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51 Cards in this Set
- Front
- Back
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Chickenpox (Varicella): MOA
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Viral: Member of the herpesvirus
-enveloped, double-stranded DNA -Enters body through respiratory route -Replicates and disseminates to the skin via the blood stream. |
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Chickenpox (Varicella): Signs and Symptoms
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Signs and Symptoms:
-Rash begins as macules turning to papules in 1-2 days. -Thin-walled fluid filled vesicles turn cloudy, dry up, crust over. -2-3 weeks after infection a slight fever develops -Skin lesions appear on the back and trunk spreading to the face, neck and limbs. (Severe cases spread to mouth, pharynx, and vagina) |
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Shingles (Herpes zoster): MOA
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Viral: Can enter the sensory nerves
-Expression of viral genome is suppressed -Stress, aging, or immune suppression can reactivate -Infectious varicella-zoster virus replicates in the nerve cell nuclei and carried to the skin by cytoplasm of nerve cell |
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Shingles (Herpes zoster): Signs and Symptoms
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Signs and Symptoms:
-A painful skin rash develops near the distal end of the nerve -Lesions are localized along a band of skin that is innervated by a single sensory nerve |
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Measles (Rubeola): MOA
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Viral: rubeola virus
Single-stranded RNA virus belonging to the paramyxovirus family Viral envelope has 2 biologically active projections H- for viral attachment to host cells M- fusion of the viral outermembrane with the host cell -Acquired by respiratory route -Assumed to replicate in the upper respiratory epithelium -Spreads to lymphoid tissues and then to all parts of the body -Skin rash results from viral replication in skin cells and cellular immune response |
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Measles (Rubeola): Signs and Symptoms
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Signs and Symptoms:
- Fever, sore throat, headache, dry cough, conjunctivitis - After 2 days, lesions called Koplik’s Spots appear on mucous membrane of the mouth - Look like grains of salt surrounded by red halo - Maculopapular lesions appear on head and spread over the body - Lesions are extensive and fuse to form red patches |
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Measles (Rubeola): Complications
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Rare complications
- Pneumonia, encephalitis - Subacute sclerosing panencephalitis (SSPE) -- Progressive disease of the CNS -- Involves personality changes, memory loss, muscle spasms, blindness -- Caused by a defective measles virus that cannot make a capsid -- Moves from brain cell to brain cell via cell fusion -- Disease begins 1-10 years after initial measles infection |
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Smallpox: MOA
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Viral: Double-stranded DNA virus belonging to the Poxviridae family
- Enveloped virus, brick-shaped Variola major -Severe and more common form -Mortality rate is 20% or higher Variola minor - Milder, less common - Mortality rate less than 1% |
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Smallpox: MOA cont...
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- Close contact necessary for infection (unstable envelope)
- Inhalation of viruses in droplets or dried crusts - Crusts can remain infective for up to 2 years - Smallpox viruses replicate in respiratory tract and spread via blood and lymphatic system (contrast with chickenpox) - Characteristic skin lesions appear about 12 days after exposure |
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Smallpox: Signs and Symptoms
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Signs and Symptoms:
- No symptoms first 12 days - Fever, body aches appear lasting 2-4 days - Followed by rash which becomes raised bumps developing into pustules which scab over - An individual is contagious from the onset of the rash until the last scab falls off - Most contagious during the first week -Vaccine is available -3/10 people on average die -NOTE: There is no treatment for smallpox |
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Warts: MOA
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Viral: papillomaviruses - 60 different strains cause warts
- Infect the skin through minor abrasions - Nipple-like protrusions of tissue covered by skin or mucous membrane - Viruses infect the deep cells of the epidermis and reproduce in the nuclei - Infectious virus is present in the wart and can contaminate objects that rub against the lesions - Infects cutaneous or mucosal tissues causing infected epithelial cells to divide. - Some strains integrate into host cell chromosomes -potential for triggering cancer |
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Warts: Treatment
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- Treatment is usually accomplished by freezing the wart with liquid nitrogen, cauterization, or surgical removal
- Warts usually regress over time -- Cell mediated immune system recognizes and attacks virally infected cells |
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Superficial cutaneous mycoses
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Living tissue is not invaded
Lack of cellular response from host (unaware) Invades hair and keratinized portion of the skin |
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Tinea versicolor
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Fungal: Malassezia furfur
- Lipophilic - Can cause skin problems such as scaly rash, dandruff, or Tinea versicolor: a patchy scaliness with Increased pigmentation in fair-skinned individuals or Decreased pigmentation in dark-skinned individuals - Implicated in the cause of seborrhoeic dermatitis and dandruff |
