Chapter 9: The Enterics Flashcards Preview

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Flashcards in Chapter 9: The Enterics Deck (58):
1

Enterics

Gram-negative bacteria that are part of the normal intestinal flora or cause GI disease

2

What Enterics are able to ferment lactose?

E. coli and most of the enterobacteriaceae

Salmonella, Shigella and Pseudomonas aeruginosa do NOT

3

What are the important biochemical properties of the enterics?

Ability to ferment lactose
Production of H2S: hydrolyze urea, liquefy gelatin, decarboxylate specific aa

4

EMB agar

methylene blue inhibits gram-positive bacteria, and colonies of lactose fermenters become deep purple to black in the medium

5

What color does E coli take on on an EMB agar?

Metallic green sheen

6

MacConkey agar

Bile salts in the medium inhibit gram-positive bacteria, and lactose fermenters develop a pink-purple coloration

7

How are enterics transmitted?

by the fecal-oral route

8

Coliform means...

normal inhabitant of the intestinal tract

9

How do you test for E. coli in a sample (water)?

Presumptive test: test tubes that contain lactose, gas is produced
Confirmed test: EMB agar plates @ 45.5C
Completed Test: broth with lactose again, gas forms
= E coli

10

What are the 3 major surface antigens of enterics?

O antigen: most external coomponenet of LPS of gram -
K: capsule that covers O antigen
H: makes up subunits of bacterial flagella

11

Clinical manifestations of enterics with no intestinal epithelial cell invasion

Bacteria bind to cell but do not enter
Diarrhea caused by release of exotoxins
Electrolyte and fluid loss
Water diarrhea WITHOUT systemic symptoms
Enterotoxigenic E. coli and cholera

12

Clinical manifestations of enterics with invasion of intestinal epithelial cells

Invasion into cells
Toxins released that destroy the cells
Systemic immune response with local WBC infiltration as well as fever
Red blood cell leakage into the stool
Enteroinvasive E coli, Shigella, and Salmonella enteritidis

13

Clinical manifestations of enterics with invasion of the LNs and bloodstream

Abdominal pain and diarrhea containing WBC and RBC
Deeper invasion
Systemic symptoms of fever, headache and increase WBC count
Mesenteric LN enlargement, bacteremia and sepsis

Salmonella typhi, Yersinia enterocolitica, and campylobacter jejuni

14

What causes nonpathogenic E. coli to -->disease?

virulence factors acquired by conjugation, lysogenic conversion, and transposons

15

What are the virulence factors of E. coli?

Mucosal interaction: pili, invade
Exotoin production: LT and ST, Shiga-like toxin
Endotoxin: Lipid A portion of LPS
Iron-binding siderophore: obtains iron from human transferring or lactoferrin

16

What are the diseases caused by E. coli in the presence of virulence factors ?

Diarrhea
UTI
Neonatal meningitis
Gram-negative sepsis, occuring commonly in debilitated hospitalized pts

17

What is Montezuma's revenge?

Traveler's diarrhea caused by E.coli

18

ETEC

Enterotoxigenic E. coli
Causes traveler's diarrhea
Pili, LT, ST
Rice water diarrhea

19

How does LT and ST cause diarrhea?

Inhibit reabsorption of Na and Cl and stimulate the secretion of Cl and HCO3 into the intestinal lumen

20

EHEC

Enterohemorrhagic E. coli
Pili, Shiga-like toxin/verotoxin
Bloody diarrhea, abdominal cramps
= hemorrhagic colitis

21

What does Shiga-like toxin cause?

Inhibit protein synthesis by inhibiting the 60S ribosome, intestinal epithelial cell death

22

HUS- Hemolytic uremic syndrome

Anemia, thrombocytopenia (decrease in platelets), and renal failure
Associated with infection by a strain of EHEC: E. coli 0157:H7
Hamburger meat fast food

23

EIEC

Enteroinvasive E. coli
Invade epithelial cells
Produce small amounts of Shiga-like toxin
Fever
WBCs invade intestinal wall
Diarrhea bloody with WBCs
Like Shigellosis

24

How does E.coli cause UTI?

Acquisition of pili virulence factor, travels up the urethra and infect the bladder (cystitis) or further to kidney (pyelonephritis)

25

What is the most common cause of UTI? Who does it usually occur in? What are the symptoms?

E.coli
Women and hospitalized pts with catheters
Buring on urination *dysuria), pee frequently, feeling fullness over bladder

26

What is the most common cause of neonatal meningitis ?

Group B strep
E.coli is second

27

What is the most common cause of gram-negative sepsis?

