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Bacteriology and Mycology > Salmonella > Flashcards

Salmonella Flashcards

1
Q

What are some of the characteristics of Salmonella?

A
  • Gram negative
  • Rods
  • Facultatively anaerobic
  • Motile with peritrichous flagella
  • NON-lactose fermenter
  • Zoonotic (Food and direct)
  • Habitat: GI tract of all animals
  • Very Hardy organism
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2
Q

Modes fo Infection

A
  1. Oral
  2. Transovarian transmission
  3. Flies: on body surface or in GI tract
  4. Foodbone infections in humans
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3
Q

What are the major Sources of Infection?

A
  1. Infected animals
  2. Asymptomatic carriers
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4
Q

What are the Virulence Factors of Salmonella?

A
  • Adhesins (pili)
  • Capsule (Vi)
  • Flagella
  • Endotoxin
  • Salmonella Pathogenicity Islands (SPI)
    • SPI-1 to SPI - 22
    • SPI-1 is responsible for invasion of intestinal epithelium
  • Siderophores:
    • enterobactin
  • Stress Proteins:
    • OM proteins produced in response to stress
  • Virulence Plasmids (SPV):
    • involved in systemic infections
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5
Q

What are Endotoxin (LPS)?

A
  • Mutants that lack LPS are less virulent
  • LPS causes vascular damage and thrombosis in the intestine
  • Responsible for systemic signs:
    • fever
    • diffuse intravascular coagulation (DIC)
    • circulatory collapse
    • shock
    • abortion
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6
Q

What are the predisposing factors for Salmonella infection

A
  • STRESS
    • ​Shipping
    • cold
    • overcrowding
    • surgery
    • antimicrobial therapy
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7
Q

What are the different types of Salmonella Infections

A
  1. Intestinal Infections
  2. Systemic infections
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8
Q

What is Salmonellla Enteritis?

A
  • Ileum most often affected
    • Speads to jejunum and colon
  1. Shortening and distortion of villi
  2. Degeneration of enterocytes
  3. Increased emptying of goblet cells (mucus production)
  4. Neutrophilic infiltration and migration into the lumen (neutrophilic shedding in feces)
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9
Q

What is Bovine Salmonellosis?

A
  • Common Serotypes:
    • Dublin and Typhimurium
  • Adults: Fever, depression, and severe diarrhea with blood and mucus
  • Cows: Abortion
  • Calves:
    • Usually between 3-6 weeks
    • Fever and Diarrhea
    • Death in 1-2 days
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10
Q

Pathogenesis of intestinal Infections

A
  1. Colonization of the intestine
    • adhere to enterocytes (pili or protien mediated)
    • Large numbers to initiate disease
    • Stress is critical factor
  2. Invasion and damage of the intestinal epithelium
    1. Enter the cells through the microvilli or the junction complexes
    2. multiply and attack adjacent cells
    3. enter lamina propria and engulfed by macrophages
      • Ability to survive and multiply inside phagocytes
  3. Simulation of fluid production and excretion
    • Net secretion of water, bicarbonate, and chloride into the lumen
    • Loss of epithelial cells results in impaired absorption
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11
Q

How do Systemic Salmonella infections happen?

A
  1. Start in the Intestinal Mucosa and Submucosa
  2. Enter th lymphatic vessels and go to the lymph nodes
  3. Enter the blood vessels
  4. Filtered by the RE system in the spleen and Liver
  • LPS is the key virulence factor
  • Most often observed with
    • S. Typhi humans
    • S. Cholerasuis pigs
    • S. Dublin cattle
    • S. Pullorum chickens
    • S. Gllinarum chickens
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12
Q

How does Salmonella cause abortion?

A

2 ways:

  • Fetus is culture positive
    1. Bacteremia
    2. Infection of the placenta and fetus
    3. Abortion
  • Fetus is culture negative
    1. Endotoxemia
    2. Release of PGF2a
    3. Lysis of Corpus luteum
    4. Abortion
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13
Q

What is Equine Salmonellosis?

A
  • Common Serotypes:
    • Typhimurium, Newport, Enteritidis, Heidelberg
  • Adult: Fever, depression, severe diarrhea with blood and mucus
  • Foals: Septicemia, high mortality
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14
Q

What is Swine Salmonellosis?

A
  • Common Serotypes:
    • Choleraesuis and Typhimurium
  • Acute Form:
    • Purplish areas, fever
    • Death in 1-3 days
  • Subacute Form: Diarrhea
  • Chronic Form: Enteritis with secondary invasion (necrosis)
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15
Q
  • Why is Salmonella a concern with Exotic Pets
A
  • 1.35 million cases of Salmonellosis occur yearly in theUS
  • 26,500 hospitalizations
  • 420 death
  • About 74,000 from reptiles and amphibians
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16
Q

How does serotype nomenclature work?

A
  1. Named for a particular disease
    1. Ex: S. Pullorum
  2. Named after the location
    1. Ex: S. Dublin
  • Capital P/D indicate serotype name not species name
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17
Q

What are the Antigenic Characteristics of Salmonella?

A
  • O-antigen: Somatic, LPS, Heat stable, designated 1, 2, 3, etc
  • H-antigen: Flagella, Protein, heat labile, designated by a, b, c, etc
  • Vi (Virulence or Capsular): Heat stable, designated 1, 2, 3, etc
    • only in S. typhi, S. hershfeldii, S. Dublin
18
Q

How is Salmonella classified?

A
  • Serogroups
    • Based on O antigen: 50 groups
      • Named A-X and 51-65
      • Majority are in goups B, C, D, E
  • Serotypes (Serovars)
    • Based on O and H
      • >2,500 serotypes
19
Q

How do you designate a Salmonella serotype?

