Infectious Disease 1 Flashcards
- 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?
- virus
- bacterial
- mono
- What is strep throat caused by?
- What is this also known as?
- steptococcus pyogenes
- group A strep
If a person presents with a fever, sore throat, difficulty swallowing, swollen lymph nodes (anterior lymphadenopathy), and tonsillar pus, what might the person have?
strep (streptococcus pyogenes)
Anterior lymphadenopathy is associated with (…)
strep
- 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?
- rapid strep tests
- 5-10 minutes
- greater than or equal to 90%
- greater than 95%
If you have a person with a negative strep and you have a high suspicion to confirm, what can you do?
throat culture
How do you perform a rapid strep test?
- put on gloves
- have patient open mouth
- use a tongue depressor to push down on tongue, but don’t touch back of throat or gagging my result
- open swab
- swab both tonsils gently but firmly; you may get false negative if you swab too much towards midline/uvula
The normal human throat culture contains many normal flora and organisms, but sometimes can be infected with pathogenic organisms such as:
- streptococci species
- neisseria gonorrhoeae
- corynebacterium diptheriae
What are the indications for a throat culture?
- 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)
- What materials do you need for a throat culture?
- What is this procedure similar to?
- How is it different?
- single/double swab + gloves + tongue depressor
- rapid strep test
- specimen is labeled and sent to lab for gram-stain and culture
How long can throat culture results generally take to grow bacteria?
36-48 hours, longer for fungi
- What are the results of throat cultures?
- What do each mean?
- “no pathogenic organisms identified”
- may be viral or need to investigate if infectious at all - bacterial organism identified
- check if patient received antibiotics appropriate for that bacteria - fungal organism - takes longer to culture
- immunocompetent (uncommon)
- immunocompromised (candida albicans-thrush)
- You should investigate any ST of unclear origin if it persists for over (…)
- What could it be?
- 2 weeks
- acid reflux, HPV, tobacco use history
- The newer strep test allows for a more (…) identification of streptococcal antigens
- It reduces (…) results by (…)
- more precise
- false negative results by 90%
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?
anti-streptolysin O titer (ASO titer)
- 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 (…)
- two weeks
- streptolysin O
What are some other later-appearing conditions related to infection with strep pyogenes?
- glomerulonephritis
- rheumatic fever
- necrotizing fasciitis
- wound infections
- skin infections/rashes
- septicemia
- scarlet fever
- 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 (…)
- ASO titer
- group A strep
- weeks 1-3, week 3, 12 months
What are some common reasons to get an ASO titer in primary care/peds?
- 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)
- 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 (…)
- epstein-barr virus
- 80%
- dormant; reactivate
- children, adolescents, young adults
Mononucleosis commonly manifests similarly to (…)
strep throat
An acute sore throat can and should involve (…) testing in the appropriate patient who has a negative strep test
mononucleosis
What symptoms can infectious mononucleosis cause?
- fatigue, sore throat, fever
- lymphadenopathy (often bilateral, posterior > anterior cervical nodes)
- splenomegaly and hepatomegaly
Lymphadenopathy involving posterior cervical nodes is associated with what?
mononucleosis
- How can you test for mononucleosis?
- What does this test detect?
- What is the sensitivity?
- What is the specificity?
- rapid mononucleosis
- heterophile antibodies (cross-react with EBV)
- 85%
- 100%
What is the method of mononucleosis rapid testing?
- 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
- What are the 2 blood tests for EBV infection?
- Which one is the newer and more common method?
- serum heterophile antibodies
- epstein-barr IgG and IgM titers (newer more common)
When testing IgG and IgM titers for EBV, which one wanes three months after infection and which one persists for life?
- IgM wanes 3 months
- IgG persists for life
What are the indications for the epstein-barr IgG and IgM titers?
- rapid mono testing not available at location
- suspicion of EBV but rapid test negative
- to detect acuity or timing of infection, recent or remote
What is influenza caused by?
influenza strain A or B
- What severe symptoms can influenza cause?
- What are the minor symptoms?
- fever (usually greater than 100), myalgias (severe, worse in back and legs)
- cough, nasal congestion, sore throat
What are the advantages of the rapid flu test?
- patient can begin treatment w an antiviral immediately and self-quarantine
- family members and contacts are made aware of their risk on contacting virus
- 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
- subtype
- 48-72 hours
- the treatment regimen for the patient
- 48-72 hour window
What are the disadvantages to the rapid flu test?
- 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)
What do the rapid flu tests commonly contain?
- nasopharyngeal swab
- pipette
- test strips of some form
- an elution solution
- control solutions to ensure test quality
What is the sensitivity and specificity of the COVID test?
- sensitivity: 65% (false negatives common)
- specificity: 99.9% (false positives rare)
- 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
- sputum culture
- necessary
- 6-8 weeks
What are the limitations around sputum cultures?
