The widespread usage of extended spectrum cephalosporins in the 1980s led to the emergence of β-lactamases capable of destroying them. Extended spectrum β-lactamases (ESBL) are the most common β-lactamases in some parts of the world and represent a pandemic of CTX-M ESBLs. Work examining the epidemiology and distribution of specific genotypes both in the UK and across the world particularly in China and India is presented. The faecal carriage by humans and dispersal into the environment is described. The environment and release of CTX-M producing Enterobacteriaceae into the environment following sewage treatment is reported and that arising from fish and poultry production. The work describes the isolation and characterization of the second most important CTX-M genotype (CTX-M-14) and the development of novel methods for the characterisation of genotypes. The publications were important in the recognition of the significance of CTX-M and drew attention to the characteristic genotype distribution around the world. The importance of faecal carriage as a dispersion mechanism and the association of specific genotypes with ethnic groups was a novel finding. The work also was the first to genotype ESBLs in India identifying that CTXM-15 was the only CTX-M genotype carried by one of the world's largest populations
