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Enterobacteriaceae Flashcards

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1
Q

General characteristics of Enterobacteriaceae

A
  • ferment glucose
  • reduce nitrate to nitrites
  • oxidase negative
  • motile at body temperature
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2
Q

oxidase positive Enterobacteriaceae

A

Plesiomonas

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3
Q

Enterobacteriaceae that are non-motile at body temperature

A

Klebsiella, Shigella, Yersinia

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4
Q

Enterobacteriaceae colony morphology

A

Gram-negative rods, facultatively anaerobic, large moist gray colonies, some mucoid colonies

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5
Q

grow throughout thioglycolate broth tube

A

facultatively anaerobic Enterobacteriaceae

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6
Q

Enterobacteriaceae grow well on which agars?

A

MacConkey, EMB agar, HE agar, XLD agar

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7
Q
  • selective and differential media
  • bile salts and crystal violet to inhibit gram +
  • differential for lactose fermentation
A

MacConkey agar

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8
Q
  • peptone base with lactose and sucrose
  • eosin and methylene blue indicators
  • for the isolation and differentiation of lactose-fermenting and non-lactose-fermenting enteric bacilli
A

EMB agar

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9
Q

Sign of lactose fermentation on EMB agar

A

purple color change

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10
Q

No sign of lactose fermentation on EMB agar

A

colorless colonies

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11
Q
  • bile salts to inhibit gram + and some gram -

- differential for lactose and sucrose fermentation

A

HE agar

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12
Q

non-pathogen growth on HE agar

A

most ferment lactose and sucrose; orange color (low pH)

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13
Q

pathogen growth on HE agar

A

green to blue color; black precipitate due to H2S gas production

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14
Q
  • sodium desoxycholate to inhibit gram + and some gram -
  • sucrose, lactose and xylose(with phenol red indicator)
  • lysine to detect lysine decarboxylation
  • thiosulfate to detect H2S
A

XLD agar

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15
Q

Yellow colonies on XLD agar

A
  • fermenters or those not producing lysine decarboxylase

- E. coli, Citrobacter

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16
Q

Colorless or red colonies on XLD agar

A

likely Shigella

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17
Q

Red colonies with black centers on XLD agar

A
  • were yellow then became red when lysine is decarboxylated

- Salmonella

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18
Q

Virulence factors of Enterbacteriaceae

A

adherence, toxins, invasive enzymes, O, H, K antigens

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19
Q

heat stable antigen located in LPS of cell wall

A

O antigen

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20
Q

flagellar antigen; heat stable

A

H antigen

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21
Q

capsular antigen; heat labile; present in E. coli and Salmonella typhi

A

K antigen

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22
Q

Opportunistic Enterobacteriaceae

A
  • normal flora (E. coli)

- septicemia, wounds, UTI, meningitis

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23
Q

Pathogenic Enterobacteriaceae

A

Salmonella, Shigella, Yersinia enterocolitica

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24
Q
  • pink on MacConkey agar, beta hemolytic on SBA
  • motile, sex pili, fimbriae
  • posses O, H, K antigens
A

Escherichia coli (morphology)

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25
Q
  • ferments glucose, lactose, trehalose, and xylose
  • indole positive, methyl red positive (glucose fermentation via mixed acid pathway)
  • H2S, DNase, urease, PAD, and citrate negative
  • IMVC (+ + - -)
A

E. coli (biochemical reactions)

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26
Q

Types of E. coli gastrointestinal infections

A

Enteropathogenic (EPEC), Enterotoxigenic (ETEC), Enteroinvasive (EIEC), Enterohemorrhagic (EHEC), and Enteroadherent

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27
Q
  • infantile diarrhea, associated with nurseries and daycare

- adhesive, stool contain mucus but no blood

A

Enteropathogenic (EPEC) E. coli

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28
Q
  • Traveler’s diarrhea (tropics and subtropics)
  • requires large inoculum; contaminated food/water, poor hygiene and sanitation
  • binds to intestinal microvilli (adhesive)
  • releases toxins (heat-labile toxin and heat-stable toxin)
A

Enterotoxigenic (ETEC) E. coli

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29
Q

Enterotoxigenic E. coli toxins

A
  • heat-labile toxin (LT): A and B units, leads to hypersecretion of fluids
  • heat-stable toxin (ST): leads to hypersecretion
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30
Q
  • dysentery with direct penetration, invasion and destruction of intestinal mucosa
  • similar to Shigella but requires more inoculum
  • watery diarrhea with blood, mucus, WBCs
  • non-motile and don’t ferment lactose
A