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Dermatophytosis
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Fungal: Cutaneous Mycoses -Dermatophytes: Epidermphyton, Microsporum, Trichophyton
- Under moist conditions, dermatophytes can invade keratinized structures using a keratinase to dissolve keratin and use it as nutrient - Do not grow at 37deg C and do not penetrate deep skin layers |
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Ringworm
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Fungal: Dermatophyte infection
Cutaneous Mycoses Symptoms: - Rash at site of infection consisting of scaly area surrounded by redness and producing irregular rings or lacy pattern on skin - Involved nails become thickened and brittle - Patchy areas of hair loss on scalp |
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Candida skin invasion
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Fungal: Candida Albicans
Cutaneous mycoses - Normally resident flora on human skin - Cause for invasion cannot be determined |
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Subcutaneous Mycoses
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Chronic, localized infections of skin and subcutaneous tissues
- Caused by traumatic implantation of the etiologic agent - Causative agents are soil saprophytes - Incidence for these fungal infections are rare - More common in bare-footed populations living in subtropic and tropical regions |
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Chromoblastomycosis
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Fungal: Subcutaneous mycoses
Dematiaceous (means dark) fungi Rounded, sclerotic bodies |
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Phaeohyphomycosis
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Fungal: Subcutaneous mycoses
Dematiaceous fungi Tissue morphology mycelial |
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Mycetoma
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Fungal: Subcutaneous mycoses
Acremonium, Aspergillus Hard nodule which softens and ulcerates Discharge of viscous, purulent fluid |
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Rose Gardener's Disease
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Fungal: Subcutaneous mycoses
Sporotrichosis - Associated with puncture wounds from vegetation - Usually a hand or arm is involved - Chronic ulcer forms at the wound site - Lymph nodes enlarge - Caused by the dimorphic (mold and yeast forms) fungus: Sporothrix schenckii - Occupational disease of farmers, carpenters, gardeners, greenhouse workers |
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Psoriasis
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Chronic inflammatory skin disorder
- Environmental, stress factors can trigger this inflammatory response -- In genetically, predisposed individuals - Increased keratinocyte proliferation -- Keratinocyte cell cycle shortened - Plaque-type psoriasis -- Scaly, erythematous, pruritic -- Involves scalp, elbows, knees, other body areas -- Capable of spreading and involving a large percentage of the body surface area (BSA) |
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Staphylococcus aureus: MOA
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Leading cause of wound infection
-Makes pus (pyogenic), gram-pos, ana/aerobic, and salt tolerant - Produces coagulase – causes blood to clot (Unique characteristic for S. aureus) - Possesses clumping factor and other virulence factors that aid in the colonization of wounds - Protein A which binds IgG by the Fc portion of the immunoglobulin molecule -- Phagocytes have Fc receptors in order for them to recognize antigen/antibody complexes -- Therefore phagocytosis is inhibited - Alpha-toxin (S. aureus) attaches to host cell membranes and make holes |
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Staphylococcus aureus: MOA cont...
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- Virulence factors help to coat the organisms with host proteins
-- Hides S. aureus from host defenses -- Enables S. aureus to colonize plastics and other foreign materials - S. aureus can spread from wound infections leading to abscesses in other tissues: heart, joints - Toxins produced by S. aureus act as super antigens, causing large release of cytokines producing toxic shock |
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Staphylococcus epidermidis: MOA
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Wound Infections:
Little invasive ability; Can colonize intravenous catheters, heart valves - Once the bacteria adhere to a plastic surface, production of a biofilm begins - The slime or glycocalyx cements the colony to the plastic and protects the bacteria from host defenses and antibiotics - Organisms can come loose from biofilms on plastic catheters and carried by bloodstream to the heart - Results in subacute bacterial endocarditis or multiple tissue abscesses in people with impaired host defenses (Cancer, diabetes) |
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Staphylococcus: Treatment
MRSA |
Treatment:
- Penicillins, cephalosporins resistant to beta-lactamase MRSA - Methicillin-resistant Staphylococcus aureus - Modified penicillin-binding proteins - Treated with vancomycin until the first vancomycin-resistant strain appeared - Synercid – acts to block bacterial protein synthesis |
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Streptococcus pyogenes: MOA
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Group A streptococcal
Virulence factors: - Deoyribonucleases - Streptokinases (dissolves blood clots) - Hyaluronidase (degrades hyaluronic acid between cells) - Toxins: -- Exotoxin A: Overactivates the cell mediated immune system (superantigen) which causes toxic shock - Exotoxin B, a protease, which destroys tissue by breaking down proteins -- Streptolysin S: One of the most potent bacterial toxins know. Able to kill many different types of human cells in the laboratory. Treatment: Penicillin |
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Pseudomonas aeruginosa: MOA
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- Gram-neg rods, motile
