Typhoid bacteria (Salmonella typhi) colonies (white) being cultured on an agar growth medium (blue) in a petri dish. Typhoid is transmitted by infected food or water, often due to contamination by faeces. This bacterium causes an acute fever, abdominal pain and diarrhoea or constipation. Severe cases can lead to intestinal bleeding and death. Antibiotic treatments and vaccines are available. Grown on bromocresol purple lactose (or Drigalski) agar, a differential agar that contains lactose and an indicator dye to aid identification of bacteria.