Slide 1Structure of the SkinDefenses That Protect the SkinWoundsNormal Microbiota of the SkinFolliculitis – Pathogen and Virulence FactorsFolliculitis – Pathogen and Virulence FactorsFolliculitis – Pathogen and Virulence FactorsFolliculitis – Pathogen and Virulence FactorsFolliculitis – Pathogen and Virulence FactorsFolliculitis – PathogenesisFolliculitis – Signs and SymptomsFolliculitis – EpidemiologyFolliculitis – DiagnosisFolliculitis – TreatmentFolliculitis – PreventionRocky Mountain Spotted Fever – Pathogen and Virulence FactorsRocky Mountain Spotted Fever – PathogenesisRocky Mountain Spotted Fever – Signs and SymptomsRocky Mountain Spotted Fever – Signs and SymptomsRocky Mountain Spotted Fever – EpidemiologyRocky Mountain Spotted Fever – EpidemiologyRocky Mountain Spotted Fever – DiagnosisRocky Mountain Spotted Fever – TreatmentRocky Mountain Spotted Fever – PreventionChickenpox/Shingles – PathogenChickenpox/Shingles – PathogenesisChickenpox/Shingles – Signs and SymptomsChickenpox/Shingles – Signs and SymptomsChickenpox/Shingles – Signs and SymptomsChickenpox/Shingles – Signs and SymptomsChickenpox/Shingles – EpidemiologyChickenpox/Shingles – DiagnosisChickenpox/Shingles – TreatmentChickenpox/Shingles – PreventionM I C R O B I O L O G YWITH DISEASES BY BODY SYSTEM SECOND EDITIONChapter 19Microbial Diseases of the Skin and WoundsStructure of the Skin•Two main layers–Dermis–Epidermis•Functions of the skin–Prevents excessive water loss–Important to temperature regulation–Assists in the formation of vitamin D–Involved in sensory phenomena–Barrier against microbial invadersDefenses That Protect the Skin•Outermost layer of skin – flattened, dead, dry, keratinized •Covered with salt and sebum–Contain antimicrobial chemicals•Sloughing of skin removes microbesWounds•Trauma to any tissue of the body– Cuts, abrasions, scrapes, surgery, inoculations, bites, and other penetrating wounds, as well as burns•Allow microbes to infect the warm, moist deeper tissues of the body•Dirty wounds provide platforms for growth of biofilms•Body forms a clot and then neighboring cells multiply and grow into the clot–In most cases other body defenses including phagocytosis, complement, and inflammation eliminate the infection•Wound infections can result in severe or fatal diseasesNormal Microbiota of the Skin•Normal flora compete with potential pathogens for nutrients and space, and produce chemicals that interfere with the growth of other microbes–Cannot be completely removed through cleansing–Typically grow in small clusters in moist areas–Waste products produce body odor•Prominent members–Malassezia–Staphylococcus–Micrococcus–Diphtheroids•Pathogenic microbes can still produce diseases, particularly if they penetrate the epidermis through wounds, or when the immune system is suppressedFolliculitis – Pathogen and Virulence Factors•Most commonly caused by members of the genus Staphylococcus –Facultatively anaerobic, Gram-positive cocci, in clusters•Tolerant of –Salt–Desiccation–Solar radiation–HeatFolliculitis – Pathogen and Virulence Factors•Two species commonly found on the skin and mucous membranes–Staphylococcus epidermidis–Staphylococcus aureus•S. epidermidis–Accounts for up to 90% of bacteria on skin–Major member of microbiota•S. aureus–More virulent–Often grows in nasal passages–Produces variety of disease conditions and symptomsFolliculitis – Pathogen and Virulence Factors•Have at least three categories of virulence factors:•Enzymes–Coagulase – immunological disguise–Hyaluronidase – promotes spread–Staphylokinase – promotes spread–Lipases – provides source of nutrition on surface of skin–β-lactamase – resistance to some antibiotics•Structural Defenses Against Phagocytosis–Capsule – inhibits chemotaxis and phagocytosis by WBC; facilitates attachment to artificial surfaces–Protein A – inhibits opsonization and complement cascadeFolliculitis – Pathogen and Virulence Factors•Toxins (produced by strains of pathogenic S. aureus)–Cytolytic toxins – damage cytoplasmic membranes–Leukocidin – kills leukocytes–Epidermal cell differentiation inhibitor – induces holes in the linings of blood vessels; invasion into tissues–Exfoliative toxin – dissolution of epidermal desmosomes (promotes spread)–Toxic shock syndrome toxin – causes over-activation of T cells and results in overabundance of cytokines that produce vast array of signs and symptomsFolliculitis – Pathogen and Virulence FactorsFolliculitis – Pathogenesis•Transmitted among humans via direct contact and via fomites•Organism grows into hair follicles and invades sebaceous glands•Inflammation and fever develop•Follicle enlarges and fills with pus–May spread into hypodermis to form furuncle–May spread into neighboring hair follicles to form a carbuncle•S. aureus (infrequently S. epidermidis) can cause bacteremia and be carried around the body–Endocarditis–Pneumonia–OsteomyelitisFolliculitis – Signs and Symptoms•Infection of the hair follicle–Often called a pimple•Called a sty when it occurs at the eyelid base•Spread of the infection into surrounding tissues can produce furuncles (boils)•Carbuncles occur when multiple furuncles grow together•Fever may occur in severe casesFolliculitis – Epidemiology•S. epidermidis is ubiquitous on human skin–Seldom causes disease because it lacks virulence factors–Can be an opportunistic pathogen in immunocompromised patients or when introduced into the body via catheters or prosthetics•S. aureus is not a permanent resident but does grow on skin and mucous membranes (nostrils) at some point in most people’s lives–S. aureus often transferred from the face to other locations on the body–20% carry the bacterium for >1 year with no symptoms•Proper handwashing and aseptic techniques are essential in preventing their transfer in health care settingsFolliculitis – Diagnosis•Detection of Gram-positive bacteria in grapelike arrangements isolated from pus•Positive coagulase test for S. aureus•Coagulase-negative staphylococci are usually S. epidermidis and not indicative of a staphylococcal infectionFolliculitis – Treatment•Critical to clean and drain abscesses of pus before topical antibiotic therapy–Hot, moist compresses may promote drainage