Skin Wounds and Infections
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| Normal Skin Flora | w/in superficial epidermis and upper part of hair follicle; Stapylococcus, Micrococcus; Diptheroids; Fungi
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| Skin Staphylococci | Salt tolerant, universally present, prevents colonization; Staph epidermidis and the potential pathogen: S. aureus (on face/hands of nasal carrier; coagulase +)
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| Skin Diptheroids | Corynebacterium (Proprionibacterium acnes); G+, low virulance, associated with acne and body odor (their named b/c they resemble diptheria bacilli)
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| Skin Fungus | Malassezia furfur; yeast; lipophilic
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| P. acnes | anaerobic G+; grows in hair follicles; loves sebum that causes microcomedomes (black/whiteheads)
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| Folliculitus - minor infx of hair follicle | Staph aureus and Pseudomonas aeruginosa in areas of sweat gland activity and friction; Pseudomonas infx commonly ocur from hot tubs
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| Furuncle (boil; stye) | Staph. aureus attaches to follicle, multiplies and spreads down to involve the sebaceous gland; complication of acne vulgaris
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| Carbuncle | spread of furuncle infx to adjacent subcutaneous tissues; can lead to bacteremia
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| Chronic furunculosis | repeat boil episodes; delayed-type hypersensitivity is responsible for inflammation/necrosis; associated w/depressed host immunity (defected PMN fxn)
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| The Virulence of Staph Aureus | due to cell wall compenent PROTEIN A (prevents Ab binding and phagocytosis); Leukocidin destructive enzymes directed against host (Hyaluronidase - breaks tissues apart, proteases, lipases - helps hair follicle colinization)
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| STREPTOcoccal Impetigo | Group A Streptococcus (also staph aureus); characterized by PUS production on suferficial skin; yellow infected crusts weep; lymph nodes enlarge; Streptococcus pyogenes complication - glomerulonephritis
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| Acute Glomerulonephritis | comlication of Strep pyogenes pyoderma; immune complexes are deposited in glomeruli; inflammatory rxn causes tissue damage
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| Cellulitis | Grp A Strep and S. aureus (in infants - Haemophilus influenzae); acute inflammation of subcutaneous CT (fat)
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| Staphylococcal Scaled Skin Syndrome (SSSS) | Certain strains of S. aureus; production of EXFOLIATINS spreads thru blood to cause large areas of keratinized epidermis to detach; Secondary problems: dehydration and infection (Pseudomonas or Candida albicans)
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| Rocky Mountain Spotted Fever | Rickettsia rickettsii; from tick bite; sudden onset of flu-like symptoms and spotted rash spreads from extremities to body core; humans are accidental host
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| Lyme Disease | Borrelia borgdorferi; spirochetes from tick cause inflammatory rxn and spread thru circulation; flu-like symptoms, arthritis, chronic nervous system symptoms; ERYTHEMA MIGRANS...it moves...
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| Stage 1 Lyme Disease | erythema migrans on skin, lymph nodes
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| Stage 2 Lyme Disease | heart, CNS, PNS (like a Bell's Palsy)
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| Stage 3 Lyme Disease | Chronic arthritis; depresson; paralysis
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| Cat Scratch Disease | Bartonella hensalae; G- bacilli; vectors: domestic cats, cat flea, body louse (pediculus humanus coporis), ticks); febrile lympadenitis; rashes; conjunctivitis; encephalitis; prolonged fever
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| Dx and Tx of Cat Scratch Disease | serologic response to Bartonella henselae antigens; azithromycin or erythromycin...Associated with AIDS pts
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| Anthrax | Bacillus anthracis; spore-former G+ rod facultative anaerobe; non-hemolytic; non-mobile; contamination from infected livestockor animal products
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| 3 Routes of Acquisition | 1. Inoculation - 95% of cases through exposed skin; 2. Ingestion - rare in humans (herbivore route); 3. Inhalation - woolsorter's disease or terroristic
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| Cutaneous Anthrax | spore introduced through cut, abrasion, insect bite; incubates 2-7 days; papules surrounded by vesicles; vesicular ring ruptures; central black necrotic region forms
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| Scarlet Fever | Grp A Strep; rash w/ itchy bumps on face/neck, chest/back, then entire body; rash peels on 6th day; Strawberry Red Tongue
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| Varicella | dsDNA virus from herpes family; red bumps/blisters erupt into pustules that break and leak virus into fluid filled crusts that later heal; Respiratory transmission and spreads through blood; virus can enter sensory nerves (Shingles)
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| Varicella zoster | occurance of shingles related to decreased cell-mediated immunity (aging); replication in nerve cell nuclei and is carried by cytoplasm along dermatome; AIDS pts can have shingles all over body
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| Measles | ssRNA Rubeola virus of paramyxovirus family; viral envelope H and M projections (attachment/fusion); Respiratory transmission; replicates in upper respiratory epithelium, spreads to lymphoid tissue, then body; rash from viral replication in skin cells
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| Smallpox | dsDNA variola virus from poxviridase family; enveloped/brick-shape; Major (common/severe) and minor (milder, rare) forms
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| Smallpox - Variola Major | 1. ordinary - 90%; 2. modified - milder in vaccinated pts; 3. flat - rare/severe; 4. hemorrhagic -rare/severe; Last case in US 1949, in world 1977
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| Smallpox symptoms | up to 17 days w/o symptoms, then flu-like for 2-4d followed by rash/pustules/scab; contagious from onset of rash till last scab falls off; no Tx; 30% die; ANY case now would be an emergency!!
