complement fixation TORCH Flashcards
definition
a classical technique for detection/ID of the presence of Ag-Ab complexes
basic principle
-complement binds to Ag-Ab complex
-when Ag is an RBC, causes lysis
-complement proteins are heat labile & get destroyed by heating at 56 celcius for 20-30 mins
sheep RBCs are used as an indicator to show utilization of availability of complement
-complement IS fixed: no lysis (+)
-complement NOT fixed (available): RBC lysis (-)
CFT principle
Ag-Ab complex forms and interacts with complement proteins & gets “fixed”
-after fixing, complement degrades or gets cleaved into a & b fragments
complement fragments
-C2b (larger) remains attached to Ag-Ab complex
-C2a (smaller) separate 7 act as chemokines
-C2a signals macrophages for engulfment of complex & destruction of antigen (in vivo)
positive CFT
-Ab in sample + Antigen + complement = Ag-Ab complex fixed with complement
-no hemolysis
negative CFT
-sample with no Ab + antigen + complement = free complement
-antigen + Ab in indicator system (RBC) = Ag-Ab complex
-Ag-Ab complex + complement = fixed complement
hemolysis
CFT components
antigen: soluble or particulate
antibody: human serum
complement: pooled serum obtained from 4-5 guinea pigs
erythrocytes: sheep RBCs
amboceptor (hemolysin): rabbit ab to sheep RBCs prepared by inoculating sheep RBCs into rabbit
neonatal sepsis definition
clinical syndrome of systemic illness accompanied by bacteria occurring in first month of life
early onset neonatal sepsis
-first 5-7 days of life
-multisystem fulminant illness with prominent respiratory symptoms
-high mortality: 5-20%
-gotten from mother’s vagina
late onset neonatal sepsis
-most common after first week of life
-less association with obstetric complications
-identifiable focus
-maternal genital tract or human contact
nosocomial sepsis
-high risk newborns
-related to: underlying illness, flora in NICU, invasive monitoring
-breaks barrier function of skin & intestine: opportunistic infection
-necrotizing enterocolitis (NEC), meningitis & sepsis
neonatal sepsis causative agents
-group B strep
-gram neg enterics (e. coli)
-listeria monocytogenes, staph, H. flu, entercocci
group b strep
-lyse blood agar
-beta hemolysis
-+ gram stain
e. coli
-lactose fermenter (pink on MAC)
-negative gram stain
