For the first time, medical experts have challenged the established view that the tuberculosis bacteria coughed up in sputum by infected individuals multiply rapidly. Experts at the Universities of Leicester and London have identified that the TB bug lays down body fat that may help it survive passing from one person to another. In the process, the bacteria increase their resistance to anti-TB drugs. The Leicester team discovered that, unlike TB bacteria growing in test tubes, many of the bugs in sputum are loaded with fat droplets. These "fat bacilli' were in an inert non-growing state, a condition in which they are more likely to survive the process of passing from one person to another. The discovery sheds light on "persister bacteria' in TB - a population believed to be the reason why TB patients have to be treated for at least six months.