ID juju Flashcards
What are infectious agents?
•Viruses •Bacteria •Fungi •Protozoans •Helminths
What are situations in which infections can occur?
- Organ system specific
- Immunosuppressed ( HIV, Neutropenic)
- post abx use: C. diff
- Diabetes: pseudomonsa MC
- Sickle Cell Disease: salmonella (any encapsulated), splenomegaly
- Prosthetic Devices: foreign device with no defense mechanism.( endocarditis
- S. aureus)
- Travel
MC bacterial infection
pseudomonas
What is a direct stain?
Prep smear of specimen +staining to detect microorganisms.
- ex: Gram Stain
What is the gram stain process?
Patient specimen is applied to glass slide, dried + fixed Slide is subjected to 2 stains
- Gram positive stain purple
- Gram negative stain red
- Nonbacterial, WBC= stain characteristic of cell type Color, shape and arrangement are described in microscopic analysis “Gram positive cocci in clusters”
What are the 4 steps in the process to end up with purple/red staining?
Crystal Violet Iodine Alcohol Safranin
What are some examples of gram positive bacteria?
Gram +:
- S. pneumoniae
- S. Aureus
- P. Aerguinosa
- S.Pyrogens
- C.botulinum
- C.Diptheria
—— Gram
-:
- N. Meningitis
- H.Pylori
- E.coli
- T.palladium
- V.cholerae
- N. gonorrhoea
What are some examples of gram negative bacteria?
Gram
-:
- N. Meningitis
- H.Pylori
- E.coli
- T.palladium
- V.cholerae
- N. gonorrhoea
—– Gram +:
- S. pneumoniae
- S. Aureus
- P. Aerguinosa
- S.Pyrogens
- C.botulinum
- C.Diptheria
What is the gold standard for growing a bacteria?
Culture: isolation of the pure organism
-Definitive identification & antimicrobial sensitivity
- MIC: minimum inhibitory concentration
- moderate to high expense Sample Collection → growth of organisms (aerobic or anaerobic) → isolation of organisms → Identification
What are types of sample collection for culture?
Liquid: body fluids (except not blood!) Solid/semisolid: Sputum, stool, tissue Swab: from infected site like a wound
Culture: process
Sample Collection → growth of organisms (aerobic or anaerobic) → isolation of organisms → Identification
- 1-3 days: longer
-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
What is antigen detection?
- antigens: surface proteins detected with immunofluorescence in microscopic examination
- do not require growing the organism
- immunoasssays that detect soluble antigens
- immunoassays that detect the organism by its reaction to a reagent antibodies
- moderate expense
- manual with microscopic evaluation + fuorescent microscope
Nucleic Acid Detection
•detects the RNA of the infectious agent
- Valuable to detecting difficult to grow or slow growing organisms •HIV viral load •Only looks for that specific organism
- 1-2 hrs: no delay, FAST
- bacteria or viral
What is the issue with nucleic acid testing?
Viral particles can remain in system.You may have recovered and still positive ,you can have partially destroyed viral products in organ system (for ex, covid like 90 days)
What does serology detect?
Detect host *antibodies * that are produced in response to infections
- Immune markers
- syphillis
- see what antibodies are present in response to a disease to dx
- orange/red/fuschia: no antibodies
- yellow/any color change: + antibodies
How is syphillis tested?
Serology
MC types of infections that lead to sepsis
MC:
- skin
- lungs
- GI tract
- urinary tract sepsis: infection you have triggers a chain reaction throughout your body
How do you go about working up an infectious agent?
- List clinical signs /symptoms to identify specific organs and tissues likely to be infected 2. Collect appropriate samples + order appropriate tests to detect the most likely infectious agents (ex: gram stain, bacterial culture) 3. Empiric tx to protect against most likely pathogens 4. When lab identifies organism (s), they preform tests for antibiotic susceptibilities (BACTERIAL ONLY usually) and modify tx necessary to target pathogenic organism (s)
What is SIRS Criteria
Initial infection and 2+ OF THE FOLLOWING:
- Temp > 38 C or
- HR> 90 Bpm
- RR>20 Bpm
- WBC> 12,000 or
What is SEPSIS Criteria
Systemic response to infection
- SIRS AND
- Documented/ highly suspected infection
What is Severe Sepsis criteria?
