Micro: Salmonella And Shigella #13

Front 1

Describe Salmonella based on the following:

members of which family

shape

Gram-pos or neg

oxidase pos or neg

fermentaton status

motility?

Back 1

family Enterobacteriaceae

Gram-negative rods

oxidase negative

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

most are motile

Front 2

What are teh three species of Salmonella?

Which has the most serotypes?

Back 2

: 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)

Front 3

What is another way of classifying Salmonellae?

Back 3

based on DNA homologies--all under Salmonella enterica (or Salmonella chleraesuis)--7 subgroups

Front 4

What is the simplistic classification system of Salmonellae?

Back 4

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.

Front 5

What do Salmonellae produce from glucose?

What is the exception?

Back 5

gas--hydrogen sufide

S. Typhi does not produce gas

Front 6

How many cells of Salmonella is needed for the development of symptomatic disease?

Back 6

Although exposure to Salmonella is frequent, a large inoculum (100 thousand to 100 million cells)

Front 7

What is the most common age for individuals to be diagnosed with Salmonella infections?

Back 7

usually diagnosed in the United States in children under the age of 10.

Front 8

Where does Salmonella grow in the host?

Does Salmonella produce exotoxins? Endotoxins?

Back 8

intracellular pathogen, surviving and growing within epithelial cells and macrophages

No exotoxins, yes endotoxins

Front 9

What are the 3 most important virulence factors of Salmonella involved with?

What symptoms is this especially true for? Unclear?

Back 9

invasiveness

serum resistance

survival within macrophages.

This is especially true for enteric fever and septicemia. In gastroenteritis, the picture is less clear.

Front 10

How does genetic regulation of enterotoxins aid Salmonella in virulence?

Back 10

so that they are not expressed in vitro, but are induced when the bacteria enter macrophages.

Front 11

How do pathogenicity islands affect Salmonella? More specifically, what do SPI 1 and SPI 2 do?

Back 11

These large blocks of VIRULENCE GENES encode such functions as

invasiveness (SPI1)

and survival inside macrophages (SPI2).

Front 12

What type of protein do both SPI 1 and 2 carry? What does this protein do?

Back 12

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.

Front 13

How does invasion of epithelial cells and macrophages by Salmonella occur?

What is the result?

Back 13

"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.

Front 14

What are the 5 virulence factors of Salmonella (2 in addition to the 3 from earlier)?

Back 14

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)

Front 15

What are the 4 forms of Salmonella infection?

Back 15

-Enteric fever

-Septicemia

-Gastroenteritis

-Asymptomatic carriage

Front 16

What types of fever does Enteric fever caused by Salmonella cause?

Back 16

typhoid and paratyphoid fever

Front 17

What causes typhoid fever?

How is typhoid fever characterized?

Back 17

S. typhi

characterized by high fever and abdominal symptoms.

Enteric fevers caused by other Salmonellae are generally milder.

Front 18

What causes paratyphoid fever?

Back 18

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.)

Front 19

Is typhoid fever a diarrheal disease? How is it spread?

Back 19

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.

Front 20

How is typhoid fever diagnosed?

Back 20

systemic infection with organisms present in blood (although not at high titer), and several internal organs.

Front 21

What serves as host to S. typhi and S. paratyphi?

Back 21

humans only

Front 22

Is typoid fever common in the US?

Is the mortality rate high?

What is the MAJOR source of infection?

What does the treatment involve?

Back 22

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

Front 23

How can septicemia be detected?

Back 23

high #'s of bacteria in the blood

Front 24

How do primary and secondary septicemia differ?

Back 24

primary--bacteria in the blood at lower level, consumed by macrophages

secondary--bacteria won't die in the macrophage. Enters bloodstream--higher titer

Front 25

Why ypes of salmonellae are most likely to cause septicemia?

Back 25

All Salmonellae can cause sepsis, although this is most common with S. choleraesuis and S. dublin.

Front 26

What infections can occur secondarily to septicemia?

Back 26

Secondary to the blood infection, localized suppurative infections such as :

endocarditis

osteomyelitis

septic arthritis

can occur in up to 10% of patients.

Front 27

What type of infection is the most common due to Salmonellae?

Back 27

Gastroenteritis (enterocolitis more correct)

Front 28

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?

Back 28

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.

Front 29

Which would be a better term for Salmonella infection: "food poisoning" or "foodborne infection" ? Why?

Back 29

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.

Front 30

Which serotype usually causes enteritidis?

What else causes it?

Back 30

typhimurium serotype

Salmonella enteritidis is somewhat invasive and gastroenteritis frequently involves infection of the mesenteric lymph nodes, although it rarely (5%) reaches the blood.

Front 31

Should antibiotic be given to treat salmonella?

Back 31

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.

Front 32

How many people carry Salmonellae

1 month? 5 months?

after clinical symptoms disappear?

When is someone considered a carrier?

What is the reservoir?

Back 32

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.

Front 33

Which species are most likely to be involved in carriers?

Back 33

S. typhi, S. paratyphi A, and S. paratyphi B.

Front 34

What genus causes bacillary dysentary? What is another name for this disease?

Back 34

Shigella

shigellosis

Front 35

What is Shigella most closely related to?

Back 35

E. Coli

Front 36

What is the natural animal host for shigella?

How is Shigella spread?

Back 36

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.

Front 37

How many organisms are needed to cause infection?

Back 37

only 10-100

highly virulent in this regard

Front 38

Are shigella motile? Lactose + or -?
Produce gas?
Which Ags do they have?

Back 38

Gram negative rods

NON-motile

lactose negative

do NOT produce gas from fermentable carbs.

have LPS O Ags (No H Ag--NON-motile)

Front 39

What are the 4 species of Shigella?

Which one only has 1 seroligic type?

Back 39

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

Front 40

Which species does NOT ferment mannitol?

Back 40

Shigella dysenteriae

Front 41

Which species will slowly ferment lactose?

Back 41

S. sonnei--thus exception to the rule that enteric pathogens are lactose negative

Front 42

Which species accounts for 60 to 80% of the shigellosis in the US?

What causes the remaining cases?

Back 42

S. sonnei 60--80%

S. flexneri causes the rest.

Front 43

Where would it be common to see shigellosis?

Back 43

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

Front 44

What is the primary virulence factor of Shigella?

What else?

Back 44

invasiveness

Shiga toxin

Front 45

What type of activities does the Shiga toxin possess?

What is the toxin nearly identical to?

Back 45

enterotoxic, cytotoxic, and neurotoxic activities

and is nearly identical to the verotoxin produced by EHEC strains of E. coli.

Front 46

How does Shigella invade and spread? What results?

Back 46

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

Front 47

Does Shigella code for Type III protein?

What mechanism does it use to invade the cell?

Back 47

encodes a Type III secretion system

uses the "trigger"-type mechanism to invade target cells.

Front 48

Does Shigella have pathogenicity islands?

Back 48

NO--Instead of a pathogenicity island, Shigella contains a large (220 kb) VIRULENCE PLASMID which carries the genes for these virulence factors.

Front 49

What are the clinical signs of Shigella infection?

Back 49

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.

Front 50

Does shigella infection invade the mucosa and reach the mesentaric nodes?

Back 50

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.

Front 51

What does Shigella treatment involve? How long does infection last?

Back 51

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.

Front 52

When is someone conisdered a carrier of shigella?

Back 52

Only rarely does a chronic carrier state occur.