Washington, July 27 - Researchers have stumbled on an organism that may unlock the key to what causes colic -- inconsolable crying in an otherwise healthy baby.

Colic is defined as unexplained and severe crying in an otherwise healthy infant three months old or younger, and lasts for more than three hours daily for at least three days a week.

'Right now, paediatric gastroenterologists can treat just about anything that comes through the door,' said J. Marc Rhoads, professor of paediatrics at The University of Texas Medical School-Houston (UTMS-H), who led the study.

But 'with colic, there is no evidence-based treatment we can offer. Colic can be a dangerous situation for a baby. The parent's frustration over the crying can lead to maternal frustration, post-partum depression and even thoughts of harming the baby,' Rhoads added.

The study pointed to an organism called Klebsiella, a normally occurring bacterium that can be found in the mouth, skin and intestines.