Chapter 19

Functions of the skin

-Prevents excess water loss

-Regulates temperature

-Assists in vitamin d formation

-Barrier against microbial invanders

-composed of two main layers:

-dermis

-epidermis

Wounds

-Trauma to to any tissue of the body: cuts, scrapes, surgery, bites, etc

-Allows microbes to infect deeper tissues of the body.

-In Most cases the other body defenses eliminate the infection

-can result in serious or fatal disease.

Skin Microbiata

-normally harmless microbes present on the skin.

-Compete with potential pathogens for nutrients and space: microbial antagonism

-cannot be completely removed by cleansing

-typically grow in most areas of the skin.

-waste products cause body odors

Components of Skin Microbiata

-made up various microbes:

-yeast:

malassezia

-bacteria:

staphylococus, micrococus, and diptherioids.

May produce disease if:

if pentrate epidermis or the immune system suppressed

Folliculitis(Signs and Symptoms)

-Infection of the hair follicle often a called a pimple

-called a sty when it occurs near the eyelid base.

-spread of the infection into sorrounding tissues can produce furuncles(aka boils)

-carbuncles occurs when multiple furuncles grow together.

Folliculitis (pathogen and virluence factors)

-commonly caused by staphlococus:

faculatively, anaerobic, gram positive.

cocci arranged in clusters.

Two species commonly found on the skin:

-staphylococus epidermis-generally harmless.

-staphylocous aureus-generally pathogenic

Folliculitis(Pathogensis)

-Staphyloccus transmitted via direct contact or fomites.

-bacteria enters hair follicles and sabaceous glands, multiples, and trigger inflammatory responses.

-Infection spread into the blood (bactermia) move to organs beyond the skin.

Folliculitis Epidemiology

-S. Epidermis lacks viruleunce and rarely causes diseases.

-S aureus colonizes the skin or mucous membrane of most people

Folliculitis (Diagnosis)

-Isolation of Gram Positive Bacteria in grape like cluster from pus.

Folliculitis (Treatment)

Dicloxacillin(semisynthetic penicillin resistant to break down by beta lactams)

Vancomycin- is used to treat resistant strains

Folliculitis (Prevention)

-Hand antiseptsis

-Proper procedures in hospitals to miminize MRSA infections

Staphylococal Scalded Skin Syndrome

-skin becomes red, wrinkled, and forms blisters typically begins around the mouth.

-outer epidermis starts peel off in sheets.

Pathogenic and Virulence Factors:

some staphylococus straints

-one or two different exfoliative toxins.

Pathogensis:

-No scarring because dermis is unaffected

-Death mis rare may due to secondary infections

Epidemiology:

disease occurs primarily in infants and children under the age of 5.

transmitted by person to person.

Diagnosis, Treatment, and Prevent:

-Disagnosed by characteristic sloughing of the skin

-treated by administration of antimicrobial drugs and supportive care of damage and exposed skin.

-Wide spread of S aureus makes prevention diffcult.

Impetigo and Erysipelas

Impetigo: red patches form on the face and limbs—> pus filled blisters—→ honey colored crusts.

Erysipelas: infection spreads to your lymph nodes.

Pathogen and virulence Factors:

Most causes of impetigo is s aureus.

streptoocus pyogenes: can cause some impetigo, but is primarily the cause of erysipelas.

virulence factors that contribute to impetigo:

-M protein: inteferes with phagocyocytsis of immune cells.

-Hydluronic Acid Capsule: camoflage

Pyrogenic Toxins: increase inflammatory cytokine release

Pathogenesis:

-The bacteria invades where the skin is comprised.

Acute Glomerulonephritis: can result if the infection spreads to the kidney.

Epidemiology:

-Transmitted to person to person contact or via fomites.

Impetigo occurs most in children

Epysipelas can also occur in the eldery

Diagnosis, Treatment and Prevention:

-The presence of vescicles is a diagnostic for impetigo.

Impetigo can be treated with oral and topical antibotics careful cleanings of the infected area.

-Erysipelas is treated with pencillin.

-Prevent with proper hygiene and cleanliness

Necrotizing Fasciitis

-Life threatening; rapid destruction of the body’s soft tissues.

-Pathogen and Viruleunce factors:

most cases are caused by s. pyogenes.

-Various enzymes facilitate the invasion of your tissues.

-Exotoxin A and Streptolysin S damages cells and tissues

Pathogensis and Epidemiology:

S. pyogenes enter through breaks in the skin.

-Usually spread through person to person.

Diagonsis, Treatment, and Prevention:

-Early diagnosis is difficult because the symptoms are non specific.

-Requires immediate surgery and treatment with clindamycin and pencilin.