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Enterobacteriacae Flashcards

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
Q

Enteropathogenic E.coli

A

watery diarrhea

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26
Q

Shigella causes what? Symptoms?

A
  • Shigellosis
  • Dysentery
  • Abdominal pain, fever, diarrhea
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27
Q

Shigella most severe in what populations?

A

Children and elderly
Outbreaks common in daycare centers and nursing homes

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28
Q

How pathogenic is Shigella?

A

Highly pathogenic
Less than 50 bacteria can cause disease

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29
Q

Infection route of Shigella

A

Fecal-oral
food poisoning

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30
Q

Name the corresponding Shigella organism of serogroup A and describe

A
  • S. dysenteriae
  • Makes enterotoxin and neurotoxin that may result in paralysis
  • Mannitol and ONPG neg
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31
Q

Name the corresponding Shigella organism of serogroup B and describe

A
  • S. flexneri
  • mild diarrhea
  • mannitol pos and ONPG neg
  • difficult to differ from S. boydii
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32
Q

Name the corresponding Shigella organism of serogroup C and describe

A
  • S. boydii
  • mild diarrhea
  • mannitol pos and ONPG neg
  • difficult to differ from S. flexneri
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33
Q

Name the corresponding Shigella organism of serogroup D and describe

A
  • S. sonnei
  • mild diarrhea
  • most common cause of shigellosis in USA
  • mannitol and ONPG pos
  • delayed lactose fermenter
34
Q

Klebsiella causes what?

A

UTIs and pneumonia

35
Q

Which populations are most prone to Klebsiella infections?

A

Alcoholics and diabetics

36
Q

Most common Klebsiella organism

A

K. pneumoniae

37
Q

Identifying characteristics of Klebsiella pneumoniae
TSI
MAC
H2S
Methyl Red
Motility
Indole

A
  • TSI: A/A with gas
  • MAC: pink and very mucoid due to capsule production
  • H2S: neg
  • MR: neg
  • Nonmotile
  • Indole neg
38
Q

Which Klebsiella species are indole pos?

A

K. oxytoca
K. ornithinolytica

39
Q

Klebsiella granulomatis

A
  • causes granuloma inguinale
  • STD
40
Q

How to ID K. granulomatis?

A
  • does not gram stain or grow on lab media
  • Donovan bodies may be seen
41
Q

Donovan bodies

A

intracellular pleomorphic bipolar staining bacteria

42
Q

Enterobacter found where?

A
  • soil
  • water
  • dairy products
43
Q

Most common and second most common Enterobacter speciess

A
  1. E. cloacae
  2. E. aerogenes
44
Q

Enterobacter spp. are occasional clinical isolates that have been linked to what?

A

Respiratory tract infections
Wounds
Blood

45
Q

Identifying characteristics of Enterobacter
H2S, MR, and indole
VP and citrate
lactose fermenting

A
  • H2S, MR, and indole negative
  • VP and citrate positive
  • All are lactose fermenters except for E. taylorae
46
Q

Arginine and lysine metabolism of E. cloacae and E. aerogenes

A
  • E. cloacae: arginine pos and lysine neg
  • E. aerogenes: arginine neg and lysine pos
47
Q

How to uniquely ID E. sakazakki?

A

Yellow pigment

48
Q

Serratia causes what kind of infection in what patient populations?

A

Opportunistic infections in patients undergoing chemo and immunosuppressed pt

49
Q

Most common Serratia clinical isolate

A

S. marcescens

50
Q

S. marcescens identifying characteristics
DNase, gelatinase, lipase
VP and citrate
ONPG
lactose fermentation
pigment

A
  • 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
Q

Name both Salmonella species

A

S. enterica
S. bongori

52
Q

S. typhi is the serotype under which Salmonella species?

A

S. enterica

53
Q

Salmonella reservoir

A

Many animal reservoirs

54
Q

Salmonella transmission route

A

Contaminated water
Undercooked food, esp chicken

55
Q

Most severe form of salmonellosis

A
  • typhoid fever caused by S. typhi
  • septicemia followed by GIT infection
56
Q

Salmonella isolated from stool biochemical tests for lactose and H2S on enteric media

A
  • Lactose neg
  • H2S pos
57
Q

Salmonella identifying characteristics
H2S, motility, citrate
indole, urease, lactose
HE agar

A
  • H2S, motility, citrate pos
  • indole, urease, and lactose pos
  • HE colonies are green with black centers
58
Q

Proteus most common isolates

A

P. vulgaris
P. mirabilis

59
Q

Proteus mirabilis identifying characteristics
H2S
Motility
Indole

A
  • H2S pos
  • swarming motility on SBA
  • indole neg
60
Q

Proteus vulgaris identifying characteristics
H2S
Motility
Indole

A
  • H2S pos
  • swarming motility on SBA
  • indole pos
61
Q

All proteus species are urease, tryptophan deaminase (TDA), and phenylalanine deaminase (PDA) ______

62
Q

All proteus are ONPG and lactose ____

63
Q

Name the 3 pathogenic spp. of Yersinia

A
  1. Y. pestis
  2. Y. enterocolitica
  3. Y. pseudotuberculosis
64
Q

Describe Y. pestis
disease association
endemic where
transmission
reservoirs
gov’t status

A
  • plague
  • southwestern USA
  • fleas transmit it
  • rodents and other small animal reservoirs
  • potential bioterrorism agent
65
Q

Describe Y. enterocolitica
disease association
transmission
ONPG result
lactose and sucrose fermentation
TSI

A
  • enterocolitis
  • contaminated water or meat
  • ONPG pos
  • delayed lactose fermenter and sucrose pos (MAC colorless at 18 hr)
  • TSI is A/A
66
Q

Y. pseudotuberculosis disease association in what population?

A

Lymphadenitis in kids

67
Q

Yersinia morphology

A

small coccobacilli

68
Q

Selective medium for Yersinia enterocolitica

A

cerfsulodin-irgassan-novobiocin (CIN) medium

69
Q

Yersinia colonies ferment what sugar and absorb what dye? What do the colonies look like?

A
  • ferment mannitol
  • absorb neutral red
  • clear colonies with pink center
70
Q

Yersinia motility

A

All spp. are nonmotile at 37°C but motile at 25°C
except Y. pestis

71
Q

Presumptive ID of Y. pestis
isolated from which body part
SBA colonies
Gram stain/morphology
Oxidase and urease
Catalase
Growth temp

A
  • 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
Q

Edwardsiella most common isolate

73
Q

Edwardsiella resembles which organism biochemically?

A

Salmonella
H2S pos
ONPG neg

74
Q

E. tarda indole and citrate results opposite from Salmonella how?

A

indole pos
citrate neg

75
Q

Citrobacter most common isolate

A

C. freundii

76
Q

C. freundii resembles ____ on MAC

77
Q

How to differentiate C. freundii from E.coli?

A

C. freundii is H2S pos
indole neg

78
Q

Morganella only species

A

M. morganii

79
Q

Morganella
indole, VP, citrate
PDA and TDA

A
  • indole pos
  • VP and citrate neg
  • PDA and TDA pos
80
Q

Providencia most common isolate

A

P. rettgeri

81
Q

Providencia
PDA and TDA
indole and citrate
VP

A
  • PDA and TDA pos
  • indole and citrate pos
  • VP neg

BOC Microbiology (7 decks)

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