Exam 8 (Infectious Disease) Flashcards
Pathogen
Organism or agent that can infect individual causing disease
Virulence
Potency/severity of pathogen
Yersinia pestis kills 50-75%
Candida albicans low risk of serious illness
Colonization
Host is carrying organism but no clinical expression or immune response
Infection
Invasion of pathogen causing immune response
Pathogen evasion
Opportunistic infection
Organism invades host and waits to cause disease till immune system is compromized by something else
Mycoplasm
Smallest bacteria,
Not visible under microscope.
Don’t gram stain
Must use acid-fast to see
Capsule
Hydrophilic gel
Protects cell from immune attack
Helps adhesion
Cell wall
Rigid
Prevents lysis
Provides shape for cell
Gram (+) or Gram (-)
Gram positive cell wall make up
Peptidoglycan with cross linked peptide chains.
Hard to get rid of bc of thick membrain.
Resistant to mammalian enzymes except for lysozime.
Teichoic acids help with adhesion and induces inflammatory reaction
How do we attack gram positive cell clinically
Target peptidoglycan with penicillin.
Blocks peptide cross linking.
Causes cell lysis
Gram negative cell wall make up
Impermeable outer membrane containing lipoplysaccharide endotoxin, phospholipid A, and O antigen.
Periplasm is single layer of peptidoglycan that makes beta-lactamase.
Gram stain
- Crystal Violet
- Iodine (mordant) makes crystal violet hang on
- Acetone or ethanol washes out gram negative
- Saffranin dies gram negative
Acid fast stain
Stain poorly
1. Carbolfuchsin dye (mycolic acid soluble) stains red
2. Organic solvent (acetone or ethanol) extracts stain from non-acid fast
3. Methylene blue stains non acid fast
LPS endotoxin
Gram negative
O antigen
H antigen
Exotoxin
Secreted from bacteria into surrounding body fluids.
Local or systemic
A is pathogen
B is recepto binding facilitating A delivery
C reactive protein
APR
Best lab value to judge treatment response.
Rises within hours of infection.
Takes a week to normalize
Erythrocyte Sedimentation Rate
Rises within 2 days of infection
Can rise 3-5 days after antibiotics initiated
Normalizes in 3-4 weeks
Wet mount
Normal saline to identify cells as pathogens
Potassium hydroxide (KOH) to identify fungi
Dark field microscopy
Identifies syphilis spirochetes
Minimum Inhibitory Choncentration
Minimum amount of ABx to prevent growth after 24 hours of incubation.
Minimum Bacteriocidal Concentration
Minimum concentration of ABx that causes microbial death killing 99.9% of colonies in 18-24 hrs
Blood agar hemolysis
Tests bacteria ability to lyse red blood cells.
Hemolysins.
Alpha is partial
Beta is complete
Gama is none
Coagulase test
Coagulase forms fibrinogen into fibrin to form clot
PCR
Polymerase Chain Rxn
Detects RNA or DNA in viruses
Very specific test.
Amplifies nucleiic acid levels