Flashcards in Chapter 9: The Enterics Deck (58):
Gram-negative bacteria that are part of the normal intestinal flora or cause GI disease
What Enterics are able to ferment lactose?
E. coli and most of the enterobacteriaceae
Salmonella, Shigella and Pseudomonas aeruginosa do NOT
What are the important biochemical properties of the enterics?
Ability to ferment lactose
Production of H2S: hydrolyze urea, liquefy gelatin, decarboxylate specific aa
methylene blue inhibits gram-positive bacteria, and colonies of lactose fermenters become deep purple to black in the medium
What color does E coli take on on an EMB agar?
Metallic green sheen
Bile salts in the medium inhibit gram-positive bacteria, and lactose fermenters develop a pink-purple coloration
How are enterics transmitted?
by the fecal-oral route
normal inhabitant of the intestinal tract
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
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
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
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
Clinical manifestations of enterics with invasion of the LNs and bloodstream
Abdominal pain and diarrhea containing WBC and RBC
Systemic symptoms of fever, headache and increase WBC count
Mesenteric LN enlargement, bacteremia and sepsis
Salmonella typhi, Yersinia enterocolitica, and campylobacter jejuni
What causes nonpathogenic E. coli to -->disease?
virulence factors acquired by conjugation, lysogenic conversion, and transposons
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
What are the diseases caused by E. coli in the presence of virulence factors ?
Gram-negative sepsis, occuring commonly in debilitated hospitalized pts
What is Montezuma's revenge?
Traveler's diarrhea caused by E.coli
Enterotoxigenic E. coli
Causes traveler's diarrhea
Pili, LT, ST
Rice water diarrhea
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
Enterohemorrhagic E. coli
Pili, Shiga-like toxin/verotoxin
Bloody diarrhea, abdominal cramps
= hemorrhagic colitis
What does Shiga-like toxin cause?
Inhibit protein synthesis by inhibiting the 60S ribosome, intestinal epithelial cell death
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
Enteroinvasive E. coli
Invade epithelial cells
Produce small amounts of Shiga-like toxin
WBCs invade intestinal wall
Diarrhea bloody with WBCs
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)
What is the most common cause of UTI? Who does it usually occur in? What are the symptoms?
Women and hospitalized pts with catheters
Buring on urination *dysuria), pee frequently, feeling fullness over bladder
What is the most common cause of neonatal meningitis ?
Group B strep
E.coli is second
What is the most common cause of gram-negative sepsis?
Usually occurs in debilitated hospitalized pts
Lipid A of LPS
O antigen but no H antigen (non-motile)
Causes UTI, Sepsis (#2 cause)
Penumonia: bloody sputum looks like currant jelly, violent, destroys lung tissue
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
Highly motile, gram- rod
Most common cause of Gram - sepsis ?
Bright red pigment production
Cause UTI, wound infections, or pneumonia
Non-motile: no flagella
Does not ferment lactose
Does not produce H2S
Always a pathogen, never normal flora
Similar to EIEC
Usual targets for Shigella ?
Preschool age children
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
What Salmonella species is not zootonic?
Salmonella typhi: only carried by humans
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
Chronic carriers of Salmonella typhi
Harbor Salmonella thypi in gallbladders
Excreting bacteria constantly
Not actively infected, no symptoms
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
What salmonella causes sepsis?
Does not involve GI tract
In bloodstream: infects lungs, brain or bone
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
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
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),
curved gram-negative rod with a single polar flagellum
Transmission: fecal-oral route
No epithelial cell invasion
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
What is the leading caue of diarrhea in Japan?
Vibrio parahaemolyticus: marine bacterium in sushi
Fecal-oral route via water is most common transmission
Children more commonly affected worldwide
What are the most common causes of diarrhea in the world?
Campylobacter jejuni, ETEC, and Rotavirus
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
Helicobacter pylori causes what?
Most common cause of duodenal ulcers and chronic gastritis
(Aspirin ranks second)
Second leading cause of gastric ulcers
What is 99% of the intestinal flora made up of?
Obligate anaerobic gram - rods from family Bacteroidaceae
(mouth and vagina are also homes)
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
When does Bacteroides fragilis cause complications?
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
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
produces black pigment when grown on blood agar
Lives in mouth, vagina, and intestine
Necrotizing anaerobic pneumonias caused by aspiration of sputum from mouth
Causes peridontal disease and aspiration penumonias
Abdominal, pelvic abscess and otitis media
Gram + anaerobes that live in mouth, vagina and intestine
Streptococcus viridans group