Gastrointestinal Infections I (20) Flashcards
What are the normal functions of the GI tract?
digestion
absorption
protection
What are the antibacterial substances of the mouth?
lysozyme and IgA
What are the immune defenses of the GI tract?
mouth - antibacterial substances, flow of saliva
stomach - low pH, varies among species and meals
intestinal mucus - physical barrier, antimicrobial enzymes
mucosal cells
GALT
The GI tract is _____ at birth
sterile
microbes acquired from environment shortly after birth
majority are anaerobes in all species
diet affects composition of flora
Milk-fed animals have what kind of GI flora?
lactobacilli
What is of little diagnostic value when diagnosing GI conditions?
fecal cultures and gram’s staining of fecal material are of little diagnostic value
What is present in large numbers in the GI tract?
e. coli
requires additional testing for interpretation
What is the role of normal microflora?
maintain normal intestinal function
prevent pathogenic bacterial growth
What disrupts normal microflora?
antimicrobials
stress
drugs that alter GI motility
sudden diet changes
What is gastroenteritis?
syndrome characterized by GI symptoms including nausea, vomiting, diarrhea, and abdominal discomfort
What is dystentery?
an inflammatory disorder of the GI tract often associated with blood and pus in the feces and accompanied by symptoms of pain, fever, abdominal cramps, usually resulting from disease of the large intestine
What is enterocolitis?
inflammation involving the mucosa of both the small and large intestine
What are characteristics of E. coli?
gram-negative rod
facultative anaerobe - can grow with or without O2
extracellular bacteria
What are the E. coli pathotypes?
enterotoxigenic E. coli (ETEC)
enteropathogenic E. coli (EPEC)
shigatoxigenic E. coli (STEC)
enteroinvasive E. coli (EIEC)
E. coli classification is based on what?
serology
pathology
What are the parts of E. coli based on serology?
cell wall O antigen
flagella H antigen
pili/fimbriae ‘F’ antigen
capsule K antigen
T/F: Regarding E. coli, you can predict pathogenicity based on O, H, and K antigen types
FALSE - these are markers to separate E. coli into groups/types
What confirms pathogenicity of ETEC?
fimbrial antigens
ETEC is an interplay between ______
- pathogen factors
- environment
- host
What is fimbriae (pili) regarding ETEC?
encoded on plasmids
proteins that extend from the cell wall
required for bacterial adhesion to CHO receptors on epithelial cells
binding is HOST-specific
F5: lambs
F4: pigs
What is enterotoxin production?
- encoded on plasmids
- two toxins: heat labile (LT) and heat stable (ST) enterotoxins
STa (calves) and STb (piglets)
What are environmental and host factors of E. coli contamination?
high inoculum dose
age - intestinal receptors present ONLY in neonates
immune status
ETEC pathogenicity is mediated by both ______
fimbriae & enterotoxins
binding (mediated by fimbriae) results in large numbers of bacteria in direct contact with epithelial cells
What are the effects of E. coli enterotoxin?
hypersecretory (watery) diarrhea
calf scours
What are vilous cells for E. coli?
absorb Na+ and Cl- into the cell
absorb substrates into cells via sodium co-transporters
effect: ABSORPTION
What are crypt cells for normal GI physiology of ETEC?
Na+ is recycled
secretes Cl- out into lumen
effect: SECRETION
What are NET effect of crypts and villi cells for normal GI physiology of ETEC?
ABSORPTION
What are enterotoxins for normal GI physiology of ETEC?
stimulate adenylate cyclase
inhibit Na+ and Cl- uptake in villous cells
increased Cl- secretion in crypt cells
HYPERSECRETION
What is important to note about ETEC and enterotoxins?
bound to the intestinal epithelium there is NO direct damage to the intestinal epithelium
What are clinical signs of ETEC?
watery diarrhea
yellowish or white scours
no invasion, inflammation, or cell damage
What is diagnosis of ETEC diarrhea?
history and management factors - incidence mainly confined to young animals
sampling - FRESH & before antibiotics
latex agglutination test
multiplex-PCR for virulence factors
NOT foul-smelling, not hemorrhagic
What is latex agglutination test regarding ETEC?
detects fimbrial antigens
- F5 and F41 in calves and lambs
F4 in pigs
What is the method of choice for diagnosing ETEC diarrhea?
Multiplex-PCR for virulence factors
What is treatment for ETEC?
important to correct dehydration and electrolytes
antibiotics
immunoglobulins
How do you prevent ETEC?
sanitation!
disinfection
reduce overcrowding (move calves to individual calf pens)
reduce inoculum size
optimize passive transfer
What is EPEC or attaching and effacing E. coli (AEEC)?
CELL DAMAGE
hyper secretion and MALABSORPTION
usually DO NOT produce toxins
pili, intimin (eae)
What is STEC?
similar to EPEC
attaching an effacing (A/E) lesions
hyper secretion and MALABSORPTION
usually produce toxins (Shiga toxins)
What is edema disease in piglets?
STEC
usually occurs 1-2 wks post-weaning
produce fimbirae and toxins (Stx2e)
- binds to receptors to vascular endothelium in CNS, stomach, forehead, eyelids, and other sites
increased vascular permeability and edema
no cell damage
What is enteroinvasive E. coli (EIEC)?
invades the cells, and then into the deeper portions of the intestine
only known to produce disease in humans
