Enterobacteriaceae Pt. 1
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1
Q: Many Gram-negative rods are commonly referred to as what type of organisms?
A: Gut bugs
2
Q: Which gut organisms are NOT normal flora of the GI tract?
A: Salmonella, Shigella, and Yersinia
3
Q: Where are environmental Gram-negative rods commonly found?
A: Soil, water, and sewage (feces)
4
Q: Are most Enterobacteriaceae aerobic or facultative anaerobes?WhatEMBXLD
A: Facultative anaerobes
5
Q: Are Enterobacteriaceae typically glucose fermenters?
A: Yes — Glucose positive
6
Q: What is the oxidase reaction of most Enterobacteriaceae?
A: Oxidase negative
7
Q: What organism is an oxidase-positive Enterobacteriaceae exception?
A: Plesiomonas
8
Q: What does nitrate positive mean for Enterobacteriaceae?
A: They reduce nitrate → nitrite
9
Q: What does the O antigen represent?
A: Cell wall (somatic) antigen
10
Q: Is the O antigen heat stable or heat labile?
A: Heat stable
11
Q: What does the K antigen represent?
A: Capsular (envelope) antigen
12
Q: Is the K antigen heat stable or heat labile?
A: Heat labile
13
Q: What does the H antigen represent?
A: Flagellar antigen
14
Q: Is the H antigen heat stable or heat labile?
A: Heat labile
15
Q: What does the Vi antigen represent?
A: Capsular antigen
16
Q: Which organism is associated with the Vi antigen?
A: Salmonella typhi
17
Q: Is the Vi antigen heat stable or heat labile?
A: Heat labile
18
Q: Where is Escherichia coli normally found?
A: In the human and animal intestinal tract
19
Q: Is E. coli usually normal flora or a pathogen?
A: Most are normal flora of the gut, but some strains cause disease.
20
Q: What type of GI illness can E. coli cause?
A: Diarrhea / gastroenteritis, including travelers’ diarrhea
21
Q: Which E. coli strain is associated with hemorrhagic colitis and HUS?
A: E. coli O157:H7
22
Q: What infection is E. coli the #1 cause of?
A: Urinary tract infections (UTIs)
23
Q: Besides UTIs and diarrhea, what other infections can E. coli cause?
A: Appendicitis, neonatal meningitis, peritonitis, gall bladder infections, endocarditis, and food poisoning
24
Q: Why can E. coli appear in many different clinical specimens?
A: It causes many opportunistic infections
25
Q: What type of E. coli strain is O157:H7?
A: Enterohemorrhagic E. coli (EHEC)
26
Q: What is the reservoir of E. coli O157:H7?
A: Intestinal tract of cattle
27
Q: How is E. coli O157:H7 transmitted to humans?
A: Fecal-oral transmission
28
Q: Name common sources of infection for E. coli O157:H7.
A: Undercooked beef, contaminated vegetables (spinach), unpasteurized milk, contaminated water, petting zoos
29
Q: What toxin is produced by E. coli O157:H7?
A: Shiga-like toxin (STEC)
30
Q: What intestinal disease is caused by the Shiga-like toxin of O157:H7?
A: Hemorrhagic colitis
31
Q: What serious complication can occur with E. coli O157:H7 infection?
A: Hemolytic Uremic Syndrome (HUS)
32
Q: What happens in Hemolytic Uremic Syndrome (HUS)?
A: Toxin damages kidneys → kidney failure, anemia, low platelets
33
Q: Which groups are most at risk for severe O157:H7 infection?
A: Children and the elderly
34
Q: What is the typical incubation period for E. coli O157:H7?
A: 3–4 days (range 1–10 days)
35
Q: What does STEC stand for?
A: Shiga toxin-producing Escherichia coli
36
Q: Why should antibiotics be used cautiously with STEC infections?
A: Antibiotics may increase the risk of developing HUS and benefit is not clearly shown.
37
Q: What must be done before administering antibiotics for suspected STEC infection?
A: Rule out STEC prior to antibiotic administration
38
Q: What toxins are produced by STEC?
A: Shiga toxin 1 and Shiga toxin 2 (may carry both)
39
Q: Which Shiga toxin is generally more virulent?
A: Shiga toxin 2
40
Q: What STEC types should be included in diagnostic testing?
A: STEC O157 and non-O157 STEC
41
Q: To whom must STEC infections be reported?
A: Los Angeles County Department of Public Health
42
Q: How quickly must labs report Shiga toxin-producing E. coli (including O157)?
