Microbiology of Skin Flashcards
Gram positive cocci in clusters
Staphylococcus sp.
What distinguishes staph aureus from other staph species (other than gold colour)?
It produces coagulase
What toxins do some staph strains produce?
Enterotoxin (food poisoning), SSST (staph scalded skin syndrome toxin) and PVL (Panton valentine leukocidin)
Gram positive cocci in chains
Streptococcus sp.
How are strep sp. classified?
Haemolysis (Beta-haemylytics then further classified as group A or B)
What are 2 important alpha-haemolytic strep sp.?
Strep pneumonia and strep viridian’s
What is an important non-haemolytic strep?
Enterococcus sp. (commensals of bowel)
What components of the skin fight bacterial infection?
Skin barrier; dry surface (cause desiccation); sebum inhibits growth; competitive bacteria
What are 3 main commensal bacteria of the skin?
Staphylococcus epidermis; Corynebacterium sp. (“diphtheroids”) and Proprionobacterium sp.
What antibiotic is used for staph aureus and strep pyogenes?
Flucoxacillin
What is necrotising fasciitis?
Bacterial infection spreading along fascial planes below skin surface → rapid tissue destruction
What are the 2 types of necrotising fasciitis?
Type 1 – mixed anaerobes & coliforms, usually post-abdominal surgery and Type II – Group A Strep infection
Tina =
Ringworm
Dermatophyte infection aka
Fungal infection (Ringworm)
What is the pathogenesis of dermatophyte infection?
- Fungus enters abraded or soggy skin
- Hyphae spread in stratum corneum
- Infects keratinised tissues only (skin, hair, nails)
- Increased epidermal turnover causes scaling
- Inflammatory response provoked (dermis)
- Hair follicles and shafts invaded
- Lesion grows outward and heals in centre, giving a “ring” appearance
What are 3 main causal organisms for fungal infections?
Trichophyton rubric (>70%); Trichophyton mentagraphytes (>20%) and Microsporum canis
What investigations should be done for fungal infections?
Wood lamp and scrapings/clippings for microscopy and culture
What is the treatment for small areas of ringworm?
Clotrimazole (canestan) cream or similar, topical nail paint (amorolfine)
Where do candida infections occur?
Skin folds where area is warm and mois
What is the causal organism of scabies?
Sarcoptes scabiei
What is the treatment of scabies?
Malathion lotion and benzyl benzoate (avoid in kiddies)
What is the treatment of lice?
Malathion
Which virus is responsible for chickenpox and shingles?
Varicella zoster
What is Neonatal Varicella zoster virus and how can it be prevented?
Secondary to chickenpox in mother later in pregnancy, can be prevented with VZV immune globulin in susceptible women
What kind of distribution does Shingles have?
Dermatomal
What is pain associated with shingles for more than 4 weeks known as?
Post Herpetic Neuralgia
What is ophthalmic zoster?
Shingles affecting there ophthalmic division of the trigeminal nerve
Ramsay-Hunt Syndrome
A complication of shingles where the facial nerve is affected , causing vesicles and pain in auditory canal and throat
Which virus causes primary gingivostomatitis?
Herpes simplex virus
Which type of HSV normally causes oral lesions?
Type 1
What is the treatment for HSV?
Aciclovir
Erythema Multiforme
A hypersensitivity reaction usually triggered by infections, most commonly herpes simplex virus (HSV)
What is the management of molluscs contagiousum?
It is self-limiting but takes months to disappear, so can be treated with local application of liquid nitrogen
Which virus causes warts?
Human papilloma virus
What is the treatment for warts?
Self-limiting, but can use topical salicylic acid
Which types of HPV are most commonly associated with warts/verrucas?
Types 1-4
Which types of HPV are most commonly associated with genital warts?
Types 6 and II
Which types of HPV are most commonly associated with cervical cancer?
Types 16 and 18
What is Herpangina and which virus causes it?
Blistering rash of the back of the mouth, caused by enteroviruses?
Which viruses cause Hand, Foot and Mouth disease?
Enteroviruses
What is slapped cheek disease also known as, and what virus causes it?
Erythema infectosium, caused by parvovirus B19
Orf
A virus infection of the skin contracted from sheep and goats, presenting as firm, fleshy nodule on hands of farmers
Which bacterium causes syphilis?
Treponema pallidum
Which bacterium causes lyme disease?
Borrelia burgdorferi
Which mosquito spreads Zika?
Aedes aegypti
Which are the symptom onset and resolution of zika?
Onset: 3-12 days after exposure, Resolution: 2-7 days after onset
What are complications of zika?
Guillain-Bare syndrome and microcephaly
