Exam 1 Flashcards
Define a Direct Test
Detect pathogens or products
Types of direct tests
Culture, PCR, Sequencing
Define an Indirect Test
Detect immune response (antibody) to pathogen
Types of indirect tests
Agglutination, ELISA, Lateral flow
Define Sensitivity
Ability to identify TRUE positives
Define Specificty
Ability to identify TRUE negatives
Define Positive Predictive Value (PPV)
Probability the disease is present when the test is positive
Define Negative Predictive Value (NPP)
Probability the disease is not present when the test is negative
Define Prevalence
What is the probability of the target condition occurring in the population
How do you calculate Sensitivity?
True positives / (all animals tested true positives + false negatives)
How do you calculate Specificity?
True negatives / (false positives + true negatives)
Define Screening Test
A sensitive test with few false negative results.
Define Confirmatory Test
A specific test with few false positive results.
Ideally, this would be a highly sensitive and specific test
What is a Bacterial or Fungal Culture?
Identification of bacteria and fungi through: colony and cell morphology characteristics and protein and nutrient-utilization differences
Does a culture require live bacteria/fungi?
Yes
How quickly can you get Culture Results?
Varies - but can be slow if the bacteria or fungi grow slowly
Sensitivity/Specificity of a culture?
Variable
What is PCR?
Identification of bacteria through exploitation of DNA sequence differences using DNA primers specific for a pathogen
Specificity/Sensitivity of a PCR?
Highly specific and sensitive
How quickly can you get PCR results?
Rapid results regardless of the pathogen
Do you need live bacteria/fungi for a PCR?
No- can be either live or dead
Can you do antimicrobial susceptibility testing with PCR? Why or why not?
No - there is no bacteria to isolate to grow in test
What is Sequencing?
Identification of bacteria by sequencing the entire genome or segments of DNA
Do you need live bacteria/fungi for sequencing?
No - can be live or dead
Benefits of Sequencing?
Allows for extremely specific identification
Allows for evaluation of the presence of genes related to virulence and antimicrobial resistance
Downfalls of sequencing?
Expensive and generally slow
Cannot do antimicrobial susceptibility testing as there is no bacterial isolate to grow in test
What is an Agglutination test?
Detects antibody by mixing patient serum with antigen of interest
Cross-linking of patient antibody with test antigen creates visible clumping
Specificity/Sensitivity of Agglutination Tests?
Less specific, more sensitive
*may see false positives necessitating a second confirmatory test
What is an ELISA?
Detects patient antibody to test antigen fixed to the plate
A more high-through put, automated test
Specificity/Sensitivity of ELISAs?
Generally good sensitivity and specificity
What is a Lateral Flow Test?
A rapid test that detects antigen or antibody
Specificity/Selectivity of a Lateral Flow Test?
Generally good specificity and selectivity
Ab Tests:
May see false positives if there is cross-reactivity between ??
May see false positives if there is cross-reactivity between pathogen of interest and another agent
Ab Tests:
May see false negatives if ??
May see false negatives if early in infection before detectible antibody is available
Ab Tests:
Can detect maternal antibody up to ??? age
Can detect maternal antibody up to 6 months of age
Ab Tests:
A single test DOES/DOES NOT differentiate (usually) between a previous infection, current infection or vaccine response
A single test does not differentiate (usually) between a previous infection, current infection or vaccine response
Negatives of using a Swab to Sample?
Small sample size
Reduced recovery of organisms from swab
Not good for fungi
What is MALDI-TOF?
Mass Spec to identify bacteria
Is A. bovis Gram + or Gram - ?
Gram +
Is A. Lingnieresii Gram + or Gram - ?
Gram -
Is E. coli Gram + or Gram - ?
Gram -
Is Salmonella spp. Gram + or Gram - ?
Gram -
Is Lawsonia intracellularis Gram + or Gram - ?
Gram -
Is C. perf Gram + or Gram - ?
Gram +
Is Brachyspira spp. Gram + or Gram - ?
Gram -
Which of the following are Facultative Anaerobes?
1. A. bovis
2. A. Lingnieresii
2. E.coli (ETEC/STEC)
3. C.perf
4. Salmonella spp.
A. Lingnieresii, E. coli, Salmonella spp.
Which bacteria are Obligate Anaerobes?
A. bovis, Brachyspira spp. C. perf
(ABC!)
Which bacteria are Microaerophilic?
Lawsonia intracellularis and Campylobacter spp.
Which bacteria are extracellular?
A. bovis, A. lingnieresii, Brachyspira spp, C. perf
(AABC)
Which bacteria are Facultative Intracellular?
E. coli (ETEC and STEC) and Salmonella spp.
Which bacteria are Obligate intracellular?
Lawsonia intracellularis
Which bacteria enter due to injury to the mouth/tongue?
A. bovis, A lingnieresii
Which bacteria form spores?
C. perf and Clostridioides difficile
Which bacteria are commonly found when feeding raw diets?
Salmonella spp. and Campylobacter spp.
What is the major predisposing factor of Clostridioides difficile?
Hx of antimicrobial use and hospitalization in horses.
Which bacteria is unable to be cultured?
Lawsonia intracellularis
Which bacteria can cause organ failure?
C. perf
Which bacteria attaches to M cells?
Salmonella spp.
Which bacteria stimulates crypt cell proliferation?
Lawsonia intracellularis
Which bacteria may require an antitoxin or neutralizing Ab?
C. perf
Which bacteria can cause Edema?
STEC and C. perf
Which bacteria require secondary testing? What are you testing for?
STEC and ETEC. PCR to determine is there are virulent genes present.
