Infectious disease labs Flashcards
infectious agents
-viruses
-bacteria
-fungi
-protozoans
-helminths
situations for infections
-organ system specific
-immunosuppressed- HIV and neutropenic
-diabetes- pseudomonas MC
-sick cell disease- salmonella (any encapsulated), splenomegaly
-prosthetic devices- foreign object
-travel
direct stains
-preparing a smear of the specimen and then using an appropriate staining technique to detect the relevant microorganisms
-gram stain
-gran + = purple
-gram - = red
-if you started on empiric antibiotics and then you find gram + -> make sure the antibiotic you gave cover gram +
different stains picture
-alcohol- strips gram neg
-if gram neg it would stain red
culture
-gold standard isolation of the PURE ORGANISM
-definitive identification and antimicrobial susceptibility
-typical bacteria
-MIC, minimum inhibitory concentration- minimum dose that will kill
-gives you more than telling you if its gram + and -
-lets you know if bacteria is resistant to antibiotics (MRSA)
-tells you at what dose/concentration the antibiotic will kill the bacteria
antigen detection
-surface protein
-do not require growing the organism
-immunoassays that detect soluble antigens
-immunoassay that detect the organism by its reaction to a reagent antibodies
-rapid test- COVID
nucleic acid detection
-RNA of the infectious agent
-Valuable to detecting difficult to grow or slow growing organisms
-HIV viral load
-Only looks for that specific organism*
-expensive
-1-2 hrs- no delay
-bacteria or viral
serology
-Detect host ANTIBODIES that are produced in response to infection with a particular infectious agent.
-Immune markers
-Syphilis
-see what antibodies are present in response to a disease to dx
process steps
-list clinical signs and symptoms to identify organs and tissue that are likely infected
-collect samples
-order test: gram stain, bacteria culture, fungal culture, nucleic acid amplification tests for viral agents, microscopy for parasites, serologic tests, depending on diff dx
-empiric tx if necessary for most likely pathogen
-lab identifies
-lab does tests for antibiotic susceptibility of pathogenic organisms
-modify empiric tx
sepsis
-Sepsis happens when an infection you already have triggers a chain reaction throughout your body.
-Infections that lead to sepsis most often start in the lung, urinary tract, skin, or GI
septic shock
-life-threatening condition caused by a severe localized or system-wide infection that requires immediate medical attention
-low BP
-pale and cool arms and legs
-chills
-difficulty breathing
-decreased urine output
-Mental confusion and disorientation can develop rapidly
-Emergency tx may include supplemental oxygen, IV fluids, antibiotics, and other medications
bacteremia
-Blood should be sterile
-Infection in organ or tissue can introduce bacteria to the blood stream
-Sepsis
-Blood culture
-Skin prep & 2 samples sent
blood cultures
-A blood culture is a medical laboratory test used to detect bacteria or fungi in a person’s blood.
-Under normal conditions, the blood does not contain microorganisms: their presence can indicate a bloodstream infection such as bacteremia or fungemia, which in severe cases may result in sepsis
antimicrobial sensitivity tests
tick transmission
-Lymes, Rickettsia, Ehrlichia & Anaplasma
-Think time and place?
-PCR and Serological Testing
-Lymes- two-step testing process for Lyme disease.
-Rocky Mountain Spotted Fever- rash with endothelial vasculitis. Serologic test.
-Ehrlichia- lone star tick. Nucleic acid amplification test.
-Anaplasma – deer tick. Nucleic acid amplification test
lymes testing
-First tier EIA that is based Borreliaantigens and detects total IgM and IgG-class antibodies, without differentiating between them.
-If first tier EIA result is neg -> no further testing needed
-If result is positive or equivocal, however, the second tier EIA is performed, which for both versions of the algorithm is based on whole cell sonicate material from culturedBorreliaspirochetes.
-The only difference between the two versions is that in the first version, two whole cell sonicate (WCS) EIAs are done to distinguish between IgM and IgG class antibodies, versus in version two where the second tier EIA detects total antibodies without differentiating between the antibody classes.
-Ultimately, though, if either of the second tier EIAs are positive, the final patient result is considered positive
parasitic infections
-Plasmodium (Malaria)- traveler with febrile illness. One of the largest causes of death in the world. Mosquitos transmission. Seen on smears in the RBC’s.
-Babesiosis- tick transmission. Infect RBC. Hemolysis, fever, anorexia, headache. Self limiting
lumbar puncture results analysis
acute bacterial infections
-impetigo- staph aureus
-dont need to know tx
-folliculitis- hot tubs
fungal infection
bacteria in gastroenteritis
virus in gastroenteritis
protozoan infections of GI