Enteroinvasive (EIEC) E. coli

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31
Q
  • hemorrhagic diarrhea, colitis
  • hemolytic-uremic syndrome (HUS)
  • watery to bloody diarrhea (no WBCs)
  • E. coli O157:H7
A

Enterohemorrhagic (EHEC) E. coli

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32
Q

low platelets, hemolytic anemia, kidney failure

A

hemolytic-uremic syndrome

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33
Q
  • watery to bloody diarrhea can be fatal

- associated with undercooked meat, unpasteurized milk, apple cider, bean sprouts, spinach

A

Enterohemorrhagic E. coli

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34
Q
  • toxins produced by Shiga toxigenic E. coli (STEC)
  • include Verotoxin I cytotoxin and Verotoxin II
  • can be screened for on SMAC plate; does not ferment sorbitol
A

E. coli O157:H7

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35
Q
  • phage mediated cytotoxin
  • attacks vero cells, also called Shiga-like toxin
  • neutralized by Shiga toxin antibodies
A

Verotoxin I

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36
Q

E. coli O157:H7 toxin not neutralized by Shiga toxin antibodies

A

Verotoxin II

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37
Q

Diagnosing E. coli O157:H7

A
  • stool culture on differential medium with serotyping
  • screens for toxin
  • demonstrates a fourfold increase in toxin neutralizing antibody titer
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38
Q

Enteroadherent E. coli

A

includes diffusely adherent (DAEC) and enteroaggregative (EAEC)

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39
Q
  • causes UTI’s and diarrheal disease
  • cystitis in kids, acute pyelonephritis in pregnant women, recurring UTI’s, pediatric diarrheal disease (in developing countries)
A

Diffusely adherent (DAEC) E. coli

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40
Q
  • adheres to small intestine; more than 2 weeks
  • causes “stacked brick” pattern on cells
  • watery diarrhea, vomiting, dehydration, abdominal pain
  • mostly in children
A

Enteroaggregative (EAEC) E. coli

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41
Q

Extraintestinal infections of E. coli

A

UTI’s, meningitis, septicemia

42
Q

Unpathogenic E. coli

A

most common cause of UTI’s (catheters, etc.)

43
Q
  • most common in neonates, gain infection just before or during birth, can involve amniotic fluid
  • has capsule antigen K1
A

Meningitis (caused by E. coli)

44
Q

Septicemia (caused by E. coli)

A

may result from urogenital tract infection or from GI source

45
Q

Other E. coli

A
  • Escherichia hermanii (clinical significance not established)
  • Escherichia vulneris (wound infections)
46
Q

Klebsiella, Enterobacter, Serratia, Pantoea, Cronobacter, and Hafnia (source/general infections)

A
  • normal flora of GI tract, soil, water, on plants
  • opportunistic and nosocomial infections
  • UTI’s, wounds, pneumonia
47
Q

Klebsiella, Enterobacter, Serratia, Pantoea, Cronobacter, and Hafnia (biochemical reactions)

A
  • Simmon’s citrate +, Potassium cyanide broth +, no H2S production, no deamination of phenylalanine, urease -
  • Indole -, methyl red -, Voges-Proskauer +, citrate + (all),
  • IMVC - - + +
48
Q
  • most common Klebsiella isolate; affects lower resp. tract
  • moist, gray mucoid colonies
  • polysaccharide capsule (virulence)
A

Klebsiella pneumoniae

49
Q
  • similar to K. pneumoniae

- indole +

A

Klebsiella oxytoca

50
Q
  • isolated from nasal secretions and cerebral abscesses

- plasmid-mediated ESBL’s

A

Klebsiella ozaenea

51
Q
  • infection of the nasal cavity; intense swelling and malformation of entire face and neck
  • Africa and South America
A

Klebsiella rhinoscleromatis (pneumoniae subspecies)

52
Q

Two most commonly isolated Enterobacter species

A

E. cloacae and E. aerogenes

53
Q

Enterobacter (biochemical reactions)

A

MR -, VP +, most produce lysine decarboxylase (not E. cloacae) and ornithine decarboxylase; infect wounds, urine, blood, CSF

