infectious disease

Question 1

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

Answer 1

DNA polymerase I

Question 2

Zidovudine MOA

Answer 2

nucleoside reverse transcriptase inhibitor

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

Question 3

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

Answer 3

pneumocystis pneumonia (P jirovecci)

Question 4

What are the two antibiotic options to treat bacteria vaginosis

Answer 4

clindamycin

metronidazole

Question 5

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

Answer 5

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)

Question 6

What makes a virus capable of genetic shifts?

Answer 6

segmented genome (orthomyxovirus, rotavirus, etc)

Question 7

define genetic shift

Answer 7

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

Question 8

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

Answer 8

Dengue fever

Question 9

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

Answer 9

aedes mosquito

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

Question 10

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

Answer 10

ascaris lumbricoides (roundworm)

Question 11

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

Answer 11

inactivated

Question 12

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

Answer 12

CD4 molecule

chemokine receptor CCR5 or CXCR4

Question 13

Oseltamivir MOA

Answer 13

neuraminidase inhibitor (treats both influenza A and B infections)

Question 14

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

Answer 14

chancroid

haemophilus ducreyi

Question 15

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

Answer 15

bacterial toxins: levels of procalcitonin rise

viral infections: fall

Question 16

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

Answer 16

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

Question 17

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

Answer 17

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

Question 18

Treatment for schistosomiasis

Answer 18

praziquantel

Question 19

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

Answer 19

spilling of cysts contents can cause anaphylactic shock

Question 20

what antifungal is a P450 inhibitor

Answer 20

the azole drugs

Question 21

What does brain imaging show in neurocysticercosis

Answer 21

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

Question 22

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

Answer 22

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

Question 23

Ehrlichia chaffeensis:
mode of transmission
appearance on microscopy
clinical manifestation

Answer 23

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

Question 24

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

Answer 24

neurocysticercosis

Question 25

rifampin MOA

Answer 25

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

Question 26

How is MRSA resistant to nafcillin

Answer 26

alteration in the structure of penicillin binding proteins

Question 27

IgA proteases allow bacteria what advantage?

Answer 27

bacterial adherence to mucosa

Question 28

What is first line treatment for tocoplasmosis

Answer 28

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

Question 29

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

Answer 29

primary central nervous system lymphoma | the 2nd most common cause of ring enhancing lesions with mass effect in HIV

Question 30

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

Answer 30

B cells

Question 31

describe the histology of syphilitic lesions at all stages

Answer 31

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

Question 32

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

Answer 32

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)

Question 33

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

Answer 33

tinea pedis (athletes foot)

Question 34

Treatment for tinea pedis

Answer 34

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

Question 35

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

Answer 35

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

Question 36

What are the clinical manifestations of Chikungunya fever

Answer 36

high fevers and severe polyarthralgias almost always present | headache, myalgiea, conjunctivitis, maculopapular rash, lymphopenia, thrombocytopenia, transaminitis

Question 37

What are the clinical manifestations of vibrio vulnificus

Answer 37

rapidly progressive (often less than 12 hr) septicemia: septic shock and bullous lesions cellulitis: hemorrhagic bullae, necrotizing fasciitis

Question 38

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

Answer 38

``` liver disease iron overload (hemochromatosis) ```

Question 39

How does vibrio vulnificus transmission usually occur

Answer 39

consumption of raw seafood or wound contamination

Question 40

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

Answer 40

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

Question 41

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

Answer 41

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

Question 42

What will be seen on blood smear of babesiosis

Answer 42

intraerythrocytic pleomorphic ring forms and occasional Maltese crosses

Question 43

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

Answer 43

candidemia

Question 44

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

Answer 44

rapid antigen detection testing, immunoassay for GAS antigens

Question 45

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

Answer 45

elevated amylase | staph aureus

Question 46

Describe the stepwise progression of typhoid fever

Answer 46

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

Question 47

Streptococcus gallolyticus (formerly strep Bovis) has what presentation

Answer 47

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

Question 48

What is an intracellular cause of lobar pneumonia

Answer 48

``` legionaella monocytogenes (mycobacterium also intracellular) ```

Question 49

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

Answer 49

(this is a Thayer-martin medium) | used to identify pathogenic neisseria organisms

Question 50

How do test results for HIV2 differ from HIV1

Answer 50

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

Question 51

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

Answer 51

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

Question 52

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

Answer 52

V factor (NAD+)

Question 53

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

Answer 53

lipopolysaccharides | lipid A

Question 54

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

Answer 54

mother-to-child vertical transmission of HIV1

Question 55

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

Answer 55

toxoid | generates protective circulating IgG against the exotoxin B subunit

Question 56

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

Answer 56

pyrophosphate DNA polymerase reverse transcriptase

Question 57

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

Answer 57

chlamydia tachomatis | lymphogranuloma venereum

Question 58

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

Answer 58

klebsiella granulomatis (granuloma inguinale) (donovan bodies)

Question 59

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

Answer 59

herpes | cowdry type A bodies

Question 60

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

Answer 60

candida albicans

Question 61

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

Answer 61

HPV

Question 62

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

Answer 62

inhibits phagocytosis prevents complement binding aids in epithelial attachment

Question 63

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

Answer 63

nares | skin

Question 64

Empyema most commonly results from bacterial spread, how?

Answer 64

bacterial translocation from the alveoli into the pleural space

Question 65

What are the lesions present in tertiary syphilis

Answer 65

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

Question 66

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

Answer 66

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