ID Flashcards
Explain the role of beta-d-glucan in a patient with severe sepsis.
Beta-d-glucan is a fungal antigen detection test. In sepsis patients, they could have elevated levels of beta-d-glucan, meaning that could point to antifungal treatment regimen or the levels could be elevated for another unknown reason. If a beta-d-glucan is positive, we can consider antifungal treatment. If a beta-d-glucan is negative, we can role out a fungal cause.
Explain the difference between uremia and azotemia. Describe some of the signs and symptoms associated with uremia.
Azotemia is the elevation of BUN due to an excess of urea and other nitrogenous wastes. Uremia are the signs and symptoms of azotemia. For example, a patient may have itchy, flaky deposits on the skin, nausea, vomiting, confusion, and fatigue.
Gram positive cocci:
Streptococcus: pyogenes, viridans, agalactiae, gallolyticus, pneumonia, mutans. Chains indicate that it is probably strep.
Staphylococcus: aureus, epidermidis, saprophyticus, haemolyticus, luguensis. Pairs or clusters indicate that it is more likely staph.
Enterococcus: faecalis, faecium
Peptostreptococcus: magnus, saccharolyticus
Gram positive rods:
Bacillus: anthracis, cereus
Clostridium: tetani, botulinum, perfringens
Clostridiodes: difficile
Corynebacterium: diptheria
Listeria: monocytogenes
Actinomyces
Nocardia
Streptomyces
Actinetobacter
Gram negative cocci
Neisseria: gonorrhea, meningitis
Moraxella: catarrhalis
Haemophilus: influenzae, ducreyi
Gram negative rods
E. coli
Proteus mirabilis
Pseudomonas aeruginosa
Klebsiella: pneumoniae, oxytoca
Describe the appropriate next test for the following, and explain your reasoning. Positive 4th generation assay for HIV screening
Do an HIV-1/HIV-2 antibody differentiation immunoassay.
Describe the appropriate next test for the following, and explain your reasoning.HIV 1 / HIV 2 antibody differentiation assay
positive for HIV 1- western blot- protein electrophoresis for HIV-1
Describe the appropriate next test for the following, and explain your reasoning. Negative 4th generation assay and positive PCR in a patient with acute symptoms
Do an HIV-1/HIV-2 antibody differentiation immunoassay.
Describe the appropriate next test for the following, and explain your reasoning. Negative 4th generation assay and negative PCR in a patient with acute symptoms and multiple risk factors for HIV-
repeat testing again in 1-2 weeks
Which values are expected to be different on a newborn BMP and in what way (higher/lower)?
Newborns have higher potassium
Explain the diagnostic testing for Bordatella pertussis, including when in the disease course they are used.
Mostly a clinical diagnosis, but can also do culture and PCR, which is best in pts with cough up to 4 weeks or Serology also best after 4 weeks
A patient’s blood cultures result with Coagulase negative Staph. Explain what will help you decide if this is a contaminant or a pathogen that needs treating.
Epidermis will not need treatment if only one of the vials is contaminated, but if all of them are, then treat for staph aureus
Define what a hematocrit is measuring.
Hematocrit measures the amount of RBCs to whole blood (cells/ total vol.)
Explain the most likely cause of an unexpectedly high potassium.
Hemolysis during phlebotomy can cause false evalution
What is the most definitive test for active tuberculosis?
Obtain a chest x-ray, If it is concerning, obtain 3 sputum samples and test each sample with culture, NAAT, and acid fast bacilli. Culture is the gold standard.
Describe the diagnostics used for Mononucleosis, and what findings would be expected on a CBC.
We will do a CBC and peripheral blood smear test to see if there are more than 50% of total cells are lymphocytes and if greater than 10% of those are atypical lymphocytes, which will look like monocytes. Heterophile antibodies should be available to be detected on a monospot.
Describe the presentation and workup for Sporothrix infection.
A subcutaneous infection where the lymphatics spread, but it is not continuous. It creates a separated, linear, ulcerating nodular rash that spreads proximal up the extremities. Usually from soil, moss, decaying wood, or cats. To diagnosis, we culture, biopsy or do a fluid sample of an oozy lesion.
Describe the most likely presentation of and the testing for Rotavirus infection.
