infectious disease Flashcards
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
DNA polymerase I
Zidovudine MOA
nucleoside reverse transcriptase inhibitor
thymidine analogue that does not have the normal 3’-hydroxyl group found on thymidine leading to chain termination
If a homeless person presents with hypoxia, bilateral interstitial infiltrates and a positive silver staining bronchoalveolar lavage what is the diagnosis
pneumocystis pneumonia (P jirovecci)
What are the two antibiotic options to treat bacteria vaginosis
clindamycin
metronidazole
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
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)
What makes a virus capable of genetic shifts?
segmented genome (orthomyxovirus, rotavirus, etc)
define genetic shift
reassortment of entire genomic segments of the human strain with genomic segments of the animal strain
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
Dengue fever
How is the chickungunya virus spread and what are typically clinical presentations
aedes mosquito
febrile illness with flulike symptoms, prominent polyarthralgia/arthritis, and diffuse macular rash
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
ascaris lumbricoides (roundworm)
What type of vaccine is approved for people with high exposures (ie veterinarians)
inactivated
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
CD4 molecule
chemokine receptor CCR5 or CXCR4
Oseltamivir MOA
neuraminidase inhibitor (treats both influenza A and B infections)
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
chancroid
haemophilus ducreyi
How do procalcitonin levels change in response to bacterial toxins and viral infections
bacterial toxins: levels of procalcitonin rise
viral infections: fall
The Jarisch-Herxheimer reactio is an acute inflammatory reaction that occurs within hours of treatment for spirochetal infections. Why?
rapid lysis of spirochetes releases inflammatory bacterial lipoproteins into the circulation and causes acute fever, rigors, and myalgias
When should prophylaxis begin for Pneumocystis jirovecii, Mycobaterium avium complex, and toxoplasma gondii
pneumocystis jirovecii: CD4 < 200
toxo gondii: CD4 < 100
myco avium: CD4 < 50
Treatment for schistosomiasis
praziquantel
Echinococcus granulosus tapeworm is most common cause of hydatid cysts. Surgical removal of the cysts in the liver should be performed with caution, why
spilling of cysts contents can cause anaphylactic shock
what antifungal is a P450 inhibitor
the azole drugs
What does brain imaging show in neurocysticercosis
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
The zika virus can cross the placenta causing what effects to the fetus
infect and destroy fetal neural progenitor cells –> microcephaly, artrhogryposis (contractures), seizures, hypertonia, ocular abnormalities, loss of brain mass (cortical thinning), subcortical calcifications
Ehrlichia chaffeensis:
mode of transmission
appearance on microscopy
clinical manifestation
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
what diagnosis should be suspected in a patient with new onset seizures in a developing country who has cystic or calcified brain lesions
neurocysticercosis
rifampin MOA
blocks the action of the bacterial DNA-dependent RNA polymerase, thereby inhibiting transcription
How is MRSA resistant to nafcillin
alteration in the structure of penicillin binding proteins
IgA proteases allow bacteria what advantage?
