Extended-spectrum beta-lactamases in non-typhoidal Salmonella spp. isolated in the UK are now a reality: why the late arrival?

In February 2004, we reported the first recognition of the presence of an extended-spectrum beta-lactamase (ESBL) in non-typhoidal Salmonella spp. in the UK; the beta-lactamase was TEM-52. Six months later, an SHV-derived ESBL (SHV-12) was detected in a salmonella strain isolated in York and 6 months after that we have just identified CTX-M-type beta-lactamases in Scottish isolates of Salmonella enterica subsp. enterica serovar Typhimurium and Salmonella Virchow (unpublished results). A very recent retrospective study of UK isolates suggests that they may have been in the population for some years but have gone undetected. Even so, compared with reports of ESBLs in Salmonella spp. elsewhere, these results are suggestive of a delayed emergence of the ESBL phenotype in non-typhoidal Salmonella spp. in the UK. Should the British congratulate themselves on warding off the emergence of these important resistance mechanisms in Salmonella spp., or is the sudden revelation of three of the major ESBL types a cause for concern?