High Yield Topics-Microbiology Flashcards by Geun Young Park

What STI presents with a painless genital ulcer followed several weeks later by a diffuse maculopapular rash involving the palms and soles

syphilis (Treponema pallidum)

spirochete

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First-line treatment for syphilis

penicillin

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MOA of penicillin

binds to bacterial transpeptidase and interferes with bacterial cell wall synthesis through the inhibition of peptidoglycan cross-linking

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spread by respiratory droplets and present with an erythematous rash, “arthralgias”, “postauricular lymphadenopathy”, and fever

Rubella infection

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An infection during pregnancy –> infant manifests with cataracts, sensorineural deafness, and congenital heart disease (patent ductus arteriosus), and microcephaly

congenital rubella infection

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Rubella infection can be prevented by

measles-mumps-rubella (MMR) vaccination

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what kind is MMR vaccination?

live-attenuated vaccine

contraindicated during pregnancy!

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Presents with a fever, cough, “conjunctivitis”, and a maculopapular rash; no postauricular lymphadenopathy or arthralgias

Measles virus

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An infection during pregnancy –> infant presents with increases the risk for fetal demise and low birth weight

congenital measles

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An infection during pregnancy –> infant presents with localized lesions of the skin, eyes, and mouth + encephalitis and multiorgan dysfunction

Herpes simplex virus (HSV)

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An infection during pregnancy –> infant presents with intrauterine growth restriction, hepatosplenomegaly, petechiae, jaundice, thrombocytopenia, microcephaly, and chorioretinitis

Cytomegalovirus

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Neurocysticercosis (calcified nodules and some cysts of brain) is caused by

pork tapeworm (aka.Taenia solium)

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Source of pork tapeworm Taenia solium

raw or undercooked, infected pork

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Azoles (-conazole) inhibits the production of ergosterol (part of the fungal cell membrane) by

inhibiting the cytochrome P450-dependent demethylation reaction that synthesizes ergosterol from lanosterol.

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Prevention of cross-linking of β-glucans in the cell wall is the mechanism of action of

echinocandins

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Pore formation in the fungal cell membrane is the mechanism of action of

amphotericin B and nystatin

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Inhibition of DNA and RNA synthesis is the mechanism of action of what fungal tx?

flucytosine

tx for cryptococcal meningitis

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Prevention of tetrahydrofolic acid synthesis is the mechanism of action of

Sulfonamides and trimethoprim

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antibody that indicates immunity to hepatitis B due to vaccination or recovery from infection.

Anti-HBs

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Mnemonic for Viral hepatitis B markers

SpECiES

S: HBsAg
E: HBeAg
C: HBcAg

E: Anti-HBe
S: Anti-HBs

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antibody that indicates low transmissibility of hepatitis B

Anti-HBe

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the sole ⊕ marker of viral hepatitis B infection during window period

Anti-HBc (IgM)

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Three genes encoded by HIV RNA (diploid genome = two ssRNAs)

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What structural proteins are encoded by env gene?

glycoprotein 160 (later cleaves into gp120 and gp41)

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Function of gp 120

attachment to host CD4+ T cell

Function of gp 41

fusion and entry

What structural proteins are encoded by gag gene?

p24 and p17

Function of p24

capsid protein

Function of p17

matrix protein

What structural proteins are encoded by pol gene?

Reverse transcriptase Integrase Protease *STUDY AID: RIP Pol

Function of Reverse transcriptase

synthesizes dsDNA from viral RNA

Function of Integrase

integrates dsDNA into host genome

Function of Protease

Cleaves protein formed from dsDNA

HIV binds to what co-receptor on CD4 T cells?

CXCR4

HIV binds to what co-receptor on macrophages?

CCR5

What does HIV acquire through budding from host cell plasma membrane?

envelope glycoproteins and envelope

HIV is diagnosed using * know this cold!

HIV-1/2 Ag/Ab testing * It detects viral p24 "antigen" capsid protein + IgG "antibodies" to HIV 1 and HIV 2

HIV-1/2 Ag/Ab immunoassays has _____ sensitivity/specificity

high

What test is used to confirm HIV in case of indeterminate HIV-1/2 Ag/Ab immunoassays?

Nucleic acid test (NAT) * aka. viral load test (measure the amount of the genetic material (RNA) of HIV in the blood)

High viral load is used to monitor effect of

drug therapy

HIV genotyping is used to determine

appropriate therapy

AIDS can be diagnosed by what two criteria?

1. low CD4+ T cell count OR 2. HIV ⊕ with AIDS-defining condition (Pneumocystis pneumonia)

What CD4+ T cell count is used to diagnose AIDS?

≤ 200 CD4+ cells/mm3

Since HIV-1/2 Ag/Ab testing is not recommended in babies with suspected HIV due to maternally transferred antibody, what is used instead?

