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Clinical Science > Infectious Disease 1 > Flashcards

Infectious Disease 1 Flashcards

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1
Q
  • If you look in a throat and there is mild pharyngeal injection but no exudate, what is the most likely cause?
  • If there is exudate, what could be the cause?
  • What is the exception to this?
A
  • virus
  • bacterial
  • mono
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2
Q
  • What is strep throat caused by?
  • What is this also known as?
A
  • steptococcus pyogenes
  • group A strep
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3
Q

If a person presents with a fever, sore throat, difficulty swallowing, swollen lymph nodes (anterior lymphadenopathy), and tonsillar pus, what might the person have?

A

strep (streptococcus pyogenes)

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4
Q

Anterior lymphadenopathy is associated with (…)

A

strep

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5
Q
  • How can you test for strep?
  • How long does it take to get the results of this test?
  • What is the sensitivity?
  • What is the specificity?
A
  • rapid strep tests
  • 5-10 minutes
  • greater than or equal to 90%
  • greater than 95%
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6
Q

If you have a person with a negative strep and you have a high suspicion to confirm, what can you do?

A

throat culture

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7
Q

How do you perform a rapid strep test?

A
  1. put on gloves
  2. have patient open mouth
  3. use a tongue depressor to push down on tongue, but don’t touch back of throat or gagging my result
  4. open swab
  5. swab both tonsils gently but firmly; you may get false negative if you swab too much towards midline/uvula
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8
Q

The normal human throat culture contains many normal flora and organisms, but sometimes can be infected with pathogenic organisms such as:

A
  • streptococci species
  • neisseria gonorrhoeae
  • corynebacterium diptheriae
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9
Q

What are the indications for a throat culture?

A
  • severe/recurrent sore throat w/ systemic symptoms (fever, palpable lymph nodes)
  • negative rapid strep but HCP confirmation desired
  • identification of chronic strep carrier
  • suspected complicated of group A strep infection (scarlet fever/generalized rash)
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10
Q
  • What materials do you need for a throat culture?
  • What is this procedure similar to?
  • How is it different?
A
  • single/double swab + gloves + tongue depressor
  • rapid strep test
  • specimen is labeled and sent to lab for gram-stain and culture
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11
Q

How long can throat culture results generally take to grow bacteria?

A

36-48 hours, longer for fungi

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12
Q
  • What are the results of throat cultures?
  • What do each mean?
A
  1. “no pathogenic organisms identified”
    - may be viral or need to investigate if infectious at all
  2. bacterial organism identified
    - check if patient received antibiotics appropriate for that bacteria
  3. fungal organism - takes longer to culture
    - immunocompetent (uncommon)
    - immunocompromised (candida albicans-thrush)
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13
Q
  • You should investigate any ST of unclear origin if it persists for over (…)
  • What could it be?
A
  • 2 weeks
  • acid reflux, HPV, tobacco use history
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14
Q
  • The newer strep test allows for a more (…) identification of streptococcal antigens
  • It reduces (…) results by (…)
A
  • more precise
  • false negative results by 90%
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15
Q

What lab test can we use if we suspect a patient had a recent streptococcal infection of the throat or elsewhere and has now developed new symptoms of their infections?

A

anti-streptolysin O titer (ASO titer)

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16
Q
  • A rapid strep may only be positive for (…), but some adverse effects can persist
  • During its growth, strep pyogenes produces extracellular products, proteins, and enzymes, including (…)
A
  • two weeks
  • streptolysin O
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17
Q

What are some other later-appearing conditions related to infection with strep pyogenes?

A
  • glomerulonephritis
  • rheumatic fever
  • necrotizing fasciitis
  • wound infections
  • skin infections/rashes
  • septicemia
  • scarlet fever
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18
Q
  • What measures presence of our antibody titers to streptolysin O?
  • This detects a recent infection of (…)
  • Its value rises over (…) weeks, peaks at week (…), and returns to normal within (…)
A
  • ASO titer
  • group A strep
  • weeks 1-3, week 3, 12 months
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19
Q

What are some common reasons to get an ASO titer in primary care/peds?

