Biology: Enterobacteriaceae and Salmonella
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Questions and Answers

What is the optimal temperature for STEC growth?

  • 25 °C
  • 60 °C
  • 37 °C (correct)
  • 50 °C

Which E. coli is responsible for most foodborne infections resulting in death?

  • EIEC
  • STEC
  • ETEC
  • EHEC (correct)

What is the minimum pH level at which some STEC can grow?

  • 4.4 (correct)
  • 6.5
  • 5.5
  • 3.5

What is the minimum water activity (aw) at which some STEC can grow?

<p>0.95 (D)</p> Signup and view all the answers

What is the recommended internal temperature for cooking meats to prevent STEC infection?

<p>70 °C (A)</p> Signup and view all the answers

What is the characteristic of Salmonella that makes it a primary cause of food infections?

<p>Its high resistance to environmental conditions (C)</p> Signup and view all the answers

What is the typical duration of untreated Salmonella infection?

<p>4-7 days (A)</p> Signup and view all the answers

What is the primary cause of diarrhea in newborns and children under 2 years of age?

<p>EPEC (B)</p> Signup and view all the answers

What is the characteristic of Escherichia coli that causes dysentery-like bloody diarrhea?

<p>EIEC (B)</p> Signup and view all the answers

What is the minimum infectious dose of Salmonella reported in the literature?

<p>10^8-10^9 cfu/g (B)</p> Signup and view all the answers

Study Notes

E. coli

  • Infection is more common in hot summer months
  • EIEC produces heat-sensitive (LT) or heat-stable (ST) toxins
  • ETEC is associated with children's diarrhea and tourist diarrhea
  • EHEC is responsible for most foodborne infections resulting in death
  • STEC can cause severe foodborne disease and produces Shiga-toxins
  • STEC can grow in temperatures ranging from 7 °C to 50 °C, with an optimum temperature of 37 °C
  • Some STEC can grow in acidic foods, down to a pH of 4.4, and in foods with a minimum water activity (aw) of 0.95
  • High virulence and low Minimum Infective Dose (MID) of 10-100

Prevention

  • Cook meats thoroughly to at least 70 °C
  • Regular hand washing, particularly before food preparation or consumption, and after toilet contact
  • Wash fruits and vegetables carefully, especially if they are eaten raw

Enterobacteriaceae

  • Gram negative
  • Motile
  • Facultative anaerobes
  • Surface antigens: O, H, and Vi
  • More than 2500 strains

Salmonella

  • Widely distributed in the intestinal tract of domestic and wild animals
  • Can pass through the entire food chain from animal feed and primary production
  • High resistance to environmental conditions and long-term viability in food
  • One of the most important reasons for food infections

Salmonella Infections

  • Caused by fecal contamination by ill or asymptomatic chronic carriers
  • Fever is documented at presentation in more than 75% of cases
  • Gastroenteritis is the most common clinical presentation of non-typhoidal Salmonella infection
  • Illness usually lasts 4-7 days, and most people recover without treatment
  • Minimal infection dose is reported to be 10^8-10^9 cfu/g

E. coli Outbreak

  • 855 cases of HUS and 2,987 cases of acute gastroenteritis attributed to the outbreak
  • Death was reported for 35 (4.1%) of the patients identified with HUS and 18 (0.6%) of the patients with EHEC gastroenteritis
  • Total 53 deaths

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Description

Learn about the characteristics of Enterobacteriaceae, a family of Gram-negative bacteria, and Salmonella, a type of bacteria found in the intestinal tract of animals.

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