HIV viral load

What are the four stages of untreated infection? * HINT: 4 F's

1. Flu-like (acute) 2. Feeling fine (latent) 3. Falling count 4. Final Crisis

Amount of HIV RNA (viral load) is inversely proportional to

CD4+ T cell count

Describe amount of HIV RNA and CD4+ T cell count during four stages of untreated infection

1. Flu-like (acute) - high HIV RNA - CD4+ T cell count drops 2. Feeling fine (latent) - relatively low HIV RNA - CD4+ T cell count increases 3. Falling count - progressive increase of HIV RNA - progressive decrease of CD4+ T cell count 4. Final Crisis - high HIV RNA - very low CD4+ T cell count (<200) --> death

HIV RNA is relatively low during latency phase b/c

Virus replicates in lymph nodes during latency phase

What pathogen is responsible for oral hairy leukoplakia on tongue in HIV patients?

EBV

How to distinguish oral thrush (by candida) vs. oral hairy leukoplakia (by EBV)

oral thrush is scrapable vs. oral hairy leukoplakia is unscrapable

A condition that presents with loss of memory, difficulty thinking, concentrating, speaking clearly, etc. due to HIV virus spreading to the brain

HIV dementia

Imaging findings of HIV dementia

cerebral atrophy on neuroimaging

What pathogen is responsible for progressive multifocal leukoencephalopathy (brain white matter disease) and areas demyelination on MRI in HIV patients?

John Cunningham virus | aka. JC virus

What pathogen is responsible for pneumonia in HIV patients with CD4+ cell count <200?

Pneumocystis jirovecii

Chest imaging finding of Pneumocystis jirovecii pneumonia

“Ground-glass” opacities

What pathogen is responsible for pleuritic pain and hemoptysis?

Aspergillus

Chest imaging finding of Aspergillus fumigatus

Cavitation or infiltrates

What pathogen is responsible for bacillary (rod-shaped) angiomatosis in HIV patients?

Bartonella spp

Biopsy findings of bacillary (rod-shaped) angiomatosis

neutrophilic inflammation

What pathogen is responsible for esophagitis in HIV patients?

Candida albicans

What endoscopy finding is associated with esophagitis caused by Candida albicans?

White plaques on endoscopy

What biopsy finding is associated with esophagitis caused by Candida albicans?

yeast and PSEUDOHYPHAE on biopsy

What pathogen is responsible for Colitis, Retinitis, Esophagitis, Encephalitis, and Pneumonitis in HIV patients?

CMV * STUDY AID: CMV causes CREEP

What pathogen is responsible for linear ulcers on endoscopy?

CMV

What pathogen is responsible for cotton-wool spots on fundoscopy?

CMV

What biopsy finding is associated with CMV infections? * HINT: same as in all CMV infections

cells with intranuclear inclusion bodies (owl eyes)

What pathogen is responsible for meningitis in HIV patients?

Cryptococcus neoformans

What pathogen is responsible for encapsulated yeast on india ink stain or capsular antigen +?

Cryptococcus neoformans * STUDY AID: sketchyMicro

What pathogen is responsible for chronic, watery diarrhea in HIV patients?

Cryptosporidium spp

What pathogen is responsible for Acid-Fast oocysts in stool

Cryptosporidium spp

What pathogen is responsible for B-cell lymphoma (diffuse large b cell lymphoma, non-Hodgkin lymphoma, and CNS lymphoma) in HIV patients?

EBV

What pathogen is responsible for nonspecific symptoms such as fever, night sweats, weight loss or focal lymphadenitis in HIV patients?

Mycobacterium avium

What pathogen is responsible for brain abscesses in HIV patients?

Toxoplasma gondii

How to distinguish CNS lymphoma (EBV) vs. Toxoplasma gondii on brain MRI

Toxoplasma gondii: MULTIPLE ring-enhancing lesions CNS Lymphoma by EBV: SOLITARY ring-enhancing lesion

Faulty nucleo"sides" that halt reverse transcriptase's activity of converting ssRNA to dsDNA --> early chain termination

NRTIs - Lamivudine - Zidovudine - Stavudine - Didanosine - Emtricitabine - Abacavir * STUDY AID: "Dine" with my "nuclear (nucleosides)" family

NRTIs are missing what on its nucleoside?

3'OH

NRTIs must be _____ to be activated b/c they are nucleosides

phosphorylated

The only NRTI that is a nucleo"tide"

"T"enofovir

Tenofovir must be phosphorylated a total of ___ times to be active

3 | already phosphorylated but must be phosphorylated two times more to be active

Which NRTI has an adverse effect of myelosuppression (bone marrow suppression), leading to anemia and neutropenia (agranulocytosis)?

Zidovudine

Tx to reverse bone marrow suppression caused by Zidovudine?

- G-CSF (granulocyte colony-stimulating factor) | - Erythropoietin

Allele that increased the risk of Type 4 hypersensitivity with Abacavir

HLA-B 57:01 * STUDY AID: - Book: HLA-B - Page: 57 - Line: 1