Digestive System Part II

Shigellosis - bacterial (digestive tract)

• Organism: Shigella sp.

• Diagnosis: Non-lactose fermenting on HE and Mac

  • No black centers on colonies

• Epidemiology: Very contagious (infectious dose = 10 cells)

Salmonellosis - bacterial (digestive tract)

• Organism: Salmonella enterica (gram - rod)

• Transmission: Eggs, meat, milk

• Diagnosis: Non-lactose fermenting on HE and Mac; serotyping

Typhoid fever - bacterial (digestive tract)

• Organism: Salmonella Typhi

• Transmission: Fecal-oral

• Diagnosis: Non-lactose fermenting on HE and Mac; colonies with black centers

• Epidemiology: Carriers can spread

• Symptoms: High fever, rash → septicemia

Enteropathogenic E. Coli (EPEC) - bacterial (digestive tract)

• Diagnosis: Lactose fermenters

  • Magenta on MacConkey

  • Gold/orange on Hektoen-Enteric

• Causes: Infantile diarrhea

Enteroinvasive E. coli (EIEC) - bacterial (digestive tract)

Acute, severe disease

• Contaminated food/water in developing countries

Enterohemorrhagic E. coli (EHEC) - Intoxication

• Caused by: strain O157:H7 (looks like normal flora)

• Diagnosis: Lactose fermenter

  • MacConkey sorbitol plate: O157:H7 is non-fermenter

• Virulence factor: Shiga toxin

Enterotoxogenic E. coli (ETEC) - Intoxication

Has acquired a toxin akin to cholera toxin

• Common cause of “traveler’s diarrhea”

• Sewage contaminated water

Campylobacteriosis - bacterial (digestive tract)

• Organism: Campylobacter jejuni

• Causes: Bacterial gastroenteritis in US

  • Guillan-Barre syndrome (autoimmune attack and temporary paralysis)

• Diagnosis: Campy blood agar plate (any growth = positive)

Yersiniosis - bacterial (digestive tract)

“Refigerator food poisoning” - grows at 4 C

• Organism: Yersinia enterocolitica

Gastric Ulcers - bacterial (digestive tract)

• Organism: Helicobacter pylori

• Virulence factor: Urease (breaks down urea and raises pH to withstand stomach acid)

Listeriosis - bacteria (digestive tract)

• Organism: Listeria monocytogenes

• Caused by: lunch meat, unpasturized dairy products

• Epidemiology: Fetuses (fetal meningitis)

Mumps - viral (digestive tract)

• Organism: Mumps virus

• Symptoms: Swelling of the cheek and jaw; can cause sterility in males

• Prevention: MMR vaccine

Rotavirus - viral (digestive tract)

Causes: viral gastroenteritis

Epidemiology: Children

Norovirus - viral (digestive tract)

Leading cause of adult gastroenteritis - very contagious

• Lifetime: 2 weeks

Hepatitis A - viral (digestive tract)

A = acute

• Transmission: ingestion

• Symptoms: spread to liver

• Prevention: vaccine

Hepatitis B - viral (digestive tract)

B = blood

• Asymptomatic in most *chronic carriers*

• Transmission: blood, semen, vaginal fluids

• Prevention: vaccine

• Treatment: post-exposure treatment

Hepatitis C - viral (digestive tract)

C = chronic

• Treatment: antivirals - can cure infection

  • If untreated → chronic hepatitis (20% get liver cirrhosis or cancer)

Hepatitis D - viral (digestive tract)

D = dud

• Higher mortality rate than HBV alone