Rotavirus presents in children most commonly in daycare with symptoms of N/V/D that is usually self-limited, but you can do PCR to test for it.
Describe the risk factors for Pneumocystis and how it will appear on a CT scan of the chest
Pneumocystis has ground glass opacities at the perihilar space of the lungs on CT. Risk Factors include having a viral infection and being immunocompromised, especially in AIDS pts
Describe the risk factors, presentation of, and testing for Giardia.
Giardia is a noninvasive flagellated parasite that cause diarrhea with no bloody stool. It causes disruption of the permeability of the small intestine with disruption to brush border enzymes. Other symptoms include a lot of cramping, nausea, flatulence, and weight loss. Stool antigen detection with ova and parasites.
Describe the risk factors for the 4 dimorphic fungi – Histoplasmosis, Blastomycosis, Coccidioidomycosis, Paracoccidioidomycosis
Blastomycosis: found in the Mississippi, in valleys with warm, moist soil, decaying wood-can’t do serology
Histoplasmosis: found in soil enriched with bat/bird droppings
Coccidioidomycosis: desert areas of Arizona/California (warm and dry)
Paracoccidioidomycosis: Paraguay, had to travel
These are introduced through the respiratory tract. They present like a pneumonia, skin lesion, or have joint/bone involvement. Lesions are widespread, maculopapular, discrete, with central ulcerations.
high platelets
thrombocytosis
high CO2
hypercapnia
low hemoglobin
anemia
lowe platelets
thrombocytopenia
high WBCs
leukocytosis
high RBCs
erythrocytosis/polycytomthemia
high sodium
hypernatremia
high BUN
azotemia
Describe the testing for HHV 1 and HHV 2.
We can do a fourth generation HIV 1/2 immunoassay and if that is negative we can look down other avenues to confirm. If it is positive, we can do HIV ½ antibody differentiation assay to determine which type of infection the patient has.
List the components of a CMP that are not found on a BMP.
total protein, albumin, total bilirubin and liver enzymes
List the ranges and critical values (high and low) for Potassium
Normal 3.5-5.0. Critical > 6 and < 2.5
List the ranges and critical values (high and low) for Sodium
Normal 135-145. Critical <125 and > 155
List the ranges and critical values (high and low) for Magnesium
Normal 1.6-2.6. Critical > 9 and in adults <0.5
List the ranges and critical values (high and low) for Calcium
Normal 8.4-10.2. Critical <6 and > 13
List the ranges and critical values (high and low) for Chloride
Normal 95-110. Critica <85 and >115
Explain the CBC changes associated with bacterial infections
leukocytosis, increase in neutrophils “left shift” increase in immature forms of neutrophils.
Explain the CBC changes associated with viral infections
leukopenia
Explain the CBC changes associated with parasite infections
increased eosinophils
List the strep species that are: alpha, Beta group A, Beta group B
alpha- strep pneumo
Beta group A- strep pyogenes
Beta group B-strep agalactiae
Normal range for RBC
4.7-6.1 for men and 4.2-5.4 for women
Normal range for WBC
5,000-10,000
Normal Range for neutrophils
54-62%
Normal Range for platelets
150,000-450,000
Normal range for hemoglobin
12-16 for women and 14-18 for men
Normal range for hematocrit
34-47 for women and 42-52 for men
Explain the relationship between deep tendon reflexes and electrolyte levels.
Hypermagnesemia leads to hyporeflexia, while hypomagnesemia leads to hyperreflexia
Describe the testing for Lyme disease, including when in the disease course they are used.
Early localized disease: rash is clinical diagnosis only
Early or disseminated or late lyme disease with joint pain, arthralgia, lymphadenopathy- use serology. Do an ELISA and if positive follow up with a Western Blot or another ELISA to confirm due to higher rate of false positives.
What is a gram stain?
stains bacteria and differentiates between + and -
What is an acid fast stain?
used with Mycobacterium, M. avium Nocardia, which don’t have a peptidoglycan layer and can occur in immunocompromised people that are exposed to birds
What is an india ink stain?
dark stain that stains the background/everything, but not the organism, so it shows up bright against the dark. “Negative stain”. Most commonly used with Cryptococcus. The cell wall prevents absorption of stain.
