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UWorld > infectious disease > Flashcards

infectious disease Flashcards

1
Q

what bacterial enzyme is involved in DNA replication and is responsible for removing short fragments of RNA that are base paired to the DNA template

A

DNA polymerase I

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2
Q

Zidovudine MOA

A

nucleoside reverse transcriptase inhibitor

thymidine analogue that does not have the normal 3’-hydroxyl group found on thymidine leading to chain termination

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3
Q

If a homeless person presents with hypoxia, bilateral interstitial infiltrates and a positive silver staining bronchoalveolar lavage what is the diagnosis

A

pneumocystis pneumonia (P jirovecci)

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4
Q

What are the two antibiotic options to treat bacteria vaginosis

A

clindamycin

metronidazole

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5
Q

If a mother passes a torch infection to her child, what will the symptomatic neonate and now asymptomatic mother’s titers be of IgG and IgM antibodies

A

asymptomatic mother: elevated IgG but not IgM

symptomatic neonate: elevated IgG (from mother) and IgM (made on their own because they are primarily infected also)

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6
Q

What makes a virus capable of genetic shifts?

A

segmented genome (orthomyxovirus, rotavirus, etc)

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7
Q

define genetic shift

A

reassortment of entire genomic segments of the human strain with genomic segments of the animal strain

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8
Q

What infection presents with acute febrile illness with headache, retro-orbital pain, and joint and muscle pain. Other findings can include hemorrhage, thrombocytopenia, leukopenia, and hemoconcentration and may be associated with recent travel

A

Dengue fever

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9
Q

How is the chickungunya virus spread and what are typically clinical presentations

A

aedes mosquito

febrile illness with flulike symptoms, prominent polyarthralgia/arthritis, and diffuse macular rash

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10
Q

what parasitic infection involving the lungs and intestines is visualized on stool microscopy as an oval egg with a thick outer shell and a single interior ovum

A

ascaris lumbricoides (roundworm)

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11
Q

What type of vaccine is approved for people with high exposures (ie veterinarians)

A

inactivated

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12
Q

HIV attaches to host cells using viral surface glycoprotein gp120 which binds to ___ as the primary receptor and the _____ as a coreceptor. binding of both induces a conformational change that exposes gp41 for viral fusion

A

CD4 molecule

chemokine receptor CCR5 or CXCR4

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13
Q

Oseltamivir MOA

A

neuraminidase inhibitor (treats both influenza A and B infections)

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14
Q

What can cause a painful penile lesion that may present has multiple and deep ulcers, may have gray to yellow exudate with ragged borders and inguinal lymphadenopathy

A

chancroid

haemophilus ducreyi

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15
Q

How do procalcitonin levels change in response to bacterial toxins and viral infections

A

bacterial toxins: levels of procalcitonin rise

viral infections: fall

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16
Q

The Jarisch-Herxheimer reactio is an acute inflammatory reaction that occurs within hours of treatment for spirochetal infections. Why?

A

rapid lysis of spirochetes releases inflammatory bacterial lipoproteins into the circulation and causes acute fever, rigors, and myalgias

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17
Q

When should prophylaxis begin for Pneumocystis jirovecii, Mycobaterium avium complex, and toxoplasma gondii

A

pneumocystis jirovecii: CD4 < 200
toxo gondii: CD4 < 100
myco avium: CD4 < 50

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18
Q

Treatment for schistosomiasis

A

praziquantel

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19
Q

Echinococcus granulosus tapeworm is most common cause of hydatid cysts. Surgical removal of the cysts in the liver should be performed with caution, why

A

spilling of cysts contents can cause anaphylactic shock

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20
Q

what antifungal is a P450 inhibitor

A

the azole drugs

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21
Q

What does brain imaging show in neurocysticercosis

A

typically shows >1 cysts in various stages of viability
viable cysts: round, nonenhancing, hypodense, + or - scolex
degenerating cysts: enhancing with edema
nonviable cysts: calcified nodules

