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salmonella Flashcards

1
Q

characteristics of salmonella

A
  • gram neg
  • rod shaped
  • facultatively anaerobic
  • motile with peritrichous flagella
  • non lactose fermenter
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2
Q

is salmonella a zoonotic pathogen?

A

yes

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3
Q

where does salmonella naturally reside?

A

GI tract of all animals, including fish, and reptiles. Very hardy animals

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4
Q

what are salmonella’s antigenic characteristics?

A
  • O-antigen
  • H-antigen
  • Vi (virulence or capsular) - S. Dublin
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5
Q

which subspecies of salmonella is responsible for 99% of animal and human infections?

A

subspecies 1 (enterica)

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6
Q

what is the mode of infection of salmonella?

A
  1. oral transmission
  2. transovarian transmission (ovary to egg in poultry (yolk))
  3. flies
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7
Q

what is a predisposing factor for salmonella

A

STRESS

-shipping, cold, overcrowding, surgery, antimicrobial therapy, etc

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8
Q

what are two major sources of acquiring salmonella?

A

infected animals and asymptomatic carriers

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9
Q

what are the virulence factors of salmonella?

A
  • enterotoxins
  • cytotoxins
  • LPS
  • flagella
  • siderophore
  • heat shock proteins
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10
Q

what are the characteristics of the enterotoxins of salmonella?

A
  • cholera-like; (LT)
  • heat labile
  • induces fluid secretions
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11
Q

what are the characteristics of the cytotoxins of salmonella?

A
  • damage intestinal cells
  • three types:
    1. heat labile
    2. low MW protein
    3. cell associated hemolysin
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12
Q

what are the characteristics of the LPS of salmonella?

A
  • mutants that lack LPS are less virulent
  • cause vascular damage and thrombosis in the intestine
  • responsible for systemic signs: fever, DIC, circulatory collapse, and shock
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13
Q

what are the characteristics of the siderophores of salmonella?

A

-iron chelators

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14
Q

what are the characteristics of the HSPs of salmonella?

A
  • outer membrane proteins produces in response to stress

- essential for the survival in macrophages

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15
Q

what are the two types of salmonella infections?

A
  • intestinal infections

- systemic infections

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16
Q

what is the pathogenesis of intestinal infections?

A
  1. colonization of the intestine
  2. invasion and damage of the intestinal epithelium
  3. stimulation of fluid production and excretion
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17
Q

what is the colonization of the intestine

A
  1. adherence to the enterocytes (receptor mediated)
  2. larger numbers of organisms are required to initiate the disease
  3. stress is a critical factor
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18
Q

describe the invasion of the intestinal epithelium of salmonella

A
  1. enter the cells through the microvilli or via the junction complexes
  2. multiply and atack the adjacent cells
  3. enter lamina propria and are engulfed by macrophages
19
Q

what is a key feature to the salmonella’s invasiveness?

A

ability to survive and multiply inside phagocytes

20
Q

what is salmonella enteritis?

A

most often ileum is affected, later spreads to jejunum and colon

  • shortening and distortion of villi
  • degeneration of enterocytes
  • increased emptying of goblet cells (mucus productin)
  • neutrophilic infiltration and migration into the lumen (neutrophilic shedding in the feces)
21
Q

how does salmonella stimulate fluid production and excretion?

A
  1. net secretion of water, bicarbonate and chloride into the lumen
  2. loss of epithelial cells results in impaired absorption
    “diarrhea”
22
Q

what is the key virulence factor of salmonella?

23
Q

what does salonellosis cause?

A
  • enteritis
  • septicemia
  • abortion
  • food borne gastroenteritis in humans (diarrhea)
24
Q

what serotypes cause bovine salonellosis

A

S. Dublin and S. Typhinurium

25
what serotypes cause equine salmonellosis
- S. Typhimurium - S. Newport - S.Enteritidis - S. Heidelberg
26
what serotypes cause swine salmonellosis?
- S. Choleraesuis | - S. Typhimurium
27
what serotypes cause ovine salmonellosis?
- S. Abortusovis - S. Typhimurium - S. Dublin
28
what serotypes cause canine and feline salmonellosis?
- not very common | - racing greyhounds can get it from eating contaminated raw meat
29
what causes avian salmonellosis
- S. Pullorum - S. Gallinarum - S. Typhimurium (food poisoning)
30
what are pullorum disease and fowl typhoid?
- in chickens anturkeys - rare in commercial farms - septicemic diseases - transmitted through the egg "transovarian transmission"
31
what causes pullorum disease?
- salmonella pullorum - adult birds are resistant bu are carriers - excreted in feces - mode of infection: transovarian, ingestion, inhalation - lesions: caseous areas in the gizzard or lungs - diagnosis: serology (agglutination test)
32
what causes fowl typhoid?
- salmonella gallinarum - chickens and turkeys - excreted in feces - mode of infection: transovarian, ingestion, inhalation, or tick-borne
33
what are the signs of fowl typhoid?
- acute septicemic disease, weakness, hyperexcitability, paresis and diarrhea - lesions: meningitis, multiple small necrotic areas in the liver and heart
34
what are a few mandatory reportable diseases by the National Eradication Program?
Pullorum and Fowl typhoid
35
what causes avain salmonellosis?
- S. Typhimurium | - S. Anatum
36
what is the immunity toward salmonella?
- both humoral and cell mediated - secretory IgA may provide local immunity - serum IgG against O-specific polysaccharide confers prodection
37
what is the best protection against salmonella?
-live attenuated, orally administered vaccine
38
how do you treat salmonellosis
antibiotics are useful (must conduct sensitivity test) | -fluid and electrolyte therapy
39
why should you conduct a sensitivity test?
- multiple antibiotic resistance is common - the wrong antibiotic may: - lead to systemic infection - prolong fecal shedding
40
what are some control measures to prevent salmonellosis?
- reduce contamination of the environment - eliminate source of infection - minimizing stress
41
what are the three sources of salmonellosis in humans?
- typhoid fever - enteric fever - gastroenteritis (most common)
42
gastroenteritis characteristics
- zoonotic disease | - symptoms: diarrhea, abdominal cramps, chills, fever, nausea, vomiting, headache
43
what two serotypes are multi-drug resistant (MDR) Salmonella?
- Typhimurium DT 104 | - Newport

Bacteriology (17 decks)

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