Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key


Play button


Play button




Click to flip

52 Cards in this Set

  • Front
  • Back
Describe Salmonella based on the following:

members of which family


Gram-pos or neg

oxidase pos or neg

fermentaton status

family Enterobacteriaceae

Gram-negative rods

oxidase negative

ferment glucose--produce gas and hydrogen sulfide (usually do NOT ferment lactose)

most are motile
What are teh three species of Salmonella?

Which has the most serotypes?
: S. typhi (one serotype), S. choleraesuis (one serotype), and S. enteritidis (more than 2000 serotypes, all formerly considered as individual species. Scientists differentiate these usually by the city where the strain was isolated)
What is another way of classifying Salmonellae?
based on DNA homologies--all under Salmonella enterica (or Salmonella chleraesuis)--7 subgroups
What is the simplistic classification system of Salmonellae?
6 serogroups A, B, C1, C2, D, E

Each of these groups contains many "species" that may be quite different in other respects.

Each of these groups contains many "species" that may be quite different in other respects.

Each of these groups contains many "species" that may be quite different in other respects.

Each of these groups contains many "species" that may be quite different in other respects.
What do Salmonellae produce from glucose?

What is the exception?
gas--hydrogen sufide

S. Typhi does not produce gas
How many cells of Salmonella is needed for the development of symptomatic disease?
Although exposure to Salmonella is frequent, a large inoculum (100 thousand to 100 million cells)
What is the most common age for individuals to be diagnosed with Salmonella infections?
usually diagnosed in the United States in children under the age of 10.
Where does Salmonella grow in the host?

Does Salmonella produce exotoxins? Endotoxins?
intracellular pathogen, surviving and growing within epithelial cells and macrophages

No exotoxins, yes endotoxins
What are the 3 most important virulence factors of Salmonella involved with?

What symptoms is this especially true for? Unclear?

serum resistance

survival within macrophages.

This is especially true for enteric fever and septicemia. In gastroenteritis, the picture is less clear.
How does genetic regulation of enterotoxins aid Salmonella in virulence?
so that they are not expressed in vitro, but are induced when the bacteria enter macrophages.
How do pathogenicity islands affect Salmonella? More specifically, what do SPI 1 and SPI 2 do?
These large blocks of VIRULENCE GENES encode such functions as

invasiveness (SPI1)

and survival inside macrophages (SPI2).
What type of protein do both SPI 1 and 2 carry? What does this protein do?
Type III protein secretion systems which inject bacterial effector proteins into target host cells.

These injected effector proteins interact with intracellular host cell components, such as the cytoskeleton, and modify host cell activity in ways that favor successful pathogenesis by Salmonella.
How does invasion of epithelial cells and macrophages by Salmonella occur?

What is the result?
"trigger" mechanism, in which Salmonella effector proteins cause actin filament polymerization and thus induce "ruffling" of and macropinocytosis by the host cell membrane.

results in the internalization of the bacterial cells inside large macropinocytotic vacuoles.
What are the 5 virulence factors of Salmonella (2 in addition to the 3 from earlier)?
1. Invasiveness of epithelial cells

2. Survival within macrophages

3. Serum resistance proteins

4. Lipopolysaccharide (endotoxin, serum resistance)

5. Capsule, Vi antigen (antiphagocytic against PMN's, serum resistance)
What are the 4 forms of Salmonella infection?
-Enteric fever



-Asymptomatic carriage
What types of fever does Enteric fever caused by Salmonella cause?
typhoid and paratyphoid fever
What causes typhoid fever?

How is typhoid fever characterized?
S. typhi

characterized by high fever and abdominal symptoms.

Enteric fevers caused by other Salmonellae are generally milder.
What causes paratyphoid fever?
S. paratyphi A

S. schottmuelleri (formerly S. paratyphi B)

and S. hirschfeldii (formerly S. paratyphi C).

(Several of the above species are not included in the 3-species system of Salmonella classification, and are now considered serotypes of S. enteritidis.)
Is typhoid fever a diarrheal disease? How is it spread?
not primarily a diarrheal disease

infection is by the fecal-oral route

bacteria are shed in stool at some stages of disease.

BUT during the invasion phase of infection patients may be constipated.
How is typhoid fever diagnosed?
systemic infection with organisms present in blood (although not at high titer), and several internal organs.
What serves as host to S. typhi and S. paratyphi?
humans only
Is typoid fever common in the US?

Is the mortality rate high?

What is the MAJOR source of infection?

What does the treatment involve?
About 400 cases occur each year in the US.

Mortality can be significant.

Asymptomatic carriers are a major source of infection.

Could involve available vaccines, but only used in special circumstances, i.e. if you'll be around someone with typhoid
How can septicemia be detected?
high #'s of bacteria in the blood
How do primary and secondary septicemia differ?
primary--bacteria in the blood at lower level, consumed by macrophages

secondary--bacteria won't die in the macrophage. Enters bloodstream--higher titer
Why ypes of salmonellae are most likely to cause septicemia?
All Salmonellae can cause sepsis, although this is most common with S. choleraesuis and S. dublin.
What infections can occur secondarily to septicemia?
Secondary to the blood infection, localized suppurative infections such as :



septic arthritis

can occur in up to 10% of patients.
What type of infection is the most common due to Salmonellae?
Gastroenteritis (enterocolitis more correct)
How logn after consumption of contaminated food or water do people experience symptoms of gastroenteritis?

