ID Small Groups

Question 1

3 Identities In dx of a tender red leg

Answer 1

1. Noninfectious
   - DVT
   - Venous insuff
   - Fracture
   - Ruptured bakers cyst
2. Infectious - cellulitis
3. Infectious -

Question 2

4 Cardinal sz of soft tissue infection

cardinal findings of inflammation

Answer 2

1. Rubor - Redness
2. Dolor - Pain
3. Calor - Heat
4. Tumor - Swelling

*bonus: functio laesa

Question 3

Two most common pathogens that cause cellulitis

Answer 3

1. S. pyogenes (GAS)
   - cellulitis is assoc. with more rapidly spreading, diffuse process w. lymphangitis and fever
2. S. aureus (MRSA)
   - Cellulitis caused by MSSA or MRSA is usually associated with a focal infection, such as a furuncle, a carbuncle, a surgical wound, or an abscess.
3. less often GBS
   - elderly patients and those with diabetes mellitus or peripheral vascular disease

Question 4

Level of skin involvement for:

1. Erysipelas
2. Cellulitis
3. Abcess
4. Necrotizing Fasciitis

Answer 4

1. Erysipelas
2. Cellulitis
3. Abcess
4. Necrotizing Fasciitis

Question 5

Erysipelas

Answer 5

Infectious

1. NOT commonly seen in lower extremities (face)
2. Sharply demarcated borders
   (cellulitis is irregular)
3. Infects Superficial Dermal Papillae

Question 6

Cellulitis

Answer 6

Infectious

1. Cardinal signs of inflammation
2. Irregular border
   (erysipelas is sharp, Nec Fasc is poorly defined)
3. Fever +leukocytosis
4. Unilateral
5. Infects the dermal + Subcutaneous layer (where capillary vessels are)

Question 7

Nectrotizing fasciitis

• layer affected
• Organism
• borders

Answer 7

1. Affects subcutaneous tissue along the surface of the connective tissue that covers muscle (fascia)
   - S. pyogenes (GAS)

• Poorly defined erythema
  (erysip is sharp)
• PAIN IS OUT OF PROPORTION TO EXAM due to deep tissue involvement

Question 8

Is cellulitis almost always unilateral or bilateral?

Answer 8

Unilateral

venous insuff is often bilateral

Question 9

How does uncontrolled diabetes mellitus interfere with treatment for bacterial infxns?

Answer 9

1. DM interferes with neutrophil fxn
2. Infection causes inflammation –> TNF-a –> insulin resistance and worsens diabetes control
   - Catecholamines
   - TNF
   - IL-6

Question 10

Is culturing effective for cellulitis?

Answer 10

Yield of cultures is very low in cellulitis.
- if you get center of lesion –> 20% +
(meaning very low #bacteria cause cellulitis)

Question 11

Treatment for MRSA (find out bc they are resistant to cephalosporin - cephalexin)

Answer 11

TMP - SMX

Bactrim

Question 12

Which layer of skin is affected in:

1. Erysipelas
2. Cellulitis
3. Nec Fasc
4. Myositis

Answer 12

1. Erysipelas
   - Superficial Dermal layer
2. Cellulitis
   - Dermal + subcutaneous layer
3. Nec Fasc
   - Subcutaneous layer along fascia of muscle (pain out of proportion)
4. Myositis
   - Muscle

Question 13

Clinical manifestations of Nec Fasc

Answer 13

PAIN IS OUT OF PROPORTION TO EXAM

• due to deep tissue involvement
• thrombosis of small vessels and destruction of superficial nerves

Initially extremely painful –> anaesthesia with nerve dmg

Elevated creatinine kinase

Question 14

2 types of Nec Fasc and organisms involved

Answer 14

1. Type I: caused by mixed bacterial infxns
   (often including anaerobes)
   - typically in pts with risk factors: sx, DM, periph vascular disease
2. Type II: monomicrobial and can occur in any age group w/o any medical comorbidities

Question 15

Gold std for dx Nec Fasc

Answer 15

Open surgical inspection, with debridement as indicated: best way to determine the extent and severity of infection and to obtain material for Gram’s staining and culture.

