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Chapter 19 Microbial Diseases of the Skin

I. Barrier Protection and Anatomical Review

A. Anatomy

B. Normal flora

i. Diphtheroids – P. acne, body odor

ii. Staphylococci & Streptococci-

iii. Fungi and viruses

II. Infections of the Skin

Disease	Etiologic Agent	Pathogenesis (mediated by exotoxins and virulence factors)	Symptoms	Transmission	Prevention and Treatment
Bacterial Skin Infections
Folliculitis	Staph. aureus GPC cl, catalase +, coagulase +, MSA +	hair follicle infected Enzymes Coagulase, Hyaluronidase, Staphylokinase, Lipases, B-Lactamase Capsules toxins leukocidins	eye - sty furuncle - boil carbuncle	Every spread by contact		Clean and drain abscess MRSA v MSSA - determines treatment SXT or Methicillin family *no food handling
Scalded Skin Syndrome	Staph. aureus GPC cl, catalase +, coagulase +, MSA +	exfoliatins coagulase, hyaluronidase, capsule, leukocidins	Purulent wound, skin appears burned toxemia	Person to person		Clean wounds thoroughly nafcillin or oxacillin
Impetigo pyoderma **text is not correct	Streptococcus pyogenes Group A GPC ch, catalase -, β hemolytic Staph. aureus	hemolysins, M protein interferes with complement DNAase,	Weeping blisters, Spread through blood	Person to person – quickly spread through droplet & contact		Clean wounds, caution with respiratory penicillin, erythromycin
Necrotizing Fasciitis	Streptococcus pyogenes Group A also groups C &G	hemolysins, M protein interferes with complement DNAase, exotoxin A, streptokinases	intense pain and swelling, muscle fascia and deep tissue involvement toxemia enhances tissue destruction	wounds contaminated with the bacteria		Debride wound Clindamycin & penicillin
Acne	Propionobacterium acnes Some Staph	excessive oil associated with puberty	superficial inflammation of oil glands	normal flora		Accutane, minocycline clear light
Pseudomonas	Pseudomonas aeruginosa	fimbrae, adhesins, endotoxins, exotoxins, pyocyanin Pseudomembrane formation	infects surfaces that have lost barrier protection - opportunistic	water - swimmer's ear, burn patients		anti-pseudomonal penicillin, aminogylcosides
Anthrax	Bacillus anthracis GPR	aerobic endospore forming	infects through wound, eschar - black wound	soil		penicillin and erythromycin

Case

Disease	Etiologic Agent	Pathogenesis	Symptoms	Transmission	Prevention and Treatment
B. Viral Infections of the Skin
Pox viruses Smallpox Cowpox monkeypox	DNA viruses variola, vaccinia (cows)	adhesion molecules variola major and variola minor	lesions that form macules, papules, vesicles, pustules	respiratory secretions, contact	vaccination
Herpes	HSV 1 HSV 2	double stranded DNA serious in immunosuppressed and neonates	painful lesions	contact with active lesions latent infection	no vaccine, no treatment to prevent but lessens duration
Warts –	Papilloma virus - dsDNA	Invades epithelium and transforms cells – genital warts & Cervical cancer	Benign tumor on skin, plantar = deeper invasion self-regression	Contact through broken skin, virus survives on fomites	Treatment by removing abnormal cells – surgery freezing, chemotherapy; self-resolution in 2 years
Chickenpox (disseminated) Varicella –Zoster Shingles (limited to nerves)	Herpes virus dsDNA With latent tendencies	Inhaled, invades mucosa, spreads through blood & lymph nodes	Erupting lesions , itchy, papules-vesicles 2° bacterial infections & scarring	Air and contact	Vaccination Isolation, no general treatment, IgG for serious cases (pregnancy and neonatal infections serious)
Measles Rubeola – red or hard measles	Paramyxovirus ssRNA enveloped	Inhaled, invades mucosa, spreads through blood & lymph nodes, destroys respiratory membrane	Cold-like symptoms, rash moving from extremities in, Koplik’s on tongue, 2° bacterial infections- pneumonia, otitis, encephalitis, SSPE	air	Vaccination MMR, no general treatment, (miscarriage potential no defects) Mortality – 1-2/1000
Measles Rubella – German Measles	Togavirus ssRNA	Inhaled, invades mucosa, spreads through blood & lymph nodes	Mild disease with light rash moving from center out	Air (40% asymptomatic contributing to spread)	Vaccination MMR, no general treatment, (congenital rubella = fetal cells infected chromosome damage defects in heart, brain, eyes, ears)
Other common rashes Erythema infectiosum Fifth's – Parvovirus; Roseola – Herpes 6

Disease	Etiologic Agent	Pathogenesis	Symptoms	Transmission	Prevention and Treatment
C. Fungal infections of the skin
Tinea or Ringworm	Dermatophytes Epidermophyton, Trichophyton, Microsporum	Invade nails, hair, skin (keratin)	May begin with papules, Dry red cracked skin	Contact, moist warm environments	Antifungals – topical treatment, environmental controls; nails hardest to treat
Candida	Candida albicans	Moist skin areas, under diapers, skin folds	Red papules to red rash	contact	OTC, nystatin, Increased incidence in Diabetics & obesity
D. Parasitic Infections of Skin
Scabies	Sarcoptes scabiei	mite burrows into skin and lays eggs, inflammation, allergic reaction	Intense itching & rash	burrowing arachnid	topical miticides
Dracunculiasis Guinea Worm Fiery Serpent	Dracunculus medinensis	Worm larvae enters through skin from contaminated water	Itching growth beneath skin; immune response causes	Water exposure	Control intermediate host, Physical removal,

Review

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Bakersfield College | Kern Community College District | Janet Fulks
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Date last updated 11/01/2011
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