Flashcards in Skin and Soft Tissue Pathology Deck (54)
4 commensal skin flora
Coagulase -ve staphylococci
5 common commensal skin viruses
Herpes viruses (HSV, VZV)
Which virus is transmitted from sheep and results in ulcerative skin lesions
Vesicle forms which grows to form an ulcer. When it ruptures, it releases vesicle fluid containing infectious particles. Virus gains entry via sensory nerve endings and migrates along the nerve to the DRG where it remains latent and the immune response is not stimulated. When reactivated, the virus migrates outwards to sensory nerve endings and causes the clinical manifestations of infection- preceded by tingling
Triggers of reactivation of HSV
Infection or stress
Primary infections of HSV
Extensive, painful lesion, occurs only once. Rare. Normally HSV1. HSV2 is usually genital herpes.
Secondary infections fo HSV
All ages, recurrent infection. Peri-oral. Weeping, vesicular
Diagnosis of HSV
Vesicle fluid contains virus-PCR
Treatment for HSV
Cold sores- topical aciclovir
Genical herpes/immunocompromised- oral aciclovir
Another name for strep pyogenes
Beta haemolytic streptococci
Usual causative organisms for bacterial skin infections
Pasteurella mulficida (grow in cat and dog's mouths)
Gram +ve cocci in clusters. Catalase +ve. Normal nasal flora in 30% population
Name some virulence factors of Staph A
Exotoxin production e.g. epidemolytic toxins A & B, toxic shock syndrome toxin, PVL-boils
Really nasty bacteria, gram +ve cocci in chains. Catalase -ve.
Name some virulence factors of strep P
M. proteins (antiphagocytic)
Streptolysins O and S
Hyaluronic capsule (antiphagocytic)
Hyaluronidase (facilitates intestinal spread)
C5a peptidase (anticomplementary)
Describe the rash in VZV
Weepeing, vesicular rash
Treatment for VZV
IV aciclovir if older, lower immune system or increased susceptibility to shingles
Causative organism for molluscum contagiosum
Molluscum contagiosum virus-poxvirus
Describe the appearance of molluscum contagiosum
Raised pearly lesions, umbilicated (central depressions) No sequelae.
Treatment of molluscum contagiosum
None. Usually disappear within 6-18 months. Physical treatments some times appropriate if disfiguring.
Causative organism for Impetigo
Often occurs at site of skin damage, superficial, thick scabs-'honey crusted lesions', with yellow exudate. often around the nose.
Local manifestation of impetigo
Generalised manifestation of impetigo
Staph scalded skin syndrome
Pathogenesis of impetigo
Desmosermal glycoprotein desmoglein-1 which is requied for cell to cell adhesion in the superficial epidermis is inactivated by ETA and ETB (epidermolytic toxin)
Causative organism for erysipelas
Infection of dermis
Ocurs at site of skin damag, often face or shin. Preceded by pain and tenderness, well demarcated inflamed lesions-red, swollen, painful or hot. Fever, malaise and local lyphadenopathy.
Infection of skin and subcutanous tissues, not bilateral.
Causative organisms of cellulitis
Pasteurella multicida (animal bites)