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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
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

CMMRS (27 decks)

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