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117 Cards in this Set
- Front
- Back
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What is found in the epidermis?
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Fixed tissue macrophages, no vessels or nerves
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Where are many superficial infections located?
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Hair follicle
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What predisposes the dermis to infection?
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Rich plexus of blood vessels interrupts the tissue
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What provide a waterproof barrier for the skin?
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Keratinocytes
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What four species are common flora on dry, exposed skin?
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Staph epidermidis
Corynebacterium sp. Proprioibacterium sp. Malassexia furfur Simple Cancers Pardon Mobsters |
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What kinds of bacteria are normal flora in the groin, axilla, web of toes?
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Gram neg rods
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What are the three types of spreading infections from superficial to deep?
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Impetigo
Erysipelas Cellulitis |
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What are the three types of abscesses (often caused by S. aureus) from least to most severe?
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Folliculitis
Furuncles (boils) Carbuncles (clusters of furuncles) |
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What are the two types of necrotizing infections from least to most severe?
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Fasciitis
Gangrene |
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What are two species that result in internal infection that spread outward in necroses?
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N. meningitidis
P. aeruginosa |
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What does the catalase test examine?
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Ability to convert H2O2 to water and oxygen
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What test is used to distinguish staphylococci?
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Coagulase test
Positive--> S. aureus Negative--> lots, may be S. saprophyticus (UTIs) or S. epidermidis |
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What is the main goal of S. aureus once it starts to establish infection?
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Avoid PMNs
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What is the main lesion that is caused by S. aureus?
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Abscess
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What does agr gene regulation in S. aureus control? How?
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Quorum sensing used to determine what to express...during growth, see a lot of adhesins and during stationary phase see a lot of toxins being made
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What does protein A in S. aureus do?
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Stops opsonization --- incapacitates antibody function
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Name three important enzymes that are virulence factors for S. aureus.
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Catalase
Coagulase Hemolysins |
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What do virulence factors of S. aureus exfoliative toxins A or B cause?
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Split of extracellular bridges in stratum granulosum epidermis
Sloughing of skin, bullous impetigo, scalded skin syndrome |
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What is the leading cause of bacteremia in the U.S. and the cause of 50% of all skin infections?
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Staph aureus
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What is the key clinical feature of toxic shock syndrome?
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deep-red sunburn rash that desquamates
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What gene is responsible for the massive resistance that much S. aureus has?
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mecA
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What are two characteristics of community-axquired methicillin-resistant staph aureus (CA-MRSA) that are worrisome?
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Panton-Valentine leukocidin
PSM peptides |
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What problems do coagulase negative staph create?
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Biofilms on plastic foreign bodies in people
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What does S. saprophyticus cause?
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UTIs in young women
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What environment is vibrio vulnificus found in?
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Warm marine waters
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What is the biggest virulence factor of vibrio vulnificus?
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Polysaccharide capsule
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What is the most virulent of the non-cholera vibrios?
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Vibrio vulnificus
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What are three groups of people that are most at risk for serious infection with vibrio vulnificus?
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Immunocompromised, cirrhosis, hemochromatosis
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What are two routes of infection caused by vibrio vulnificus?
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Septicemia and bacteremia due to cellulitis
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How many days after ingestion of raw seafood do the necrotizing lesions show up in vibrio vulnificus infection?
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1-3 days
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What are the gram negative rod anaerobes?
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B. fragilis
Fusobacterium Preyotella Porphyromonas |
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What are the gram positive cocci anaerobes?
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Peptostreptococcus
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What is the gram positive rod anaerobe?
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Clostridium
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Name some anaerobes found in the oral cavity, intestines, and female genital tract.
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Fusobacterium
Prevotella Prophyromonas Peptostreptococcus |
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What is one way to distinguish an infection involving anaerobes?
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Smells bad and there is often a mixed morphology of anaerobes and aerobes
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What kind of infection is usually involved in bite wounds?
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Anaerobes
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What anaerobe is indicative of underlying colon cancer if found in the bloodstream?
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Clostridium septicum
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What is the standard anti-anaerobic antibiotic?
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Clindamycin
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What are some of the virulence factors of B. fragilis?
