BOC Microbiology > Enterobacteriacae > Flashcards

Enterobacteriacae Flashcards

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1
Q

All Enterobacteriacae show what gram stain and morphology?

A

Gram-neg bacilli

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2
Q

What are the common biochemical traits of all Enterobacteriacae?

A
  • Oxidase neg
  • Catalase pos
  • Reduce nitrate to nitrite
  • Facultative anaerobe
  • Ferment glucose
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3
Q

Most medically relevant family of GNB?

A

Enterobacteriacae

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4
Q

Enterobacteriacae associated diseases

A
  • UTIs
  • gastroenteritis
  • septicemia
  • food poisoning
  • wound infections
  • peritonitis
  • pneumonia
  • meningitis
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5
Q

What are the 4 antigens that contribute to Enterobacteriacae serological characteristics?

A
  • O (Somatic) Ag for cell wall
  • K (envelope) Ag for capsule
  • H (flagellar) Ag
  • Vi Ag
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6
Q

Capsular antigen of Salmonella typhi

A

Vi Ag

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7
Q

Heat stabilities of O, K, H, and Vi Ag

A

Heat stable = O
Heat labile = K, H, Vi

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8
Q

List enteric media

A
  • MAC
  • Eosin-methylene blue (EMB)
  • Hektoen enteric (HE) agar
  • Xylose-lysine-desoxycholate (XLD) agar
  • Salmonella-Shigella (SS) agar
  • Bismuth sulfite agar
  • Brilliant green agar
  • Selenite broth
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9
Q

MAC agar interpretation

A
  • pink/red = lactose fermenters
  • colorless = non-lactose fermenters
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10
Q

EMB agar interpretation

A
  • colony with dark center = lactose fermenter
  • colorless colony = non-lactose fermenter
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11
Q

HE agar interpretation

A
  • yellow/orange = lactose and/or sucrose fermenters
  • green = H2S neg, Shigella
  • green with black center = H2S positive, Salmonella
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12
Q

XLD agar interpretation

A
  • yellow = lactose and/or sucrose fermenter
  • red with black center = Salmonella
  • clear = Shigella
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13
Q

SS agar interpretation

A
  • red = lactose fermenters
  • colorless with black center = Salmonella
  • colorless = Shigella
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14
Q

Bismuth sulfite agar interpretation

A
  • black = Salmonella typhi
  • yellow-orange = lactose fermenters
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15
Q

Brilliant green agar interpretation

A
  • red/pink = Proteus and Salmonella
  • no growth = Shigella and most lactose fermenters
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16
Q

Selenite broth interpretation
uncommon enhancement medium for stool cultures

A
  • Salmonella enhanced
  • normal GI flora are inhibited
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17
Q

Escherichia associated diseases

A

UTIs
appendicitis
peritonitis
gallbladder infections
endocarditis
meningitis in newborns
gasteroenteritis
food poisoning

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18
Q

Identifying traits of Escherichia
TSI slant
MAC
SBA sheep blood agar
EMB
Indole, methyl red, motility, ONPG
VP, citrate, and urease

A
  • TSI slant: A/A and H2S neg
  • MAC: pink/red colonies
  • SBA: shiny, opaque, off-white, beta-hemolytic
  • EMB: green metallic sheen with dark center
  • Indole, methyl red, motility, ONPG positive
  • VP, citrate, and urease negative
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19
Q

Enterohemorrhagic E.coli (EHEC) causes what?

A

Hemorrhagic colitis and HUS, leading to kidney failure in kids

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20
Q

How is EHEC acquired? Mechanism?

A
  • Acquired by eating undercooked hamburger or other contaminated foods such as apple cider, basil, sprouts…etc
  • Mechanism: Shiga toxin 1 and 2 virulence factors (E.coli O157:H7)
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21
Q

How to isolate and ID E.coli O157:H7?

A
  • sorbitol MAC
  • E.coli O157:H7 does not metabolize sorbitol -> colorless colonies
  • other E.coli strains produce pink colonies
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22
Q

List all 4 strains of E.coli that cause human intestinal infections

A
  1. Enterohemorrhagic
  2. Enterotoxigenic
  3. Enteroinvasive
  4. Enteropathogenic
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23
Q

