ID 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)
-MIC: tells you at what dose/concentration the antibiotic will kill the bacteria
Sample Collected:
→ liquids (body fluids, blood)
→ solid/semisolid (sputum, stool, tissue)
→ Swab from infected site
Growth on Mediums:
→ agar plate, broth, agar in tube
Isolate Organisms
→ Subculture colonies
ID organism via biochem tests
Culture: samples collected, growth, isolataion, identifications
Sample Collected:
→ liquids (body fluids, blood)
→ solid/semisolid (sputum, stool, tissue)
→ Swab from infected site
Growth on Mediums:
→ agar plate, broth, agar in tube
Isolate Organisms
→ Subculture colonies
ID organism via biochem tests
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
→ uses fluorescence in microscopic examination
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
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
lyme disease
2 tiered testing for lyme disease
-1. enzyme immunoassay (EIA) OR immunofluorescence assay (IFA)
- detects total IgM + IgG antibodies (indicate past infxn) w/o differentiating b/w them
-if positive -> and symptoms are <= 30 days -> IgM and IgG western blot (2 EIAs)
-if positive -> and symptoms are > 30 days -> IgG western blot ONLY
-if negative -> consider alternative dx OR if pt with signs/symptoms consistent with lyme disease for <= 30 days, consider obtaining a convalescent serum
osteomyelitis: Population w/ Highest Incidence or Predisposing Conditions organisms
Infection of bone, prosthetic
-staph aureus: all ages, MC causing hematogenous osteomyelitis
-*salmonella spp. : sickle cell disease pts (encapsulated), immunocompromised individuals
-pseudomonas aeruginosa: IV drug use, pts with puncture wound to foot, pts with urinary catheters
-aerobic gram neg rods (enterbacter and proteus): UTI!!!, diabetic foot infections, vascular insufficiency
-aerobic streptococci: pts with bites, diabetic foot lesions, vascular insufficiency
-anaerobic streptococci: pts with foreign body assoc infections, bites, diabetic foot lesions, decubitus ulcers
-mycobacteirum tuberculosis: pts with hx of pulmonary TB, immunocompromised pts
-fungal species (candida and aspergillus): pts with catheter related fungemia, IV drug users, immunocompromised pts
Salmonella → eggs, undercooked chicken, reptiles - turtles
E. Coli → lettuce (manure in soil) beef, milk
C. diff → post ABX use
MC → enterotoxins produced by S. Aureus (dairy, bakery products), Bacillus cereus (reheated fried rice)
acute viral gastroenteritis
Cruise Ship → Rotavirus, Norovirus
● Hand hygiene to prevent spread
● Fecal oral route
nOrO: year round (two Os = round); sapovirus
rota: Winter/fall stomach virus
astrovirus: winter
enteric ADEnovirus: summer (drink lemonADE in summer)
acute bacterial infections
-impetigo: staph aureus, streptococcus pyogenes
- erysipelas: erythematous, very painful, sharply demarcated, RAISED, REGULAR border -> streptococcus pyogenes, streptococcus agalactaiae > S. aureus
- cellulitis: erythematous diffuse, FLAT, with irregular border, deep dermis -> streptococcus pyogenes, streptococcus agalactaiae > S. aureus
-folliculitis- hot tubs, localized inflamed papules containing a small amount of pus -> S. aureaus, pseudomonas (Hot tub!!)
-skin abscess -> raised, tender with central area of purulence, pus is firm then fluctuates -> deep dermis -> staph aureaus
- necrotizing fascilitis: painful area of inflammation with rapid progression to necrosis, bullae, purpura, anesthesia, systemic toxiicty -> monomicrobial form: s. pyogens, clostridium perfringens, vibrio vulnificus; polymicrobial form: enteric gram negative rods and anaerobes.
-dont need to know tx
Dx stained stool specimens
Amoebas - severe colitis
Assoc w/ exposure to water contamination sources