What are the symptoms?

How is this treated and how long does it take?
6 to 48 hours after consumption

nausea, vomiting, and diarrhea as the initial presenting symptoms.

loose stools, moderate volume, without blood or mucus, although voluminous or bloody stools may sometimes occur.

Fever and abdominal cramping are common.

Symptoms persist from 2 days to a week before spontaneous resolution.
Which would be a better term for Salmonella infection: "food poisoning" or "foodborne infection" ? Why?
FOOD BORNE INFECTION: since the disease is due to live bacteria in the food, not from a preformed TOXIN, and the ingested bacteria infect the gut mucosa.
Which serotype usually causes enteritidis?

What else causes it?
typhimurium serotype

Salmonella enteritidis is somewhat invasive and gastroenteritis frequently involves infection of the mesenteric lymph nodes, although it rarely (5%) reaches the blood.
Should antibiotic be given to treat salmonella?
no--it is a self-limited infection; antibiotic treatment only serves to prolong the carrier state and increase the likelihood of secondary cases.

Treatment should center around supportive therapy and maintaining fluid and electrolyte balance.
How many people carry Salmonellae

1 month? 5 months?

after clinical symptoms disappear?

When is someone considered a carrier?

What is the reservoir?
1 month--1/2

5 months--1/20

after 1 year considered a carrier. still secretes the organism.

gall baldder is reservoir in most carriers.
Which species are most likely to be involved in carriers?
S. typhi, S. paratyphi A, and S. paratyphi B.
What genus causes bacillary dysentary? What is another name for this disease?

What is Shigella most closely related to?
E. Coli
What is the natural animal host for shigella?

How is Shigella spread?
There is no natural animal host for Shigella, although it can be experimentally infected into monkeys.

The organisms are harbored by humans and transferred by contaminated food, water and direct fecal-oral spread.
How many organisms are needed to cause infection?
only 10-100

highly virulent in this regard
Are shigella motile? Lactose + or -?
Produce gas?
Which Ags do they have?
Gram negative rods


lactose negative

do NOT produce gas from fermentable carbs.

have LPS O Ags (No H Ag--NON-motile)
What are the 4 species of Shigella?

Which one only has 1 seroligic type?
Shigella dysenteriae, AKA serologic group A

Shigella flexneri, AKA serologic group B

Shigella boydii, AKA serologic group C

Shigella sonnei, AKA serologic group D.

Group D only has 1 serologic type
Which species does NOT ferment mannitol?
Shigella dysenteriae
Which species will slowly ferment lactose?
S. sonnei--thus exception to the rule that enteric pathogens are lactose negative
Which species accounts for 60 to 80% of the shigellosis in the US?

What causes the remaining cases?
S. sonnei 60--80%

S. flexneri causes the rest.
Where would it be common to see shigellosis?
primarly a pediatric disease. commonly seen in an infected family or day care center

LESS COMMON: cruise ships, in time of war, natural disaster, refugee camps, institutions
What is the primary virulence factor of Shigella?

What else?

Shiga toxin
What type of activities does the Shiga toxin possess?

What is the toxin nearly identical to?
enterotoxic, cytotoxic, and neurotoxic activities

and is nearly identical to the verotoxin produced by EHEC strains of E. coli.
How does Shigella invade and spread? What results?
Shigella invades the epithelium of the LARGE bowel

spreads from cell to cell by the formation of ACTIN "COMETS", similar to the mechanism used by Listeria.

leads to the formation of micro-abscesses, and ultimately, ULCERATION of the colonic mucosa
Does Shigella code for Type III protein?

What mechanism does it use to invade the cell?
encodes a Type III secretion system

uses the "trigger"-type mechanism to invade target cells.
Does Shigella have pathogenicity islands?
NO--Instead of a pathogenicity island, Shigella contains a large (220 kb) VIRULENCE PLASMID which carries the genes for these virulence factors.
What are the clinical signs of Shigella infection?
fever and scant bloody diarrhea with mucus and pus

in the early stages of disease (when the small intestine is infected) a voluminous watery diarrhea is seen in many patients.
Does shigella infection invade the mucosa and reach the mesentaric nodes?
Unlike Salmonella, Shigella does NOT invade beyond the mucosa to reach the lamina propria and the mesenteric lymph nodes and does not lead to bacteremia.
What does Shigella treatment involve? How long does infection last?
Symptoms generally subside without treatment in about one week, although patients may continue to excrete organisms for an additional week.

Treatment with antibiotics shortens the duration of symptoms and shedding, although antibiotic-resistant strains are common.

Treatment also involves replacement of fluid and electrolytes.
When is someone conisdered a carrier of shigella?
Only rarely does a chronic carrier state occur.