MMIC PBL

Name: Kwan Siew Yan (outpatient)
Sex: Female
Age: 29
Complaints: Diarrhea
Diagnosis: Enterocolitis
Antibiotic treatment (if any): Nil
Specimen: Stool

Enterocolitis is the inflammation of the large and small intestines. [1] It is characterized by an invasion of the epithelial and subepithelial tissue of the small and large intestines. Strains that do not invade do not cause this disease. The organisms penetrate both through and between the mucosal cells into the lamina propria, resulting in inflammation and diarrhea. A polmorphonuclear leukocyte will limit the infection to other parts of the body. [2] Symptoms will include:
- diarrhea
- nausea
- vomiting
- fever
- abdominal bleeding
- rectal bleeding
- sluggishness [1]

Possible Organisms Present [2]:
1) Salmonella enteritidis
Characteristics
- facultative anaerobes
- gram-negative rods
- do not ferment lactose
- produce H2S
- motile

Habitat and Transmission
- found in enteric tract of humans and animals
- transmitted mainly by fecal-oral route and foods prepared by chronic carriers

Pathogenesis
- invade the mucosa of the small and large intestines
- infectious dose is at least 10*5 organisms, much greater than infectious dose of Shigella

2) Shigella species
Characteristics
- facultative gram-negative rods
- do not produce H2S
- non-lactose fermenting
- non-motile compared to Salmonella

Habitat and Transmission
- human colon only; human disease
- no animal reservoir for Shigella
- transmitted by the fecal-oral route
- principal factors in transmission include fingers, flies, food and feces

Pathogenesis
- invade the mucosa of the ileum and colon but do not penetrate further; hence sepsis is rare
- most effective pathogens among enteric bacteria as infectious dose is much lower (1-10 organisms) than that of Salmonella

3) Campylobacter jejuni
Characteristics
- curved, gram-negative rods that appear either comma or S-shaped
- motile with a single polar flagellum
- microaerophilic (5% O2 with 10% CO2)
- grow well at 42℃

Habitat and Transmission
- human and animal feces
- transmitted by fecal-oral route
- Food and water contamination with animal feces is the major source of human infection. (e.g. poultry, meat and unpasteurized milk)

Pathogenesis
- invade mucosa of colon but do not penetrate; hence sepsis is rare

4) Staphylococcus aureus
Characteristics
- gram-positive cocci in clusters
- coagulase-positive and catalase-positive

Transmission
- via the hands

Pathogenesis
- produce enterotoxin in foods

5) Clostridium difficile
Characteristics
- anaerobic
- gram-positive
- spore-forming rods

Habitat and Transmission
- human colon and transmitted by fecal-oral route

Pathogenesis
- antibiotics suppress normal flora of colon, allowing them to overgrow and produce large amounts of exotoxins

6) Bacillus cereus
Characteristics
- aerobic
- gram-negative
- spore-forming rod

Habitat and Transmission
- found in grains such as rice (e.g. re-heated rice)

Pathogenesis
- Two enterotoxins are produced

7) Enteroinvasive Escherichia coli (EIEC)
Characteristics
- Facultative gram-negative rods
- Ferment lactose

Transmission
- Fecal-oral route
- Food-borne route

Pathogenesis
- closely resemble Shigella in their pathogenic mechanisms
- penetrate and multiply within epithelial cells of the colon causing widespread cell destruction
- EIEC are invasive organisms which are same as Shigella but they do not produce LT or ST toxin and, unlike Shigella, they do not produce the shiga toxin

References

1) http://www.wrongdiagnosis.com/ >enterocolitis

2) Levinson, W. (2006). Review Of Medical Microbiology and Immunology. (9th ed.). US: The McGraw-Hill Company.

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