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Microbiology EXAM 1


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Family Enterobacteria is gram negative or gram positive? What shape are they?
Gram negative, rod shaped bacteria
Family Enterobacteria is obligately anaerobic.
False, they are FACULTATIVELY anaerobic.
Where can Family Enterobacteria be found?
Soil, water, fruits, vegetables, grains, plants, trees, and humans
Are Family Enterobacteria motile or non-motile?
Can be either. If motil, by peritrichous flagella.
Describe how Family Enterobacteria is divided based upon the clinical criteria of lactose fermentation.
Lactose fermenters are opprotunists while non-lactose fermenters are FRANK PATHOGENS and as such will cause disease.
Describe how opportunistic pathogens infect the host's body.
Usually the host defenses are altered in some way to allow the opportunists to infect the body site.
Describe how frank pathogens infect the host's body.
Do not require the alterations of the host defense mechanisms to cause the disease.
Rapid lactose fermenters are called?
How should samples to detect Family Enterobacteria for treatment be handled?
Early in the course of the enteric disease before the initiation of treatment, repeat specimens should be cultured, specimens that cannot be cultured soon after collection should be placed in transport media.
Name some transport media for Family Enterobacteria.
1. Buffered glycerol saline 2. Ames medium 3. Specimen preservation media
Name specimens that can be submitted to isolate Family Enterobacteria.
Biopsy material, wound exudates, body fluids, blood, urine, feces, dust and litter samples, hatchery debris, post mortem samples.
Define selective.
Refers to media that allow certain genera while inhibiting others.
Define differential.
Allows most if not all enterics to grow, thus enabling the lab to select different colonies bases upon appearance.
Eosin Methylen Blue Agar
Inhibits gram positive bacteria, fermentative organisms produce acid that changes the color of the indicator giving the colony a blue violet color.
MacConkey's agar
Inhibits gram positive bacteria, lactose fermentators turns the colonies red or pink in color.
Hektone enteric agar
More selective that either MacConkey's or EMB, bromthymol blue as fermentation indicator. Fermentative organisms appear Salmon in color.
Brilliant green agar.
Lactose or sucrose fermenters appear as yellow. Lactose or sucrose non-fermenters appear pink.
Salmonella-Shigella medium
Lactose fermenters appear red by neutral red. Non lactose fermenters appear colorless.
Xylose-Lysine Deoxycolate
Rapid fermentation which is almost universal among enteric bacteria except Shigella. Appear as black centers with H2S.
Name some examples of rapid lactose fermenters.
Escherichia Klebsiella Enterobacter
Name slow or non-lactose fermenters.
SALMONELLA, shigella, proteus, citrobacteri, Yersinia
E.coli can be found EVERYWHERE.
True. It is found in the intestinal tract of all warm blooded animals, but are usually absent in intestines of fish and cold blooded animals.
E. coli characteristics 1. Gram ____ 2. Motile? 3. Capsule?
1. gram negative short rods 2. motile, peritrichous flagella 3. capsule is present-- EMB is important
E.coli are serotyped based on...
LPS antigens 1. O (Somatic) 2. H (Flagellar) 3. K (Capsular)
Name important types of capsular antigens for E.coli.
K88- pig pathogen K99- calf, sheep and swine diarrhea
E. coli is always pathogenic.
False, there are non pathogenic and pathogenic species of which there are gradation of virulence and ability to produce disease.
Describe the mechanism of pathogenesis of e. coli.
1. localizes in SI 2. Produce toxin 3. Absorption of toxin 4. Action of toxin elsewhere
Where are the endotoxins located in e.coli?
Embedded within the outer layer of cell wall which are then released with the bacteria is lysed. These toxins are less toxic than exotoxins.
E.coli can produce exotoxins as well as endotoxins.
True. These toxins are called are ENTEROTOXIN.
E.coli produced both endotoxins and exotoxins.
True. The exotoxins are called ENTEROTOXIN. The toxin activate adenylate cyclase which results in increased cAMP. The increased cAMP causes hypersecretion of water and chlorides into the gut lumen result in fluid loss.
Name the two disease syndrome in cattle produced by E.coli.
Septicemic colibacillosis or colisepticemia and enteric colibacilloisis.
Why is it important that the calve has colostrum?
The calve will ingest e.coli from its enviroment and it will become a part of its normal flora. The colostrum may inhibit the sudden increased rate of multiplication of the organisms in the calf's intestine.
What is a common cause of mastitis in cows?
E. coli-- usually associated with poor sanitation.

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