Micro 1

Question 1

Streptococcus pyogenes results in:

Answer 1

**Localized abcesses and Spreading abcesses and Streptococcal toxic shock syndrome **

• Localized* = Impetigo: confined to the epidermis; invasion through minor trauma. superficial vesicle clusters that are raw/weeping/form yellow crusts
• Spreading abscesses* = Erysipelas - involves dermal lymphatics, spreading area of erythema and edema with rapidly advancing, well-demarcated edges (“butterfly-wing” rash characteristically seen on the face), pain, and systemic infections, including fever and lymphadenopathy.

also = Cellulitis involves the subcutaneous fat layer, often develops at a site of previous trauma or skin lesion; the involved skin becomes tender, red, warm, and swollen, often abrupt onset of malaise, fever, chills, and headache.

Also = necrotizing fasciitis and myositis are infections of the deeper subcutaneous tissues, fascia, and muscle, characterized by extensive, rapidly spreading necrosis and gangrene of the skin and surrounding structures.

STSS = when local host defenses inadequate to control infection of wound, invasive streptococci enter the blood stream (bacteremia is common, in contrast with S. aureus). Selected strains produce streptococcal pyrogenic exotoxins (Spe). SpeA, is a superantigen. It allows simultaneous binding to MHC class-2 molecules and T-cell receptors, leading to the direct stimulation of T cells and IL-2 production. In response, there is a dramatic increase in production of cytokines IL-1 and TNF, and a systemic inflammatory response occurs. Fever = most common presenting sign, although some patients present with hypothermia secondary to shock. Patients also have tachycardia and hypotension. Necrotizing fasciitis or myositis is found in 50-70% of patients, requiring surgical debridement or amputation. Patients with STSS require prompt antibiotic therapy using empirical antibiotic coverage but intensive care is urgently needed to manage the complications of cardiovascular collapse.

Question 2

The following are caused by:

impetigo

erysipelas

cellulitis

necrotizing fasciitis and myositis

STSS

Answer 2

Streptococcus pyogenes

Question 3

cause of impetigo:

Answer 3

usully group A streptococcus infection

Question 4

presenting symptoms of Impetigo:

Answer 4

localized abcessess

confined to epidermis

invasion thru minor trauma

clusters of superficial vesicles that make raw weeping surface

main presentation often = yellow crusts

highl contagesou

Question 5

presenting symptoms of Ersipelas

Answer 5

spreading abcessess

dermal lymphatic involvement

spreading area of erythema and edema w/rapidly advancing, well-demarcated edges (think butterfly-wing rash on face)

pain

systemic infections like fever/lymphadenopathy

Question 6

presenting symptoms of cellulitis

Answer 6

spreading abcessess

invovles subcutaneous fat layer

often develops at site of previous trauma/skin lesion, which becomes tender/red/warm/swollen

abrupt onset of malaise

abrupt fever

abrupt chills

abrupt headache

Question 7

presenting symptoms of Necrotizing fasciitis and myositis:

Answer 7

spreading abcesses

deeper subcutaneous tissues/facia/muslce infections

extensive, rapidly spreading necrosis & gangrene of skin & surrounding structures

Question 8

presenting symptoms of Streptococcal toxic shock syndrome (STSS)

Answer 8

local host defenses unable to control progression of wond infection

invasive streptococci enter blood stream

bactermeia is common

certain strains produce streptococcal pyrogenic exotonins

FEVER

(some have hypothermia secondary to shock)

Patients have tachycardia & hypotension…

Necrotizing fasciitis or myositis involved in 50-70% of patients…

cardiovascular collapse can occur

Question 9

features of host immune resopnse associated w/immunopathogenesis of streptococcal toxic shock syndrome:

Answer 9

SpeA = superantigen that binds to MCH class2 molecules and T-cell receptors (stimulates T-cells and causes IL-2 production)

Cytokines IL-1 and TNF production increases, and with it inflammatory response

Question 10

What does

staphylococcus aureus cause?

Answer 10

pyogenic infections (abcesses/localized infections of skin)

    **Folliculitis** **carbuncles  chronic furunculosis (impaired immune response)  bullous impetigo**

Surgical wound infections (nosocomial)
High rate of MRSA involvement

Bacteremia/Endocarditis
Spread of infection to the heart. Most common in IV drug users. May sometimes occur as a secondary infection after a varicella-zoster infection.

Toxin-Associated Diseases

Toxic-shock syndrome (TSS)
Menstrual or nonmenstrual form (wound). TSST-1 superantigen mediated.

Staphylococcal scalded-skin syndrome (Ritter disease)
Usually occurs in children less than five years of age. Exfoliatin toxin causes sloughing of the skin.

Question 11

Presenting symptoms of Staphyloocccal scalded-skin syndrome:

Answer 11

Usually occurs in children less than five years of age. Exfoliatin toxin causes sloughing of the skin.

Question 12

features of host immune response associated with immunopathogenesis of Toxic-Shock Syndrome

Answer 12

Toxic-shock syndrome (TSS)

Menstrual or nonmenstrual form (wound). TSST-1 superantigen mediated.

Question 13

Treatment of Staphylococcus aureu?

Answer 13

Treatment – clean wounds, drain purulent collections, fluid replacement, penicillinase-resistant penicillins can hasten recovery but not curative.

Question 14

treatment of streptococcus pyogenes:

Answer 14

Penicillin G. Clindamycin with TSS. Surgery for necrotizing fasciitis.