Thank you for the query. As per the history, your mother is 85 yrs old, with a severe eye infection for which she required oral antibiotics, and presently suffering from diarrhoea. I n all probabilities, the diarrhoea is an antibiotic induced one (very common with high end antibiotics). In this case, it is advisable to maintain her fluid and electrolyte balance, she requires plenty of oral fluid intake and oral rehydration salt/solution. Probiotic drugs are advisable (like lactobacillus), and she can continue having curd, as this is helpful. There are certain drugs which are specifically taken for this condition (like metronidazole and oral vancomycin), however, these should be taken only after consulting your physician. If symptoms persist or worsen certain infection parameters need to be checked like total white blood cell count and stool for C.difficile toxin. Hope this helps you.