Infectious Diseases - Meds

Question 0

What would you use penicillin for?

Answer 0

Strep bacteria, such as Strep. pneumonia (also responds to amoxillin (ORAL - good for all upper resp stuff) and ceftriaxone), Strep. pyogenes, Strep. viridans (also ceftriaxone).

Strep pyogenes: strep throat: penicillin

Strep viridans: heart - stole heart - ceft-reaction or penicillin

Strep pneumonia: penicillin OR ceftriaxone OR amoxicilillin (amo is good for all upper resp stuff)

Question 1

What are the names of oral and IV penicillins?

Answer 1

Oral: Penicillin V

IV or IM: Penicillin G

NOTICE OPPOSITE: ORAL IS V

Beta-lactamases in some bacteria (staph, gram -ves) can cleave penicillins (cut one of the two rings)

Question 2

What is an AMP-GENT combo?

Answer 2

AMP-GENT combo = ampicillin + gentamycin (+ and -), good for serious UTIs etc - could be gram - enteric bacteria or enterococcus => coverage for both *Amp is NOT beta lactase resistant, will get cleaved!*

**Amoxicillin/ampicillin HELPSS kill enterococci AND enterobacter. **

**H. Influenza, E.Coli, Listeria, Proteus Mirabilis, Salmonella, Shigella. **

**GENTAMYCIN helps kill ENTEROBACTER, so amoxicillin and getnamycin often used together = AMP-GENT combo, since serious infections, say UTIs could be either enterococcus (faecalis) or enterobacter (like E.coli). **

Question 3

What penicillin-like drug can be given for enterococci and good spectrum of Gram -ves?

Answer 3

Amoxicillin (PO) and Ampicillin (IV)

Think amOxicillin with O for PO ampIcillin with I for IV AMPicillins are AMPed up penicillins - better spectrum. HELPSS kill enterococci. For enterococci, give amPIcillins only (IV), b/c they need stronger stuff.

EnteroBACTER: H.Influenza E.Coli Listeria monocytogenes Proteus mirabilis Salmonella Shigella Enterococci, like Enterococcus faecalis

One of the drugs that works against enterococci AND enterobacter!

Question 4

What are penicillinase-resistant penicillins?

Answer 4

great against beta-lactamases (bacterial enzymes that cut through beta-lactam rings in “normal penicillin”). Ex. Staph aureus needs cloxacillin (**staff watch clocks) **

Question 5

When would you prescribe Penicillin V

Answer 5

Strep infections, especially Strep. pharyngitis (Group A)

Question 6

What are examples of penicillinase-resistant Penicillins in IV form?

Answer 6

IV: methicillin (no longer in production), nafcillin, oxacillin “ I MET a eNAF OXes to not like beef”

Question 7

Name a few penicillinase-resistant PO Penicillins?

Answer 7

PO: think Staph like to watch clox so they can go home

CLOXacillin diCLOXacillin

Not good against gram -ves because bulky

Great for Staph/Strep coverage - infected skin wounds (cellulitis, impetigo, etc) when it could be either Staph or Strep.

Question 8

Name Anti-Pseudomonal Penicillins?

Answer 8

Think of Sherlock Holmes trying to catch thieves who use Pseudonyms. He is driving a CAR, while smoking a PIPE, with a bag of CARB-rich British cookies in the back seat, and a bomb TICking in his trunk.

Ticarcillin

Carbenecillin

Piperacillin

Question 9

Are anti-Pseudomonal drugs sensitive to penicillinases (beta lactamases)?

Answer 9

Yes, so most Staph aureus are resistant to them

Question 10

Name a few beta-lactamase inhibitors

Answer 10

Clavulanic acid (think clavicle)

Sulbactam (think SULtan BACk from IsTAMbul)

Tazobactam (think Tazo tea)

Usually given in combo with penicillins to create beta-lactamase resistant combos

Question 11

What are some antibiotic combos that are frequently used for penicillinase-resistant bacteria?

Answer 11

Amoxicillin + clavulanic acid

Ticarcillin + clavulanic acid

Ampicillin + sulbactam

Piperacillin + tazobactam

Broad-coaverage against beta lactamase gram+ (Staph aureus), gram - (H. influenza), anaerobes.

Question 13

What are Cephalosporins?

Answer 13

Cephalosporins = class of antibacterials, cell wall inhibitors, over 20 different kinds - more resistant to beta lactamases (but susceptible to cephalosporinases) - wider spectrum of activity because of R group

Remember, ENTEROCOCCI (group D Strep - UTI, nosocomial, subacute endocarditis, biliary infections) are resistant to cephalosporins and can colonize when ceph’s are administered

Remember that MRSA are also resistant to cephalosporins - treat them with vancomycin

Question 13

What organisms are resistant to Cephalosporins ?