54
Q

Pantoea agglomerans

A
  • similar to K. pneumoniae
  • motile; lysine, ornithine, and arginine negative
  • outbreak from contaminated IV fluids
55
Q
  • associated with neonate meningitis and bacteremia

- brain abscesses, respiratory and wound infections

A

Coronobacter sakazakii

56
Q
  • positive ONPG (slow lactose)
  • DNase
  • highly resistant to antimicrobials
A

Serratia

57
Q
  • prodigiosin (red at room temp)
  • most clinically relevant Serratia species
  • opportunistic: UTI’s, bacteremia, respiratory nosocomial infections
A

Serratia marcescens

58
Q

Other Serratia species

A
  • S. liquefaciens, S. ficaria, S. entomophila, S. fonticola
  • S. rubidaea, S. plymuthica (red at room temp)
  • S. odorifera (dirty musty odor)
59
Q

Hafnia alvei

A
  • linked to gastroenteritis, can be isolated from stool samples
  • delayed citrate reaction, two biotypes
60
Q

Hafnia Biotype 1

A

grows in beer wort of breweries; not clinically isolated

61
Q

Hafnia Biotype 2

A

grown from environmental and human samples

62
Q
  • isolated from urine, wounds, ear and blood infections
  • produce swarming on lab media, burnt chocolate odor
  • positive phenylalanine deaminase, produce H2S
  • lactose -, urease +
A

Proteus species

63
Q

Proteus mirabilis

A
  • most commonly isolated Proteus

- indole -, ornithine decarboxylase +, K/A with H2S on TSI

64
Q

Proteus vulgaris

A

indole +, ornithine decarboxylase -, sucrose fermentation = A/A with H2S on TSI

65
Q

UTI infections, possibly diarrhea, similar to Proteus

A

Morganella morganii

66
Q

Providencia species

A
  • high resistance to antimicrobials

- P. rettgeri, P. stuartii, P. alcalifaciens

67
Q

urinary tract pathogen, nosocomial outbreaks

A

Providencia rettgeri

68
Q

nosocomial burn unit outbreaks, no swarming, isolated from urine clutures

A

Providencia stuartii

69
Q
  • E. tarda is only pathogen
  • urea -, lysine decarboxylase +, H2S +, indole +, no growth on citrate
  • bacteremia and wound infections
A

Edwardsiella

70
Q

Erwinia and Pectobacterium

A

plant pathogens

71
Q
  • weak urease activity, ferment lactose, grow on Simmon’s citrate, MR +, similar to Salmonella
  • C. freundii hydrolyzes urea and doesn’t decarboxylate lysine
  • Salmonella doesn’t hydrolyze urea and decarboxylates lysine
A

Citrobacter

72
Q
  • most common Citrobacter

- nosocomial UTI’s, pneumonia, endocarditis, intraabdomial abscesses

A

Citrobacter freundii

73
Q

Citrobacter associated with neonatal meningitis and brain abscesses

A

Citrobacter koseri

74
Q

Citrobacter braakii

A

nosocomial UTI’s

75
Q

Primary Enterobacteriaceae Intestinal Pathogens

A

Salmonella, Shigella, Yersinia

76
Q
  • gram negative rods, facultative anaerobes
  • clear, colorless, non lactose-fermenting colonies with black centers (K/A, H2S +)
  • indole -, VP -, phenylalanine deaminase -, urease -, no growth in Potassium cyanide medium, produce H2S
A

Salmonella

77
Q

most serious pathogens are Subgroup I (S. typhi, S. choleraesuis, S. paratyphi)

A

Salmonella enterica

78
Q

Differentiating Salmonella subgroup I members

A
  • lysine decarboxylase rules out S. paratyphi
  • ornithine decarboxylase rules out S. typhi
  • trehalose fermentation rules out S. choleraesuis
79
Q

Salmonella enterica virulence factors

A
  • fimbriae required for adhesion to intestines
  • invasion factor (able to transverse intestinal mucosa)
  • enterotoxin involved in gastroenteritis
80
Q

Antigenic structures of Salmonella

A
  • O and H antigens
  • Vi capsular antigen
  • used in serologic typing
81
Q

H antigen

A
  • occur in phase I and II
  • Phase I not always present but identify particular serotype
  • Phase II are nonspecific
82
Q

