Question

Discussion Topic

Regarding food safety,

a. Explain whether there is a greater risk for E. coli O157:H7 infection when consuming a hamburger compared to consuming a steak.

b. Also, discuss whether or not food poisoning can still occur after consuming a reheated pot of soup known to be contaminated with Staphylococcus aureus.

Minimum of 250 words please.

Answer 1

Question a

E coli O157:H7 is the most common serotype among the enterohaemorrhagic E coli. It is usually transmitted through contaminated food such as undercooked ground meat, spinach, lettuce etc. It manifests as hemorrhagic colitis characterised by abdominal pain, bloody diarrhoea. Another manifestation is hemolytic uremic syndrome. Infective dose is low(less than 100 bacilli)

Hamburgers are more harmful than steaks. Hamburgers are made from ground meat. This bacilli will be present on the surface of meat. When the meat is ground into fine pieces, the bacteria can reach the inner surfaces also. Every bit of the meat can get contaminated by the organism. So, improper cooking (at inadequate temperatures), will leave the meat unsafe to eat. Cooking to 160 degree Fahrenheit is needed to destroy the organism,so that each and every piece is adequately heated.

Steaks are not ground meat. Hence the bacilli will remain only on the surface. Heating will mostly destroy the bacteria present on the surface, even if adequate heat does not reach the interior.

Question b

Staphylococcal food poisoning is caused by the preformed enterotoxin which is already produced in the food, even before consumption. This toxin is expressed by nearly 50% of Staphylococcus aureus strains. Since the toxin is preformed, the incubation period is short. Manifestations occur in 1-6 hours. It manifests as nausea, vomiting, occasional diarrhoea, hypotension and dehydration. The toxin stimulates vagus nerve and vomiting centre in the brain. It also stimulate intestinal peristaltic activity. Serotype A is the most common type causing food poisoning. Most common food items involved are milk products, custards, potato salads or processed meat.

Reheating will not prevent food poisoning, because the toxin would have already been there in the food. This toxin is heat stable and can resist gastric juice also.