Antibacterials

staph, strep, clostridium

what are 3 common gram+ bacteria?

pseudomonas, neisseria, haemophilus influenzae, syphilis, lyme, chlamydia

what are some common gram- bacteria?

empiric therapy

the use of antimicrobial drugs before the identification of the infecting microorganism & its drug susceptibility is determined

1. meibomian gland dysfunction

2. canaliculitis

3. dacryocystitis

4. dacryoadenitis

5. blepharitis

6. hordeolum

7. orbital cellulitis

what are some bacterial infections of the eye?

preseptal cellulitis

cellulitis in front of the orbital septum, give oral anti-bacterials to tx

orbital cellulitis

cellulitis behind the orbital septum, can access the brain, potentially fatal, must be immediately treated with IV anti-bacterials

selective toxicity

chemotherapeutics is based on the principle of _________

selective toxicity

bacteria have different features than human cells that are necessary for bacteria survival, antibacterial drugs take advantage of differences to inhibit or kill the bacteria without harming the host

bactericidal

• at standard doses, kills sensitive organisms so that the # of bacteria fall quickly after taking the drug

• more rapid response & clinical improvement

bacteriostatic

• at standard doses, inhibits growth of bacteria but does not kill them, # of bacteria remains constant

• requires a functioning immune system to eliminate the bacteria

• usually inhibit a metabolic rxn needed for growth, not necessary for survival

narrow spectrum drugs

active against a single species or limited group

extended spectrum drugs

intermediate range of activity, usually newer “generation” of a drug that adds more activity than an earlier generation

broad spectrum drugs

active against a wide range of pathogens, their use can drastically alter the bodies normal flora & result in superinfections

1. alteration of normal body flora (nausea, vomiting, diarrhea, yeast infections)

2. allergic hypersensitivities

3. interference w/ hormonal birth control

4. Stevens Johnson Syndrome

what are 4 SE of all antibiotics?

B-lactam ring covalently binds to & inhibits PBPs → inhibits cell wall synthesis

what is the MoA of B-lactam antibiotics (cephalosporins & penicillins)?

bactericidal

are B-lactam antibiotics bacteriostatic or bactericidal?

B-lactamase, penicillinase

some bacteria produce ______ or _____ which are enzymes that inactivate or degrade B-lactam drugs

penicillin G

• treats syphilis

• lots of resistance

• broken down by gastric acid & rapidly eliminated by the kidneys, must be given IV continuous infusion or IM with oral probenecid

probenecid

given with IM administration of penicillin G, competes for the same sites on kidney that penicillin binds to be excreted, slowing down the elimination of penicillin

penicillin V

• more stable

• can be given orally

• don’t really use in eyecare

dicloxacillin, nafcillin

what drugs are penicillinase resistant?

ampicillin, amoxicillin

what drugs are extended spectrum aminopenicillins?

amoxicillin + clavulanate, ampicillin + sulbactum

what drugs are extended spectrum & B-lactamase inhibitors?

clavulanate

B-lactamase inhibitor, blocks the enzyme so that active amoxicillin can access the bacteria & inhibit cell wall synthesis

no

does clavulanate have anti-bacterial properties by itself?

G+, G-, G+

early generations of cephalosporins work better on ____ bacteria, but later generations work better on ____ with less ____ coverage

cephalexin, cefazolin

what are the 1st gen cephalosporins?

cefaclor, cefuroxime

what are the 2nd gen cephalosporins?

ceftriaxone, ceftazidime

what are the 3rd gen cephalosporins?

cefepime

what are the 4th gen cephalosporins?

oral

dosage form of cephalexin

injection, Tp fortified eye drop

dosage form of cefazolin

oral

dosage form of cefaclor

injection, oral, Tp fortified eye drop

dosage form of cefuroxime

injection

dosage form of ceftriaxone

injection, Tp fortified eye drop

dosage form of ceftazidime

ceftazidime, cefepime

which cephalosporins are anti-pseudomonal?

injection

dosage form of cefepime

no

do cephalosporins work on MRSA?

first gen

penicillins & ______ cephalosporins exhibit allergic cross-sensitivity reactions

urticaria, angioedema, anaphylaxis

type 1 hypersensitivity rxn to PCN & cephalosporins

hemolytic anemia

type 2 hypersensitivity rxn to PCN & cephalosporins

interstitial nephritis, vasculitis, serum sickness

type 3 hypersensitivity rxn to PCN & cephalosporins

contact dermatitis, SJS

type 4 hypersensitivity rxn to PCN & cephalosporins

maculopapular rash

_____________ occurs late in tx of 2-3% of pt receiving penicillin

penicillins, cephalosporins, bacitracin, vancomycin

list the cell wall synthesis inhibitors

oral

dosage form for dicloxacillin

injection, oral

dosage form for nafcillin

intravenous

dosage form for ampicillin

oral, injection

dosage form of amoxicillin

oral, injection

dosage form of amoxicillin + clavulanate

1. penicillin V

2. penicillin G

3. dicloxacillin

4. nafcillin

5. ampicillin

6. amoxicillin

7. amoxicillin + clavulanate

8. ampicillin + sulbactam

list the penicillins

1. cephalexin

2. cefazolin

3. cefaclor

4. cefuroxime

5. ceftriaxone

6. ceftazidime

7. cefepime

list the cephalosporins

blocks transpeptidase which inhibits the cell wall

MoA of vancomycin

1. history of non-response to penicillin or cephalosporin

2. condition not responding as expected

3. infection in unexpected location

4. history of previous MRSA infection

5. pain outside clinical presentation

6. history of recent incarceration, hospitalization, long-term care facility

7. health care worker

in what instances should you consider MRSA coverage?

