CM1- Exam 2 Flashcards
serology
study of Abs and their reaction with Ags, that bind specifically to Ab or T cell receptors, in diagnosis of infectious diseases
immunogen
induces an immune response
polyclonal vs. monoclonal abs
polyclonal:
- cheap
- mixture of multiple Abs derived from multiple cells against multiple epitopes
monoclonal:
- expensive
- derived from 1 cell that has been exposed to 1 epitope
- high specificity and strong avidity
what causes false-negative and false-positive serologic results (3 each)
false neg:
- mutated Ags
- immunocompromising conditions
- may result from competition of IgM and IgG Abs
false pos:
- may result from presence of rheumatoid factor
- cross-reacting Abs
- reactivation of latent organism
direct vs. indirect agglutination testing
- direct → natural carrier particles (ex. RBCs)
- indirect → artificial carrier particles (ex. latex beads coated with Ag)
immunofluorescent assay
Ag or Ab is labeled with substance that can be detected later on and allows for detection of an Ab-Ag reaction
direct (DFA) vs. indirect fluorescent Ab (IFA)
DFA: Ab conjugated to fluorescent tag binds to Ag; antigen detection
IFA: Ab-Ag-Ab sandwich
- Ag (from reagent) of corresponding Ab of interest is fixed to glass slide
- Ab binds to Ag (reagent)
- secondary Ab (fluorescently tagged) binds to primary Ab
enzyme immunoassay (EIA)
based on specific Ag-Ab interaction combined with enzyme-mediated color change for detection
- horseradish peroxidase or alkaline phosphatase
membrane-Bound Immunoassay
based on specific Ag-Ab interaction occurring on membrane support (ex. nitrocellulose or PVDF), which allows for rapid binding and detection of target molecules
- ex. lateral flow assays
2 screening tests for syphilis
- rapid plasma reagin (RPR)
- venereal disease research laboratory (VDRL) test
target (template) vs. probe
- Target (template): sequence you want to find if present in specimen
- Probe: short, single-stranded DNA or RNA oligonucleotide that is labeled and used to detect target
prozone vs. postzone
prozone → too much Ab; not enough Ag
postzone → too much Ag; not enough Ab
- cross-linking does not occur in either
southern blot
detects specific DNA sequences in complex mixture by DNA hybridization
northern blot
similar to Southern Blot, but is used for detecting specific RNA sequences
In situ hybridization
detects specific DNA and RNA sequences directly in cells or tissue sections using complementary labeled probes
RT-PCR
converts RNA into complementary DNA (cDNA) using reverse transcriptase, followed by PCR amplification of cDNA
Real time PCR
quantifies DNA or RNA amplification in real time using fluorescent dyes or probes
Nested PCR
increases specificity and sensitivity by using 2 rounds of PCR with 2 sets of primers; 2nd PCR is found within 1st PCR
Multiplex PCR
amplifies multiple DNA targets in single reaction using multiple primer pairs
3 basic steps of PCR
- denaturation – separates double-stranded DNA
- primer annealing – anneals primers to target DNA
- primer extension – synthesizes new strands of DNA
ways to prevent contamination when performing PCR (4)
- 3 separate areas for template extraction, PCR reagent preparation, amplification
- reagent set up in BSC class II (use UV light to decontaminate surfaces)
- PPE and supplies should stay in designated areas
- clean areas with 10% bleach or commercial solutions designed for decontamination of nucleic acids
catalase
(+) staph
(-) strep
coagulase
(+) S. aureus
(-) CoNS
novobiocin
(+) S. saprophyticus
(-) other CoNS
PYR hydrolysis (pink rxn)
(+) GAS/S. pyogenes or Enterococcus spp.
hippurate hydrolysis (purple rxn)
(+) GBS/S. agalactiae
salt tolerance
(+) Enterococcus spp.
(-) other GDS
bacitracin “taxo A”
(+) GAS/S. pyogenes
optochin “taxo P”
(+) S. pneumoniae
CAMP test
(+) GBS/S. agalactiae
bile esculin hydrolysis
(+) Enterococcus spp.
(-) other GDS
bile solubility
(+) S. pneumoniae
microdase disc
(+) Micrococcus
(-) Staph
streptolysin O vs. S (3 each)
O:
- oxygen labile
- immunogenic
- ASO titer
S:
- oxygen stable
- non-immunogenic
- causes hemolysis on plates
S. aureus infections (4)
- skin/wound infections: folliculitis, furuncles, carbuncles, impetigo, SSS/Ritter disease, abscess
- food poisoning (enterotoxin)
- TSS
- suppurative infection (pus)
S. epidermidis infections (1)
- HAIs: UTIs, pathogenesis (biofilm), sepsis
S. saprophyticus infections (2)
- UTIs
- bladder inflammation
S. pyogenes infections (4)
- pyodermal: impetigo, erysipelas, scarlet fever, wound infections, cellulitis
- invasive: TSS, necrotizing fasciitis (rapid tissue death)
- post-infection sequelae: rheumatic fever, acute post-strep glomerulonephritis
- bacterial pharyngitis aka strep throat
S. agalactiae infections (3)
- invasive disease of newborn (early vs. late onset)
- after female procedures: endometritis, wound infections, tricuspid valve endocarditis
- elderly/immunocompromised: UTIs, skin/soft tissue infections, pneumonia, intraabdominal abscesses, bacteremia, endocarditis
S. pneumoniae infections (4)
- pneumonia
- bacteremia
- meningitis
- sinusitis / otitis media
Enterococcus spp. infections (1)
- HAIs: UTIs, bacteremia, wound infections, endocarditis
Viridans infections (1)
- subacute bacterial endocarditis
Abiotrophia spp. and Granulicatella spp. infections (3)
- bacteremia
- endocarditis
- otitis media
