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Microbiology > Skin/Muscle/Bone > Flashcards

Skin/Muscle/Bone Flashcards

1
Q

S. pyogenes structural virulence factors

A

M protein: destroys C3 convertase
F protein: mediates adherence via fibronectin-binding proteins
Pili and TA: attachment

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2
Q

Bartonella hensleae

A

Causes: Cat Scratch Dz
Pathogenesis: obligate intracellular, can trigger proliferation of endothelial cells
ROS: regional lymphadenopathy
Diagnosis: Warthin-Starry stain, IFA, serology

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3
Q

Chromoblastomycosis

A

Transmission: traumatic implantation
Incubation: months-years
Pathogenesis: granulomatous inflammation
ROS: wart-like lesions w/ crusting abscesses extending along lymphatics
Dx: dark brown, round fungal cells seen in leukocytes or giant cells

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4
Q

Condylomata acuminatum

A

Caused by HPV 6 and 11

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5
Q

Epidermophyton

A

No microconidia

Microconidia: “beaver-tail” appearance

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6
Q

S. pyogenes toxins

A

Pyrogens exotoxins (SPE): stimulates cytokines release (causes erythematous rash)

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7
Q

Melassazia Furfur

A

Pathogenesis: infects stratum corneumphenols degrade lipids producing acid that damages melanocytes and inhibit tyrosinase
Clinical manifestation: Pityriasis versicolor
Dx: short septate hyphae w/ spores = “spaghetti and meatball”

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8
Q

Tinea Nigra

A

Etiology: Cladosporium werneckii
Epidemiology: Southern US
ROS: brown spot caused by melanin-like pigment in hyphae
Tx: topical keratolytic agent

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9
Q

Rubella

A

*Aka German Measles
Family: Togaviridae (TORCH infection)
ROS: centripetal rash, postauricular lymphadenopathy, Forchheimer’s sign (petechial lesion on palate)

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10
Q

S. pyogenes enzymes virulence

A

C5a peptidase: inhibits production of C5a
Streptokinase: breaks down fibrin clot
Hyaluronidase: degrades HA in ECM (like in nec fasc)

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11
Q

Necrotizing Fasciitis

A

Etiology: type I is polymicrobial, or type II is S. pyogenes
ROS: sudden onset pain, crepitus, fever, tenderness, hypoperfusion and bullae later in the course

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12
Q

Trichnosis

A

Etiology: Trichnella spiralis
Transmission: ingestion of cysts in undercooked meat
ROS: periorbital edema, fever, myalgia, rashes, eosinophilia, splinter hemorrhages
Complication: myocarditis, CNS/lung involvement
Dx: muscle biopsy showing cysts, ELISA, eosinophilia

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13
Q

Cellulitis/Erysipelas with h/o pw?

A

Pseudomonas aeruginosa

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14
Q

White Piedra

A

Etiology: Trichosporon
Transmission: person-to-person
Epidemiology: semitropical and temperate climates
Pathogenesis: ascostroma are fruiting bodies, then ascospores released
ROS: superficial infection of hair shaft
Tx: shave infected hair

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15
Q

Cellulitis/Erysipelas in pt w/ dog or cat injury?

A

Pasteurella multocida

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16
Q

Loaisis

A

Etiology: Loa loa
Vector: deer fly (Chrysops)
ROS: dermis and subcutaneous skin infection (Calabar swelling - red/itchy on extremities and body 1-3d), itching d/t migration of the worm
Dx: microfilirae on PB (daytime sample), eosinophilia, adult worm in eye

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17
Q

Impetigo

A

Cause: S. aureus (80%), and S. pyogenes (occasionally)
ROS: honey crusted lesions that don’t scar bc doesn’t affect dermis

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18
Q

Onchocerciasis (River Blindness)

A

Etiology: Onchocera volvulus
Vector: black fly
ROS: intense itching when worm dies and Wolbachia pipientis is released into tissues, nodules where adult worms gather, heals w/ discoloration of skin, fever w/ myalgia/arthralgia, wt loss, keratitis, uveitis, retinitis, optic neuritis
Complication: blindness, wrinkled skin from long-term infection

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19
Q

Cutaneous Larva Migrans

A

Etiology: Ancylostoma braziliense
Transmission: skin penetration
Pathogenesis: eggs hats, then filariform larva penetrate skin
ROS: creeping eruption, serpiginous erythematous tracking in skin assoc w/ intense itchiness (you can see the gross worm under the skin)

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20
Q

Non-bullous Impetigo

A

Most common
Etiology: S. aureus
Pathology: TA adhesions (fibronectin-binding proteins) require epithelial receptor fibronectin for attachment/colonization

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21
Q

Cellulitis/Erysipelas in child < 6yo?

A

H. Influenza

22
Q

Post-streptococcal sequelae

A
  • Post-strep Glomerulonephritis (s/p impetigo or pharyngitis)
  • Rheumatic Fever (s/p pharyngitis mainly, rarely impetigo)
23
Q

Trichophyton

A

Affects 3 things: skin, hair, nails
Microconidia: birds on a lane
Microconidia: looks like a caterpillar

24
Q

What is Roseola Infantum?