Which bacteria use fimbriae to attach to the host?
ETEC, STEC
Which bacteria have a predisposing factor of FPT?
ETEC, STEC, C. perf
Which bacteria use an internal flagella for motility?
Brachyspira spp.
Main differences between prokaryotes and eukaryotes
Prokaryotes: single chromosome. No mebrane bound organelles.
Eukaryotes: multiple chromosomes and membrane bound organelles.
Majority of the gram + cell wall is..?
a thick layer of peptidoglycan
Gram - cell wall is composed of:
small peptioglycan layer
outer membrane for protection (LPS)
Define an obligate aerobe
require oxygen for growth
define obligate anaerobes
cannot grow in the presence of oxygen
define facultative anaerobes
can use oxygen, but can grow in other atmospheres too.
define microaerophiles
need higher levels of CO2
a community of microorganisms found on or in a healthy animal
Microbiota (AKA normal flora)
the microbiota found at a given habitat and the host environment that they inhabit
microbiome
where do we find microbiota on the body
GI tract, upper resp, external eye, skin, lower urogenital tract
How is the microbiota established?
At birth, gradual maturation with different exposures (feed, stress, animal contact, envrionmental flora..) and genetics
role of microbiota in the health of the host
development of the immune system, colonization resistance, direct and indirect protection, host nutrition.
pathogen
a bacteria or fungi that causes Dz
pathogenicity
ability to cause Dz
Virulence
the degree of pathogenicity of the bacteria or fungi
Colonization
presence of bacteria or fungi on body surfaces that do not cause disease, which may be beneficial to the host (aka microbiota)
Common predisposing factors of the host
- underlying disease
- failure of passive transfer
- immunologically naive
- nutritional deficiency
common predisposing factors (environment)
- build up of pathogen load
- crowding/stress
- weather
- geographic location
- food/feed quality
- travel
Ingress
bacteria gain access to inner areas of the body with external connections but DO NOT cross epithelial barriers
Penetration
across epithelial barrier into deeper tissues
Common predisposing factors for oral infections:
‣ Trauma
‣ Foreign bodies
‣ Rough feed
‣ Tumors
‣ Dental issues
‣ Viral infections, especially those that cause oral lesions
Common presenting signs of oral infections
‣ Swellings
* Abscesses
* Osteomyelitis
‣ Halitosis or fetid odor
‣ Difficulty swallowing, eating or drinking
‣ Tooth decay or loss
‣ Nasal discharge
‣ Salivation
‣ Cough
Which bacteria produce endotoxins?
E. coli ETEC/STEC, Brachyspira spp.
Are endotoxins associated with gram - or gram + outer membranes?
Gram negative
Does C. perf produce endotoxins, exotoxins, and/or enterotixins?
Exotoxins/enterotoxins
Which bacteria are microaerophilic?
Lawsonia intracellularis, camplytobacter spp.
Which bacteria are zoonotic?
Salmonella spp, Campylobacter spp.
Which bacteria can cause enterotoxemia?
STEC and C. perf Type D
C. perf Type A with NetF toxin is associated with what disease?
hemorrhagic enteritis in foals and dogs
What species does C. perf type A affect?
Bovine (calves)
What species does C. perf type C affect?
Neonate Ag Animals
What species does C. perf type D affect?
Ovine, goats
What spescies deos C. perf type G affect?
Avian
What C. perf types produce alpha toxin?
all types have alpha toxin
What disease is associated with C. perf Type C?
Neonatal hemorrhagic and necrotizing enteritis
What disease(s) is associated with C. perf Type D?
Ovine enterotoxemia,
enterotemia and enterocolitis in goats
What disease is C. perf Type G associated with?
Avian necrotic enteritis
Species/age associated with ETEC
Neonates, first 2-3 days of life
Species/age associated with STEC
pigs around 4 weeks of age
Species/age associated with Salmonella spp?
Lots of species, any age
Species/age associated with Lawsonia intracellularis
pigs, weaning foals
Age/species associated with C. perf?
Ag animals and occasionally foals within the 1st month of life
species associated with brachyspira spp?
grower/finisher pigs
What type of culture do you need for Brachyspira spp?
Anaerobic culture
What type of culture do you need for C. perf
Anaerobic culture
What type of culture do you need for A. bovis?
Anaerobic culture
What type of culture do you need for a facultative anaerobe?
Aerobic
which bacteria does not effect the intestinal wall
ETEC
ETEC produces what type of diarrhea?
watery diarrhea (no blood)
Salmonella spp. produces what type of diarrhea?
Inflammatory diarrhea (+/- blood)
Lawsonia intracellularis produces what type of diarrhea?
malabsorptive diarrhea (+/- blood)
C. perf produces what type of diarrhea?
severe hemorrhagic diarrhea
Brachyspira spp. produces what type of diarrhea?
Malabsorptive diarrhea (mucoid to mucohemorrhagic)
What is the toxic E.coli honorable mention that we learned?
EHEC
What are the non-toxic E.coli honorable mention that we learned?
AIEC, EPEC
E. coli EHEC is associated with…
production of attaching and effacing lesions, AND produces shiga-like toxins. Causes Dz in humans (Adult cattle are the reservoir)
E. coli AIEC is associated with…
canine granulomatous colitis. Primarily affects boxers and bulldogs. Causes a malabsortive inflammatory diarrhea (+/- blood)
E. coli EPEC is associated with….
characteristic attaching and effacing lesions. Causes malabsorptive diarrhea. Occurs in most species.
Most enterotoxins of C. perf are carried on..?
plasmids (not alpha)
