Glossary of Chapter 9: The Enterics

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What are the 4 genus' of enterics
enterobacteriaceae, vibrionaceae, pseudomonadaceae, bacteroidaceae
What are 2 important media to ID enterics?
1. EMB agar: inhibits gram + bacteria and lactose fermenters turn deep purple to black; 2. MacConkey agar: bile salts in the medium inhibit gram + bacteria and the lactose fermenters turn pink/purple
What biochemical properties can you measure in the lab?
1. lactose fermentation; 2. production of H2S
How would you test for E. coli in Uruguayan river?
1. lactose with inverted vial; 2. streak EMB with the water to look for green metallic sheen; 3. put metallic green colonies back in the broth
What are the 3 main surface antigens found in enterics?
K antigen: capsule that covers O antigen; O antigen: outer-most LPS component; H antigen: makes up subunits of bacterial flagella so only motile bacteria have it
What are the 2 types of disease caused by enterics?
1. diarrhea with or without systemic infection; 2. UTI, pneumonia, bacteremia, sepsis in weak hospitalized patients
What are the 3 levels of diarrhea?
1. no cell invasion: binding to epithelial cells, exotoxin release, no systemic symptoms; 2. invasion of epithelial cells: binding, invasion, toxins kill cells, WBC+, leukocytes and RBCs in stool; 3. invasion of lymph nodes and blood stream: abdominal pain, diarrhea with WBC, RBC
What bugs cause diarrhea without cellular invasion?
E. coli and vibrio cholera
Which bugs invade intestinal epithelial cells?
E. coli, Shigella, Salmonella enteriditis
Which bugs cause diarrhea and invade lymph nodes + blood stream?
salmonella typhi, yersinia enterocolitica, campylobacter jejuni
What 6 bugs are known as the nosocomial gram negatives?
E. coli, Klebsiella pneumoniae, Proteus mirabilis, enterobacter, serratia, Pseudomonas aeruginosa
What are 4 possible E. coli virulence factors?
1. mucosal interaction; 2. exotoxin production; 3. endotoxin production; 4. Fe-binding siderophore
How does E. coli become virulent?
DNA swapping
What 4 diseases does E. coli + virulence cause?
1. diarrhea; 2. UTI; 3. neonatal meningitis; 4. gram - sepsis (esp. in hospitalized pts.)
What causes travelers' diarrhea or Montezuma's revenge?
E. coli
What do the heat Labile Toxin (LT) and heat Stabile Toxin (ST) do?
inhibit Na+ and Cl- absorption, stimulate Cl- and HCO3- secretion
What are the 3 types of E. coli diarrhea?
1. enterotoxigenic E. coli (ETEC): binds, LT, ST, "rice water" diarrhea; 2. enterohemorrhagic E. coli (EHEC): Shiga-like toxin (verotoxin), epithelial cell death, bloody, cramps, hemorrhagic colitis; 3. enteroinvasive E. coli (EIEC): like shigella, invade epithelial cells, fever, bloody stool
What does verotoxin do?
inhibits 60S ribosome, killing epithelial cells
Which 3 bugs share virulence through DNA swapping?
vibrio, E. coli, shigella
How does E. coli cause UTI?
pili virulence factor lets bug travel up urethra leading to cystitis (bladder infection) and pyelonephritis (kidney infection) causing dysuria (painful pee) and frequency
What is the most common cause of UTI's? Who gets them?
E. coli; women & hospitalized pts. with catheters in urethra
What are the top 2 causes of neonatal meningitis?
1. group B strep; 2. E. coli
What's the most common cause of gram - sepsis?
E. coli in weak hospitalized pts. caused by the lipid A component of LPS
Can E. coli cause nosocomial pneumonia?
What 3 things does Klebsiella pneumonia cause?
1. gram - sepsis (2nd most common); 2. UTI in pts. with Foley catheter; 3. pneumonia in alcoholics and hospitalized pts. (red currant jelly sputum)
What is the virulence factor in Klebsiella?
the O antigen
What biochemical reaction is proteus mirabilis known for? Is it motile?
splits urea into NH3 and CO2; YES!
What disease does proteus cause?
UTI and other nosocomial infections
What bug causes hemolytic uremic syndrome (HUS)? What are some signs?
E. coli 0157:H7; anemia, thrombocytopenia, renal failure
What is enterobacter?
highly motile gram - rod; occasional cause of nosocomial infections
What is serratia known for?
bright rred pigment; causes UTIs, wound infection, pneumonia
What are the key identifiers of E. coli, shigella, and salmonella (ie. labs)?
1. E. coli: ferments lactose; 2. Shigella: "...don't do SHIt" non-motile, no H2S production, no lactose fermentation; 3. Salmonella: motile (like the fishy), H2S production, no fermentation (can't underwater)
How does Shigella cause disease?
invades intestinal epithelial cells and releases the SHIGA TOXIN (inhibits 60S ribosome); the damaged colon can then no longer reabsorb fluids and electrolytes
What is Salmonella's vi antigen?
the polysaccharide capsule around the O antigen; vi = "virulence" factor
Where does Salmonella live?