Sepsis + evidence of organ dysfunction, hypo perfusion or hypotension
What is Septic Shock criteria?
Sepsis induced hypotension:
- systolic BP <90 , despite fluid resuscitation
- evidence of Organ dysfunction, hypo perfusion, or hypotension requires immediate medical attention
Symptoms + tx of septic shock
- Low BP (<90)
- pale and cool arms and legs
- chills
- difficulty breathing
- decreased urine output (vasodilation)
- Mental confusion and disorientation requires immediate medical attention tx:
- supplemental O2
- IV fluids
- abx
Bacteremia
•Blood should be sterile •Infections in organ or tissue can introduce bacteria to the blood stream •can lead to sepsis dx: •Blood culture: 4 bottles/vials total •Skin prep to eliminate skin microorganisms before venipuncture
- 2 samples taken at two different sites
- one aerobic set and one anaerobic set
What is a blood culture?
Lab test used to detect bacteria or fungi in a person’s blood.
-detect their presence by co2 production
- Skin prep to eliminate skin microorganisms before venipuncture
- 2 samples taken at two different sites
- one aerobic set and one anaerobic set positive blood culture: growth of microorganism generating CO2
The presence of microorganisms can indicate
a bloodstream infection such as bacteremia or fungemia, which in severe cases may result in sepsis.
Antimicrobial sensitivity tests are used to determine
Which abx are likely to effectively eliminate an infectious organism by exposing the organism to diff abx in vitro
- dilution method
- disc diffusion method
What diseases involved in tick transmission?
Lymes, Rickettsia/RMSF, Ehrlichia, Anaplasma
What testing is performed for ticks?
PCR and Serological Testing Lyme:
- two
-step testing RMSF:
- rash with endothelial vasculitis
- serological test Ehrlichia:
- lone start tick
- Nucleic acid amplification test Anaplasma:
- deer tick
- Nucleic acid amplification test
RMSF testing
RMSF:
- rash with endothelial vasculitis
- serological test Ehrlichia:
- lone start tick
- Nucleic acid amplification test Anaplasma:
- deer tick
- Nucleic acid amplification test
Ehrlichia what kind of tick and test?
Lone star tick. Nucleic acid amplification test.
Anaplasma, what kind of tick and test?
Deer tick. Nucleic acid amplification test.
Lyme Disease Testing Process
Two tier testing First tier: enzyme immunassay or Immunofluorescence assay
- detects antibodies produced by the body in response to infection
- positive/equivocal (unclear) = confirmatory testing
- negative: no further tests Second tier: confirmatory test:
- analyzes the blood for antibodies specific to different components (proteins) of the Borrelia burgdorferi bacteria
- sx for over 30 days: IgG western blot ONLY
- sx for less than or equal to 30 days: IgM and IgG western blot
- positive results = pt is positive for lyme ds
lyme ds: EIAs first tier vs second tier
First tier EIAs:
- Borrelia antigens
- distinguish between IgM and IgG class antibodies
- IgM = early/recent exposure
- if negative: no further testing second tier EIAs:
- detects total antibodies without differentiating between the antibody classes.
- if second tier EIAs are positive, the final patient result is considered positive
What is fungemia + causes
Candida normal flora in oral and GI tract causes:
- Steroid inhalers
- Nasal steroids– flonase
- Abx therapy
- Neutropenia
- Pts w indwelling lines
Transmission cycle of Plasmodium (Malaria)
- A bite from an infected mosquito 2. parasites travel to liver where they lie dormant for 10 days- 4 weeks 3. parasites leave liver and infect RBCs, then malaria signs and symptoms 4. new mosquito bite you and becomes infected