What is a calcofluor white stain?
Is a staining technique specific to fungi
Explain the difference in cell membrane structure in Gram negative versus Gram positive bacteria
Gram negative has a thinner peptidoglycan layer but two layers of cell walls with LPS and they stain pink.
Gram positive bacteria have a thicker peptidoglycan layer and it stains purple.
What sites in the body should be sterile?
CSF, saliva, lower respiratory tract, blood, pericardial fluid, pleural fluid, peritoneal fluid, synovial fluid, bone, and urine straight from the bladder or kidneys
Explain how MacConkey agar and EMB agar distinguish between bacteria.
Differentiates between lactose fermenters and non lactose fermenters
MacConkey: pink and yellow
EMB: green and yellow
List Lactose non-fermenting Gram negative bacteria that would turn MacConkey agar yellow and would have yellow colonies on EMB agar.
Non- lactose: pseudomonas, proteus, Shigella, salmonella
List Lactose-fermenting Gram negative bacteria that would turn MacConkey agar pink and would have green colonies on EMB agar.
Lactose: E. Coli, enterobacter, klebsiella
Explain how catalase is used to differentiate Streptococcus from Staphylococcus
Hydrogen peroxide will bubble indicating the organism is staph.
Explain how sheep blood agar distinguishes between types of Streptococcus.
Alpha: minimal hemolysis, oxidizes and gives green color
Beta: hemolysis, oxidizes and gives green color
Gamma: no hemolysis, gray, normal flora
Explain how serology testing is done, and what indicates a result that supports diagnosis of an infection
Serology detects antibodies against a specific organism in serum in the bloodstream. Presence of antibodies does not differentiate between active vs. prior infections though. We can try to differentiate based on immunoglobulin levels (IgG or IgM) to determine if antibodies are active or latent
Describe the differences in primary versus secondary antibody response to infections
In a primary immune response, the body has never encountered the antigen before, meaning IgG and IgM will both react at similar rates. During a secondary infection or response, IgG will remain elevated for longer than IgM, because IgG deals with acquired immune response with memory cells. This is the basis of vaccinations and helps us determine a patient’s level of immunity.
Explain what a titer is and how it is reported
Titers are a type of immunologic test that measures serology as dilutions. The serial dilution that results with the lower serial dilution that still has antibodies present is our result.
Describe what acute phase reactants are, and list examples
They are proteins whose concentration increases or decreases by 25% in the inflammation process and the changes are brought on by hepatocytes in response to cytokines. In the presence of inflammation there is increased CRP and procalcitonin,and more and there are decreased levels of albumin and transferrin.
Describe what CRP is and how it is used in clinical practice
Their function is to bind to phosphocholine on pathogens and damaged cells to promote the complement cascade and activate phagocytic cells. CRP can be elevated in acute and chronic inflammation. Used to monitor effectiveness of treatment. Normal levels vary with age and gender. Obesity and smoking are risk factors.
Describe what ESR is and how it is used in clinical practice
Measures the rate at which erythrocytes migrate downwards in a tube over 1 hour. Blood from EDTA tube is placed in ESR test tube. Wait 1 hour to see how far the cells fall down from the upper line to determine ESR. This is a tool for tracking of therapy but isnt used for diagnosing. Higher amounts of proteins and especially fibrinogen in the blood cause erythrocytes to form rouleaux which migrate faster and look like lifesavers in a package, they sink faster and cause a higher ESR.
Gram variable bacteria:
mycobacterium
Anaerobic bacteria
Clostridium, Actinomyces, Propionibacterium, Peptostreptococcus. -negative = Bacteroides, Fusobacterium, Campylobacter, Prevotella
List two bacteria that are usually diagnosed with serology
brucella and RMST
List how the following grow on sheep blood agar
Strep pneumoniae - green
Strep viridans- green
Strep pyogenes - green with cleared area
Strep agalactiae- green with cleared area
Explain the appearance of a Clostridium perfringens infection on imaging
There will be crepitus or air bubbles that crackle under the skin and will show up as black on imaging.