Answer 13

MRSA is resistant to all cephalosporins Enterococci (incl. Strep. faecalis) are resistant to cephalosporins.

Question 14

What are the general differences between different generations of Cephalosporins?

Answer 14

older generations are more effective against gram +, newer generations are less effective against gram -ves Would treat Staph and Strep with first generation

enterococci faecalis (strep D) (UTI, nosocomial esp after cephalosporins, subacute endocarditis) and MRSA are resistant to cephalosporins

Question 15

Name first generation cephalosporins? What do they do?

Answer 15

usually have PH in the name (“need to have PH.D to know them!). Orals: CePHalothin CePHapirin CePHradine CePHalexin

Alternative to penicillin for staph and strep infections when penicillins cannot be tolerated. Good before surgery as skin infection prevention.

1st generation are grood fro gram +ves

Question 16

Name second generation cephalosporins?

Answer 16

CeFAmandole

CeFAclor

CeFURoxime - > on top 10 list for H. influenza

H. Influenza = How I CEFted (sifted) ROX (rocks)

awesome for upper resp infections - good gram -ve coverage

CeFOXitin

CefoTEtan

Covers gram -ves.

Cefuroxime covers against Strep. pneumoniae and H. influenzae - awesome for community-acquired pneumonia when you know it is gram -ve but don’t know organism

Cefuroxime is good for sinusitis and otitis media, caused by H. influenza or Moraxella catarrhalis. cefotetan, cefoxitin and cefmetazole have anaerobic coverage (ex. Bacteroides fragilis) - great for abdo surgeries (often contamination by anaerobes from GI tract), or abdo infections.

Question 17

Name third generation cephalosporins? When are they used?

Answer 17

CEFTriaxone (big one! IV) <- top 10

Strep pneumonia, E.Coli, gonorrhea

CEFTazidime

CEFixime PO - good for skin infections

Cefdinir, Cefpodoxime, Cefditoren, Cefotaxime Ceftizoxime

CEFTriaxone (theft reaction!) is a drug of choice for meningitis-causing bacteria because of good CSF penetration.

CEFOtaxime is a drug of choice for meningitis in neonates/kids (ceftriaxon can interfere with bilirubin metabolism)

CEFTriaxone is also used to treat gonorrhea (IM) In-patient community acquired pneumonias, meningitis, pyelonephritis (UTI that involves kidneys).

Question 18

Name fourth generation cephalosporins? When is it used?

Answer 18

Cefepime same as 3rd generation, but with coverage against Pseudomonas aeruginosa. Ceftazidime(3rd gen) also has Pseudomonas coverage.

Question 19

Name fifth generation cephalosporins? (not in notes)

Answer 19

Ceftaroline - activity against MRSA

Question 20

Do allergies to cephalosporins exist?

Answer 20

10% of patients with penicillin allergies will have cephalosporin reactions. As with penicillins, rash usually appears weeks later.

Question 21

Give examples of carbapenems?

Answer 21

Imipenem (I’m a pen), meropenem, doripenem, ertapenem.

Question 22

What are carbapenems?

Answer 22

Carbapenems = Antibiotics, broad coverage - great for bacterial resistance = reserved for bad stuff!

** Resistant to beta-lactamases.** remember them as penicillin like drugs since they have PEN inside. reserved for strong strong stuff - like polymicrobial infections or multidrug resistant organism but do not treat MRSA! careful I”M a pen = imipenems can cause seizures - think has “I’m” - thinking pen -> seizures. meropenem - no seizures, better for things like post-trauma and neurosurgical meningitis = “myr” = peace - brain at peace from treatment from meningitis and from not seizing.

Question 23

What class does imipenem belong to? When is it used?

Answer 23

imipenem = cell wall inhibitor = carbapenem, broadest antibacterial activity of any antibiotic known to man - kills gram+, gram-, anaerobes (even Pseudo). Very small, so can pass through gram - porins. does not kill MRSA and Mycoplasma (no cell wall)

Question 24

How does penicillin work?

Answer 24

1. penicillins penetrate outer cell layer
2. gets into inner layer that has transpeptidases which build cell walls
3. penicillin’s b-lactam ring binds to and inhibits competitively the transpeptidase enzyme (b/c competitive, can overcome intermediate resistance with higher drug dose).
4. cell wall synthesis stopped
5. holes in cell wall, bacteria die (bactericidal)

bacteria can create enzymes that break down pencillins - that is why you hear about penicillinase-resistant penicillin = beta lactamase enzymes of bacteria cleave penciillin.

Question 25

What is amoxicillin and ampicillin?

Answer 25

Think of amoxicillin (PO) and ampicillin (IV) as AMPed up penicillins.