- Opportunistic, major cause of nosocomial infections (esp. burn victims) - Facultative anaerobe - Capable of using nitrate substitutes as a final electron acceptor - Produce several water-soluble pigments - more green than anything (pyoverdin + pyocyanin) -Damages tissue, prevents healing, increased risk of septic shock (Circulating pathogens instead of toxins) - Produce proteases that cause localized hemorrhages and tissue necrosis |
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Cutaneous mycoses often result from fungi that utilize this enzyme:
1. Hyaluronidase 2. Coagulase 3. Catalase 4. Keritinase |
Keritinase
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Tetanus: MOA
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Anaerobic Bacterial: Clostridium tetani
-sporeformer, gram-pos rod - Spherical endospore - Produces toxin which is coded by a plasmid called tetanospasmin - Toxin is carried by the cytoplasm of neuron’s axon to its cell body - This neuron is controlled by other neurons which inhibit or stimulate - Tetanospasmin blocks the action of the inhibitory neurons - Therefore the muscles will continually contract - Most causes of lockjaw result from puncture wounds |
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Tetanus: Signs and Symptoms, Prevention, and Treatment
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Signs and Symptoms:
- Characterized by sustained painful, uncontrollable muscle spasms - Often begin in the jaw muscles - Muscles tense, pain increases, breathing is labored - Patient often dies of pneumonia or stomach contents regurgitated into the lungs - Tetanus is preventable through immunizations using an inactivated tetanus toxoid - Tetanus is treated by administering tetanus antitoxin -- Tetanus immune globulin (TIG) -- Wounds are cleaned of dead tissue -- Antibacterial medication such as metronidazole |
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Gas Gangrene: MOA
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Clostridium perfringens (Gangrene)
- Fostered by the presence of dirt and dead tissue in the wound - Delay in getting medical attention - Clostridium perfringens grows easily in dead, necrotic tissue -- Poorly oxgenated, perfect for strict anaerobes - Pathogenicity is due to product of an alpha-toxin, that destroys host cell membranes and will diffuse into the bloodstream causing massive damage throughout the body. - Organisms grow readily in the fluids of dead tissue producing hydrogen and carbon dioxide gas |
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Gas Gangrene: MOA
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Signs and Symptoms:
- Swelling of wound with thin bloody or brownish fluid leaking - Fluid appears frothy due to gas formation by microorganism - Skin appears stretched and mottled with black Treatment: Surgery to remove dead infected tissues is necessary |
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Bacterial Bite Wounds
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Pasteurella multocida:
- Gram-neg rod, facultative anaerobe - Some strains produce a toxin that is cytotoxic - Capsules of this organisms are antiphagocytic - Abscesses - Best known to cause fowl cholera (chicken disease) Best treatment is immediate cleansing of bite wounds Treatment: - P. multocida is susceptible to penicillin - Usually penicillin plus a beta-lactamase inhibitor is administered (amoxicillin) |
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Clostridium perfingens: MOA
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Anaerobic gram-positive rod - spore former
Saprophytic, ubiquitous in soil, infects mucus membranes Produces 20 different exotoxins: - Alpha toxin -- Lethal by hydrolysis of cell membrane: Erythrocytes (hemolytic), Leukocytes, Platelets, Fibroblasts Muscle cells. Lecithinase, necrotizing, cardiotoxic - Theta-toxin: alters capillary permeabliity. Pore forming. Signs: Double zone of hemolysis on blood agar. Inner zone is complete (theta) Outer zone is incomplete (alpha) |
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Cutaneous Leishmaniasis: MOA and Signs and Symptoms
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- Caused by the protozoan parasite, Leishmania
- Spread through the bite of a sandfly |
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Scabies: MOA, Signs and Symptoms, Treatment
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Caused by Mites
MOA: - Adult females deposit eggs as they burrow in skin. - The eggs hatch releasing larvae. - Larvae molt into nymphs found in short molting pouches. - Mating occurs after the male penetrates the molting pouch of the adult female. -- Transmission is by person-to-person and fomites (clothing, bedding) Signs and Symptoms: -- Found predominantly between the fingers and wrists. Also armpits, stomach, genitals, and knees. Treatment: 5% permethrin Lotions |
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Hypersensitivities: Type IV: MOA
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- Response mediated by TH1 cells
-- Recognize antigen presented by MHC II molecules - Involves mononuclear cell infiltration -- Sensitized lymphocytes migrate to the site of inoculation where they undergo blast transformation and proliferation - Sensitized lymphocytes begin to secrete lymphokines which help to increase numbers - Lymphokines -- Soluble products from sensitized lymphocytes which affect other cells |
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Acute Paronychia: MOA
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Inflammation of the nailfolds
- Rapid onset of painful, bright red swelling of the proximal and lateral nailfold due to trauma or manipulation - Superficial infections present with an accumulation of purulent material behind the cuticle A diffuse, painful swelling suggests deeper infection - Commonly caused by Staphylococcus aureus - Cases that do not respond to antibiotics (cephalexin) may require deep incision. - Acute paronychia rarely evolves into chronic paronychia. |
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Chronic Paronychia: MOA, Signs and Symptoms
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Inflammation of the proximal nail-fold.