Testing for C. Diff
iquid stool, Toxin A and Toxin B, GDH antigen test
Testing for legionella
urine antigen testing
testing for Bartonella
PCR, culture, serology
Testing for bordatella
Lymphocytosis (which is weird because most bacterial diseases cause neutrophila). Clinical, can do PCR
Testing for Mycobacterium tuberculosis
Active: CXR to see if there are cavitary lesions with bacteria
Latent: quant gold with IFN-gamma from T cells. Blood sample.
Testing for Covid
NAAT/PCR with a swab or antigen tests with nasal swab, best if performed 3 weeks after onset of symptoms.
Testing for Flu
rapid antigen test (flu swab), high specificity and sensitivity. PCR, preferred tests for higher risk groups
Testing for HHV 1 and 2
Tzanck smear to see if there are any multinucleated cells
Explain the criteria for a definitive diagnosis of a fungal infection
Must ID fungus and have evidence of an inflammatory response. Identification would be done through culture, DNA sequencing or mass spec. Inflammation would be ESR/CRP or CBC
Testing for Epstein Barr
CBC and peripheral blood smear to see if there are heterophile antibodies
Testing for CMV
quantitative PCR to see if pt has pp65 antigen
Rabies Testing
Skin snip of the back of the head, axilla, saliva sample, blood culture, CSF and do RFFIT tests for antibodies
HIV testing
Screening: 3rd generation or 4th generation immunoassay, also available as rapids. If positive, do antibody differentiation test or a Western blot
Acute: P24 antigen tests
HIV+ patients HIV-1/HIV-2 RNA NAAT tests
Explain how dermatophyte test media is used
Inoculate a slightly deeper skin scrapings or nail fragments and if the test media stays yellow, it is negative. If the test media turns magenta, it is positive for dermatophytes. This can take 1-2 weeks
Sporothrix testing
Fluid sample of oozy lesion and either culture or biopsy
Aspergillus testing
Culture, Galactomannan, Beta-D-glucan. Will be cavitary lesions, aspergilloma or a fungal ball in the lungs will need to be cultured
Cryptococcus testing
imaging and staining with india ink. Will see solid nodules on imaging, in the pulmonary system or the brain. Can cause meningitis.
Describe which parasite infections tend to have associated eosinophilia.
Strongyloides (common in rice paddies), Schistosomes, Filaria, Trichinella, Necator, Toxocara, Ascaris
Describe which parasitic infections can be visualized on a peripheral blood smear, and describe their appearance on the smear.
Plasmodium: rounded rings in the RBC
Trypanosoma: will see a flagellate around the RBCs
Filariae (elephantiasis) :
Baesiosis: maltese cross
Describe which parasitic infections tend to cause ring-enhancing lesions on CT scans of the brain
Toxoplasmosis: cat vector
Neurocysticercosis: worms
Describe the testing for Cryptosporidium
Stool staining and PCR, where the parasite will stain pink
Describe the manifestations of and testing for nematode infection
Stool microscopy, stool antigen testing, PCR, or a heme +stool
Describe Nectar americanus
ingested through eggs and you can cough it up and it goes back down into the lungs. It is found in the US in coastal areas. Larvae penetrate the skin and migrate to the lung then to the intestines where they attach to the wall of the SI and ingest blood causing anemia
Describe Ascaris lumbricoides or roundworm
largest intestinal nematode parasite. Acquired by ingestion of eggs.
What is Fungi mass spec called?
MALDI TOF MS
What does Tinea Versicolor look like on a KOH prep and how long can you leave the KOH on?
spaghetti and meatballs appearance and only about 5 mins
What is the eclipse period?
Period of time after infection before any available test can detect infection.
Describe anthrax
necrotic ulcers that can progress toe eschar. Described as biphastic when inhaled. concern for bioterrorism. Widened mediastinum on CXR, culture OR do PCR, staining, serology
What is the correlated total calcium formula?
(4- albumin+calcium)
When testing a potassium level what kind of stick do you want?
Venous
What is an indication of leukemia?
blast cells in the peripheral blood
What is the most definitive test for active tuberculosis?
Culture
What are common gram negative cocci species?
Moraxella
Diagnostic test for kid that is sick in daycare
Rotavirus antigen test
Magnesium and what other lab value usually go together
Potassium