- patient ability to truly expectorate appropriate deep sputum can result in decreased sensitivity, and tendency to pick up oral/oropharyngeal organisms
- 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
- lungs
- saliva
- 5-10 mL
- 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 (…)
- pertussis
- bordetella pertussis
- inspiratory whoop
- severe paroxysms of coughing fits
- post-cough emesis
- What does pertussis testing involve?
- What do you use for testing?
- What do you not use?
- 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
- What are the different tests for pertussis? Describe each
- What does the CDC recommend you do?
- 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
- 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?
- tuberculosis
- cough, fever, weigh loss, nigh sweats, fatigue; skeletal, GI, GU manifestations
If a patient is having night sweats and a cough, what is a possible explanation?
tuberculosis
What are tuberculosis screening tests?
TST - tuberculosis skin test
Who should you test for TB?
- persons who have symptoms or are suspected to have TB
- patients with known exposure to TB
- persons who are at higher risk of TB
Which people are at higher risk of TB?
- health care workers
- HIV patients
- IV drug users
- 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
- cannot
- 6-8 weeks
- for life
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
- two-step
- second TB
- 1-4 weeks
When reading a TB test, what is the only portion you should read?
- only read raised portion, not red area
What are the different TB reaction sizes?
- 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)
What is the interpretation of a TB reaction size less than 5 mm?
negative in everyone
What is the interpretation of a TB reaction size greater than/equal to 5 mm?
positive in:
- HIV infection
- close contact with + case
- immunocompromised
- CXR findings of old TB
What is the interpretation of a TB reaction size greater than/equal to 10 mm?
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)
What is the interpretation of a TB reaction size greater than/equal to 15 mm?
positive in:
- healthy, low-risk individuals over 4
In what scenarios may you receive a false negative TB skin test?
- recent infection < 8 weeks prior
- immunosuppression or waning natural immunity
- MMR vaccine (wait 4-6 weeks to perform TST)
- poor placement of TB test
In what scenarios may you receive a false positive TB skin test?
- infection with nontuberculosis mycobacterium
- BCG vaccination (in countries where TB is endemic)
- poor interpretation of TB test
- 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
- interferon-gamma release assays
- active or latent TB
- specific
- BCG vaccine
- What are the two interferon-gamma release assays for TB testing?
- Which one is more commonly ordered?
- What does this involve?
- QuantiFERON-TB Gold In-Tube (QFT-GIT); most common
- T-SPOT
- simple venipuncture
Interferon-gamma release assays for TB testing are preferred in what types of patients?
patients who come from countries that administer BCG vaccine or patients who have poor compliance with return to have TST read
What are the advantages of the QuantiFERON test over the TST?
- basic phlebotomy
- results in 24 hours
- single visit
- objective interpretation
- in vitro test
- no boost response
- not affected by BCG vaccine
Stool can be the key to diagnosing what?
- intestinal bleeding
- intestinal infections
- intestinal inflammation
- malabsorption syndromes
- cause of diarrhea
- What can be observed when there is a pathogenic organism causing infection?
- This is common in (…) and (…) infections
- fecal leukocytes
- shigella and salmonella
What are the 4 common bacteria that come back on a general stool culture?
- SSYC + E. coli
- Salmonella
- Shigella
- Yersinia
- Campylobacter
- E. coli
What are some indications for a stool culture?
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
- What test must be ordered separately from a stool culture?
- This test can only be performed on what type of stool?
- clostridium difficile
- loose or watery stool
Clostridium difficile testing is indicated in patients with what?
- pts w diarrhea who have been on antibiotics for more than 5 days, or have taken antibiotics recently
What can the consequences of C. diff be?
- mild to profound, foul- smelling diarrhea that hospitalizes patients
What are the indications for stool ova and parasites?
evaluation of diarrhea in a patient suspected of having a parasitic cause for their symptoms
Doing a stool ova and parasites is important in what individuals?
- people traveling to countries w endemic disease
- daycare workers
- AIDS patients
- community outbreak of specific organisms
- The most common etiology for diarrhea in the US is either (…) or (…)
- When diarrhea persists (…) days, investigate
- viral or bacterial
- > 7 days
If a patient has what symptoms, you will more than likely need a stool culture?
- fever
- bloody diarrhea
- weight loss
- exposures or outbreaks
What is also called fecal occult blood testing (FOBT) or stool guaiac?
hemoccult testing
What is usually done as part of routine rectal exam to check for occult bleeding from the GI tract?
hemoccult
What other conditions can you use hemoccult testing for?
- GI tract tumors, especially colorectal cancer
- IBS (UC or crohn’s disease)
- hemorrhoids
- bleeding from anywhere along nasopharyngeal to GI tract
What is the number 1 reason for hemoccult testing?
blood in diarrhea
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
- three-day period
- 3 day
How is the hemoccult test performed?
- 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
- Describe a negative hemoccult test
- Describe a positive hemoccult test
- no blue color, no hidden blood present in stool
- blue color, blood present in stool
What are the limitations of hemoccult testing?
- 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
What test is this describing:
- hemoglobin of blood can be detected by a chemical assay of the test causing a blue stain to appear
hemoccult
