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74 Cards in this Set
- Front
- Back
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What is the name of the gram-positive rod involved in Listeriosis?
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Listeria monocytogenes or
L. monocytogenes |
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Human disease due to L. monocytogenes generally occurs in what population?
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Prenant women or individuals who are immunosuppressed
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Outbreaks of Listeria have been traced to what types of sources?
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Contaminated milk
Soft cheeses Vegetables Meat |
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Although Listeriosis primarily causes GI symptoms, it can also cause much more invasive syndromes such as...?
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Meningitis, sepsis, and stillbirth
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What 3 proteins mediate the spreading of L. monocytogenes?
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1. internalin
2. hemolysin listeriolysin O. 3. phospholipase C. |
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How is listeriosis diagnosed?
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Culture of bacterium
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How is listeriosis treated? Be specific.
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IV administration of ampicillin or penicillin
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All Salmonella are thought to belong to what single species?
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S. enterica
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Salmonellosis is caused by over 2,000 variations or strains of Salmonella. What is another name for serological variation?
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Serovars
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Describe the characteristics of Salmonella.
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Gram-negative
Motile Non-spore forming Rods |
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T or F. Typhoid Fever is caused by S. Typhi.
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False. Typhoid Fever is caused by S. enterica, it's serovar (strain or variation) is Typhi.
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How is Typhoid spread?
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Ingestion of food/water contaminated by feces of infected humans OR person-to-person contact.
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What is the mechanism of action for Typhoid? Be specific.
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Bacteria colonize in small intestine, penetrate epithelium, and spread to lymph system, blood, liver, and gallbladder. Bacteria then RE-infect the GI tract.
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What is the time frame of the disease Listeriosis?
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Most individuals stop shedding bacteria at approximately 3 months, however in some cases the bacteria still exists in the feces, but individuals show no symptoms.
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How is Typhoid Fever diagnosed?
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Demonstration of typhoid bacilli in blood, urine, or stools and serology.
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What is the serology test termed in reference to diagnosing Typhoid Fever?
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The Widal test
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List treatments of Typhoid Fever.
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Ceftriaxone or Ciprofloxacin
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Name some preventative techniques for Typhoid Fever.
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1. Purification of H2O
2. Prevention of food handling by carriers 3. Complete isolation of individuals carrying disease 4. Vaccine for high risk individuals |
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Which of the diseases studied for quiz 2 is considered to be caused by an "intelligent bacteria"? Why?
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Shigellosis "tricks" the Peyer's patch cells into phagocytosis. Once engulfed, they disrupt the phagosome membrane and are realeased into the cytoplasm where they reproduce. They then invade nearby mucosal cells and cause an inflammatory reaction in the mucosa.
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Where do Shigellae reside? Do they travel?
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They do not usually spread behond the colonic epithelium.
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What is the serology test termed in reference to diagnosing Typoid Fever?
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The Widal test
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List treatments of Typhoid Fever.
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Ceftriaxone or Ciprofloxacin
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Name some preventative techniques for Typhoid Fever.
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1. Purification of H2O
2. Prevention of food handling by carriers 3. Complete isolation of individuals carrying disease 4. Vaccine for high risk individuals |
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Which of the diseases studied for quiz 2 is considered to be caused by an "intelligent bacteria"? Why?
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Shigellosis "tricks" the Peyer's patch cells into phagocytosis. Once engulfed, they disrupt the phagosome membrane and are realeased into the cytoplasm where they reproduce. They then invade nearby mucosal cells and cause an inflammatory reaction in the mucosa.
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Where do Shigellae reside? Do they travel?
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They do not usually spread beyond the colonic epithelium.
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What toxin is produced by Shigella?
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Shiga-toxin (used to be verotoxin)
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Describe the moelcular composition of shiga-toxin.
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Composed of one A protein surrounded by five B proteins.
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Describe the mechanism of action of shiga-toxin.
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STEPS
1. The B proteins attach to host vascular cells, causing internalization of the whole toxin. 2. The A subunit protein is released from B protein and binds to ribosomes (inhibits protein synthesis. |
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Name a specific target of the B protein in shiga-toxin.
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Glomerular endothelium. Damage from toxin on these cells leads to kidney failure.
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In what population is Shigellosis most prevalent?
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Infants and children (ages 1-4), in daycare centers.
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Name and describe the mechanism of action of pathogenic shigellae.
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Type III secretion. This system is used for direct export of virulence factors into target host cells. Some of the 20-30 proteins form a needlelike structure which penetrates the target cell membrane and delievers other proteins through it.
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Shigellosis is considered to be "self-limiting" in adults. What does this mean? Is it self-limiting in all populations?
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Self-limiting means the disease runs its course and doesn't cause major damage. No. In infants and children it may be fatal. Kidney failure and neurological complications are a concern, especially in malnourished infants.
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What are treatements available for Shigellosis? Prevention?
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TREATMENTS:
Trimethoprim-sulfamethoxazole Fluoroquinolones PREVENTION: personal hygiene and clean water |
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What is the major type of food intoxication in the US? What microbe causes it?
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Staphylococcal food poisoning caused by ingestion of improperly cooked or stored food on which S. aureus has grown.
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Describe the microscopic nature and distinguishable characteristics of S. aureus.
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Gram-positive coccus, resistant to heat, drying, and radiation.
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Describe the pathway or mechanism of action of Staphyloccus aureus.
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If allowed in proper conditions (certain foods) they produce heat-stable enterotoxins that make food dangerous while it appears normal.
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Which enterotoxins are said to be "super antigens"? What do these toxins do?
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Enterotoxins A and B stimulate vomiting through the vagus nerve (neurotoxins)
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How are enterotoxins detected?
