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28 Cards in this Set

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  • Back
Typhoid fever is so named because it bears a superficial resemblance to typhus, a rickettsial disease, despite that the two diseases are quite different. TRUE/FALSE
What causes Typhoid fever?
It is caused by the typhi serovar of S. enterica and characterized by a progressive, invasive infection that leads eventually to septicemia.
What are the symptoms of Typhoid fever?
Fever, diarrhea and abdominal pain. It infiltrates the mesenteric lymphnodes and phagocytes of the liver and spleen. occasionally, the small intestine may develop ulcers and perforations.
Does Salmonella possess a virulence factor?
There is believed to be an island of genes in Salmonells that seems to confer virulence on the bacterium.
How is salmonella transmitted?
Animal products such as meat and milk can be readily contaminated during slaughter.
It has been spread via rodent feces.
There was a breakout in Colorado after visitors were exposed to the railings of the Kimodo dragon exhibit.
is there a treatment protocol for Salmonella?
Uncomplicated cases of Salmonella are treated with fluid and electrolyte replacement. if the disease is severe, Trimethoprim-sulfamethoxazole is recommended.
Typhoid fever is always treated with antibiotics.
Some may carry the organism unsymptomatically in their gall bladder.
What are Shigella?
They are Gram - straight rods, nonmotile and non spore forming. They are usually human parasites, but will infect apes.
Stool culture is still the gold standard for identification in the case of Shigella. TRUE/FALSE
hich serovar causes the most severe case of shigellosis?
Shigella dysenteriae, though it is uncommon in the US.
The two most prevalent strains are S. sonnei and flexneri.
Are nausea and vomiting common signs of Shigellosis?
Yes. Fever and abdominal pain may accompany this as well. Diarrhea with blood from an infectious source is usually referred to as dysentery.
What is the pathogenesis of Shigella?
Shigella invades the villus cells of the large intestine, rather than the small. It is not as invasive as Salmonella.
How does Shigella enter the intestinal mucosa?
It enters the intestinal mucosa by means of lymphoid cells in Peyer's patches. Once there, it instigates an inflammatory reaction that causes extensive tissue destruction.
Does Shigella possess an endotoxin?
Yes. The release of endotoxin causes fever. Enterotoxin, an exotoxin that affects the enteric or GI tract damages the mucosa and villi. heavy bleeding and mucus secretion result.
What is the Shiga toxin?
It is a heat labile exotoxin, and appears to be responsible for the more serious damage to the intestine as well as other systemic effects, including injury to nerve cells. It is an A-B toxin.
What is the A-B toxin?
The B portion of the toxin attaches to host cells, and the whole toxin is internalized. Once inside, the A portion of the toxin exerts its effect. In the Shiga toxin, the A portion binds to ribosomes, interrupting protein synthesis and leading to the damage.
How is Shigella transmitted?
Aside from the usual oral route, it is also acquired through direct person to person contact, due to the small required dose of 10-200 bacteria. Lax sanitation appears to be a prime factor.
Shigella can establish a chronic carrier condition in some people that lasts several months. TRUE/FALSE
What is the general treatment for Shigella?
What is a particularly strain of E. coli?
E. coli 0157:H7 and its close relatives are the most virulent. A particularly virulent form of E. coli is the enterohemorrhagic E. coli or EHEC.
What are the signs of E. coli 0157:H7?
Mild gastroenteritis with fever to bloody diarrhea.
About 10% of patients develop hemolytic uremic syndrome(HUS), a severe hemolytic anemia that causes kidney damage and possible failure.
Neurologic symptoms such as blindness, seizure and stroke are also possible. Young children are more commonly stricken.
What is the pathogenesis of this form of E. coli?
This bacterium owes much of its virulence to shiga toxins, because they are identical to the shiga exotoxin secreted by virulent shigella species.
Sometimes this E. coli is referred to as STEC(shiga toxin producing E. coli). The shiga toxin genes are present are present on bacteriophage in E.coli, but are on the chromosome of shigells dysenteriae.
Are there any other virulence determinants for EHEC?
Yes. They have an ability to efface enterocytes which are gut epithelial cells. This is done via a set of bacterial proteins, one called, intimin, used for intimate attachment to host cells.
What is the type 111 secretion system?
Another set of proteins enables the bacterium to construct a complex bridging system between E. coli and host cell membranes, which permits E. coli to insert its products into the host cell.
is there a particularly interesting characteristic regarding the type 111 pipeline system?
One of the products sent through the type 3 pipeline is a protein that the bacterium inserts into the host cell membrane so that it will become a receptor for the bacterial intimin protein.
Ground beef is more dangerous than steaks or other cuts of meat regarding E. coli infection?
True. The bacterium is a natural habitat of the GI tracts of cattle. When intestinal contents contact the animal carcass, so bacteria are confined to the surface of meats. Ground beef is ground up and the bacteria remain viable throughout the batch. It is important to cook hamburger meat completely through.
Regarding culture and diagnosis, presence should be confirmed with stool culture or with newer techniques such as Elisa and PCR. TRUE/FALSE
Is the hamburger meat more dangerous today than it was 30 years ago?
Yes. The emergence of this pathogen in the early 1980s has resulted from a regular E. coli picking upthe shiga toxin from shigella.
Is ther treatment for this species of E. coli?
Antibiotics are contraindicated for this infection. They may augment pathology. Antimotility drugs are contraindicated as well. Supportive therapy remains the only viable practical option.