram-Positive Bug — Streptococcus
- Strep pyogenes (throat)
- Strep pneumoniae (lungs)
- Strep viridans (dental abscess, endocarditis)
- Strep agalactiae (Group B Strep)
Gram-Positive Bug — Enterococcus
- Enterococcus faecalis (urinary tract)
- Enterococcus faecium (urinary tract)
Other Gram-Positive Bugs
- Clostridium difficile
- Listeria monocytogenes (listeriosis): outbreaks in food or ice cream!
- Propionibacterium acne (acne)
- Corynebacterium diphtheriae (diphtheria)
- Clostridium botulinum (botulism)
- Clostridium tetani (tetanus)
- Bacillus anthracis (anthrax)
So, if a patient says, “I’m allergic to penicillin,” can you safely prescribe a cephalosporin?
Maybe … IF you are PCN allergic, you’re EITHER allergic to the pink pentagon OR the blue box
If you are allergic to the pink pentagon, can you safely take a cephalosporin?
Yes, cephalosporins do not have a pink pentagon
90-98% of PCN-allergic patients are allergic to the pink pentagon and can safely take cephalosporins!
If you are allergic to the blue box in PCN, can you safely take a cephalosporin?
No both have a blue box
- 2-10% of patients who are allergic to PCN are allergic to the blue box AND will also be allergic to cephalosporins
When NOT to prescribe PCN with rx of reaction?
Anaphylaxis or Hives
Hives = IgE-mediated, Type I reaction
- Will get worse with repeated exposure
What if pt w/ PCN reaction was morbilliform rash?
Ok to give cephalosporin
- Red raised flat, all over body – but pt can sleep and are not miserable
- Rash is macular or maculopapular, lesions are fixed, area expands over several days
- May itch
- More prevalent in children
- More common with aminopenicillins (amoxicillin and ampicillin)
- Usually T cell mediated
morbilliform rash
What happens when a patient who has mononucleosis is exposed to penicillin?
Don’t give mono pt a PCN drug. Can get morbilliform rash (aka. Morbilliform rash)
What is Beta-Lactamase?
An enzyme that smart bacteria learn how to produce
It destroys the beta-lactam ring on PCN and cephalosporins! And if you destroy the blue box … antibiotic won’t work!
Ampicillin, Amoxicillin, Penicillin G, Penicillin K Gram-Positive Organisms
- NOT Staphylococcus
Streptococcus Group A, B, C, G Enterococcus, Strep pneumoniae, Drug-resistant Strep pneumoniae (DRSP), C. botulinum (wound, not food)
Penicillin’s
Can amoxicillin really kill DRSP?
What dose for adults?
What dose for peds?
Yes amoxicillin can kill the drug resistant strep pneumonia
Adult- 1gram TID
Pedi- 90 mg/kg/ day (as long as it does not exceed adult dose)
Amoxicillin/Clavulanic acid (Augmentin)
Gram-Positive, Gram-Negative Organisms
Beta-lactamase, NOT MRSA
Streptococcus Group A, B, C, G, Enterococcus, Strep pneumoniae, DRSP, MSSA H. influenzae, M. catarrhalis, E. coli, Neisseria, C. diphtheria
Extended-Spectrum PENICILLINS
How would you know if a bug produced beta-lactamase?
If pt had Abx within the last 90 days and is sick again – you can suspect that the organism making them sick produces beta lactamase.
TMP-SMX (Bactrim, Septra) Gram-Negative Organisms
MRSA, E. coli ????
Staph: MSSA, MRSA, CA-MRSA, Not Strep, Not E. coli (USE IF COST IS AN ISSUE)
Sulfonamides
Doxycycline, Minocycline, Vibramycin Gram-Negative Organisms
Atypicals, MRSA
Minocycline is good choice for MSSA and community-acquired-MRSA (CA-MRSA) Doxy/Mino good choices for atypical pathogens and lower resp tract pathogens H. flu, E. coli, Legionella, Mycoplasma, Chlamydophila, Rickettsia (tick- and tickborne infections
Tetracyclines
1st- 3rd Cephalosporins bacteria coverage
First Generation= Gram +
Second Generation Gram + Gram -
Third Generation= Gram + Gram - Beta lactamase
Cephalexin (Keflex), Cefadroxil (Duricef) Gram-Positive Organisms
Staph: MSSA, Strep
Cephalosporins 1st Generation
Cefuroxime (Ceftin), Cefaclor (Ceclor), Cefprozil (Cefzil) Gram-Positive, Gram-Negative Organisms
Staph: MSSA, Streptococcus
H. flu, E. coli, Proteus mirabilis
Cephalosporins 2nd Generation
Ceftibuten (Cedax), Cefixime (Suprax) Weak Gram-Positive, Gram-Negative Organisms
Beta-Lactamase Producers
Strep groups NOT Staph H. flu, M. cat, E. coli, Klebsiella, Salmonella, Shigella
Cephalosporins 3rd Generation
