Genetics, Vaccines, Diagnostics Flashcards
what is the general mechanism of gene transfer
-transformation
-conjugation
-transduction
define trasnformant
-cell that has taken up recipient DNA by transformation
define competent
-bacteria that can take up DNA naturally without artificial treatment
define homologous recombination
-identical or similar regions of DNA align and exchange by excision repair
-aka allelic exchange, strand replacement
define complementation
-mutated DNA expressed on plasmid (in trans) will correct the mutation
what type of DNA can bind to cells
double stranded DNA
what type of DNA can be taken up
single stranded DNA
what can induce competence
-calcium treatment of electroporation
parts of bacteriophage
-head
-tail
-fiber
what are bacteriophages
bacterial viruses
what is transduction
-process of transferring DNA form one bacterium to another by phage
lysogeny
-cells do not lyse, but phage DNA integrated into and replicates in host cell DNA
-determined by differences in G and C content of bacterial DNA
salmonella virulence factors
-O antigens (LPS)
clostridium botulinum virulence facotrs
types C and D toxigenic when infected by certain phage
e. coli virulence factors
-lysogenic lambda phage - gene encoding host cell envelope protein that provides serum resistance
Corynebacterium diphtheria virulence factors
-B prophage carrier of diphtheria toxin tox gene
vibrio cholerae virulence factors
-cholera toxin genes expressed on prophage
what is a prophage
phage that has integrated into the genome
extrachromosomal pieces of DNA
-autonomously replicating – independent of chromosomes
plasmids definition
-genes of unknown origin
-often not needed for growth
-may contain genes encoding virulence factors
F factor definition
-fertility factor
-genes that promote replication and transfer of factor to recipient cells
-conjugation
R factor definition
-F factor + genes encoding resistance to specific antibiotics
-RTF adn R determinants
what is RTF
-resistance transfer factor
-encodes origin of replication, sex pilin genes
what are R determinants
-genes encoding antibiotic resistance, heavy metal resistance, virulence factors, insertion sequences
transposons
-mobile genetic elements
-jump form on region of chromosome or plasmid to another
mechanism of transposition (jumping)
-N element contains gene encoding transposase, binds to IR sites, mediates excision and insertion
net effects of transposon movement
-mutation resulting from insertion into middle of another gene
-neutral event – insertion next to intact gene
-excision – can carry along a neighboring gene
live vaccines
-attenuated
-limited growth in host
-possible reversion to virulence
killed vaccine
-chemically inactivated whole cells
-stimulate only short Th1 response
-not very effective
subunit vaccines
-has to be mixed with adjuvants to be effective
live recombinant vaccines
-gene for antigen expressed in a microbe
DNA vaccine
- gene encoding antigen expressed directly in immunized host
-still need to find way to avoid gene silencing by host
recombinant DNA technologies
-targeted gene mutation
-overexpression of genes
what can you use a plasmid containing a transposon for
-transform a pathogen and screen for KanR clones
type I transposon
-not affected
-gene interrupted is not a virulence gene
type II transposon
-affected
-gene interrupted is a virulence gene
sensitivity of DNA based test
-high sensitivity
-can theoretically detect presence of a single organism
specificity of DNA based test
-high specificity
-can detect specific genotypes
-can determine drug resistance
-can predict or confirm virulence
speed of DNA based test
-quicker than traditional culturing for certain organisms
uses for DNA based tests
-culture identify and confirmation
-low numbers or difficult to isolate and grow
-organisms present in small volumes in specimen (intraocular fluid, forensic samples)
-molecular epidemiology (identify point sources for outbreaks)
-zoonotic and highly infectious agents (minimize hazards)
-non viable organisms (good for vaccines)
disadvantages of using DNA based test
-expensive
-must have goof clinical data to support infection by that organism – highly specific
-will miss new organisms unless sequencing done
problem with mixed culture infections
what does PCR do
exponential amplification of DNA
brucellosis, causitive agent
-zoonotic disease
-causative agent is gram negative cocco bacillus genus Brucella
what does brucellosis do
abortion in livestock, caused by Brucella abortus
indirect diagnosis of brucellosis
serum, serology, antibiotics to O side chain
direct diagnosis of brucellosis
culture, identification
issues with diagnosis brucellosis
-Brucella grows very slow
-biochemical phenotyping requires multiple tests
-vaccine strain RB51 can cause abortions in pregnant cows
what does real time PCR signify
data collection and analysis occur as a reaction proceeds
advantages of real time PCR
-fast
-can multiplex analysis – 4-5 different fluorescent signals generated
-can be automated for large sample numbers
MALDI-TOF
-matrix assisted laser desorption ionization time of flight
-doesn’t give wrong name when can’t identify something
