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LAB 6 Flashcards

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1
Q

What is the incidence of salmonellosis gastroenteritis

A

An estimated 1.35 million cases occur annually
- 26,500 result in hospitalization
- 420 result in death

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2
Q

symptoms of salmonellosis gastro

A
  • Abdominal pain
  • Cramps
  • Diarrhea
  • Nausea
  • Vomiting
  • Fever
  • Dehydration
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3
Q

metagenomics def

A

The study of microbial genomes based on DNA extracted directly from the environment, it samples the entire pool of nucleic acids found in any given ecosystem and most frequently used to determine the members of the microbial community living there

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4
Q

metatranscriptomics def

A

mRNA extracted from the natural environment is reverse transcribed to cDNA and directly analyzed by next generation sequencing

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5
Q

what is the incidence of nasal carriage of s.aureus in the MICR221 class

A

31%

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6
Q

results of TSA

A

Enteroccus faecalis
escherichia coli
salmonella typhimurium
shigella sonnei
All had:
- 0.5 mm
- raised
- circular
- entire
- cream
- smooth

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7
Q

hektoen agar

A
  • an example of selective and differential medium used for the isolation and cultivation of gram-negative enteric microorganisms
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8
Q

Enterococcus faecalis hektoen agar results

A

growth = complete inhibition

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9
Q

Escherichia coli hektoen agar results

A

growth = partially inhibited
colony morphology = orange-red, smooth, raised

agar colour = orange

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10
Q

salmonella typhimurium hektoen agar results

A

growth = good
colony morphology = 2-4mm, clear, green/blue, moist, raised, black centres
agar colour = blue/green

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11
Q

shigella sonnei

A

growth = good
colony morphology = 2-3mm, clear, green/blue, moist, flat, transparent
agar colour = blue/green

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12
Q

selective components in hektoen agar

A

bile salts

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13
Q

which group of bacteria is hektoen agar selective for

A

enteric bacteria

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14
Q

differential components in hektoen agar

A

Lactose
Sucrose
Salicin
Acid fuchsin
Bromothyl blue
Ferric ammonium citrate
Sodium thiosulfate

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15
Q

how does hektoen agar differentiate between the groups of bacteria

A

Salmonella produce hydrogen sulfide producing black colonies, other enteric bacteria (including Shigella) do not

Salmonella and Shigella do not ferment any of the three carbohydrates (lactose, sucrose or salicin) so the agar colour stays the same (blue/green), unlike other enteric bacteria (salmon orange-red)

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16
Q

which enzyme must bacteria have in order to grow in tetrathionate broth

A

tetrathionate reductase

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17
Q

why does salmonella need to be incubated on an enrichment broth

A
  • because it is present in such small numbers it may be impossible to recover
  • the tetrathionate broth allows the salmonella to multiply and also suppresses growth of the normal faecal microflora
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18
Q

results of enriching salmonella

A

Primary culture (inoculated with a faecal sample):
colony morphology:
- orange colour
- smooth
- raised
agar colour:
- orange + may be a precipitate

Enrichment subculture:
colony morphology:
- 2-4mm
- clear
- green
- moist
- raised
- black centres
agar colour:
- mostly green/yellow

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19
Q

estimate for what the bacteria growing on the primary culture plate in the enrichment of salmonella is

A

E.coli

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20
Q

estimate for what the bacteria growing on the enrichment culture plate in the enrichment of salmonella is

A

Salmonella typhimurium

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21
Q

triple sugar iron agar

A
  • differential but not selective
  • useful in screening isolates of enteric bacteria
  • contains three carbs:
    -> glucose
    -> lactose
    -> sucrose
  • also contains
  • ferrous ions
  • pH indicator phenol red
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22
Q

what are the four reactions that can be recorded from each tube in the triple sugar ion agar

A
  • colour of the butt
  • colour of the slant
  • production of gas
  • production of hydrogen sulfide
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23
Q

what are the possible outcomes of the triple sugar iron agar

Study These Flashcards
A
  1. Acid reaction (yellow colour) = indicates the ability of the bacteria to ferment one or more of the carb components of the medium
  2. Alkaline reaction (deep red colour) = indicates the aerobic utilisation of organic acids by enteric bacteria when the fermentable substrates have been utilised
  3. sulfide produced by the bacteria reacts with ferrous ions in the medium producing insoluble ferrous sulfide (black)
  4. gas production can be recorded as positive if gas bubbles in the agar or at the base of the tube are observed
24
Q

triple sugar iron agar test results

Study These Flashcards
A

Escherichia coli:
slant = yellow
butt = yellow
gas = yes
H2S = no
Proteus mirabilis:
slant = red
butt = yellow
gas = yes
H2S =yes
Salmonella:
slant = red
butt = yellow
gas = yes
H2S =either
shigella sonnei:
slant = red
butt = yellow
gas = no
H2S =no