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Animal toxicity tests or antibody-based methods (titers)
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How many different enterotoxins have been connected to Staphylococcus aureus? Which are the most common?
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13 different enteroxins, of which the following are most common: A, B, C1, C2, D, and E.
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How is Staphylococcus aureus treated?
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Fluid and electrolyte replacement
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What is Traveler's Diarrhea? How is it contracted?
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A rapid acting, dehydrating illness contracted from certain viruses, bacteria, or Protozoa usually absent from the Traveler's normal environment.
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What is the most causative agents of Traveler's Diarrhea?
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Escherichia coli
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What are the 6 categories of E. coli?
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1. Enterotoxigenic (ETEC)
2. Enteroinvasive (EIEC) 3. Enterohemmoragic (EHEC) 4. Enteropathogenic (EPEC) 5. Enteroaggragative (EAggEC) 6. Diffusely adhering (DAEC) |
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Describe the mechanism of action for enterotoxigenic E. coli.
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ETEC produces one or both of 2 enterotoxins that are responsible for the diarrhea and distinguished by their heat stability.
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What are the names of the two enterotoxins released by ETEC (enterotoxigenic E. coli)?
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Heat stable enterotoxins (ST) and heat labile enterotoxins (LT)
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What is the function of Heat-stable enterotoxin?
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ST binds to a glycoprotein receptor, activating guanylate cyclase on the surface if the intestinal epithelial cells. This stimulates the production of cGMP (cyclic guanosine monophosphate) leading to the secretion of electrolytes and water (thus the watery stools)
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What is the function of Heat-labile enterotoxin?
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LT binds to specific gangliosides on the epithelial cells, activating membrane bound adenosine monophosophate (cAMP) resulting in hyper secretion of water and electrolytes
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How do enteroinvasive strains of E. coli cause diarrhea?
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By penetrating and multiplying within the intestinal epithelial cells by the presence of a large plasmid. EIEC may also produce a cytotoxin and enterotoxin.
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Describe the pathway of damage that enteropathogenic E. coli causes.
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EPEC attaches to the brush border of the intestinal epithelial cells, causing effacing lesions.
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Enteropathogenic E. coli is also described as what? Why?
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Known as AE E. coli because of the effacing lesions or "attaching-effacing" (AE) lesions that cause cell destruction.
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AE E. coli is an important cause of diarrhea in what population?
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Children in developing countries.
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What form of enterohemmorrhagic E. coli causes outbreaks of hemmorrhagic colitis in the US?
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E. coli O157:H7, found in 1982
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How does Enterohemmorrhagic E. coli lead to diarrhea?
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EHEC carries bacteriophage- encoded genetic determinants for shiga-like toxins (Stx-1 & Stx-2 proteins) and can also produce AE lesions
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Describe the action or pathway of enteroaggragative E. coli
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EAGgEC strains adhere to epithelial cells, forming clumps of bacteria (thus "aggragative").
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T or F:
Toxins are definitely involved in EAggEc strains. |
F. Toxin involvement is suggested through lesions, but none have been detected yet.
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Name two treatments other than fluid replacement for Traveler's diarrhea caused by E. coli
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Trimethoprim-sulfamethoxazole
Doxycyline |
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How is Traveler's diarrhea caused by E. coli diagnosed?
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Based on traveling history and symptoms. Lab diagnosis via isolation of the type of E. coli from feces and ID using DNA probes, determining virulence factors, and polymerase chain reaction
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Give the microscopic description of Shigellosis
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Gram-negative
non-motile nonspore-forming falcultative (anaerobic) rods |
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What are the two most common types of Salmonellosis?
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Typhimurium
Enteritidis |
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True or false:
L. monocytogenes are not normally found as part of of the GI microbiota in healthy individuals. |
False.
L. monocytogenes are intracellular pathogens, which is consistent in causing illness in individuals with deficient cell-mediated immunity--it CAN be found as part of the normal GI microbiota |
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___________ Salmonella can be found per one gram of fecal sample.
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1 billion
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Another name for Shigellosis is ______________.
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bacillary dysentery
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List the four F's in reference to Shigellosis and its transmission route.
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Food
Fingers Feces Flies |
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T or F
Shigella is restricted to human and mammalian hosts. |
False. Shigella is restricted to ONLY human hosts
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Name the two most common Shigella pathogens.
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S. sonnei
S. flexneri |
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Describe the mechanism of action of diffusely adhering E. coli. (DAEC)
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DAEC adheres over the entire surface of epithelial cells and causes disease mostly in immunologically naive or malnourished children.
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T or F. DAEC has absolutely no virulence factor.
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False. It has been suggested that DAEC may have an undefined virulence factor.
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T or F.
In all E. coli cases, recovery can be without complications. |
False. EHEC (hemmorhagic) damages the kidneys permanently.
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What is the severe hemolytic anemia that leads to kidney failure that is connected to EHEC?
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hemolytic uremic syndrome
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What is the significance of enterohemmorhagic E. coli strain O157:H7?
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It is a major form found in 1982 that causes breakouts of hemmorhagic colitis in the US. Actually incidence of EHEC is under-reported because most labs do not test for non-O157 strains.
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What is hemolytic uremic syndrome?
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it is a sever hemolytic anemia that leads to kidney failure. Stx-1 and Stx-2 have been implicated in the disease.
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Name the strain of E. coli that works by releasing enterotoxins known for their heat stability.
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enterotoxigeneic E. coli (ETEC)
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Name the strain of E. coli that is distinguished by it's ability to invade via the presence of a large plasmid.
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enteroinvasive E. coli (EIEC)
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Which strain of E. coli is known to cause effacing lesions?
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enteropathogenic E. coli (EPEC)
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