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MSK, rheum, derm > microbiology > Flashcards

microbiology Flashcards

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Dermatology Board Prep flashcards
1
Q

polyarticular septic arthritis suggests which pathogen?

A

GBS

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2
Q

what location of septic arthritis suggests IVDU?

A

sternoclavicular joint

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3
Q

what bug is most responsible by far for septic arthritis? in which conditions is it seen even more?

A

staph aureus

RA and IVDU

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4
Q

what is the second most common cause of septic arthritis? what conditions are risk factors?

A

GBS

neonates, DM, malignancies

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5
Q

pseudomonas suggests what etiology of septic arthritis?

A

iatrogenic or IVDU

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6
Q

what bug is a cause of septic arthritis in young adults and those with complement deficiency, also SLE?

A

Neisseria

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7
Q

what bugs can cause septic arthritis in SLE? sickle cell?

A

salmonella: SLE and sickle cell
neisseria: SLE

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8
Q

what bug causes septic arthritis following dog or cat bite?

A

Pasteurella multocida

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9
Q

what is the etiology of septic arthritis due to brucella?

A

unpasteurized milk

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10
Q

what manifests with the clinical triad of 1. dermatitis 2. tenosynovitis 3. migratory polyarthritis

A

disseminated gonococcal infection: causes gonococcal arthritis

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11
Q

what groups does gonococcal arthritis occur in?

A

4x more in women

young and sexually active or IVDU

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12
Q

what does blood culture show in gonococcal arthritis?

A

occult bacteremia: won’t be able to culture

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13
Q

what is the most common cause of osteomyelitis? 2nd most common

A
  1. staph. aureus

2. staph. epidermidis

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14
Q

what bug causes osteomyelitis in someone who stepped on a nail?

A

pseudomonas

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15
Q

what are 2 most common and 2 other causes of vertebral osteomyelitis and spondyodiskitis?

A

staph aureus and staph epidermidis

MTB and brucella

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16
Q

what are 2 most common bugs responsible for osteomyelitis in children? what can also cause it in neonates?

A
  1. staph aureus
  2. strep pneumo
    neonates: GBS, E. coli
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17
Q

what bug, besides staph aureus, causes osteomyelitis in sickle cell? how?

A

salmonella

-gut infarcts release salmonella and auto-splenectomy so can’t clear it

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18
Q

what unusual locations of osteomyelitis suggest IVDU? what two bugs are responsible beside staph aureus?

A

sternoclavicular, sternochondral joint, pubic symphysis

pseudomonas and candida

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19
Q

what bug causes needle-licker OM?

A

eikenella corrodens

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20
Q

what are the two most common causes of pyomyositis?

A
  1. staph aureus by far (60-70%)

2. GAS (1-5%)

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21
Q

what bug causes gas gangrene? how is it cultured? appearance?

A

Clostridia perfringens
anaerobic culture with sugar fermentation and acid production
large box-car gram-positive rods

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22
Q

what is the pathogenesis of gas gangrene?

A

alpha toxin is liecithinase that damages cell membranes, causes hemolysis, produces gas in tissues

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23
Q 
describe the genome of: 
alphaherpesviruses
HPV
poxviridae
parvovirus B19
measles
mumps
rubella
coxsackievirus/enterovirus
HHV-6
A 
alphaherpesviruses: linear, dsDNA
HPV: circular dsDNA, very small
poxviridae: linear, dsDNA
parvo: -ssDNA, tiniest genome
measles/mumps: (paramxyo) -ssRNA
rubella: (toga) +ssRNA
coxsackie/entero: +ssRNA
HHV-6: dsDNA
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24
Q

what are the three stages of lytic cycle in herpes viruses?

A

immediate early: proteins contained in virus on infection lead to expression of other herpes genes by redirecting use of host RNA polymerase

early: replication of virus genome in nucleus of host cell
late: structural proteins synthesized in cytoplasm of host cell

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25
Q

what is the neurotropism of HSV-1, HSV-2 and VZV?

A

HSV1: trigeminal nerve
HSV2: lumbar and sacral nerves
VZV: dorsal root ganglia

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26
Q

what does LAT gene do in HSV-1?

A

produces microRNAs in latency to prevent apoptosis, repress viral gene expression, may inhibit CD8s

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27
Q

what test can be used to diagnose alphaherpesviruses? what does it show?

A

Tzanck smear: shows multinucleated cells

28
Q

how do HPV warts turn into malignant tumors?

A

occasionally, viral genome is integrated into host genome
-if E2 is split, high level expression of E6/7
E6: causes degradation of p53
E7: inhibits Rb

29
Q

what does the Gardasil vaccine contain?

A

L1 capsid protein from each carcinogenic strain of HPV

30
Q

what is unique about the replication of pox viruses?

A

encode all of own proteins so replicate in cytoplasm

-unique for DNA viruses

31
Q

how is molluscum contagiosum diagnosed in lab?

A

presence of cytoplasmic inclusions in keratinocytes

32
Q

how did the smallpox vaccine work?

A

live vaccinia viruses (lab strain of pox virus)

33
Q

what disease does parvovirus B19 cause in children? describe it

A

fifth disease of erythema infectiosum

slapped cheek and erythematous reticular rash

34
Q

what does parvovirus B19 cause in adults?

A

less rash and more polyarthritis, flu-like syndrome

35
Q

what cells do parvovirus B19 replicated in? what are two possible consequences?

A

precursor RBCs
aplastic crisis in sickle cell
chronic anemia in immunocompromised

36
Q

what two viral exanthems can cause neonatal infection? what do they do to the fetus?