A
  • undefined rash suspected to be scarlet fever caused by strep A throat infection
  • sudden increased creatinine in child post-strep causing case of post-streptococcal glomerulonephritis (increased creatinine after a recent strep pharyngitis infection)
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20
Q
  • What virus causes mononucleosis?
  • Greater than (…) of the US population has been exposed to this virus
  • After an acute infection, this virus becomes (…) and most people will not have future symptoms, but it can (…) later
  • The majority of affected patients are (…)
A
  • epstein-barr virus
  • 80%
  • dormant; reactivate
  • children, adolescents, young adults
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21
Q

Mononucleosis commonly manifests similarly to (…)

A

strep throat

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22
Q

An acute sore throat can and should involve (…) testing in the appropriate patient who has a negative strep test

A

mononucleosis

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23
Q

What symptoms can infectious mononucleosis cause?

A
  • fatigue, sore throat, fever
  • lymphadenopathy (often bilateral, posterior > anterior cervical nodes)
  • splenomegaly and hepatomegaly
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24
Q

Lymphadenopathy involving posterior cervical nodes is associated with what?

A

mononucleosis

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25
Q
  • How can you test for mononucleosis?
  • What does this test detect?
  • What is the sensitivity?
  • What is the specificity?
A
  • rapid mononucleosis
  • heterophile antibodies (cross-react with EBV)
  • 85%
  • 100%
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26
Q

What is the method of mononucleosis rapid testing?

A
  • fingers cleaned with sterile alcohol pad and wiped dry
  • using lancet, whole blood obtained from finger
  • first drop is wiped off, fill well with second (allow two drops)
  • wait 5 minutes to read
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27
Q
  • What are the 2 blood tests for EBV infection?
  • Which one is the newer and more common method?
A
  • serum heterophile antibodies
  • epstein-barr IgG and IgM titers (newer more common)
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28
Q

When testing IgG and IgM titers for EBV, which one wanes three months after infection and which one persists for life?

A
  • IgM wanes 3 months
  • IgG persists for life
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29
Q

What are the indications for the epstein-barr IgG and IgM titers?

A
  • rapid mono testing not available at location
  • suspicion of EBV but rapid test negative
  • to detect acuity or timing of infection, recent or remote
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30
Q

What is influenza caused by?

A

influenza strain A or B

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31
Q
  • What severe symptoms can influenza cause?
  • What are the minor symptoms?
A
  • fever (usually greater than 100), myalgias (severe, worse in back and legs)
  • cough, nasal congestion, sore throat
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32
Q

What are the advantages of the rapid flu test?

A
  • patient can begin treatment w an antiviral immediately and self-quarantine
  • family members and contacts are made aware of their risk on contacting virus
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33
Q
  • The rapid flu test does not identify the (…)
  • It is best used when the onset of symptoms of (…) within presentation
  • Testing is not recommended if it does not change what?
  • Antivirals are not usually indicated after (…) window of symptoms
A
  • subtype
  • 48-72 hours
  • the treatment regimen for the patient
  • 48-72 hour window
34
Q

What are the disadvantages to the rapid flu test?

A
  • sensitivies = 50-70% (specificity 95%)
  • sensitivity higher in children than adults since children tend to shed the virus longer than adults
  • involves uncomfortable nasopharyngeal sampling using swab (most common) or wash/aspirate
  • poor technique can decrease sensitivity (increases number of false positives)
35
Q

What do the rapid flu tests commonly contain?

A
  • nasopharyngeal swab
  • pipette
  • test strips of some form
  • an elution solution
  • control solutions to ensure test quality
36
Q

What is the sensitivity and specificity of the COVID test?

A
  • sensitivity: 65% (false negatives common)
  • specificity: 99.9% (false positives rare)
37
Q
  • In cases of patients with cough, fever, or abnormal chest x-ray findings, a (…) may be indicated
  • This is only when it is (…) to determine the pathogenic pulmonary organism
  • Fungal sputum cultures can take up to (…) weeks to analyze
A
  • sputum culture
  • necessary
  • 6-8 weeks
38
Q

What are the limitations around sputum cultures?