1. nephrotoxicity

2. ototoxicity

3. red man syndrome

what are the SE of vancomycin?

red man syndrome

• intense red face, neck, upper torso w/ itching/burning

• due to overstimulation of mast cells → release of histamine

• treat w/ anti-histamine

• to avoid, slow IV infusion over 1-2hrs

inhibits precursor peptidoglycan movement through cell membrane so it cannot form the cell wall

what is the MoA of bacitracin?

ointment

dosage form of bacitracin

hypersensitivity, intolerance

contraindications of bacitracin

cationic detergent that interacts w/ phospholipids of the cell membrane disrupting the osmotic integrity of the cell → increases bacterial cell permeability → cell death

MoA of polymixin B

1. polymixin B

2. gramicidin

list the cell membrane toxins

no (due to neurotoxicity & nephrotoxicity)

is polymixin B used systemically?

1. irritation

2. allergic rxn of lids/conjunctiva (rare, mild)

what are the SE of topical application of polymixin B?

1. pain

2. chemosis

3. tissue necrosis

what are the SE of subconjunctival injection of polymixin B?

hypersensitivity

contraindications of polymixin B

makes a hole in the cell wall → alters permeability → cell death

MoA of gramicidin

bactericidal

is gramicidin bacteriostatic or bactericidal?

1. aminoglycosides

2. tetracyclines

list the 30S inhibitors

1. chloramphenicol

2. macrolides

3. lincosamide

list the 50S inhibitors

1. gentamicin

2. tobramycin

3. neomycin

4. amikacin

list the aminoglycosides

1. tetracycline

2. doxycycline

3. minocycline

list the tetracyclines

1. erythromycin

2. azithromycin

3. clarithromycin

list the macrolides

clindamycin

list the lincosamide

irreversibly binds to the A-site of 30S ribosomal subunit → misreading of transfer RNA codons

MoA of aminoglycosides

ung, sol

dosage forms of neomycin

ung, sol

dosage forms of gentamicin

ung, sol

dosage forms of tobramycin

compounded fortified sol

dosage forms of amikacin

bactericidal

are aminoglycosides bacteriostatic or bactericidal?

neomycin

• oldest aminoglycoside

• primarily topical use

  • repeated use results in drug sensitization → contact dermatitis

• never used stand alone

• broad spectrum coverage

  • not pseudomonas or MRSA

gentamicin

aminoglycoside used for severe infections

neomycin

50% of patients that are allergic to ______ are allergic to gentamicin

tobramycin

• similar use as gentamicin but less allergic hypersensitivity

• preferred topical

• 2nd most effective topical against MRSA

• pregnancy B

B

what is the pregnancy category of tobramycin?

amikacin

• 1st semi-synthetic aminoglycoside marketed

• chemical modification protects the molecule from many aminoglycoside-inactivating enzymes

• reserved for use in severe infections & resistance to tobramycin or gentamicin

• only available as a compounded fortified version

1. nephrotoxicity

2. ototoxicity

what are the systemic SE effects of systemic aminoglycosides?

parenterally

how must aminoglycosides be given if used systemically?

1. corneal toxicity (punctate epithelial erosion, delayed re-epithelialization, corneal ulceration)

2. allergic contact dermatitis

3. posterior segment toxicity (retinal/macula ischemia)

4. increased intracranial pressure

what are the ocular SE of topical aminoglycosides?

1. B-lactam antibiotics

2. vancomycin

aminoglycosides have a synergistic effect when used in combination with what 2 drugs?

separately

how must B-lactams & aminoglycosides be administered if they are used together?

binds to 30S ribosomal subunit → blocks attachment of aminoacyl t-RNA to the A-site → inhibits protein synthesis

MoA of tetracycline drugs?

1. antibacterial: chlamydia, TB, lyme, Rickettsial, brucellosis, typhus & Q fever, mycoplasma pneumonia, cholera, plague

2. anti-inflammatory effects

3. inhibition of bacterial lipases: decreasing of free fatty acids

4. anti-collagenase effects: corneal erosions & prevention of corneal melt

what are the indications for tetracycline drugs?

short acting

duration of action of tetracycline

oral

dosage form of tetracycline

oral

dosage form of doxycycline

oral

dosage form of minocycline

long acting

duration of action of doxycycline

long acting

duration of action of minocycline

bacteriostatic

are tetracyclines bacteriostatic or bactericidal?