Imagine amp (stereo amp) in GI tract - this is to help you remember that ampicillin is also good for enterococcus faecalis (Group D strep, which normally colonizes GI, but also causes UTIs, many nosocomial infections (esp. after cephalosporins), etc). Enterococcus needs ampIcillin (IV), b/c it is opportunistic and needs strong stuff.

BUT AMOXICILLINS CANNOT RESIST BETA LACTAMASES, so need some extra stuff, like gentamicyn for added oumph.

**Amoxicillin/ampicillin HELPSS kill enterococci AND enterobacter. **

H. Influenza, E.Coli, Listeria, Proteus Mirabilis, Salmonella, Shigella.

GENTAMYCIN helps kill ENTEROBACTER, so amoxicillin and getnamycin often used together = AMP-GENT combo, since serious infections, say UTIs could be either enterococcus (faecalis) or enterobacter (like E.coli).

Question 26

What’s the deal with penicillin allergies?

Answer 26

• less than 10% of penicillin allergy people have true IgE mediated allergic reation (hives, anaphylaxis, etc)
• anaphylaxis risk with PO penicilin = 0.01-0.02%
  
  • mortality 0.0015-0.02%
• anaphylaxis NOT genetic
• 50% of patients loose sensitivity to penicillin in 5 years
• 80% of patients loose sensitivity to penicillin in 8 years
• if distant reaction (> 10 yrs) could have a graded penicillin challenge
• ampicillin and cephalexin have similar side chains so try not to give
• 1% risk with cephalosporins with reported penicillin allergy, 2.5% risk with confirmed pecicillin allergy (less likely to have allergy if 3rd or 4th generation cephalosporin, like ceftriaxone (IV), cefixime (PO), or cefepime (IV-4th)
  *

Question 27

How does Vancomycin work? What antibiotic class is it?

Answer 27

Vancomycin is of glycopeptide class PO or IV

It works by inhibiting cell wall synthesis by a mechanism different from penicillins (beta lactams) - it gets involved in an earlier phase.

glycopeptides attach to the end of peptidoglycan precursor units (short D-alanyl-D-alanine = d-ala-d-ala termini) - this step is called transglycosylation. precursor is then not released from the carrier and peptidoglycan synthesis stops.

Vancomycin resistant enterococci become resistant by not allowing the drug to bind to D-ala-D-ala.

MRSA: good coverage

give Vancomycin PO for C.difficile infections

**give Vanco for enterococci, pecicillin-resistant Strep, coagulase -ve staph. **

gram +ves: good coverage

Think D-ala-D-ala = singing in Vancouver

Side effects:

Flushing: when vancomycin is administered quickly, the blood pressure can fall because of histamine release. Therefore vancomycin must be administered slowly (usually over 1 hour). The flushing caused by histamine release has been called red man syndrome and is not an allergy but a predictable response to rapidly administered vanco.

Ototoxicity: very rare, unless vancomycin is administered with another ototoxic agent, such as aminoglycosides (gentamicin)

Nephrotoxicity: is rare (6-7%), unless administered with another nephrotoxic agent such as aminoglycoside (gentamicin)

Neutropenia: low WBC count possible.

If resistant to Vancomycin, can treat with daptomycin - similar mechanism of action (good for VRE).

Question 28

How does gentamicin/tobramycin work? What class are they?

Answer 28

gentamicin is of aminoglycosides class. also tobramycin, streptomycin. they are antibiotics derived from bacteria and inhibit protein synthesis by irreversibly binding to small ribosomal subunit (30 S ).

**Gentamicin is really good against gram -ve bacteria, and is bacteriostatic. **

Poorly absorbed in the GI and so not administered orally, but do collect around proximal tubule in the kidney and cause nephrotoxicity of the drug! Excreted by kidney, so have to watch for renal dysfunction and change dosage accordingly: monitor GFR.

Side effects: ototoxicity (10%) thought to damage hair cells in inner ear.

nephrotoicity (up to 10%) - watch creatinine, if rises stop! usually nephrotoxicity is mild and can be reversed.

REMEMBER AMP -GENT

**Gentamicin was great for gram -ves, like those causing UTIs, pseudomonas, etc so often administered in synergy with ampicillin to get gram + and gram -ves out. **

10 vacteria: enterococcus faecalis = amp+gent, also used for E.coli.

Question 29

What is the mechanism of action of clindamycin?

Answer 29

a**ntibiotic that iinhibit the 23S bacterial ribosome. blocking tthe transfer of the new amino acid onto the growing chain. because of its action on protein synthesis, has thought to be good in toxin-producing infections - ex. GAStrep, like in necrotizing fasciitis. **

Good for strep

S. aureus

MRSA

anaerobes

not good for gram negative organism

predisposes to C.diff - the worst drug to predispose to C.diff