Lecture 10 Flashcards
What are the characteristics of invasive Enterobacteriaceae pathogens?
gram- rods causing intestinal disease in the large intestine (sometime part of small intestine) leading to bloody diarrhea
What is the reservoir for invasive Enterobacteriaceae pathogens?
animal or human microbiota
What is a common form of treatment against invasive Enterobacteriaceae pathogens causing diarrhea?
antibiotics
What are the 3 species of bacteria that causes dysentery diarrhea?
Shigella (and closely related EIEC strains), Salmonella and EHEC noninvasive strain
How are Shigella and EIEC similar?
Shigella is another variant of E. coli
What are two types of Salmonella diseases?
Salmonellosis (dysentery diarrhea) and typhoid fever (non-enteric disease)
What disease does a non-invasive EHEC strain cause?
hemorrhagic colitis
What is dysentery?
disorder of digestive system (large intestine or colon) resulting in severe diarrhea (contains blood, mucus, and pus in feces)
What is dysentery characterized by?
frequent pooping includes cramps and pain
What are the 4 Shigella species?
S. dysenteriae (serogroup A) = A dyss (diss) | S. flexneri (serogroup B) | S. boydii (serogorup C) = Chef Boy(ar)dii | S. sonnei (serogroup D)
What are the characteristics of Shigella?
non-motile; same characteristics as E. coli
Where is S. flexneri common in?
most studied out of the 4 species; common in developing countries (we Be “flexin” on developing countries = we “show off” how forward we are, Be = serogroup B)
Where is S. sonnei common in?
developed countries (ie: USA = California = always “sonnei” in California = vitamin D (serogroup D))
How common is Shigellosis?
very common
What age group do most deaths worldwide occur with?
kids under 10
How many Shigellosis cases/year in the US?
~450,000
What is the reservoir for Shigellosis?
strictly human = same for EIEC since they are similar
What are the 2 methods of transmission of Shigella?
direct contact and fecal-oral transmission
How does fecal-oral transmission occur?
water contaminated with feces or flies sit on feces and then sit on our food
What are the 3 symptoms of Shigellosis? How long does it take after infection for symptoms to develop?
abdominal cramps, fever, dysentery || 1-3 days
What is the Type II secretion system?
2-step process to deliver toxin from bacteria to inside host
What is the Type III secretion system?
secreted protein is delivered directly from microbe into host cell via an injection-like process that requires a complex of proteins called an “injectisome”
What is the 2-step process of the Type II secretion system in gram– bacteria?
toxin first secreted into periplasmic space and assembles into 4º structure »_space; toxin transferred across outer-membrane to bind onto host-cell surface receptor to be taken in
How does Shigella use the Type III secretion system?
uses it to transfer proteins that cause the host cell to uptake the bacteria, involves the formation of the flagella to inject proteins through
What are the virulence factors of Shigella?
Ipa proteins, IcsA autotransporter, and Shiga toxin
What are the Ipa proteins as a virulence factor of Shigella?
group of proteins that are secreted via the Type III secretion system
What is the IcsA autotransporter as a virulence factor of Shigella?
protein that mediates intracellular motility by helps pathogen bind to the cytoskeleton of the host cell and uses it to move within the cell and spread onto neighboring cells
What is the Shiga toxin of Shigella?
AB exotoxin that kills intestinal epithelial and endothelial cells
What are autotransporter proteins?
proteins that don’t rely on a transport system because it transports itself
What is the invasion strategy of Shigella/EIEC?
INDIRECTLY invades epithelial cells by crossing between adjacent cells and invade Through the Basal Side of cell; can Directly invade M cells
What is the invasion strategy of Samlonella?
DIRECTLY invades epithelial and M cells
What are M cells?
cells of the immune system
What are 3 ways we can detect/diagnosis Shigella in an individual?
culture organism from fecal sample || perform biochemical assays and agglutination rxns || PCR-based assay
What is the treatment of Shigellosis?
replacement of fluids with electrolytes while administering antibiotics to reduce severity and duration of the disease
What vaccines are available for Shigellosis?
none, currently under development
Why would you want to use antibiotics to treat Shigellosis?
damage is so severe = no time to wait for immune system to clear it up
What are the differences in Salmonella species due to?
antigenic epitopes
Which species of Salmonella are we discussing?
