Strains of O:K:H antigens that are associated ubiquitously with certain pathogens imply they evolved away from other lineages to exchange with. These completely similar strains are clones.
Virulence Factors for Enterobacteriaceae
•Endotoxin(LPS)- endotoxin leading to shock
•Capsule -poor immunogens & antiphagocytic
•Antigenic phase variation- K & H antigens
•Type III secretion- syringe-like injectors
•Sequestration of iron- different siderophores
•Serum resistance – OmpA binds C4BP
•Exotoxins - variety of enzymatic and lytic toxins
Medical Terms for Diseases
•Diarrhea: frequent, liquid stools (stools that assume the shape of their container).
•Dysentery: a disease marked initially by frequent watery stools but followed by scant stool production characterized by excretion of mucus and blood. There is usually abdominal pain, fever, and tenesmus.
•Enteritis: inflammation of the intestine.
•Enteric fever: an acute illness presenting as fever, headache, abdominal pain, and occasional skin rash. There is bacteremia.
•Food poisoning: the ingestion of a food containing a preformed toxin. No growth of the
bacteria required in the host.
Scope of Gastrointestinal Disease
Number 2 killer of children after pneumonia
Bangladesh: 7 srs infections a year for first two years
US: average 2 cases a year
E. Coli Morphology
Most common facultative aerobic
Gram neg rod in GI tract
Diarrheagenic E. coli
•Diffuse aggregative E. coli (DAEC)
Extraintestinal E. coli
Septic Shock/UTI (UPEC)
Most usually from initial infection of GIT/UT
High mortality in immunocomp/ primary abdominal/CNS infection
E. coli is leading cause of endotoxic shock/death
Septic Shock from E. coli
Too much inflammation from gram - septicemia (LPSs)
IL-1/6 produced by macrophages/lymphocytes/endothelial/keratinocytes and causes fever by release of prostaglandins in hypothalamus, contributes to hypotension/anorexia/increased PMNs/Increased transferrin
•E. coli (2nd) and group B streptococci (1st) cause majority of CNS infections in infants younger than 1 month
• 75% of E. coli possess K1 capsular antigen
•Commonly found in GI tract of mother and child
Uropathogenic E. coli (UPEC)
Contamination of urethra from colon
Ascends urethra to bladder, can infect kidneys and prostrate
Type I pili under phase shift
Causes 70-90% of uncomplicated UTI
Cystitis Symptoms: dysuria, frequent and urgent need to urinate