Term
| What are the different roles of Pili (fibriae) and nonfimbrial adhesins? |
|
Definition
1) Pili are proteinacous structures (Pilin arm linked to Adhesin) facilitate long-range interactions
2) Non-fimbrial adhesins facilitate short between bacterium and host |
|
|
Term
| What is the importance of Bacterial replication? |
|
Definition
1) Increases delivery of soluble virulence factors
2) Survival/persistence
3) Requires pathogen adaptation. |
|
|
Term
| What biological characteristics define Enterobacteriaceae? |
|
Definition
Gram-negative rods that are part of normal GI flora, but that can acquire virulence genes and cause opportunistic infections (i.e. UTIs in hospital)
1) Facultative anaerobes found in sewage
2) Oxidase-negative (no cytochrome oxidase)
3) Growth on simple media with glucose carbon source
4) Growth in presence of bile salts (MacConkey) |
|
|
Term
| How can you differentiate between different Enterobacteriaceae? |
|
Definition
Metabolism
1) Triple Sugar Iron (TSI) tube
2) More commonly API these days. |
|
|
Term
| What are the 6 clinically relevant Enterobacteriaceae? |
|
Definition
1,2,3 and 6 occur in "healthy" people (PEES)
4 and 5 are opportunistic
1) E. coli (Diarrhea, DysenteryUTI)
2) Salmonella (Diarrhea and Enteric fever)
3) Shigella (Dysentery)
4) Klebsiella (UTI, bacteremia)
5) Proteus (UTI)
6) Yersinea (Plauge, lymphadenitis) |
|
|
Term
Which enteric enterobacteriaeceae is
Glc +
Lac +
Suc +/-
Gas Glc +
H2S - |
|
Definition
| E. coli- diarrhea, dysentery and UTI in healthy and compromised individuals |
|
|
Term
Which enteric enterobacteriaeceae is
Glc +
Lac -
Suc -
Gas Glc +
H2S + |
|
Definition
| Salmonella- Diarrhea and enteric fever in "healthy" individuals |
|
|
Term
Which enteric enterobacteriaeceae is
Glc +
Lac -
Suc +/-
Gas Glc -
H2S - |
|
Definition
| Shigella- Dysentery in "healthy" people |
|
|
Term
| How can you tell between Shigella and Salmonella in terms of biochemical tests? |
|
Definition
Both are lactose-negative (E. coli is positive)
Salmonella can metabolize H2S (black in TSI medium), while Shigella cannot |
|
|
Term
| Which Enterobacteriaceae cause infections in "healthy" people vs. "Comromised" individuals? |
|
Definition
1 Healthy= Salmonella, E. coli, Shigella, Y. spp.
2) Compromised= Klebsiella, Proteus, E. coli and others |
|
|
Term
| What is the reservoir and transmission of E. coli? |
|
Definition
1) Humans are reservoir for humans
2) Transfered through food/water. |
|
|
Term
Which disease is each of the following E. coli serotypes associated with?
1) O26:H11
2) O157:H7
3) O148:H28
4) O4:H5
5) K1 |
|
Definition
1) EPEC
2) EHEC
3) ETEC
4) UTI
5) Neonatal meningitis |
|
|
Term
| Which virulence factors are associated with E. coli? |
|
Definition
1) Fimbrial (unique pili for each isolate that attach to host mannose) and Afimbrial adhesions
2) Iron acquisition with Siderophores (small, non-protein iron thieves).
