Treatment of Bacterial Skin Diseases (Marsella)

Question 1

Choice of abx determined by…

Answer 1

• Susceptibility of the bacteria
• Concurrent disease
• Depth of infection
• Length of tx
• Breed
• Age
• Owner constraints (time, money, drug admin)

Question 2

Abx spectrum choice

Answer 2

• Start w/ narrow spectrum
  
  • Some abx develop resistance rapidly
  • Never use big guns first for pyoderma

Question 3

Abx & glucocorticoid use?

Answer 3

Don’t do it!

Question 4

Abx therapy for mixed infections

Answer 4

• If possible, select abx effective against various organisms
• If not possible, select abx effective against staph

Question 5

Reasons for treatment failure

Answer 5

• Failure to ID all underlying causes
• Wrong abx
• Inappropriate dose
• Inappropriate length
• Concurrent steroids
• foreign body reaction

Question 6

1st line abx for pyoderma

Answer 6

• Erythromycin
• Lincomycin
• Clindamycin
• 1st generation cephalosporins

Question 7

2nd line abx for pyoderma

Answer 7

• Potentiated sulfonamides
• 3rd generation cephalosporins
• Amoxicillin/clavulanic acid

Question 8

3rd line abx for pyoderma

Answer 8

• Fluoroquinolones
• Chloramphenicol
• Rifampin
• Amikacin

Question 9

Erythromicin mechanism of action

Answer 9

• Macrolide, inhibits ribosomal protein synthesis
• Bacteriostatic
• Time-dependent

Question 10

Erythromycin spectrum

Answer 10

Narrow spectrum for staphylococcus

Question 11

Adverse effects of erythromycin

Answer 11

• Inhibition of cytochrome P450 (drug interactions)
• GI

Question 12

Lincomycin mechanism of action

Answer 12

• Macrolide-like
• Bacteriostatic

Question 13

Disadvantage of lincomycin

Answer 13

Rapid resistance (cross-reactive w/ erythromycin)

Question 14

Clindamycin mechanism of action

Answer 14

Related to lincomycin (marcrolide-like)

Question 15

Clindamycin uses

Answer 15

• Superficial pyoderma
• Deep pyoderma (recurrent infections)
• Cases of S. schleiferi

Question 16

Advantage of clindamycin

Answer 16

Well tolerated by most patients

Question 17

Cephalosporin mechanism of action

Answer 17

• Inhibition of synthesis of bacterial cell wall
• bacteriocidal

Question 18

First generation cephalosporin (cephalexin) uses

Answer 18

• 1st line
• broad spectrum, but primarily gram+

Question 19

First generation cephalosportin (cephalexin) disadvantages/adverse effects

Answer 19

• Increasing reports of resistance
• Vomiting/diarrhea
• Immune-mediated hemolytic anemia
• Immune-mediated thrombocytopenia
• Urticaria
• Drug eruptions (EM, TEN, PF)
• (Rarely - neurotoxicity, neutropenia, interstitial nephritis)

Question 20

Potentiated sulfonamides mechanism of action

Answer 20

Interfere w/ synthesis of folic acid

Question 21

Potentiated sulfonimides adverse effects

Answer 21

• Sulfa groups are very allergenic and my trigger hypersensitivity reactions (types I, II, III)
• Anemia, leukopenia, thrombocytopenia
• Fever
• KCS (keratoconjunctivitis sicca)
• Hepatopathy
• Arthropathy (shifting leg lameness)
• Cutaneous eruptions
• Hypothyroidism
• Polymyositis

Question 22

Potentiated sulfonamides contraindications

Answer 22

• Anti-acids interfere w/ absorption
• Do NOT use in dobermans and rotweillers
  
  • Incr. risk of arthropathy
  • possible defect of detox

Question 23

Silver sulphadiazine

Answer 23

• Topical sulfonamide
• Broad spectrum
• Ideal for pseudomonas

Question 24

Third generation cephalosporins

Answer 24

• Convenia, simplicef
• Gram negative
• Broader spectrum than 1st gen
• Use as 1st choice only if compliance issues are anticipated (injection that lasts several days rather than owners giving pill)

Question 25

Beta-lactamase resistant penicillins

Answer 25

* Oxacillin, dicloxacillin, nafcillin * Expensive * Excellent for *staph* * TID

Question 26

Amoxicillin/Clavulanic acid

Answer 26

* Broad spectrum (primarily gram+) * Bacteriocidal * Rapid absorption * GI adverse effects

Question 27

Chloramphenicol mechanism of action

Answer 27

* Inhibiting ribosomal protein synthesis * Metabolized by liver * Bacteriostatic * Broad spectrum

Question 28

Chloramphenical adverse effects

Answer 28

* Depression of microsomal enzymes (inhibits metabolism of other drugs) * Aplastic anemia in owners (wear gloves when handling) * GI, anorexia * Elevated liver enzymes * Anemia * Peripheral neuropathy (large breed dogs)

Question 29

Fluoroquinolones mechanism of action

Answer 29

* Inhibiting DNA gyrase (DNA replication) * Bacteriocidal * **Concentration dependent** * Great penetration in tissues * Accumulate in neutrophils and macrophages

Question 30

Fluoroquinolone uses

Answer 30

* Broad spectrum * Effective against *Staph* and *Pseudomonas* * **Resistant cases** (NOT 1st line)

Question 31

Fluoroquinolone disadvantages/adverse effects

Answer 31

* Absorption inhibited by anti-acids * GI * Neurological * Seizures * Arthropathy (incr. risk when receiving cyclosporins) * Blindness (cats, Baytril) * Do NOT give in cats or growing dogs

Question 32

Enrofloxacin (Baytril)

Answer 32

* Metabolized into ciprofloxacin * Food admin incr. amount of cipro

Question 33

Fluoroquinalones (examples)

Answer 33

* Enrofloxacin (Baytril) * Marbofloxacin (Zeniquin) * Orbifloxacin (Orbax) * Moxifloxacin * Pradofloxacin (veraflox)

Question 34

Doxycycline

Answer 34

* Resistant cases * Time dependent * Anti-inflammatory * Vomit/diarrhea, nausea, yellow staining of teeth * **Esophageal strictures in cats**

Question 35

Mupirocin

Answer 35

* Topical abx * Good for *Staph* * Minimal systemic absorption

Question 36

Polymyxin B

Answer 36

* Topical abx * Used for resistant *Pseudomonas* * Binds to cell membrane (more permeable)

Question 37

Long term abx therapy (good/bad?)

Answer 37

* Not recommended * Avoid pulse therapy (administration of supra-pharmacologic doses of drugs in an intermittent manner to enhance the therapeutic effect and reduce the side effects)