Capsular Vi antigen

A

similar to capsular K antigen, always present, prevents phagocytosis

83
Q

Salmonella enterica (clinical infections)

A
  • acute gastroenteritis or food poisoning caused by organism (not toxin); milk, poultry, eggs, pet handling
  • carrier state in gallbladder
  • nontyphoidal bacteremia, typhoid fever, other fevers
84
Q

Typhoid fever disease course

A
  • ingestion of organism; fever, malaise, anorexia, lethargy begin 9-14 days later (flu-like)
  • invades and penetrates intestinal mucosa, constipation
  • enters lymphatic system, sustained in mesenteric lymph nodes
  • enters blood stream; goes to spleen, liver, bone marrow; engulfed by monocytes and grow intracellularly
  • released into blood stream again (isolated from blood now); prolonged bacteremia, rose spots on abdomen
  • invasion of gallbladder and Peyer’s patches, bacteria released into bowel (isolated from stool now), long-term infection/necrosis of gallbladder, hemorrhage and perforation of bowel
85
Q

non-typhoidal bacteremia

A
  • prolonged fever with intermittent bacteremia
  • fever and gastroenteritis with brief bacteremia in kids
  • transient bacteremia during gastroenteritis or septicemia without gastroenteritis in adults
86
Q

Shigella species

A

S. dysenteriae (group A), S. flexneri (group B), S. boydii (group C), S. sonnei (group D)

87
Q
  • Shigella that causes the most serious infections

- primarily in developing countries

A

Shigella dysenteriae (group A)

88
Q

Shigella flexneri (group B)

A

second most common Shigella in the United States; associated in men having sex with men pop. and young adults

89
Q

Shigella boydii (group C)

A

most common in developing countries

90
Q

most common Shigella isolate in the United States; causes short, self-limiting infections

A

Shigella sonnei (group D)

91
Q

Shigella species (general characteristics)

A
  • non-motile, non lactose-fermenting (K/A)
  • don’t produce gas (except group B)
  • urease -, no H2S on TSI, doesn’t decarboxylate lysine
  • S. sonnei is ONPG and ornithine decarboxylase + (S. flexneri is -)
92
Q

Shigella species (clinical infections)

A
  • dysentery (S. dysenteriae)
  • fever and watery diarrhea (S. sonnei)
  • requires low inoculum (resistant to stomach acid, spread by fecal-oral route
  • penetration of mucosal epithelium (Shiga toxin)
93
Q

Dysentery (S. dysenteriae)

A
  • most severe Shigella infection

- local inflammation, fever, chills, shedding of intestinal mucosa, mucus, blood, ulcers, tenesmus (prolapsed rectum)

94
Q
  • H2S - on TSI (K/A)

- isolated on CIN agar or CIN II agar with Aeromonas

A

Yersinia

95
Q
  • Class A Bioterrorism agent
  • causes The Plague; transmitted through rodents (except pneumonic form-respiratory droplets)
  • gram - coccobacilli resembling a safety pin
  • negative for motility above 22C, ornithine decarboxylase -
A

Yersinia pestis

96
Q
  • contact with/ingestion of swine, cats, dogs, fecal material
  • survives at cold temperatures, affects kids and ICP’s
  • acute gastroenteritis, simulates apendicitis
  • causes erythema nodosum (red nodules on lower legs - cause itching and burning)
  • motility at 25C, non-motile at 37C
  • grows at 4C, ornithine decarboxylase +
A

Yersinia enterocolita

97
Q
  • rodents, farm animals, birds, guinea pigs; ingestion of fecal material
  • caseous swelling called pseudotubercles in mesenteric lymph nodes
  • motile at 25C; ornithine decarboxylase -
A

Yersinia pseudotuberculosis

98
Q
  • peptone base with yeast extract, mannitol, bile salts, cefsulodin, igrasan, novobiocin, neutral red and crystal violet indicators
  • selective for Yersinia and Aeromonas
A

CIN (Cefsulodin-Igrasan-Novobiocin) agar

99
Q

Screen stool pathogens (HE, XLD, Mac, SMAC) for ______

A

Salmonella, Shigella, Campylobacter, E. coli O157:H7

100
Q

Screen stool pathogens (CIN agar) for ____________

A

Yersinia

101
Q

Serologic grouping for __________

A
  • Salmonella (60 types of O antigens; agglutination)

- Shigella (A through D serotypes)

Microbiology (26 decks)

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