A: Within 1 working day
43
Q: What does ETEC stand for? & How does ETEC cause disease?
A: Enterotoxigenic E. coli;
Enterotoxins mediate secretion of water and electrolytes into the bowel lumen, causing profuse watery stools.
Enterotoxins mediate secretion of water and electrolytes into the bowel lumen, causing profuse watery stools.
44
Q: What illness is commonly associated with ETEC?
A: Traveler’s diarrhea from contaminated food or water
45
Q: What does EIEC stand for? How does EIEC cause disease? What disease is caused by EIEC?
A: Enteroinvasive;
The organism invades the large intestinal lining similar to Shigella.;
Dysentery, involving necrosis, ulceration, and inflammation of the bowel, associated with children in areas of poor sanitation.
The organism invades the large intestinal lining similar to Shigella.;
Dysentery, involving necrosis, ulceration, and inflammation of the bowel, associated with children in areas of poor sanitation.
46
Q: What does EPEC stand for? How does EPEC cause disease? What illness is associated with EPEC?
A: Enteropathogenic;
The organism attaches to mucosal cells of the small bowel, causing small bowel surface changes (loss of microvilli);
A: Diarrhea (sometimes chronic) in infants in developing or low-income nations
The organism attaches to mucosal cells of the small bowel, causing small bowel surface changes (loss of microvilli);
A: Diarrhea (sometimes chronic) in infants in developing or low-income nations
47
Q: What does EAEC stand for?
What is known about the pathogenic mechanism and transmission of EAEC?What illness is associated with EAEC?
What is known about the pathogenic mechanism and transmission of EAEC?What illness is associated with EAEC?
A: Enteroaggregative E. coli;
Unknown pathogenic mechanism and mode of transmission not well understood;
Watery diarrhea that can be prolonged
Unknown pathogenic mechanism and mode of transmission not well understood;
Watery diarrhea that can be prolonged
48
Q: What disease is caused by Shigella?
A: Shigellosis (bacillary dysentery)
49
Q: Where does Shigella proliferate and where does it cause damage?
A: Proliferates in the small intestine but damages the large intestine
50
Q: What type of intestinal inflammation does Shigella cause?
A: Acute inflammatory colitis
51
Q: What are common symptoms of Shigellosis?
A: Cramps, tenesmus, bloody/mucoid stools or diarrhea, and fever
52
Q: Which groups experience the most severe Shigella infections?
A: Children and the elderly
53
Q: Is Shigella considered normal flora?
A: No
54
Q: How is Shigella transmitted?
A: Human feces → human oral transmission (fecal-oral)
55
Q: How infectious is Shigella?
A: Highly pathogenic — fewer than 50 bacteria can cause disease
56
Q: Why can Shigella survive stomach acid relatively well?
A: The bacteria are not strongly affected by stomach acid
57
Q: What is the incubation period for Shigella infection?
A: 1–7 days
58
Q: Which antigen is used to serotype Shigella?
A: O antigen (because it lacks H antigen due to being non-motile)
59
Q: Which species causes the most severe dysentery?
A: Shigella dysenteriae
60
Q: What toxin is produced by Shigella dysenteriae?
A: Shiga toxin
61
Q: What severe outcomes can occur with Shigella dysenteriae infection?
A: Bloodstream invasion and mortality up to 20%
62
Q: How does Shigella infect intestinal cells?
A: It enters intestinal epithelial cells, multiplies inside them, spreads to neighboring epithelial cells, forms abscesses as cells are destroyed, and blood/mucus enter stool.
63
Q: How are Shigella serogroups determined in the laboratory?
A: Bacterial agglutination
64
Q: What should be done if a Shigella isolate is untypeable?
A: Boil the suspension of the organism and retest to inactivate the capsule that may mask the O antigen.
65
Q: Which organism belongs to Serogroup A?
A: Shigella dysenteriae
66
Q: What illnesses are associated with Shigella dysenteriae (Serogroup A)?
A: Enterotoxin attacking the large intestines and a neurotoxin that may cause paralysis
67
Q: What are the mannitol and ONPG results for Shigella dysenteriae?
A: Mannitol – , ONPG –
68
Q: Which organism belongs to Serogroup B?
A: Shigella flexneri
69
Q: What illness is associated with Shigella flexneri?
A: Mild diarrhea; common in the U.S.; post-infectious arthritis in HLA-B27 positive patients
70
Q: What are the mannitol and ONPG results for Shigella flexneri?
A: Mannitol + , ONPG –
71
Q: Which organism belongs to Serogroup C?