High mortality so surgical debridement/biopsy should not be delayed
- or CT + MRI to view subcu and fascial edema

Question 16

Importance of type of treatment for Nec Fasc

Answer 16

Empiric IV then surgery
1. Clindamycin + Amp-Sulbactam:
cover broad spectrum of org in Type I
- Clinda suppress toxin (50S) and facilitate phagocytosis of S. pyogenes by inhib M protein

2. Amp-Sulbactam:
   If Type II and GAS alone is cause

Surgery - thrombosis of small vessels of skin prevents antimicrobials from reaching site of infxn

Question 17

Fast acuity and fast progression of pain and systemic toxicity in unilateral limb should alert you to?

Answer 17

Nec Fasc

• systemic: tachy, hypotensive, hyperthermic

Question 18

Does Nec Fasc commonly have an obvious portal of entry?

Answer 18

No - 50%

• trauma site
• sx
• peri-rectal abcesses
• decubitus ulcer/intestinal perforation

Question 19

Sz + sx of Endocarditis

Answer 19

Any febrile syndrome where there is evidence of >1 organ system involved

Question 20

Pre-existing cardiac lesions that predisposed Endocarditis

Answer 20

Heart murmur in 90% of cases:

Valvular lesions that lead to Hi P gradients can result in:

1. turbulent, non-laminar bf
2. Endothelial trauma
3. Fibrin-platelet dep.

organisms liek strep can produce extracellular polysacc dextrans that can adher to fibrin-platelet thrombi on damaged heart valves –> vegetation

Question 21

Attachment of bacterial species to endocardial structures

Answer 21

organisms liek strep can produce extracellular polysacc dextrans that can adher to fibrin-platelet thrombi on damaged heart valves –> vegetation

Prosthetic valve endocarditis
- Coag neg staph (S. epidermidis)

Question 22

Local destruction of endocardial structures

Local effect of IE on integrity of heart valves and surrounding cardiac tissue.

Answer 22

1. valvular insufficiency
2. CHF
3. Myocardial and valve ring abcesses
4. Pericarditis
5. Conduction system disturbances

Question 23

Embolization

Answer 23

Emboli can be release from the valve vegetation to any organ –>

1. embolic stroke
2. MI
3. Renal infarct
4. Retinal hemorrhage from left-sided valves (mitral/aortic)
5. Pulmonary emboli from right-sided valves (tricuspid)

Question 24

Systemic signs-fever, malaise

Answer 24

Bacteremia: cytokine mediated

• sepsis: chills, fever, sweats, cachexia
• Fatigue, weight loss, anemia may accompany IE

Question 25

Immune-complex mediated manifestations

Answer 25

Olser nodes - tender purplish raised papules on digits Roth spots - retinal flame-like hemorrhage on fundoscopy Glomerulonephritis

Question 26

Organisms most assoc. w/ 1. Acute endocarditis 2. Subacute endocarditis: 3. Prosthetic valve endocarditis

Answer 26

1. Acute endocarditis - S. aureus: fibronectin-binding protein that can invade intact endo 2. Subacute endocarditis - S. viridans - S. bovis - E. faecalis : can produce extracellular polysacc dextran to adhere to fibrin-platelet thrombi on dmged heart valves 3. Prosthetic valve endocarditis - Coag neg staph (S. epidermidis)

Question 27

HACEK group

Answer 27

Gram neg bacteria less commonly associated with endocarditis ``` H: Haemophilus A: Actinobacillus C: Cardiobacterium E: Eikenella K: Kingella ``` *candida can also cause endocarditis

Question 28

Duration of tx for IE

Answer 28

~4 weeks of bactericidal agents

Question 29

Drugs with good activity against MSSA

Answer 29

1. Dicloxacillin 2. Amox-clav Amox-sulbactam (IV) 3. Cephalexin *rest are PO

Question 30

Drugs with activity against MRSA

Answer 30

All PO 1. Clindamycin 2. TPM-SMX 3. Doxycycline-minocycline 4. Linezolid IV 1. Vancomycin (glycopeptide)

Question 31

Bactericidal

Answer 31

30S: 1. AG (30s) Peptidoglycan synth: 2. Vanc 3. PCN 4. Cephalosporin DNA fxn: 5. FQ 6. Metronid 7. Rifampin

