Enterobacteriaceae (E.Coli-Specific) Flashcards
(44 cards)
Describe the general structure of Enterobacteriaceae:
Gram negative rods
Many have flagella and a capsule
H and K Antigens
LPS
What are the locations of H and K Antigens in Enterobacteriaceae?
H-antigen: located in peritrichous flagella
K-antigen: located in capsule
Function of the capsule in Enterobacteriaceae?
Important in causing extraintestinal colonization, UTI, and invasive disease
Describe the composition of LPS in the membrane of Enterobacteriaceae.
O-antigen: located on outer most domain
Core oligosaccharide
Lipid A: inner most region of LPS
What is significant about of O-antigen?
Targeted antigen for detection in laboratory
What is the pathogenesis of lipid A?
Causes toxicity: fever, diarrhea, and possible fatal endotoxic shock
Name the 6 virulence factors of Enterobacteriaceae:
Endotoxin (LPS) Capsule Antigenic Phase Variation Type III secretion systems Sequestration of growth factors
What is the significance of antigenic phase variation in Enterobacteriaceae?
Alte expression of H and K antigens to protect organisms from Ab mediated cell death
What is the significance of Type III secretion systems in Enterobacteriaceae?
Facilitates secretion of virulence factors into host cells
Morphology of Enterobacteriaceae
Gram-negative rods that stain red
Culture Characteristics of Enterobacteriaceae
Grow on standard media (i.e. blood agar)
5 Biochemical characteristics of Enterobacteriaceae
Facultative (aerobic & anaerobic)
Ferment glucose
Reduce nitrate to nitrite
Oxidase negative
Grow on MacConkey Agar (salt)
What differentiates Enterobacteriaceae from other gram-negative rods?
Enterobacteriaceae is Oxidase negative
Non-lactose fermenting Enterobacteriaceae
Salmonella Shigella Proteus Yersinia Serratia
Lactose fermenting Enterobacteriaceae
E. coli
Klebsiella
Enterobacter
Citrobacter
6 Escherichia Coli Clinical Syndromes:
Gram negative bacteremia and sepsis
Most common contributor to community-acquired UTIs
Wound infections
Pneumonia in immunocompromised hospitalized patients
Meningitis in neonates
Gastroenteritis
Pathogenic Phenotype of Enterotoxigenic
E. coli (ETEC)
Elaboration of secretory toxins (LT, ST) that do not damage the mucosal epithelium but stimulate hypersecretion of fluids
Signs and Symptoms of Enterotoxigenic
E. coli (ETEC)
Profuse, watery, secretory diarrhea is predominant symptom. Often accompanied by mild abdominal cramps. Dehydration and vomiting occur in some cases.
Pathogenic Phenotype of Enteropathogenic E. coli (EPEC)
Adheres to epithelial cells in localized micro-colonies and causes attaching/ effacing lesions
Signs and Symptoms of Enteropathogenic E. coli (EPEC)
Usually occurs in infants.
Characterized by low-grade fever, malaise, vomiting, and diarrhea, with a prominent amount of mucus, but with no gross blood
Pathogenic Phenotype of Enteroinvasive E. coli (EIEC)
Invasion of epithelial cells
Signs and Symptoms of Enteroinvasive E. coli (EIEC)
Inflammatory diarrhea (Dysentery) similar to Shigella. Hallmarks are fever and colitis. Symptoms are urgency and tenesmus; blood, mucus, and many leukocytes in stool
Pathogenic Phenotype of Enterohemorrhagic E. coli (EHEC)
Shiga Toxin producing E. coli (STEC) -Carry cytotoxins (Shiga toxins, Stx1 and Stx2). Primarily caused by E.coli O157:H7
Signs and Symptoms of Enterohemorrhagic E. coli (EHEC)
Bloody diarrhea without WBCs. Often no fever. Abdominal pain is common. May progress to hemolytic uremic syndrome (HUS) or hemorrhagic colitis.