(Click HERE to return to Case Study Homepage)
Introduction
An emergency was reported at JFK airport as 8 passengers on board Flight 1038 from Lima, Peru, began to experience vomiting and diarrhea, in what appeared to be food/water poisoning.
The flight took off from Lima and made a technical stop in Miami, FL, USA, for two hours before arriving in New York City. The total trip took about 17 hours. The victims were rushed to a nearby hospital as soon as the pane landed.
You work as an epidemiologist for the NYC Department of Public Health. It is your job to determine what caused the outbreak and from where it came.
INSTRUCTIONS: We have developed a series of questions for you to answer as you go through this case study. Download and print a copy of the WORKSHEET.
Resources:
Methods:
Pathogen Library:
Symptoms
Right now, the only information you have is the symptoms, which include watery diarrhea with some vomiting; no fever. Based on these symptoms, and the information below, which common intestinal bacterial pathogens (see list below) do you now suspect? Which ones can you likely rule out?
Clinical Samples
You ask the clinical lab to streak rectal swabs of the patients onto selective media to try to isolate and identify the potential pathogen. You ask for some of the more common selective media for intestinal pathogens: Sorbital MacConkey and Hektoen Agar.
Review the media reference above. How do each of these media work? What do these results tell you?
|
Medium
|
E.coli | E.coli O157 | patient 1 | patient 2 | patient 3 | |
|
Sorbital MacConkey
Agar |
 |
 |
 |
 |
 |
|
| Salmonella |
Shigella
|
|||||
|
Hektoen Agar |
 |
 |
 |
 |
 |
There has to be more…
You are not convinced you have found the pathogen. As you ponder the situation, you come across this article on an outbreak in South America.
Convinced this could be the break you were looking for, you order one more selective medium.
What bacterium caused the outbreak in South America?
Search the internet to find out the name of the medium commonly used to detect this bacterium (and how it works), then interpret these results.
|
not inoculated
|
(+) control | patient 1 | patient 2 | patient 3 | |
 |
 |
 |
 |
 |
Confirming the Pathogen: ELISA
You are able to obtain stool samples from 6 of the patients on the plane suffering from diarrhea. You run 2 different ELISA assays on them: 1) E. coli entero-toxin and 2) Vibrio cholerae toxin. You include (+) and (-) controls to ensure that the ELISA’s are working properly. The ELISA results are shown below.
Review the background information on ELISA and review the results below. What do they tell you?
The Source
Now, you are very certain of what caused the outbreak. However, you need to know the source of the outbreak. You interview the patients, as well a number of other passengers (controls) on the plane who did not get sick, about potential exposure. An analysis of risks factors for patients and control passengers is shown below.
| Risk Factor | Patients (%) | Controls (%) |
| Visited Trujillo, Peru |
10/10 (100%) |
25/25 (100%) |
| Went to Trujillo fiesta |
8/10 (80%) |
18/25 (72%) |
| Drank unboiled water in Trujillo | 7/10 (70%) |
4/25 (16%) |
| Ate cabbage at fiesta |
1/10 (10%) | 4/25 (16%) |
| Ate bananas at fiesta | 4/10 (40%) |
17/25 (68%) |
| Ate cerviche (raw seafood) |
1/10 (10%) |
4/25 (16%) |
The Finishing Touches
To close this case, you do a ribotyping analysis of some isolates obtained from some patients and variety of sources. The ribotyping results are shown below.
Review the background information on Ribotyping and review the results below. What do they tell you?
Conclusion
Now it’s up to you!
So– you have all the data you need– it’s time to argue your case. What is the pathogen and what is the source for this outbreak?
Your answers should be thoughtful and well-organized, and it must incorporate the results you obtained in this case study. That is, use the information from your results and in the references to support your final conclusion.