ID Week 2 High Yield

Which antibiotic susceptibility tests provide an MIC?

Microbroth dilution, broth macrodilution, and gradient diffusion (E-test).

What does MIC stand for?

Minimum inhibitory concentration.

What is an MIC?

The lowest concentration of an antibiotic that inhibits visible bacterial growth.

Does microbroth dilution provide an MIC?

Yes.

Does broth macrodilution provide an MIC?

Yes.

Does gradient diffusion (E-test) provide an MIC?

Yes. The MIC is read where the inhibition ellipse intersects the strip.

Does standard disk diffusion provide an MIC?

No. It is a qualitative test that determines susceptibility or resistance.

Does agar dilution provide an MIC according to the Blueprint?

The document lists agar dilution as not providing an MIC.

What is the difference between an E-test and disk diffusion?

E-test uses a concentration gradient to determine MIC; standard disk diffusion is qualitative.

How can you identify whether a susceptibility test provides an MIC?

Look for a specific numerical antibiotic concentration rather than only growth or no growth.

What does a qualitative antibiotic susceptibility test determine?

Whether bacteria are susceptible or resistant, not the MIC.

Does a low MIC necessarily mean an antibiotic will be clinically effective?

No. A low MIC alone does not predict clinical treatment effectiveness.

What is an important principle of antibiotic stewardship?

Choose narrow-spectrum antibiotics when appropriate.

What other factor should be considered when selecting an antibiotic?

Potential side effects.

What is antigenic shift?

A sudden, major change in influenza A resulting in a new hemagglutinin and/or neuraminidase subtype.

Which influenza virus undergoes antigenic shift?

Influenza A.

What mechanism causes antigenic shift?

Reassortment of viral genome segments.

What can antigenic shift cause?

Pandemics.

What is antigenic drift?

Small, gradual changes caused by point mutations in viral genes.

What can antigenic drift cause?

Epidemics and the need for yearly influenza vaccine updates.

What is the difference between antigenic shift and drift?

Shift involves reassortment and major changes; drift involves point mutations and gradual changes.

Which antigenic change is associated with influenza pandemics?

Antigenic shift.

Which antigenic change explains yearly influenza vaccine updates?

Antigenic drift.

What virus is the most common cause of the common cold?

Rhinovirus.

Which virus is associated with cruise ship outbreaks of gastroenteritis?

Norovirus.

Which virus is associated with pinkeye (conjunctivitis)?

Adenovirus.

Which virus causes croup with a seal-like barking cough?

Parainfluenza virus.

What is the characteristic X-ray finding in croup?

Steeple sign.

What causes the steeple sign?

Subglottic narrowing of the upper airway.

What viral protein is responsible for syncytia formation?

F protein.

Which respiratory viruses are associated with syncytia formation through F protein?

RSV and parainfluenza viruses.

What is the characteristic shape of rabies virus?

Bullet-shaped.

What are Negri bodies?

Eosinophilic cytoplasmic inclusions associated with rabies infection.

Where are Negri bodies found?

In infected neurons.

Which virus is associated with Negri bodies?

Rabies virus.

What is post-polio syndrome?

Progressive muscle weakness or atrophy occurring 15–40 years after poliovirus infection.

Which polio vaccine is associated with vaccine-associated paralytic polio?

Sabin vaccine (live attenuated oral polio vaccine).

Why does the Sabin vaccine carry a risk of paralytic polio?

The live attenuated virus can rarely revert to neurovirulence.

What does a positive anti-HCV antibody indicate?

Past exposure or infection with hepatitis C; it does not establish active infection.

What test confirms active hepatitis C infection?

HCV RNA testing.

What does anti-HBV surface antibody indicate according to the Blueprint?

Immunity against hepatitis B.

What mnemonic does the Blueprint recommend for HBV serology?

SpECiES.

What does TORCHES VPZ represent?

Infections that can be transmitted from mother to baby during pregnancy or birth.

What does T in TORCHES VPZ stand for?

Toxoplasmosis.

What does O in TORCHES VPZ stand for?

The O is part of the TORCH acronym; the listed infections continue with Rubella.

What does R in TORCHES VPZ stand for?

Rubella.

What does C in TORCHES VPZ stand for?

Cytomegalovirus (CMV).

What does H in TORCHES VPZ stand for?

HIV.

What does HE in TORCHES VPZ stand for?

Herpes virus.

What does S in TORCHES VPZ stand for?

Syphilis.

What does V in TORCHES VPZ stand for?

Varicella-zoster virus (VZV).

What does P in TORCHES VPZ stand for?

Parvovirus.

What does Z in TORCHES VPZ stand for?

Zika virus.

What congenital abnormality is associated with Zika virus?

Microcephaly.

Why is pregnancy considered an immunocompromised state in the Blueprint?

Pregnancy involves immune adaptations that affect maternal immune responses.

Which type of vaccine should be avoided during pregnancy?

Live attenuated vaccines.

Why should live attenuated vaccines be avoided during pregnancy?

There is a risk of infection from the attenuated organism.

What is Reye syndrome associated with?

Aspirin use in children, particularly during viral illnesses.

Which medication should be avoided in children with viral illnesses because of Reye syndrome risk?

Aspirin.

What does a positive tourniquet test indicate in dengue fever?

Capillary fragility and hemorrhage associated with thrombocytopenia.

Why can dengue fever produce a positive tourniquet test?

Thrombocytopenia and fragile capillaries cause increased bleeding.

What are the major steps in HIV replication?

CD4 binding → fusion → reverse transcription → integration → replication → budding.

Which HIV protein attaches to CD4?

GP120.

Which HIV protein mediates fusion and entry?

GP41.

What receptor does HIV use as a coreceptor during early infection?

CCR5.

Which cells are associated with CCR5 usage in early HIV infection?

Macrophages.

What coreceptor is associated with later HIV infection?

CXCR4.

Which cells are associated with CXCR4 usage?

T cells.

What enzyme converts HIV RNA into DNA?

Reverse transcriptase.

What happens after HIV reverse transcription?

Viral DNA integrates into host DNA.

What enzyme allows HIV DNA to integrate into host DNA?

Integrase.

How does HIV exit an infected cell?

Budding.

What class of HIV medication is abacavir?

Nucleoside reverse transcriptase inhibitor (NRTI).

What screening is required before prescribing abacavir?

HLA-B*57:01 screening.

Why must HLA-B*57:01 be checked before abacavir?

Carriers are at increased risk of potentially fatal hypersensitivity reactions.

What is a major adverse effect of abacavir?

Hypersensitivity reaction.

What class of drug is tenofovir?

Nucleotide analog reverse transcriptase inhibitor.

Which two viral infections can tenofovir help treat?

HIV and hepatitis B.

What is an important adverse effect of tenofovir?

Nephrotoxicity.

What is the major adverse effect associated with efavirenz?

Neuropsychiatric effects.

What neuropsychiatric symptoms can efavirenz cause?

Dizziness, hallucinations, and vivid dreams.

Which viruses have double-stranded RNA genomes?

Reoviruses.

What is unusual about the RNA genome of reoviruses?

It contains both positive-sense and negative-sense RNA strands.

What happens to ALT and AST during acute viral hepatitis?

They can increase dramatically, approximately 400–10,000.

What are typical baseline ALT and AST levels according to the Blueprint?

Approximately 20.

What does an AST/ALT ratio below 1 indicate according to the Blueprint?

Chronic or late hepatitis.

What is the classic presentation of roseola?

High fever followed by a rash.

What temperature can occur with roseola?

Greater than 104°F.

What is the classic rash associated with parvovirus B19?

Slapped-cheek rash.