- Commonly caused by Staphylococcus aureus and streptococci (Mixed infection common) - Evolves slowly and presents initiallly with tenderness and mild swelling - Significant contact irritant exposure is a major cause. Individuals whose hands are repeatedly exposed to moisture are at greatest risk. - Many or all fingers are involved simulatneously. -- Cuticle separates from the nail plate (exposing it for infection) -- Small quntity of pus can be expressed from under the proximal nailfold. |
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Chronic Paronychia: Treatment
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Treatment.
- Avoid exposure to contact irritants and on treatment of underlying inflammation and infection - Keep the proximal nailfold dry. - Topical steroid creams applied bid for up to 3 weeks are more effective than systemic antifungals. |
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Subungual hematoma/Pseudomonas infection: MOA
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Subungual hematoma
- Trauma to the nail unit - Usually caused by blunt impact resulting in accumulation of blood under the nail plate - Repeated exposure to soap and water may cause maceration of the hyponychium and softening of the nail plate - Separation of the nail plate (onycholysis) exposes a damp, macerated space between the nail plate and the nail bed -- Fertile site for the growth of Pseudomonas - The nail plate assumes a green-black color *This presentation may be confused with subungual hematoma but the absence of pain with Pseudomonas infection establishes the diagnosis |
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Herpetic Whitlow: MOA
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Herpes Simplex infection of the fingertip.
Risk as decreased with use of gloves - The appearance and course of the disease resembles that at other body sites - Exception to that is extreme pain due to swollen fingertips - Herpetic fingers infections in AIDS patients may rapidly progress to the complete destruction of nail structures |
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Fungal Nail Infections: General facts
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- Dermatophytes Tricophyton rubrum and Tricophyton mentagrophytes are responsible for most fingernail and toenail infections
- Candida sp. can also infect the nail plate - Toenail infections occur in 15% to 20% of the population between 40 and 60 years of age. -- May also occur in children. - Trauma predisposes to infection |
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Four patters of nail infection:
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There are four distinct patterns of nail infection:
- Several patterns of infection may occur simultaneously in the nail plate -- Proximal subungual onychomycosis -- Distal subungual onychomycosis -- Candida onychomycosis (distal end of nail plate) -- White superficial onychomycosis (Trichophyton rubrum, Tricophyton mentagrophytes, Aspergillus, Cephalosporium, Fusarium, and Scopulariopsis invade the nail plate in any pattern) |
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Distal Subungual onychomycosis:
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Most common pattern of nail invasion
- Fungi invade the hyponychium, the distal area of the nail bed. - The distal nail plate turns yellow or white due to accumulation of hyperkeratotic debris - Causes the nail to rise and separate from the underlying bed - Fungus grows in the substance of the plate, causing it to crumble and fragment |
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White superficial onychomycosis
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Caused by surface invasion of the nail plate
- By Tricophyton mentagrophytes - The surface of the nail is soft, dry, and powdery and can be scraped away - The nail plate is not thickened and remains adherent to the nail bed |
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Proximal subungual onychomycosis
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- Microorganisms enter the posterior nailfold-cuticle area, migrate to the underlying matrix, and finally invade the nail plate from below
- Infection occurs within the substance of the nail plate, but the surface remains intact - Hyperkeratotic debris accumulates and causes the nail to separate -- Transverse white bands begin at the proximal nail plate and are carried distally with outward growth of the nail plate - Tricophyton rubrum is the most common cause - This is the most common pattern seen in patients with AIDS |
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Candida onychomycosis: MOA, Signs and Symptoms, Treatment
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Nail-plate infection caused by Candida albicans
-- Generally involves all of the fingernails -- Nail plate thickens and turns yellow-brown. -- There are many other patterns of infection. -- Linear, yellow, or dark brown streaks appear at the distal end and grow proximally in some pattern -- Some or all of the nail plate may appear yellow in these areas, the nail can be separated from the underlying bed Treatment: - Oral itraconazole (Sporanox) or Terbinafine - Topical -- Ciclopirox -- Topicals are effective only if used in conjunction with oral therapy or as a prophylaxis |
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Clostridium perfinges produces a toxin which hydrolyzes lecithin and sphyingomyelin so that ________.
1. DNA replication is inhibited 2. Cell membranes are disrupted 3. Protein synthesis is disrupted |
Cell membranes are disrupted
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