[Web Module] Skin and Soft Tissue Infections

What is surgical debridement?

Removal of dead and diseased tissue to diagnose and treat conditions like necrotizing fasciitis.

The surgery should typically be done within 6 hours of admission and at least within 24 hours (the sooner the better)

How many surgical debridements are generally performed for necrotizing fasciitis?

Around 3-4 debridgements

What are skin grafts?

Medical grafting involving skin transplantation to improve function and appearance of a target area

How are blood cultures used to diagnose necrotizing fasciitis?

Can be used to perform gram staining and identify the causative organism via culturing.

Blood tests can also be used to suspect/facilitate diagnosis (leukocytosis + elevation in serum creatine phosphokinase levels)

What results will typically appear on blood tests for patients with necrotizing fasciitis?

Elevated white blood cells (leukocytosis)

Elevated serum creatine phosphokinase (indicates injury/stress to muscles)

Why are swabs often inadequate for diagnosing skin and soft tissue infections?

1. Can only collect small amount of fluid

2. Anerobic organisms grow very poorly on swabs since they are exposed to air

3. Fungal specimens cannot be accurately cultured as it may be contaminated by environmental fungi

4. Swabs are ineffective and collecting specimens from deep tissues

How are tissue cultures used to diagnose necrotizing fasciitis?

Tissue cultures are typically collected during surgical debridement and are stored in a sterile container for culturing.

1 drop of sterile saline should be added to small samples to ensure pathogen viability of the sample

What are three different types of hemolysis results on blood agar?

Alpha hemolysis - Incomplete

Beta hemolysis - Complete

Gamma hemolysis - None

What is alpha hemolysis?

Incomplete clearing of a blood agar, producing a greenish discoloration.

Indicative of streptococcus pneumonia

Which type of streptococci causes alpha hemolysis on a blood agar?

Streptococcus pneumonia

What is beta hemolysis?

Complete clearing of a blood agar

Indicative of streptococcus pyogenes

Which type of streptococci causes beta hemolysis on a blood agar?

Steptococcus pyogenes

What is gamma hemolysis?

Absence of hemolysis of a blood agar

Indicative of enterococcus faecalis

What type of streptococci causes gamma hemolysis on a blood agar?

Enterococcus faecalis

What are family prevention strategies if one family member has streptococcus pyogenes?

-Anyone with a sore throat or skin infection should be treated with antibiotics specific to streptococcus pyogenes (ampicillin)

-Family members without any symptoms should be cultured to see if they are colonized with streptococcus pyogenes then treated with antibiotics (ampicillin) if they are

What are strategies to determine the type of bacteria if multiple bacterial species are present on culturing?

Use of different culture mediums

Ex:

CNA media to r/o gram negatives

MacConkey agar to r/o gram positives and identify lactose fermentation

What are three serum biomarkers for sepsis?

1.Procalcitonin - calcitonin precursor and biomarker for sepsis

2. C-reactive protein - protein produced by liver during inflammation, biomarker for infection and sepsis

3. Lactate - measure of impaired tissue perfusion and organ dysfunction, biomarker for sepsis

What vital signs indicate possible sepsis in a patient?

Low BP

High HR

High Temp