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| Warts | Papillomaviruses; infection thru abrasions; nipple-like protrusions covered by skin or mucous membrane; virus replicates in nuclei deep in epidermis; Tx: freezing/cauterization/surgery
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| Superficial cutaneous mycoses | fungal skin infections; living tissue not invaded; only hair, nails, keratinized skin; lack of cellular response from host; no pathological changes elicited
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| Tinea capitus, barbae, axillaris, corporis, cruris, pedis | scalp, beard, armpit, body, groin, feet
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| Malassezia furfur | lipophilic...requiring oil from hair follicles; can cause a scaly rash, dandruff, tinea versicolor, seborrhoeic dermatitis
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| Tinea versicolor | Malassezia furfur; patchy scaliness with increased/decreased pigmentation in fair/dark-skinned individuals
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| Cutaneous mycoses | Candida (yeast) and Dermatophytosis (epidermophyton, microsporum, trichophyton); under moist conditions dermatophytes can invade keratinized structures via keratinase; don't grow at 37C; pathogenesis dependent on virulence and moisture
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| Ringworm - cutaneous | dermatophyte; red, scaly, lacy rings on skin; thick/brittle nails; patchy hair loss
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| Diaper Rash -cutaneous | Candida albicans; normal resident of human skin
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| Subcutaneous | chronic, localized infx of skin/subcut tissue d/t traumatic implantation of agent from soil saprophytes
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| Chromoblastomycosis - subcutaneous | dematiaceous fungi; rounded, sclerotic bodies
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| Phaeohyphomycosis - subcutaneous | dermaticaceous fungi; tissue morphology mycelial
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| Mycetoma - subcutaneous | Acremonium, Asperigillus; hard nodule which softens and ulcerates; discharge of viscous, purulent fluid
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| Rose Gardner's Disease - subcutaneous | Sporothrix schenckii (dimorphic fungus: mold/yeast forms); d/t puncture wounds in garden in upper extremitiy; chronic ulcer and enlarged lymph nodes
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| Psoriasis | Chronic inflammatory skin disorder; genetic; increased keratinocyte proliferation d/t shortened cell cycle; Plaque-type: scaly erythematous, pruritic on scalp, elbows, knees and more
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| Staphylococcal Wound Infections | G+; pyogenic - pus producing; grow in aerobic and anaerobic conditions and can spread to surrounding tissues to form abscesses; Virulence factors: coagulase, protein-A, alpha-toxin
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| Staph Protein A | binds IgG by Fc protein on immunoglobulin to inhibit phagocytosis
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| Staph alpha-toxin | used to attach to and porforate host cell membrane
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| Group A Streptococcal "Flesh Eaters" | Strep pyogenes; usually susceptible to penicillin; can progess to severe infx (pneumonia, meningitis, necrotizing fasciiis, strep toxic shock)
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| Strep toxins - Exotoxin A | pyogenic superantigen that causes toxic shock
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| Strep toxins - Exotoxin B | protease
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| Necrotizing Fasciitis | Strep. pyogenes; colonization and destruction of fatty tissues; fluid buildup/infx produces toxic products; Tx: Removal of diseased tissue/toxins
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| Pseudomonas aeruginosa | opportunistic pathogen; nosocomial infx, esp burn victims (some community acquired in pools, too); Forms biofilms in lungs of CF pts; difficult to Tx
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| Burns and Pseudomonas | G- rods, motile, facultative anaerobe (Nitrate final e acceptor); turns wound a GREEN color with a sweet smell; tissue damage prevents healing; septic shock from circulating PATHOGENS (not toxins like strep/staph)
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| Tetanus "lock-jaw" | Claustridium tetani; G+ spore-forming anaerobic; plasmid produces toxin; muscle spasm in jaw; pt can die from pneumonia when stomach contents is aspirated
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| Tetanus - tatanospasmin exotoxin | blocks inhibatory neurons for muscle contraction; continuous contraction ensues;
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| Tetanus - cause/Tx | puncture wounds; prevent via immunizations if inactivated tetanus toxoid; Tx: tetanus antitoxin (TIG - tetanus immune globulin); clean dead tissue, metranidazole
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| Gas Gangrene | Clostridium perfringens - grows in dead anaerobic tissue (clostridial myonecrosis); results from neglected wounds containing debride; black swelled/streched skin with leaky bloody/brown frothy fluid d/t gas production; Sx necessary to remove dead tissue
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| Clostridium perfrigens | G+ spore-forming obligate anaerobe; saphophytic (loves dead tissue); 20 different exotoxins (alpha (outer) and theta (inner) leave double hemolysis zone on blood agar)
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| Clostridium pefringens exotoxins - Alpha-toxin | necrotizing; lecithinase hydrolyzes lecithin and sphingomyelin (egg-yolk agar); hydrolyzes key components in cell membrane; RBCs, WBCs, platelets, fibroblasts, muscle cells; most important virulent factor
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| Clostridium perfringens exotoxins - Theta-toxin | alters capillary permeability; toxic to heart muscle; pore-forming; loss of cellular fluid
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| Bacterial bite wounds | Pasteurella multocida; G- rod, facultative anaerobe; causes fowl cholera; capsules are antiphagocytic and form abscesses; Tx with penicillin plus a b-lactamase inhibitor (amoxicillin)
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| Cutaneous Leishmaniasis | protozoan parasite Leishmania from sand fly bites; can cause localized ulcer/nodule
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| Scabies | Sarcoptes scabiei; mite burrows into epidermis and feeds/lays eggs for 1mo; rash from allergy forms; Dx by identifying mite; rash is itchy on hands btw fingers, under breasts and in genital areas
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| Staphylococcus epidermidis | little invasive ability; glycocalyx slime protects its colonies on catheters, etc; can get into blood and cause subacute bacterial enteritis in diabetic or cancer pts
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| Treatment of staph infx | penicillins, cephalosporins resistant to b-lactamase, MRSA - vancomycin or Synercid
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