The bacterium group B streptococcus, or GBS is the leading cause of meningitis and infection in newborn babies in the UK. This life threatening infection occurs in 1 in 1000 babies and one of five babies affected will die. Many pregnant women without symptoms have GBS if they are tested, and are presumed to be at risk of infecting their babies. These researchers will check how common the infection is in pregnant women and develop ways of preventing the infection spreading to their babies. The aim is to find the difference between bacteria that are likely to cause an infection and those that are not, so antibiotics can be given to mothers when required. This work will also be important in guiding vaccine development.