Chapter 54 Viral Infections

Front 1

What are the seasonal peaks for enteroviruses and rotavirus?

Back 1

Enteroviruses peak in late summer and early fall . Rotavirus is a wintertime disease.

Hint 1

Front 2

Which two cell lines would you select to culture influenza virus?

Back 2

Rhesus monkey kidney and the R-Mix hybrid of mink lung/A549 are the most sensitive for influenza.

Front 3

Which two cell lines would you select to culture herpes simplex virus (HSV)?

Back 3

For HSY, choose human diploid fibroblast (HDF), Hep-2, or rabbit kidney.

Front 4

What are the two advantages of enzyme immunoassay(EIA) over direct fluorescent antibody (DFA)?

Back 4

EIA is more easily automated and is less subjective in the interpretation of positive vs negative than DFA.

Front 5

What is the transport temperature for viral transport media, for all samples except blood?

Back 5

4°C is the transport temperature for viral culture specimens.

Front 6

Cell culture isolation is still the gold standard for diagnosis of HSV. Cytopathic effect (CPE) by standard culture methods is usually evident in ??days. Describe the characteristic CPE.

Back 6

The standard cell culture for HSV shows syncytial formation in 2-3 days. For most cell cultures, the centrifugation method speeds up growth, and for HSV, cultures may show CPE after only 1 day.

Front 7

What is the role of DFA in both standard and centrifugation-enhanced cultures for HSV?

Back 7

DFA is used to confirm positive CPE in cultures.

Front 8

Which of the influenza viruses is more common and produces more serious illness?

Back 8

This is influenza A.

Front 9

What two laboratory methods are useful for rapid diagnosis of influenza and utilize a nasopharyngeal swab?

Back 9

One is the DFA stain. If you aspirate several columnar epithelial cells where the virus is lurking, you can pick them up right away with DFA. EIA is rapid and easy to perform; sensitivity is better with nasopharyngeal aspirates than with throat swabs with this method.

Front 10

What are the two rapid diagnostic methods for respiratory syncytial virus?

Back 10

DFA and EIA. These are much faster methods than the 3-10 days needed to culture this virus . Respiratory syncytial virus (RSV) is a serious illness in infants, and prompt diagnosis is critical to the initiation of therapy.

Front 11

What two cell types does Epstein-Barr virus (EBV) infect in humans?

Back 11

Recall that EBY infects pharyngeal epithelial cells (infectious mononucleosis starts with a sore throat) as well as the B lymphocytes.

Front 12

To what EBV antigen are the heterophile antibodies directed?

Back 12

None . That is why we use the complicated tests with cells from other species
to sort out nonspecific antibodies from those that are associated with EBV. The antibodies that bind to EBV antigens are those binding to the early antigen (EA) and to the viral capsid antigen (VCA) .

Front 13

What four other primary infections might be demonstrated in a mononucleosis ­ like illness that is EBV-negative?

Back 13

Toxoplasma gondii, CMV, human herpes virus 6 (HHV 6), and HIV all may cause a mononucleosis-like illness.

Front 14

What is the most common intrauterine infection and infects 1% of liveborn infants in the USA?

Back 14

CMV. Thankfully, 90% are asymptomatic

Front 15

What test performed on amniotic fluid is reliable in the diagnosis of CMV?

Back 15

PCR, along with culture.

Front 16

What is the first test to perform if one suspects acute rubella in a woman who is 10 weeks pregnant?

Back 16

Serology is the mainstay to begin the diagnostic process. Start with an antirubella IgM for an acute infection.

Front 17

What test can be performed to diagnose human immunodeficiency virus (HIV) in an infant, and what is the earliest age this test can be performed?

Back 17

Maternal antibodies to HIV transmitted transplacentally can persist for up to 15 months, so this is not a useful method for detecting vertical HIV infection . The PCR assay for transcribed DNA in lymphoid cells can be performed at 1 month of age, and RT-PCR can be performed at birth if the neonate was infected transplacentally.

Front 18

What subfamily of viruses accounts for nearly 75% of cases of viral meningitis in the USA?

Back 18

Enteroviruses are the main player here. The gold standard is RT-PCR of the cerebrospinal fluid.

Front 19

To diagnose varicella zoster virus in a patient, what specimen should be taken for culture?What tissue culture cells work well, and what method of culture is preferred?
A DFA conjugate stain is applied to confirm positives in??days.

Back 19

Vesicle fluid (a new lesion) is cultured on human diploid fibroblasts (HDF) in a shell vial. At 3-5 days, one may perform a DFA conjugate stain to look for positivity.

Front 20

Two viral exanthems with similar sounding names are erythema infectiosum, which is due to ??
and exanthem subitum, due to??

Back 20

Erythema infectiosum is due to parvovirus B19 . This illness is commonly called 'slapped cheek' in children because of their facial erythema . Exanthem subitum is due to HHV 6.

Front 21

Rotavirus is a major cause of diarrhea in the pediatric population. What are three other viruses that cause diarrhea in this age group?

Back 21

Other pediatric gastroenteritis viruses include adenovirus serotypes 40 and 41,
astroviruses, and caliciviruses .

Front 22

In a community hospital setting, what are the two main methods of diagnosing rotavirus?

Back 22

These are latex agglutination or EIA. Electron microscopy is quite specific, but it cannot easily be performed in hospital settings.

Front 23

Can any of the hepatitis viruses be grown in standard tissue culture cell lines?

Back 23

No. Diagnosis of the hepatitides rests on serology and PCR.

Front 24

Which is the most common genotype of hepatitis C virus (HCV) in the US?
How effective is treatment with a-interferon in patients with this genotype?

Back 24

Genotype 1 is found in 75% of US HCV patients, but it is not very responsive to therapy with a-IFN.

Front 25

A 28-year-old male with HIV has a viral load of 10 000 copies/mL prior to starting antiretroviral therapy. 2 months after initiating therapy and maintaining good compliance, his viral load has fallen by 1.0 log copies/mL. How many copies are present by the polymerase chain reaction (PCR) assay?

Back 25

1000 copies/mL will be present after a 1.0 log reduction. Do not forget your basic math skills when taking an examination. Some questions are as simple as this one. This reduction in viral load (at least 0.5-1.0 log copies/mL) correlates with slowed disease progression in HIV, so this patient is doing OK.

Front 26

What technique is used to determine the viral load in hepatitis C?

Back 26

Viral load is determined by RT-PCR. HCV is an RNA virus and the nucleic acid must be converted to DNA. The same is true for HIV.

Front 27

What type of culture has shortened the incubation time for cytomegalovirus (CMV) to 1-2 days? What is the main cell line for culturing CMV?

Back 27

The centrifugation -enhanced shell vial shortens the incubation time. CMV strongly prefers HDF as its cell line for culture.