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MHD 1 > L26 The Enterobacteriaceae II > Flashcards

L26 The Enterobacteriaceae II Flashcards

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1
Q

What are the 4 important species of Shigella and what serogroup do they belong to?

A
  1. Shigella dysenteriae (A)
  2. Shigella flexneri (B)
  3. Shigella boydii (C)
  4. Shigella sonnei (D)
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2
Q

Which species of Shigella accounts for 70% of U.S. isolates?

A

Shigella sonnei

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3
Q

How is Shigella similar to E. coli? How is it different?

A

Similar biochemically, antigenically, and genetically

Unlike E. coli, it is non-lactose fermenting, non-gas producing, and non-motile

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4
Q

What is the primary reservoir of Shigella?

A

Human intestines

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5
Q

___ cases of Shigella are reported annually in the US.

A

500,000

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6
Q

How is Shigella transmitted?

A

Person to person via the fecal oral route

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7
Q

Shigella can be found in what 6 locations?

A

Water, food, flies, fingers, fomites, feces

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8
Q

Which populations are at highest risk for Shigella?

A

Young children in day care centers/nurseries, siblings and parents of these children, MSM

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9
Q

What is the major clinical syndrome associated with Shigella?

A

Bacillary dysentery

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10
Q

What are the symptoms of bacillary dysentery?

A

Abdominal cramps, tenesmus, pus, blood, and leukocytes present in the stool

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11
Q

Which tissues do Shigella invade through in bacillary dysentery?

A

Epithelial cells and submucosa

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12
Q

What is the incubation period and the length of disease for bacillary dysentery?

A

Incubation: 1-3 days; length: 48 hours

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13
Q

True or false - bacillary dysentery is the most communicable of bacterial diarrheas.

A

True

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14
Q

What is the concentration of Shigella in the stool when a person has bacillary dysentery?

A

10^3-10^4 CFU/gram

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15
Q

Describe the pathogenesis of Shigella.

A

Virulent strains carry a plasmid for attachment and entry. They enter cells via a phagocytic vacuole. The organism escapes into the cytoplasm and replicates intracellularly. Organisms enter adjacent cells.

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16
Q

What drives Shigella through the cytoplasm?

A

An actin tail

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17
Q

S. dysenteriae strains produce ___ exotoxin.

A

Shiga toxin

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18
Q

Compare the toxins produced by E. coli in STEC and the toxin produced by S. dysenteriae.

A

Stx1 is identical

Stx2 is 60% homologous

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19
Q

How does Shiga toxin function?

A

Disrupts protein synthesis in the cell and leads to epithelial cell damage

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20
Q

Where is Edwardsiella tarda found?

A

Cold blooded vertebrates, fresh water, catfish

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21
Q

What are the clinical manifestations of Edwardsiella tarda?

A
  1. Gastroenteritis

2. Septicemia (rare)

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22
Q

What types of gastrointestinal disease does Edwardsiella cause?

A
  1. Acute, self-limiting gastroenteritis with water diarrhea
  2. Typhoid-like illness with bloody diarrhea and possible fever, nausea, vomiting, colonic ulcerations and terminal ileum nodularity
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23
Q

Edwardsiella tarda is sometimes mistaken for which diseases?

A

Salmonellosis and IBD (Chron’s disease)

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24
Q

What is the important species of Salmonella?