3) Toxins
- LPS endotoxin
- Hemolysin (Hly) in polynephritis
- Heat-stable enterotoxin (STa)- small/uses intestinal cGMP to stimulate fluid/electrolyte secretion
- Heat-labile enterotoxin (LT)- large/uses cAMP
- Shiga toxin (STX) innactivates ribosomes to stop protein synthesis in kidney cells |
|
|
Term
| Which toxins are utilized by E. coli? |
|
Definition
- LPS endotoxin
- Hemolysin (Hly) in polynephritis
- Heat-stable enterotoxin (STa)- small/uses intestinal cGMP to stimulate fluid/electrolyte secretion
- Heat-labile enterotoxin (LT)- large/uses cAMP
- Shiga toxin (STX) innactivates ribosomes to stop protein synthesis in kidney cells |
|
|
Term
| What are 2 mechanisms by which pathogens are able to colonize in spite of host defenses? |
|
Definition
1) Novel adhesins
2) Strategies to avoid immune recognition (molecular mimicry) |
|
|
Term
| Which E. coli toxin is homologous to Cholerae toxin? |
|
Definition
| Heat-Labile enterotoxin (LT)- 1A and 5B subunits with action to increase intestinal cAMP. |
|
|
Term
| What is the difference between Type II, III and IV secretion systems in gram-negative pathogens? |
|
Definition
II) SIC or TAT to get to periplasm, and then out through pore.
III) Protein syringe that spans both membranes (Shigella, Salmonella and Y. pestis)
IV) DNA/Protein syringe that spans both membranes (H. pylori and Legionella) |
|
|
Term
| Which biotypes of E. coli can cause Intestinal disease? |
|
Definition
1) ETEC (enterotoxin)
2) EPEC (enteropathogenic)
3) EAEC (enteroaggregative)
4) EIEC (enteroinvasive)
5) EHEC (enterohemorrhagic) |
|
|
Term
| Which E. coli biotype that causes intestinal disease colonizes the intestine with unique, plasmid-encoded pili (CFAI, II and III) and uses STa and/or LT toxins in its pathogenesis? |
|
Definition
ETEC (OH148:H28)
Causes watery diarrhea in infants and travelers. Also in some foods. |
|
|
Term
| How does EPEC cause intestinal disease and infant diarrhea in developing countries? |
|
Definition
Attaching and Effacing (A/E) lesions on biopsy
1) EPEC adheres to enterocyte with plasmid-encoded bundle-forming pilus (BFP)
2) Attachment allows Type III delivery of TIR to to host cell
3) TIR, now on host cell, can bind up EPEC Intimin, causing an even closer interaction to occur and a pedestal to form
4) Diarrhea ensures. |
|
|
Term
Which intestinal disease-causing biotype of E. coli causes chronic diarrhea in HIV+ individuals, infant diarrhea (USA) and traveler's diarrhea?
How does it do this? |
|
Definition
EAEC (no fecal lymphocytes)
1) Adheres to enterocytes as aggregates of many EAEC cells
2) Increase mucous production creates protective biofilm for aggregate
3) EAST toxin may be important |
|
|
Term
| How does EIEC cause intestinal disease? What other bacteria are they similar to? |
|
Definition
Similar to Shigella in pathogenic mechanisms and clinical illness (Watery diarrhea with blood and fecal leucocytes)
1) Invade enterocytes using common pili and afimbrial adhesions
2) Lyse endocytic vesicles and escape to cytoplasm for multiplication and cell destruction
** have type III secretion system but no identified enterotoxin** |
|
|
Term
| How can you tell EIEC from EAEC based upon clinical presentation? |
|
Definition
EAEC will have watery diarrhea WITHOUT fecal leucocytes
EIEC have blood and fecal leucocytes in feces. |
|
|
Term
| Which E. coli biotype is the most common cause of hemolytic uremic syndrome (acute kidney failure in children)? |
|
Definition
EHEC
** but also recently seen in EAEC strains with Stx |
|
|
Term
| What is the relationship between antibiotic use and hemolytic uremic syndrome (HUS)? |
|
Definition
| They increase the risk in EHEC infection. |
|
|
Term
| How can EHEC be transmitted? |
|
Definition
1) Ingestion of undercooked meat
2) Petting zoos |
|
|
Term
| What is the pathogenesis of EHEC infection? |
|
Definition
1) Incubation of 2-4 days (long-lasting diarrhea will go from clean to bloody)
2) "EPEC+ Shiga" mechanism.