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22
Q

The zika virus can cross the placenta causing what effects to the fetus

A

infect and destroy fetal neural progenitor cells –> microcephaly, artrhogryposis (contractures), seizures, hypertonia, ocular abnormalities, loss of brain mass (cortical thinning), subcortical calcifications

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23
Q

Ehrlichia chaffeensis:
mode of transmission
appearance on microscopy
clinical manifestation

A

harbored in white tailed deer and transmitted by ticks
micro: replicates in vacuoles within monocytes and forms mulberry-shaped, intraleukocytic inclusions (morulae)
fever, chills, myalgia, maculopapular rash, lymphopenia thrombocytopenia, elevated aminotransferases

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24
Q

what diagnosis should be suspected in a patient with new onset seizures in a developing country who has cystic or calcified brain lesions

A

neurocysticercosis

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25
Q

rifampin MOA

A

blocks the action of the bacterial DNA-dependent RNA polymerase, thereby inhibiting transcription

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26
Q

How is MRSA resistant to nafcillin

A

alteration in the structure of penicillin binding proteins

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27
Q

IgA proteases allow bacteria what advantage?

A

bacterial adherence to mucosa

28
Q

What is first line treatment for tocoplasmosis

A

combination of pyrimethamine and sulfadiazine
(or pyrimethamine and clindamycin if sulfa allergy)
along with leucovorin (folinic acid)

29
Q

If a patient with HIV and multiple-ring enhancing lesions being treated for toxoplasmosis with no improvement, what other condition should suspicion rise for

A

primary central nervous system lymphoma

the 2nd most common cause of ring enhancing lesions with mass effect in HIV

30
Q

Primary central nervous system lymphoma is typically composed of what cell type

A

B cells

31
Q

describe the histology of syphilitic lesions at all stages

A

proliferative endarteritis of small vessels with a surrounding plasma cell rich infiltrate

32
Q

What is the most common mechanism of aminoglycoside resistance as seen in pseudomonas aeruginosa

A

antibiotic modifying enzymes: add chemical groups (actyle, adenyl, phosphate) to target drug
(altered aminoglycosides have a reduced ability to bind to the 16S ribosomal RNA within the 30S ribosomal subunit)

33
Q

A patient that has prurituc, erythematous rash affecting the feet with microscopy of the skin scrapings showing branching hyphae have what diagnosis

A

tinea pedis (athletes foot)

34
Q

Treatment for tinea pedis

A

topical fungals: azoles (miconazole, clotrimazole), allylamines (terbinafine) and tolnaftate

35
Q

Where are Chikungunya infections likely to occur and what is the vector

A

tropical/subtropical parts of central/south america, africa, and asia
Aedes mosquito

36
Q

What are the clinical manifestations of Chikungunya fever

A

high fevers and severe polyarthralgias almost always present

headache, myalgiea, conjunctivitis, maculopapular rash, lymphopenia, thrombocytopenia, transaminitis

37
Q

What are the clinical manifestations of vibrio vulnificus

A

rapidly progressive (often less than 12 hr)

septicemia: septic shock and bullous lesions
cellulitis: hemorrhagic bullae, necrotizing fasciitis

38
Q

What are risk factors that make someone more likely to be infected with vibrio vulnificus

A 
liver disease
iron overload (hemochromatosis)
39
Q

How does vibrio vulnificus transmission usually occur

A

consumption of raw seafood
or
wound contamination

40
Q

What does the mecA gene code for which is present in certain strains of staph aureus

A

penicillin binding protein 2a (has low affinity for beta lactams)

41
Q

After an HIV viron enters a host cell, viral ___ is released from the nucleocapsid and then what happens in order for viral DNA to insert into host DNA

A

RNA transcribed into double stranded DNA by reverse transcriptase –> viral DNA enters nucleus —> integrase inserts the DNA into host cell’s chromosomes

42
Q

What will be seen on blood smear of babesiosis

A

intraerythrocytic pleomorphic ring forms and occasional Maltese crosses

43
Q

Patients receiving parenteral nutrition (through a central venous catheter) are at high risk for what yeast infection

A

candidemia

44
Q

In office throat swab with what type of testing can provide on-site microbiologic confirmation of a Group A strep infection