E. coli
Usually occurs in debilitated hospitalized pts
Lipid A of LPS

28

Klebsiella penumoniae

O antigen but no H antigen (non-motile)
Hospitals
Causes UTI, Sepsis (#2 cause)
Penumonia: bloody sputum looks like currant jelly, violent, destroys lung tissue

29

Proteus mirabilis

Very motile
Break down urea
Use this (OX-19, 2, K) as a cross reaction to check if pts have had Rickettsia
Common cause of UTI and HA-infections

30

Enterobacter

Highly motile, gram- rod
Normal flora
HA-infection

31

Most common cause of Gram - sepsis ?

E coli

32

Serratia

Bright red pigment production
Cause UTI, wound infections, or pneumonia

33

Shigella

Four species
Non-motile: no flagella
Does not ferment lactose
Does not produce H2S
Always a pathogen, never normal flora
Shiga toxin
Similar to EIEC

34

Usual targets for Shigella ?

Preschool age children
Nursing homes
Fecal-oral route

35

Salmonella

Non-lactose fermenter
Motile
And produces H2S
Vi antigen: surround O antigen and protects from Abs
Lives in GI tracts of animals and infects humans by contaminated food or water with animal feces

36

What Salmonella species is not zootonic?

Salmonella typhi: only carried by humans

37

Typhoid Fever

Salmonella typhi: invades LNs and seeds in multiple organ systems
Also called enteric fever
Facultative intracellular parasite
Headache, fever, abdominal pain, (appendicitis feel)
Spleen enlargement, diarrhea and rose spots on abdomen possible

38

Chronic carriers of Salmonella typhi

Harbor Salmonella thypi in gallbladders
Excreting bacteria constantly
Not actively infected, no symptoms

39

What type of pts are more susceptible to Salmonella infections?

Asplenic or sickle-cell anemic pts - have difficulty clearing encapsulted bacteria
Particularly prone to Salmonella osteomyelitis

40

What salmonella causes sepsis?

Salmonella choleraesuis
Does not involve GI tract
In bloodstream: infects lungs, brain or bone

41

What is the most common type of Salmonella infection?

Diarrhea: nausea, abdominal pain, diarrhea watery mostly (sometimes mucous and blood) Fever 50%
Only lasts for a week or less

42

Yersinia enterocolitica

Motile gram-negative rod
Another cause of acute gastroenteritis
Animals are a major source: fecal-oral route
Fever, diarrhea, abdominal pain (appendicitis like), mucosal ulceration
Survive cold

43

How does Yersinia enterocolitica cause disease?

Invasion: binds to intestinal wall, systemic invasion into region LNs and bloodstream
Mesenteric LNs swell
Sepsis can develop
Enterotoxin: ST-like (diarrhea),

44

Vibrio cholera

curved gram-negative rod with a single polar flagellum
Transmission: fecal-oral route
No epithelial cell invasion
Releases cholragen

45

What does Choleragen do/

5 B subunits bind to surface, allowing A subunit to enter
A subunit activates G-protein, Stimulates Adenylate cyclase, increase cAMP
Active secretion of Na and Cl
Inhibition of Na and Cl reabsorption
Fluid loss

46

What is the leading caue of diarrhea in Japan?

Vibrio parahaemolyticus: marine bacterium in sushi

47

Campylobacter jejuni

Gram-negative rod
zootonic
Fecal-oral route via water is most common transmission
Children more commonly affected worldwide

48

What are the most common causes of diarrhea in the world?

Campylobacter jejuni, ETEC, and Rotavirus

49

What are the symptoms of Campylobacter jejuni infection?

Prodrome of fever and headache
Abdominal cramps, bloody loose diarrhea
Invades lining of small intestine, spreads systemically

50

Helicobacter pylori causes what?

Most common cause of duodenal ulcers and chronic gastritis
(Aspirin ranks second)
Second leading cause of gastric ulcers

51

What is 99% of the intestinal flora made up of?

Obligate anaerobic gram - rods from family Bacteroidaceae
(mouth and vagina are also homes)

52

What is a bacteria that is one of the few gram - that does NOT contain lipid A in its outer cell membrane
Part of Bacteroidaceae

Bacteroids fragilis

53

When does Bacteroides fragilis cause complications?

Low virulence
But when the intestine ruptures due to trauma or infection, ischemia etc. the bacteria will go into peritoneal cavity and form abscesses
Fever and systemic spread may accompany

54

Abscess formation by Bacteroides fragilis is seen in what type of pts?

Obstetric and gynecologic pts
Pts with septic abortion, pelvic inflammatory disease, or IUD

55

Bacteroides melaninogenicus

produces black pigment when grown on blood agar
Lives in mouth, vagina, and intestine
Necrotizing anaerobic pneumonias caused by aspiration of sputum from mouth
Periodontal disease

56

Fusobacterium

Causes peridontal disease and aspiration penumonias
Abdominal, pelvic abscess and otitis media

57

Peptostreptococcus

Gram + anaerobes that live in mouth, vagina and intestine
Streptococcus viridans group

58

Peptococcus

Cluster of cocci that are gram + anaerobes that live in mouth, vagina and intestine
Streptococcus viridans group