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Adhesins
Antiphagocytic capsule Succinic acid Enterotoxin Enzymes |
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What complication are you less likely to see with B. fragilis despite its toxin? Why?
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Less likely to see shock or DIC because toxin lacks lipid A
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Where in the body is B. fragilis found?
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Bowel
NOT oropharynx |
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What types of infections is B. fragilis involved in?
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"Below the waist"
Abscess Decubitous ulcer Diabetic ulcer Osteomyelitis Post-surgical wounds (abodominal, pelvic) |
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What do you treat B. fragilis with?
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Metro or clinda (produces a beta-lactamase)
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What does clostridium perfringens look like on gram stain?
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Box-car GPB
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What toxin is made by C. perfrigens and what does it do?
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Alpha-toxin lecithinase
Damages membranes of WBCs, RBCs, platelets, endothelial cells |
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What types of skin infections is C. perfringens often found in?
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Those with mixed flora - wound infections, perirectal abscesses, diabetic food and decubitus ulcers
Crepitant cellulitis Fasciitis myositis |
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What is a rare but serious complication of C. perfringens skin infection?
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Gas gangrene
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What are the 3 treatments for gangrene?
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Surgical removal of affected tissue
Antibiotics Hyperbaric oxygen |
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What is the oxygen requirement of C. tetani?
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Strick anaerobe
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What is the exotoxin produced by C. tetani? How does it work?
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Tetanospasmin (trophic for CNS, blocks inhibitors)
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What is the incubation period of C. tetani?
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8 or so days (less the closer to the CNS it is)
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What are the four types of tetanus?
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Generalized
Localized Cephalic Neonatal |
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What are the first two noticeable symptoms of tetanus? What does this look like?
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Trismus and risus sardonicus
Masseter rigidity then increased tone in orbicularis oris -- look like grinning because of muscle spasm |
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How long do the symptoms of tetanus last?
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2 weeks with antitoxin
1 or more months without |
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How long does active immunization with DaPT last?
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around 10 years
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What organism that causes SSTM infections is not culturable?
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M. leprae
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What is the avg incubation period for leprosy?
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2-4 years
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What immune response does lepromatous leprosy invoke?
What is found in these lesions? |
TH2
IL-4,5,10 |
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For which type of leprosy may patients be agammaglobulinemic?
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LL
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What is the main cell type involved in immune response to lepromatous (multibacillary) leprosy? What does this result in?
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Macrophages
Granuloma formation |
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Which form of leprosy reacts to lepromin?
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Tuberculoid (paucibacillary) leprosy
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What type of immune response is stimulated by tuberculoid (paucibacillary) leprosy?
What is found in the lesions? |
TH1
IL-2, TNF-beta, IFN-gamma |
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What is seen histologically in tuberculoid leprosy?
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Giant cells
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Which type of leprosy has the best prognosis?
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Tuberculoid (paucibacillary) leprosy
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What is the most common method of transmission of leprosy?
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Respiratory
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How many lesions are present in each type of leprosy?
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More than five in multibacillary (LL), less than five in paucibacillary (TT)
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Which type of leprosy has asymmetric lesions that scale?
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Tuberculoid leprosy
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What is claw hands a complication of?
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Leprosy
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Patient from Mozambique presents with skin lesions and enlarged peripheral nerves. What should be in your differential diagnosis?
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Leprosy
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Patient presents with hypoesthetic skin lesions (no sensation) after traveling the world. What is in your differential diagnosis?
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Leprosy
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What organism would you see on an acid fast stain but not be able to culture?
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M. leprae
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What do you use to treat leprosy?
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Dapsone, Clofazimine, Rifampicin
--Dapper Clothes Ruffle |
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What is something that causes infections that look like Nocardia and are frequently gotten after minor trauma in water?
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Mycobacterium marinum
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What is the treatment for Mycobacterium marinum?
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Extended antibiotics (18mo)
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What is a characteristic of all mycobacterium?
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Facultative intracellular
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What is an infection obtained in nail salons?
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Mycobacterium fotuitum, chelonae, or abscessus (rapid growers)
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What does M. furfur bind to? What type of organism is it?
