HY Micro Flashcards
Recombination can occur between 2 virus strains that have a _____ genome (Ex: Herpes)
nonsegmented (double stranded)
refers to the exchange of genes between 2 chromosomes via crossing over within homologous regions.
Progeny can have genomes with traits from both parent viruses.
Recombination
occurs when one virus inhibits replication and/or release of a second virus that is infecting the same cell.
Interference
Phenotypic mixing can occur when a host is ___ with 2 viruses.
coinfected
occurs when a host cell is coinfected with 2 viral strains and progeny virions contain parental genome from one strain and nucleocapsid (or envelope) proteins from the other strain.
Phenotypic mixing
Phenotypic mixing result in progeny acquiring additional traits (ex: enhanced ability to infect new host cells due to different nucleocapsid proteins). However, as the genome is _____, subsequent progeny would not retain these traits.
unchanged
Reassortment refers to changes in genomic composition that occur when a host is coinfected with 2 _____ viruses that exchange whole genome segments.
segmented
Reassortment can cause alterations in surface antigens of the _____ , making it mutagenic (Ex: Influenza)
viral progeny
Reassortment is for ______ genomes
Recombination is for ________ genomes
segmented
non-segmented
Direct uptake of extracellular DNA from a lysed cell or from free floating plasmids
Transformation
*typically causes no genomic change in progeny
They possess the surface proteins hemagglutinin (HA) and neuraminidase (NA), which are virulence factors required for infectivity
Orthomyxoviruses
refers to point mutations in HA and NA genes that slightly alter the product proteins, allowing them to evade immune recognition and possibly increasing infectivity of the virus.
Antigenic drift
a change in species-to-species transmission likely represents a major modification in protein structure that is better explained by RNA segment _____.
reassortment
occurs when 2 viruses infect the same cell and progeny viruses exhibit coat or envelope proteins not coded for by the genetic material packaged within them.
Phenotypic mixing
Influenza epidemics and pandemics are typically caused by reassortment of the RNA segments coding for hemagglutinin or neuraminidase proteins (major antigenic ____ ).
shifts
Bacterial mRNA can be polycistronic, meaning that ____ codes for several proteins.
one mRNA
The transcription and translation of the lac operon proteins is regulated by a single _____, operator, and set of regulatory elements.
promoter
mRNA is polycistronic
Parvovirus B19 replicates in _____ precursors in the bone marrow.
erythrocyte (RBC)
an enveloped virus containing partially double-stranded circular DNA.
An enzyme packed in its virion has RNA-dependent DNA-polymerase activity.
Hepatitis B
Orthomyxoviruses contain a segmented genome, and HA and NA are coded by separate RNA segments. This allows for ______ when 2 distinct strains infect the same cell.
genetic reassortment
Immune defense against Giardia involves CD4+ T helper cell induction of secretory __ production.
IgA
Secretory ___ helps prevent and clear infection by binding and impairing microbial or protozoal adherence to the mucosa.
IgA
IgA deficiency, X-linked agammaglobulinemia, and common variable immune deficiency have a predisposition to developing chronic ____ (protozoa)
giardiasis
*+/– Small-bowel biopsy = villous atrophy & crypt hyperplasia.
is able to obtain new genetic material (which codes for a capsule) from the environment that is released following the death and lysis of neighboring bacterial cells (Transformation) thus becoming VIRULENT.
S pneumoniae
Bacteria that have the innate capacity to undergo transformation are said to be naturally competent and include :
Streptococcus (S pneumoniae, Viridans)
Haemophilus
Neisseria
Bacillus
Transfer of infected Bacterial Host DNA to another newly infected bacteria via a Bacteriophage
Transduction
While replicating within a host bacterium, a bacteriophage may accidentally incorporate host bacterial DNA into the phage particle.
Transduction
By this mechanism, bacteria can acquire genes for virulence and antibiotic resistance from another bacteria.
Transduction (via a bacteriophage)
Phage mediated DNA transfer
Transduction
_____ form of one-way DNA transfer performed by bacteria carrying a plasmid with the fertility (F) factor.
Conjugation
Pilus mediated DNA transfer
Conjugation
The process begins with a pilus, forming a direct connection with the receiving bacterium.
Then transferring a single DNA strand with the F factor to the recipient.
After which, complementary DNA strands are synthesized.
