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Microbiology > Unit 7B > Flashcards

Unit 7B Flashcards

1
Q

Describe gram negative rods -Family Enterobacteriaceae

A

range from non pathogenic to primary pathogens

Most intestinal pathogens

Some saprophytic bacteria

Many are coliforms

Facultative anaerobes

Have flagella (motile)

Catalase negative

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2
Q

How are species of enterobacteriacrae divided based on their ability to ferment lactose

A

In MacConkey’s agar: they will br PINK if they are positive or WHITE if negative

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3
Q

Describe how MacConkey’s agar is selective AND differential

A

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

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4
Q

Examples of enterobacteriaceae

A 
Escherichia 
Salmonella 
Enterobacter 
Klebsiella 
Proteus 
Yersinia
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5
Q

Describe Escherichia coli (E. coli)

A

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

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6
Q

E. coli can cause _____ is allowed ti invade internal organs

A

Severe disease

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7
Q

Describe the parts of the name:

EHEC O157: H7

A

EHEC: type of E. coli
O157: o antigen
H7: flagellum

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8
Q

What are pathogenic factors of E. coli

A

Endotoxins: trigger inflammation

Capsules: resist drying ajd phagocytosis

Some are hemolytic

Some produce exotoxins (enterproxins act on the GIT)

Have acquired antibiotic resistance

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9
Q

How is E. coli controlled and prevented

A

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

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10
Q

What are the 3 most common causes if food borne illnesses in people

A

Salmonella
E.coli
Campylobacter

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11
Q

Describe E.coli diarrhea, enteritis and food borne disease

A

Causes bacterial enteritis resultingnin diarrhea

Fecal oral transmission (animal to animal or zoonosis)

Contaminated meat, dairy and produce

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12
Q

Type and secerity of diarrhea/damage from enteropathogenic E. coli depends on

A

Strain and exotoxin it produces

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13
Q

What are the 3 major groups of enteropathogenic E. coli that causes bacterial diarrhea least to most severe

A

ETEC: enterotoxigenic E. coil

EPEC: enteripathogenic E. coli

EHEC: enterohemorrhagic E. coli (most severe)

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14
Q

Describe ETEC: enterotoxigenic E. coil

A

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

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15
Q

Describe EPEC: enteripathogenic E. coli

A

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

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16
Q

Describe EHEC: enterohemorrhagic E. coli

A

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

17
Q

what is EHEC O157: H7

AKA: hamburger disease

A

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

18
Q

What is some general prevention of EHEC O157:H7

A 
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
19
Q

What is some targeted prevention of EHEC O157:H7

A

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%)

20
Q

What concerns come with Raw meat based diets for dogs

A

Large portion of dogs will shed pathogenic/zoonotic E. coli in feces and saliva

Huge concern for immunocompromised people

21
Q

What is E.coli -neonatal septicemia

A

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

22
Q

What is coliform mastitis

A

Acute, severe mastitis caused by any member if enterobacteriaceae, E. coli most common

Most cases can be cleared by the immune system

23
Q

Environmental mastitis is associated with

A

Fecal contamination of bedding

Fecal E.coli - infects mammary glands - colonization in milk

24
Q

What happens with severe cases of coliform mastitis

A

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)

25
Q

What is the treatment and prevention of coliform mastitis

A

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

26
Q

Describe E. coli in poultry

A

E. coli can penetrate the eggshell and infect the yolk sac and spread to thw embryo and causes death of the embryo

27
Q

What is cellulitis in broilers

A

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

28
Q

Describe E. coli urogenital tract infections

A

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

29
Q

What are struvites

A

Type of crystal which can cause obstruction in the urinary tract

30
Q

Whatbare the risk factors for urogenital tract infections by E. coli

A

Female anatomy, estrus, fecal contamination

Urinary catheterization, poor cystocentesis technique

31
Q

Explain treatment of urogenital tract infections by E. coli

A

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

32
Q

Describe the diagnosis of pathogenic E. colo

A

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)

33
Q

Why must samples for pathogenic E. coli on post mortem bodies need to be taken ASAP

A

Intestinal bacteria (especially clostridium and E.coli) spread rapidly after death

Microbiology (12 decks)

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