Enterotoxigenic E.coli

A

severe epidemic diarrhea due to contaminated water

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24
Q

Enteroinvasive E.coli

A

bloody diarrhea by invading intestinal epithelium

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25
Enteropathogenic E.coli
watery diarrhea
26
Shigella causes what? Symptoms?
- Shigellosis - Dysentery - Abdominal pain, fever, diarrhea
27
Shigella most severe in what populations?
Children and elderly Outbreaks common in daycare centers and nursing homes
28
How pathogenic is Shigella?
Highly pathogenic Less than 50 bacteria can cause disease
29
Infection route of Shigella
Fecal-oral food poisoning
30
Name the corresponding Shigella organism of serogroup A and describe
- S. dysenteriae - Makes enterotoxin and neurotoxin that may result in paralysis - Mannitol and ONPG neg
31
Name the corresponding Shigella organism of serogroup B and describe
- S. flexneri - mild diarrhea - mannitol pos and ONPG neg - difficult to differ from S. boydii
32
Name the corresponding Shigella organism of serogroup C and describe
- S. boydii - mild diarrhea - mannitol pos and ONPG neg - difficult to differ from S. flexneri
33
Name the corresponding Shigella organism of serogroup D and describe
- S. sonnei - mild diarrhea - most common cause of shigellosis in USA - mannitol and ONPG pos - delayed lactose fermenter
34
Klebsiella causes what?
UTIs and pneumonia
35
Which populations are most prone to Klebsiella infections?
Alcoholics and diabetics
36
Most common Klebsiella organism
K. pneumoniae
37
Identifying characteristics of Klebsiella pneumoniae **TSI** **MAC** **H2S** **Methyl Red** **Motility** **Indole**
- TSI: A/A with gas - MAC: pink and very mucoid due to capsule production - H2S: neg - MR: neg - Nonmotile - Indole neg
38
Which Klebsiella species are indole pos?
K. oxytoca K. ornithinolytica
39
Klebsiella granulomatis
- causes granuloma inguinale - STD
40
How to ID K. granulomatis?
- does not gram stain or grow on lab media - Donovan bodies may be seen
41
Donovan bodies
intracellular pleomorphic bipolar staining bacteria
42
Enterobacter found where?
- soil - water - dairy products
43
Most common and second most common Enterobacter speciess
1. E. cloacae 2. E. aerogenes
44
Enterobacter spp. are occasional clinical isolates that have been linked to what?
Respiratory tract infections Wounds Blood
45
Identifying characteristics of Enterobacter **H2S, MR, and indole** **VP and citrate** **lactose fermenting**
- H2S, MR, and indole negative - VP and citrate positive - All are lactose fermenters *except* for E. taylorae
46
Arginine and lysine metabolism of E. cloacae and E. aerogenes
- **E. cloacae**: arginine pos and lysine neg - **E. aerogenes**: arginine neg and lysine pos
47
How to uniquely ID E. sakazakki?
Yellow pigment
48
Serratia causes what kind of infection in what patient populations?
Opportunistic infections in patients undergoing chemo and immunosuppressed pt
49
Most common Serratia clinical isolate
S. marcescens
50
S. marcescens identifying characteristics **DNase, gelatinase, lipase** **VP and citrate** **ONPG** **lactose fermentation** **pigment**
- DNase, gelatinase, lipase pos - VP and citrate pos - ONPG pos - delayed lactose fermenter - some strains make red pigment, which is enhanced upon room temp inc
51
Name both Salmonella species
S. enterica S. bongori
52
S. typhi is the serotype under which Salmonella species?
S. enterica
53
Salmonella reservoir
Many animal reservoirs
54
Salmonella transmission route
Contaminated water Undercooked food, esp chicken
55
Most severe form of salmonellosis
- typhoid fever caused by S. typhi - septicemia followed by GIT infection
56
Salmonella isolated from stool biochemical tests for lactose and H2S on enteric media
- Lactose neg - H2S pos
57
Salmonella identifying characteristics **H2S, motility, citrate** **indole, urease, lactose** **HE agar**
- H2S, motility, citrate pos - indole, urease, and lactose pos - HE colonies are green with black centers
58
Proteus most common isolates
P. vulgaris P. mirabilis
59
Proteus mirabilis identifying characteristics **H2S** **Motility** **Indole**
- H2S pos - swarming motility on SBA - indole neg
60
Proteus vulgaris identifying characteristics **H2S** **Motility** **Indole**
- H2S pos - swarming motility on SBA - indole pos
61
All proteus species are urease, tryptophan deaminase (TDA), and phenylalanine deaminase (PDA) ______
Positive
62
All proteus are ONPG and lactose ____
Negative
63
Name the 3 pathogenic spp. of Yersinia
1. Y. pestis 2. Y. enterocolitica 3. Y. pseudotuberculosis
64
Describe Y. pestis **disease association** **endemic where** **transmission** **reservoirs** **gov't status**
- plague - southwestern USA - fleas transmit it - rodents and other small animal reservoirs - potential bioterrorism agent
65
Describe Y. enterocolitica **disease association** **transmission** **ONPG result** **lactose and sucrose fermentation** **TSI**
- enterocolitis - contaminated water or meat - ONPG pos - delayed lactose fermenter and sucrose pos (MAC colorless at 18 hr) - TSI is A/A
66
Y. pseudotuberculosis disease association in what population?
Lymphadenitis in kids
67
Yersinia morphology
small coccobacilli
68
Selective medium for Yersinia enterocolitica
cerfsulodin-irgassan-novobiocin (CIN) medium
69
Yersinia colonies ferment what sugar and absorb what dye? What do the colonies look like?
- ferment mannitol - absorb neutral red - clear colonies with pink center
70
Yersinia motility
All spp. are nonmotile at 37°C but motile at 25°C *except Y. pestis*
71
Presumptive ID of Y. pestis **isolated from which body part** **SBA colonies** **Gram stain/morphology** **Oxidase and urease** **Catalase** **Growth temp**
- isolation from resp tract, blood, or lymph nodes - pinpoint colonies - GNB - oxidase and urease neg - catalase pos - growth may be better at 28°C than 35°C
72
Edwardsiella most common isolate
E. tarda
73
Edwardsiella resembles which organism biochemically?
Salmonella H2S pos ONPG neg
74
E. tarda indole and citrate results opposite from Salmonella how?
indole pos citrate neg
75
Citrobacter most common isolate
C. freundii
76
C. freundii resembles ____ on MAC
E. coli
77
How to differentiate C. freundii from E.coli?
C. freundii is H2S pos indole neg
78
Morganella only species
M. morganii
79
Morganella **indole, VP, citrate** **PDA and TDA**
- indole pos - VP and citrate neg - PDA and TDA pos
80
Providencia most common isolate
P. rettgeri
81
Providencia **PDA and TDA** **indole and citrate** **VP**
- PDA and TDA pos - indole and citrate pos - VP neg
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