A

6th disease, Exanthem Subitum, HHV-6

25
Bullous Impetigo
Etiology: S. aureus Group II Type 71 Pathology: Exfoliatins degrade desmoglein-1 resulting in loss of superficial dermis (lesions occur on intact skin)
26
Secondary skin infection
Occur in skin that's already diseased (can have multiple organisms) *overgrowth of resident flora
27
Smallpox
Family: Poxviridae Pathogenesis: variola major is highly virulent, causes toxemia, shock and DIC ROS: flu-like sx's w/ synchronous eruptive pustules (centripetal spread) start on mouth and spread everywhere Prevention: Jennerian vaccine
28
Tinea (Pityriasis) Versicolor
Etiology: Melassazia furfur Risk: sun exposure, hot/humid climates (+ immunosuppression) ROS: hypo- and hyper- pigmentation on chest/back Tx: selenium sulfide shampoo
29
HFMD
Etiology: Coxsackie A16 (and A6) Transmission: fecal-oral and droplets Epidemiology: children in the summer ROS: maculopaular/vesicular rash on hands/feet and oral enanthems + prodrome of fatigue/ST/fever
30
Ecthyma
Etiology: B-hemolytic Streptococcus Pathology: when impetigo goes to dermis
31
Erythema Infectiosum
*Aka Fifth Dz Family: Parvoviridae Pathogenesis: binds P ag on erythrocyte precursors ROS: slapped cheek rash, lacy red rash, arthritis in adults Complication: hydrops fetalis,
32
Measles
*Aka Rubeola Family: Paramyxoviridae Pathogenesis: syncytia formation, F protein and Hemagglutinin, infects CD150+ lymphocytes and CD46+ cells ROS: cough, coryza, conjunctivitis, centripetal rash, Koplik spots on buccal mucosa Complication: SSPE (years later, pt not infectious)
33
Chickenpox
Family: Herpesviridae (HHV-3 aka VZV) ROS: asynchronous pustules w/ centrifugal spread *TORCH infection Complication: Shingles bc reactivation in DRG
34
Condylomata lata
Caused by Treponema pallidum (highly infectious)
35
Cutaneous Leishmaniasis
Etiology: Leishmania (tropicana, mexicana, braziliensis) Vector: sandfly Dx: amastagoets w/in macrophages
36
Mansonellosis
Etiology: Mansonella streptocerca (M for Moses) ROS: chronic papular lesions w/ post-inflammatory hyperpigmentatin Complication: Lichenification (thickened/leathery skin) Dx: microfilirae in blood w/ classic hook @ end of worm ("walking stick" shape to tail)
37
Flaggrin genotype
Predisposes individual to skin infections
38
Roseola Infantum
*Aka 6th Dz (Exanthem Subitum) Family: Herpes (HHV-6) Pathogenesis: tropism for CD4+ T-cells, CD46+ cells ROS: centrifugal rash (spares face), febrile sz s/p rash
39
Sporotrichosis (Rose Gardner's Dz)
Etiology: Sporothrix stencil Transmission: penetration by rose thorn ROS: small red pustule then ascending lymphangitis, distal lesions ulcerated and drain Dx: "cigar-shaped" yeast (aka thin branched hyphae), "flowerette" mold phase
40
Clostridium perfringens
Morphology: "boxcar" rods, double zone of hemolysis, egg yolk agar (EYA), Nagler +ve, spore forming Pathogenesis: lecithinase - degrades membranes, causes RBC lysis and decreases blood supply to tissues *spores germinate in anaerobic conditions releasing toxins causing gas gangrene
41
CA-MRSA
PVL toxin (USA300 and USA400 type)
42
Primary skin infection
Caused by single pathogen and affects NORMAL skin
43
Molluscum Contagiosum
Family: Poxvirus ROS: non-painful dome-shaped lesion w/ dimpled center (flesh colored w/ pearly appearance *if diffuse suggests HIV Diagnosis: molluscum bodies in epidermis (Lg cells w/ eosinophilic inclusions and small peripheral nucleus)
44
Erysipelas
Infection of upper dermis and superficial lymph Prevalence: young children and elderly ROS: raised plaques w/ well-defined borders
45
Black Piedra
Etiology: Piedraia hostage or Trichosporon Epidemiology: humid tropical areas Transmission: person-to-person Pathogenesis: ascostroma are fruiting bodies, then ascospores released ROS: superficial fungal infection of hair shaft Tx: shave infected hair
46
Cellulitis
Infection of hypodermis and subcutaneous fat Etiology: β-hemolytic Strep, S. aureus ROS: ill-defined borders that expand rapidly, accompanied by lymphangitis (streaking), usually on extremities Prevention: NOT contagious
47
Cellulitis/Erysipelas in pt w/ exposure to freshwater/seawater
Vibrio vulnificus and Aeromonas hydrophil
48
Herpangina
Etiology: Coxsackie A (picorna) Transmission: fecal-oral or droplets Epidemiology: children in summertime ROS: painful ulcerative oral enanthem, vesicles on soft palate, erythematous pharyngitis, fever, malaise, ST (cervical lymphadenopathy sometimes)
49
HA-MRSA
USA100, USA500, USA800 | Resistant to almost all abx, no PVL toxin
50
B. anthracis virulence factors
.
51
B. anthracis Clinical Manifestations
.

Microbiology (14 decks)

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