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A yeast
Binds to lipid-rich areas of the skin (e.g. sebaceous glands) -- only to outer layers |
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What is the most common superficial mycosis infection in the U.S.?
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Pityriasis versicolor (caused by M. furfur)
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What type of lesions are caused by M. furfur in pityriasis versicolor?
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Hypo- or hyper-pigmented, seen on trunk, scale easily and are itchy
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What does M. furfur look like when found in lesions?
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Spaghetti and meatballs
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What do dermatophytes cause?
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Cutaneous mycoses - Ringworm
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What type of organism causes ringworm?
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Monomorphic filamentous mold
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What does microsporum infect?
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Hair and skin
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What does trichophyton infect?
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Hair, skin, and nails
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What does epidermopyton floccusom infect?
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Skin and nails
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What type of immune response resolves cutaneous mycoses?
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CMI
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What areas of the body are most commonly infected by cutaneous mycoses?
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Feet, groin, scalp, nails
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What is tinea unguium? What is unique about it?
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Ringworm of the nail
Hardest ringworm to treat |
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What are two ways to diagnose ringworm?
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Woods lamp
KOH+microscope (+calcofluor) |
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What is the main subcutaneous fungal infection in the U.S.?
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Sporothrix schenckii
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What is the structure of sporothrix schenckii?
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Thermally dimorphic fungus
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What type of lesions are seen in sporothrix schenckii infections?
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Papulomacular lesions that ulcerate and often develop raised borders
Usually painless and sometimes followed by secondary lesions along lymphatic channels |
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What are some populations that sporothrix schenckii infections are seen in?
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Rose gardeners
Miners People who handle sphagnum moss |
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What does lymphocutaneous sporotichosis look like?
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Infection with Nocardia, Mycobacterium marinum, or Blasto
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What does extracutaneous sporotichosis most often involve?
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Joints (sometimes lungs)
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What are the 5 classical rashes of childhood?
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Chickenpox
Measles Parvo B19 Roseola Rubella |
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What type of virus causes chickenpox and shingles?
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Herpesviridae
-enveloped with surface glycoproteins |
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When is someone with chickenpox infectious?
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Secondary viremia stage
~48hrs before rash, 4-5 days after crusting |
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What is the main method of transmission of chickenpox?
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Respiratory
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What type of immunity protects against chickenpox?
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Humoral limits viremic spread
CMI limits cell-to-cell transmission |
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Where does the virus become latent after chickenpox, what happens if it reactivates later in life?
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In the DRG
Results in shingles if reactivated |
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How long does the rash last for chickenpox?
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14-15 days
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How is chickenpox different in the immunocompromised?
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Lesions often have hemorrhagic bases, may get pneumo or encephalitis
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Describe perinatal chickenpox.
Describe congenital chickenpox. |
If a woman gets chickenpox right around the time she gives birth then mortality is very high.
If a woman gets chickenpox in the first half of pregnancy then the child will likely survive but may have skin scarring, low birth weight, microcephaly, etc |
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What is the distribution of the skin vesicles in shingles?
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Unilateral, follows a dermatome (often thoracic or lumbar)
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What is herpetic neuralgia?
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Pain associated with shingles that involves the nerves being irritable
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Which antivirals can be given to the immunocompromised, adults, or pregnant women with chickenpox?
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Acyclovir, Valacyclovir, Famcyclovir
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What type of vaccine is given for varicella?
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Live attenuated
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What is given to the elderly to prevent shingles?
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Zostavax
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What type of virus is rubella?
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Togavirus
-enveloped, +RNA |
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What type of immune response is most important in eliminating rubella?
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CMI
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How long does the maculopapular rash of rubella last in children normally?
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3 days
Relatively benign |
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Who develops the worst symptoms upon exposure to rubella?
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Adults get it worse than children
Worst if fetus gets it in the first trimester -cataracts, heart defects, deafness, FTT, MR |
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What type of vaccine is available for rubella?
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MMR
Live cold attenuated |
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What type of parasite causes trichinosis?
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Tissue-dwelling roundworm
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How do humans usually get trichinosis?
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From eating undercooked pork
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What is the only treatment for trichinosis once it has encysted?
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Bedrest and aspirin
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