A

Salmonella enterica

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25
All serotypes of Salmonella enterica are considered single species except S. bongori. Which of these are listed as separate species?
1. S. typhi/paratyphi 2. S. typhimurium 3. S. enteritidis
26
What is the habitat for salmonella?
Lower animals for non-typhoid strains, humans for S. typhi (gall bladder)
27
What are the major characteristics of Salmonella?
Non-lactose fermenter, produces hydrogen sulfide (black)
28
How is Salmonella transmitted?
Improper food handling, secondarily from person-to-person
29
True or false - Salmonella requires a high inoculum for disease.
True, except for S. typhi
30
An estimated ___ cases of non-typhoidal salmonellosis occur in the U.S. annually, with ___ hospitalizations and ___ deaths.
1.4 million; 16,000; 600
31
___ cases of S. typhi are reported in the U.S. each year and are associated with ___.
500; travel (27 million cases and 200,000 deaths worldwide)
32
About half of salmonella epidemics are the result of contaminated ___. They are also associated with ___.
Poultry/poultry products; reptiles
33
What are the clinical syndromes associated with Salmonella?
1. Asymptomatic carrier states 2. Febrile gastroenteritis 3. Septicemia without major GI inolvement 4. Enteric fever
34
The carrier state of Salmonella is limited with which types and is chronic with which types?
Limited - non-S. typhi Chronic - S. typhi
35
What is the most common presentation when infected with Salmonella?
Febrile gastroenteritis (found in 2/3 of patients with culture confirmed)
36
What is the incubation period and duration of febrile gastroenteritis associated with Salmonella?
12-48 hours; 3-5 days
37
What are the symptoms of febrile gastroenteritis associated with Salmonella?
Malaise, nausea, sometimes vomiting, followed by abdominal pain and diarrhea; self-limited
38
Septicemia without major GI involvement caused by Salmonella is characteristically found in which patient populations?
Patients with underlying leukemia, lymphoma, AIDS, SLE, sickle cell crisis, alcoholic hepatitis; increased risk in pediatric, geriatric, and AIDS patients
39
Salmonella is the cause of 10% of localized suppurative infections such as ___, ___, and ___>
Osteomyelitis, endocarditis, arthritis
40
How is septicemia associated with salmonella diagnosed?
Positive blood cultures
41
What is the best known example of enteric fever as well as a milder form?
Typhoid fever, paratyphoid fever
42
What types of Salmonella cause enteric fever?
S. typhi and S. paratyphi A and B
43
What part of a patient's history can aid in diagnosis of enteric fever?
Travel history
44
What is the incubation period and length of illness for enteric fever?
Incubation: 1-2 weeks Length of illness: 4 weeks (fever for 2 weeks, GI symptoms fo 1-2 weeks)
45
How does enteric fever present?
Fever, headache, rose spots (pink macules or prupuric lesions), constipation
46
Describe the pathogenesis of the gastroenteritis seen with salmonella.
Salmonella produces an adhesin that stimulates rearrangement of the plasma cell membrane to form ruffles. Bacteria enter the cell by pinocytosis associated with these ruffles. They invade large and small bowel and the lamina propria and induce a large inflammatory response.
47
Describe the pathogenesis of enteric fever.
Bacteria bind to M cells. Infection kills the cells, and the bacteria go the the Peyer's patches. Organisms invade macrophages where they multiply. Organisms inhibit oxidative metabolic burst, allowing them to survive intracellularly. They spread from Peyer's patches into the RES, and into the bloodstream. They colonize the gallbladder.
48
What are the important species of Citrobacter?
C. freundii and C. koseri
49
What is the habitat of Citrobacter?
Intestinal tract of humans and animals
50
Citrobacter species cause what clinical syndromes?
Nosocomial infections of urinary and respiratory tracts of debilitated, hospitalized patients, endocarditis,, and hospital acquired bacteremias
51
C. freundii is a rare cause of ___. C. koseri is a rare cause of ___ and ___ in neonates.
Diarrhea; meningitis; brain abscess
52
What are the 4 important species of Klebsiella?