S. enterica serovar Typhimurium and S. enterica serovar Typhi
What group does S. enterica serovar Typhimurium belong to?
Group B
What group does S. enterica serovar Typhi belong to?
Group D1
What do salmonella cells use to attach to their host cells?
pili
What disease does S. enterica serovar Typhimurium cause?
Salmonellosis
What is Salmonellosis?
gastroenteritis characterized by fever, nausea, vomiting, cramps, bloody OR non-bloody diarrhea
What is the reservoir for S. enterica serovar Typhimurium?
human, livestock animals, lizards/reptiles
What is the mode of transmission for S. enterica serovar Typhimurium?
zoonotic disease = can consume infected livestock (ie: chicken/eggs) or come into contact with infected animals
How common is Salmonellosis in the US?
more than 1million cases/year
What are the 4 virulence factors of S. enterica serovar Typhimurium?
2 adhesins = type 1 pili and curli (a type of pilus) || 2 Type-III-secretion systems = Sip proteins or Ssp proteins
How many Type III secretion systems does S. Typhimurium have?
2
Why would a pathogen need 2 different type-III secretion systems and not just one? (2 reasons)
regulate which of the 2 protein-groups need to secrete since not both are expressed at the same time || protein-group A is being used for pathogen-host-cell interaction and protein-group B will be used at different stage of infection
What are ways to prevent Salmonellosis?
eliminating bacteria from food with proper cooking and vaccinating chickens using vaccine against S. enterica serovar Typhimurium
What vaccine are available against S. enterica serovar Typhimurium?
none for humans thus far but one for chickens
What is a treatment used against Salmonellosis?
use of antibiotics are NOT recommended; oral rehydration therapy
What is S. enterica serovar Typhi?
similar to S. enterica serovar Typhimurium but found a way to escape the GI tract and infect other parts of the body
What disease does S. enterica serovar Typhi cause?
Typhoid fever
What is typhoid fever?
systemic disease infecting liver, spleen and bone marrow
What are some symptoms of typhoid fever?
fever/headache, myalgias, anorexia, GI symptoms but not a true GI disease
What is the reservoir for S. enterica serovar Typhi?
strictly humans = not zoonotic
What is the method of transmission of S. enterica serovar Typhi?
indirect oral-fecal route
How common is typhoid fever worldwide?
more than 15mil cases
What is a characteristic of typhoid fever?
red spots seen on skin
What samples must you collect to diagnose someone who is infected with S. enterica serovar Typhi and has typhoid fever?
blood sample = detectable during early stages of infection || fecal and urine sample = detectable during late stages of infection
Why does the amount of S. enterica serovar Typhi decline in the blood as the infection progresses?
bacteria exits blood to move into other organ systems
What is used to treat typhoid fever?
antibiotics
In order to prevent typhoid fever, what are the 3 vaccines available for use?
must be vaccinated especially when travelling || whole-killed bacterial vaccine, Vi antigen vaccine, and oral live vaccine
Why is the whole-killed bacterial vaccine for typhoid fever no longer recommended?
side effects emerged due to virulence factors present from the process of making the vaccine when the bacteria was killed
What is the Vi antigen vaccine for typhoid fever?
isolated one of the protective virulence factors and incorporated it into a vaccine
What is the Oral-live vaccine for typhoid fever?
attenuated the pathogen to be used as a vaccine
What strain is the non-invasive EHEC that causes hemorrhagic colitis?
O157:H7
What is the reservoir of EHEC O157:H7?
humans and animal = zoonotic disease
What is hemorrhagic colitis?
initially secretory diarrhea followed by bloody diarrhea with cramps and no fever
How many cases/year does hemorrhagic colitis occur in the US?
~73,000
What is the mode of transmission of EHEC O157:H7
via contaminated food, usually undercooked ground beef, unpasteurized milk/juices, uncooked produce
What are the virulence factors of EHEC O157:H7?
Shiga toxin and EaeA adhesin
What does the EaeA adhesin do? What is the consequence of the action?
causes actin rearrangement which damages the host = no need to invade to cause damage
What is a treatment against hemorrhagic colitis?
use of antibiotics (controversial = depends on views of doctor)
What are 3 ways to prevent infection from EHEC O157:H7?
pasteurize dairy products (doesn’t sterilize), irradiate beef meat, good hygiene
