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Bacteriology Labs > Lab 5 - enterobactericeae general and the lactose+ genera > Flashcards

Lab 5 - enterobactericeae general and the lactose+ genera Flashcards

1
Q

The general characteristics of Enterobacteriaceae - habitat

A

Gut, environment, normal gut flora. When excreted in the faeces it gets into environment.

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2
Q

The general characteristics of Enterobacteriaceae - pathogenicity

A

There are Obligate pathogenic -and facultative pathogenic, but most of the enterobacteriaceae are saprophytes which sometimes gives benefits for the host:

  • Inhibit growth of unwanted pathogens.
  • Produce vitamins.
  • Help in digestion, some bacteria contains enzymes which the host has not.
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3
Q

The general characteristics of Enterobacteriaceae - Morphology

A
  • 1-3 μm rod (mid-sized), flagella (except: Shigella, Klebsiella - diagnostic tool!).
  • Some have a capsule and fimbria.
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4
Q

The general characteristics of Enterobacteriaceae - Staining

A

Gram negative

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5
Q

The general characteristics of Enterobacteriaceae - Culture/ environment

A

Grow on nutrient agar and on MacConkey
agar

aerobic, facultative anaerobic, 10-45 (37, body!) oC. Wide temperature range where propagation is possible. 1 day to produce colony.

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6
Q

The general characteristics of Enterobacteriaceae - describe why the selective and differential media are used with examples

A

not festidious! Sample often contain a lot of bacteria and they can be hard to identify and separate from each other. Differentiation is mainly due to lactose fermentation.

  • Selective enrichment: → Salmonella
  • Combined media, can examine many features of bacteria at the same time. Mainly used in food hygiene and not in clinical diagnostics.
  • Chromogenic media, media containing chemicals. When a biological reaction occur it changes color.
  • Rambach agar (fermentation of propylene glycol): Salmonella
  • Chromocult coliform agar to differentiate btw coliform and E. coli.
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7
Q

The general characteristics of Enterobacteriaceae - decribe how the different selectivity capacities are used for different bacteria

A

All these media contains lactose, indicator and inhibitory materials, and are used to propegate only certain bacteria by using different selectivity levels of the medium:
Low selective capacity, Medium selective capacity, High selective capacity:

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8
Q

Low selective capacity medium of enterobacteriaceae

A
  • All kind of eneterobacteria and some Gram+ spp can propagate.
  • Crystal violet(inhib gram+) – lactose (fermentation)- litmus(detects acid prod from lactose ferm) (oldest!: Drigalski)
  • Crystal violet – bile salts(inhib gram+)– lactose – neutral red (MacConkey) E.coli red, salmonella no color
  • Eosin – lactose – methylene blue
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9
Q

Medium selective capacity medium of enterobacteriaceae

A

Not all genera of enterobacterium can propagate, only the most important.

  • Brillantgreen (inhib gram+)– lactose – phenol red. Escherchia(yellow in acidic) and Salmonella.
  • Deoxycholate-citrate – lactose – neutral red (DC). Shigella, eifferentiation of different e. Coli
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10
Q

High selective capacity medium of enterobacteriaceae

A

Designed for isolation of salmonella. - Bismuth-sulphite agar

Bc salmonella is zoonotic, widespread, and cause many different diseases!

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11
Q

The general characteristics of Enterobacteriaceae: Biochemistry

A

Catalase +
!!oxidase -
!!fermentative (acid + gas production)(differentiate btw lactose + & -)

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12
Q

The general characteristics of Enterobacteriaceae: Antigens

A

Important since the bacteria are so widespread. The antigen is important for differentiation.
There are four types:
O: cell wall, lipopolysacch, unique for gram-
K: capsule, sometimes a virulence factor! Serotyping
H: flagella (Not Shigella or Klebsiella)
F: fimbria (generally involved in pathogenicity) tube on surface - virulence factor

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13
Q

The general characteristics of Enterobacteriaceae:

A

Medium - average resistance.

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14
Q

The general characteristics of Enterobacteriaceae: Grouping

A

Genus: biochemical characteristics

Species: biochemical and serological characteristics (antigen characteristics).

Serogroups (cell wall antigens): O antigens

Serotype (determined when we know all antigens present): O-K-H-F antigens

Biotypes: fermentation pattern

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15
Q

Escherichia coli habitat

A

Gut, aerobic, facultative anaerobic gut flora, mucous membranes.

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16
Q

Escherichia coli Morphology

A

2-3 μm rod, capsule (some, especially E.coli from cattle), flagella, fimbria - virulence factor!

17
Q

Escherichia coli Staining

A

Gram negative

18
Q

Escherichia coli Culture

A
  • As Enterobacteriaceae, simple nutrient agar or broth.
  • Capsulated culture (calf strain),
  • beta Haemolysis (swine), swine strains, independent from what disease they are collected.
  • Colonies appear within a day.
  • acidic pH - lactose+
19
Q

Escherichia coli biochemistry

A

Lactose +, indol +

Indol positive means that bacteria are able to produce indol from tryptophane.

20
Q

Escherichia coli antigens

A
  • All four types are present in E. coli.
    O: type specific (174 types). Type specific = one bacteria has a single O-antigen.
    K: heat stabile (A) and heat labile (L): 80 types
    F: 19 types. F-type is important since it is in strong correlation with the caused disease. H: 57 types, one antigen in one bacterium.
21
Q

Escherichia coli Resistance

A

Medium

22
Q

Escherichia coli Pathogenicity

A

Saprophyte - facultative pathogenic (small fraction)

23
Q

Pathogenic E. coli strains

A
  • Enteropathogenic strains. Intimin, protein on surface of bacteria, attaches to enterocytes of mucous membranes and destroy the cells.
  • Enterotoxigenic strains, adhesive factors, enterotoxin. Peptides which change the function of the enterocytes. Instead of absorbing water and nutritions they excrete diarrhea.
  • Verotoxigenic strains (VT1, VT2), verotoxins, inhibit protein synthesis and attack endocells. - Necrotoxic (cytotoxic necrotic factor producing) strains, attack the epithelia cells of the gut. - Enteroinvasive strains (Hu): Shigella
  • Enteroadhesive-aggregative strains: Hu
  • Septikaemic strains
24
Q

Klebsiella
K. pneumoniae
Habitat:

A

Gut, respiratory way, genital tract, environment, mucous membranes.

Gut, resp, spread by mucous memb.>gen tract> shed to environment

25
Q

Klebsiella

K. pneumoniae Morphology

A
  • Rod
  • Capsule, very thick! Good protection, white
  • No flagellum
26
Q

Klebsiella

K. pneumoniae Culture

A
  • Large, merging, mucoid colonies, single colonies are hard to see due to the extensive capsule.
  • Rapid change of the colour of the indicator due to fast metabolism. If they are allowed to grow for a long time they will ferment all the Lactose and start to degrade the acids produced, when all the acids are degraded the pH will increase. As the acid decr. It looks lactose negative after a while
27
Q

Klebsiella

K. pneumoniae Biochemistry

A

Lactose +

28
Q

Klebsiella

K. pneumoniae Antigens

A

82 serogroups (capsule), correlated with the diseases. Virulence factors

29
Q

Klebsiella

K. pneumoniae Pathogenicity

A
  • Saprophytic (most)

- Facultative pathogenic:

30
Q

ENTEROBACTER habitat

A

gut (part of normal flora), environment (shed)

31
Q

ENTEROBACTER morph

A
  • rod
  • capsule, large
  • flagella

Bacteriology Labs (4 decks)

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