1. Case Study Pathogenic Bacteriology 2009
Maria Navarrete
Luu, Helen
Chiu, Allen

2. Case Summary
The patient was am 8-year-old male with a 2-day history of diarrhea. He presented with worsening diarrhea (14 movements that day) which had become bloody. He also complained of pain upon defecation and had vomited once. He had attended a cookout previously and claimed that his mother had made him eat a hamburger that was “pink inside” even though he” he did not like it.”

3. Culture of stool specimen on MacConkey-sorbitol

4. Key Information Pointing to Diagnosis
Age
- 8-year old
Symptoms
2-day diarrhea
Bloody diarrhea
Vomit
Dehydration
Pain upon defecation
History
Consumption of undercooked meat
Physical examination
White blood count of 13, 100/μl with 9,700 neutrophils per μl
Abundant polymorphonuclear cells in a methylene blue stain of feces
He was treated with trimethoprim-sulfamethoxazole and intravenous fluid therapy for dehydration. His condition improved and was discharged 24 hours later.

5. Escherichia coli serotype O157:H7
Diagnosis
Enterohemorrhagic
Escherichia coli serotype O157:H7
Infection

6. Classification Enterobacteriaceae Escherichia coli serotype O157:H7
Enterohemorragic (EHEC)
Gram –
Rod
Motile
Sorbitol negative

8. Diseases and Pathogenesis of Disease Caused by Pathogen E. coli O157:H7
Hemorrhagic diarrhea
Colitis
Hemolytic-uremic syndrome (HUS)
Pathogenesis
E. coli O157:H7 has O, H, antigens.
E. coli O157:H7 produces two toxins: verotoxin I and verotoxin II.
Verotoxin I is a phage-encoded cytotoxin identical to the shiga toxin.
E. coli O157:H7 attaches via pili to the intestinal mucosa and liberates the shiga-like toxin.

9. Diagnosis/Isolation/Identification/ of E. coli O157:H7
Stool culture on MacConkey agar containing sorbitol (SMAC)
Appear colorless with heavy growth
Serotyping with E. coli O157:H7 antiserum
4-methylum-belliferyl β-D-glucoronide (MUG) biochemical test
E. coli O157:H7 rarely produces the enzyme β-D-glucoronidase; therefore, if enzyme is present a fluorescent product is formed.
ELISA or latex agglutination to detect O157 antigen
Latex test to detect H7 antigen

10. Therapy, Prevention and Prognosis of Patient Infected with E
Therapy, Prevention and Prognosis of Patient Infected with E. coli 0157:H7
Most people recover without specific treatment in five to 10 days. Antibiotics should not be used for the treatment of E. coli 0157:H7 infection due that some antibiotics may increase the risk of complications.
To prevent E. coli 0157:H7 infections, do not eat undercooked hamburger or other ground beef products. Drink only pasteurized milk, juice or cider. Wash fruits and vegetables thoroughly, especially those that will not be cooked.
Children under five years and the elderly should avoid eating alfalfa sprouts. Immunocompromised patients are also susceptible to E. coli 0157:H7.
People who are infected with E. coli 0157:H7, especially children, should wash their hands carefully with soap after using the toilet to reduce the risk of spreading the disease.

11. Prevalence and potential link between E
Prevalence and potential link between E. coli O157:H7 isolated from drinking water, meat and vegetables and stools of diarrhoeic confirmed and non-confirmed HIV⁄AIDS patients in the Amathole District – South Africa
Abong’o B.O et al, 2008, Journal of Applied Microbiology, vol:105. p-p. 424–431.
Stool collection from confirmed and non-confirmed patients from a referral hospital in The Amathole district in Africa were tested for E. coli O157:H7. Water samples and meat samples collected from rural communities in The Amathole district where these patients reside were collected and tested for the presence of E. coli O157:H7.
Researchers found that 74 out of 131 stool samples of HIV/AIDS patients contained E. coli O157:H7. They also found that 46 out of 180 water samples contained and 64 out of 180 meat and meat products samples contained E. coli O157:H7.
Researchers also fount that the prevalence of E. coli O157:H7 was correlated to the poor living and unhygienic of these patients.
Researchers urge for prompt monitoring of water and food products in underserved communities to control E. coli O157:H7 infections.
This article was important for the prevention of E. coli O157:H7 in HIV patients living in underserved communities.

12. Take Home Message
E. coli 0157:H7 causes hemorrhagic diarrhea, colitis, and HUS.
E. coli 0157:H7 illness produces watery diarrhea, bloody diarrhea, abdominal cramps, and a low grade fever or no fever.
E. coli 0157:H7 may be potentially fatal for young children and the elderly.
E. coli 0157:H7 may be identified by stool culture using SMAC, serotyping, and detection of shiga-like toxins.
Antibiotics should not be used for the treatment of E. coli 0157:H7 infection due to higher production of shiga-like toxin.
Cook all meat thoroughly, wash all vegetables, and do not drink unpasteurized dairy products and juices.
Transmission of E. coli 0157:H7 is through the consumption of undercooked processed meat, unpasteurized dairy products and juices, and bean sprouts.
E. coli 0157:H7 is an important potential human pathogen.

13. References
Abong’o, B. O., and M. N.B. Momba. "Prevalence and potential link
between E. coli O157:H7 isolated from drinking water, meat and
vegetables and stools of diarrhoeic confirmed and non-confirmed HIV⁄AIDS patients in the Amathole District – South Africa." Journal
of Applied Microbiology 105 (Jan.-Feb. 2008): 424–431.
Centers for Disease Control and Prevention. "Escherichia coli General
Information ." Centers for Disease Control and Prevention. 27 Mar
Department of Health and Human Services. 11 Mar. 2009
<
Mahon, Connie R., Donald C. Lehman, and George Manuselis.
Diagnostic Microbiology. 3rd ed. St. Louis: Saunders, 2007.
McQueen, Nancy. "Enterobacteriaceae." Unpublished notes. California
State University Los Angeles. Biology and Microbiology
Department. Winter 2009.
Rickman, Mike. "A Colorful Editorial Cartoon Accompanying a Column About an E. coli
Outbreak." Cartoon. Mike Rickman. 11 Mar < index.shtml>.