Lec12 EColi Flashcards
What is the micro of enterobacteriacea? shape, gram, lac? where are they normally found?
- gram negative rods
- lactose fermenting
- found in GI of humans/animals or in environment
What infections are caused E. coli
- UTI
- diarrhea
- neonatal sepsi
- intra-abdominal infections
- nosocomial infections
What diseases associated with klebsiella?
pneumonia, UTI, nosocomial [hospital acquired] infections
What diseases associated with salmonella
diarrhea, typhoid fever
What disease associated with shingella?
diarrhea
What diseases associated with yersinia?
diarrhea, the plague
What type of disease associated with enterobacter, serratia, and citrobacter?
nosocomial [aka hospital acquired] infections
What disease associated with proteus?
UTI
What is pathogenesis of E coli infection?
- E coli is part of normal GI flora –> makes it hard to diagnose diarrheal disease cause by E coli
- infection causes by virulence factors [diarrhea, uti] or disruption of host barriers [intraabdominal infection following intestinal perforation
What is MacConkey agar?
- grows gram negative bacteria
- differentiated between them based on who is a lactose fermenter
- lactose fermenting bacteria turn red/pink
What are the 3 important surface antigens of E coli used to serotype strains?
O antigen = LPS [lipopolisaccharide]
H antigen = flagella
K antigen = capsule
What are clinical signs of a lower UTI [cystitis urethritis]?
- dysuria, frequency of urination
What are clinical signs of an upper UTI [pyelonephritis]
- fever, flank pain, dysuria, frequency of urination, costo-vertebral angle tenderness
What is the most common cause of UTI? what are the other causes?
E coli most common by far then - coagulase negative staph - proteus mirabilis - other gram negatives - other gram positives
What is function of P-Pilli in E Coli?
- type of pili that is present in some uropathogenic strains
- allow e coli to adhere to urinary epithelium
- specific for urinary tract epithelium and nowhere else
What are type 1 pili?
the common type of pili
How do you treat lower UTI?
- oral medication
- fluoroquinolone [ex cipro]
- or 3rd gen cephalosporin [ex ceftriaxone]
- or trimethoprim-sulfamethoxazole
How do you treat upper UTI?
- by IV drug
- fluoroquinolone [ex cipro]
- or 3rd gen cephalosporin [ex ceftriaxone]
What is enterotoxigenic E Coli [ETEC]? How transmitted, what diseases?
- transmitted through food/water contaminated by infected individual
- travelers diarrhea
- watery diarrhea in infants in developing country
What is the pathogenesis of ETEC [enterotoxigenic]?
- Adheres to intestinal epithelial cell via CF pili
- does not invade cell
- releases heat labile and heat stable exotoxins that go into cell and cause diarrhea
What is treatment for ETEC?
supportive treatment
What is heat labile toxin [LT]?
- similar to cholera toxin
- type of AB exotoxin
- stimulates adenylate cyclase and leads to secretion of Na, K, and water
What is heat stable toxin [ST]?
- exotoxin
- stimulates guanylate cyclase and leads to secretion Cl, HCO3, and water
How does commensal E Coli bcome ETEC?
- gains single pENT plasmid
- LT, ST, and CF genes all contained on single plasmid
What is enteropathogenic E Coli [EPEC]? How transmitted, what diseases?
- produces water diarrhea in infants in developing world
- transmitted by fecal-oral route from carrier to infant
What is the characteristic finding of enteropathogenic E Coli?
attachment/effacement [A/E] lesion
what is pathogenesis of EPEC infection?
- bundle-forming pili mediate attachment
- assemble type III secretion system injects proteins in epithelial cell that act as virulence factors and trigger rearrangement of cytoskeleton leads to loss of normal structure
How does normal commensual E Coli become EPEC?
introduction of virulence genes on a pathogenicity island [PAI]
What are enteroaggregative E Coli? Disease?
- cause prolonged watery diarrhea [weeks] in children in developing world
- organisms pile up on top of cell and form thick mucous-bacterial biofilm
- stacked brick appearance
What is a pathogenicity island?
segment of DNA with multiple virulence factors back to back
What disease does enterohemorrhagic E Coli [EHEC or STEC] cause? symptoms?
- bloody diarrhea without fever
- hemolytic-uremic syndrome [HUS] triad of:
- —— microangiopathic anemia [RBCs destroyed in small vessels]
- ——- thrombocytopenia [absence of platelets]
- ——- renal failure
What is the triad of hemolytic uremic syndrome
- —— microangiopathic anemia [RBCs destroyed in small vessels]
- ——- thrombocytopenia [absence of platelets]
- ——- renal failure
How is EHEC [enterohemorrhagic] acquired?
- consumption of not fully cooked beef
- direct contact with animals
- food contaminated by animal feces
What is pathogenesis of EHEC? What is its primary exotoxin?
- EColi 0157:H7 and others
- releases Shigatoxin [Stx]
- Shigatoxin is AB exotoxin that interferes with protein synthesis at level of ribosome
- causes injury to enterocytes –> get blood diarrhea
- if gets into blood stream causes injury to renal endothelium –> get renal failure, thrombocytopenia, enemia
What is treatment of EHEC?
supportive treatment
antibiotics don’t help
How is EHEC diagnosed?
- test for shigatoxin in stool
- sorbitol agar: 0157:H7 will show up as clear as opposed to normal E coli will have pink [but this will not distinguish other EHEC strains]
How does commensal E coli become EHEC?
gets shigatoxin gene from a phage
What is enteroinvasic E coli [EIEC]? What diseases? Who gets it? What is site of infection?
- causes dysentary: small volume bloody diarrhea, crampy abdominal pain, fever
- stool smear will have many WBCs
- seen in children in developing world
- site of infection is colon [other E Colis mostly small intestine]
What is pathogenesis of EIEC?
- e coli gets into enterocyte
- spreads from one cell to the next causes cell death
- little or no systemic disemination
When do you get intra-abdominal infection? what is treatment?
- occurs following rupture of intestine [appendicitis, diverticulitis, trauma]
- requires surgical and medical management with broad spectrum antibiotics
What are signs of neonatal sepsis and meningitis? what are top bacterial etiologies? treatment?
- fever, hypothermia, abnormal vital signs often only clue
- top causes: E Coli [particularly those wtih K1 capsular antigen], Group B streptococcus, Listeria
- treat: cefotaxamine + ampicillin [for listeria]
What are signs of nosocomial E coli infection? What are two types of resistant enzymes they can contain?
can cause:
- bacteremia
- urinary tract infections
- ventilator associated pneumonia
- can be very resistant
- – extended spectrum betalacamases [ESBLs] –> inactivate 1st-3rd gen cephalosporins
- klebsiella pneumoniae carbapenamase [KPCs]