A
  • patient ability to truly expectorate appropriate deep sputum can result in decreased sensitivity, and tendency to pick up oral/oropharyngeal organisms
39
Q
  • In a sputum culture, patients need to expectorate sputum from the (…) and (…) is just not enough for an accurate test
  • There needs to be at least (…) ml of sputum for culture
A
  • lungs
  • saliva
  • 5-10 mL
40
Q
  • What is also known as “whooping cough”?
  • What is this bacterial upper respiratory infection caused by?
  • Sufferers have what is known as a (…) with their cough and (…) and (…)
A
  • pertussis
  • bordetella pertussis
  • inspiratory whoop
  • severe paroxysms of coughing fits
  • post-cough emesis
41
Q
  • What does pertussis testing involve?
  • What do you use for testing?
  • What do you not use?
A
  • involves nasopharyngeal swab (PCR testing usually)
  • do use dacron swab w/ flexible shaft
  • do not use cotton or rayon swabs, they are toxic to pertussis
42
Q
  • What are the different tests for pertussis? Describe each
  • What does the CDC recommend you do?
A
  • PCR of bordetella pertussis (nasopharyngeal): higher cost, not affected by previous antibiotic use, results available in 1-2 days
  • culture of bordetella pertussis - requires second swab: can take 7-10 days
  • CDC recommends both be used to confirm diagnosis
43
Q
  • What is an infectious disease spread through the air and is transmitted by respiratory droplets from coughing, sneezing, speaking and spitting?
  • What are some of the respiratory and systemic manifestations?
A
  • tuberculosis
  • cough, fever, weigh loss, nigh sweats, fatigue; skeletal, GI, GU manifestations
44
Q

If a patient is having night sweats and a cough, what is a possible explanation?

A

tuberculosis

45
Q

What are tuberculosis screening tests?

A

TST - tuberculosis skin test

46
Q

Who should you test for TB?

A
  • persons who have symptoms or are suspected to have TB
  • patients with known exposure to TB
  • persons who are at higher risk of TB
47
Q

Which people are at higher risk of TB?

A
  • health care workers
  • HIV patients
  • IV drug users
48
Q
  • A TB skin test (…) determine if this infection if active or dormant
  • Results of a TB test will be positive (…) weeks after TB infection
  • This test remains positive for (…) after infection and further testing after a definite positive result is useless
A
  • cannot
  • 6-8 weeks
  • for life
49
Q

Sometimes a (…) TB test is required due to the fact that remote infection with TB can cause waning of immune response and false negative, so a (…) TB test (…) weeks later will cause a “booster effect” -> a true positive

A
  • two-step
  • second TB
  • 1-4 weeks
50
Q

When reading a TB test, what is the only portion you should read?

A
  • only read raised portion, not red area
51
Q

What are the different TB reaction sizes?

A
  • less than 5 mm
  • greater than/equal to 5 mm (highest risk)
  • greater than/equal to 10 mm (medium risk)
  • greater than/equal to 15 mm (low risk)
52
Q

What is the interpretation of a TB reaction size less than 5 mm?

A

negative in everyone

53
Q

What is the interpretation of a TB reaction size greater than/equal to 5 mm?

A

positive in:
- HIV infection
- close contact with + case
- immunocompromised
- CXR findings of old TB

54
Q

What is the interpretation of a TB reaction size greater than/equal to 10 mm?

A

positive in:
- children under 4
- persons from countries w/ high TB incidence
- IV drug users
- residents/employees in high-risk settings
- economically disadvantaged
- medical conditions associated w/ reactivation (cancer, diabetes, dialysis)

55
Q

What is the interpretation of a TB reaction size greater than/equal to 15 mm?

A

positive in:
- healthy, low-risk individuals over 4

56
Q

In what scenarios may you receive a false negative TB skin test?

A
  • recent infection < 8 weeks prior
  • immunosuppression or waning natural immunity
  • MMR vaccine (wait 4-6 weeks to perform TST)
  • poor placement of TB test
57
Q

In what scenarios may you receive a false positive TB skin test?

A
  • infection with nontuberculosis mycobacterium
  • BCG vaccination (in countries where TB is endemic)
  • poor interpretation of TB test
58
Q
  • What is a relatively recent test approved for the detection of latent TB infection?
  • This cannot differentiate between what?
  • Antigens targeted in test are more (…) for M. tuberculosis than PPD antigens
  • This can be used regardless of (…) vaccine status
A
  • interferon-gamma release assays
  • active or latent TB
  • specific
  • BCG vaccine
59
Q
  • What are the two interferon-gamma release assays for TB testing?
  • Which one is more commonly ordered?
  • What does this involve?
A
  • QuantiFERON-TB Gold In-Tube (QFT-GIT); most common
  • T-SPOT
  • simple venipuncture
60
Q

Interferon-gamma release assays for TB testing are preferred in what types of patients?