25
what organisms could be confused using TSI slants
Proteus mirabilis and Salmonella
26
urease test
- used when organisms cannot be differentiated by TSI slants - differential - used to test the ability of an organism to produce the exo-enzyme, urease - urease breaks the carbon-nitrogen bond of amides to form CO2, ammonia and water Contains two buffers, urea, a very small amount of nutrients for the bacteria, agar, and the pH indicator phenol red --> if the urea in the slant is degraded and ammonia is produced, an alkaline environment is created and the media turns pink
27
results of the urease test
proteus mirabilis = pink = alkaline (contains urease) salmonella = yellow = acidic (no urease)
28
carcinogenic
having the potential to cause cancer
29
colony morphology of the enteric bacteria
E.coli & S.typhimurium - gram negative - regular staining - rods - singles - 2um - regular form - straight rod axis --> therefore they can't be differentiated from the gram stain alone
30
serotype
a way of grouping cells based on the antigens or other molecules found on their surface
31
identification of Salmonella species
- a serotype is determined by the somatic (O) and flagella (H) antigens in the cell wall of Salmonella
32
nomenclature for identification of salmonella species
- in antigenic formulae the O is listed first then the H - major antigens are separated by colons and the components of an antigen (serofactors) are separated by commas eg: 4,5,12: j: 1, 2
33
the slide agglutination test
- a rapid diagnostic test for typhoid fever - rapid results - used to test unknown organisms against known antisera positive result = clumping
34
antisera
a blood serum containing antibodies
35
the slide agglutination test procedure
1. Place one 10 µL drop of the killed Salmonella isolate culture at each end of a microscope slide. 2. Add 10 µL of O antiserum 4 to one drop. 3. Add 10 µL of O antiserum 9 to the other. 4. Mix the drops by gently 'rocking' the slide. The drops need to stay separate so do not be too vigorous. Repeat steps 1 - 4 using a fresh slide with H antigen 1 and H antigen 5.
36
what was the outcome of the slide agglutination test
typhimurium
37
what is the gram reaction of C.difficile
gram positive
38
what causes the symptoms of pseudomembranous colitis
--> Toxin A and Toxin B - the disease is not an infection as such, but rather an overgrowth of Cl. difficile in the bowel - this is due to the prior antibiotic therapy removing elements of the normal microflora, which usually keep this organism under control
39
what types of antibiotics are most often associated with this condition?
- ampicillin - cephalosporins - clindamycin - amoxicillin - fluoroquinolone
40
where is the largest bacterial community inhaibting the human body found
in the large intestine
41
polymerase chain reaction (PCR)
- DNA or RNA is extracted directly from intestinal or faecal samples - then the hypervariable 16S rRNA sequences are amplified using PCR primers that anneal with the conserved sequences that span selected V regions - to seperate the components 16S fragments in the PCR product, a polyacrylamide gel is used - The double-stranded 16S fragments migrate through a polyacrylamide gel containing a gradient of urea and formamide until they are partially denatured by the chemical conditions - Due to the variation in the 16S sequences of different bacterial species, different 16S 'species' can be differentiated by this electrophoretic method.
42
what prevents denaturation of the DNA gramgents during gel electrophoresis
a GC-right 5' end
43
which group of bacteria predominate in babies and why is this so?
Bifidobacteria - the carbohydrate in breast milk (Bifidus factor) favours their growth
44
which group of bacteria predominate in adults and why is this so?
Clostridium - due to diet, bifidobacteria are in the minority in the adult gut
45
aim of the human microbiome project
has the goal of identifying and characterizing the microorganisms which are found in association with both healthy and diseased humans
46
what were the two sites that the researchers noted as being "especially diverse in terms of community membership"
- oral and stool sites
47
What is the site that the researchers noted as “harbouring particularly simple communities”?
vaginal sites
48
name the dominant taxa in the oral cavity
streptococcus
49
what were the percentage of S. aureus and S. epidermis found on participants skin and nasal samples
Skin Nasal S. aureus 4% 29% S. epidermidis 100% 93%
50
thermal death point (TDP)
the lowest temp required to kill all bacteria in a sample within a period of 10mins
51
thermal death time
the length of time required to kill all bacteria in a sample at a given temp
52
decimal reduction time
the time taken to obtain a 10-fold reduction in the number of bacteria
53
bacillus subtilis thermal death point
100 degrees
54
escherichia coli thermal death point
70 degrees
55
why does B. subtilis have a higher thermal death point
B. subtilis is more heat resistant as it forms endospores
56

MICR221 (19 decks)

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