GI tracts of animals; contamination through animal feces
Which is part of the normal human GI flora, salmonella or shigella?
neither, both are pathogenic in humans!
What are the 4 disease states that salmonella causes in humans?
1. typhoid fever; 2. carrier state; 3. sepsis; 4. gastroenteritis
What is typhoid fever?
aka enteric fever; caused by salmonella typhi, a facultative intracellular parasite; treated with ciprofloxacin or ceftriaxone
What is the salmonella carrier state?
after recovery from typhoid fever, salmonella typhi lives in the gall bladder
What salmonella species causes sepsis?
salmonella choleraesuis; does NOT involve GI tract
Which salmonella disease are sickle cell pts. more likely to get?
salmonella osteomyelitis; no spleen to phagocytose the vi encapsulated salmonella
Which species of salmonella causes diarrhea only?
salmonella enteritidis causes gastroenteritis
How is salmonella diarrhea treated?
fluid and electrolyte replacement since antibiotics don't shorten the course of the disease
What is the name of the non-enteric bug which is a gram - rod and causes acute gastroenteritis?
Yersinia enterocolitica
In acute enterocolitis caused by Yersinia enterocolitica, where is the pain most severe?
the terminal ileum, located in the right lower quadrant
Describe the 2-fold pathogenesis of Yersinia enterocolitica.
1. bind to intestinal wall and invade regional lymph nodes; 2. secrete heat stabile enterotoxin
What causes cholera? How does it present?
Vibrio cholera, a curved gram - rod with a single polar flagellum; presents with abrupt onset of watery diarrhea (looks like rice water), loss of fluid of 1 liter/hour
How does the cholera toxin, choleragen, work?
B subunit binds to intestinal epithelial cell, A subunit enters the cell, activating the G-protein. AC is stimulated, + cAMP production, + Na/Cl secretion, - Na/Cl reabsorption
What is the leading cause of diarrhea in Japan due to the sushi?
Vibrio parahaemolyticus
What are the 3 most common causes of diarrhea in the world?
Campylobacter jejuni, ETEC, and the Rotavirus
What can Campylobacter jejuni cause?
fever, headache, abdominal cramps and bloody, loose diarrhea
How does Campylobacter jejuni cause symptoms and how does it spread?
spread via the oral-fecal route, the reservoirs are in wild and domestic animals and poultry; invades lining of the small intestine and spreads systematically, secretes LT toxin and an unknown cytotoxin that destroys mucosal cells
What is the most common cause of duodenal ulcers and chronic gastritis; and the second leading cause of gastric (stomach) ulcers?
Helicobacter pylori
Why is the Pseudomonas aeruginosa so important to understand?
1. colonizes and infects sick, immunocompromised hospitalized patients; 2. it's resistant to almost every antibiotic
What are some key characteristics of Pseudomonas aeruginosa?
obligate aerobe, non-lactose fermenter, gram-negative rod, produces green fluorescent pigment (fluorescein) and a blue pigment (pyocyanin) which gives colonies and infected wound dressings a green-blue color, smells like grapes
What is the main toxic agent of Pseudomonas aeruginosa?
exotoxin A, which stops protein synthesis
What are some important Pseudomonas infections to know?
1. pneumonia (CF patients, immunocompromised patients); 2. osteomyelitis (diabetic patients' foot ulcers, IV drug users can get it in vertebrae or clavicle, kids can get it following puncture wound); 3. burn wound infections; 4. sepsis; 5. UTI, pyelonephritis (debilitated patients in nursing homes - due to Foley catheters); 6. right heart endocarditis in IV drug users; 7. malignant external otitis (esp. in elderly diabetic patients); 8. corneal infections (contact lens wearers)
What is Pseudomonas cepacia?
rapidly becoming an important pathogen, affecting hospitalized patients ina similar manner
99% of the flora in our intestinal tract is colonized by what bug?
Bacteroidaceae, an obligate anaerobic gram - rod; the mouth and vagina are also home to these bugs
Which bug is the important one to consider following surgery and wounds in the intestine?
Bacteroides fragilis forms abscesses in the peritoneal cavity; prophylactic antibiotics are necessary: clindamycin, metronidazole, chloramphenicol
What bug is involved in necrotizing anaerobic pneumonias caused by aspirating lots of sputum from the mouth (also causes periodontal disease)?
Bacteroides melaninogenicus; Fusobacterium does the same thing, but also can cause abdominal and pelvic abscesses and otitis media
What gram + anaerobes are part of the normal flora of the mouth, vagina, and intestine?
Peptostreptococcus and Peptococcus

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