Unit 7B Flashcards
Describe gram negative rods -Family Enterobacteriaceae
range from non pathogenic to primary pathogens
Most intestinal pathogens
Some saprophytic bacteria
Many are coliforms
Facultative anaerobes
Have flagella (motile)
Catalase negative
How are species of enterobacteriacrae divided based on their ability to ferment lactose
In MacConkey’s agar: they will br PINK if they are positive or WHITE if negative
Describe how MacConkey’s agar is selective AND differential
Selective: bule salts select for enteric bacteria
Selective: crystal biolet inhibits gram positive growth
Differential: lactose and phenol red identify bacteria that produce lactic acid
Examples of enterobacteriaceae
Escherichia Salmonella Enterobacter Klebsiella Proteus Yersinia
Describe Escherichia coli (E. coli)
Gram negative bacilli
Facultative anaerobe
Motile
Catalase negative
Lactose fermenter (pink on macconkey’s agar)
Large grey colonies on blood agar (some are hemolytic)
Normal in intestinal flora
Ubiquitous
Coliform
Can survive up to 6 months in manure (predominant in feces)
Common in organic biofilms
Some are non pathogenic, opprotunistic or pathogenic (depends on strain and infectious dose)
Can be found in some species but not in others and cause disease
E. coli can cause _____ is allowed ti invade internal organs
Severe disease
Describe the parts of the name:
EHEC O157: H7
EHEC: type of E. coli
O157: o antigen
H7: flagellum
What are pathogenic factors of E. coli
Endotoxins: trigger inflammation
Capsules: resist drying ajd phagocytosis
Some are hemolytic
Some produce exotoxins (enterproxins act on the GIT)
Have acquired antibiotic resistance
How is E. coli controlled and prevented
Hygiene: control of feces in environment, control of fecal contaminatiok of food and water
Host health: vaccines, fecal exposure
Most Disinfectants kill E. coli
Pasteurization kills E. coli
What are the 3 most common causes if food borne illnesses in people
Salmonella
E.coli
Campylobacter
Describe E.coli diarrhea, enteritis and food borne disease
Causes bacterial enteritis resultingnin diarrhea
Fecal oral transmission (animal to animal or zoonosis)
Contaminated meat, dairy and produce
Type and secerity of diarrhea/damage from enteropathogenic E. coli depends on
Strain and exotoxin it produces
What are the 3 major groups of enteropathogenic E. coli that causes bacterial diarrhea least to most severe
ETEC: enterotoxigenic E. coil
EPEC: enteripathogenic E. coli
EHEC: enterohemorrhagic E. coli (most severe)
Describe ETEC: enterotoxigenic E. coil
Part of normal flora
Causes secretory diarrhea (enterotoxin acts on small intestine cells and causes them to secrete excess ions and water into lumen) (no physical damage to cells)
Animal becomes dehydrated and loses electrolytes
Describe EPEC: enteripathogenic E. coli
Attach to surface of intestinal cells and destroys the microvilli on them
This causes decreased absorption of nutrients causing malabsorptive diarrhea (nutrients and water) (some microscopic damage to the intestines)
Diarrhea is mucoid and can be chronic
Most affected: rabbits, humans, dogs
Describe EHEC: enterohemorrhagic E. coli
Bacteria Produce Shiga toxin: enters intestinal cells and blocks protein synthesis and kills the cell, resukts in ulcers and bleeding
Resukts in hemorrhagic diarrhea
Part of normal flora, causes enteritis if transmitted to others
Can cause significant disease in calves and piglets
what is EHEC O157: H7
AKA: hamburger disease
Part of normal flora in 30% of cattle
Causes zoonotic hemorrhagic enteritis in people
Food borne transmission (food contaminated with feces, especially beef, comtaminated milk or unpasteurized milk, plants fertilized with contaminated manure
What is some general prevention of EHEC O157:H7
Hygiene during food prep and handling Meet and produce inspection Thorough cooking of ground beef Avoid unpasteurized milk Wash fruits and vegetables Bacterial counts in fertilizer
What is some targeted prevention of EHEC O157:H7
Cannot treat affected cattle but can decrease normal floar load made of it
Vaccines for cattle specific to this strain
(Boosts immune system, decreases shedding and reduces cases in people by 50-85%)
What concerns come with Raw meat based diets for dogs
Large portion of dogs will shed pathogenic/zoonotic E. coli in feces and saliva
Huge concern for immunocompromised people
What is E.coli -neonatal septicemia
Most common gram negative cause of septicemia
Most susceptible: foals, calves, piglets lacking colostrum or if they ingested large quantities of fecal matter
Enters via umbilicus or through ingestion and spreads to blood, lungs, liver, spinal cord, heart, kidneys
Diagnosis is made by culturing internal organs like the liver when they are dead
What is coliform mastitis
Acute, severe mastitis caused by any member if enterobacteriaceae, E. coli most common
Most cases can be cleared by the immune system
Environmental mastitis is associated with
Fecal contamination of bedding
Fecal E.coli - infects mammary glands - colonization in milk
What happens with severe cases of coliform mastitis
Hugh numbers fo bacteria release large amounts of endotoxin
Can be local in the mammary goand (severe damage) or spread systemically (endotoxic shock)
Most commonly causes death in cows (endotoxic shock or euthanasia)
What is the treatment and prevention of coliform mastitis
Fluids, stripping infected gland
Clinical signs appear too fast to start antibiotics and are not allowed in food animals
Prevent with good hygiene and vaccines in dry periods
Describe E. coli in poultry
E. coli can penetrate the eggshell and infect the yolk sac and spread to thw embryo and causes death of the embryo
What is cellulitis in broilers
Infection of skin, subcutaneous ajd muscles
Bacteria from feces enters via scratches and wounds on the skin, commonly affects breast and around the anus
Tissue becomes pale, yellow, white and firm
Birds are condemned and cannot be eaten
Describe E. coli urogenital tract infections
Common cause of UTIs
Caused by multi-drug resistant E. coli strains (community or hospital acquired)
E. coli produce urease to increase pH to 7.5
Leads to secondary struvite formation
What are struvites
Type of crystal which can cause obstruction in the urinary tract
Whatbare the risk factors for urogenital tract infections by E. coli
Female anatomy, estrus, fecal contamination
Urinary catheterization, poor cystocentesis technique
Explain treatment of urogenital tract infections by E. coli
Most are easily treated
Community acquired multidtug resistant strains are harder to treat
Nosocomial hospital acquired multifrug resistant strains are very hard to treat
Identification of gram negative tods on urine microscopy is an indication to send for culture and sensitivity
Describe the diagnosis of pathogenic E. colo
Cultures
Testing for specific strains
Testing for specific enterotoxins
Testing for antibiotic sensitivity (has lots of plasmid based antibiotic resistance)
Post mortem samples MUST be frok freshly dead aniamls (within hours)
Why must samples for pathogenic E. coli on post mortem bodies need to be taken ASAP
Intestinal bacteria (especially clostridium and E.coli) spread rapidly after death