Close adherence via intimin, followed by production of Stx, which causes colonic damage and kidney damage when absorbed into circulation. |
|
|
Term
| What is the difference between CA-UTIs and Nosocomial UTIs in terms of the % caused by E. coli biotypes? |
|
Definition
E.coli UTI has cystitis (bladder) and pyelonephritis (kidney), and is most common in sexually-active women
CA-UTI is 80%, while Nosocomial-UTI is only 20% |
|
|
Term
| Explain the virulence factors associated with E. coli UTIs. |
|
Definition
1) Type 1/ common pili (mannose-binding)
2) P-pili which binds Forssman dissacharide antigen on kidney epithelium (Pyelonephritis)
3) Hemolysin, Endotoxin and Invasiveness (can go intracellular!) |
|
|
Term
What is the relationship between K1 antigen in E. coli and neonatal meningitis?
How does endotoxin fit in? |
|
Definition
75% of E. coli meningitis from K1 antigen
- Homopolymer of sialic acid that inhibits phagocytosis and complement activation (molecular mimicry of host)
- Endotoxin from LPS is more important for symptoms (fever, shock). |
|
|
Term
| How do you diagnose E. coli infection? |
|
Definition
Culture!
1) MacConkey agar for pink Lac(+) colonies
2) Use API to further differentiate
3) PCR for biotype |
|
|
Term
| What treatment/prevention methods are associated with E. coli? |
|
Definition
1) Antibiotics for neonatal meningitis and UTIs
2) Symptomatic for ETEC
3) Kidney dialysis and transfusion for HUS caused by EHEC ( DON"T USE ANTIBIOTICS) |
|
|
Term
| How can you differentiate between H. pylori and Campylobacter jejuni? |
|
Definition
-C. jejuni grows best at 42 degrees and does not produce urease
-H. pylori grows best at 37 and produces urease. |
|
|
Term
True or False:
H. pylori is an enterobacteriaceae |
|
Definition
False!
It is curved, gram-negative rod (like Campylobacter) that is motile and microaerophilic (not facultative anaerobe) |
|
|
Term
| What are the reservoirs/transmission of H. pylori? |
|
Definition
1) Human reservoir (other spp. in animals)
2) Transmitted via fecal-oral or oral-oral in developing countries (70% abroad vs. 30% colonized in US)
**Colonization increases with age |
|
|
Term
| What virulence factors are associated with H. pylori? |
|
Definition
1) Urease and Flagella (get them to mucous) to raise pH of environment.
2) VacA damages stomach epithelium and causes ulcers
3) cag Pathogenicity island with type IV secretion system and CagA (inflammation)
4) LPS (inflammation) |
|
|
Term
| Explain H. pylori pathogenesis. |
|
Definition
1) Colonized people have mild GI symptoms which may persist as chronic gastritis
2) >1% of colonized people develop duodenal/gastric ulcers (urease, VacA, CagA)
3) Can lead to gastric cancer/lymphoma |
|
|
Term
| How do you diagnose/treat H. pylori infection? |
|
Definition
1) Biopsy with gram-stain, culture and urease test
2) Breath test with C14 radioactive urea to check for urease
3) Combination Therapy
-Antimicrobial (macrolide/clarithromycin and vismuth salts)
-Acid-blocker (omeprazole)- gets >90% |
|
|
Term
| How do VacA, CagA and LPS fit into H. pylori pathogenesis? |
|
Definition
VacA- damages stomach epithelial cells
CagA- effector of cag pathogenicity island that induces inflammation
LPS- Induce inflammation. |
|
|
Term
| How do you treat H. pylori? |
|
Definition
| Combination Therapy with Macrolide (Clarithromycin) and an Acid-blocker (Omeprazole) |
|
|
