Probiotics are useful for :
Probiotics are defined as live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.
Bacterial colonization or infection of the intestine by pathogens such as Clostridium, Escherichia, Klebsiella, Salmonella, Shigella, Campylobacter, Pseudomonas, Streptococcus, Enterococcus, Staphylococcus aureus, and coagulase-negative staphylococcus increases the risk of necrotizing enterocolitis. 
Other potential uses of probiotics are

Managing lactose intolerance
Cholesterol-lowering
Improving immune function and preventing infections
Antibiotic-associated diarrhea
Improving mineral absorption
Irritable bowel syndrome and colitis
Prevention of colon cancer
Lowering blood pressure
Helicobacter pylori
Reducing inflammation
Prevents harmful bacterial growth under stress
Necrotizing enterocolitis
Breast milk jaundice
Hospital acquired pneumonia
Neonatal seizures