17.4 CASE STUDY

Differentiate between disease caused by S. typhi and that caused by Shigella.

Route of Infection + Clinical Manifestation+ Duration+ Tissue Damage+ Complications+ Carriers 

Route of Infection:

  • S. typhi: After ingestion, the bacteria traverse through the intestine and get phagocytosed by macrophages. They then spread systemically to organs like the liver, spleen, and bone marrow.

  • Shigella: The infection is mainly localized to the intestine, specifically targeting the colonic mucosa.

Clinical Manifestation:

  • S. typhi: Initial symptoms are nonspecific and can include fever, headache, myalgias, malaise, and anorexia. As the disease progresses, high fever (stepladder pattern) becomes characteristic, potentially followed by complications like intestinal hemorrhage or perforation if untreated.

  • Shigella: This leads to acute bloody diarrhea (dysentery) with mucoid stools, abdominal cramps, and fever. The onset is often sudden.

Duration:

  • S. typhi: Typhoid fever has a more prolonged course and can last several weeks if untreated.

  • Shigella: The duration of Shigellosis is typically shorter, often resolving within a week, but severe infections can be life-threatening, especially in children.

Tissue Damage:

  • S. typhi: The damage isn't primarily due to direct invasion of the bacteria but rather due to the host's immune response.

  • Shigella: Causes direct damage to the intestinal wall, leading to tissue destruction and hemorrhagic colitis.

Complications:

  • S. typhi: Potential complications include intestinal perforation, hemorrhage, and dissemination leading to complications in distant organs.

  • Shigella: The most common complication is dehydration. Severe infections can lead to sepsis or hemolytic-uremic syndrome (HUS).

Carriers:

  • S. typhi: Chronic carriers (especially gallbladder carriers) are a significant concern as they serve as reservoirs for the bacteria and can infect others.

  • Shigella: Chronic carriage is less common.


Both diseases are primarily transmitted via the fecal-oral route and underscore the importance of good hygiene and sanitation in prevention.

Mind Map: Differentiate between disease caused by S. typhi and that caused by Shigella

Route of Infection

  • S. typhi

    • Ingestion

    • Traverse through the intestine

    • Phagocytosed by macrophages

    • Spread systemically to organs like liver, spleen, and bone marrow

  • Shigella

    • Localized to the intestine

    • Targets the colonic mucosa

Clinical Manifestation

  • S. typhi

    • Nonspecific initial symptoms

    • Fever, headache, myalgias, malaise, anorexia

    • High fever (stepladder pattern) as disease progresses

    • Complications: intestinal hemorrhage, perforation

  • Shigella

    • Acute bloody diarrhea (dysentery)

    • Mucoid stools, abdominal cramps, fever

    • Sudden onset

Duration

  • S. typhi

    • Prolonged course

    • Lasts several weeks if untreated

  • Shigella

    • Shorter duration

    • Resolves within a week

    • Severe infections can be life-threatening, especially in children

Tissue Damage

  • S. typhi

    • Damage due to host's immune response

  • Shigella

    • Direct damage to intestinal wall

    • Tissue destruction, hemorrhagic colitis

Complications

  • S. typhi

    • Intestinal perforation, hemorrhage

    • Dissemination leading to complications in distant organs

  • Shigella

    • Dehydration (most common)

    • Severe infections can lead to sepsis, hemolytic-uremic syndrome (HUS)

Carriers

  • S. typhi

    • Chronic carriers (especially gallbladder carriers)

    • Reservoirs for the bacteria, can infect others

  • Shigella

    • Less common chronic carriage

Both diseases are primarily transmitted via the fecal-oral route and emphasize the importance of good hygiene and sanitation in prevention.