A

patients who come from countries that administer BCG vaccine or patients who have poor compliance with return to have TST read

61
Q

What are the advantages of the QuantiFERON test over the TST?

A
  • basic phlebotomy
  • results in 24 hours
  • single visit
  • objective interpretation
  • in vitro test
  • no boost response
  • not affected by BCG vaccine
62
Q

Stool can be the key to diagnosing what?

A
  • intestinal bleeding
  • intestinal infections
  • intestinal inflammation
  • malabsorption syndromes
  • cause of diarrhea
63
Q
  • What can be observed when there is a pathogenic organism causing infection?
  • This is common in (…) and (…) infections
A
  • fecal leukocytes
  • shigella and salmonella
64
Q

What are the 4 common bacteria that come back on a general stool culture?

A
  • SSYC + E. coli
  • Salmonella
  • Shigella
  • Yersinia
  • Campylobacter
  • E. coli
65
Q

What are some indications for a stool culture?

A

patients w/ acute case of severe or persistent diarrhea especially in certain circumstances:
- fever, nausea, vomiting, weight loss
- recent foreign travel
- ingestion of well or contaminated water
- bloody diarrhea
- recent antibiotic use
- ingestion of undercooked or poorly prepared food

66
Q
  • What test must be ordered separately from a stool culture?
  • This test can only be performed on what type of stool?
A
  • clostridium difficile
  • loose or watery stool
67
Q

Clostridium difficile testing is indicated in patients with what?

A
  • pts w diarrhea who have been on antibiotics for more than 5 days, or have taken antibiotics recently
68
Q

What can the consequences of C. diff be?

A
  • mild to profound, foul- smelling diarrhea that hospitalizes patients
69
Q

What are the indications for stool ova and parasites?

A

evaluation of diarrhea in a patient suspected of having a parasitic cause for their symptoms

70
Q

Doing a stool ova and parasites is important in what individuals?

A
  • people traveling to countries w endemic disease
  • daycare workers
  • AIDS patients
  • community outbreak of specific organisms
71
Q
  • The most common etiology for diarrhea in the US is either (…) or (…)
  • When diarrhea persists (…) days, investigate
A
  • viral or bacterial
  • > 7 days
72
Q

If a patient has what symptoms, you will more than likely need a stool culture?

A
  • fever
  • bloody diarrhea
  • weight loss
  • exposures or outbreaks
73
Q

What is also called fecal occult blood testing (FOBT) or stool guaiac?

A

hemoccult testing

74
Q

What is usually done as part of routine rectal exam to check for occult bleeding from the GI tract?

A

hemoccult

75
Q

What other conditions can you use hemoccult testing for?

A
  • GI tract tumors, especially colorectal cancer
  • IBS (UC or crohn’s disease)
  • hemorrhoids
  • bleeding from anywhere along nasopharyngeal to GI tract
76
Q

What is the number 1 reason for hemoccult testing?

A

blood in diarrhea

77
Q

A positive hemoccult result over a (…) indicates a higher suspicion for abnormal cause, so you can send a person home with a (…) fecal occult blood test

A
  • three-day period
  • 3 day
78
Q

How is the hemoccult test performed?

A
  • obtain stool through rectal exam/patient doing it at home
  • place stool sample on front two windows of hemoccult
  • close the front and turn card over
  • take liquid test solution bottle, drop a drop on back of each window and one in between the control section
  • if you see blue color in windows, consider positive
79
Q
  • Describe a negative hemoccult test
  • Describe a positive hemoccult test
A
  • no blue color, no hidden blood present in stool
  • blue color, blood present in stool
80
Q

What are the limitations of hemoccult testing?

A
  • lacks sensitivity and specificity
  • false positives can occur with foods such as red meat, turnips, radishes
  • false negatives can occur with ingestion of vitamin C
  • oral iron does not affect result
81
Q

What test is this describing:
- hemoglobin of blood can be detected by a chemical assay of the test causing a blue stain to appear

A

hemoccult

Clinical Science (18 decks)

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