Citrobacter, Enterobacter, Escherichia, Klebsiella, Moganella, Proteus, Salmonella, Shigella, Serratia, and Yersinia
Where are enterobacteriaceae found?
Ubiquitous: soil, water, vegetation
1) ___ of all septicemia
2) ____ of UTIs
3) Many intestinal infections
4) Pathogenic or opportunitistic?
- 1) 30-35% of septicemia
- 2) More than 70% of UTIs
- 4) Some are solely pathogenic, while others are opportunistic
Enterobacteriaceae share a common antigen. What is it?
What is their major cell wall antigen?
- Enterobacterial common antigen
- Major Cell Wall antigen = LPS
Enterobacteriaceae are aerobes/non-aerobes?
Facultative anaerobes; Grow rapidly aerobically or anaerobically.
Enterobacteriaceae ferment glucose, reduce nitrate are catalase-? and oxidase-?
- Oxidase-N (absence of oxidase is a distinguishing characteristic)
LPS is an endotoxin or exotoxin? Toxicity is due to?
Endotoxin, Lipid A
Name 9 things LPS can initiate.
- Complement activation
- Cytokine release
- Intravascular coagulation
- Decreased preipheral circulation
- Shock Death
E. coli have _______ that help it adhere to host cells in the urinary or GI tract. These include?
- Colonization factor antigens (CFA/I, CFA/II, CFA/III)
- Aggregative adherence fimbriae (AAF/I, AAF/III)
- Bundle-forming pili (Bfp)
- P pili
- Ipa proteins (invasion plasmid antigens)
- Dr fimbriae
Name the 4 exotoxins of E.coli.
- Shiga toxins (Stx-1, Stx-2)
- Heat-stabile toxins (STa, STb)
- Heat-labile toxins (LT-I, LT-II)
- Hemolysins (Hly)
E. coli Phase Variation:
Serologic classification of Enterobacteriaceae is based on 3 major groups of antigens. What are they? Which ones are under genetic control?
- 1) Somatic O polysaccharides (specific to each genus)
- 2) Capsular K antigens (type-specific polysaccharides)
- 3) Flagellar H proteins
K & H antigens are under genetic control and can be alternately expressed or not expressed (phase variation)
Phase variation (E. coli) protects the bacteria from ________
Ab-mediated cell death
What are 4 common things E. coli causes?
- UTIs (80% of CA)
- Sepsis (most common cause)
- Neonatal meningitis
- Gastroenteritis (esp. in developing countries)
Most E. coli infections are _____________ except_______
Name 2 complications of E. coli's gastroenteritis.
E. coli Bacteremia originates from infections in the ______ or ____
GI or urinary tract
Name 2 groups have have a high mortality for E. coli Bacteremia.
- Immune compromised patients
- Primary infections in abdomen or CNS
Gram-Negative rods that cause UTIs originate in the ______, contaminate the _______, and ascend into the _______. May migrate to the kidney or prostate.
- Originate in the colon
- contaminate the urethra
- ascend into the bladder
E. coli UTI's tend to be caused by specific serogroups that possess? (2 things)
Lyse host cells and stimulate inflammation
E. coli UTI is also associated with catheter use in hospital
Adhesins in E. coli UTIs are optimized for attachment to cells lining that bladder and upper urinary tract. Name 3 types of adhesins.
These have very tight attachment
What 2 things will be detected in a urine sample from someone with an E. coli induced UTI?
- E. coli (duh)
- WBC's (from the inflammation)
Uropathogenesis of E. coli
- 1) Attachment of E. coli cells to epithelial cells/facet cells of bladder via adhesins
- 2) Internalization of bacteria into cells (phagocytosis)
- 3) Bacteria replicate in cells
- 4) Induces stimulation secretion of cytokines
- 5) Recuits macrophages and PMN to site of infection (this is what causes inflammation and pain during a UTI)
- 6) PMNs cause disruption of epithelial cell surface and allow exfoliation of bacteria out into the urine
What 2 things cause the majority of CNS infections in infants <1 month?
E. coli & Grp. B Streptococcus (S. agalactiae)
75% of E. coli Neonatal meningitis contain what capsular antigen. Where is this commonly found?
- K1 capsular antigen
- Found in GI tract of pregnant women and newborns
5 Virotypes of E. coli that cause gastroenteritis.
6th Group of E.coli that is not well characterized.
E. coli grows rapidly on most culture media, but which is most typical?
Which E. coli virotype has commercially avialable assay for toxin detection?
Many 0157 strains do NOT ferment ____, so _____ can be used as a screening tool.
sorbitol, MacConkey agar
What type of nutrients and what color are these two organisms on MacConkey agar?
2) E. coli
- 1) Amino acids, yellow/colorless
- 2) Lactose, pink
What causes the neutral red dye in a MacConkey agar plate to turn red?
What makes up the medium of a TSI Agar Slant?
TSI= Triple Sugar Iron
Glucose, lactose, sucrose (1:10:10) and phenol red (pH indicator) + Ferrous sulfate (H2S indicator)
TSI Agar Slant:
Acid Production =
H2S production =
- Acid Production = yellow
- Alkaline = Red
- H2S = Black color (FeS)
TSI Agar Slant:
Lactose or sucrose fermentation
Acid= yellow butt/slant
TSI Agar Slant:
Acid butt = yellow butt/ red slant
Treatment for E. coli UTIs
cephalosporins, trimethprim/sulfamethoxazole, nalidixic acid (sometimes), tetracycline.
Amoxicillin resistance is increasing
Tx for E. coli diarrhea or hemorrhagic colitis.
- Provide supportive therapy (e.g. fluids)
- Use of antibiotics is controversial
Tx for E. coli HUS
- IV fluids and nutritional supllementation
- Blood transfusions may be needed
- Dialysis (short-term)
More than 85% of patients with the most common form of HUS recover complete kidney function