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62 Cards in this Set
- Front
- Back
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What are the 4 genus' of enterics
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enterobacteriaceae, vibrionaceae, pseudomonadaceae, bacteroidaceae
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What are 2 important media to ID enterics?
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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
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What biochemical properties can you measure in the lab?
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1. lactose fermentation; 2. production of H2S
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How would you test for E. coli in Uruguayan river?
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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
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What are the 3 main surface antigens found in enterics?
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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
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What are the 2 types of disease caused by enterics?
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1. diarrhea with or without systemic infection; 2. UTI, pneumonia, bacteremia, sepsis in weak hospitalized patients
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What are the 3 levels of diarrhea?
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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
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What bugs cause diarrhea without cellular invasion?
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E. coli and vibrio cholera
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Which bugs invade intestinal epithelial cells?
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E. coli, Shigella, Salmonella enteriditis
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Which bugs cause diarrhea and invade lymph nodes + blood stream?
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salmonella typhi, yersinia enterocolitica, campylobacter jejuni
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What 6 bugs are known as the nosocomial gram negatives?
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E. coli, Klebsiella pneumoniae, Proteus mirabilis, enterobacter, serratia, Pseudomonas aeruginosa
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What are 4 possible E. coli virulence factors?
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1. mucosal interaction; 2. exotoxin production; 3. endotoxin production; 4. Fe-binding siderophore
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How does E. coli become virulent?
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DNA swapping
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What 4 diseases does E. coli + virulence cause?
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1. diarrhea; 2. UTI; 3. neonatal meningitis; 4. gram - sepsis (esp. in hospitalized pts.)
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What causes travelers' diarrhea or Montezuma's revenge?
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E. coli
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What do the heat Labile Toxin (LT) and heat Stabile Toxin (ST) do?
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inhibit Na+ and Cl- absorption, stimulate Cl- and HCO3- secretion
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What are the 3 types of E. coli diarrhea?
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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
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What does verotoxin do?
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inhibits 60S ribosome, killing epithelial cells
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Which 3 bugs share virulence through DNA swapping?
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vibrio, E. coli, shigella
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How does E. coli cause UTI?
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pili virulence factor lets bug travel up urethra leading to cystitis (bladder infection) and pyelonephritis (kidney infection) causing dysuria (painful pee) and frequency
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What is the most common cause of UTI's? Who gets them?
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E. coli; women & hospitalized pts. with catheters in urethra
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What are the top 2 causes of neonatal meningitis?
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1. group B strep; 2. E. coli
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What's the most common cause of gram - sepsis?
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E. coli in weak hospitalized pts. caused by the lipid A component of LPS
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Can E. coli cause nosocomial pneumonia?
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YES!
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What 3 things does Klebsiella pneumonia cause?
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1. gram - sepsis (2nd most common); 2. UTI in pts. with Foley catheter; 3. pneumonia in alcoholics and hospitalized pts. (red currant jelly sputum)
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What is the virulence factor in Klebsiella?
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the O antigen
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What biochemical reaction is proteus mirabilis known for? Is it motile?
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splits urea into NH3 and CO2; YES!
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What disease does proteus cause?
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UTI and other nosocomial infections
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What bug causes hemolytic uremic syndrome (HUS)? What are some signs?
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E. coli 0157:H7; anemia, thrombocytopenia, renal failure
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What is enterobacter?
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highly motile gram - rod; occasional cause of nosocomial infections
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What is serratia known for?
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bright rred pigment; causes UTIs, wound infection, pneumonia
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What are the key identifiers of E. coli, shigella, and salmonella (ie. labs)?
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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)
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How does Shigella cause disease?
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invades intestinal epithelial cells and releases the SHIGA TOXIN (inhibits 60S ribosome); the damaged colon can then no longer reabsorb fluids and electrolytes
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What is Salmonella's vi antigen?
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the polysaccharide capsule around the O antigen; vi = "virulence" factor
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Where does Salmonella live?
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GI tracts of animals; contamination through animal feces
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Which is part of the normal human GI flora, salmonella or shigella?
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neither, both are pathogenic in humans!
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What are the 4 disease states that salmonella causes in humans?
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1. typhoid fever; 2. carrier state; 3. sepsis; 4. gastroenteritis
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What is typhoid fever?
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aka enteric fever; caused by salmonella typhi, a facultative intracellular parasite; treated with ciprofloxacin or ceftriaxone
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What is the salmonella carrier state?
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after recovery from typhoid fever, salmonella typhi lives in the gall bladder
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What salmonella species causes sepsis?
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salmonella choleraesuis; does NOT involve GI tract
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Which salmonella disease are sickle cell pts. more likely to get?
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salmonella osteomyelitis; no spleen to phagocytose the vi encapsulated salmonella
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Which species of salmonella causes diarrhea only?
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salmonella enteritidis causes gastroenteritis
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How is salmonella diarrhea treated?
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fluid and electrolyte replacement since antibiotics don't shorten the course of the disease
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What is the name of the non-enteric bug which is a gram - rod and causes acute gastroenteritis?
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Yersinia enterocolitica
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In acute enterocolitis caused by Yersinia enterocolitica, where is the pain most severe?
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the terminal ileum, located in the right lower quadrant
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Describe the 2-fold pathogenesis of Yersinia enterocolitica.
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1. bind to intestinal wall and invade regional lymph nodes; 2. secrete heat stabile enterotoxin
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What causes cholera? How does it present?
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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
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How does the cholera toxin, choleragen, work?
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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
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What is the leading cause of diarrhea in Japan due to the sushi?
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Vibrio parahaemolyticus
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What are the 3 most common causes of diarrhea in the world?
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Campylobacter jejuni, ETEC, and the Rotavirus
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What can Campylobacter jejuni cause?
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fever, headache, abdominal cramps and bloody, loose diarrhea
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How does Campylobacter jejuni cause symptoms and how does it spread?
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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
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What is the most common cause of duodenal ulcers and chronic gastritis; and the second leading cause of gastric (stomach) ulcers?
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Helicobacter pylori
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Why is the Pseudomonas aeruginosa so important to understand?
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1. colonizes and infects sick, immunocompromised hospitalized patients; 2. it's resistant to almost every antibiotic
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What are some key characteristics of Pseudomonas aeruginosa?
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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
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What is the main toxic agent of Pseudomonas aeruginosa?
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exotoxin A, which stops protein synthesis
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What are some important Pseudomonas infections to know?
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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)
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What is Pseudomonas cepacia?
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rapidly becoming an important pathogen, affecting hospitalized patients ina similar manner
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99% of the flora in our intestinal tract is colonized by what bug?
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Bacteroidaceae, an obligate anaerobic gram - rod; the mouth and vagina are also home to these bugs
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Which bug is the important one to consider following surgery and wounds in the intestine?
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Bacteroides fragilis forms abscesses in the peritoneal cavity; prophylactic antibiotics are necessary: clindamycin, metronidazole, chloramphenicol
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What bug is involved in necrotizing anaerobic pneumonias caused by aspirating lots of sputum from the mouth (also causes periodontal disease)?
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Bacteroides melaninogenicus; Fusobacterium does the same thing, but also can cause abdominal and pelvic abscesses and otitis media
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What gram + anaerobes are part of the normal flora of the mouth, vagina, and intestine?
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Peptostreptococcus and Peptococcus
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