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Flashcards in Microbiology-Septic Shock Deck (24)
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1
Q

Common causes of toxic shock syndrome

A

S. aureus or strep pyogenes produce super antigens that result in overactivation of T-cells and cytokine storm. Cytokine storm results in capillary leak, tissue damage, multigrain failure and death.

2
Q

Common situations that may promote staph toxic shock syndrome

A

Superabsorbant tampons, abscesses, wounds and post-inflluenza. Sometimes the source of infection is not as clinically apparent as strep TSS.

3
Q

CDC definition of staph TSS

A

1) Fever > 102 2) Hypotension (SBP < 90) 3) Diffuse macular erythroderma 4) Desquamation of skin 1-2 weeks later 5) 3+ organ system involvement. +/- s. aureus. - serology for measles, leptospirosis, Rocky Mountain Spotted Fever

4
Q

Common situations that may promote strep toxic shock syndrome

A

Invasive skin infections (necrotizing fasciitis, myositis) and bacteremia.

5
Q

How would you know this is necrotizing fasciitis?

A

Tenderness extends beyond the redness because the infection moves along fascial planes faster than it does through the skin.

6
Q

Diagnosis of strep TSS

A

1) Isolate strep pyogenes 2) Hypotension (SBP < 90) 3) 2+ of the following: renal insufficiency, coagulopathy, increases liver enzymes, RDS, erythematous macular rash and soft tissue necrosis.

7
Q

Staph superantigens? Strep superantigens? How do they work?

A

Staph: TSST-1 (menstrual), enterotoxins A-E. Strep: Strep pyrogenic exotoxins and strep superantigen. These antigens bind to the beta-subunit of the T-cell receptor and MHC II. This activates up to 20% of all CD4+ T-cells that go on to produce IFN-gamma, IL-1, IL-2, IL-6, IL-8, TNF-alpha & beta. These promote acute phase reactant production in the liver, ROS release from PMNs and leaky capillaries that ultimately causes inflammation, tissue injury and shock.

8
Q

Tx for TSS

A

1) IV fluids 2) Find site of infection 3) Antibiotics: vancomycin (MRSA), nafcillin (MSSA), penicillin (group A strep) + clindamycin (blocks toxin production) 4) +/- IVIG

9
Q

What is endotoxin synonymous with?

A

LPS, the principle component of the outer membrane in gram negative bacteria.

10
Q

How does our body recognize LPS?

A

TLR4. Binding of LPS to TLR4 results in macrophage activation and TNF-alpha release, which is the key mediator in endotoxic shock. After TNF, IL-1 is released, then IL-6.

11
Q

Common pathogens that are recognized by pattern recognition receptors (PRRs)?

A

Pathogen associated molecular patterns (PAMPS). PRRs include TLRs.

12
Q

Treatment of shock due to gram - endotoxic shock

A

1) IV fluids 2) Broad spectrum abx 3) Vasopressors/inotropes if needed. Note than many of the cytokine inhibitors have not been shown to be effective.

13
Q

Why is meningococcus so scary

A

“No other infection so quickly slays”. There are high levels of endotoxin released by the organism because the bacteria blebs lots of it into the blood that cause cytokines TNF, IL-1, IL- and IL-8 to go through the roof.

14
Q

Infection caused by gram-negative, encapsulated, aerobic diplococci shown in the CSF of a patient that died from meningitis below. What are the pathogenic serotypes?

A

Neisseria meningitides: A, B, C, X, Y, W135. Note that these have the ability to undergo capsule switching, which helps protect them from macrophages and complement-mediated lysis.

15
Q

Highest rate of meningococcus infection

A

< 1 years old. There is a little bump around age 18.

16
Q

Classic symptoms of meningococcal infection

A

Hemorrhagic petechial rash (in areas of pressure, especially belts and elastic straps), meningismus (neck stiffness/photophobia) and impaired consciousness. Note that by the time these symptoms present it is usually too late.

17
Q

How does meningococcal infection present, what is the spectrum?

A

Meningitis, meningitis + meningococcemia, meningococcemia w/o meningitis.

18
Q

Common sequelae in patients affected by meningococcemia

A

Loss of limbs, organ destruction, loss of hearing.

19
Q

How does meningococcus affect the blood vessels and cause petechia?

A

Vessels are infected and causes vasculitis.

20
Q

Synonyms for meningococcemia

A

Waterhouse-Friedrichsen syndrome and purpura fulminans, note that both of these are associated with necrosis of the adrenal glands.

21
Q

Why doesn’t everyone get meningococcemia? What factors increase risk for infection?

A

Many people have it in their throat, but not all strains are infectious. Also people with terminal complement deficiency (C5-C9), variations in mannose-binding lectin pathway, asplenia, cigarrette smoking and preceding URI increase risk.

22
Q

Dx of meningococcemia

A

CSF culture or PCR

23
Q

Tx of meningococcemia

A

3rd generation cephalosporin (ceftriaxone). Prophylaxis with quinolone or rifampin for close contacts. You could also give tetravalent (A,C,Y,W135) vaccine for MCV.

24
Q

Common cause of meningococcemia not covered in vaccine

A

Serogroup B