A: Shigella boydii
72
Q: What illness is associated with Shigella boydii?
A: Mild diarrhea
73
Q: What are the mannitol and ONPG results for Shigella boydii?
A: Mannitol + , ONPG –
74
Q: Which organism belongs to Serogroup D?
A: Shigella sonnei
75
Q: What illness is associated with Shigella sonnei?
A: Mild diarrhea, sometimes watery; most common cause of shigellosis in the U.S.
76
Q: What are the mannitol and ONPG results for Shigella sonnei?
A: Mannitol + , ONPG +
77
Q: How many species of Salmonella are there?
A: Two species: Salmonella enterica and Salmonella bongori
78
Q: Approximately how many Salmonella serotypes exist?
A: More than 2,400 serotypes
79
Q: What type of illness do most Salmonella serotypes cause?
A: Moderate to severe gastroenteritis
80
Q: Which species is responsible for the majority of Salmonella illnesses?
A: Salmonella enterica
81
Q: Name important serotypes of Salmonella enterica.
A: S. typhi, S. paratyphi, S. typhimurium, and S. enteritidis
82
Q: What are common animal reservoirs of Salmonella?
A: Many animals including reptiles and chickens
83
Q: Which Salmonella species is found only in humans?
A: Salmonella typhi
84
Q: How is Salmonella typhi transmitted?
A: Human feces → human oral transmission (fecal-oral)
85
Q: How is Salmonella most commonly transmitted overall?
A: Contaminated water and undercooked food (especially chicken)
86
What is the incubation period for S. enterica?
12-36 hours
87
What is the incubation period for S. typhi?
2 weeks
88
What are the sympotoms for S. enterica?
– moderate fever
– nausea
– abdominal pain
– cramps
– diarrhea
– nausea
– abdominal pain
– cramps
– diarrhea
89
What are the sympotoms for S. typhi?
– high fever
– headache
– diarrhea
– headache
– diarrhea
90
What is the mortality rate of S.enterica?
– general population: low
– very young/old: higher
– very young/old: higher
91
What is the mortality rate of S.enterica?
– today: 1-2%
– late 19th
-early 20th century: 10-30%
– today, undeveloped areas: 10-30%
– late 19th
-early 20th century: 10-30%
– today, undeveloped areas: 10-30%
92
What is the source of S. enterica? and how does it enter the human body?
– Poultry/poultry products (eggs)
• Multi-drug resistance linked to
antibiotic use in poultry
– Unpasteurized milk/milk products
• Bacterium enters intestinal epithelial
cell -> multiply w/in vesicle inside cell
– death, if occurs, usually due to septicemia
• Multi-drug resistance linked to
antibiotic use in poultry
– Unpasteurized milk/milk products
• Bacterium enters intestinal epithelial
cell -> multiply w/in vesicle inside cell
– death, if occurs, usually due to septicemia
93
What is the source of S. typhi and how does it enter the human body?
human
• Bacterium multiply in phagocytic cells -> can become disseminated throughout the body
– can be isolated in blood, urine, feces
– multiple organ failure can occur if disseminated
– death due to: perforation of the intestine-> septicemia/peritonitis
• INFECTED CAN BECOME CARRIERS
– bacterium remain in gallbladder
– “Typhoid Mary”
• presumed to have infected almost 50,
3 deaths (she was a cook)
• Bacterium multiply in phagocytic cells -> can become disseminated throughout the body
– can be isolated in blood, urine, feces
– multiple organ failure can occur if disseminated
– death due to: perforation of the intestine-> septicemia/peritonitis
• INFECTED CAN BECOME CARRIERS
– bacterium remain in gallbladder
– “Typhoid Mary”
• presumed to have infected almost 50,
3 deaths (she was a cook)
94
MAC
TYPE:
WHAT GROWS:
KEY INGREDIENTS:
SHIGELLA =
SALMONELLA =
TYPE:
WHAT GROWS:
KEY INGREDIENTS:
SHIGELLA =
SALMONELLA =
TYPE: Selective Differential