A

parvovirus: fatal anemia or hydrops fatalis
rubella: congenital defects, blueberry rash

37
Q

what causes the symptoms of parvovirus infection?

A

immune response: cell-mediated causes rash, cytokines cause fever prodrome

38
Q

what is the clinical diagnosis definition of measles?

A
  1. generalized rash lasting >3 days
  2. high fever >38..3C (101F)
  3. three C’s: cough, coryza, conjunctivitis
39
Q

what is pathognomonic for measles? what causes the rash in measles?

A

Koplik spots

cell-mediated immune response

40
Q

what type of vaccine is the measles one?

A

live attenuated

41
Q

what are two potentially serious complications of measles?

A

immune suppression for about a month

encephalitis/encephalomyelitis

42
Q

what is the first sign of mumps?

A

parotid gland swelling and inflammation

43
Q

what are two potentially serious complications of mumps?

A

aseptic meningitis

gonadal involvement in post-pubertal men can cause sterility if bilateral

44
Q

which morbilliform viral rash begins on face and spreads and is accompanied by low fever, LAD, conjunctivitis, sore throat?

A

rubella

45
Q

what exanthem disease do coxsackievirus and enterovirus cause?

A

hand, foot and mouth disease

  • oral ulcerative lesions on tonsils, uvula
  • vascular lesions on hands and feet
46
Q

what does HHV-6 cause and who does it infect?

A

infants, children

47
Q

what causes Rocky Mountain Spotted Fever? how does the rash present? How can you diagnose it?

A

Rickettsia rickettsii
petechial rash starts on ankles/wrists and spreads
Weil-Felix test: antibody cross-reacts with Proteus antigens

48
Q

what causes Epidemic Typhus? how does the rash present? how is it transmitted?

A

Rickettsia prowazekii
petechial rash spreads from trunk to extremities (inverse of RMSF)
fleas/lice: virus in feces infects the bites

49
Q

what causes Endemic Typhus? How does it present? reservoir and transmission?

A

Rickettsia typhus
milder version of epidemic typhus
small mammals, fleas

50
Q

what can be diagnosed by morulae in monocytes/granuloctyes? what type of disease does it cause?

A

Ehrlichia chaffeensis and Anaplasma phagocytophilia

southern tick-borne diseases

51
Q

what is Anaplasmosis sometimes called? what are possible presentations?

A

Rocky Mountain Spotless Fever

  • CNS involvement
  • difficulty breathing, renal failure, hemorrhage
52
Q

Coxiella: most common location in US, reservoir, modes of transmission, possible complications

A
  • western agricultural states
  • sheep, cattle, goats
  • contaminated dairy of animal viscera, ticks, aerosolized spore-like form
  • pneumonic disease, liver or heart involvement causes chronic infection
53
Q

which spirochete may be visualized on blood smear?

A

Borrelia of relapsing fever: hermsii and recurrentis

54
Q

what causes Lyme disease? how can it be visualized? how is it diagnosed?

A

Borrelia burgdorferi
darkfield microscopy, Giemsa or silver stain
ELISA confirmed with Western Blot

55
Q

describe the 3 stages of Lyme disease

A
  1. erythema migrans, maybe flu/arthralgias
  2. heart block/myocarditis, meningitis, facial/Bell’s palsies
  3. progressive CNS disease, arthritis
56
Q

what species cause relapsing fever? where is it endemic to? reservoir and transmission? describe the rash

A

Borrelia hermsii and recurrentis
western US
rodents/small animals; ticks and body lice
rash is usually not present

57
Q

how can relapsing fever be diagnosed?

A

visualization on blood smear of spirochetes

convalescent serum during active symptoms

58
Q

what sort of bacteria is Leptospira interrogans? primary reservoir and transmission?

A

spirochete
dogs (also rodents, livestock)
water or soil contaminated from animal urine

59
Q

what is the clinical presentation of Leptospira infection? what is a characteristic finding?

A

two stages separated by quiescence:

  1. flu-like, conjunctivitis
  2. organ damage: liver, kidney, lung hemorrhage, meningitis
    - very high bilirubin is characteristic
60
Q

what causes Cat Scratch Fever? how does it present? in immunocompromised? how can it be diagnosed?

A

Batonella heneslae
fever with LAD, papule at site of infection, long course
immunocompromised: bacillary angiomas
Warthin-Starry silver stain

61
Q

what is the reservoir for anthrax? how does cutaneous infection present?

A

cattle, sheep
painless lesion that becomes blistered with necrotic center
-can have dizziness, palpitations, sepsis

62
Q

what is the reservoir for Burkholderia? what strange way may it be diagnosed?

A

soil, water and livestock

resistant to gentamicin and colistin

63
Q

where is francisella found? how is it transmitted? what does the cutaneous infection look like? what is the virulence factor? how can it be diagnosed?

A

Arkansas, Missouri, Martha’s Vineyard
fleas, lice, ticks; contaminated animals, blood or water
ulceroglandular with bubo-like LAD and flu symptoms
agglutination testing

64
Q

where does plague occur in US and why? what causes “black death”? how can the safety pin be visualized?

A

west: reservoir is prairie dogs
endotoxin-related effects cause DIC and cutaneous hemorrhages
Giemsa or Wayson stains

65
Q

what are three virulence factors of plague?

A
  1. anti-phagocytic capsule
  2. LPS endotoxin
  3. Yops: injected into host cells, inhibit phagocytosis and cytokine production

MSK, rheum, derm (6 decks)

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