bacterial adherence to mucosa
What is first line treatment for tocoplasmosis
combination of pyrimethamine and sulfadiazine
(or pyrimethamine and clindamycin if sulfa allergy)
along with leucovorin (folinic acid)
If a patient with HIV and multiple-ring enhancing lesions being treated for toxoplasmosis with no improvement, what other condition should suspicion rise for
primary central nervous system lymphoma
the 2nd most common cause of ring enhancing lesions with mass effect in HIV
Primary central nervous system lymphoma is typically composed of what cell type
B cells
describe the histology of syphilitic lesions at all stages
proliferative endarteritis of small vessels with a surrounding plasma cell rich infiltrate
What is the most common mechanism of aminoglycoside resistance as seen in pseudomonas aeruginosa
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)
A patient that has prurituc, erythematous rash affecting the feet with microscopy of the skin scrapings showing branching hyphae have what diagnosis
tinea pedis (athletes foot)
Treatment for tinea pedis
topical fungals: azoles (miconazole, clotrimazole), allylamines (terbinafine) and tolnaftate
Where are Chikungunya infections likely to occur and what is the vector
tropical/subtropical parts of central/south america, africa, and asia
Aedes mosquito
What are the clinical manifestations of Chikungunya fever
high fevers and severe polyarthralgias almost always present
headache, myalgiea, conjunctivitis, maculopapular rash, lymphopenia, thrombocytopenia, transaminitis
What are the clinical manifestations of vibrio vulnificus
rapidly progressive (often less than 12 hr)
septicemia: septic shock and bullous lesions
cellulitis: hemorrhagic bullae, necrotizing fasciitis
What are risk factors that make someone more likely to be infected with vibrio vulnificus
liver disease iron overload (hemochromatosis)
How does vibrio vulnificus transmission usually occur
consumption of raw seafood
or
wound contamination
What does the mecA gene code for which is present in certain strains of staph aureus
penicillin binding protein 2a (has low affinity for beta lactams)
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
RNA transcribed into double stranded DNA by reverse transcriptase –> viral DNA enters nucleus —> integrase inserts the DNA into host cell’s chromosomes
What will be seen on blood smear of babesiosis
intraerythrocytic pleomorphic ring forms and occasional Maltese crosses
Patients receiving parenteral nutrition (through a central venous catheter) are at high risk for what yeast infection
candidemia
In office throat swab with what type of testing can provide on-site microbiologic confirmation of a Group A strep infection
rapid antigen detection testing, immunoassay for GAS antigens
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
elevated amylase
staph aureus
Describe the stepwise progression of typhoid fever
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
Streptococcus gallolyticus (formerly strep Bovis) has what presentation
subacute bacterial endocarditis (symptoms similar to strep viridans)
associated with colonic cancer in 25% of patients
What is an intracellular cause of lobar pneumonia
legionaella monocytogenes (mycobacterium also intracellular)
What does a growth medium containing vancomycin, colistin, nystatin, and trmethoprim test for
(this is a Thayer-martin medium)
used to identify pathogenic neisseria organisms
How do test results for HIV2 differ from HIV1
HIV antigen/antibody test (4th generation HIV test): positive
HIV-1 western blot: intermediate in HIV2
plasma HIV1 RNA: negative in HIV2
How does treatment for malaria acquired in Africa differ from treatment for malaria acquired in mexico
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
H flu colonies will grow around streaks of beta hemolytic s aureus colonies because S aureus actively secretes what?
V factor (NAD+)
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
lipopolysaccharides
lipid A
Oral thrush, interstitial pneumonia, and severe lymphopenia during the first year of life are consistent with what diagnosis
mother-to-child vertical transmission of HIV1
What type of immunization is used for corynebacterium diptheriae and mounts what type of immune response
toxoid
generates protective circulating IgG against the exotoxin B subunit
Foscarnet is a ____ analog that does not require intracellular activation. It directly inhibits ___ in herpesvirus and ____ in HIV
pyrophosphate
DNA polymerase
reverse transcriptase
What cause of a painless penile ulcer has intracytoplasmic inclusion bodies in epithelial cells and leukocytes
chlamydia tachomatis
lymphogranuloma venereum
what cause of a painless penile ulcer has deeply staining gram negative intracytoplasmic cysts
klebsiella granulomatis
(granuloma inguinale)
(donovan bodies)
what cause of painful penile ulcer has multinucleated giant cells and intranuclear inclusions
herpes
cowdry type A bodies
What organism will appear on sputum culture as round-to-oval, budding yeast, which form germ tubes when incubated at 37 C in serum
candida albicans
Most oropharyngeal carcinomas (ie tonsils, base of tongue) are cause by what infection
HPV
How is M protein a helpful virulence factor for group A strep
inhibits phagocytosis
prevents complement binding
aids in epithelial attachment
staph aureus colonizes the ___ and ____ which is not eliminated by oral antibiotics so recurrent infections are common
nares
skin
Empyema most commonly results from bacterial spread, how?
bacterial translocation from the alveoli into the pleural space
What are the lesions present in tertiary syphilis
gummas: painless, indurated granulomatous lesions that progress to white-gray rubbery lesions that may ulcerate
What is the treatment of phthirus pubis (pubic louse) and MOA
topical permethrin: blocks parasite sodium ion conduction in nerve cell membrane channels and results in louse paralysis and death