WHAT GROWS: GNR
KEY INGREDIENTS: lactose, crystal violet & bile salts inhibit G+; neutral red as indicator
SHIGELLA = colorless
SALMONELLA = colorless w/ black centers
Coliforms (lact +): pink
WHAT GROWS: GNR
KEY INGREDIENTS: lactose, crystal violet & bile salts inhibit G+; neutral red as indicator
SHIGELLA = colorless
SALMONELLA = colorless w/ black centers
Coliforms (lact +): pink
95
EMB
TYPE:
WHAT GROWS:
KEY INGREDIENTS:
SHIGELLA =
SALMONELLA =
TYPE:
WHAT GROWS:
KEY INGREDIENTS:
SHIGELLA =
SALMONELLA =
TYPE: Selective Differential
WHAT GROWS: GNR
KEY INGREDIENTS: lactose, sucrose. Eosin and Methylene blue as indicators
SHIGELLA = clear
SALMONELLA = clear
Coliforms: blue black
WHAT GROWS: GNR
KEY INGREDIENTS: lactose, sucrose. Eosin and Methylene blue as indicators
SHIGELLA = clear
SALMONELLA = clear
Coliforms: blue black
96
HE
TYPE:
WHAT GROWS:
KEY INGREDIENTS:
SHIGELLA =
SALMONELLA =
TYPE:
WHAT GROWS:
KEY INGREDIENTS:
SHIGELLA =
SALMONELLA =
TYPE: Selective differential
WHAT GROWS: GNR
KEY INGREDIENTS: lactose, sucrose, salicin, ferric amm. citrate, bile salts. Bromthymol blue/acid fusion (ind)
SHIGELLA = green
SALMONELLA = green/ black (lact - , H2S+)
Coliforms (lact +): yellow/salmon, + / - black centers
WHAT GROWS: GNR
KEY INGREDIENTS: lactose, sucrose, salicin, ferric amm. citrate, bile salts. Bromthymol blue/acid fusion (ind)
SHIGELLA = green
SALMONELLA = green/ black (lact - , H2S+)
Coliforms (lact +): yellow/salmon, + / - black centers
97
SS
TYPE:
WHAT GROWS:
KEY INGREDIENTS:
SHIGELLA =
SALMONELLA =
TYPE:
WHAT GROWS:
KEY INGREDIENTS:
SHIGELLA =
SALMONELLA =
TYPE: Selective differential
WHAT GROWS: Shigella Salmonella only
KEY INGREDIENTS: lactose, ferric/sodium citrate, neutral red (ind), brilliant green / bile salts inhibits other enterics
SHIGELLA = colorless
SALMONELLA = colorless / black
WHAT GROWS: Shigella Salmonella only
KEY INGREDIENTS: lactose, ferric/sodium citrate, neutral red (ind), brilliant green / bile salts inhibits other enterics
SHIGELLA = colorless
SALMONELLA = colorless / black
98
XLD
TYPE:
WHAT GROWS:
KEY INGREDIENTS:
SHIGELLA =
SALMONELLA =
TYPE:
WHAT GROWS:
KEY INGREDIENTS:
SHIGELLA =
SALMONELLA =
TYPE: Selective Differential
WHAT GROWS: GNR
KEY INGREDIENTS: lysine, xylose, lactose, sucrose, ferrice amm. citrate, Na desoxcholate inhibits G+, phenol red (ind)
SHIGELLA = red
SALMONELLA = red/ black centers
Coliforms: yellow/ orange
WHAT GROWS: GNR
KEY INGREDIENTS: lysine, xylose, lactose, sucrose, ferrice amm. citrate, Na desoxcholate inhibits G+, phenol red (ind)
SHIGELLA = red
SALMONELLA = red/ black centers
Coliforms: yellow/ orange
99
Selenite
TYPE:
WHAT GROWS:
KEY INGREDIENTS:
SHIGELLA =
SALMONELLA =
TYPE:
WHAT GROWS:
KEY INGREDIENTS:
SHIGELLA =
SALMONELLA =
TYPE: Selective enrichment
WHAT GROWS: Salmonella
KEY INGREDIENTS: Sodium selenite toxic for G+ and most Enterobacteriaceae
Isolate Salmonella
WHAT GROWS: Salmonella
KEY INGREDIENTS: Sodium selenite toxic for G+ and most Enterobacteriaceae
Isolate Salmonella
100
Q: What is the most common species of Edwardsiella?
A: Edwardsiella tarda
101
Q: Are human infections with Edwardsiella common?
A: No, they are uncommon
102
Q: What are common sources of Edwardsiella?
A: Environment, snakes, and turtles
103
Q: What types of infections can Edwardsiella cause?
A: Diarrhea, wound infections, and septicemia
104
Q: Which organism does Edwardsiella resemble biochemically?
A: Salmonella
105
Q: What are the shared biochemical characteristics of Edwardsiella and Salmonella?
A: H2S positive and ONPG negative (lactose negative)
106
Q: How can Edwardsiella tarda be differentiated from Salmonella?