A

Salmonella typhimurium 1, 4, [5], 12 : i : 1, 2

  • O = 1, 4, [5], 12
    • italics means phage conversion
    • [] present or absent
  • H = i
  • V = 1, 2
20
Q

What are some of the characteristics of Salmonella?

A
  • Gram negative
  • Rods
  • Facultatively anaerobic
  • Motile with peritrichous flagella
  • NON-lactose fermenter
  • Zoonotic (Food and direct)
  • Habitat: GI tract of all animals
  • Very Hardy organism
21
Q

What are the diseases caused by Salmonella?

A
  1. Enteritis
  2. Systemic Infections:
    1. septicemia
    2. Abortion
  3. Foodborne infections in humans
22
Q

What are the Modes of Infection of Salmonella?

A
  1. Oral
  2. Transovarian transmission
  3. Flies
  4. Foodborne infections in humans
23
Q

What is Ovine Salmonellosis?

A
  • Common Serotypes:
    • Typhimurium and Dublin
  • Enteritis
  • Septicemia
  • Abortion
24
Q

What is Canine and Feline Salmonellosis?

A
  • Not common
  • Racing greyhounds
    • from contaminated raw meat
25
Q

What is Avian Salmonellosis?

A
  • S. Pullorum: Pullorum or Bacillary white diarrhea
  • S. Gallinarum: Fowl typhoid
  • S. Typhimurium: enteritis, diarrhea, septicemia
  • S. Anatum: Keel disease in ducks
26
Q

What is Pullorum Disease and Fowl Typhoid?

A
  • Primarily in chickens and turkeys
  • Rare in commercial farms
  • Septicemic diseases
  • Transmitted through Transovarian transmission
27
Q

What is Salmonella Pullorum?

A
  • Highly fatal to young chicks
  • Adults are resistant carriers
  • Organisms excreted in feces
  • Modes of Transmission:
    • Transovarian, Ingestion, Inhalation
  • Lesion: Caseous areas in the gizzard/lungs
  • Diagnosis: Serology (agglutination)
28
Q

What is Salmonella Gallinarum?

A
  • “Fowl Typhoid”
  • Affects chicken and turkeys
  • Organisms excreted in feces
  • Modes of infection: Transovarian, Ingestion, Inhalation, Tick borne (Argas persicus)
  • Signs: Acute septicemic disease, weakness, hyperexcitability, paresis, diarrhea
  • Lesions: Meningitis, Multiple small necrotic areas in the liver and heart
29
Q

What is the National Eradication Program?

A
  • Pullorum and Fowl typhoid are mandatory reportable diseases
  • Outbreaks are placed under quarantine
  • Require periodic testing of breeding flocks
30
Q

How is Salmonellosis diagnosed?

A
  • Isolation:
    • Serotype identification is important only in chickens
  • Serology:
    • Blood or serum
31
Q

How is Immunity to Salmonella developed?

A
  • Both humoral and cell mediated
  • Secretory IgA may provide local immunity
  • Serum IgG against O- specific polysaccharide confers protection
32
Q

What is the treatment for Salmonellosis?

A
  • Antibiotics:
    • Aminoglycosides
    • Tetracyclines
  • Good to conduct susceptibility test
  • Fluid and electrolyte therapy
33
Q

Why conduct antibiotic susceptibility test?

A
  • Multiple antibiotic resistance is common
  • The wrong antibiotic may:
    • lead to systemic infection
    • Prolong fecal shedding
34
Q

Is there a vaccine for Salmonellosis?

A
  • For chickens/turkeys
  • Bacterins are not effective
  • Live attenuated
    • PO provides best protection
  • Vaccine consisting of mutants (Auxotrophic mutants)
  • SRP vaccine
35
Q

What are the control measures for Salmonellosis?

A
  • Reducing contamination of the environment
  • Eliminating source of infection
  • Minimizing stress
36
Q

What are the forms of Salmonellosis in Humans?

A
  1. Typhoid fever: S. Typhi
  2. Enteric fever:
    1. S. Paratyphi A
    2. S. Schotmulleri
    3. S. Hirshfeldii
  3. Gastroenteritis: foodborne, most common
37
Q

What is Gastroenteritis in Humans?

A
  • zoonotic
  • Often foodborne (meat, eggs, milk)
  • Mild, often self-limiting
  • Sever in childre and elderly
  • Symptoms:
    • Diarrhea, abdominal cramps, chills, fever, nausea/vomiting, headache, etc.
38
Q

How prevalent is Gastroenteritis in humans?

A
  • 1.35 million cases/year
    • 26,500 hospitalized
    • 420 deaths
  • 32 serotypes reported
    • Enteritidis, Typhemurium, Newport, Javiana, Heidelberg, Hadar, Agona
39
Q

What are the Multi-Drug Resistant (MDR) Salmonellas?

A
  • 2 serotypes:
    • Typhimurium DT 104
    • Newport
  • Major health concern
40
Q

S. Typhimurium DT 104

A
  • MDR: Amp, Cmp, Str, Sulfa, tet (ACSSuT) and now quinolones
  • Identified in UK in 1984
  • Outbreak in Nebraska in 1996
  • Steady increase in prevalence
  • Mortality 40% in cattle
  • 36% of people are hospitalized
  • Primarily associated with cattle
    • main source is ground beef
  • Control:
    • reduce infection in cattle
    • Reduce contamination risk during slaughter
41
Q

S. Newport

A
  • Recognized in 1999
  • MDR: B-lactams, Cmp, Strep, Tet
    • mediated by a plasmid
  • Outbreaks associated with dairy farms

Bacteriology and Mycology (35 decks)

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