K. pneumoniae, K. oxytoca, K. ozaenae, K. rhinoscleromatis
53
What is the habitat of Klebsiella species?
Intestines and upper respiratory tract of humans and animals
54
What are the clinical syndromes associated with K. pneumoniae and K. oxytoca?
Primary lobar pneumonia characterized by destructive changes, necrosis, and hemorrhage (currant jelly sputum), bronchopneumonia, bronchitis, UTIs, bacteremias
55
What are the clinical syndromes associated with K. ozaenae?
Atrophic rhinitis, destruction of mucosa and fetid mucopurulent discharge
56
What are the clinical syndromes associated with K. rhinoscleromatis?
Rhinoscleroma, chronic granulomatous disease involving the mucosa of the upper respiratory tract
57
What is a major virulence factor of Klebsiella?
Capsule
58
What are the 2 important species of Enterobacter?
1. E. aerogenes | 2. E. cloacae
59
What is the habitat of Enterobacter?
Environment, GI tract of humans
60
Enterobacter frequently colonize which patients?
Hospital patients
61
Enterobacter cause opportunistic infections in hospital patients, including...
...UTI, respiratory tract infections, infections of cutaneous wounds, septicemia, and meningitis
62
Why is antibiotic therapy often ineffective with Enterobacter?
The organisms are frequently multiply resistant
63
What is the important Serratia species?
S. marcescens
64
What are the clinical syndromes caused by S. marscescens?
Nosocomial infections, pneumoniae, septicemia, UTI, surgical wound and cutaneous infections, endocarditis and osteomyelitis in IV drug users
65
What color do S. marcescens grow on MacConkey agar?
Red
66
What are the important Proteus species?
1. P. mirabilis | 2. P. vulgaris
67
What are the 3 key ID features of Proteus species?
1. Swarming observed on blood agar 2. Lactose negative on MacConkey agar 3. Strongly ureas positive
68
What is the habitat of Proteus bacteria?
Soil, water, and intestinal tract of humans and animals;
69
What are the two most common isolates in the clinical laboratory?
1. E. coli (first) | 2. Proteus (second)
70
What is the most frequently isolated species of Proteus?
P. mirabilis
71
P. mirabilis causes what clinical syndromes?
UTIs and wound infections
72
P. mirabilis produces highly alkaline ___, which can lead to what?
Urea; renal calculi composed of struvite
73
P. vulgaris is most commonly recovered from ___.
Infected sites in IC patients
74
What is the most common species of Yersinia?
Y. enterocolitica
75
Where is Y. enterocolitica found?
Lakes and reservoirs
76
Y. enterocolitica can cause ___ outbreaks of diarrhea, lymphadenopathy, pneumonia, and spontaneous abortions in various animals.
Epizootic
77
What are the important virulence factors of Y. enterocolitica?
1. YOPS (outer proteins) that resist phagocytosis
78
___ are major reservoir of Y. enterocolitica in humans.
Pigs
79
___ infections with Y. enteroclitica occur in the U.S. annually.
100,000
80
Y. entercolitica causes diarrheal illness associated with household preparation of ___; milk and water are also sources.
Chitterlings
81
What is the portal of entry for Y. enterocolitica?
Oral digestive route
82
What time of year is Y. eneterocolitica common during?
Cold months
83
2/3 of infection with Y. enterocolitica causes ___.
Enterocolitis
84
What is the incubation period and length of illness for entercolitis caused by Y. enterocolitica?
4-6 days of incubation; diarrhea, fever, and abdominal pain last as long as 1-2 weeks
85
How does a chronic form of enterocolitis occur caused by Y. enterocolitica?
Organisms adhere to and penetrate the ileum, causing terminal ileitis, lymphadenitis, and acute enterocolitis; this mimics appendicitis and is most common in children.
86
Y. enterocolitica is associated with what clinical syndromes in addition to enterocolitis?
Transfusion-related sepsis, arthritis, intra-abdominal abscess, hepatitis, osteomyelitis
87
Why is Y. entercolitica infection associated with transfusion?
Blood contamination occurs due to asymptomic bacteremia at the time of blood donation; can proliferate in blood stored at 4 degrees Celsius after 2-3 weeks
88
What is serotyping?
Identifying the presence of different capsule, cell, and flagellar antigens

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