A: Indole positive and citrate negative
107
Q: What types of infections are associated with Klebsiella?
A: UTIs, pneumonia, septicemia, and nosocomial infections
108
Q: What type of sputum is characteristic of Klebsiella pneumonia?
A: “Currant jelly” sputum (bloody sputum)
109
Q: Which groups are at higher risk for Klebsiella infections?
A: Diabetics and alcoholics
110
Q: What is the most commonly isolated Klebsiella species?
A: Klebsiella pneumoniae
111
Q: What colony appearance is typical for Klebsiella pneumoniae?
A: Highly mucoid colonies due to capsule
112
Q: Is Klebsiella pneumoniae motile?
A: No, it is non-motile
113
Q: What is the indole result for Klebsiella pneumoniae?
A: Indole negative
114
Q: What is the indole result for Klebsiella oxytoca?
A: Indole positive
115
Q: What disease is caused by Klebsiella (Calymmatobacterium) granulomatis?
A: Granuloma inguinale (STD)
116
Q: What is unique about Klebsiella granulomatis regarding laboratory testing?
A: It does not Gram stain or grow on lab media
117
Q: What may be seen in Wright or Giemsa-stained specimens of Klebsiella granulomatis infections?
A: Donovan bodies (intracellular pleomorphic bipolar staining bacteria)
118
Q: What organism is now called Klebsiella aerogenes?
A: Formerly Enterobacter aerogenes
119
Q: What antibiotic resistance is intrinsic to Klebsiella?
A: Intrinsic resistance to ampicillin (Amp = R)
120
Q: How many species of Enterobacter are there?
A: 12 species
121
Q: What are common sources of Enterobacter?
A: Human/animal gut, soil, water, and dairy products
122
Q: What types of infections can Enterobacter cause?
A: Respiratory tract infections, wound infections, and bloodstream infections
123
Q: What is the most common Enterobacter isolate?
A: Enterobacter cloacae
124
Q: What organism was formerly Enterobacter sakazakii?
A: Cronobacter sakazakii
125
Q: What type of food poisoning is associated with Cronobacter sakazakii?
A: Infant formula
126
Q: What diseases can Cronobacter sakazakii cause in infants?
A: Meningitis and enteritis
127
Q: What is the mortality rate for infants infected with Cronobacter sakazakii?
A: 20–50%
128
Q: What other infections can Cronobacter sakazakii cause?
A: Wound infections and UTIs in all ages
129
Q: What characteristic helps identify Cronobacter sakazakii in the lab?
A: Yellow pigment
130
Q: Which Enterobacter species is lactose negative?
A: Enterobacter taylorae
131
Q: What type of pathogen is Serratia?
A: Opportunistic pathogen
132
Q: Which patients are commonly affected by Serratia infections?
A: Chemotherapy patients, immunosuppressed patients, and neonates (NICU outbreaks)
133
Q: What is the most common Serratia species isolated?
A: Serratia marcescens
134
Q: What pigment can some Serratia marcescens strains produce?
A: Pink or red pigment that deepens when held at room temperature
135
Q: What is the lactose fermentation characteristic of Serratia?
A: Delayed lactose fermenter but ONPG positive
136
Q: What infections are associated with Proteus?
A: UTIs, pneumonia, and septicemia
137
Q: How many Proteus species are there?
A: Four species
138
Q: Which Proteus species are most commonly isolated?
A: Proteus vulgaris and Proteus mirabilis
139
Q: What are key biochemical characteristics of Proteus?
A: H₂S positive, lactose negative, ONPG negative
140
Q: What unique growth characteristic is seen with Proteus?
A: Swarming motility
141
Q: How can Proteus vulgaris and Proteus mirabilis be differentiated?
A: P. vulgaris indole positive, P. mirabilis indole negative
142
Q: What additional enzyme tests are positive in Proteus?
A: Urease positive and tryptophan deaminase (TDA/PDA) positive
143
Q: What odor is characteristic of Proteus colonies?
A: Musky smell
144
Q: What infections are associated with Providencia?
A: UTIs, pneumonia, and septicemia
145
Q: How many Providencia species exist?
A: Five species
146
Q: How many Providencia species are found in humans?
A: Four
147
Q: What are the key biochemical characteristics of Providencia?
A: PDA+, TDA+, indole+, citrate+, and VP−
148
Q: Which Providencia species is most commonly isolated?
A: Providencia rettgeri
149
Q: Name other Providencia species mentioned.
A: Providencia stuartii and Providencia alcalifaciens
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