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Carbohyrdrates and Microbiology :) > Enterobacteriaceae Opportunistic Pathogens > Flashcards

Enterobacteriaceae Opportunistic Pathogens Flashcards

1
Q

What are the GENERAL characteristics of Enterobacteriaceae?

A
  • Gram negative bacilli
  • Non-spore forming
  • All ferment glucose
  • Catalase pos (except Shigella dysenteriae)
  • Oxidase neg (except Plesiamonas sp.)
  • Most reduce nitrate to nitrite (ones causing human infections)
  • Peritrichous flagella if motile
  • All grow on BA and CHOC
  • Grow well at 35-37
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2
Q

Epidemiology of Enterobacteriaceae

A

E. coli : NF of bowel (human and animal), may inhabit female genital tract

Citrobacter spp, Enterobacter spp, Klebsiella spp, Morganella spp, Proteus spp, Providencia spp and Serratia spp: NF in human GIT

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3
Q

Their mode of transmission?

A
  • Often endogenous and opportunistic

- Person-to-person (often nosocomial)

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4
Q

Virulence factors include:

A

Endotoxins (fever, vasodilation, inflammation, shock, DIC), capsules, adhesion proteins, multiple antimicrobial resistances

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5
Q

These can cause what in these types of patients?

A

Nosocomial infections of RT, UT, blood and other sterile sites in hospitalized or debilitated patients

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6
Q

Virulence factors of E.coli causing extraintestinal infections

A

Endotoxins, pili, capsule

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7
Q

Enterotoxigenis E.coli (ETEC) and their virulence factors

A
  • Potent toxins (serious GI infections)

- Pili, enterotoxins

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8
Q

Enteroinvasive E.coli (EIEC) and their virulence factors

A
  • Invades enterocytes (serious GI infections)

- Similar mechanisms to Shigella

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9
Q

Enteroaggregative E.coli (EAEC) and their virulence factors

A
  • Attach to mucosal cells of GI and change cell surface (serious GI infections)
  • Pili, enterotoxins
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10
Q

Enterohemorrhagic E.coli (EHEC/VTEC/STEC) and their virulence factors

A
  • Toxin (life threatening systemic illness)

- SHIGA toxin

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11
Q

Colonial appearance on BA

A

Large, grey, smooth. glistening, moist, E.coli often B-hemolytic, Kleb + Enterbacter spp. may be mucoid, Proteus spp. often swarm

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12
Q

Gelatin Hydrolysis

A
  • Determines ability to produce gelatinase
    Procedure:
  • Stab 4-5 times, inc in 02 up to 14 days
  • Place in 4 degrees daily to check for liquification
  • Use uninoculated tube for control, ensure it gels
  • Pos= partial/total liquefaction @4deg (control solid)
  • Neg= solid at 4deg

Pos QC=Bacillus subtilis
Neg QC=E.coli

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13
Q

4-Methylumbelliferyl-β-D-Glucuronide (MUG) test

A
  • Rapid test to ID E.coli
  • Subsrate:4-Methylumbelliferyl-β-D-Glucuronide

Procedure:

  • Impreg substrate on paper disc
  • Inoc and inc in 2 hrs
  • Pos=electric blue fuorescence (E.coli)
  • Neg=no fluorescence (Kleb. pnuemoniae)

NOTE: only test oxidase-neg orgs

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14
Q

What are the categories of E.coli?

