Superficial skin and soft tissue infection Flashcards
(21 cards)
What are the bacteria that makes up the normal flora of the skin
- Gram pos cocci : coagulase negative eg staph epidermidis
* Propionibacterium acnes and candida
What are the contributing factors to soft skin infection
- (Skin breach ) trauma ,medical techniques ,surgery
- immune-compromised states eg malnutrition ,diabetes and burn wounds
- immune-suppressive therapy eg transplantation
- chronic venous insufficiency
Classification of the skin and soft tissue infection
It is either classified as superficial /deep and complicated /uncomplicated
> Superficial : involing the epidermis and the dremis
> Deep : Extending o the subcutaneous layer ,fascia(fasciitis) or muscles (myosities )with / without necrosis
> uncomplicated : folliculitis
> Complicated : cellulitis with bacteremia ,myonecrosis
Discuss the primary pyodermas
*Infection of the skin that may/ may not involve the dermis and the subcutaneous tissue and may complicate with bacteremia
discuss Infectious gangrene : Cellulitis ,fasciitis and myositis and give example
Serious infections prone to complications and rapidly extend to deeper structures eg fascia and muscle
eg gas gangrene : clostridial (eg C.perfringes ) and non-clostridial eg strept. gas gangrene
Discuss the toxin-mediated cutaneous manifestation
Disease is not mediated by direct by microbial invasion but rather by exotoxins released by the bacteria ,causing skin toxin -mediated pathology eg scaled skin syndrome by S.aureus / toxin shock syndrome by strept or staphy
Cutaneous involvement in systemic microbial infection
*Primary site of infection is not the skin ,organisms seed via the blood stream from another organ to the skin
Discuss the impetigo : Primary ,superficial and uncomplicated
Vesicular lesions on exposed areas which become purulent ,rapture and the purulent discharge dries to form characteristic golden-yellow crust
- Occurs mainly in children ; peaks in hot and humid summer months
- Caused by Group A Stept
Compare erysipelas with cellulitis
Erysipelas is caused by strept pyogenes (GROUP A Strept) resulting in primary ,superficial and can extend into the deep ,complicated SSTI
Cellulities caused by S.pyogens ,Saureus ,H.Influenza can cause primary ,deep ,complicated SSTI
Discuss erysipelas (St Anthony s fire)
- Infection of the upper dermis involving superficial cutaneous lymphatic vessels thus can result in regional lymph node and tenderness
- Can be identifies by tender erythematous ,indurated plaque and demarcated border
- Accompanied by malaise ,aches ,fever and nausea
- Caused by : S.Pyogens( on the face ) and non.GAS ,staph on the lower extremities
Treatment : spontaneous resolution or antibiotics
Complication : abscess ,gangrene ,thrombophlebitis
Discuss cellulites
> Usually infection is caused by S.aureus ,GAS and vibro vulnificus
> Identification :
- Non-necrotizing inflammation of the skin and subcutaneous tissues and may be seen often after a breach
- Erythema ,pain ,hot , swelling
> Severe inspection suspected if :
- malaise
- fever
- toxicity
- lymphangitic spread (red lines streaking away from the area of infection )
- circumferential cellulitis
> Treatment :co-amoxyclav ,cefazolin , clindamycin ,ciprofloaxicin and IV for severe infection
Discuss necrotizing fasciitis
> Severe infection involving subcutaneous soft tissue ,mainly superficial and deep fascia
Fournier gangrene : form of necrotizing fascitis localized to scrotum and perineal area
Usually cute
> Symptoms :
* pain ,fever ,rapid progression to systemic toxicity
> Signs :
- crepitus (crackling sounds under the skin )
- foul smelling
- discoloration
- Within 3-5 days skin breakdown with blisters ,frank cutaneous ,necrosis and gangrene
List the 3 types of necrotizing fasciitis
Type 1.
*Caused by mixed pathogens including at least one anaerobe ,facultative anaerobe (onGAS eg Strept.Anginosus ) and enterobactereriaceae and it is common in diabetics
Type 2 :
- Due to GAS / S.pyogens with / without S.aureus
- Streptococcal pyrogens exotoxins A,B and C are directly toxic and tend to be produced by strains causing necrotizing fasciitis.
Type 3 : Associated with infection secondary to rare organisms .
*Bacteria : vibro vulnificus and listeria monocytogenes
> Treatment : Early surgery ,effective debridement and IV antibiotics eg penicillin and aminoglycoside and clindamycin
What is the difference between clostridial and non clostridial gas gangrene ?
> Clostridial gangrenous myonecrosis :
- Cuased by C.perfringens ,novyii
- Occurs in setting having traumatic injuries ,penetrating wounds ,surgical wounds and vascular insufficiency in extremity
Treatment : Aggressive surgical debridement even amputation ;penicillin/metronidazole +clindamycin +protein synthesis inhibitors (clindamycin ,chloramphenicol ,tetracycline - may be effective to inhibit the synthesis of clostridial exotoxins
> Non-clostridial gangrene myositis
*caused by strept. pyogenes
Give a reason why few neutrophils are from gas gangrene tissue
*C.perfringens phospholipase C stimulate formation of large intravascular platelet / leukocytes complexes . The absence of a tissue inflammatory response in C.perfringes gas gangrene is due to impaired neutrophil mobility caused by a large aggregates of adherent platelet induced by PLC
What is the difference between exotoxins and endotoxins
1.Exotoxins >Secreted by both gram + and - > Released by actively dividing cells > They are proteins >Highly immunogenic eg toxoids are used for immunization
2.Endotoxins
> Only gram - ( they are present in the outer membrane of gram - cell wall )
> Released maximally upon cell lysis
> They are LPS
>Immunogenicity is poorer relative tp exotoxins
Staphylococcal scalded skin syndrome
> Mot severe systemic infection of the S.aureus (usually in younger children )
Starts with fever ,tenderness and scarlatiniform rash
Due to exfoliative toxins which produce a widespread bullae (blisters ) and exfoliation
Caused by methicillin sensitive and methicillin resistant S.aureus
Treated with fluid therapy and IV anti-staphylococcal antimicrobe
heals within 2 weeks
Toxic shock syndrome
>Acute febrile illness with a generalized scarlatiniform rash associated with S.areus > Clinical features of the syndrome : *hypotension *3/ more organ systems dysfunction *desquamation of the skin lesions
> Associated with with production of staph toxic shock syndrome toxins 1
> TSST1 acts as a superantigen and non-specifically activates large numbers of T-cells ,causing a systemic inflammation reaction
T/F : Many systemic microbial infections can present with cutaneous manifestations
t
List the micribes that can cause systemic infection
- S.pyogens : purpura ,cutaneous hemorrhage
- N.meningitidis :macules ,petechaie ,purpura
- Salmonella Typhi : Rose spots
- Infective endocarditis : petechiae ,cutaneous manifestations of embolic spread
Prenteral Rx advocated when
Infection is rapidly spreading & co-morbidities (e.g. DM, neutropenia, immune-compromise/-suppression, heart failure, cirrhosis, renal failure, etc.) are present
It is important to ensure rapid, adequate serum and tissue antibiotic levels
cSSTIs are diagnosed: hospitalization and debridement often required