Question 32

Bacteriostatic

Answer 32

1. Chloramphenicol 2. Clindamycin 3. Linezolid 4. Macrolides 5. TCN 6. Sulfonamides 7. Trimethoprim

Question 33

Hepatically elim drugs (nonrenal)

Answer 33

CCRIMESS 1. Clindamycin 2. Chloramphenical 3. Rifampin 4. Isoniazid 5. Metronidazole 6. Erythromycin 7. Sulfonamide 8. Streptogramins

Question 34

Risks for enteric infxn while traveling abroad

Answer 34

1. Eating uncooked, unpeeled vegetables 2. Fresh salsa (unbottled, open, many hands, uncooked) 3. ceviche (uncooked fish and vegies)

Question 35

Inflammatory vs Non-inflamm diarrhea

Answer 35

Inflammatory: - from colon - fever - fecal WBC/RBC Non-inflammatory: - from upper small bowel - no fever - no fecal WBC or RBC

Question 36

3 common organisms causing inflamm and non inflamm diarrhea

Answer 36

Inflam: 1. Campylobacter 2. Salmonella/ Shigella 3. EHEC Non-Inflam: 1. ETEC 2. Norovirus 3. Rotavirus - others: Giardia, Cryptosporidium, Vibrio cholera

Question 37

Single most important and effective intervention for controlling the morbidity and mortality of diarrheal illness in children and adults in U.S and worldwide

Answer 37

Rotavirus: 5% of all gastroenteritis in children ... but MOST COMMON CAUSE OF SEVERE GE IN INFANTS AND YOUNG CHILDREN Primary MOT is F-O route: highly contagious

Question 38

Diarrhea

Answer 38

3/M loose or watery stools lasting >24 hours

Question 39

Most highly recommended ab to treat travelers diarrhea

Answer 39

FQ (Cipro) - target DNA topo Macrolide - azithro: targets 50S Rifaximin (rifampin analog)

Question 40

Common etiologies of viral gastroenteritis in childhood

Answer 40

1. Rotavirus 2. Caliciviruses (norovirus, sapovirus) 3. Enteric adenovirus *Gastroenteritis (presence of both vomiting and diarrhea)

Question 41

Tx of viral gastroenteritis

Answer 41

Oral rehydration - water, glucose, sodium

Question 42

Strategies for prevention of viral gastroenteritis

Answer 42

Derp stuff Rotavirus: 2 types of vaccines - do not give after 12 weeks of age

Question 43

Viral vs bacterial etiology of gastroenteritis

Answer 43

Viral: 80% of diarrhea in children - no mucous/blood Bacterial: less common - blood/mucous in stool - fever *but 1/3 of rotavirus will have fever

Question 44

Enterotoxin prod by rotavirus

Answer 44

NSP4: alters epithelial cell fxn and permeability contributing to secretory diarrha

Question 45

FQs and their elimination

Answer 45

1. Ciprofloxacin 2. Levofloxacin Renally eliminated can cause tendon rupture, prolonged QT, or arthropathy

Question 46

Organisms most responsible for: 1. Cystitis: 2. Urethritis: 3. Cervicitis: 4. Vaginitis:

Answer 46

1. Cystitis: - E. coli - S. Sapro 2. Urethritis: - N. gonorrhoeae - C. trachomatis - HSV 3. Cervicitis: - N. gonorrhoeae - C. trachomatis 4. Vaginitis: - Candida - Trichomonas vaginalis

Question 47

First line tx for uncomplicated cystitis | - what if they are pregnant?

Answer 47

TMP-SMX **Nitrofurantoin or Fosfomycin for pregnancy

Question 48

First line tx for complicated cystitis

Answer 48

FQ - cipro/levo bactericidal Can cover GNR and some GP

Question 49

First line tx for uncomplicated and complicated pyeloneph

Answer 49

uncomp: FQ comp: Empiric broad spec. 3rd gen Ceph, FQ

Question 50

The majority of young sexually active pts who have genital ulcers have:

Answer 50

1. Genital herpes (HSV) 2. Syphilis 3. Chancroid (H. ducreyi) 4. LGV (C. trachomatis)

Question 51

How is acyclovir effective against HSV?

Answer 51

acyclovir is selectively PHOSPHORYLATED by HSV infected cells to acyclovir monophosphate