“While there are a number of variables to consider, the simple answer is yes. Theoretically, when used cutlery is in contact with your leftovers, oral bacteria are transferred to the food. If not stored properly or for a long time, these could result in food poisoning.
Opportunistic bugs wait for the perfect environment in which to thrive, but the growth rate of bacteria depends on a number of factors such as food type, bacterial content of the food prior to storage, food acidity levels, fridge temperature and length of storage. Higher bacterial levels (such as in undercooked chicken) and longer storage times increase the risk of food poisoning. To be safe, cook food thoroughly, store leftovers properly, and serve food with clean utensils.”