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CMMRS > Chapter 9: The Enterics > Flashcards

Chapter 9: The Enterics Flashcards

1
Q

Enterics

A

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

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2
Q

What Enterics are able to ferment lactose?

A

E. coli and most of the enterobacteriaceae

Salmonella, Shigella and Pseudomonas aeruginosa do NOT

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3
Q

What are the important biochemical properties of the enterics?

A

Ability to ferment lactose

Production of H2S: hydrolyze urea, liquefy gelatin, decarboxylate specific aa

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4
Q

EMB agar

A

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

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5
Q

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

A

Metallic green sheen

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6
Q

MacConkey agar

A

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

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7
Q

How are enterics transmitted?

A

by the fecal-oral route

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8
Q

Coliform means…

A

normal inhabitant of the intestinal tract

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9
Q

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

A

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

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10
Q

What are the 3 major surface antigens of enterics?

A

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

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11
Q

Clinical manifestations of enterics with no intestinal epithelial cell invasion

A 
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
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12
Q

Clinical manifestations of enterics with invasion of intestinal epithelial cells

A

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

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13
Q

Clinical manifestations of enterics with invasion of the LNs and bloodstream

A

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

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14
Q

What causes nonpathogenic E. coli to –>disease?

A

virulence factors acquired by conjugation, lysogenic conversion, and transposons

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15
Q

What are the virulence factors of E. coli?

A

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

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16
Q

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

A

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

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17
Q

What is Montezuma’s revenge?

A

Traveler’s diarrhea caused by E.coli

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18
Q

ETEC

A

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

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19
Q

How does LT and ST cause diarrhea?

A

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

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20
Q

EHEC

A

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

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21
Q

What does Shiga-like toxin cause?

A

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

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22
Q

HUS- Hemolytic uremic syndrome

A

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

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23
Q

EIEC

A 
Enteroinvasive E. coli 
Invade epithelial cells 
Produce small amounts of Shiga-like toxin 
Fever
WBCs invade intestinal wall 
Diarrhea bloody with WBCs
Like Shigellosis
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24
Q

How does E.coli cause UTI?

A

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

25
Q

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

A

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

26
Q

What is the most common cause of neonatal meningitis ?

A

Group B strep

E.coli is second

27
Q

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

A

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

28
Q

Klebsiella penumoniae

A

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
Q

Proteus mirabilis

A

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
Q

Enterobacter

A

Highly motile, gram- rod
Normal flora
HA-infection

31
Q

Most common cause of Gram - sepsis ?

A

E coli

32
Q

Serratia

A

Bright red pigment production

Cause UTI, wound infections, or pneumonia

33
Q

Shigella

A 
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
Q

Usual targets for Shigella ?

A

Preschool age children
Nursing homes
Fecal-oral route

35
Q

Salmonella

A

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
Q

What Salmonella species is not zootonic?

A

Salmonella typhi: only carried by humans

37
Q

Typhoid Fever

A

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
Q

Chronic carriers of Salmonella typhi

A

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

39
Q

What type of pts are more susceptible to Salmonella infections?

A

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

40
Q

What salmonella causes sepsis?

A

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

41
Q

What is the most common type of Salmonella infection?

A

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

42
Q

Yersinia enterocolitica

A

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
Q

How does Yersinia enterocolitica cause disease?

A

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

44
Q

Vibrio cholera

A

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

45
Q

What does Choleragen do/

A

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
Q

What is the leading caue of diarrhea in Japan?

A

Vibrio parahaemolyticus: marine bacterium in sushi

47
Q

Campylobacter jejuni

A

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

48
Q

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

A

Campylobacter jejuni, ETEC, and Rotavirus

49
Q

What are the symptoms of Campylobacter jejuni infection?

A

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

50
Q

Helicobacter pylori causes what?

A

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

51
Q

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

A

Obligate anaerobic gram - rods from family Bacteroidaceae

mouth and vagina are also homes

52
Q

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

A

Bacteroids fragilis

53
Q

When does Bacteroides fragilis cause complications?

A

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
Q

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

A

Obstetric and gynecologic pts

Pts with septic abortion, pelvic inflammatory disease, or IUD

55
Q

Bacteroides melaninogenicus

A

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
Q

Fusobacterium

A

Causes peridontal disease and aspiration penumonias

Abdominal, pelvic abscess and otitis media

57
Q

Peptostreptococcus

A

Gram + anaerobes that live in mouth, vagina and intestine

Streptococcus viridans group

58
Q

Peptococcus

A

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

CMMRS (27 decks)

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