Case C: On a Friday afternoon, 65 individuals attended a farewell party. The age

Question

Case C: On a Friday afternoon, 65 individuals attended a farewell party. The ages of the people attending ranged from 4 to 78 years of age. The event was held in a nearby city park and food was provided by a local catering company. Food was brought to the party by the caterers at approximately 12:30 p.m. Within 20-24 hours after the food had been served, several people began to experience vomiting and diarrhea with moderate to severe abdominal cramps, headache and muscle aches. Some of the elderly patients experienced some typical symptoms of dehydration, such as thirst and dryness of the mucus membranes. Fecal cultures from the patients grew the same microorganism with the following characteristics: Gram-negative bacillus Glucose fermentation: Lactose fermentation H2S production Positive Negative Positive 1. How did a TSI tube test of this microorganism look like? (1pt) 2. What was the period of incubation for these pathogenic bacteria? (0.5 pt) 3. What was the most likely means of transmission of this pathogen? (0.Spt

Explanation / Answer

1. Answer: The TSI tube looks has alkaline slant with acidic bottom, with gas formation (H2S). The bottom of the tube willl be yellow due to glucose fermentation and slant will be red.

Explanation: TSI tube contains Triple Sugar Iron agar with 0.1% glucose, 1% lactose or sucrose, Ferrous sulphate to serve as indicator of H2S production, Phenol red to indicate acidification and peptone as nitrogen source. Since, the given bacterium is a glucose fermenter and glucose is rich in the bottom of the tube, it turns yellow due to acidification while slant being rich in lactose stays red in color. As H2S is produced, the slant will appear red.

From this TSI tube result, the microbe can be concluded as Salmonella or Proteus.

2. The incubation period for Gastroenteritis type of Proteus is 3-20 hours while Salmonella food poisoning has 6-72 hours of incubation period. Both of them match the given food poisoning but as there is dehydration and dryness of mucus memebranes the Salmonella food poisoning can be ruled out as it is having less chances. So, the most likely food poisoning in this case would be from Preoteus

3. Most likely means of transmission for this disease is food served in the party which might be contaminate with the pathogens:

Salmonella food poisoning: Rodent contaminated food, Poultry, beef, eggs may contain Salmonella bacteria which may be presented in the party and led to the food poisoning due to improper cooking by the catering service

Proteus food poisoning: Unclean food, improper hygeine, improper cooking, unclean utensils for food serving may led to the contamination of the food served in the party resulting in food poisoning.

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