Conjugation
S. Viridans dextrans colonize/adhere to ____ at sites of endothelial trauma on heart valves
Fibrin- Platelet aggregates
Spore-forming bacteria can survive boiling temperatures. ____ & _____ species are common pathogenic spore-forming bacteria.
Bacillus
Clostridium
Endothelial surface glycoproteins mediate binding of ____ cells to endothelium
immune (Neutrophils)
Subendothelial collagen and _____ form the subendothelial fibrous cap over the central core of an atherosclerotic plaque and are potent platelet activators.
glycosaminoglycans
___ and ___ have a dormant hepatic phase (hypnozoite) that may reactivate several months after return from an endemic region (if not treated with primaquine).
In contrast, ____ does not have a dormant hepatic phase; it matures in (and is released from) the liver over 8-30 days.
P ovale
P vivax
P falciparum (not dormant)
In Africa, where chloroquine-resistant _____ is endemic, common chemoprophylaxis regimens include atovaquone-proguanil, doxycycline, and mefloquine.
Plasmodium falciparum
____ is a schizonticide that actively destroys replicating parasites within red blood cells. However, it is inactivated in the liver and has no efficacy against hepatic schizonts.
Mefloquine
*must be taken for 4 weeks after return to ensure liver parasites burst and inhabit RBCs
Cases of P falciparum in Africa are usually resistant to.
chloroquine
___ chemoprophylaxis for malaria must be continued for 4 weeks after return from an endemic region to ensure the elimination of hepatic schizonts (which develop in the liver over 8-30 days).
Mefloquine
In the bloodstream, endotoxin causes a severe inflammatory response mediated by ___ & ___ from activated macrophages.
tumor necrosis factor-alpha
IL-1
Intestinal ____ is a property of gastroenteritis caused by Salmonella, Shigella, EIEC, Campylobacter jejuni, & Entamoeba histolytica. This frequently leads to bloody or hemorrhagic diarrhea (due to mucosal cell necrosis).
invasion
acts by inactivating the 60S ribosomal subunit in human cells, thereby inhibiting human cell protein production, leading to cell death.
Shiga Toxin
Shiga-like Toxin
“Stacked-brick” intestinal adhesion is characteristic of ____.
These organisms adhere to human jejunal, ileal, and colonic mucosa in an aggregative, or stacked-brick, pattern and do NOT invade.
It causes persistent diarrhea in infants in developing countries and those with advanced immunosuppression (AIDS).
enteroaggregative E coli (EAEC)
ETEC produces plasmid-encoded, ____ and ____ enterotoxins which cause watery diarrhea which self resolves in a few days.
heat-labile (LT, choleragen-like)
heat-stable (ST)
ETEC, Heat-Labile toxin (LT) activates
adenylate cyclase, leading to increased intracellular cyclic AMP
ETEC heat-labile (LT) toxin is similar to
Cholera- Like enterotoxin
ETEC Heat-stable Toxin (ST) activates
guanylate cyclase leading to increased intracellular cyclic GMP
non-Lactose fermenting bacteria turn what color on MacConkey Agar
White colonies
During Glucose fermentation
____ produces acid & ____ produces gas.
Shigella (Acid) Escherichia coli (Gas)
Generate Black Hydrogen Sulfide (2)
Salmonella
Proteus
Do NOT Generate Black Hydrogen Sulfide
Shigella
Lactose Fermenters
E. coli Enterobacter Klebsiella Serratia (slow) Citrobacter (slow)
Shigella is transmitted via the __ route and is never a component of the normal bacterial gut flora (non-motile).
fecal-oral
Shigella INVADES the gastrointestinal mucosa, particularly via the M cells in the ____ .
After cell entry, Shigella is able to lyse its containment vacuole and enter the cytosol. It then can induce apoptosis and spread to adjacent cells via protrusions created through HOST-cell _____.
Peyer’s patches
actin polymerization
*Shiga toxin is NOT the main pathogenic factor. INVASION is.
can cause inflammation and enlargement of the lymphoid tissue around the appendix and terminal ileum (“pseudoappendicitis”), leading to right lower quadrant pain that can be confused with acute appendicitis.
Y enterocolitica
proliferates in the LNs and grows in the cold
_____ phosphorylates Acyclovir to its active form.
thymidine kinase
