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Staph / Strep - Necrotizing Fasciitis and TSS
Terms in this set (24)
What are medically relevant species of Streptococci discussed in this class (Hint: 5)?
1. Streptococcus pyogenes (GAS)
2. Streptococcus agalactiae (GBS)
3. Streptococcus pneumoniae
4. Enterococcus faecalis
5. Viridans streptococci
What are the general characteristics of Streptococci bacteria?
1. Gram positive cocci (spheres) that grow in chains
2. Non-spore-forming and non-motile
3. Facultative anaerobes that ferment variety of sugars (production of lactic acid)
4. Catalase NEGATIVE
5. Hemolytic on blood agar (containing sheep red blood cells)
What are some defining characteristics of Streptococcus pyogenes (GAS)?
2. Bacitracin sensitive
3. Pyrrolidonyl arylamidase (PYR) positive
What are some defining characteristics of Streptococcus agalactiae (GBS)?
2. Bacitracin resistant
3. Hippurate hydrolyzation
4. CAMP test positive
What are some defining characteristics of Streptococcus pneumoniae?
2. Optochin sensitive
3. Lancet-shaped diplococci
4. Lysed by bile
What are some defining characteristics of Enterococcus faecalis?
1. Pyrrolidonyl arylamidase (PYR) positive
2. Varied hemolysis
3. Esculin hydrolyzation
4. Bile (40%) and NaCl (6.5%) tolerant
What are some defining characteristics of Viridans streptococci?
2. Optochin resistant
3. Not lysed in bile
What are the different disease that Streptococcus pyogenes can cause?
1. Pharyngitis ("Strep Sore Throat") Scarlet Fever
5. Necrotizing Fasciitis
6. Streptococcal Toxic Shock Syndrome
1. Rheumatic Fever
2. Acute Glomerulonephritis
What are the risk factors of necrotizing Fasciitis?
1. in general immuno-compromised patients
2. 18% to 60% of cases are associated with diabetes mellitus
3. chronic cardiac disease, malnutrition, cancer, age, alcohol abuse, intravenous drug abuse, obesity and smoking
4. blunt trauma
5. soft tissue infection
7. subcutaneous injury
What is the system clinical presentation of necrotizing fasciitis?
- 35% show acute renal failure
- 29% coagulopathy
- 28% liver function tests are abnormal
- 14% acute respiratory distress syndrome
- 46% detectable bacteremia
- 100% disproportionate pain
What are the clinical and lab diagnosis necessary to diagnose necrotizing fasciitis?
- Imaging can reveal gas development
- Soft tissue oximetry
- Incisional exploration or biopsy
- Blood cultures: Up to 60% positive in GAS, lower in mixed infection
- Gram stain
- CBC: haemoglobinuria and leucocytosis is common in GAS
- Acute renal failure due to sepsis = high level of serum C reactive protein
- High creatine levels due to myonecrosis or myositis
- Severe metabolic acidosis = high serum lactate combined with low sodium levels
What is the clinical treatment of necrotizing fasciitis?
1. Immediate surgical referral improves survival
2. Aggresssive antibiotic therapy and prompt (aggressive) surgical debridement
3. Resuscitation with intravenous fluids and colloids
What antibiotics are suggested for a Strep infection?
What are the general characteristics of Staphylococcus bacteria?
- Gram positive cocci ("bunch of grapes" described in culture)
- Facultative anaerobic bacteria
- Able to grow at high salt (10% NaCl)
- Prevalent on the skin and mucous membranes of humans
Infants are at risk for what disease if infected with Staphylococcus aureus?
- Staphylococcal scalded skin syndrome
- Ritter's disease
Young children with poor personal hygiene are at risk for what disease if infected with Staphylococcus aureus?
Patients with intravascular catheters are at risk for what disease if infected with Staphylococcus aureus?
Bacteremia and endocarditis
Patients with compromised pulmonary function or respiratory infection are at risk for what disease if infected with Staphylococcus aureus?
What is the current treatment for infection of Staphylococcus aureus?
- Antibiotics: Oxacillin or Vancomycin for oxacillin-resistant strains
- Identification and drainage of infection
- Thorough hand-washing and covering of exposed skin of medical personne
Toxic Shock Syndrome is presented with what symptoms?
- Sudden onset of fever
- Renal or respiratory failure
- Changes in mental status
What are the diagnostic criteria for Streptococcus Toxic Shock Syndrome?
1. Isolation of GAS from sterile site (blood, CSF) and/or non-sterile site (skin lesion)
2. Clinical signs of severity: Hypotension (<90 mm Hg sys.) + two or more clinical abnormalities:
- Renal impairment
- Liver abnormalities
- Acute respiratory distress syndrome
- Extensive tissue necrosis
- Erythematous rash
What are the diagnostic criteria for general Toxic Shock Syndrome?
1. Temperature of more than 38.9 °C
2. Systolic blood pressure <90 mm Hg
3. Widespread sunburn-like rash
4. Rash with subsequent desquamation
5. More than three of the following:
- Gastrointestinal: vomiting and diarrhea
- Muscular: severe myalgias
- Mucus membranes: hyperemia
- Renal: high levels of blood urea nitrogen (BUN) & creatinine, pyria
- Liver: hepatitis with serum bilirubin, aspartate transaminase (AST) and alanine transaminase (ALT) 2 x normal
- Blood: thrombocytopenia
- CNS: disorientation without focal
What are superantigens (SAgs)?
- Bacterial antigens that are extremely potent at stimulating T lymphocytes and cytokine production in an uncontrolled manner.
- Cause massive systemic release of pro- inflammatory cytokines, such as tumour necrosis factor-alpha (TNF-α) and interleukin- beta (IL-1β), and T cell mediators, such as IL-2
- The result is a fever, shock, and even death.
What is the difference between current treatment for general Toxic Shock Syndrome and Staphylococcus Toxic Shock Syndrome?
- Aggressive fluid replacement
- Identification and removal of the infection site
The main difference is:
TSS requires intravenous treatment with antibiotics resistant to beta- lactamase
sTSS requires intravenous treatment with antibiotics penicillin G and clindamycin
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