Thread by @MayoClinicINFD

Images of Infectious Diseases

In addition to these CT findings, there are multiple wedge-shaped peripheral areas of hypoattenuation in the spleen.

Name the host and the risk factor.

28 PWID. No PMH.
Fever, chills, sweats. cough, abdominal pain x 1 week

PE: ill-looking, murmur, scattered rales, petechiae
WBC 19.5, Cre 2.16
Blood culture: MSSA
CT (prior tweet)
TEE ordered.

Whic of the following options is best for Rx?

1/
Case diagnosis:
#MSSA #Endocarditis in #PWID

TEE: TV multiple vegetations + small aortic valve lesion. PFO with small right to left shunt

2/
#Right-sided #Endocarditis
1. PWID (most common)
2. Cardiac device (CIED/leads)
3. Vascular catheters (central line/PICC)
4. Cardiac anomaly (R-side)

3/
#Right-sided #Endocarditis
1. 10% of endocarditis
2. Tricuspid 90% > pulmonic
3. Concomitant left sided IE in 13% (this case)
4. S aureus >>> streptococcus >> enterococcus >> GNB, fungi (rare)

4/
Right-sided #Endocarditis in #PWID
#Staphylococcus aureus most common pathogen (70%)

Use of saliva on injection equipment: oropharyngeal flora - Streptococcus milleri, Eikenella corrodens, H. parainfluenza

5/
Peripheral septic embolization is rare in right-sided #endocarditis

You should consider:
- left-sided involvement (note: MSSA can cause septic foci in absence of left sided endocarditis): sites - brain, spleen, spine, kidneys, others...
- atrial septal abnormality (PFO)

6/
Rx of #uncomplicated right-sided #endocarditis
Rx: 2-week of IV oxacillin / nafcillin
Alternate: cefazolin
No need to add aminoglycoside!

If beta-lactam allergy:
Vancomycin or Daptomycin x 4 weeks

CAUTION: screen for “complicated cases” (see next)

pubmed.ncbi.nlm.nih.gov/8967707/

7/
Complicated right-sided #endocarditis
1. Concomitant left sided endocarditis
2. Complications (abscess, heart block)
3. Metastasis outside of lung
4. No defervesce within 72h of Rx
5. Renal failure
6. MRSA

If any of above is present:
—> Rx as left-sided endocarditis (next)

8/
Rx of “complicated” right-sided MSSA endocarditis

Rx similar to left-sided MSSA endocarditis
- Nafcillin or oxacillin for 6 weeks
- Cefazolin for 6 weeks

Suggested answer to MCQ:
cefazolin for 6 weeks

9/
What is #Cefazolin #InoculumEffect

The phenomenon of loss of therapeutic efficacy of cefazolin (and other early generation cephalosporin) when large numbers of organisms (inoculum) are present.

Concern in deep-seated MSSA infections (endocarditis)

aac.asm.org/content/53/8/3…

10/
#Nafcillin vs #Cefazolin in #MSSA

Cefazolin - less nephrotoxicity and no difference in clinical success vs nafcillin for MSSA BSI
(not an endocarditis study)

Baseline renal insufficiency in our case led to concern for prolonged nafcillin use

doi.org/10.1016/j.jmii…

11/
#Oxacillin vs #Cefazolin in #MSSA

Cefazolin similar to oxacillin for treatment of “complicated” MSSA bacteremia but with significantly improved safety.

aac.asm.org/content/58/9/5…

12/
How about oral option in #endocarditis
#POET trial

“Left-sided” endocarditis in stable condition: changing to oral antibiotic was noninferior to continued IV antibiotic Rx.

Note:
Limited data in “right-sided” endocarditis

nejm.org/doi/full/10.10…

13/
Need of antibiotics for endocarditis and invasive infections in #PWID

Access to oral antibiotic therapy for PWID who cannot complete prolonged inpatient IV antibiotics is beneficial.

Consider this option for those who leave against medical advice.

doi.org/10.1093/cid/ci…

14/
Indications for surgery in right sided IE
1. Large vegetation
2. Recurrent septic pulmonary emboli
3. Highly-resistant / virulent organism (fungi)
4. Persistent bacteremia

Note:
Uncommon complications in right-sided IE
- Heart failure
- Heart block
- Paravalvular abscess

/15
Case resolution
Right sided endocarditis with PFO, left sided involvement and septic embolization (lungs and spleen)

Rx initially oxacillin (inoculum effect) then switched to cefazolin for total of 6 weeks antibiotic duration

Thanks for participating.
Stay well everyone!