A

rapid antigen detection testing, immunoassay for GAS antigens

45
Q

Parotitis risk factors include dehydration, intubation, medications that decrease salivary flow, salivary flow obstruction, and recent intense teeth cleaning. What lab value is helpful for diagnosis and what is the most common infectious organism

A

elevated amylase

staph aureus

46
Q

Describe the stepwise progression of typhoid fever

A

week 1: rising fever, bacteremia, relative bradycardia
week 2: abdominal pain, rose spots on trunk and abdomen
week 3: hepatosplenomegaly and intestinal bleeding and perforation

47
Q

Streptococcus gallolyticus (formerly strep Bovis) has what presentation

A

subacute bacterial endocarditis (symptoms similar to strep viridans)
associated with colonic cancer in 25% of patients

48
Q

What is an intracellular cause of lobar pneumonia

A 
legionaella monocytogenes
(mycobacterium also intracellular)
49
Q

What does a growth medium containing vancomycin, colistin, nystatin, and trmethoprim test for

A

(this is a Thayer-martin medium)

used to identify pathogenic neisseria organisms

50
Q

How do test results for HIV2 differ from HIV1

A

HIV antigen/antibody test (4th generation HIV test): positive
HIV-1 western blot: intermediate in HIV2
plasma HIV1 RNA: negative in HIV2

51
Q

How does treatment for malaria acquired in Africa differ from treatment for malaria acquired in mexico

A

chloroquine-sensitive organisms are known to be in mexico and other areas so should be treated with choroquine
many african species are chlorquine resistant and can be treated with atovaquone-proguanil or artermisinins

52
Q

H flu colonies will grow around streaks of beta hemolytic s aureus colonies because S aureus actively secretes what?

A

V factor (NAD+)

53
Q

gram negative sepsis is caused by the release of ______ from bacterial cells during cell division or bacteriolysis. ____ is the toxic component of it that induces widespread release of IL-1 and TNF alpha from activated macrophages

A

lipopolysaccharides

lipid A

54
Q

Oral thrush, interstitial pneumonia, and severe lymphopenia during the first year of life are consistent with what diagnosis

A

mother-to-child vertical transmission of HIV1

55
Q

What type of immunization is used for corynebacterium diptheriae and mounts what type of immune response

A

toxoid

generates protective circulating IgG against the exotoxin B subunit

56
Q

Foscarnet is a ____ analog that does not require intracellular activation. It directly inhibits ___ in herpesvirus and ____ in HIV

A

pyrophosphate
DNA polymerase
reverse transcriptase

57
Q

What cause of a painless penile ulcer has intracytoplasmic inclusion bodies in epithelial cells and leukocytes

A

chlamydia tachomatis

lymphogranuloma venereum

58
Q

what cause of a painless penile ulcer has deeply staining gram negative intracytoplasmic cysts

A

klebsiella granulomatis
(granuloma inguinale)
(donovan bodies)

59
Q

what cause of painful penile ulcer has multinucleated giant cells and intranuclear inclusions

A

herpes

cowdry type A bodies

60
Q

What organism will appear on sputum culture as round-to-oval, budding yeast, which form germ tubes when incubated at 37 C in serum

A

candida albicans

61
Q

Most oropharyngeal carcinomas (ie tonsils, base of tongue) are cause by what infection

A

HPV

62
Q

How is M protein a helpful virulence factor for group A strep

A

inhibits phagocytosis
prevents complement binding
aids in epithelial attachment

63
Q

staph aureus colonizes the ___ and ____ which is not eliminated by oral antibiotics so recurrent infections are common

A

nares

skin

64
Q

Empyema most commonly results from bacterial spread, how?

A

bacterial translocation from the alveoli into the pleural space

65
Q

What are the lesions present in tertiary syphilis

A

gummas: painless, indurated granulomatous lesions that progress to white-gray rubbery lesions that may ulcerate

66
Q

What is the treatment of phthirus pubis (pubic louse) and MOA

A

topical permethrin: blocks parasite sodium ion conduction in nerve cell membrane channels and results in louse paralysis and death

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