A

Uropathogenic (UPEC)
- Pathogenicity islands coding for adhesions and toxins

Meningitis/sepsis-asscosiated (MNEC)
- neonatal meningitis w/ high morbidity and mortality. Spread fr. blood

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15
Q

E.coli are:

A
  • Most are LF, dry (may see precip of bile salts on MAC
  • Indole pos
  • VP neg
  • Citrate neg
  • Lysine pos
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16
Q

Klebsiella spp. characteristics

A
  • Klebsiella pnuemoniae, Klebsiella oxytoca
  • NF in Nasopharynx and GIT
  • UTI, pneumonia, septicemia, liver abcesses
  • K.oxytoca: associated w/ self-limiting, antibiotic-associated hemorrhagic colitis
  • K.pneumoniae: intrinsically resistant to ampicillan
  • Possible multidrug resistance
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17
Q

Kleb spp. are:

A

Culture:
- Mucoid, Mac-LF &lrg

Tests

  • Non-motile
  • VP pos
  • Ornithine neg
  • Urea pos
18
Q

What test differentiates K.pnuemoniae and K.oxytoca?

A

Indole
K.pnuemoniae - neg
K.oxytoca - pos

19
Q

Enterobacter spp. is part of which tribe?

A

Klebsielleae

20
Q

NF and infections of Enterobacter spp.

A
  • NF in human GIT (also in soil and water)

- UTI, respiratory and cutaneous infections, nosocomial (contaminated medical devices

21
Q

Culture and tests of Enterobacter spp

A

Culture
- Mac: LF; often mucoid (capsule); may have plasmids

Tests

  • Motile
  • Ornithine pos
22
Q

Test that differentiates E.aerogenes from E.cloacae

A

Lysine
E.aerogenes = pos
E.cloasae = neg

23
Q

Serratia spp., name 2, what tribe are they a part of.

A

Serratia marcescens
Serratia liquifaciens

Tribe Klebsiella

24
Q

What can be caused by Serratia spp.?

A

UTI, pneumonia, septicemia, wound infections

Nosocomial opportunist

25
Q

What does Serratia marcescens look like in the lab?

A

Typically red, pigment prodogiosin (not all)

  • Motile
  • LLF
  • DNase pos
26
Q

Where can you find Citrobacter and how is it transmitted?

A
  • NF of the GIT

- Person to person transmission

27
Q

Infections caused by Citrobacter

A
  • UTI is most common

- Septicemia, meninitis, brain abscesses, neurological complications

28
Q

What does Citrobacter look like in the lab

A
  • LLF

- May have inducable AmpC genes=resistance to ampicillin etc

29
Q

Where is Proteus spp. found?

A
  • NF of GIT
  • UTI, wound and ear infection
  • vulgaris; infection in immunocomp’d, especially after antibiotics
30
Q

Describe Proteus in the lab

A
  • Swarming on non-inhibitory plates (most strains)
  • Distinct odour (chocolate cake
  • NLF
  • PDA pos
  • Urea pos
31
Q

Which tests differentiate P. mirabilis from P. vulgaris?

A

Indole:

  • P. mirabilis = neg
  • P. vulgaris = pos

Ornithine:

  • P. mirabilis = pos
  • P. vulgaris = neg
32
Q

Where do you find Morganella spp.

A
  • NF in GIT
  • UTI, wound infections?
  • Questionable clinical significance
33
Q

What does Morganella morganii look like in the lab

A
  • NLF
  • PDA pos
  • Urea pos
  • Citrate neg
  • Ornithine pos
  • Indole pos
  • H2S may be pos
34
Q

What does Providencia spp. look like in the lab

A
  • NLF
  • PDA pos
  • Citrate pos
  • Urea pos (P. rettgeri)
35
Q

Name the H2S producing:

A
  • Proteus mirabilis
  • Proteus vulgaris
  • Morganella morganii
  • Citrobacter freundii
36
Q

VP positive:

A

All except E. coli and Citrobacter freundii

37
Q

PDA pos:

A
  • Proteus spp.
  • Morganella morganii
  • Providencia spp.
38
Q

Non-motile and urea positive

A

Klebsiella spp.

39
Q

Only LF’s that are indole positive:

A
  • E. coli
  • Klebsiella oxytoca
  • Citrobacter Freundii
40
Q

Enteropathogenic E. coli (EPEC)

A
  • Can be chronic, attach to enterocytes in small bowel

Carbohyrdrates and Microbiology :) (7 decks)

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